Sample records for varian computers
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Automated segmentation and dose-volume analysis with DICOMautomaton
NASA Astrophysics Data System (ADS)
Clark, H.; Thomas, S.; Moiseenko, V.; Lee, R.; Gill, B.; Duzenli, C.; Wu, J.
2014-03-01
Purpose: Exploration of historical data for regional organ dose sensitivity is limited by the effort needed to (sub-)segment large numbers of contours. A system has been developed which can rapidly perform autonomous contour sub-segmentation and generic dose-volume computations, substantially reducing the effort required for exploratory analyses. Methods: A contour-centric approach is taken which enables lossless, reversible segmentation and dramatically reduces computation time compared with voxel-centric approaches. Segmentation can be specified on a per-contour, per-organ, or per-patient basis, and can be performed along either an embedded plane or in terms of the contour's bounds (e.g., split organ into fractional-volume/dose pieces along any 3D unit vector). More complex segmentation techniques are available. Anonymized data from 60 head-and-neck cancer patients were used to compare dose-volume computations with Varian's EclipseTM (Varian Medical Systems, Inc.). Results: Mean doses and Dose-volume-histograms computed agree strongly with Varian's EclipseTM. Contours which have been segmented can be injected back into patient data permanently and in a Digital Imaging and Communication in Medicine (DICOM)-conforming manner. Lossless segmentation persists across such injection, and remains fully reversible. Conclusions: DICOMautomaton allows researchers to rapidly, accurately, and autonomously segment large amounts of data into intricate structures suitable for analyses of regional organ dose sensitivity.
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Digital overlaying of the Universal Transverse Mercator Grid with LANDSAT-data derived products
NASA Technical Reports Server (NTRS)
Pendleton, T. W.
1976-01-01
Software has been written in FORTRAN IV for a Varian 73 computer which reformats LANDSAT-data-derived surface classifications and pictorial representations into a digital array which corresponds to the Universal Transverse Mercator Grid.
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Kim, Sangroh; Yoshizumi, Terry; Toncheva, Greta; Yoo, Sua; Yin, Fang-Fang; Frush, Donald
2010-05-01
To address the lack of accurate dose estimation method in cone beam computed tomography (CBCT), we performed point dose metal oxide semiconductor field-effect transistor (MOSFET) measurements and Monte Carlo (MC) simulations. A Varian On-Board Imager (OBI) was employed to measure point doses in the polymethyl methacrylate (PMMA) CT phantoms with MOSFETs for standard and low dose modes. A MC model of the OBI x-ray tube was developed using BEAMnrc/EGSnrc MC system and validated by the half value layer, x-ray spectrum and lateral and depth dose profiles. We compared the weighted computed tomography dose index (CTDIw) between MOSFET measurements and MC simulations. The CTDIw was found to be 8.39 cGy for the head scan and 4.58 cGy for the body scan from the MOSFET measurements in standard dose mode, and 1.89 cGy for the head and 1.11 cGy for the body in low dose mode, respectively. The CTDIw from MC compared well to the MOSFET measurements within 5% differences. In conclusion, a MC model for Varian CBCT has been established and this approach may be easily extended from the CBCT geometry to multi-detector CT geometry.
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Constantin, Dragoş E; Fahrig, Rebecca; Keall, Paul J
2011-07-01
Using magnetic resonance imaging (MRI) for real-time guidance during radiotherapy is an active area of research and development. One aspect of the problem is the influence of the MRI scanner, modeled here as an external magnetic field, on the medical linear accelerator (linac) components. The present work characterizes the behavior of two medical linac electron guns with external magnetic fields for in-line and perpendicular orientations of the linac with respect to the MRI scanner. Two electron guns, Litton L-2087 and Varian VTC6364, are considered as representative models for this study. Emphasis was placed on the in-line design approach in which case the MRI scanner and the linac axes of symmetry coincide and assumes no magnetic shielding of the linac. For the in-line case, the magnetic field from a 0.5 T open MRI (GE Signa SP) magnet with a 60 cm gap between its poles was computed and used in full three dimensional (3D) space charge simulations, whereas for the perpendicular case the magnetic field was constant. For the in-line configuration, it is shown that the electron beam is not deflected from the axis of symmetry of the gun and the primary beam current does not vanish even at very high values of the magnetic field, e.g., 0.16 T. As the field strength increases, the primary beam current has an initial plateau of constant value after which its value decreases to a minimum corresponding to a field strength of approximately 0.06 T. After the minimum is reached, the current starts to increase slowly. For the case when the beam current computation is performed at the beam waist position the initial plateau ends at 0.016 T for Litton L-2087 and at 0.012 T for Varian VTC6364. The minimum value of the primary beam current is 27.5% of the initial value for Litton L-2087 and 22.9% of the initial value for Varian VTC6364. The minimum current is reached at 0.06 and 0.062 T for Litton L-2087 and Varian VTC6364, respectively. At 0.16 T the beam current increases to 40.2 and 31.4% from the original value of the current for Litton L-2087 and Varian VTC6364, respectively. In contrast, for the case when the electron gun is perpendicular to the magnetic field, the electron beam is deflected from the axis of symmetry even at small values of the magnetic field. As the strength of the magnetic field increases, so does the beam deflection, leading to a sharp decrease of the primary beam current which vanishes at about 0.007 T for Litton L-2087 and at 0.006 T for Varian VTC6364, respectively. At zero external field, the beam rms emittance computed at beam waist is 1.54 and 1.29n-mm-mrad for Litton L-2087 and Varian VTC6364, respectively. For the inline configuration, there are two particular values of the external field where the beam rms emittance reaches a minimum. Litton L-2087 rms emittance reaches a minimum of 0.72n and 2.01 n-mm-mrad at 0.026 and 0.132 T, respectively. Varian VTC6364 rms emittance reaches a minimum of 0.34n and 0.35n-mm-mrad at 0.028 and 0.14 T, respectively. Beam radius dependence on the external field is shown for the in-line configuration for both electron guns. 3D space charge simulation of two electron guns, Litton L-2087 and Varian VTC6364, were performed for in-line and perpendicular external magnetic fields. A consistent behavior of Pierce guns in external magnetic fields was proven. For the in-line configuration, the primary beam current does not vanish but a large reduction of beam current (up to 77.1%) is observed at higher field strengths; the beam directionality remains unchanged. It was shown that for a perpendicular configuration the current vanishes due to beam bending under the action of the Lorentz force. For in-line configuration it was determined that the rms beam emittance reaches two minima for relatively high values of the external magnetic field.
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Constantin, Dragoş E.; Fahrig, Rebecca; Keall, Paul J.
2011-01-01
Purpose: Using magnetic resonance imaging (MRI) for real-time guidance during radiotherapy is an active area of research and development. One aspect of the problem is the influence of the MRI scanner, modeled here as an external magnetic field, on the medical linear accelerator (linac) components. The present work characterizes the behavior of two medical linac electron guns with external magnetic fields for in-line and perpendicular orientations of the linac with respect to the MRI scanner. Methods: Two electron guns, Litton L-2087 and Varian VTC6364, are considered as representative models for this study. Emphasis was placed on the in-line design approach in which case the MRI scanner and the linac axes of symmetry coincide and assumes no magnetic shielding of the linac. For the in-line case, the magnetic field from a 0.5 T open MRI (GE Signa SP) magnet with a 60 cm gap between its poles was computed and used in full three dimensional (3D) space charge simulations, whereas for the perpendicular case the magnetic field was constant. Results: For the in-line configuration, it is shown that the electron beam is not deflected from the axis of symmetry of the gun and the primary beam current does not vanish even at very high values of the magnetic field, e.g., 0.16 T. As the field strength increases, the primary beam current has an initial plateau of constant value after which its value decreases to a minimum corresponding to a field strength of approximately 0.06 T. After the minimum is reached, the current starts to increase slowly. For the case when the beam current computation is performed at the beam waist position the initial plateau ends at 0.016 T for Litton L-2087 and at 0.012 T for Varian VTC6364. The minimum value of the primary beam current is 27.5% of the initial value for Litton L-2087 and 22.9% of the initial value for Varian VTC6364. The minimum current is reached at 0.06 and 0.062 T for Litton L-2087 and Varian VTC6364, respectively. At 0.16 T the beam current increases to 40.2 and 31.4% from the original value of the current for Litton L-2087 and Varian VTC6364, respectively. In contrast, for the case when the electron gun is perpendicular to the magnetic field, the electron beam is deflected from the axis of symmetry even at small values of the magnetic field. As the strength of the magnetic field increases, so does the beam deflection, leading to a sharp decrease of the primary beam current which vanishes at about 0.007 T for Litton L-2087 and at 0.006 T for Varian VTC6364, respectively. At zero external field, the beam rms emittance computed at beam waist is 1.54 and 1.29π-mm-mrad for Litton L-2087 and Varian VTC6364, respectively. For the in-line configuration, there are two particular values of the external field where the beam rms emittance reaches a minimum. Litton L-2087 rms emittance reaches a minimum of 0.72π and 2.01π-mm-mrad at 0.026 and 0.132 T, respectively. Varian VTC6364 rms emittance reaches a minimum of 0.34π and 0.35π-mm-mrad at 0.028 and 0.14 T, respectively. Beam radius dependence on the external field is shown for the in-line configuration for both electron guns. Conclusions: 3D space charge simulation of two electron guns, Litton L-2087 and Varian VTC6364, were performed for in-line and perpendicular external magnetic fields. A consistent behavior of Pierce guns in external magnetic fields was proven. For the in-line configuration, the primary beam current does not vanish but a large reduction of beam current (up to 77.1%) is observed at higher field strengths; the beam directionality remains unchanged. It was shown that for a perpendicular configuration the current vanishes due to beam bending under the action of the Lorentz force. For in-line configuration it was determined that the rms beam emittance reaches two minima for relatively high values of the external magnetic field. PMID:21859019
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Constantin, Dragos E.; Fahrig, Rebecca; Keall, Paul J.
Purpose: Using magnetic resonance imaging (MRI) for real-time guidance during radiotherapy is an active area of research and development. One aspect of the problem is the influence of the MRI scanner, modeled here as an external magnetic field, on the medical linear accelerator (linac) components. The present work characterizes the behavior of two medical linac electron guns with external magnetic fields for in-line and perpendicular orientations of the linac with respect to the MRI scanner. Methods: Two electron guns, Litton L-2087 and Varian VTC6364, are considered as representative models for this study. Emphasis was placed on the in-line design approachmore » in which case the MRI scanner and the linac axes of symmetry coincide and assumes no magnetic shielding of the linac. For the in-line case, the magnetic field from a 0.5 T open MRI (GE Signa SP) magnet with a 60 cm gap between its poles was computed and used in full three dimensional (3D) space charge simulations, whereas for the perpendicular case the magnetic field was constant. Results: For the in-line configuration, it is shown that the electron beam is not deflected from the axis of symmetry of the gun and the primary beam current does not vanish even at very high values of the magnetic field, e.g., 0.16 T. As the field strength increases, the primary beam current has an initial plateau of constant value after which its value decreases to a minimum corresponding to a field strength of approximately 0.06 T. After the minimum is reached, the current starts to increase slowly. For the case when the beam current computation is performed at the beam waist position the initial plateau ends at 0.016 T for Litton L-2087 and at 0.012 T for Varian VTC6364. The minimum value of the primary beam current is 27.5% of the initial value for Litton L-2087 and 22.9% of the initial value for Varian VTC6364. The minimum current is reached at 0.06 and 0.062 T for Litton L-2087 and Varian VTC6364, respectively. At 0.16 T the beam current increases to 40.2 and 31.4% from the original value of the current for Litton L-2087 and Varian VTC6364, respectively. In contrast, for the case when the electron gun is perpendicular to the magnetic field, the electron beam is deflected from the axis of symmetry even at small values of the magnetic field. As the strength of the magnetic field increases, so does the beam deflection, leading to a sharp decrease of the primary beam current which vanishes at about 0.007 T for Litton L-2087 and at 0.006 T for Varian VTC6364, respectively. At zero external field, the beam rms emittance computed at beam waist is 1.54 and 1.29{pi}-mm-mrad for Litton L-2087 and Varian VTC6364, respectively. For the in-line configuration, there are two particular values of the external field where the beam rms emittance reaches a minimum. Litton L-2087 rms emittance reaches a minimum of 0.72{pi} and 2.01{pi}-mm-mrad at 0.026 and 0.132 T, respectively. Varian VTC6364 rms emittance reaches a minimum of 0.34{pi} and 0.35{pi}-mm-mrad at 0.028 and 0.14 T, respectively. Beam radius dependence on the external field is shown for the in-line configuration for both electron guns. Conclusions: 3D space charge simulation of two electron guns, Litton L-2087 and Varian VTC6364, were performed for in-line and perpendicular external magnetic fields. A consistent behavior of Pierce guns in external magnetic fields was proven. For the in-line configuration, the primary beam current does not vanish but a large reduction of beam current (up to 77.1%) is observed at higher field strengths; the beam directionality remains unchanged. It was shown that for a perpendicular configuration the current vanishes due to beam bending under the action of the Lorentz force. For in-line configuration it was determined that the rms beam emittance reaches two minima for relatively high values of the external magnetic field.« less
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NASA Astrophysics Data System (ADS)
Hodges, M.; Barzilov, A.; Chen, Y.; Lowe, D.
2016-10-01
The bremsstrahlung photon flux from the UNLV particle accelerator (Varian M6 model) was determined using MCNP5 code for 3 MeV and 6 MeV incident electrons. Human biological equivalent dose rates due to accelerator operation were evaluated using the photon flux with the flux-to-dose conversion factors. Dose rates were computed for the accelerator facility for M6 linac use under different operating conditions. The results showed that the use of collimators and linac internal shielding significantly reduced the dose rates throughout the facility. It was shown that the walls of the facility, in addition to the earthen berm enveloping the building, provide equivalent shielding to reduce dose rates outside to below the 2 mrem/h limit.
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Deshpande, Sudesh; Dhote, Deepak; Thakur, Kalpna; Pawar, Amol; Kumar, Rajesh; Kumar, Munish; Kulkarni, M. S.; Sharma, S. D.; Kannan, V.
2016-01-01
The objective of this work was to measure patient eye lens dose for different cone-beam computed tomography (CBCT) acquisition protocols of Varian's On-Board Imaging (OBI) system using optically stimulated luminescence dosimeter (OSLD) and to study the variation in eye lens dose with patient geometry and distance of isocenter to the eye lens. During the experimental measurements, OSLD was placed on the patient between the eyebrows of both eyes in line of nose during CBCT image acquisition to measure eye lens doses. The eye lens dose measurements were carried out for three different cone-beam acquisition protocols (standard dose head, low-dose head [LDH], and high-quality head [HQH]) of Varian OBI. Measured doses were correlated with patient geometry and distance between isocenter and eye lens. Measured eye lens doses for standard head and HQH protocols were in the range of 1.8–3.2 mGy and 4.5–9.9 mGy, respectively. However, the measured eye lens dose for the LDH protocol was in the range of 0.3–0.7 mGy. The measured data indicate that eye lens dose to patient depends on the selected imaging protocol. It was also observed that eye lens dose does not depend on patient geometry but strongly depends on distance between eye lens and treatment field isocenter. However, undoubted advantages of imaging system should not be counterbalanced by inappropriate selection of imaging protocol, especially for very intense imaging protocol. PMID:27651564
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[Porting Radiotherapy Software of Varian to Cloud Platform].
Zou, Lian; Zhang, Weisha; Liu, Xiangxiang; Xie, Zhao; Xie, Yaoqin
2017-09-30
To develop a low-cost private cloud platform of radiotherapy software. First, a private cloud platform which was based on OpenStack and the virtual GPU hardware was builded. Then on the private cloud platform, all the Varian radiotherapy software modules were installed to the virtual machine, and the corresponding function configuration was completed. Finally the software on the cloud was able to be accessed by virtual desktop client. The function test results of the cloud workstation show that a cloud workstation is equivalent to an isolated physical workstation, and any clients on the LAN can use the cloud workstation smoothly. The cloud platform transplantation in this study is economical and practical. The project not only improves the utilization rates of radiotherapy software, but also makes it possible that the cloud computing technology can expand its applications to the field of radiation oncology.
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Digital overlaying of the universal transverse Mercator grid with LANDSAT data derived products
NASA Technical Reports Server (NTRS)
Graham, M. H.
1977-01-01
Picture elements of data from the LANDSAT multispectral scanner are correlated with the universal tranverse Mercator grid. In the procedure, a series of computer modules was used to make approximations of universal transverse Mercator grid locations for all picture elements from the grid locations of a limited number of known control points and to provide display and digital storage of the data. The software has been written in FORTRAN 4 language for a Varian 70-series computer.
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Dosimetric quality control of Eclipse treatment planning system using pelvic digital test object
NASA Astrophysics Data System (ADS)
Benhdech, Yassine; Beaumont, Stéphane; Guédon, Jeanpierre; Crespin, Sylvain
2011-03-01
Last year, we demonstrated the feasibility of a new method to perform dosimetric quality control of Treatment Planning Systems in radiotherapy, this method is based on Monte-Carlo simulations and uses anatomical Digital Test Objects (DTOs). The pelvic DTO was used in order to assess this new method on an ECLIPSE VARIAN Treatment Planning System. Large dose variations were observed particularly in air and bone equivalent material. In this current work, we discuss the results of the previous paper and provide an explanation for observed dose differences, the VARIAN Eclipse (Anisotropic Analytical) algorithm was investigated. Monte Carlo simulations (MC) were performed with a PENELOPE code version 2003. To increase efficiency of MC simulations, we have used our parallelized version based on the standard MPI (Message Passing Interface). The parallel code has been run on a 32- processor SGI cluster. The study was carried out using pelvic DTOs and was performed for low- and high-energy photon beams (6 and 18MV) on 2100CD VARIAN linear accelerator. A square field (10x10 cm2) was used. Assuming the MC data as reference, χ index analyze was carried out. For this study, a distance to agreement (DTA) was set to 7mm while the dose difference was set to 5% as recommended in the TRS-430 and TG-53 (on the beam axis in 3-D inhomogeneities). When using Monte Carlo PENELOPE, the absorbed dose is computed to the medium, however the TPS computes dose to water. We have used the method described by Siebers et al. based on Bragg-Gray cavity theory to convert MC simulated dose to medium to dose to water. Results show a strong consistency between ECLIPSE and MC calculations on the beam axis.
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Hill, Malcolm S; Hill, April L
2002-02-01
The goal of the research presented here was to examine phenotypic plasticity exhibited by three morphotypes of the common Caribbean sponge Anthosigmella varians (Duchassaing & Michelotti). We were interested in examining the biotic (and, to a lesser extent, abiotic) factors responsible for branch production in this species. We also tested the hypothesis that the skeleton may serve an antipredator function in this sponge, focusing on vertebrate fish predators (i.e., angelfish) in this work. In transplant and caging experiments, unprotected forma varians replicates were immediately consumed by angelfish, while caged replicates persisted on the reef for several months. These findings support the hypothesis that predators (and not wave energy) restrict forma varians to lagoonal habitats. Branch production was not observed in A. varians forma incrustans when sponges were protected from predators or placed in predator-free, low-wave-energy environments. It is not clear from our work whether forma incrustans is capable of producing branches (i.e., whether branch production is a plastic trait in this morph). Additional field experiments demonstrated that A. varians forma varians increased spicule concentrations, compared to uninjured sponges, in response to artificial predation events, and A. varians forma rigida reduced spicule concentrations, compared to uncaged controls, when protected from predators. These findings indicate that spicule concentration is a plastic morphological trait that can be induced by damage, and that A. varians may be able to reduce spicule concentrations when environmental conditions change (e.g., in the absence of predators). The potential significance of inducible defenses and structural anti-predator defenses in sponges is discussed in relation to recent work on sponge chemical defenses.
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NASA Astrophysics Data System (ADS)
Freeman, Ray; Morris, Gareth A.
2015-01-01
This Perspective offers a personal view of the story of Varian NMR, a courageous initiative that began in the 1950s but came to an abrupt end some 60 years later. Without doubt, Varian leaves behind a priceless legacy, particularly in the field of structural chemistry. The highlights are set out in four main sections, named after the four seasons, but not necessarily in strict chronology. How did the accepted business practices influence the evolution, growth, and eventual demise of this exciting venture? How well did management handle an unconventional group of young scientific entrepreneurs? What does it all mean for the future of magnetic resonance? The subject can be viewed on two different levels, the Varian story itself, and the larger picture - the Silicon Valley phenomenon as a whole, with Varian considered as an interesting microcosm.
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Molecular Phylogeny, Laboratory Rearing, and Karyotype of the Bombycid Moth, Trilocha varians
Daimon, Takaaki; Yago, Masaya; Hsu, Yu-Feng; Fujii, Tsuguru; Nakajima, Yumiko; Kokusho, Ryuhei; Abe, Hiroaki; Katsuma, Susumu; Shimada, Toru
2012-01-01
This study describes the molecular phylogeny, laboratory rearing, and karyotype of a bombycid moth, Trilocha varians (F. Walker) (Lepidoptera: Bombycidae), which feeds on leaves of Ficus spp. (Rosales: Moraceae). The larvae of this species were collected in Taipei city, Taiwan, and the Ryukyu Archipelago (Ishigaki and Okinawa Islands, Japan). Molecular phylogenetic analyses revealed that T. varians belongs to the subfamily Bombycinae, thus showing a close relationship to the domesticated silkworm Bombyx mori (L.), a lepidopteran model insect. A laboratory method was developed for rearing T. varians and the time required for development from the embryo to adult was determined. From oviposition to adult emergence, the developmental zero was 10.47 °C and total effective temperature was 531.2 day—degrees, i.e., approximately 30 days for one generation when reared at 28 °C. The haploid of T. varians consisted of n = 26 chromosomes. In highly polyploid somatic nuclei, females showed a large heterochromatin body, indicating that the sex chromosome system in T. varians is WZ/ZZ (female/male). The results of the present study should facilitate the utilization of T. varians as a reference species for B. mori, thereby leading to a greater understanding of the ecology and evolution of bombycid moths. PMID:22963522
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SU-E-T-100: Designing a QA Tool for Enhance Dynamic Wedges Based On Dynalog Files
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yousuf, A; Hussain, A
2014-06-01
Purpose: A robust quality assurance (QA) program for computer controlled enhanced dynamic wedge (EDW) has been designed and tested. Calculations to perform such QA test is based upon the EDW dynamic log files generated during dose delivery. Methods: Varian record and verify system generates dynamic log (dynalog) files during dynamic dose delivery. The system generated dynalog files contain information such as date and time of treatment, energy, monitor units, wedge orientation, and type of treatment. It also contains the expected calculated segmented treatment tables (STT) and the actual delivered STT for the treatment delivery as a verification record. These filesmore » can be used to assess the integrity and precision of the treatment plan delivery. The plans were delivered with a 6 MV beam from a Varian linear accelerator. For available EDW angles (10°, 15°, 20°, 25°, 30°, 45°, and 60°) Varian STT values were used to manually calculate monitor units for each segment. It can also be used to calculate the EDW factors. Independent verification of fractional MUs per segment was performed against those generated from dynalog files. The EDW factors used to calculate MUs in TPS were dosimetrically verified in solid water phantom with semiflex chamber on central axis. Results: EDW factors were generated from the STT provided by Varian and verified against practical measurements. The measurements were in agreement of the order of 1 % to the calculated EDW data. Variation between the MUs per segment obtained from dynalog files and those manually calculated was found to be less than 2%. Conclusion: An efficient and easy tool to perform routine QA procedure of EDW is suggested. The method can be easily implemented in any institution without a need for expensive QA equipment. An error of the order of ≥2% can be easily detected.« less
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Process yield improvements with process control terminal for varian serial ion implanters
NASA Astrophysics Data System (ADS)
Higashi, Harry; Soni, Ameeta; Martinez, Larry; Week, Ken
Implant processes in a modern wafer production fab are extremely complex. There can be several types of misprocessing, i.e. wrong dose or species, double implants and missed implants. Process Control Terminals (PCT) for Varian 350Ds installed at Intel fabs were found to substantially reduce the number of misprocessing steps. This paper describes those misprocessing steps and their subsequent reduction with use of PCTs. Reliable and simple process control with serial process ion implanters has been in increasing demand. A well designed process control terminal greatly increases device yield by monitoring all pertinent implanter functions and enabling process engineering personnel to set up process recipes for simple and accurate system operation. By programming user-selectable interlocks, implant errors are reduced and those that occur are logged for further analysis and prevention. A process control terminal should also be compatible with office personal computers for greater flexibility in system use and data analysis. The impact from the capability of a process control terminal is increased productivity, ergo higher device yield.
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TU-AB-BRC-05: Creation of a Monte Carlo TrueBeam Model by Reproducing Varian Phase Space Data
DOE Office of Scientific and Technical Information (OSTI.GOV)
O’Grady, K; Davis, S; Seuntjens, J
Purpose: To create a Varian TrueBeam 6 MV FFF Monte Carlo model using BEAMnrc/EGSnrc that accurately reproduces the Varian representative dataset, followed by tuning the model’s source parameters to accurately reproduce in-house measurements. Methods: A BEAMnrc TrueBeam model for 6 MV FFF has been created by modifying a validated 6 MV Varian CL21EX model. Geometric dimensions and materials were adjusted in a trial and error approach to match the fluence and spectra of TrueBeam phase spaces output by the Varian VirtuaLinac. Once the model’s phase space matched Varian’s counterpart using the default source parameters, it was validated to match 10more » × 10 cm{sup 2} Varian representative data obtained with the IBA CC13. The source parameters were then tuned to match in-house 5 × 5 cm{sup 2} PTW microDiamond measurements. All dose to water simulations included detector models to include the effects of volume averaging and the non-water equivalence of the chamber materials, allowing for more accurate source parameter selection. Results: The Varian phase space spectra and fluence were matched with excellent agreement. The in-house model’s PDD agreement with CC13 TrueBeam representative data was within 0.9% local percent difference beyond the first 3 mm. Profile agreement at 10 cm depth was within 0.9% local percent difference and 1.3 mm distance-to-agreement in the central axis and penumbra regions, respectively. Once the source parameters were tuned, PDD agreement with microDiamond measurements was within 0.9% local percent difference beyond 2 mm. The microDiamond profile agreement at 10 cm depth was within 0.6% local percent difference and 0.4 mm distance-to-agreement in the central axis and penumbra regions, respectively. Conclusion: An accurate in-house Monte Carlo model of the Varian TrueBeam was achieved independently of the Varian phase space solution and was tuned to in-house measurements. KO acknowledges partial support by the CREATE Medical Physics Research Training Network grant of the Natural Sciences and Engineering Research Council (Grant number: 432290).« less
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NASA Astrophysics Data System (ADS)
Kennedy, William James
2013-12-01
Kennedy, W.J. 2013. On variation in Schloenbachia varians (J. Sowerby, 1817) from the Lower Cenomanian of western Kazakhstan Acta Geologica Polonica, 63
(4), 443-468. Warszawa. An assemblage of 94 specimens of Schloenbachia varians (J. Sowerby, 1817) from the Lower Cenomanian Sharpeiceras schlueteri Subzone of the Mantelliceras mantelli Zone of the Besakty section in the Mangyshlak Mountains of western Kazakhstan includes 26 complete adults that range from to 59-174 mm in diameter. No size-related dimorphism was detected in the assemblage, which shows wide, continuous intraspecific variation. This is described in terms of five formae; from robust to gracile these are: ventriosa, varians sensu stricto, subtuberculata , intermedia, and subplana. The ratio of robust (ventriosa + varians sensu stricto) to gracile (subtuberculata + intermedia + subplana) individuals is 34% to 66%. The reference specimens of the formae and their synonyms are described and illustrated, and related to the Besakty material. The modification of adult body chamber ornament of all formae is documented, and Jakeiceras Cooper and Owen, 2011 is shown to be based on an adult of a passage form between forma subtuberculata and forma intermedia. The differences between Lower Cenomanian S. varians, lower Middle Cenomanian S. coupei (Brongniart, 1822), and upper Middle and lower Upper Cenomanian S. lymensis Spath, 1926b are described and illustrated. -
Breves, André; Széchy, Maria Teresa M DE; Lavrado, Helena P; Junqueira, Andrea O R
2017-01-01
The reef-building vermetid Petaloconchus varians occurs in the western Atlantic Ocean, from the Caribbean Sea to the southern coast of Brazil. The present study evaluated the abundance of P. varians on intertidal rocky shores in Ilha Grande Bay (Rio de Janeiro State), and characterized their reefs, describing the species density, besides the weight and the belt width of the reefs. Petaloconchus varians reefs were recorded at 25 sites, with rocky shores exposed to different wave action (very sheltered, sheltered, semi-exposed and exposed) and slopes (10° to 46°). Clusters of individuals constructed large reefs along the middle intertidal zone, creating a wide belt (38 cm to 2 m). The density of P. varians and the weight of the reefs ranged from 620 to 2,559 ind.100 cm-2 and from 100 to 1,500 g.100 cm-2, respectively. Considering that the species was last reported from the area in the mid-20th century, the present study suggests that P. varians reefs are becoming dominant in the intertidal zone of rocky shores in Ilha Grande Bay. This is a contribution to knowledge of this ecosystem in Ilha Grande Bay, in view of local or global ecological changes.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Bai, W; Fan, X; Qiu, R
2014-06-01
Purpose: To compare and analyze the characteristics of static intensity-modulated radiotherapy (IMRT) plans designed on Elekta and Varian Linac in different esophageal cancer(EC), exploring advantages and disadvantages of different vendor Linac, thus can be better serve for clinical. Methods: Twenty-four patients with EC were selected, including 6 cases located in the cervical, upper, middle and the lower thorax, respectively. Two IMRT plans were generated with the Oncentra planning system: in Elekta and Varian Linac, prescription dose of 60Gy in 30 fractions to the PTV. We examined the dose-volume histogram parameters of PTV and the organs at risk (OAR) such asmore » lungs, spinal cord and heart, and additional Monitor units(MU), treatment time, Homogeneity index(HI), Conformity index(CI) and Gamma index comparisons were performed. Results: All plans resulted in abundant dose coverage of PTV for EC of different locations. The doses to PTV, HI and OAR in Elekta plans were not statistically different in comparison with Varian plans, with the following exceptions: in cervical, upper and lower thoracic EC the PTV's CI, and in middle thorax EC PTV's D2, D50, V105 and PTV-average were better in Elekta plans than in Varian plans. In the cervical, upper and the middle thorax EC, treatment time were significantly decreased in Varian plans as against Elekta plans, while in the lower thoracic EC treatment time were no striking difference. MUs and gamma index were similar between the two Linac plans. Conclusion: For the the middle thorax EC Varian plans is better than Elekta plans, not only in treatment time but in the PTV dose; while for the lower thorax EC Elekta plans is the first choice for better CI; for the other part of the EC usually Elekta plans can increase the CI, while Varian plans can reduce treatment time, can be selected according to the actual situation of the patient treatment.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Pursley, J; Gueorguiev, G; Prichard, H
Purpose: To demonstrate the commissioning of constant dose rate volumetric modulated arc therapy (VMAT) in the Raystation treatment planning system for a Varian Clinac iX with Exact couch. Methods: Constant dose rate (CDR) VMAT is an option in the Raystation treatment planning system, enabling VMAT delivery on Varian linacs without a RapidArc upgrade. Raystation 4.7 was used to commission CDR-VMAT for a Varian Clinac iX. Raystation arc model parameters were selected to match machine deliverability characteristics. A Varian Exact couch model was added to Raystation 4.7 and commissioned for use in VMAT optimization. CDR-VMAT commissioning checks were performed on themore » linac, including patient-specific QA measurements for 10 test patients using both the ArcCHECK from Sun Nuclear Corporation and COMPASS from IBA Dosimetry. Multi-criteria optimization (MCO) in Raystation was used for CDR-VMAT planning. Results: Raystation 4.7 generated clinically acceptable and deliverable CDR-VMAT plans for the Varian Clinac. VMAT plans were optimized including a model of the Exact couch with both rails in the out positions. CDR-VMAT plans generated with MCO in Raystation were dosimetrically comparable to Raystation MCO-generated IMRT plans. Patient-specific QA measurements with the ArcCHECK on the couch showed good agreement with the treatment planning system prediction. Patient-specific, structure-specific, multi-statistical parameter 3D QA measurements with gantry-mounted COMPASS also showed good agreement. Conclusion: Constant dose rate VMAT was successfully modeled in Raystation 4.7 for a Varian Clinac iX, and Raystation’s multicriteria optimization generated constant dose rate VMAT plans which were deliverable and dosimetrically comparable to IMRT plans.« less
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SU-E-T-164: Clinical Implementation of ASi EPID Panels for QA of IMRT/VMAT Plans.
Hosier, K; Wu, C; Beck, K; Radevic, M; Asche, D; Bareng, J; Kroner, A; Lehmann, J; Logsdon, M; Dutton, S; Rosenthal, S
2012-06-01
To investigate various issues for clinical implementation of aSi EPID panels for IMRT/VMAT QA. Six linacs are used in our clinic for EPID-based plan QA; two Varian Truebeams, two Varian 2100 series, two Elekta Infiniti series. Multiple corrections must be accounted for in the calibration of each panel for dosimetric use. Varian aSi panels are calibrated with standard dark field, flood field, and 40×40 diagonal profile for beam profile correction. Additional corrections to account for off-axis and support arm backscatter are needed for larger field sizes. Since Elekta iViewGT system does not export gantry angle with images, a third-party inclinometer must be physically mounted to back of linac gantry and synchronized with data acquisition via iViewGT PC clock. A T/2 offset correctly correlates image and gantry angle for arc plans due to iView image time stamp at the end of data acquisition for each image. For both Varian and Elekta panels, a 5 MU 10×10 calibration field is used to account for the nonlinear MU to dose response at higher energies. Acquired EPID images are deconvolved via a high pass filter in Fourier space and resultant fluence maps are used to reconstruct a 3D dose 'delivered' to patient using DosimetryCheck. Results are compared to patient 3D dose computed by TPS using a 3D-gamma analysis. 120 IMRT and 100 VMAT cases are reported. Two 3D gamma quantities (Gamma(V10) and Gamma(PTV)) are proposed for evaluating QA results. The Gamma(PTV) is sensitive to MLC offsets while Gamma(V10) is sensitive to gantry rotations. When a 3mm/3% criteria and 90% or higher 3D gamma pass rate is used, all IMRT and 90% of VMAT QA pass QA. After appropriate calibration of aSi panels and setup of image acquisition systems, EPID based 3D dose reconstruction method is found clinically feasible. © 2012 American Association of Physicists in Medicine.
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SU-E-T-505: Inter-Comparison of Clinical Plans Created On Truebeam with Trilogy and Clinac
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sharma, M; Wu, Y; Kim, S
2015-06-15
Purpose The purpose of this study is to investigate the dosimetric differences in clinical treatment plans when machine parameters are switched from Varian Truebeam to older Varian models and vice-versa. This is used to determine the clinically-safe limits to directly transfer patients from Truebeam to Trilogy or Clinac. Methods Thirty-two patients with cancer of different treatment sites such as lung, head-and-neck, prostate and breast were studied. The clinically approved IMRT, VMAT or 3D conformal treatment plans were delivered either on Truebeam or Clinac/Trilogy. Keeping the monitor units, fraction size and other machine parameters the same, the plans were recomputed onmore » a different Varian linear accelerator (e.g., Truebeam plans were recomputed on Trilogy and vice-versa). The plans comparison was done using the target D98 and normal organ D2, D10, D20, D30, D50 and D70 dose metrics. Results The perfraction dose-difference in the PTV-D98 for all 32 patients varied from 0.01 to −0.06 Gy with median being −0.04 Gy. For a 2Gy/fraction treatment course, this would be maximum PTV-D98 dose-difference of 6 cGy/fraction or 30 cGy/5fractions. For organs-at-risks the maximum per-fraction dosedifference in D2, D5, D10, D20, D30, D50 and D70 between Truebeam and Trilogy/Clinac plans varied from 0.06 to −0.07 Gy with median being with — 0.02 Gy. The 3D-CRT plans had relatively lower dose-difference in comparison to IMRT and VMAT plans. The dose computed on Truebeam was systematically lower than the dose computed on Trilogy/ Clinac. Conclusions for conventional fractionation schedules, assuming the maximum uncertainty of <2%, it is clinically safe to switch the treatment machine for 5 fractions. For hypo-fractionated treatments with higher dose per-fraction, plans may need to be revisited before switching the linear accelerator from Truebeam to Clinac/Trilogy or vice-versa.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, T; Lin, H; Xu, X
Purpose: (1) To perform phase space (PS) based source modeling for Tomotherapy and Varian TrueBeam 6 MV Linacs, (2) to examine the accuracy and performance of the ARCHER Monte Carlo code on a heterogeneous computing platform with Many Integrated Core coprocessors (MIC, aka Xeon Phi) and GPUs, and (3) to explore the software micro-optimization methods. Methods: The patient-specific source of Tomotherapy and Varian TrueBeam Linacs was modeled using the PS approach. For the helical Tomotherapy case, the PS data were calculated in our previous study (Su et al. 2014 41(7) Medical Physics). For the single-view Varian TrueBeam case, we analyticallymore » derived them from the raw patient-independent PS data in IAEA’s database, partial geometry information of the jaw and MLC as well as the fluence map. The phantom was generated from DICOM images. The Monte Carlo simulation was performed by ARCHER-MIC and GPU codes, which were benchmarked against a modified parallel DPM code. Software micro-optimization was systematically conducted, and was focused on SIMD vectorization of tight for-loops and data prefetch, with the ultimate goal of increasing 512-bit register utilization and reducing memory access latency. Results: Dose calculation was performed for two clinical cases, a Tomotherapy-based prostate cancer treatment and a TrueBeam-based left breast treatment. ARCHER was verified against the DPM code. The statistical uncertainty of the dose to the PTV was less than 1%. Using double-precision, the total wall time of the multithreaded CPU code on a X5650 CPU was 339 seconds for the Tomotherapy case and 131 seconds for the TrueBeam, while on 3 5110P MICs it was reduced to 79 and 59 seconds, respectively. The single-precision GPU code on a K40 GPU took 45 seconds for the Tomotherapy dose calculation. Conclusion: We have extended ARCHER, the MIC and GPU-based Monte Carlo dose engine to Tomotherapy and Truebeam dose calculations.« less
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Kocuria varians infection associated with brain abscess: a case report.
Tsai, Cheng-Yu; Su, Shou-hsin; Cheng, Yu-Hsin; Chou, Yu-lin; Tsai, Tai-Hsin; Lieu, Ann-Shung
2010-04-27
Kocuria, established by Stackebrandt et al., previously was classified into Micrococcus. Only two species, K. rosea and K. kristinae are reported to be associated as pathogenic and found with catheter-related bacteremia and acute cholecystitis. We herein report the first case of brain abscess caused by Kocuria varians, a gram-positive microorganism, in a 52-year-old man. Hematogenous spread is the probable pathogenesis. This report presents a case of Kocuria varians brain abscess successfully treated with surgical excision combined with antimicrobial therapy. In addition, Vitek 2 system has been used to identify and differentiate between coagulase-negative staphylococcus.
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NASA Astrophysics Data System (ADS)
Daimon, Takaaki; Fujii, Takeshi; Yago, Masaya; Hsu, Yu-Feng; Nakajima, Yumiko; Fujii, Tsuguru; Katsuma, Susumu; Ishikawa, Yukio; Shimada, Toru
2012-03-01
Analysis of female sex pheromone components and subsequent field trap experiments demonstrated that the bombycid moth Trilocha varians uses a mixture of ( E, Z)-10,12-hexadecadienal (bombykal) and ( E,Z)-10,12-hexadecadienyl acetate (bombykyl acetate) as a sex pheromone. Both of these components are derivatives of ( E,Z)-10,12-hexadecadienol (bombykol), the sex pheromone of the domesticated silkmoth Bombyx mori. This finding prompted us to compare the antennal and behavioral responses of T. varians and B. mori to bombykol, bombykal, and bombykyl acetate in detail. The antennae of T. varians males responded to bombykal and bombykyl acetate but not to bombykol, and males were attracted only when lures contained both bombykal and bombykyl acetate. In contrast, the antennae of B. mori males responded to all the three components. Behavioral analysis showed that B. mori males responded to neither bombykal nor bombykyl acetate. Meanwhile, the wing fluttering response of B. mori males to bombykol was strongly inhibited by bombykal and bombykyl acetate, thereby indicating that bombykal and bombykyl acetate act as behavioral antagonists for B. mori males. T. varians would serve as a reference species for B. mori in future investigations into the molecular mechanisms underlying the evolution of sex pheromone communication systems in bombycid moths.
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Catching errors with patient-specific pretreatment machine log file analysis.
Rangaraj, Dharanipathy; Zhu, Mingyao; Yang, Deshan; Palaniswaamy, Geethpriya; Yaddanapudi, Sridhar; Wooten, Omar H; Brame, Scott; Mutic, Sasa
2013-01-01
A robust, efficient, and reliable quality assurance (QA) process is highly desired for modern external beam radiation therapy treatments. Here, we report the results of a semiautomatic, pretreatment, patient-specific QA process based on dynamic machine log file analysis clinically implemented for intensity modulated radiation therapy (IMRT) treatments delivered by high energy linear accelerators (Varian 2100/2300 EX, Trilogy, iX-D, Varian Medical Systems Inc, Palo Alto, CA). The multileaf collimator machine (MLC) log files are called Dynalog by Varian. Using an in-house developed computer program called "Dynalog QA," we automatically compare the beam delivery parameters in the log files that are generated during pretreatment point dose verification measurements, with the treatment plan to determine any discrepancies in IMRT deliveries. Fluence maps are constructed and compared between the delivered and planned beams. Since clinical introduction in June 2009, 912 machine log file analyses QA were performed by the end of 2010. Among these, 14 errors causing dosimetric deviation were detected and required further investigation and intervention. These errors were the result of human operating mistakes, flawed treatment planning, and data modification during plan file transfer. Minor errors were also reported in 174 other log file analyses, some of which stemmed from false positives and unreliable results; the origins of these are discussed herein. It has been demonstrated that the machine log file analysis is a robust, efficient, and reliable QA process capable of detecting errors originating from human mistakes, flawed planning, and data transfer problems. The possibility of detecting these errors is low using point and planar dosimetric measurements. Copyright © 2013 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.
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Pérez-Aguilar, Daniel Alberto; Soares, Marianne Araújo; Passos, Luis Clepf; Martínez, Ana Mabel; Pineda, Samuel; Carvalho, Geraldo Andrade
2018-06-19
The mirid Engytatus varians (Distant) is a promising biological control agent of the tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), one of the most destructive pests of tomato (Solanum lycopersicum L.). The effects of five insecticides commonly used on tomato crops in Brazil were evaluated on E. varians in laboratory and semifield conditions. Glass Petri dish with residues of chlorfenapyr, thiamethoxam, and abamectin caused ˃90% mortality in both stages of the predator 72 h post-treatment, except imidacloprid that caused 78% of nymphs mortality. Teflubenzuron caused 24 and 66% mortality on adults and nymphs, respectively. The offspring of females derived from treated nymphs with teflubenzuron was significantly lower than the control but not when females were treated as adults. Longevity of males derived from nymphs treated with teflubenzuron was significantly reduced, but no effects were observed on females. When males and females were treated as adults with teflubenzuron there were no effects on their longevity. In the greenhouse-aged tomato plants, the 2 h-old residues of thiamethoxam, chlorfenapyr, and abamectin caused more than 70% of mortality of third instar of E. varians at 72 h post-treatment, 12 day-old residues of all three compounds caused a mortality lower than 30%. These data suggest that teflubenzuron can be associated with releases of E. varians adults, while the use of other evaluated pesticides should be avoided in this situation. Although, the low persistence of these products indicate that their spraying and later releases of E. varians adults on tomato crops are a possible strategy to control T. absoluta.
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Time-resolved EPR spectroscopy in a Unix environment.
Lacoff, N M; Franke, J E; Warden, J T
1990-02-01
A computer-aided time-resolved electron paramagnetic resonance (EPR) spectrometer implemented under version 2.9 BSD Unix was developed by interfacing a Varian E-9 EPR spectrometer and a Biomation 805 waveform recorder to a PDP-11/23A minicomputer having MINC A/D and D/A capabilities. Special problems with real-time data acquisition in a multiuser, multitasking Unix environment, addressing of computer main memory for the control of hardware devices, and limitation of computer main memory were resolved, and their solutions are presented. The time-resolved EPR system and the data acquisition and analysis programs, written entirely in C, are described. Furthermore, the benefits of utilizing the Unix operating system and the C language are discussed, and system performance is illustrated with time-resolved EPR spectra of the reaction center cation in photosystem 1 of green plant photosynthesis.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Njeh, C
2015-06-15
Purpose: Dose inhomogeneity in treatment planning can be compensated using physical wedges. Enhanced dynamic wedges (EDW) were introduced by Varian to overcome some of the short comings of physical wedges. The objectives of this study were to measure EDW output factors for 6 MV and 20 MV photon energies for a Varian 2300CD. Secondly to review the literature in terms of published enhanced dynamic wedge output factors (EDWOF) for different Varian models and thereby adding credence to the case of the validity of reference databases. Methods: The enhanced dynamic wedge output factors were measured for the Varian 2300CD for bothmore » 6 MV and 20 MV photon energies. Twelve papers with published EDWOF for different Varian Linac models were found in the literature. Results: The EDWOF for 6 MV varied from 0.980 for a 5×5 cm 10 degree wedge to 0.424 for 20×20 cm 60 degree wedge. Similarly for 20 MV, the EDWOF varied from 0.986 for 5×5 cm 10 degree wedge to 0.529 for 20×20 cm 60 degree wedge. EDWOF are highly dependent on field size. Comparing our results with the published mean, we found an excellent agreement for 6 MV EDWOF with the percentage differences ranging from 0.01% to 0.57% with a mean of 0.03%. The coefficient of variation of published EDWOF ranged from 0.17% to 0.85% and 0.1% to 0.9% for the for 6 MV and 18MV photon energies respectively. This paper provides the first published EDWOF for 20 MV photon energy. In addition, we have provided the first compendium of EDWOFs for different Varian linac models. Conclusion: The consistency of EDWOF across models and institution provide further support that, a standard data set of basic photon and electron dosimetry could be established, as a guide for future commissioning, beam modeling and quality assurance purposes.« less
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Kocuria varians infection associated with brain abscess: A case report
2010-01-01
Background Kocuria, established by Stackebrandt et al., previously was classified into Micrococcus. Only two species, K. rosea and K. kristinae are reported to be associated as pathogenic and found with catheter-related bacteremia and acute cholecystitis. Case presentation We herein report the first case of brain abscess caused by Kocuria varians, a gram-positive microorganism, in a 52-year-old man. Hematogenous spread is the probable pathogenesis. Conclusions This report presents a case of Kocuria varians brain abscess successfully treated with surgical excision combined with antimicrobial therapy. In addition, Vitek 2 system has been used to identify and differentiate between coagulase-negative staphylococcus. PMID:20423506
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A simplified approach to characterizing a kilovoltage source spectrum for accurate dose computation.
Poirier, Yannick; Kouznetsov, Alexei; Tambasco, Mauro
2012-06-01
To investigate and validate the clinical feasibility of using half-value layer (HVL) and peak tube potential (kVp) for characterizing a kilovoltage (kV) source spectrum for the purpose of computing kV x-ray dose accrued from imaging procedures. To use this approach to characterize a Varian® On-Board Imager® (OBI) source and perform experimental validation of a novel in-house hybrid dose computation algorithm for kV x-rays. We characterized the spectrum of an imaging kV x-ray source using the HVL and the kVp as the sole beam quality identifiers using third-party freeware Spektr to generate the spectra. We studied the sensitivity of our dose computation algorithm to uncertainties in the beam's HVL and kVp by systematically varying these spectral parameters. To validate our approach experimentally, we characterized the spectrum of a Varian® OBI system by measuring the HVL using a Farmer-type Capintec ion chamber (0.06 cc) in air and compared dose calculations using our computationally validated in-house kV dose calculation code to measured percent depth-dose and transverse dose profiles for 80, 100, and 125 kVp open beams in a homogeneous phantom and a heterogeneous phantom comprising tissue, lung, and bone equivalent materials. The sensitivity analysis of the beam quality parameters (i.e., HVL, kVp, and field size) on dose computation accuracy shows that typical measurement uncertainties in the HVL and kVp (±0.2 mm Al and ±2 kVp, respectively) source characterization parameters lead to dose computation errors of less than 2%. Furthermore, for an open beam with no added filtration, HVL variations affect dose computation accuracy by less than 1% for a 125 kVp beam when field size is varied from 5 × 5 cm(2) to 40 × 40 cm(2). The central axis depth dose calculations and experimental measurements for the 80, 100, and 125 kVp energies agreed within 2% for the homogeneous and heterogeneous block phantoms, and agreement for the transverse dose profiles was within 6%. The HVL and kVp are sufficient for characterizing a kV x-ray source spectrum for accurate dose computation. As these parameters can be easily and accurately measured, they provide for a clinically feasible approach to characterizing a kV energy spectrum to be used for patient specific x-ray dose computations. Furthermore, these results provide experimental validation of our novel hybrid dose computation algorithm. © 2012 American Association of Physicists in Medicine.
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Li, Jun; Shi, Wenyin; Andrews, David; Werner-Wasik, Maria; Lu, Bo; Yu, Yan; Dicker, Adam; Liu, Haisong
2017-06-01
The study was aimed to compare online 6 degree-of-freedom image registrations of TrueBeam cone-beam computed tomography and BrainLab ExacTrac X-ray imaging systems for intracranial radiosurgery. Phantom and patient studies were performed on a Varian TrueBeam STx linear accelerator (version 2.5), which is integrated with a BrainLab ExacTrac imaging system (version 6.1.1). The phantom study was based on a Rando head phantom and was designed to evaluate isocenter location dependence of the image registrations. Ten isocenters at various locations representing clinical treatment sites were selected in the phantom. Cone-beam computed tomography and ExacTrac X-ray images were taken when the phantom was located at each isocenter. The patient study included 34 patients. Cone-beam computed tomography and ExacTrac X-ray images were taken at each patient's treatment position. The 6 degree-of-freedom image registrations were performed on cone-beam computed tomography and ExacTrac, and residual errors calculated from cone-beam computed tomography and ExacTrac were compared. In the phantom study, the average residual error differences (absolute values) between cone-beam computed tomography and ExacTrac image registrations were 0.17 ± 0.11 mm, 0.36 ± 0.20 mm, and 0.25 ± 0.11 mm in the vertical, longitudinal, and lateral directions, respectively. The average residual error differences in the rotation, roll, and pitch were 0.34° ± 0.08°, 0.13° ± 0.09°, and 0.12° ± 0.10°, respectively. In the patient study, the average residual error differences in the vertical, longitudinal, and lateral directions were 0.20 ± 0.16 mm, 0.30 ± 0.18 mm, 0.21 ± 0.18 mm, respectively. The average residual error differences in the rotation, roll, and pitch were 0.40°± 0.16°, 0.17° ± 0.13°, and 0.20° ± 0.14°, respectively. Overall, the average residual error differences were <0.4 mm in the translational directions and <0.5° in the rotational directions. ExacTrac X-ray image registration is comparable to TrueBeam cone-beam computed tomography image registration in intracranial treatments.
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Belosi, Maria F; Rodriguez, Miguel; Fogliata, Antonella; Cozzi, Luca; Sempau, Josep; Clivio, Alessandro; Nicolini, Giorgia; Vanetti, Eugenio; Krauss, Harald; Khamphan, Catherine; Fenoglietto, Pascal; Puxeu, Josep; Fedele, David; Mancosu, Pietro; Brualla, Lorenzo
2014-05-01
Phase-space files for Monte Carlo simulation of the Varian TrueBeam beams have been made available by Varian. The aim of this study is to evaluate the accuracy of the distributed phase-space files for flattening filter free (FFF) beams, against experimental measurements from ten TrueBeam Linacs. The phase-space files have been used as input in PRIMO, a recently released Monte Carlo program based on the PENELOPE code. Simulations of 6 and 10 MV FFF were computed in a virtual water phantom for field sizes 3 × 3, 6 × 6, and 10 × 10 cm(2) using 1 × 1 × 1 mm(3) voxels and for 20 × 20 and 40 × 40 cm(2) with 2 × 2 × 2 mm(3) voxels. The particles contained in the initial phase-space files were transported downstream to a plane just above the phantom surface, where a subsequent phase-space file was tallied. Particles were transported downstream this second phase-space file to the water phantom. Experimental data consisted of depth doses and profiles at five different depths acquired at SSD = 100 cm (seven datasets) and SSD = 90 cm (three datasets). Simulations and experimental data were compared in terms of dose difference. Gamma analysis was also performed using 1%, 1 mm and 2%, 2 mm criteria of dose-difference and distance-to-agreement, respectively. Additionally, the parameters characterizing the dose profiles of unflattened beams were evaluated for both measurements and simulations. Analysis of depth dose curves showed that dose differences increased with increasing field size and depth; this effect might be partly motivated due to an underestimation of the primary beam energy used to compute the phase-space files. Average dose differences reached 1% for the largest field size. Lateral profiles presented dose differences well within 1% for fields up to 20 × 20 cm(2), while the discrepancy increased toward 2% in the 40 × 40 cm(2) cases. Gamma analysis resulted in an agreement of 100% when a 2%, 2 mm criterion was used, with the only exception of the 40 × 40 cm(2) field (∼95% agreement). With the more stringent criteria of 1%, 1 mm, the agreement reduced to almost 95% for field sizes up to 10 × 10 cm(2), worse for larger fields. Unflatness and slope FFF-specific parameters are in line with the possible energy underestimation of the simulated results relative to experimental data. The agreement between Monte Carlo simulations and experimental data proved that the evaluated Varian phase-space files for FFF beams from TrueBeam can be used as radiation sources for accurate Monte Carlo dose estimation, especially for field sizes up to 10 × 10 cm(2), that is the range of field sizes mostly used in combination to the FFF, high dose rate beams.
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Bednarz, Bryan; Xu, X George
2012-01-01
There is a serious and growing concern about the increased risk of radiation-induced second cancers and late tissue injuries associated with radiation treatment. To better understand and to more accurately quantify non-target organ doses due to scatter and leakage radiation from medical accelerators, a detailed Monte Carlo model of the medical linear accelerator is needed. This paper describes the development and validation of a detailed accelerator model of the Varian Clinac operating at 6 and 18 MV beam energies. Over 100 accelerator components have been defined and integrated using the Monte Carlo code MCNPX. A series of in-field and out-of-field dose validation studies were performed. In-field dose distributions calculated using the accelerator models were tuned to match measurement data that are considered the de facto ‘gold standard’ for the Varian Clinac accelerator provided by the manufacturer. Field sizes of 4 cm × 4 cm, 10 cm × 10 cm, 20 cm × 20 cm and 40 cm × 40 cm were considered. The local difference between calculated and measured dose on the percent depth dose curve was less than 2% for all locations. The local difference between calculated and measured dose on the dose profile curve was less than 2% in the plateau region and less than 2 mm in the penumbra region for all locations. Out-of-field dose profiles were calculated and compared to measurement data for both beam energies for field sizes of 4 cm × 4 cm, 10 cm × 10 cm and 20 cm × 20 cm. For all field sizes considered in this study, the average local difference between calculated and measured dose for the 6 and 18 MV beams was 14 and 16%, respectively. In addition, a method for determining neutron contamination in the 18 MV operating model was validated by comparing calculated in-air neutron fluence with reported calculations and measurements. The average difference between calculated and measured neutron fluence was 20%. As one of the most detailed accelerator models for both in-field and out-of-field dose calculations, the model will be combined with anatomically realistic computational patient phantoms into a computational framework to calculate non-target organ doses to patients from various radiation treatment plans. PMID:19141879
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NASA Astrophysics Data System (ADS)
Buckley, J.; Wilkinson, D.; Malaroda, A.; Metcalfe, P.
2017-01-01
Three alternative methodologies to the Computed-Tomography Dose Index for the evaluation of Cone-Beam Computed Tomography dose are compared, the Cone-Beam Dose Index, IAEA Human Health Report No. 5 recommended methodology and the AAPM Task Group 111 recommended methodology. The protocols were evaluated for Pelvis and Thorax scan modes on Varian® On-Board Imager and Truebeam kV XI imaging systems. The weighted planar average dose was highest for the AAPM methodology across all scans, with the CBDI being the second highest overall. A 17.96% and 1.14% decrease from the TG-111 protocol to the IAEA and CBDI protocols for the Pelvis mode and 18.15% and 13.10% decrease for the Thorax mode were observed for the XI system. For the OBI system, the variation was 16.46% and 7.14% for Pelvis mode and 15.93% to the CBDI protocol in Thorax mode respectively.
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Dose computation for therapeutic electron beams
NASA Astrophysics Data System (ADS)
Glegg, Martin Mackenzie
The accuracy of electron dose calculations performed by two commercially available treatment planning computers, Varian Cadplan and Helax TMS, has been assessed. Measured values of absorbed dose delivered by a Varian 2100C linear accelerator, under a wide variety of irradiation conditions, were compared with doses calculated by the treatment planning computers. Much of the motivation for this work was provided by a requirement to verify the accuracy of calculated electron dose distributions in situations encountered clinically at Glasgow's Beatson Oncology Centre. Calculated dose distributions are required in a significant minority of electron treatments, usually in cases involving treatment to the head and neck. Here, therapeutic electron beams are subject to factors which may cause non-uniformity in the distribution of dose, and which may complicate the calculation of dose. The beam shape is often irregular, the beam may enter the patient at an oblique angle or at an extended source to skin distance (SSD), tissue inhomogeneities can alter the dose distribution, and tissue equivalent material (such as wax) may be added to reduce dose to critical organs. Technological advances have allowed the current generation of treatment planning computers to implement dose calculation algorithms with the ability to model electron beams in these complex situations. These calculations have, however, yet to be verified by measurement. This work has assessed the accuracy of calculations in a number of specific instances. Chapter two contains a comparison of measured and calculated planar electron isodose distributions. Three situations were considered: oblique incidence, incidence on an irregular surface (such as that which would be arise from the use of wax to reduce dose to spinal cord), and incidence on a phantom containing a small air cavity. Calculations were compared with measurements made by thermoluminescent dosimetry (TLD) in a WTe electron solid water phantom. Chapter three assesses the planning computers' ability to model electron beam penumbra at extended SSD. Calculations were compared with diode measurements in a water phantom. Further measurements assessed doses in the junction region produced by abutting an extended SSD electron field with opposed photon fields. Chapter four describes an investigation of the size and shape of the region enclosed by the 90% isodose line when produced by limiting the electron beam with square and elliptical apertures. The 90% isodose line was chosen because clinical treatments are often prescribed such that a given volume receives at least 90% dose. Calculated and measured dose distributions were compared in a plane normal to the beam central axis. Measurements were made by film dosimetry. While chapters two to four examine relative doses, chapter five assesses the accuracy of absolute dose (or output) calculations performed by the planning computers. Output variation with SSD and field size was examined. Two further situations already assessed for the distribution of relative dose were also considered: an obliquely incident field, and a field incident on an irregular surface. The accuracy of calculations was assessed against criteria stipulated by the International Commission on Radiation Units and Measurement (ICRU). The Varian Cadplan and Helax TMS treatment planning systems produce acceptable accuracy in the calculation of relative dose from therapeutic electron beams in most commonly encountered situations. When interpreting clinical dose distributions, however, knowledge of the limitations of the calculation algorithm employed by each system is required in order to identify the minority of situations where results are not accurate. The calculation of absolute dose is too inaccurate to implement in a clinical environment. (Abstract shortened by ProQuest.).
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The determination of ethanol in blood and urine by mass fragmentography
NASA Technical Reports Server (NTRS)
Pereira, W. E.; Summons, R. E.; Rindfleisch, T. C.; Duffield, A. M.
1974-01-01
A mass fragmentographic technique for a rapid, specific and sensitive determination of ethanol in blood and urine is described. A Varian gas chromatograph coupled through an all-glass membrane separator to a Finnigan quadripole mass spectrometer and interfaced to a computer system is used for ethanol determination in blood and urine samples. A procedure for plotting calibration curves for ethanol quantitation is also described. Quantitation is achieved by plotting the peak area ratios of undeuterated-to-deuterated ethanol fragment ions against the amount of ethanol added. Representative results obtained by this technique are included.
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Nedaie, Hassan Ali; Darestani, Hoda; Banaee, Nooshin; Shagholi, Negin; Mohammadi, Kheirollah; Shahvar, Arjang; Bayat, Esmaeel
2014-01-01
High-energy linacs produce secondary particles such as neutrons (photoneutron production). The neutrons have the important role during treatment with high energy photons in terms of protection and dose escalation. In this work, neutron dose equivalents of 18 MV Varian and Elekta accelerators are measured by thermoluminescent dosimeter (TLD) 600 and TLD700 detectors and compared with the Monte Carlo calculations. For neutron and photon dose discrimination, first TLDs were calibrated separately by gamma and neutron doses. Gamma calibration was carried out in two procedures; by standard 60Co source and by 18 MV linac photon beam. For neutron calibration by 241Am-Be source, irradiations were performed in several different time intervals. The Varian and Elekta linac heads and the phantom were simulated by the MCNPX code (v. 2.5). Neutron dose equivalent was calculated in the central axis, on the phantom surface and depths of 1, 2, 3.3, 4, 5, and 6 cm. The maximum photoneutron dose equivalents which calculated by the MCNPX code were 7.06 and 2.37 mSv.Gy-1 for Varian and Elekta accelerators, respectively, in comparison with 50 and 44 mSv.Gy-1 achieved by TLDs. All the results showed more photoneutron production in Varian accelerator compared to Elekta. According to the results, it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry inside the linac field due to high photon flux, while MCNPX code is an appropriate alternative for studying photoneutron production. PMID:24600167
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Nedaie, Hassan Ali; Darestani, Hoda; Banaee, Nooshin; Shagholi, Negin; Mohammadi, Kheirollah; Shahvar, Arjang; Bayat, Esmaeel
2014-01-01
High-energy linacs produce secondary particles such as neutrons (photoneutron production). The neutrons have the important role during treatment with high energy photons in terms of protection and dose escalation. In this work, neutron dose equivalents of 18 MV Varian and Elekta accelerators are measured by thermoluminescent dosimeter (TLD) 600 and TLD700 detectors and compared with the Monte Carlo calculations. For neutron and photon dose discrimination, first TLDs were calibrated separately by gamma and neutron doses. Gamma calibration was carried out in two procedures; by standard 60Co source and by 18 MV linac photon beam. For neutron calibration by (241)Am-Be source, irradiations were performed in several different time intervals. The Varian and Elekta linac heads and the phantom were simulated by the MCNPX code (v. 2.5). Neutron dose equivalent was calculated in the central axis, on the phantom surface and depths of 1, 2, 3.3, 4, 5, and 6 cm. The maximum photoneutron dose equivalents which calculated by the MCNPX code were 7.06 and 2.37 mSv.Gy(-1) for Varian and Elekta accelerators, respectively, in comparison with 50 and 44 mSv.Gy(-1) achieved by TLDs. All the results showed more photoneutron production in Varian accelerator compared to Elekta. According to the results, it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry inside the linac field due to high photon flux, while MCNPX code is an appropriate alternative for studying photoneutron production.
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Evaluation of lens absorbed dose with Cone Beam IGRT procedures.
Palomo, R; Pujades, M C; Gimeno-Olmos, J; Carmona, V; Lliso, F; Candela-Juan, C; Vijande, J; Ballester, F; Perez-Calatayud, J
2015-12-01
The purpose of this work is to evaluate the absorbed dose to the eye lenses due to the cone beam computed tomography (CBCT) system used to accurately position the patient during head-and-neck image guided procedures. The on-board imaging (OBI) systems (v.1.5) of Clinac iX and TrueBeam (Varian) accelerators were used to evaluate the imparted dose to the eye lenses and some additional points of the head. All CBCT scans were acquired with the Standard-Dose Head protocol from Varian. Doses were measured using thermoluminescence dosimeters (TLDs) placed in an anthropomorphic phantom. TLDs were calibrated at the beam quality used to reduce their energy dependence. Average dose to the lens due to the OBI systems of the Clinac iX and the TrueBeam were 0.71 ± 0.07 mGy/CBCT and 0.70 ± 0.08 mGy/CBCT, respectively. The extra absorbed dose received by the eye lenses due to one CBCT acquisition with the studied protocol is far below the 500 mGy threshold established by ICRP for cataract formation (ICRP 2011 Statement on Tissue Reactions). However, the incremental effect of several CBCT acquisitions during the whole treatment should be taken into account.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Belosi, Maria F.; Fogliata, Antonella, E-mail: antonella.fogliata-cozzi@eoc.ch, E-mail: afc@iosi.ch; Cozzi, Luca
2014-05-15
Purpose: Phase-space files for Monte Carlo simulation of the Varian TrueBeam beams have been made available by Varian. The aim of this study is to evaluate the accuracy of the distributed phase-space files for flattening filter free (FFF) beams, against experimental measurements from ten TrueBeam Linacs. Methods: The phase-space files have been used as input in PRIMO, a recently released Monte Carlo program based on thePENELOPE code. Simulations of 6 and 10 MV FFF were computed in a virtual water phantom for field sizes 3 × 3, 6 × 6, and 10 × 10 cm{sup 2} using 1 × 1more » × 1 mm{sup 3} voxels and for 20 × 20 and 40 × 40 cm{sup 2} with 2 × 2 × 2 mm{sup 3} voxels. The particles contained in the initial phase-space files were transported downstream to a plane just above the phantom surface, where a subsequent phase-space file was tallied. Particles were transported downstream this second phase-space file to the water phantom. Experimental data consisted of depth doses and profiles at five different depths acquired at SSD = 100 cm (seven datasets) and SSD = 90 cm (three datasets). Simulations and experimental data were compared in terms of dose difference. Gamma analysis was also performed using 1%, 1 mm and 2%, 2 mm criteria of dose-difference and distance-to-agreement, respectively. Additionally, the parameters characterizing the dose profiles of unflattened beams were evaluated for both measurements and simulations. Results: Analysis of depth dose curves showed that dose differences increased with increasing field size and depth; this effect might be partly motivated due to an underestimation of the primary beam energy used to compute the phase-space files. Average dose differences reached 1% for the largest field size. Lateral profiles presented dose differences well within 1% for fields up to 20 × 20 cm{sup 2}, while the discrepancy increased toward 2% in the 40 × 40 cm{sup 2} cases. Gamma analysis resulted in an agreement of 100% when a 2%, 2 mm criterion was used, with the only exception of the 40 × 40 cm{sup 2} field (∼95% agreement). With the more stringent criteria of 1%, 1 mm, the agreement reduced to almost 95% for field sizes up to 10 × 10 cm{sup 2}, worse for larger fields. Unflatness and slope FFF-specific parameters are in line with the possible energy underestimation of the simulated results relative to experimental data. Conclusions: The agreement between Monte Carlo simulations and experimental data proved that the evaluated Varian phase-space files for FFF beams from TrueBeam can be used as radiation sources for accurate Monte Carlo dose estimation, especially for field sizes up to 10 × 10 cm{sup 2}, that is the range of field sizes mostly used in combination to the FFF, high dose rate beams.« less
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Optimization of image quality and dose for Varian aS500 electronic portal imaging devices (EPIDs).
McGarry, C K; Grattan, M W D; Cosgrove, V P
2007-12-07
This study was carried out to investigate whether the electronic portal imaging (EPI) acquisition process could be optimized, and as a result tolerance and action levels be set for the PIPSPro QC-3V phantom image quality assessment. The aim of the optimization process was to reduce the dose delivered to the patient while maintaining a clinically acceptable image quality. This is of interest when images are acquired in addition to the planned patient treatment, rather than images being acquired using the treatment field during a patient's treatment. A series of phantoms were used to assess image quality for different acquisition settings relative to the baseline values obtained following acceptance testing. Eight Varian aS500 EPID systems on four matched Varian 600C/D linacs and four matched Varian 2100C/D linacs were compared for consistency of performance and images were acquired at the four main orthogonal gantry angles. Images were acquired using a 6 MV beam operating at 100 MU min(-1) and the low-dose acquisition mode. Doses used in the comparison were measured using a Farmer ionization chamber placed at d(max) in solid water. The results demonstrated that the number of reset frames did not have any influence on the image contrast, but the number of frame averages did. The expected increase in noise with corresponding decrease in contrast was also observed when reducing the number of frame averages. The optimal settings for the low-dose acquisition mode with respect to image quality and dose were found to be one reset frame and three frame averages. All patients at the Northern Ireland Cancer Centre are now imaged using one reset frame and three frame averages in the 6 MV 100 MU min(-1) low-dose acquisition mode. Routine EPID QC contrast tolerance (+/-10) and action (+/-20) levels using the PIPSPro phantom based around expected values of 190 (Varian 600C/D) and 225 (Varian 2100C/D) have been introduced. The dose at dmax from electronic portal imaging has been reduced by approximately 28%, and while the image quality has been reduced, the images produced are still clinically acceptable.
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1986-06-06
Varian. WCOT, Vit. Silica) or in the case of the stilbenes by HPLC analysis using an Ultrasphere-Octyl column eluting with 70:30 = MeOH:H 20 (v/v...the formation of each individual product was followed by HPLC at several wavelengths and the rate constants computed for their appearance. Given this...HN R b) CH3COOHI 200 1 1 .nf IN HN R CH2CH] HPLC 13 IASTEREO*.RS Id 8.0 10-3 M MAIN ISOMER ccctc I X- RAY) .ot ’ 1 V . ’ R WAOITSCHATKA /J \\ / FIGURE
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Kamekura, M; Hamakawa, T; Onishi, H
1982-01-01
RNA was degraded at 60 degrees C for 24 h by halophilic nuclease H in supernatants from broth cultures of Micrococcus varians subsp. halophilus containing 12% NaCl. Since contaminating 5'-nucleotidase exhibited almost no activity under these conditions, the 5'-GMP formed could be recovered from the reaction mixture, and the yield was 805 mg from 5 g of RNA. PMID:6184020
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Computational study of radiation doses at UNLV accelerator facility
NASA Astrophysics Data System (ADS)
Hodges, Matthew; Barzilov, Alexander; Chen, Yi-Tung; Lowe, Daniel
2017-09-01
A Varian K15 electron linear accelerator (linac) has been considered for installation at University of Nevada, Las Vegas (UNLV). Before experiments can be performed, it is necessary to evaluate the photon and neutron spectra as generated by the linac, as well as the resulting dose rates within the accelerator facility. A computational study using MCNPX was performed to characterize the source terms for the bremsstrahlung converter. The 15 MeV electron beam available in the linac is above the photoneutron threshold energy for several materials in the linac assembly, and as a result, neutrons must be accounted for. The angular and energy distributions for bremsstrahlung flux generated by the interaction of the 15 MeV electron beam with the linac target were determined. This source term was used in conjunction with the K15 collimators to determine the dose rates within the facility.
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E-Bomb: The Key Element of the Contemporary Military-Technical Revolution
2008-09-01
section. (1) Klystron . The klystron is a high -frequency oscillator and amplifier that was invented in the late 1930s by R. H. Varian and S . F. Varian... klystrons became commercially available. However, a relativistic magnetron source in the L band producing 1.8 GW of peak power is now commercially...Altitude Electromagnetic Pulse (HEMP) and High Power Microwave (HPM) Weapons. In addition, a measure of effectiveness model is proposed to compare the
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SU-F-T-465: Two Years of Radiotherapy Treatments Analyzed Through MLC Log Files
DOE Office of Scientific and Technical Information (OSTI.GOV)
Defoor, D; Kabat, C; Papanikolaou, N
Purpose: To present treatment statistics of a Varian Novalis Tx using more than 90,000 Varian Dynalog files collected over the past 2 years. Methods: Varian Dynalog files are recorded for every patient treated on our Varian Novalis Tx. The files are collected and analyzed daily to check interfraction agreement of treatment deliveries. This is accomplished by creating fluence maps from the data contained in the Dynalog files. From the Dynalog files we have also compiled statistics for treatment delivery times, MLC errors, gantry errors and collimator errors. Results: The mean treatment time for VMAT patients was 153 ± 86 secondsmore » while the mean treatment time for step & shoot was 256 ± 149 seconds. Patient’s treatment times showed a variation of 0.4% over there treatment course for VMAT and 0.5% for step & shoot. The average field sizes were 40 cm2 and 26 cm2 for VMAT and step & shoot respectively. VMAT beams contained and average overall leaf travel of 34.17 meters and step & shoot beams averaged less than half of that at 15.93 meters. When comparing planned and delivered fluence maps generated using the Dynalog files VMAT plans showed an average gamma passing percentage of 99.85 ± 0.47. Step & shoot plans showed an average gamma passing percentage of 97.04 ± 0.04. 5.3% of beams contained an MLC error greater than 1 mm and 2.4% had an error greater than 2mm. The mean gantry speed for VMAT plans was 1.01 degrees/s with a maximum of 6.5 degrees/s. Conclusion: Varian Dynalog files are useful for monitoring machine performance treatment parameters. The Dynalog files have shown that the performance of the Novalis Tx is consistent over the course of a patients treatment with only slight variations in patient treatment times and a low rate of MLC errors.« less
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Cardenas, Carlos E; Nitsch, Paige L; Kudchadker, Rajat J; Howell, Rebecca M; Kry, Stephen F
2016-07-08
Out-of-field doses from radiotherapy can cause harmful side effects or eventually lead to secondary cancers. Scattered doses outside the applicator field, neutron source strength values, and neutron dose equivalents have not been broadly investigated for high-energy electron beams. To better understand the extent of these exposures, we measured out-of-field dose characteristics of electron applicators for high-energy electron beams on two Varian 21iXs, a Varian TrueBeam, and an Elekta Versa HD operating at various energy levels. Out-of-field dose profiles and percent depth-dose curves were measured in a Wellhofer water phantom using a Farmer ion chamber. Neutron dose was assessed using a combination of moderator buckets and gold activation foils placed on the treatment couch at various locations in the patient plane on both the Varian 21iX and Elekta Versa HD linear accelerators. Our findings showed that out-of-field electron doses were highest for the highest electron energies. These doses typically decreased with increasing distance from the field edge but showed substantial increases over some distance ranges. The Elekta linear accelerator had higher electron out-of-field doses than the Varian units examined, and the Elekta dose profiles exhibited a second dose peak about 20 to 30 cm from central-axis, which was found to be higher than typical out-of-field doses from photon beams. Electron doses decreased sharply with depth before becoming nearly constant; the dose was found to decrease to a depth of approximately E(MeV)/4 in cm. With respect to neutron dosimetry, Q values and neutron dose equivalents increased with electron beam energy. Neutron contamination from electron beams was found to be much lower than that from photon beams. Even though the neutron dose equivalent for electron beams represented a small portion of neutron doses observed under photon beams, neutron doses from electron beams may need to be considered for special cases.
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WE-G-BRF-07: Non-Circular Scanning Trajectories with Varian Developer Mode
DOE Office of Scientific and Technical Information (OSTI.GOV)
Davis, A; Pearson, E; Pan, X
2014-06-15
Purpose: Cone-beam CT (CBCT) in image-guide radiation therapy (IGRT) typicallyacquires scan data via the circular trajectory of the linearaccelerator's (linac) gantry rotation. Though this lends itself toanalytic reconstruction algorithms like FDK, iterative reconstructionalgorithms allow for a broader range of scanning trajectories. Weimplemented a non-circular scanning trajectory with Varian's TrueBeamDeveloper Mode and performed some preliminary reconstructions toverify the geometry. Methods: We used TrueBeam Developer Mode to program a new scanning trajectorythat increases the field of view (FOV) along the gantry rotation axiswithout moving the patient. This trajectory consisted of moving thegantry in a circle, then translating the source and detector alongmore » theaxial direction before acquiring another circular scan 19 cm away fromthe first. The linear portion of the trajectory includes an additional4.5 cm above and below the axial planes of the source's circularrotation. We scanned a calibration phantom consisting of a lucite tubewith a spiral pattern of CT spots and used the maximum-likelihoodalgorithm to iteratively reconstruct the CBCT volume. Results: With the TrueBeam trajectory definition, we acquired projection dataof the calibration phantom using the previously described trajectory.We obtained a scan of the treatment couch for log normalization byscanning with the same trajectory but without the phantom present.Using the nominal geometric parameters reported in the projectionheaders with our iterative reconstruction algorithm, we obtained acorrect reconstruction of the calibration phantom. Conclusion: The ability to implement new scanning trajectories with the TrueBeamDeveloper Mode enables us access to a new parameter space for imagingwith CBCT for IGRT. Previous simulations and simple dual circle scanshave shown iterative reconstruction with non-circular trajectories canincrease the axial FOV with CBCT. Use of Developer Mode allowsexperimentally testing these and other new scanning trajectories. Support was provided in part by the University of Chicago Research Computing Center, Varian Medical Systems, and NIH Grants 1RO1CA120540, T32EB002103, S10 RR021039 and P30 CA14599. The contents of this work are solely the responsibility of the authors and do not necessarily represent the official views of the supporting organizations.« less
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Dosimetric Comparison in Breast Radiotherapy of 4 MV and 6 MV on Physical Chest Simulator
DOE Office of Scientific and Technical Information (OSTI.GOV)
Donato da Silva, Sabrina; Passos Ribeiro Campos, Tarcisio; Batista Nogueira, Luciana
2015-07-01
According to the World Health Organization (2014) breast cancer is the main cause of death by cancer in women worldwide. The biggest challenge of radiotherapy in the treatment of cancer is to deposit the entire prescribed dose homogeneously in the breast, sparing the surrounding tissue. In this context, this paper aimed at evaluating and comparing internal dose distribution in the mammary gland based on experimental procedures submitted to two distinct energy spectra produced in breast cancer radiotherapy. The methodology consisted of reproducing opposite parallel fields used in the treatment of breast tumors in a chest phantom. This simulator with syntheticmore » breast, composed of equivalent tissue material (TE), was previously developed by the NRI Research Group (UFMG). The computer tomography (CT) scan of the simulator was obtained antecedently. The radiotherapy planning systems (TPS) in the chest phantom were performed in the ECLIPSE system from Varian Medical Systems and CAT 3D system from MEVIS. The irradiations were reproduced in the Varian linear accelerator, model SL- 20 Precise, 6 MV energy and Varian linear accelerator, 4 MV Clinac 6x SN11 model. Calibrations of the absorbed dose versus optical density from radiochromic films were generated in order to obtain experimental dosimetric distribution at the films positioned within the glandular and skin equivalent tissues of the chest phantom. The spatial dose distribution showed equivalence with the TPS on measurement data performed in the 6 MV spectrum. The average dose found in radiochromic films placed on the skin ranged from 49 to 79%, and from 39 to 49% in the mammary areola, for the prescribed dose. Dosimetric comparisons between the spectra of 4 and 6 MV, keeping the constant geometry of the fields applied in the same phantom, will be presented showing their equivalence in breast radiotherapy, as well as the variations will be discussed. To sum up, the dose distribution has reached the value expected in the breast dose of the 180 cGy in a wide range of the film in the glandular TE in both spectra. (authors)« less
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Harmony search optimization for HDR prostate brachytherapy
NASA Astrophysics Data System (ADS)
Panchal, Aditya
In high dose-rate (HDR) prostate brachytherapy, multiple catheters are inserted interstitially into the target volume. The process of treating the prostate involves calculating and determining the best dose distribution to the target and organs-at-risk by means of optimizing the time that the radioactive source dwells at specified positions within the catheters. It is the goal of this work to investigate the use of a new optimization algorithm, known as Harmony Search, in order to optimize dwell times for HDR prostate brachytherapy. The new algorithm was tested on 9 different patients and also compared with the genetic algorithm. Simulations were performed to determine the optimal value of the Harmony Search parameters. Finally, multithreading of the simulation was examined to determine potential benefits. First, a simulation environment was created using the Python programming language and the wxPython graphical interface toolkit, which was necessary to run repeated optimizations. DICOM RT data from Varian BrachyVision was parsed and used to obtain patient anatomy and HDR catheter information. Once the structures were indexed, the volume of each structure was determined and compared to the original volume calculated in BrachyVision for validation. Dose was calculated using the AAPM TG-43 point source model of the GammaMed 192Ir HDR source and was validated against Varian BrachyVision. A DVH-based objective function was created and used for the optimization simulation. Harmony Search and the genetic algorithm were implemented as optimization algorithms for the simulation and were compared against each other. The optimal values for Harmony Search parameters (Harmony Memory Size [HMS], Harmony Memory Considering Rate [HMCR], and Pitch Adjusting Rate [PAR]) were also determined. Lastly, the simulation was modified to use multiple threads of execution in order to achieve faster computational times. Experimental results show that the volume calculation that was implemented in this thesis was within 2% of the values computed by Varian BrachyVision for the prostate, within 3% for the rectum and bladder and 6% for the urethra. The calculation of dose compared to BrachyVision was determined to be different by only 0.38%. Isodose curves were also generated and were found to be similar to BrachyVision. The comparison between Harmony Search and genetic algorithm showed that Harmony Search was over 4 times faster when compared over multiple data sets. The optimal Harmony Memory Size was found to be 5 or lower; the Harmony Memory Considering Rate was determined to be 0.95, and the Pitch Adjusting Rate was found to be 0.9. Ultimately, the effect of multithreading showed that as intensive computations such as optimization and dose calculation are involved, the threads of execution scale with the number of processors, achieving a speed increase proportional to the number of processor cores. In conclusion, this work showed that Harmony Search is a viable alternative to existing algorithms for use in HDR prostate brachytherapy optimization. Coupled with the optimal parameters for the algorithm and a multithreaded simulation, this combination has the capability to significantly decrease the time spent on minimizing optimization problems in the clinic that are time intensive, such as brachytherapy, IMRT and beam angle optimization.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Fave, X; Fried, D; UT Health Science Center Graduate School of Biomedical Sciences, Houston, TX
2015-06-15
Purpose: Several studies have demonstrated the prognostic potential for texture features extracted from CT images of non-small cell lung cancer (NSCLC) patients. The purpose of this study was to determine if these features could be extracted with high reproducibility from cone-beam CT (CBCT) images in order for features to be easily tracked throughout a patient’s treatment. Methods: Two materials in a radiomics phantom, designed to approximate NSCLC tumor texture, were used to assess the reproducibility of 26 features. This phantom was imaged on 9 CBCT scanners, including Elekta and Varian machines. Thoracic and head imaging protocols were acquired on eachmore » machine. CBCT images from 27 NSCLC patients imaged using the thoracic protocol on Varian machines were obtained for comparison. The variance for each texture measured from these patients was compared to the variance in phantom values for different manufacturer/protocol subsets. Levene’s test was used to identify features which had a significantly smaller variance in the phantom scans versus the patient data. Results: Approximately half of the features (13/26 for material1 and 15/26 for material2) had a significantly smaller variance (p<0.05) between Varian thoracic scans of the phantom compared to patient scans. Many of these same features remained significant for the head scans on Varian (12/26 and 8/26). However, when thoracic scans from Elekta and Varian were combined, only a few features were still significant (4/26 and 5/26). Three features (skewness, coarsely filtered mean and standard deviation) were significant in almost all manufacturer/protocol subsets. Conclusion: Texture features extracted from CBCT images of a radiomics phantom are reproducible and show significantly less variation than the same features measured from patient images when images from the same manufacturer or with similar parameters are used. Reproducibility between CBCT scanners may be high enough to allow the extraction of meaningful texture values for patients. This project was funded in part by the Cancer Prevention Research Institute of Texas (CPRIT). Xenia Fave is a recipient of the American Association of Physicists in Medicine Graduate Fellowship.« less
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Brushed permanent magnet DC MLC motor operation in an external magnetic field.
Yun, J; St Aubin, J; Rathee, S; Fallone, B G
2010-05-01
Linac-MR systems for real-time image-guided radiotherapy will utilize the multileaf collimators (MLCs) to perform conformal radiotherapy and tumor tracking. The MLCs would be exposed to the external fringe magnetic fields of the linac-MR hybrid systems. Therefore, an experimental investigation of the effect of an external magnetic field on the brushed permanent magnet DC motors used in some MLC systems was performed. The changes in motor speed and current were measured for varying external magnetic field strengths up to 2000 G generated by an EEV electromagnet. These changes in motor characteristics were measured for three orientations of the motor in the external magnetic field, mimicking changes in motor orientations due to installation and/or collimator rotations. In addition, the functionality of the associated magnetic motor encoder was tested. The tested motors are used with the Varian 120 leaf Millennium MLC (Maxon Motor half leaf and full leaf motors) and the Varian 52 leaf MKII MLC (MicroMo Electronics leaf motor) including a carriage motor (MicroMo Electronics). In most cases, the magnetic encoder of the motors failed prior to any damage to the gearbox or the permanent magnet motor itself. This sets an upper limit of the external magnetic field strength on the motor function. The measured limits of the external magnetic fields were found to vary by the motor type. The leaf motor used with a Varian 52 leaf MKII MLC system tolerated up to 450 +/- 10 G. The carriage motor tolerated up to 2000 +/- 10 G field. The motors used with the Varian 120 leaf Millennium MLC system were found to tolerate a maximum of 600 +/- 10 G. The current Varian MLC system motors can be used for real-time image-guided radiotherapy coupled to a linac-MR system, provided the fringe magnetic fields at their locations are below the determined tolerance levels. With the fringe magnetic fields of linac-MR systems expected to be larger than the tolerance levels determined, some form of magnetic shielding would be required.
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Poster - 53: Improving inter-linac DMLC IMRT dose precision by fine tuning of MLC leaf calibration
DOE Office of Scientific and Technical Information (OSTI.GOV)
Nakonechny, Keith; Tran, Muoi; Sasaki, David
Purpose: To develop a method to improve the inter-linac precision of DMLC IMRT dosimetry. Methods: The distance between opposing MLC leaf banks (“gap size”) can be finely tuned on Varian linacs. The dosimetric effect due to small deviations from the nominal gap size (“gap error”) was studied by introducing known errors for several DMLC sliding gap sizes, and for clinical plans based on the TG119 test cases. The plans were delivered on a single Varian linac and the relationship between gap error and the corresponding change in dose was measured. The plans were also delivered on eight Varian 2100 seriesmore » linacs (at two institutions) in order to quantify the inter-linac variation in dose before and after fine tuning the MLC calibration. Results: The measured dose differences for each field agreed well with the predictions of LoSasso et al. Using the default MLC calibration, the variation in the physical MLC gap size was determined to be less than 0.4 mm between all linacs studied. The dose difference between the linacs with the largest and smallest physical gap was up to 5.4% (spinal cord region of the head and neck TG119 test case). This difference was reduced to 2.5% after fine tuning the MLC gap calibration. Conclusions: The inter-linac dose precision for DMLC IMRT on Varian linacs can be improved using a simple modification of the MLC calibration procedure that involves fine adjustment of the nominal gap size.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Schmidt, M; Knutson, N; University of Rhode Island, Kingston, RI
2016-06-15
Purpose: Development of an in-house program facilitates a workflow that allows Electronic Portal Imaging Device (EPID) patient specific quality assurance (QA) measurements to be acquired and analyzed in the Portal Dosimetry Application (Varian Medical Systems, Palo Alto, CA) using a non-Aria Record and Verify (R&V) system (MOSAIQ, Elekta, Crawley, UK) to deliver beams in standard clinical treatment mode. Methods: Initial calibration of an in-house software tool includes characterization of EPID dosimetry parameters by importing DICOM images of varying delivered MUs to determine linear mapping factors in order to convert image pixel values to Varian-defined Calibrated Units (CU). Using this information,more » the Portal Dose Image Prediction (PDIP) algorithm was commissioned by converting images of various field sizes to output factors using the Eclipse Scripting Application Programming Interface (ESAPI) and converting a delivered configuration fluence to absolute dose units. To verify the algorithm configuration, an integrated image was acquired, exported directly from the R&V client, automatically converted to a compatible, calibrated dosimetric image, and compared to a PDIP calculated image using Varian’s Portal Dosimetry Application. Results: For two C-Series and one TrueBeam Varian linear accelerators, gamma comparisons (global 3% / 3mm) of PDIP algorithm predicted dosimetric images and images converted via the inhouse system demonstrated agreement for ≥99% of all pixels, exceeding vendor-recommended commissioning guidelines. Conclusion: Combinations of a programmatic image conversion tool and ESAPI allow for an efficient and accurate method of patient IMRT QA incorporating a 3rd party R&V system.« less
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Poster — Thur Eve — 55: An automated XML technique for isocentre verification on the Varian TrueBeam
DOE Office of Scientific and Technical Information (OSTI.GOV)
Asiev, Krum; Mullins, Joel; DeBlois, François
2014-08-15
Isocentre verification tests, such as the Winston-Lutz (WL) test, have gained popularity in the recent years as techniques such as stereotactic radiosurgery/radiotherapy (SRS/SRT) treatments are more commonly performed on radiotherapy linacs. These highly conformal treatments require frequent monitoring of the geometrical accuracy of the isocentre to ensure proper radiation delivery. At our clinic, the WL test is performed by acquiring with the EPID a collection of 8 images of a WL phantom fixed on the couch for various couch/gantry angles. This set of images is later analyzed to determine the isocentre size. The current work addresses the acquisition process. Amore » manual WL test acquisition performed by and experienced physicist takes in average 25 minutes and is prone to user manipulation errors. We have automated this acquisition on a Varian TrueBeam STx linac (Varian, Palo Alto, USA). The Varian developer mode allows the execution of custom-made XML script files to control all aspects of the linac operation. We have created an XML-WL script that cycles through each couch/gantry combinations taking an EPID image at each position. This automated acquisition is done in less than 4 minutes. The reproducibility of the method was verified by repeating the execution of the XML file 5 times. The analysis of the images showed variation of the isocenter size less than 0.1 mm along the X, Y and Z axes and compares favorably to a manual acquisition for which we typically observe variations up to 0.5 mm.« less
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Total centralisation and optimisation of an oncology management suite via Citrix®
NASA Astrophysics Data System (ADS)
James, C.; Frantzis, J.; Ripps, L.; Fenton, P.
2014-03-01
The management of patient information and treatment planning is traditionally an intra-departmental requirement of a radiation oncology service. Epworth Radiation Oncology systems must support the transient nature of Visiting Medical Officers (VMOs). This unique work practice created challenges when implementing the vision of a completely paperless solution that allows for a responsive and efficient service delivery. ARIA® and EclipseTM (Varian Medical Systems, Palo Alto, CA, USA) have been deployed across four dedicated Citrix® (Citrix Systems, Santa Clara, CA, USA) servers allowing VMOs to access these applications remotely. A range of paperless solutions were developed within ARIA® to facilitate clinical and organisational management whilst optimising efficient work practices. The IT infrastructure and paperless workflow has enabled VMOs to securely access the VarianTM (Varian Medical Systems, Palo Alto, CA, USA) oncology software and experience full functionality from any location on multiple devices. This has enhanced access to patient information and improved the responsiveness of the service. Epworth HealthCare has developed a unique solution to enable remote access to a centralised oncology management suite, while maintaining a secure and paperless working environment.
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TH-AB-202-07: Radar Tracking of Respiratory Motion in Real Time
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fung, A; Li, C; Torres, C
Purpose: To propose a method of real time tracking of respiratory motion in patients undergoing radiation therapy. Radar technology can be employed to detection the movement of diaphragm and thoracic anatomy. Methods: A radar transceiver was specially designed. During experiment, the radar device was securely attached to a fixed frame. Respiratory motion was simulated with: 1) Varian RPM phantom, 2) Standard Imaging Respiratory Gating Platform. Signals recorded with radar equipment were compared with those measured with Varian RPM system as a reference. Results: Motion generated by Varian RPM phantom was recorded by the radar device, and compared to the signalsmore » recorded by RPM camera. The results showed exact agreement between the two monitoring equipments. Motion was also generated by Standard Imaging Respiratory Motion Platform. The results showed the radar device was capable of measuring motion of various amplitudes and periods. Conclusion: The proposed radar device is able to measure movements such as respiratory motion. Compared to state-of-the-art respiratory detection instrument, the radar device is shown to be equally precise and effective for monitoring respiration in radiation oncology patients.« less
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NASA Technical Reports Server (NTRS)
Hoffer, R. M. (Principal Investigator)
1979-01-01
The spatial characteristics of the data were evaluated. A program was developed to reduce the spatial distortions resulting from variable viewing distance, and geometrically adjusted data sets were generated. The potential need for some level of radiometric adjustment was evidenced by an along track band of high reflectance across different cover types in the Varian imagery. A multiple regression analysis was employed to explore the viewing angle effect on measured reflectance. Areas in the data set which appeared to have no across track stratification of cover type were identified. A program was developed which computed the average reflectance by column for each channel, over all of the scan lines in the designated areas. A regression analysis was then run using the first, second, and third degree polynomials, for each channel. An atmospheric effect as a component of the viewing angle source of variance is discussed. Cover type maps were completed and training and test field selection was initiated.
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NASA Astrophysics Data System (ADS)
Tsivilskiy, I. V.; Nagulin, K. Yu.; Gilmutdinov, A. Kh.
2016-02-01
A full three-dimensional nonstationary numerical model of graphite electrothermal atomizers of various types is developed. The model is based on solution of a heat equation within solid walls of the atomizer with a radiative heat transfer and numerical solution of a full set of Navier-Stokes equations with an energy equation for a gas. Governing equations for the behavior of a discrete phase, i.e., atomic particles suspended in a gas (including gas-phase processes of evaporation and condensation), are derived from the formal equations molecular kinetics by numerical solution of the Hertz-Langmuir equation. The following atomizers test the model: a Varian standard heated electrothermal vaporizer (ETV), a Perkin Elmer standard THGA transversely heated graphite tube with integrated platform (THGA), and the original double-stage tube-helix atomizer (DSTHA). The experimental verification of computer calculations is carried out by a method of shadow spectral visualization of the spatial distributions of atomic and molecular vapors in an analytical space of an atomizer.
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Halophilic Nuclease from a Moderately Halophilic Micrococcus varians
Kamekura, Masahiro; Onishi, Hiroshi
1974-01-01
The moderately halophilic bacterium Micrococcus varians, isolated from soy sauce mash, produced extracellular nuclease when cultivated aerobically in media containing 1 to 4 M NaCl or KCl. The enzyme, purified to an electrophoretically homogeneous state, had both ribonuclease and deoxyribonuclease activities. The nuclease had maximal activity in the presence of 2.9 M NaCl or 2.1 M KCl at 40 C. The enzymatic activity was lost by dialysis against low-salt buffer, whereas when the inactivated enzyme was dialyzed against 3.4 M NaCl buffer as much as 77% of the initial activity could be restored. Images PMID:4852218
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Validation of stationary phases in (111)In-pentetreotide planar chromatography.
Moreno-Ortega, E; Mena-Bares, L M; Maza-Muret, F R; Hidalgo-Ramos, F J; Vallejo-Casas, J A
2013-01-01
Since Pall-German stopped manufacturing ITLC-SG, it has become necessary to validate alternative stationary phases. To validate different stationary phases versus ITLC-SG Pall-Gelman in the determination of the radiochemical purity (RCP) of (111)In-pentetreotide ((111)In-Octreoscan) by planar chromatography. We conducted a case-control study, which included 66 (111)In-pentetreotide preparations. We determined the RCP by planar chromatography, using a freshly prepared solution of 0,1M sodium citrate (pH 5) and the following stationary phases: ITLC-SG (Pall-Gelman) (reference method), iTLC-SG (Varian), HPTLC silica gel 60 (Merck), Whatman 1, Whatman 3MM and Whatman 17. For each of the methods, we calculated: PRQ, relative front values (RF) of the radiopharmaceutical and free (111)In, chromatographic development time, resolution between peaks. We compared the results obtained with the reference method. The statistical analysis was performed using the SPSS program. The p value was calculated for the study of statistical significance. The highest resolution is obtained with HPTLC silica gel 60 (Merck). However, the chromatographic development time is too long (mean=33.62minutes). Greater resolution is obtained with iTLC-SG (Varian) than with the reference method, with lower chromatographic development time (mean=3.61minutes). Very low resolutions are obtained with Whatman paper, essentially with Whatman 1 and 3MM. Therefore, we do not recommend their use. Although iTLC-SG (Varian) and HPTLC silica gel 60 (Merck) are suitable alternatives to ITLC-SG (Pall-Gelman) in determining the RCP of (111)In-pentetreotide, iTLC-SG (Varian) is the method of choice due to its lower chromatographic development time. Copyright © 2012 Elsevier España, S.L. and SEMNIM. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zakjevskii, V; Knill, C; Rakowski, J
2014-06-01
Purpose: To develop a comprehensive end-to-end test for Varian's TrueBeam linear accelerator for head and neck IMRT using a custom phantom designed to utilize multiple dosimetry devices. Methods: The initial end-to-end test and custom H and N phantom were designed to yield maximum information in anatomical regions significant to H and N plans with respect to: i) geometric accuracy, ii) dosimetric accuracy, and iii) treatment reproducibility. The phantom was designed in collaboration with Integrated Medical Technologies. A CT image was taken with a 1mm slice thickness. The CT was imported into Varian's Eclipse treatment planning system, where OARs and themore » PTV were contoured. A clinical template was used to create an eight field static gantry angle IMRT plan. After optimization, dose was calculated using the Analytic Anisotropic Algorithm with inhomogeneity correction. Plans were delivered with a TrueBeam equipped with a high definition MLC. Preliminary end-to-end results were measured using film and ion chambers. Ion chamber dose measurements were compared to the TPS. Films were analyzed with FilmQAPro using composite gamma index. Results: Film analysis for the initial end-to-end plan with a geometrically simple PTV showed average gamma pass rates >99% with a passing criterion of 3% / 3mm. Film analysis of a plan with a more realistic, ie. complex, PTV yielded pass rates >99% in clinically important regions containing the PTV, spinal cord and parotid glands. Ion chamber measurements were on average within 1.21% of calculated dose for both plans. Conclusion: trials have demonstrated that our end-to-end testing methods provide baseline values for the dosimetric and geometric accuracy of Varian's TrueBeam system.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhan, Lixin; Jiang, Runqing; Osei, Ernest K.
2014-08-15
Flattening filter free (FFF) beams have been adopted by many clinics and used for patient treatment. However, compared to the traditional flattened beams, we have limited knowledge of FFF beams. In this study, we successfully modeled the 6 MV FFF beam for Varian TrueBeam accelerator with the Monte Carlo (MC) method. Both the percentage depth dose and profiles match well to the Golden Beam Data (GBD) from Varian. MC simulations were then performed to predict the relative output factors. The in-water output ratio, Scp, was simulated in water phantom and data obtained agrees well with GBD. The in-air output ratio,more » Sc, was obtained by analyzing the phase space placed at isocenter, in air, and computing the ratio of water Kerma rates for different field sizes. The phantom scattering factor, Sp, can then be obtained from the traditional way of taking the ratio of Scp and Sc. We also simulated Sp using a recently proposed method based on only the primary beam dose delivery in water phantom. Because there is no concern of lateral electronic disequilibrium, this method is more suitable for small fields. The results from both methods agree well with each other. The flattened 6 MV beam was simulated and compared to 6 MV FFF. The comparison confirms that 6 MV FFF has less scattering from the Linac head and less phantom scattering contribution to the central axis dose, which will be helpful for improving accuracy in beam modeling and dose calculation in treatment planning systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Sempau, Josep; Badal, Andreu; Brualla, Lorenzo
Purpose: Two new codes, PENEASY and PENEASYLINAC, which automate the Monte Carlo simulation of Varian Clinacs of the 600, 1800, 2100, and 2300 series, together with their electron applicators and multileaf collimators, are introduced. The challenging case of a relatively small and far-from-axis field has been studied with these tools. Methods: PENEASY is a modular, general-purpose main program for the PENELOPE Monte Carlo system that includes various source models, tallies and variance-reduction techniques (VRT). The code includes a new geometry model that allows the superposition of voxels and objects limited by quadric surfaces. A variant of the VRT known asmore » particle splitting, called fan splitting, is also introduced. PENEASYLINAC, in turn, automatically generates detailed geometry and configuration files to simulate linacs with PENEASY. These tools are applied to the generation of phase-space files, and of the corresponding absorbed dose distributions in water, for two 6 MV photon beams from a Varian Clinac 2100 C/D: a 40 x 40 cm{sup 2} centered field; and a 3 x 5 cm{sup 2} field centered at (4.5, -11.5) cm from the beam central axis. This latter configuration implies the largest possible over-traveling values of two of the jaws. Simulation results for the depth dose and lateral profiles at various depths are compared, by using the gamma index, with experimental values obtained with a PTW 31002 ionization chamber. The contribution of several VRTs to the computing speed of the more demanding off-axis case is analyzed. Results: For the 40 x 40 cm{sup 2} field, the percentages {gamma}{sub 1} and {gamma}{sub 1.2} of voxels with gamma indices (using 0.2 cm and 2% criteria) larger than unity and larger than 1.2 are 0.2% and 0%, respectively. For the 3 x 5 cm{sup 2} field, {gamma}{sub 1} = 0%. These figures indicate an excellent agreement between simulation and experiment. The dose distribution for the off-axis case with voxels of 2.5 x 2.5 x 2.5 mm{sup 3} and an average standard statistical uncertainty of 2% (1{sigma}) is computed in 3.1 h on a single core of a 2.8 GHz Intel Core 2 Duo processor. This result is obtained with the optimal combination of the tested VRTs. In particular, fan splitting for the off-axis case accelerates execution by a factor of 240 with respect to standard particle splitting. Conclusions: PENEASY and PENEASYLINAC can simulate the considered Varian Clinacs both in an accurate and efficient manner. Fan splitting is crucial to achieve simulation results for the off-axis field in an affordable amount of CPU time. Work to include Elekta linacs and to develop a graphical interface that will facilitate user input is underway.« less
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Shielding evaluation for IMRT implementation in an existing accelerator vault
Price, R. A.; Chibani, O.; Ma, C.‐M.
2003-01-01
A formalism is developed for evaluating the shielding in an existing vault to be used for IMRT. Existing exposure rate measurements are utilized as well as a newly developed effective modulation scaling factor. Examples are given for vaults housing 6, 10 and 18 MV linear accelerators. The use of an 18 MV Siemens linear accelerator is evaluated for IMRT delivery with respect to neutron production and the effects on individual patients. A modified modulation scaling factor is developed and the risk of the incurrence of fatal secondary malignancies is estimated. The difference in neutron production between 18 MV Varian and Siemens accelerators is estimated using Monte Carlo results. The neutron production from the Siemens accelerator is found to be approximately 4 times less than that of the Varian accelerator resulting in a risk of fatal secondary malignancy occurrence of approximately 1.6% when using the SMLC delivery technique and our measured modulation scaling factors. This compares with a previously published value of 1.6% for routine 3D CRT delivery on the Varian accelerator. PACS number(s): 87.52.Ga, 87.52.Px, 87.53.Qc, 87.53.Wz PMID:12841794
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SU-E-T-98: An Analysis of TG-51 Electron Beam Calibration Correction Factor Uncertainty
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lee, P; Alvarez, P; Taylor, P
Purpose: To analyze the uncertainty of the TG-51 electron beam calibration correction factors for farmer type ion chambers currently used by institutions visited by IROC Houston. Methods: TG-51 calibration data were collected from 181 institutions visited by IROC Houston physicists for 1174 and 197 distinct electron beams from modern Varian and Elekta accelerators, respectively. Data collected and analyzed included ion chamber make and model, nominal energy, N{sub D,w}, I{sub 50}, R{sub 50}, k’R{sub 50}, d{sub ref}, P{sub gr} and pdd(d{sub ref}). k’R{sub 50} data for parallel plate chambers were excluded from the analysis. Results: Unlike photon beams, electron nominal energymore » is a poor indicator of the actual energy as evidenced by the range of R{sub 50} values for each electron beam energy (6–22MeV). The large range in R{sub 50} values resulted k’R{sub 50} values with a small standard deviation but large range between maximum value used and minimum value (0.001–0.029) used for a specific Varian nominal energy. Varian data showed more variability in k’R{sub 50} values than the Elekta data (0.001–0.014). Using the observed range of R{sub 50} values, the maximum spread in k’R{sub 50} values was determined by IROC Houston and compared to the spread of k’R{sub 50} values used in the community. For Elekta linacs the spreads were equivalent, but for Varian energies of 6 to 16MeV, the community spread was 2 to 6 times larger. Community P{sub gr} values had a much larger range of values for 6 and 9 MeV values than predicted. The range in Varian pdd(d{sub ref} ) used by the community for low energies was large, (1.4–4.9 percent), when it should have been very close to unity. Exradin, PTW Roos and PTW farmer chambers N{sub D,w} values showed the largest spread, ≥11 percent. Conclusion: While the vast majority of electron beam calibration correction factors used are accurate, there is a surprising spread in some of the values used.« less
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Electron-emission characteristics of tungsten alloys: Mee 492. [No data; plasma anode tube
DOE Office of Scientific and Technical Information (OSTI.GOV)
Moon, H.M.
A plasma-anode tube was constructed to investigate the electron-emission characteristics for rhenium, 1% thorium tungsten, and 2% thorium tungsten. The tube consists of cathode, anode, cesium reservoir, and three probes. Inside of tube is a rough vacuum by using a Varian liquid-nitrogen-cooled cryovalve and further vacuum by using a Varian absorption pumpt to 4 X IO/sup -5/ pa. The tube was sealed off from the vacuum pump after the cesium ampoule was broken. The entire plasma-anode tube except the cesiunm reservoir was placed in a Blue M Electric Company furnace whose door had been modified to permit viewing of themore » tube.« less
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Biró, L. P.; Kertész, K.; Horváth, E.; Márk, G. I.; Molnár, G.; Vértesy, Z.; Tsai, J.-F.; Kun, A.; Bálint, Zs.; Vigneron, J. P.
2010-01-01
An unusual, intercalated photonic nanoarchitecture was discovered in the elytra of Taiwanese Trigonophorus rothschildi varians beetles. It consists of a multilayer structure intercalated with a random distribution of cylindrical holes normal to the plane of the multilayer. The nanoarchitectures were characterized structurally by scanning electron microscopy and optically by normal incidence, integrated and goniometric reflectance measurements. They exhibit an unsaturated specular and saturated non-specular component of the reflected light. Bioinspired, artificial nanoarchitectures of similar structure and with similar properties were realized by drilling holes of submicron size in a multilayer structure, showing that such photonic nanoarchitectures of biological origin may constitute valuable blueprints for artificial photonic materials. PMID:19933221
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Grilo, T F; Cardoso, P G; Pato, P; Duarte, A C; Pardal, M A
2014-03-01
A medium-term mesocosm exposure study was conducted to elucidate bioaccumulation and depuration of polychlorinated biphenyl congener 153 (PCB-153) in edible shrimp Palaemonetes varians. Over the 15-day exposure period, shrimp under different exposure concentrations exhibited a significant increase in PCB-153 concentration compared with control organisms. Distinct bioaccumulation patterns and uptake rates were observed depending on the exposure concentrations. For low PCB-153 exposure levels (0.25μgL(-1)), accumulation followed a saturation model, reaching an apparent steady state after fifteen days exposure. For intermediate (2.5μgL(-1)) and high PCB-153 levels (25μgL(-1)), accumulation was faster and linear. In addition, the bioaccumulation rate was not proportional to PCB-153 concentration, and the bioaccumulation was higher at intermediate exposure concentrations. Regarding the depuration phase, P. varians lost up to 30% of PCB-153 after 72h and levels continued slowly to decrease until the end of the 30-d experimental period. However, PCB-153 levels in shrimp did not reach background values, and those exposed to moderate and high PCB-153 concentrations presented contamination levels much higher than the regulatory limit for human food consumption (75ngg(-1) ww for Σ6 PCB). Copyright © 2013 Elsevier Inc. All rights reserved.
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Evaluation of imaging quality for flat-panel detector based low dose C-arm CT system
DOE Office of Scientific and Technical Information (OSTI.GOV)
Seo, Chang-Woo; Cha, Bo Kyung; Jeon, Sungchae
The image quality associated with the extent of the angle of gantry rotation, the number of projection views, and the dose of X-ray radiation was investigated in flat-panel detector (FPD) based C-arm cone-beam computed tomography (CBCT) system for medical applications. A prototype CBCT system for the projection acquisition used the X-ray tube (A-132, Varian inc.) having rhenium-tungsten molybdenum target and flat panel a-Si X-ray detector (PaxScan 4030CB, Varian inc.) having a 397 x 298 mm active area with 388 μm pixel pitch and 1024 x 768 pixels in 2 by 2 binning mode. The performance comparison of X-ray imaging qualitymore » was carried out using the Feldkamp, Davis, and Kress (FDK) reconstruction algorithm between different conditions of projection acquisition. In this work, head-and-dental (75 kVp/20 mA) and chest (90 kVp/25 mA) phantoms were used to evaluate the image quality. The 361 (30 fps x 12 s) projection data during 360 deg. gantry rotation with 1 deg. interval for the 3D reconstruction were acquired. Parke weighting function were applied to handle redundant data and improve the reconstructed image quality in a mobile C-arm system with limited rotation angles. The reconstructed 3D images were investigated for comparison of qualitative image quality in terms of scan protocols (projection views, rotation angles and exposure dose). Furthermore, the performance evaluation in image quality will be investigated regarding X-ray dose and limited projection data for a FPD based mobile C-arm CBCT system. (authors)« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Panfil, J; Patel, R; Surucu, M
Purpose: To compare markerless template-based tracking of lung tumors using dual energy (DE) cone-beam computed tomography (CBCT) projections versus single energy (SE) CBCT projections. Methods: A RANDO chest phantom with a simulated tumor in the upper right lung was used to investigate the effectiveness of tumor tracking using DE and SE CBCT projections. Planar kV projections from CBCT acquisitions were captured at 60 kVp (4 mAs) and 120 kVp (1 mAs) using the Varian TrueBeam and non-commercial iTools Capture software. Projections were taken at approximately every 0.53° while the gantry rotated. Due to limitations of the phantom, angles for whichmore » the shoulders blocked the tumor were excluded from tracking analysis. DE images were constructed using a weighted logarithmic subtraction that removed bony anatomy while preserving soft tissue structures. The tumors were tracked separately on DE and SE (120 kVp) images using a template-based tracking algorithm. The tracking results were compared to ground truth coordinates designated by a physician. Matches with a distance of greater than 3 mm from ground truth were designated as failing to track. Results: 363 frames were analyzed. The algorithm successfully tracked the tumor on 89.8% (326/363) of DE frames compared to 54.3% (197/363) of SE frames (p<0.0001). Average distance between tracking and ground truth coordinates was 1.27 +/− 0.67 mm for DE versus 1.83+/−0.74 mm for SE (p<0.0001). Conclusion: This study demonstrates the effectiveness of markerless template-based tracking using DE CBCT. DE imaging resulted in better detectability with more accurate localization on average versus SE. Supported by a grant from Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Deshpande, S; Dhote, D; Kumar, R
Purpose: To measure actual patient eye lens dose for different cone beam computed tomography (CBCT) acquisition protocol of Varian’s On Board Imagining (OBI) system using Optically Stimulated Luminescence (OSL) dosimeter and study the eye lens dose with patient geometry and distance of isocenter to the eye lens Methods: OSL dosimeter was used to measure eye lens dose of patient. OSL dosimeter was placed on patient forehead center during CBCT image acquisition to measure eye lens dose. For three different cone beam acquisition protocol (standard dose head, low dose head and high quality head) of Varian On-Board Imaging, eye lens dosesmore » were measured. Measured doses were correlated with patient geometry and distance between isocenter to eye lens. Results: Measured eye lens dose for standard dose head was in the range of 1.8 mGy to 3.2 mGy, for high quality head protocol dose was in range of 4.5mGy to 9.9 mGy whereas for low dose head was in the range of 0.3mGy to 0.7mGy. Dose to eye lens is depends upon position of isocenter. For posterioraly located tumor eye lens dose is less. Conclusion: From measured doses it can be concluded that by proper selection of imagining protocol and frequency of imaging, it is possible to restrict the eye lens dose below the new limit set by ICRP. However, undoubted advantages of imaging system should be counter balanced by careful consideration of imaging protocol especially for very intense imaging sequences for Adoptive Radiotherapy or IMRT.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Calvo Ortega, Juan Francisco, E-mail: jfcdrr@yahoo.es; Moragues, Sandra; Pozo, Miquel
2014-07-01
The aim of this study is to assess the accuracy of a convolution-based algorithm (anisotropic analytical algorithm [AAA]) implemented in the Eclipse planning system for intensity-modulated radiosurgery (IMRS) planning of small cranial targets by using a 5-mm leaf-width multileaf collimator (MLC). Overall, 24 patient-based IMRS plans for cranial lesions of variable size (0.3 to 15.1 cc) were planned (Eclipse, AAA, version 10.0.28) using fixed field-based IMRS produced by a Varian linear accelerator equipped with a 120 MLC (5-mm width on central leaves). Plan accuracy was evaluated according to phantom-based measurements performed with radiochromic film (EBT2, ISP, Wayne, NJ). Film 2Dmore » dose distributions were performed with the FilmQA Pro software (version 2011, Ashland, OH) by using the triple-channel dosimetry method. Comparison between computed and measured 2D dose distributions was performed using the gamma method (3%/1 mm). Performance of the MLC was checked by inspection of the DynaLog files created by the linear accelerator during the delivery of each dynamic field. The absolute difference between the calculated and measured isocenter doses for all the IMRS plans was 2.5% ± 2.1%. The gamma evaluation method resulted in high average passing rates of 98.9% ± 1.4% (red channel) and 98.9% ± 1.5% (blue and green channels). DynaLog file analysis revealed a maximum root mean square error of 0.46 mm. According to our results, we conclude that the Eclipse/AAA algorithm provides accurate cranial IMRS dose distributions that may be accurately delivered by a Varian linac equipped with a Millennium 120 MLC.« less
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SU-D-BRD-01: An Automated Physics Weekly Chart Checking System Supporting ARIA
DOE Office of Scientific and Technical Information (OSTI.GOV)
Chang, X; Yang, D
Purpose: A software tool was developed in this study to perform automatic weekly physics chart check on the patient data in ARIA. The tool accesses the electronic patient data directly from ARIA server and checks the accuracy of treatment deliveries, and generates reports which summarize the delivery history and highlight the errors. Methods: The tool has four modules. 1) The database interface is designed to directly access treatment delivery data from the ARIA database before reorganizing the data into the patient chart tree (PCT). 2) PCT is a core data structure designed to store and organize the data in logicalmore » hierarchies, and to be passed among functions. 3) The treatment data check module analyzes the organized data in PCT and stores the checking results into PCT. 4) Report generation module generates reports containing the treatment delivery summary, chart checking results and plots of daily treatment setup parameters (couch table positions, shifts of image guidance). The errors that are found by the tool are highlighted with colors. Results: The weekly check tool has been implemented in MATLAB and clinically tested at two major cancer centers. Javascript, cascading style sheets (CSS) and dynamic HTML were employed to create the user-interactive reports. It takes 0.06 second to search the delivery records of one beam with PCT and compare the delivery records with beam plan. The reports, saved in the HTML files on shared network folder, can be accessed by web browser on computers and mobile devices. Conclusion: The presented weekly check tool is useful to check the electronic patient treatment data in Varian ARIA system. It could be more efficient and reliable than the manually check by physicists. The work was partially supported by a research grant from Varian Medical System.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, H; Wang, W; Hu, W
2014-06-01
Purpose: To quantify setup errors by pretreatment kilovolt cone-beam computed tomography(KV-CBCT) scans for middle or distal esophageal carcinoma patients. Methods: Fifty-two consecutive middle or distal esophageal carcinoma patients who underwent IMRT were included this study. A planning CT scan using a big-bore CT simulator was performed in the treatment position and was used as the reference scan for image registration with CBCT. CBCT scans(On-Board Imaging v1. 5 system, Varian Medical Systems) were acquired daily during the first treatment week. A total of 260 CBCT scans was assessed with a registration clip box defined around the PTV-thorax in the reference scanmore » based on(nine CBCTs per patient) bony anatomy using Offline Review software v10.0(Varian Medical Systems). The anterior-posterior(AP), left-right(LR), superiorinferior( SI) corrections were recorded. The systematic and random errors were calculated. The CTV-to-PTV margins in each CBCT frequency was based on the Van Herk formula (2.5Σ+0.7σ). Results: The SD of systematic error (Σ) was 2.0mm, 2.3mm, 3.8mm in the AP, LR and SI directions, respectively. The average random error (σ) was 1.6mm, 2.4mm, 4.1mm in the AP, LR and SI directions, respectively. The CTV-to-PTV safety margin was 6.1mm, 7.5mm, 12.3mm in the AP, LR and SI directions based on van Herk formula. Conclusion: Our data recommend the use of 6 mm, 8mm, and 12 mm for esophageal carcinoma patient setup in AP, LR, SI directions, respectively.« less
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Chao, Ming; Wei, Jie; Li, Tianfang; Yuan, Yading; Rosenzweig, Kenneth E; Lo, Yeh-Chi
2017-01-01
We present a study of extracting respiratory signals from cone beam computed tomography (CBCT) projections within the framework of the Amsterdam Shroud (AS) technique. Acquired prior to the radiotherapy treatment, CBCT projections were preprocessed for contrast enhancement by converting the original intensity images to attenuation images with which the AS image was created. An adaptive robust z-normalization filtering was applied to further augment the weak oscillating structures locally. From the enhanced AS image, the respiratory signal was extracted using a two-step optimization approach to effectively reveal the large-scale regularity of the breathing signals. CBCT projection images from five patients acquired with the Varian Onboard Imager on the Clinac iX System Linear Accelerator (Varian Medical Systems, Palo Alto, CA) were employed to assess the proposed technique. Stable breathing signals can be reliably extracted using the proposed algorithm. Reference waveforms obtained using an air bellows belt (Philips Medical Systems, Cleveland, OH) were exported and compared to those with the AS based signals. The average errors for the enrolled patients between the estimated breath per minute (bpm) and the reference waveform bpm can be as low as −0.07 with the standard deviation 1.58. The new algorithm outperformed the original AS technique for all patients by 8.5% to 30%. The impact of gantry rotation on the breathing signal was assessed with data acquired with a Quasar phantom (Modus Medical Devices Inc., London, Canada) and found to be minimal on the signal frequency. The new technique developed in this work will provide a practical solution to rendering markerless breathing signal using the CBCT projections for thoracic and abdominal patients. PMID:27008349
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mancosu, Pietro; Fogliata, Antonella, E-mail: Antonella.Fogliata@humanitas.it; Stravato, Antonella
2016-07-01
Frameless stereotactic radiosurgery (SRS) requires dedicated systems to monitor the patient position during the treatment to avoid target underdosage due to involuntary shift. The optical surface monitoring system (OSMS) is here evaluated in a phantom-based study. The new EDGE linear accelerator from Varian (Varian, Palo Alto, CA) integrates, for cranial lesions, the common cone beam computed tomography (CBCT) and kV-MV portal images to the optical surface monitoring system (OSMS), a device able to detect real-time patient's face movements in all 6 couch axes (vertical, longitudinal, lateral, rotation along the vertical axis, pitch, and roll). We have evaluated the OSMS imagingmore » capability in checking the phantoms' position and monitoring its motion. With this aim, a home-made cranial phantom was developed to evaluate the OSMS accuracy in 4 different experiments: (1) comparison with CBCT in isocenter location, (2) capability to recognize predefined shifts up to 2° or 3 cm, (3) evaluation at different couch angles, (4) ability to properly reconstruct the surface when the linac gantry visually block one of the cameras. The OSMS system showed, with a phantom, to be accurate for positioning in respect to the CBCT imaging system with differences of 0.6 ± 0.3 mm for linear vector displacement, with a maximum rotational inaccuracy of 0.3°. OSMS presented an accuracy of 0.3 mm for displacement up to 1 cm and 1°, and 0.5 mm for larger displacements. Different couch angles (45° and 90°) induced a mean vector uncertainty < 0.4 mm. Coverage of 1 camera produced an uncertainty < 0.5 mm. Translations and rotations of a phantom can be accurately detect with the optical surface detector system.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Tateoka, K; Graduate School of Medicine, Sapporo Medical University, Sapporo, JP; Fujimomo, K
2014-06-01
Purpose: The aim of the study is to evaluate the use of Varian DynaLog files to verify VMAT plans delivery and modulation complexity score (MCS) of VMAT. Methods: Delivery accuracy of machine performance was quantified by multileaf collimator (MLC) position errors, gantry angle errors and fluence delivery accuracy for volumetric modulated arc therapy (VMAT). The relationship between machine performance and plan complexity were also investigated using the modulation complexity score (MCS). Plan and Actual MLC positions, gantry angles and delivered fraction of monitor units were extracted from Varian DynaLog files. These factors were taken from the record and verify systemmore » of MLC control file. Planned and delivered beam data were compared to determine leaf position errors and gantry angle errors. Analysis was also performed on planned and actual fluence maps reconstructed from those of the DynaLog files. This analysis was performed for all treatment fractions of 5 prostate VMAT plans. The analysis of DynaLog files have been carried out by in-house programming in Visual C++. Results: The root mean square of leaf position and gantry angle errors were about 0.12 and 0.15, respectively. The Gamma of planned and actual fluence maps at 3%/3 mm criterion was about 99.21. The gamma of the leaf position errors were not directly related to plan complexity as determined by the MCS. Therefore, the gamma of the gantry angle errors were directly related to plan complexity as determined by the MCS. Conclusion: This study shows Varian dynalog files for VMAT plan can be diagnosed delivery errors not possible with phantom based quality assurance. Furthermore, the MCS of VMAT plan can evaluate delivery accuracy for patients receiving of VMAT. Machine performance was found to be directly related to plan complexity but this is not the dominant determinant of delivery accuracy.« less
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On flattening filter‐free portal dosimetry
Novais, Juan Castro; Molina López, María Yolanda; Maqueda, Sheila Ruiz
2016-01-01
Varian introduced (in 2010) the option of removing the flattening filter (FF) in their C‐Arm linacs for intensity‐modulated treatments. This mode, called flattening filter‐free (FFF), offers the advantage of a greater dose rate. Varian's “Portal Dosimetry” is an electronic portal imager device (EPID)‐based tool for IMRT verification. This tool lacks the capability of verifying flattening filter‐free (FFF) modes due to saturation and lack of an image prediction algorithm. (Note: the latest versions of this software and EPID correct these issues.) The objective of the present study is to research the feasibility of said verifications (with the older versions of the software and EPID). By placing the EPID at a greater distance, the images can be acquired without saturation, yielding a linearity similar to the flattened mode. For the image prediction, a method was optimized based on the clinically used algorithm (analytical anisotropic algorithm (AAA)) over a homogeneous phantom. The depth inside the phantom and its electronic density were tailored. An application was developed to allow the conversion of a dose plane (in DICOM format) to Varian's custom format for Portal Dosimetry. The proposed method was used for the verification of test and clinical fields for the three qualities used in our institution for IMRT: 6X, 6FFF and 10FFF. The method developed yielded a positive verification (more than 95% of the points pass a 2%/2 mm gamma) for both the clinical and test fields. This method was also capable of “predicting” static and wedged fields. A workflow for the verification of FFF fields was developed. This method relies on the clinical algorithm used for dose calculation and is able to verify the FFF modes, as well as being useful for machine quality assurance. The procedure described does not require new hardware. This method could be used as a verification of Varian's Portal Dose Image Prediction. PACS number(s): 87.53.Kn, 87.55.T‐, 87.56.bd, 87.59.‐e PMID:27455487
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WE-E-BRB-02: Implementation of Pencil Beam Scanning (PBS) Proton Therapy Treatment for Liver Patient
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lin, L.
Strategies for treating thoracic and liver tumors using pencil beam scanning proton therapy Thoracic and liver tumors have not been treated with pencil beam scanning (PBS) proton therapy until recently. This is because of concerns about the significant interplay effects between proton spot scanning and patient’s respiratory motion. However, not all tumors have unacceptable magnitude of motion for PBS proton therapy. Therefore it is important to analyze the motion and understand the significance of the interplay effect for each patient. The factors that affect interplay effect and its washout include magnitude of motion, spot size, spot scanning sequence and speed.more » Selection of beam angle, scanning direction, repainting and fractionation can all reduce the interplay effect. An overview of respiratory motion management in PBS proton therapy including assessment of tumor motion and WET evaluation will be first presented. As thoracic tumors have very different motion patterns from liver tumors, examples would be provided for both anatomic sites. As thoracic tumors are typically located within highly heterogeneous environments, dose calculation accuracy is a concern for both treatment target and surrounding organs such as spinal cord or esophagus. Strategies for mitigating the interplay effect in PBS will be presented and the pros and cons of various motion mitigation strategies will be discussed. Learning Objectives: Motion analysis for individual patients with respect to interplay effect Interplay effect and mitigation strategies for treating thoracic/liver tumors with PBS Treatment planning margins for PBS The impact of proton dose calculation engines over heterogeneous treatment target and surrounding organs I have a current research funding from Varian Medical System under the master agreement between University of Pennsylvania and Varian; L. Lin, I have a current funding from Varian Medical System under the master agreement between University of Pennsylvania and Varian.; H. Li, Na.« less
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WE-E-BRB-01: Personalized Motion Management Strategies for Pencil Beam Scanning Proton Therapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhu, X.
Strategies for treating thoracic and liver tumors using pencil beam scanning proton therapy Thoracic and liver tumors have not been treated with pencil beam scanning (PBS) proton therapy until recently. This is because of concerns about the significant interplay effects between proton spot scanning and patient’s respiratory motion. However, not all tumors have unacceptable magnitude of motion for PBS proton therapy. Therefore it is important to analyze the motion and understand the significance of the interplay effect for each patient. The factors that affect interplay effect and its washout include magnitude of motion, spot size, spot scanning sequence and speed.more » Selection of beam angle, scanning direction, repainting and fractionation can all reduce the interplay effect. An overview of respiratory motion management in PBS proton therapy including assessment of tumor motion and WET evaluation will be first presented. As thoracic tumors have very different motion patterns from liver tumors, examples would be provided for both anatomic sites. As thoracic tumors are typically located within highly heterogeneous environments, dose calculation accuracy is a concern for both treatment target and surrounding organs such as spinal cord or esophagus. Strategies for mitigating the interplay effect in PBS will be presented and the pros and cons of various motion mitigation strategies will be discussed. Learning Objectives: Motion analysis for individual patients with respect to interplay effect Interplay effect and mitigation strategies for treating thoracic/liver tumors with PBS Treatment planning margins for PBS The impact of proton dose calculation engines over heterogeneous treatment target and surrounding organs I have a current research funding from Varian Medical System under the master agreement between University of Pennsylvania and Varian; L. Lin, I have a current funding from Varian Medical System under the master agreement between University of Pennsylvania and Varian.; H. Li, Na.« less
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WE-E-BRB-00: Motion Management for Pencil Beam Scanning Proton Therapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
NONE
Strategies for treating thoracic and liver tumors using pencil beam scanning proton therapy Thoracic and liver tumors have not been treated with pencil beam scanning (PBS) proton therapy until recently. This is because of concerns about the significant interplay effects between proton spot scanning and patient’s respiratory motion. However, not all tumors have unacceptable magnitude of motion for PBS proton therapy. Therefore it is important to analyze the motion and understand the significance of the interplay effect for each patient. The factors that affect interplay effect and its washout include magnitude of motion, spot size, spot scanning sequence and speed.more » Selection of beam angle, scanning direction, repainting and fractionation can all reduce the interplay effect. An overview of respiratory motion management in PBS proton therapy including assessment of tumor motion and WET evaluation will be first presented. As thoracic tumors have very different motion patterns from liver tumors, examples would be provided for both anatomic sites. As thoracic tumors are typically located within highly heterogeneous environments, dose calculation accuracy is a concern for both treatment target and surrounding organs such as spinal cord or esophagus. Strategies for mitigating the interplay effect in PBS will be presented and the pros and cons of various motion mitigation strategies will be discussed. Learning Objectives: Motion analysis for individual patients with respect to interplay effect Interplay effect and mitigation strategies for treating thoracic/liver tumors with PBS Treatment planning margins for PBS The impact of proton dose calculation engines over heterogeneous treatment target and surrounding organs I have a current research funding from Varian Medical System under the master agreement between University of Pennsylvania and Varian; L. Lin, I have a current funding from Varian Medical System under the master agreement between University of Pennsylvania and Varian.; H. Li, Na.« less
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WE-E-BRB-03: Implementation of PBS Proton Therapy Treatment for Free Breathing Lung Cancer Patients
DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, H.
Strategies for treating thoracic and liver tumors using pencil beam scanning proton therapy Thoracic and liver tumors have not been treated with pencil beam scanning (PBS) proton therapy until recently. This is because of concerns about the significant interplay effects between proton spot scanning and patient’s respiratory motion. However, not all tumors have unacceptable magnitude of motion for PBS proton therapy. Therefore it is important to analyze the motion and understand the significance of the interplay effect for each patient. The factors that affect interplay effect and its washout include magnitude of motion, spot size, spot scanning sequence and speed.more » Selection of beam angle, scanning direction, repainting and fractionation can all reduce the interplay effect. An overview of respiratory motion management in PBS proton therapy including assessment of tumor motion and WET evaluation will be first presented. As thoracic tumors have very different motion patterns from liver tumors, examples would be provided for both anatomic sites. As thoracic tumors are typically located within highly heterogeneous environments, dose calculation accuracy is a concern for both treatment target and surrounding organs such as spinal cord or esophagus. Strategies for mitigating the interplay effect in PBS will be presented and the pros and cons of various motion mitigation strategies will be discussed. Learning Objectives: Motion analysis for individual patients with respect to interplay effect Interplay effect and mitigation strategies for treating thoracic/liver tumors with PBS Treatment planning margins for PBS The impact of proton dose calculation engines over heterogeneous treatment target and surrounding organs I have a current research funding from Varian Medical System under the master agreement between University of Pennsylvania and Varian; L. Lin, I have a current funding from Varian Medical System under the master agreement between University of Pennsylvania and Varian.; H. Li, Na.« less
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SU-F-T-424: Mitigation of Increased Surface Dose When Treating Through A Carbon Fiber Couch Top
DOE Office of Scientific and Technical Information (OSTI.GOV)
Johnson, E; Misgina, F
Purpose: To study the effect of the Varian carbon fiber couch top on surface dose for patients being treated using single PA beams in the supine position and to identify simple methods for surface dose reduction. Methods: Measurements of surface dose were obtained in Solid Water phantoms using both a parallel plate ionization chamber (PTW Advanced Markus) and EBT2 Radiochromic films for both 6 and 10MV photons. All measurements were referenced to a depth considered a typical for PA Spine fields. Techniques used to reduce the surface dose included introducing an air standoff using Styrofoam sheets to suspend the phantommore » surface above the couch top and by adding a thin high Z scattering foil on the table surface. Surface doses were evaluated for typical field sizes, standoff heights, and various scattering materials. Comparisons were made to the surface dose obtainable when treating through a Varian Mylar covered tennis racket style couch top. Results: Dependence on typical spine field sizes was relatively minor. Dependence on air gap was much more significant. Surface doses decreased exponentially with increases in air standoff distance. Surface doses were reduced by approximately 50% for an air gap of 10cm and 40% for a 15cm air gap. Surface doses were reduced by an additional 15% by the addition of a 1mm Tin scattering foil. Conclusion: Using simple techniques, it is possible to reduce the surface dose when treating single PA fields through the Varian carbon fiber couch top. Surface doses can be reduced to levels observed when treating though transparent Mylar tops by adding about 15 cm of air gap. Further reductions are possible by adding thin scattering foils, such as Tin or Lead, on the couch surface. This is a low cost approach to reduce surface dose when using the Varian carbon fiber couch top.« less
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Oliphant, Andrew; Hauton, Chris; Thatje, Sven
2013-01-01
Variations in larval instar number are common among arthropods. Here, we assess the implications of temperature-mediated variations in larval instar number for larval development time, larval growth rates, and juvenile dry weight within the palaemonid shrimp, Palaemonetes varians. In contrast with previous literature, which focuses on terrestrial arthropods, particularly model and pest species often of laboratory lines, we use wild shrimp, which differ in their life history from previous models. Newly-hatched P. varians larvae were first reared at 5, 10, 17, 25, and 30°C to assess their thermal scope for development. Larvae developed at 17, 25, and 30°C. At higher temperatures, larvae developed through fewer larval instars. Two dominant developmental pathways were observed; a short pathway of four instars and a long pathway of five instars. Longer developmental pathways of six to seven instars were rarely observed (mostly at lower temperatures) and consisted of additional instars as ‘repeat’ instars; i.e. little developmental advance over the preceding instar. To assess the implications of temperature-mediated variation in larval instar number, newly-hatched larvae were then reared at 15, 20, and 25°C. Again, the proportion of larvae developing through four instars increased with temperature. At all temperatures, larval development time and juvenile dry weight were greater for larvae developing through five instars. Importantly, because of the increasing proportion of larvae developing through four instars with increasing temperature, larval traits associated with this pathway (reduced development time and juvenile dry weight) became more dominant. As a consequence of increasing growth rate with temperature, and the shift in the proportion of larvae developing through four instars, juvenile dry weight was greatest at intermediate temperatures (20°C). We conclude that at settlement P. varians juveniles do not follow the temperature-size rule; this is of importance for life-history ecology in response to environmental change, as well as for aquaculture applications. PMID:24069450
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Oliphant, Andrew; Hauton, Chris; Thatje, Sven
2013-01-01
Variations in larval instar number are common among arthropods. Here, we assess the implications of temperature-mediated variations in larval instar number for larval development time, larval growth rates, and juvenile dry weight within the palaemonid shrimp, Palaemonetes varians. In contrast with previous literature, which focuses on terrestrial arthropods, particularly model and pest species often of laboratory lines, we use wild shrimp, which differ in their life history from previous models. Newly-hatched P. varians larvae were first reared at 5, 10, 17, 25, and 30 °C to assess their thermal scope for development. Larvae developed at 17, 25, and 30 °C. At higher temperatures, larvae developed through fewer larval instars. Two dominant developmental pathways were observed; a short pathway of four instars and a long pathway of five instars. Longer developmental pathways of six to seven instars were rarely observed (mostly at lower temperatures) and consisted of additional instars as 'repeat' instars; i.e. little developmental advance over the preceding instar. To assess the implications of temperature-mediated variation in larval instar number, newly-hatched larvae were then reared at 15, 20, and 25 °C. Again, the proportion of larvae developing through four instars increased with temperature. At all temperatures, larval development time and juvenile dry weight were greater for larvae developing through five instars. Importantly, because of the increasing proportion of larvae developing through four instars with increasing temperature, larval traits associated with this pathway (reduced development time and juvenile dry weight) became more dominant. As a consequence of increasing growth rate with temperature, and the shift in the proportion of larvae developing through four instars, juvenile dry weight was greatest at intermediate temperatures (20 °C). We conclude that at settlement P. varians juveniles do not follow the temperature-size rule; this is of importance for life-history ecology in response to environmental change, as well as for aquaculture applications.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ding, G
Purpose: Commissioning radiation beams requires considerable effort to obtain the beam data for beam configuration in a commercial treatment planning system. With the advances in technology, the manufacturer of accelerators now has the ability to adjust radiation beam parameters to meet pre-determined specifications with high precision. This study aims to illustrate the feasibility of making pre-configured radiation beams available in commercial treatment planning systems. Methods: In recent years, Varian has made a set of measured beam data from the TrueBeam accelerator available to users. Although the beam data are provided as “suggestive data” without warranty, the commissioned data measured bymore » users have been shown to be in excellent agreement with the data set provided when the beams from the installed Linacs were adjusted to meet the beam specifications. An unofficial survey among Varian Linac TrueBeam users shows that the suggestive data set has been used with validation by users in some clinics. This indicates that radiation beams from a specified Linac can be standardized and pre-configured in a treatment planning system. Results: Two newly installed Varian TrueBeam accelerators at two different centers were examined in which one set of commissioned beam data was obtained from measurements performed by an independent physics consulting company and the other was measured by local physicists in the department. All beams from both accelerators were tuned to meet the manufacturer’s specifications. Discrepancies of less than 1% were found between the commissioned beam data from both accelerators and the suggestive data set provided by Varian. Conclusion: It may be feasible that radiation beams can be pre-configured in commercial treatment planning systems. The radiation beam users will perform the beam validation and end-to-end tests instead of configuring beams. This framework can increase both the efficiency and the accuracy in commercial radiation treatment planning systems.« less
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NASA Astrophysics Data System (ADS)
Jakobsen, Hans J.; Bildsøe, Henrik; Gan, Zhehong; Brey, William W.
2011-08-01
The acquisition and different appearances observed for wide bandwidth solid-state MAS NMR spectra of low-γ nuclei, using 14N as an illustrative nucleus and employing two different commercial spectrometers (Varian, 14.1 T and Bruker, 19.6 T), have been compared/evaluated and optimized from an experimental NMR and an electronic engineering point of view, to account for the huge differences in these spectra. The large differences in their spectral appearances, employing the recommended/standard experimental set-up for the two different spectrometers, are shown to be associated with quite large differences in the electronic design of the two types of preamplifiers, which are connected to their respective probes through a 50 Ω cable, and are here completely accounted for. This has led to different opportunities for optimum performances in the acquisition of nearly ideal wide bandwidth spectra for low-γ nuclei on the two spectrometers by careful evaluation of the length for the 50 Ω probe-to-preamp cable for the Varian system and appropriate changes to the bandwidth ( Q) of the NMR probe used on the Bruker spectrometer. Earlier, we reported quite distorted spectra obtained with Varian Unity INOVA spectrometers (at 11.4 and 14.1 T) in several exploratory wide bandwidth 14N MAS NMR studies of inorganic nitrates and amino acids. These spectra have now been compared/evaluated with fully analyzed 14N MAS spectra correspondingly acquired at 19.6 T on a Bruker spectrometer. It is shown that our upgraded version of the STARS simulation/iterative-fitting software is capable of providing identical sets for the molecular spectral parameters and corresponding fits to the experimental spectra, which fully agree with the electronic measurements, despite the highly different appearances for the MAS NMR spectra acquired on the Varian and Bruker spectrometers.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Rafat, M; Bazalova, M; Palma, B
Purpose: To characterize the effect of very rapid dose delivery as compared to conventional therapeutic irradiation times on clonogenic cell survival. Methods: We used a Varian Trilogy linear accelerator to deliver doses up to 10 Gy using a 6 MV SRS photon beam. We irradiated four cancer cell lines in times ranging from 30 sec to 30 min. We also used a Varian TrueBeam linear accelerator to deliver 9 MeV electrons at 10 Gy in 10 s to 30 min to determine the effect of irradiation time on cell survival. We then evaluated the effect of using 60 and 120more » MeV electrons on cell survival using the Next Linear Collider Test Accelerator (NLCTA) beam line at the SLAC National Accelerator Laboratory. During irradiation, adherent cells were maintained at 37oC with 20%O2/5%CO2. Clonogenic assays were completed following irradiation to determine changes in cell survival due to dose delivery time and beam quality, and the survival data were fitted with the linear-quadratic model. Results: Cell lines varied in radiosensitivity, ranging from two to four logs of cell kill at 10 Gy for both conventional and very rapid irradiation. Delivering radiation in shorter times decreased survival in all cell lines. Log differences in cell kill ranged from 0.2 to 0.7 at 10 Gy for the short compared to the long irradiation time. Cell kill differences between short and long irradiations were more pronounced as doses increased for all cell lines. Conclusion: Our findings suggest that shortening delivery of therapeutic radiation doses to less than 1 minute may improve tumor cell kill. This study demonstrates the potential advantage of technologies under development to deliver stereotactic ablative radiation doses very rapidly. Bill Loo and Peter Maxim have received Honoraria from Varian and Research Support from Varian and RaySearch.« less
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Guerreiro, António; Soares, Ana; Piletska, Elena; Mattiasson, Bo; Piletsky, Sergey
2008-03-31
Molecularly imprinted (MIP) and blank polymers with affinity for nonylphenol were designed using computational modelling. Chromatographic tests demonstrated higher affinity of imprinted polymers towards the template nonylphenol as compared with blank polymers. The performance of both polymers in solid-phase extraction was however very similar. Both blank and imprinted polymers appeared to be suitable for the removal and pre-concentration of nonylphenol from contaminated water samples with 99% efficiency of the recovery. The commercial resins PH(EC) (Biotage) and C18 (Varian) tested in the same conditions used for comparative purposes had recovery rate <84%. The polymer capacity for nonylphenol was 231 mg g(-1) for blank and 228 mg g(-1) for MIP. The synthesised materials can have significance for sample pre-concentration and environmental analysis of this class of compounds.
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Casey, Kevin E.; Alvarez, Paola; Kry, Stephen F.; Howell, Rebecca M.; Lawyer, Ann; Followill, David
2013-01-01
Purpose: The aim of this work was to create a mailable phantom with measurement accuracy suitable for Radiological Physics Center (RPC) audits of high dose-rate (HDR) brachytherapy sources at institutions participating in National Cancer Institute-funded cooperative clinical trials. Optically stimulated luminescence dosimeters (OSLDs) were chosen as the dosimeter to be used with the phantom. Methods: The authors designed and built an 8 × 8 × 10 cm3 prototype phantom that had two slots capable of holding Al2O3:C OSLDs (nanoDots; Landauer, Glenwood, IL) and a single channel capable of accepting all 192Ir HDR brachytherapy sources in current clinical use in the United States. The authors irradiated the phantom with Nucletron and Varian 192Ir HDR sources in order to determine correction factors for linearity with dose and the combined effects of irradiation energy and phantom characteristics. The phantom was then sent to eight institutions which volunteered to perform trial remote audits. Results: The linearity correction factor was kL = (−9.43 × 10−5 × dose) + 1.009, where dose is in cGy, which differed from that determined by the RPC for the same batch of dosimeters using 60Co irradiation. Separate block correction factors were determined for current versions of both Nucletron and Varian 192Ir HDR sources and these vendor-specific correction factors differed by almost 2.6%. For the Nucletron source, the correction factor was 1.026 [95% confidence interval (CI) = 1.023–1.028], and for the Varian source, it was 1.000 (95% CI = 0.995–1.005). Variations in lateral source positioning up to 0.8 mm and distal/proximal source positioning up to 10 mm had minimal effect on dose measurement accuracy. The overall dose measurement uncertainty of the system was estimated to be 2.4% and 2.5% for the Nucletron and Varian sources, respectively (95% CI). This uncertainty was sufficient to establish a ±5% acceptance criterion for source strength audits under a formal RPC audit program. Trial audits of four Nucletron sources and four Varian sources revealed an average RPC-to-institution dose ratio of 1.000 (standard deviation = 0.011). Conclusions: The authors have created an OSLD-based 192Ir HDR brachytherapy source remote audit tool which offers sufficient dose measurement accuracy to allow the RPC to establish a remote audit program with a ±5% acceptance criterion. The feasibility of the system has been demonstrated with eight trial audits to date. PMID:24320455
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Rodrigues, Anna; Yin, Fang-Fang; Wu, Qiuwen, E-mail: Qiuwen.Wu@Duke.edu
2015-05-15
Purpose: To develop a framework for accurate electron Monte Carlo dose calculation. In this study, comprehensive validations of vendor provided electron beam phase space files for Varian TrueBeam Linacs against measurement data are presented. Methods: In this framework, the Monte Carlo generated phase space files were provided by the vendor and used as input to the downstream plan-specific simulations including jaws, electron applicators, and water phantom computed in the EGSnrc environment. The phase space files were generated based on open field commissioning data. A subset of electron energies of 6, 9, 12, 16, and 20 MeV and open and collimatedmore » field sizes 3 × 3, 4 × 4, 5 × 5, 6 × 6, 10 × 10, 15 × 15, 20 × 20, and 25 × 25 cm{sup 2} were evaluated. Measurements acquired with a CC13 cylindrical ionization chamber and electron diode detector and simulations from this framework were compared for a water phantom geometry. The evaluation metrics include percent depth dose, orthogonal and diagonal profiles at depths R{sub 100}, R{sub 50}, R{sub p}, and R{sub p+} for standard and extended source-to-surface distances (SSD), as well as cone and cut-out output factors. Results: Agreement for the percent depth dose and orthogonal profiles between measurement and Monte Carlo was generally within 2% or 1 mm. The largest discrepancies were observed within depths of 5 mm from phantom surface. Differences in field size, penumbra, and flatness for the orthogonal profiles at depths R{sub 100}, R{sub 50}, and R{sub p} were within 1 mm, 1 mm, and 2%, respectively. Orthogonal profiles at SSDs of 100 and 120 cm showed the same level of agreement. Cone and cut-out output factors agreed well with maximum differences within 2.5% for 6 MeV and 1% for all other energies. Cone output factors at extended SSDs of 105, 110, 115, and 120 cm exhibited similar levels of agreement. Conclusions: We have presented a Monte Carlo simulation framework for electron beam dose calculations for Varian TrueBeam Linacs. Electron beam energies of 6 to 20 MeV for open and collimated field sizes from 3 × 3 to 25 × 25 cm{sup 2} were studied and results were compared to the measurement data with excellent agreement. Application of this framework can thus be used as the platform for treatment planning of dynamic electron arc radiotherapy and other advanced dynamic techniques with electron beams.« less
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Rodrigues, Anna; Sawkey, Daren; Yin, Fang-Fang; Wu, Qiuwen
2015-05-01
To develop a framework for accurate electron Monte Carlo dose calculation. In this study, comprehensive validations of vendor provided electron beam phase space files for Varian TrueBeam Linacs against measurement data are presented. In this framework, the Monte Carlo generated phase space files were provided by the vendor and used as input to the downstream plan-specific simulations including jaws, electron applicators, and water phantom computed in the EGSnrc environment. The phase space files were generated based on open field commissioning data. A subset of electron energies of 6, 9, 12, 16, and 20 MeV and open and collimated field sizes 3 × 3, 4 × 4, 5 × 5, 6 × 6, 10 × 10, 15 × 15, 20 × 20, and 25 × 25 cm(2) were evaluated. Measurements acquired with a CC13 cylindrical ionization chamber and electron diode detector and simulations from this framework were compared for a water phantom geometry. The evaluation metrics include percent depth dose, orthogonal and diagonal profiles at depths R100, R50, Rp, and Rp+ for standard and extended source-to-surface distances (SSD), as well as cone and cut-out output factors. Agreement for the percent depth dose and orthogonal profiles between measurement and Monte Carlo was generally within 2% or 1 mm. The largest discrepancies were observed within depths of 5 mm from phantom surface. Differences in field size, penumbra, and flatness for the orthogonal profiles at depths R100, R50, and Rp were within 1 mm, 1 mm, and 2%, respectively. Orthogonal profiles at SSDs of 100 and 120 cm showed the same level of agreement. Cone and cut-out output factors agreed well with maximum differences within 2.5% for 6 MeV and 1% for all other energies. Cone output factors at extended SSDs of 105, 110, 115, and 120 cm exhibited similar levels of agreement. We have presented a Monte Carlo simulation framework for electron beam dose calculations for Varian TrueBeam Linacs. Electron beam energies of 6 to 20 MeV for open and collimated field sizes from 3 × 3 to 25 × 25 cm(2) were studied and results were compared to the measurement data with excellent agreement. Application of this framework can thus be used as the platform for treatment planning of dynamic electron arc radiotherapy and other advanced dynamic techniques with electron beams.
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Tremonte, P; Reale, A; Di Renzo, T; Tipaldi, L; Di Luccia, A; Coppola, R; Sorrentino, E; Succi, M
2010-11-01
To evaluate interactions between Lactobacillus sakei and coagulase negative cocci (CNC) (Staphylococcus xylosus and Kocuria varians) and to investigate the influence of these interactions on their own proteolytic activity. Interactions occurring between strains of Lact. sakei and CNC were assessed by spectrophotometric analysis. The growth of 35 strains of Lact. sakei, used as indicators, was compared to that obtained combining the same strains with growing cells or cell-free supernatants of 20 CNC (18 Staph. xylosus and 2 K. varians). The proteolytic activity expressed by single strains or by their combinations was assessed on sarcoplasmic protein extracts by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The results evidenced that interactions are able to affect not only the growth but also the in vitro proteolytic activity of Lact. sakei and CNC used in combination. A relationship between the presence of interactions among useful strains and the strength of technological characteristics, such as proteolysis, was defined. The study highlighted that CNC are able to stimulate the growth of some Lact. sakei strains. At the same time, this interaction positively influences the proteolytic activity of strains used in combination. Given the importance of proteolysis during the ripening of fermented meats, this phenomenon should be taken into account to select meat starter cultures. © 2010 The Authors. © 2010 The Society for Applied Microbiology.
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NASA Astrophysics Data System (ADS)
Kairn, T.; Crowe, S. B.; Charles, P. H.; Trapp, J. V.
2014-03-01
This study investigates the variation of photon field penumbra shape with initial electron beam diameter, for very narrow beams. A Varian Millenium MLC (Varian Medical Systems, Palo Alto, USA) and a Brainlab m3 microMLC (Brainlab AB. Feldkirchen, Germany) were used, with one Varian iX linear accelerator, to produce fields that were (nominally) 0.20 cm across. Dose profiles for these fields were measured using radiochromic film and compared with the results of simulations completed using BEAMnrc and DOSXYZnrc, where the initial electron beam was set to FWHM = 0.02, 0.10, 0.12, 0.15, 0.20 and 0.50 cm. Increasing the electron-beam FWHM produced increasing occlusion of the photon source by the closely spaced collimator leaves and resulted in blurring of the simulated profile widths from 0.24 to 0.58 cm, for the MLC, from 0.11 to 0.40 cm, for the microMLC. Comparison with measurement data suggested that the electron spot size in the clinical linear accelerator was between FWHM = 0.10 and 0.15 cm, encompassing the result of our previous output-factor based work, which identified a FWHM of 0.12 cm. Investigation of narrow-beam penumbra variation has been found to be a useful procedure, with results varying noticeably with linear accelerator spot size and allowing FWHM estimates obtained using other methods to be verified.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Fraass, B.
Treatment planning is a central part of radiation therapy, including delineation in tumor volumes and critical organs, setting treatment goals of prescription doses to the tumor targets and tolerance doses to the critical organs, and finally generation of treatment plans to meet the treatment goals. National groups like RTOG have led the effort to standardize treatment goals of the prescription doses to the tumor targets and tolerance doses to the critical organs based on accumulated knowledge from decades of abundant clinical trial experience. The challenge for each clinical department is how to achieve or surpass these set goals within themore » time constraints of clinical practice. Using fifteen testing cases from different treatment sites such as head and neck, prostate with and without pelvic lymph nodes, SBRT spine, we will present clinically utility of advanced planning tools, including knowledge based, automatic based, and multiple criteria based tools that are clinically implemented. The objectives of this session are: Understand differences among these three advanced planning tools Provide clinical assessments on the utility of the advanced planning tools Discuss clinical challenges of treatment planning with large variations in tumor volumes and their relationships with adjacent critical organs. Ping Xia received research grant from Philips. Jackie Wu received research grant from Varian; P. Xia, Research support by Philips and Varian; Q. Wu, NIH, Varian Medical.« less
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MO-D-BRC-03: Knowledge-Based Planning
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wu, Q.
Treatment planning is a central part of radiation therapy, including delineation in tumor volumes and critical organs, setting treatment goals of prescription doses to the tumor targets and tolerance doses to the critical organs, and finally generation of treatment plans to meet the treatment goals. National groups like RTOG have led the effort to standardize treatment goals of the prescription doses to the tumor targets and tolerance doses to the critical organs based on accumulated knowledge from decades of abundant clinical trial experience. The challenge for each clinical department is how to achieve or surpass these set goals within themore » time constraints of clinical practice. Using fifteen testing cases from different treatment sites such as head and neck, prostate with and without pelvic lymph nodes, SBRT spine, we will present clinically utility of advanced planning tools, including knowledge based, automatic based, and multiple criteria based tools that are clinically implemented. The objectives of this session are: Understand differences among these three advanced planning tools Provide clinical assessments on the utility of the advanced planning tools Discuss clinical challenges of treatment planning with large variations in tumor volumes and their relationships with adjacent critical organs. Ping Xia received research grant from Philips. Jackie Wu received research grant from Varian; P. Xia, Research support by Philips and Varian; Q. Wu, NIH, Varian Medical.« less
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MO-D-BRC-04: Multiple-Criteria Optimization Planning
DOE Office of Scientific and Technical Information (OSTI.GOV)
Donaghue, J.
Treatment planning is a central part of radiation therapy, including delineation in tumor volumes and critical organs, setting treatment goals of prescription doses to the tumor targets and tolerance doses to the critical organs, and finally generation of treatment plans to meet the treatment goals. National groups like RTOG have led the effort to standardize treatment goals of the prescription doses to the tumor targets and tolerance doses to the critical organs based on accumulated knowledge from decades of abundant clinical trial experience. The challenge for each clinical department is how to achieve or surpass these set goals within themore » time constraints of clinical practice. Using fifteen testing cases from different treatment sites such as head and neck, prostate with and without pelvic lymph nodes, SBRT spine, we will present clinically utility of advanced planning tools, including knowledge based, automatic based, and multiple criteria based tools that are clinically implemented. The objectives of this session are: Understand differences among these three advanced planning tools Provide clinical assessments on the utility of the advanced planning tools Discuss clinical challenges of treatment planning with large variations in tumor volumes and their relationships with adjacent critical organs. Ping Xia received research grant from Philips. Jackie Wu received research grant from Varian; P. Xia, Research support by Philips and Varian; Q. Wu, NIH, Varian Medical.« less
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MO-D-BRC-00: In Memoriam of Jan Van De Geijn: Knowledge-Based Planning
DOE Office of Scientific and Technical Information (OSTI.GOV)
NONE
Treatment planning is a central part of radiation therapy, including delineation in tumor volumes and critical organs, setting treatment goals of prescription doses to the tumor targets and tolerance doses to the critical organs, and finally generation of treatment plans to meet the treatment goals. National groups like RTOG have led the effort to standardize treatment goals of the prescription doses to the tumor targets and tolerance doses to the critical organs based on accumulated knowledge from decades of abundant clinical trial experience. The challenge for each clinical department is how to achieve or surpass these set goals within themore » time constraints of clinical practice. Using fifteen testing cases from different treatment sites such as head and neck, prostate with and without pelvic lymph nodes, SBRT spine, we will present clinically utility of advanced planning tools, including knowledge based, automatic based, and multiple criteria based tools that are clinically implemented. The objectives of this session are: Understand differences among these three advanced planning tools Provide clinical assessments on the utility of the advanced planning tools Discuss clinical challenges of treatment planning with large variations in tumor volumes and their relationships with adjacent critical organs. Ping Xia received research grant from Philips. Jackie Wu received research grant from Varian; P. Xia, Research support by Philips and Varian; Q. Wu, NIH, Varian Medical.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Xia, P.
Treatment planning is a central part of radiation therapy, including delineation in tumor volumes and critical organs, setting treatment goals of prescription doses to the tumor targets and tolerance doses to the critical organs, and finally generation of treatment plans to meet the treatment goals. National groups like RTOG have led the effort to standardize treatment goals of the prescription doses to the tumor targets and tolerance doses to the critical organs based on accumulated knowledge from decades of abundant clinical trial experience. The challenge for each clinical department is how to achieve or surpass these set goals within themore » time constraints of clinical practice. Using fifteen testing cases from different treatment sites such as head and neck, prostate with and without pelvic lymph nodes, SBRT spine, we will present clinically utility of advanced planning tools, including knowledge based, automatic based, and multiple criteria based tools that are clinically implemented. The objectives of this session are: Understand differences among these three advanced planning tools Provide clinical assessments on the utility of the advanced planning tools Discuss clinical challenges of treatment planning with large variations in tumor volumes and their relationships with adjacent critical organs. Ping Xia received research grant from Philips. Jackie Wu received research grant from Varian; P. Xia, Research support by Philips and Varian; Q. Wu, NIH, Varian Medical.« less
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Kim, Sangroh; Yoshizumi, Terry T; Toncheva, Greta; Frush, Donald P; Yin, Fang-Fang
2010-03-01
The purpose of this study was to establish a dose estimation tool with Monte Carlo (MC) simulations. A 5-y-old paediatric anthropomorphic phantom was computed tomography (CT) scanned to create a voxelised phantom and used as an input for the abdominal cone-beam CT in a BEAMnrc/EGSnrc MC system. An X-ray tube model of the Varian On-Board Imager((R)) was built in the MC system. To validate the model, the absorbed doses at each organ location for standard-dose and low-dose modes were measured in the physical phantom with MOSFET detectors; effective doses were also calculated. In the results, the MC simulations were comparable to the MOSFET measurements. This voxelised phantom approach could produce a more accurate dose estimation than the stylised phantom method. This model can be easily applied to multi-detector CT dosimetry.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Casey, Kevin E.; Kry, Stephen F.; Howell, Rebecca M.
Purpose: The aim of this work was to create a mailable phantom with measurement accuracy suitable for Radiological Physics Center (RPC) audits of high dose-rate (HDR) brachytherapy sources at institutions participating in National Cancer Institute-funded cooperative clinical trials. Optically stimulated luminescence dosimeters (OSLDs) were chosen as the dosimeter to be used with the phantom.Methods: The authors designed and built an 8 × 8 × 10 cm{sup 3} prototype phantom that had two slots capable of holding Al{sub 2}O{sub 3}:C OSLDs (nanoDots; Landauer, Glenwood, IL) and a single channel capable of accepting all {sup 192}Ir HDR brachytherapy sources in current clinicalmore » use in the United States. The authors irradiated the phantom with Nucletron and Varian {sup 192}Ir HDR sources in order to determine correction factors for linearity with dose and the combined effects of irradiation energy and phantom characteristics. The phantom was then sent to eight institutions which volunteered to perform trial remote audits.Results: The linearity correction factor was k{sub L}= (−9.43 × 10{sup −5}× dose) + 1.009, where dose is in cGy, which differed from that determined by the RPC for the same batch of dosimeters using {sup 60}Co irradiation. Separate block correction factors were determined for current versions of both Nucletron and Varian {sup 192}Ir HDR sources and these vendor-specific correction factors differed by almost 2.6%. For the Nucletron source, the correction factor was 1.026 [95% confidence interval (CI) = 1.023–1.028], and for the Varian source, it was 1.000 (95% CI = 0.995–1.005). Variations in lateral source positioning up to 0.8 mm and distal/proximal source positioning up to 10 mm had minimal effect on dose measurement accuracy. The overall dose measurement uncertainty of the system was estimated to be 2.4% and 2.5% for the Nucletron and Varian sources, respectively (95% CI). This uncertainty was sufficient to establish a ±5% acceptance criterion for source strength audits under a formal RPC audit program. Trial audits of four Nucletron sources and four Varian sources revealed an average RPC-to-institution dose ratio of 1.000 (standard deviation = 0.011).Conclusions: The authors have created an OSLD-based {sup 192}Ir HDR brachytherapy source remote audit tool which offers sufficient dose measurement accuracy to allow the RPC to establish a remote audit program with a ±5% acceptance criterion. The feasibility of the system has been demonstrated with eight trial audits to date.« less
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Kong, X; Clausen, C; Wang, S
2012-06-01
Clinical experience for configuration, commission and implementation of SmartArc with MOSAIQ R&V system. SmartArc is Pinnacle's solution for VMAT. On July 2011 we updated to Pinnacle 9.0 and purchased SmartArc. A standalone Eclipse workstation has been used 3 years for VMAT planning. Our clinical setting: Mosaiq 2.2; Varian Trilogy driven by 4DiTC and Varian 21ex driven by sequencer. Some key physics parameters have been studied: machine dose rate; MLC leaf speed; Leaf motion per gantry rotation. Tabletop was created by user to improve the dose accuracy for planning. In-house sandwich phantom was used with MapCheck for planner dose verification. A PTW 0.6cc ion chamber was included for absolute dose comparison. A copy of current machine data with default highest dose rate is recommended. It is due to after 10th iteration of optimization, the default dose rate will kick in. 2.5cm/s is the constraint for Varian Millennium 120 MLC; a buffer zone of 10% is suggested to reduce the MLC error on treatment. 2.25cm/s is used in our configuration. This results in MLC interlock if not configured correct. Maximum leaf motion per gantry rotation of 0.46cm/degree has to be checked for planning with Mosaiq R&V. Otherwise, undeliverable plan will show up sometimes on 4DiTC.Tabletop was exported as a DICOM structure from Eclipse to Pinnacle; we created a ROI template based on the matched tabletop.QA using in-house phantom for different sites were tested. Results for both planner dose and absolute chamber measurement are satisfactory. Special attentions need to be paid for dose rate, MLC leaf speed, leaf motion per gantry rotation when configuring SmartArc. Varian 21ex is supported but is slow for clinical delivery. Users need to create your own tabletop to improve planning accuracy. Conventional commission procedures for RapidArc also apply for SmartArc. © 2012 American Association of Physicists in Medicine.
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Radio frequency noise from an MLC: a feasibility study of the use of an MLC for linac-MR systems.
Lamey, M; Yun, J; Burke, B; Rathee, S; Fallone, B G
2010-02-21
Currently several groups are actively researching the integration of a megavoltage teletherapy unit with magnetic resonance (MR) imaging for real-time image-guided radiotherapy. The use of a multileaf collimator (MLC) for intensity-modulated radiotherapy for linac-MR units must be investigated. The MLC itself will likely reside in the fringe field of the MR and the motors will produce radio frequency (RF) noise. The RF noise power spectral density from a Varian 52-leaf MLC motor, a Varian Millennium MLC motor and a brushless fan motor has been measured as a function of the applied magnetic field using a near field probe set. For the Varian 52-leaf MLC system, the RF noise produced by 13 of 52 motors is studied as a function of distance from the MLC. Data are reported in the frequency range suitable for 0.2-1.5 T linac-MR systems. Below 40 MHz the Millennium MLC motor tested showed more noise than the Varian 52-leaf motor or the brushless fan motor. The brushless motor showed a small dependence on the applied magnetic field. Images of a phantom were taken by the prototype linac-MR system with the MLC placed in close proximity to the magnet. Several orientations of the MLC in both shielded and non-shielded configurations were studied. For the case of a non-shielded MLC and associated cables, the signal-to-noise ratio (SNR) was reduced when 13 of 52 MLC leaves were moved during imaging. When the MLC and associated cables were shielded, the measured SNR of the images with 13 MLC leaves moving was experimentally the same as the SNR of the stationary MLC image. When the MLC and cables are shielded, subtraction images acquired with and without MLC motion contains no systematic signal. This study illustrates that the small RF noise produced by functioning MLC motors can be effectively shielded to avoid SNR degradation. A functioning MLC can be incorporated into a linac-MR unit.
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Radio frequency noise from an MLC: a feasibility study of the use of an MLC for linac-MR systems
Lamey, M; Yun, J; Burke, B; Rathee, S; Fallone, B G
2010-01-01
Currently several groups are actively researching the integration of a megavoltage teletherapy unit with magnetic resonance (MR) imaging for real-time image-guided radiotherapy. The use of a multileaf collimator (MLC) for intensity-modulated radiotherapy for linac-MR units must be investigated. The MLC itself will likely reside in the fringe field of the MR and the motors will produce radio frequency (RF) noise. The RF noise power spectral density from a Varian 52-leaf MLC motor, a Varian Millennium MLC motor and a brushless fan motor has been measured as a function of the applied magnetic field using a near field probe set. For the Varian 52-leaf MLC system, the RF noise produced by 13 of 52 motors is studied as a function of distance from the MLC. Data are reported in the frequency range suitable for 0.2–1.5 T linac-MR systems. Below 40 MHz the Millennium MLC motor tested showed more noise than the Varian 52-leaf motor or the brushless fan motor. The brushless motor showed a small dependence on the applied magnetic field. Images of a phantom were taken by the prototype linac-MR system with the MLC placed in close proximity to the magnet. Several orientations of the MLC in both shielded and non-shielded configurations were studied. For the case of a non-shielded MLC and associated cables, the signal-to-noise ratio (SNR) was reduced when 13 of 52 MLC leaves were moved during imaging. When the MLC and associated cables were shielded, the measured SNR of the images with 13 MLC leaves moving was experimentally the same as the SNR of the stationary MLC image. When the MLC and cables are shielded, subtraction images acquired with and without MLC motion contains no systematic signal. This study illustrates that the small RF noise produced by functioning MLC motors can be effectively shielded to avoid SNR degradation. A functioning MLC can be incorporated into a linac-MR unit. PMID:20090187
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Andersen, A; Casares-Magaz, O; Elstroem, U
Purpose: Cone-beam CT (CBCT) imaging may enable image- and dose-guided proton therapy, but is challenged by image artefacts. The aim of this study was to demonstrate the general applicability of a previously developed a priori scatter correction algorithm to allow CBCT-based proton dose calculations. Methods: The a priori scatter correction algorithm used a plan CT (pCT) and raw cone-beam projections acquired with the Varian On-Board Imager. The projections were initially corrected for bow-tie filtering and beam hardening and subsequently reconstructed using the Feldkamp-Davis-Kress algorithm (rawCBCT). The rawCBCTs were intensity normalised before a rigid and deformable registration were applied on themore » pCTs to the rawCBCTs. The resulting images were forward projected onto the same angles as the raw CB projections. The two projections were subtracted from each other, Gaussian and median filtered, and then subtracted from the raw projections and finally reconstructed to the scatter-corrected CBCTs. For evaluation, water equivalent path length (WEPL) maps (from anterior to posterior) were calculated on different reconstructions of three data sets (CB projections and pCT) of three parts of an Alderson phantom. Finally, single beam spot scanning proton plans (0–360 deg gantry angle in steps of 5 deg; using PyTRiP) treating a 5 cm central spherical target in the pCT were re-calculated on scatter-corrected CBCTs with identical targets. Results: The scatter-corrected CBCTs resulted in sub-mm mean WEPL differences relative to the rigid registration of the pCT for all three data sets. These differences were considerably smaller than what was achieved with the regular Varian CBCT reconstruction algorithm (1–9 mm mean WEPL differences). Target coverage in the re-calculated plans was generally improved using the scatter-corrected CBCTs compared to the Varian CBCT reconstruction. Conclusion: We have demonstrated the general applicability of a priori CBCT scatter correction, potentially opening for CBCT-based image/dose-guided proton therapy, including adaptive strategies. Research agreement with Varian Medical Systems, not connected to the present project.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yaddanapudi, S; Cai, B; Sun, B
2015-06-15
Purpose: Electronic portal imaging devices (EPIDs) have proven to be useful for measuring several parameters of interest in linear accelerator (linac) quality assurance (QA). The purpose of this project was to evaluate the feasibility of using EPIDs for determining linac photon beam energies. Methods: Two non-clinical Varian TrueBeam linacs (Varian Medical Systems, Palo Alto, CA) with 6MV and 10MV photon beams were used to perform the measurements. The linacs were equipped with an amorphous silicon based EPIDs (aSi1000) that were used for the measurements. We compared the use of flatness versus percent depth dose (PDD) for predicting changes in linacmore » photon beam energy. PDD was measured in 1D water tank (Sun Nuclear Corporation, Melbourne FL) and the profiles were measured using 2D ion-chamber array (IC-Profiler, Sun Nuclear) and the EPID. Energy changes were accomplished by varying the bending magnet current (BMC). The evaluated energies conformed with the AAPM TG142 tolerance of ±1% change in PDD. Results: BMC changes correlating with a ±1% change in PDD corresponded with a change in flatness of ∼1% to 2% from baseline values on the EPID. IC Profiler flatness values had the same correlation. We observed a similar trend for the 10MV beam energy changes. Our measurements indicated a strong correlation between changes in linac photon beam energy and changes in flatness. For all machines and energies, beam energy changes produced change in the uniformity (AAPM TG-142), varying from ∼1% to 2.5%. Conclusions: EPID image analysis of beam profiles can be used to determine linac photon beam energy changes. Flatness-based metrics or uniformity as defined by AAPM TG-142 were found to be more sensitive to linac photon beam energy changes than PDD. Research funding provided by Varian Medical Systems. Dr. Sasa Mutic receives compensation for providing patient safety training services from Varian Medical Systems, the sponsor of this study.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Cardenas, C; Nitsch, P; Kudchadker, R
2015-06-15
Purpose: Accurately determining out-of-field doses when using electron beam radiotherapy is of importance when treating pregnant patients or patients with implanted electronic devices. Scattered doses outside of the applicator field in electron beams have not been broadly investigated, especially since manufacturers have taken different approaches in applicator designs. Methods: In this study, doses outside of the applicator field were measured for electron beams produced by a 10×10 applicator on two Varian 21iXs operating at 6, 9, 12, 16, and 20 MeV, a Varian TrueBeam operating at 6, 9, 12, 16, and 20 MeV, and an Elekta Versa HD operating atmore » 6, 9, 12 and 15 MeV. Peripheral dose profiles and percent depth doses were measured in a Wellhofer water phantom at 100 cm SSD with a Farmer ion chamber. Doses were compared to peripheral photon doses from AAPM’s Task Group #36 report. Results: Doses were highest for the highest electron energies. Doses typically decreased with increasing distance from the field edge but showed substantial increases over some distance ranges. Substantial dose differences were observed between different accelerators; the Elekta accelerator had much higher doses than any Varian unit examined. Surprisingly, doses were often similar to, and could be much higher than, doses from photon therapy. Doses decreased sharply with depth before becoming nearly constant; the dose was found to decrease to a depth of approximately E(MeV)/4 in cm. Conclusion: The results of this study indicate that proper shielding may be very important when utilizing electron beams, particularly on a Versa HD, while treating pregnant patients or those with implanted electronic devices. Applying a water equivalent bolus of Emax(MeV)/4 thickness (cm) on the patient would reduce fetal dose drastically for all clinical energies and is a practical solution to manage the potentially high peripheral doses seen from modern electron beams. Funding from NIH Grant number: #CA180803.« less
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Comparison of optimization algorithms in intensity-modulated radiation therapy planning
NASA Astrophysics Data System (ADS)
Kendrick, Rachel
Intensity-modulated radiation therapy is used to better conform the radiation dose to the target, which includes avoiding healthy tissue. Planning programs employ optimization methods to search for the best fluence of each photon beam, and therefore to create the best treatment plan. The Computational Environment for Radiotherapy Research (CERR), a program written in MATLAB, was used to examine some commonly-used algorithms for one 5-beam plan. Algorithms include the genetic algorithm, quadratic programming, pattern search, constrained nonlinear optimization, simulated annealing, the optimization method used in Varian EclipseTM, and some hybrids of these. Quadratic programing, simulated annealing, and a quadratic/simulated annealing hybrid were also separately compared using different prescription doses. The results of each dose-volume histogram as well as the visual dose color wash were used to compare the plans. CERR's built-in quadratic programming provided the best overall plan, but avoidance of the organ-at-risk was rivaled by other programs. Hybrids of quadratic programming with some of these algorithms seems to suggest the possibility of better planning programs, as shown by the improved quadratic/simulated annealing plan when compared to the simulated annealing algorithm alone. Further experimentation will be done to improve cost functions and computational time.
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2012-01-01
Background The radiation field on most megavoltage radiation therapy units are shown by a light field projected through the collimator by a light source mounted inside the collimator. The light field is traditionally used for patient alignment. Hence it is imperative that the light field is congruent with the radiation field. Method A simple quality assurance tool has been designed for rapid and simple test of the light field and radiation field using electronic portal images device (EPID) or computed radiography (CR). We tested this QA tool using Varian PortalVision and Elekta iViewGT EPID systems and Kodak CR system. Results Both the single and double exposure techniques were evaluated, with double exposure technique providing a better visualization of the light-radiation field markers. The light and radiation congruency could be detected within 1 mm. This will satisfy the American Association of Physicists in Medicine task group report number 142 recommendation of 2 mm tolerance. Conclusion The QA tool can be used with either an EPID or CR to provide a simple and rapid method to verify light and radiation field congruence. PMID:22452821
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Rainbow, P.S.; Poirier, L.; Smith, B.D.; Brix, K.V.; Luoma, S.N.
2006-01-01
Diet is an important exposure route for the uptake of trace metals by aquatic invertebrates, with trace metal trophic transfer depending on 2 stages - assimilation and subsequent accumulation by the predator. This study investigated the trophic transfer of trace metals from the sediment-dwelling polychaete worm Nereis diversicolor from metal-rich estuarine sediments in southwestern UK to 2 predators - another polychaete N. virens (Cu, Zn, Pb, Cd, Fe) and the decapod crustacean Palaemonetes varians (Cu, Zn, Pb, Cd, Fe, Ag, As, Mn). N. virens showed net accumulation of Cu, Zn, Pb and Cd from the prey; accumulation increased with increasing prey concentration, but a coefficient of trophic transfer decreased with increasing prey concentration, probably because a higher proportion of accumulated metal in the prey is bound in less trophically available (insoluble) detoxified forms. The trace metal accumulation patterns of P. varians apparently restricted significant net accumulation of metals from the diet of N. diversicolor to just Cd. There was significant mortality of the decapods fed on the diets of metal-rich worms. Metal-rich invertebrates that have accumulated metals from the rich historical store in the sediments of particular SW England estuaries can potentially pass these metals along food chains, with accumulation and total food chain transfer depending on the metal assimilation efficiencies and accumulation patterns of the animal at each trophic level. This trophic transfer may be significant enough to have ecotoxicological effects. ?? Inter-Research 2006.
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NASA Astrophysics Data System (ADS)
Ajo, Ramzi, Jr.
Modern treatment planning systems (TPS's) utilize different algorithms in computing dose within the patient medium. The algorithms rely on properly modeled clinical setups in order to perform optimally. Aside from various parameters of the beam, modifiers, such as multileaf collimators (MLC's), must also be modeled properly. That could not be more true today, where dynamic delivery such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) are being increasingly utilized due to their ability to deliver higher dose precisely to the target while sparing more surrounding normal tissue. Two of the most popular TPS's, Pinnacle (Philips) and Eclipse (Varian), were compared, with special emphasis placed on parameterization of the dosimetric leaf gap (DLG) in Eclipse. The DLG is a parameter that accounts for Varian's rounded MLC leaf ends. While Pinnacle accounts for the rounded leaf end by modeling the MLC's, Eclipse uses a measured parameter. This study investigated whether a single value measured DLG is sufficient for dynamic delivery. Using five planning volumes for vertebral body SBRT treatments, each prescribed for 3000 cGy in 5 fractions, an array of 20 treatment plans was generated using varying energies of 6MV-FFF and 10MV-FFF. Treatment techniques consisted of 9-field Step-and-shoot IMRT, and dual-arc VMAT using patient specific optimization criteria in the Pinnacle TPS v9.8. Each plan was normalized to ensure coverage of 3000cGy to 95% of the target volume. The dose was computed in Pinnacle v9.8, with the Collapsed Cone Convolution Superposition algorithm and Eclipse v11, with the Acuros XB algorithm, using a dose grid resolution of 2 mm in both systems. Dose volume histograms (DVH's) were generated for a comparison of max and mean dose to the targets and spinal cord, as well as 95% coverage of the targets and the volume of the spinal cord receiving 14.5 Gy (V14.5). Patient specific quality assurance (PSQA) fields were generated and then delivered, using a Varian Edge linear accelerator, to a 4D QA phantom for a gamma analysis and distance to agreement (DTA) comparison. All Eclipse calculations were made for both measured and optimized DLG parameters. Calculated vs. measured point dose for the Pinnacle TPS had an average difference of 2.79 +/- 2.00%. Gamma analysis using a 3% and 3 mm DTA had 99/100 fields passing at > 95%. Using measured values of the DLG in Eclipse, calculated vs. measured point dose was -4.44 +/- 1.97%, and DTA had 33/110 fields passing at > 95%. After an optimization of the DLG in Eclipse, calculated vs. measured point dose had an average difference of 2.20 +/- 2.23%, and DTA with 95/110 fields passing at > 95%. This study looked at the performance of the Pinnacle and Eclipse TPS's, with special consideration given to the DLG parameterization used by Eclipse. The results support the idea that a single valued DLG is not sufficient for dynamic delivery. An optimization of the parameter is necessary to account for the high modulation of IMRT and VMAT techniques.
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SU-G-TeP4-02: A Method for Evaluating the Direct Impact of Failed IMRT QAs On Patient Dose
DOE Office of Scientific and Technical Information (OSTI.GOV)
Geneser, S; Butkus, M
Purpose: We developed a method to calculate patient doses corresponding to IMRT QA measurements in order to determine and assess the actual dose delivered for plans with failed (or borderline) IMRT QA. This work demonstrates the feasibility of automatically computing delivered patient dose from portal dosimetry measurements in the Varian TPS system, which would provide a valuable and clinically viable IMRT QA tool for physicists and physicians. Methods: IMRT QA fluences were measured using portal dosimetry, processed using in-house matlab software, and imported back into Eclipse to calculate dose on the planning CT. To validate the proposed workflow, the Eclipsemore » calculated portal dose for a 5-field sliding window prostate boost plan was processed as described above. The resulting dose was compared to the planned dose and found to be within 0.5 Gy. Two IMRT QA results for the prostate boost plan (one that failed and one that passed) were processed and the resulting patient doses were evaluated. Results: The max dose difference between IMRT QA #1 and the original planned and approved dose is 4.5 Gy, while the difference between the planned and IMRT QA #2 dose is 4.0 Gy. The inferior portion of the PTV is slightly underdosed in both plans, and the superior portion is slightly overdosed. The patient dose resulting from IMRT QA #1 and #2 differs by only 0.5 Gy. With this new information, it may be argued that the evaluated plan alteration to obtain passing gamma analysis produced clinically irrelevant differences. Conclusion: Evaluation of the delivered QA dose on the planning CT provides valuable information about the clinical relevance of failed or borderline IMRT QAs. This particular workflow demonstrates the feasibility of pushing the measured IMRT QA portal dosimetry results directly back onto the patient planning CT within the Varian system.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
He, R.; Giri, Shankar; VA Medical Center at Jackson, Mississippi
2014-06-01
Purpose: Target localization of prostate for Intensity Modulated Radiation Therapy (IMRT) in patients with bilateral hip replacements is difficult due to artifacts in Computed Tomography (CT) images generated from the prostheses high Z materials. In this study, Magnetic Resonance (MR) images fused with CT images are tested as a solution. Methods: CT images of 2.5 mm slice thickness were acquired on a GE Lightspeed scanner with a flat-topped couch for a prostate cancer patient with bilateral hip replacements. T2 weighted images of 5 mm separation were acquired on a MR Scanner. After the MR-CT registration on a radiotherapy treatment planningmore » system (Eclipse, Varian), the target volumes were defined by the radiation oncologists on MR images and then transferred to CT images for planning and dose calculation. The CT Hounsfield Units (HU) was reassigned to zero (as water) for artifacts. The Varian flat panel treatment couch was modeled for dose calculation accuracy with heterogeneity correction. A Volume Matrix Arc Therapy (VMAT) and a seven-field IMRT plans were generated, each avoiding any beam transversing the prostheses; the two plans were compared. The superior VMAT plan was used for treating the patient. In-vivo dosimetry was performed using MOSFET (Best Canada) placed in a surgical tube inserted into the patient rectum during therapy. The measured dose was compared with planned dose for MOSFET location. Results: The registration of MR-CT images and the agreement of target volumes were confirmed by three physicians. VMAT plan was deemed superior to IMRT based on dose to critical nearby structures and overall conformality of target dosing. In-vivo measured dose compared with calculated dose was -4.5% which was likely due to attenuation of the surgical tube surrounding MOSFET. Conclusion: When artifacts are present on planning CT due to bilateral hip prostheses, MR-CT image fusion is a feasible solution for target delineation.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zlateva, Yana; Seuntjens, Jan; El Naqa, Issam
Purpose: To advance towards clinical Cherenkov emission (CE)-based dosimetry by investigating beam-specific effects on Monte Carlo-calculated electron-beam stopping power-to-CE power ratios (SCRs), addressing electron beam quality specification in terms of CE, and validating simulations with measurements. Methods: The EGSnrc user code SPRRZnrc, used to calculate Spencer-Attix stopping-power ratios, was modified to instead calculate SCRs. SCRs were calculated for 6- to 22-MeV clinical electron beams from Varian TrueBeam, Clinac 21EX, and Clinac 2100C/D accelerators. Experiments were performed with a 20-MeV electron beam from a Varian TrueBeam accelerator, using a diffraction grating spectrometer with optical fiber input and a cooled back-illuminated CCD.more » A fluorophore was dissolved in the water to remove CE signal anisotropy. Results: It was found that angular spread of the incident beam has little effect on the SCR (≤ 0.3% at d{sub max}), while both the electron spectrum and photon contamination increase the SCR at shallow depths and decrease it at large depths. A universal data fit of R{sub 50} in terms of C{sub 50} (50% CE depth) revealed a strong linear dependence (R{sup 2} > 0.9999). The SCR was fit with a Burns-type equation (R{sup 2} = 0.9974, NRMSD = 0.5%). Below-threshold incident radiation was found to have minimal effect on beam quality specification (< 0.1%). Experiments and simulations were in good agreement. Conclusions: Our findings confirm the feasibility of the proposed CE dosimetry method, contingent on computation of SCRs from additional accelerators and on further experimental validation. This work constitutes an important step towards clinical high-resolution out-of-beam CE dosimetry.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zwan, B J; University of Newcastle, Newcastle, NSW; Barnes, M
2016-06-15
Purpose: To automate gantry-resolved linear accelerator (linac) quality assurance (QA) for volumetric modulated arc therapy (VMAT) using an electronic portal imaging device (EPID). Methods: A QA system for VMAT was developed that uses an EPID, frame-grabber assembly and in-house developed image processing software. The system relies solely on the analysis of EPID image frames acquired without the presence of a phantom. Images were acquired at 8.41 frames per second using a frame grabber and ancillary acquisition computer. Each image frame was tagged with a gantry angle from the linac’s on-board gantry angle encoder. Arc-dynamic QA plans were designed to assessmore » the performance of each individual linac component during VMAT. By analysing each image frame acquired during the QA deliveries the following eight machine performance characteristics were measured as a function of gantry angle: MLC positional accuracy, MLC speed constancy, MLC acceleration constancy, MLC-gantry synchronisation, beam profile constancy, dose rate constancy, gantry speed constancy, dose-gantry angle synchronisation and mechanical sag. All tests were performed on a Varian iX linear accelerator equipped with a 120 leaf Millennium MLC and an aS1000 EPID (Varian Medical Systems, Palo Alto, CA, USA). Results: Machine performance parameters were measured as a function of gantry angle using EPID imaging and compared to machine log files and the treatment plan. Data acquisition is currently underway at 3 centres, incorporating 7 treatment units, at 2 weekly measurement intervals. Conclusion: The proposed system can be applied for streamlined linac QA and commissioning for VMAT. The set of test plans developed can be used to assess the performance of each individual components of the treatment machine during VMAT deliveries as a function of gantry angle. The methodology does not require the setup of any additional phantom or measurement equipment and the analysis is fully automated to allow for regular routine testing.« less
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Dosimetric evaluation of total marrow irradiation using 2 different planning systems
DOE Office of Scientific and Technical Information (OSTI.GOV)
Nalichowski, Adrian, E-mail: nalichoa@karmanos.org; Eagle, Don G.; Burmeister, Jay
This study compared 2 different treatment planning systems (TPSs) for quality and efficiency of total marrow irradiation (TMI) plans. The TPSs used in this study were VOxel-Less Optimization (VoLO) (Accuray Inc, Sunnyvale, CA) using helical dose delivery on a Tomotherapy Hi-Art treatment unit and Eclipse (Varian Medical Systems Inc, Palo Alto, CA) using volumetric modulated arc therapy (VMAT) dose delivery on a Varian iX treatment unit. A total dose of 1200 cGy was prescribed to cover 95% of the planning target volume (PTV). The plans were optimized and calculated based on a single CT data and structure set using themore » Alderson Rando phantom (The Phantom Laboratory, Salem, NY) and physician contoured target and organ at risk (OAR) volumes. The OARs were lungs, heart, liver, kidneys, brain, and small bowel. The plans were evaluated based on plan quality, time to optimize the plan and calculate the dose, and beam on time. The resulting mean and maximum doses to the PTV were 1268 and 1465 cGy for VoLO and 1284 and 1541 cGy for Eclipse, respectively. For 5 of 6 OAR structures the VoLO system achieved lower mean and D10 doses ranging from 22% to 52% and 3% to 44%, respectively. Total computational time including only optimization and dose calculation were 0.9 hours for VoLO and 3.8 hours for Eclipse. These times do not include user-dependent target delineation and field setup. Both planning systems are capable of creating high-quality plans for total marrow irradiation. The VoLO planning system was able to achieve more uniform dose distribution throughout the target volume and steeper dose fall off, resulting in superior OAR sparing. VoLO's graphics processing unit (GPU)–based optimization and dose calculation algorithm also allowed much faster creation of TMI plans.« less
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SU-G-BRC-17: Using Generalized Mean for Equivalent Square Estimation
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhou, S; Fan, Q; Lei, Y
Purpose: Equivalent Square (ES) is a widely used concept in radiotherapy. It enables us to determine many important quantities for a rectangular treatment field, without measurement, based on the corresponding values from its ES field. In this study, we propose a Generalized Mean (GM) type ES formula and compare it with other established formulae using benchmark datasets. Methods: Our GM approach is expressed as ES=(w•fx^α+(1-w)•fy^α)^(1/α), where fx, fy, α, and w represent field sizes, power index, and a weighting factor, respectively. When α=−1 it reduces to well-known Sterling type ES formulae. In our study, α and w are determined throughmore » least-square-fitting. Akaike Information Criterion (AIC) was used to benchmark the performance of each formula. BJR (Supplement 17) ES field table for X-ray PDDs and open field output factor tables in Varian TrueBeam representative dataset were used for validation. Results: Switching from α=−1 to α=−1.25, a 20% reduction in standard deviation of residual error in ES estimation was achieved for the BJR dataset. The maximum relative residual error was reduced from ∼3% (in Sterling formula) or ∼2% (in Vadash/Bjarngard formula) down to ∼1% in GM formula for open fields of all energies and at rectangular field sizes from 3cm to 40cm in the Varian dataset. The improvement of the GM over the Sterling type ES formulae is particularly noticeable for very elongated rectangular fields with short width. AIC analysis confirmed the superior performance of the GM formula after taking into account the expanded parameter space. Conclusion: The GM significantly outperforms Sterling type formulae at slightly increased computational cost. The GM calculation may nullify the requirement of data measurement for many rectangular fields and hence shorten the Linac commissioning process. Improved dose calculation accuracy is also expected by adopting the GM formula into treatment planning and secondary MU check systems.« less
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Nicolini, G; Abraham, S; Fogliata, A; Jordaan, A; Clivio, A; Vanetti, E; Cozzi, L
2013-03-01
To evaluate the use of volumetric-modulated arc therapy [VMAT, RapidArc® (RA); Varian Medical Systems, Palo Alto, CA] for the treatment of cutaneous Kaposi's sarcoma (KS) of lower extremities with adequate target coverage and high bone sparing, and to compare VMAT with electron beam therapy. 10 patients were planned with either RA or electron beams. The dose was prescribed to 30 Gy, 10 fractions, to mean the planning target volume (PTV), and significant maximum dose to bone was limited to 30 Gy. Plans were designed for 6-MV photon beams for RA and 6 MeV for electrons. Dose distributions were computed with AcurosXB® (Varian Medical Systems) for photons and with a Monte Carlo algorithm for electrons. V(90%) was 97.3±1.2 for RA plans and 78.2±2.6 for electrons; similarly, V(107%) was 2.5±2.2 and 37.7±3.4, respectively. RA met coverage criteria. Concerning bone sparing, D(2%) was 29.6±1.1 for RA and 31.0±2.4 for electrons. Although acceptable for bone involvement, pronounced target coverage violations were obtained for electron plans. Monitor units were similar for electrons and RA, although for the latter they increased when superior bone sparing was imposed. Delivery times were 12.1±4.0 min for electrons and 4.8±1.3 min for the most modulated RA plans. High plan quality was shown for KS in the lower extremities using VMAT, and this might simplify their management in comparison with the more conventional usage of electrons, particularly in institutes with limited staff resources and heavy workloads. VMAT is also dosimetrically extremely advantageous in a typology of treatments where electron beam therapy is mainly considered to be effective owing to the limited penetration of the beams.
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SU-E-T-171: Missing Dose in Integrated EPID Images.
King, B; Seymour, E; Nitschke, K
2012-06-01
A dosimetric artifact has been observed with Varian EPIDs in the presence of beam interrupts. This work determines the root cause and significance of this artifact. Integrated mode EPID images were acquired both with and without a manual beam interrupt for rectangular, sliding gap IMRT fields. Simultaneously, the individual frames were captured on a separate computer using a frame-grabber system. Synchronization of the individual frames with the integrated images allowed the determination of precisely how the EPID behaved during regular operation as well as when a beam interrupt was triggered. The ability of the EPID to reliably monitor a treatment in the presence of beam interrupts was tested by comparing the difference between the interrupt and non-interrupt images. The interrupted images acquired in integrated acquisition mode displayed unanticipated behaviour in the region of the image where the leaves were located when the beam interrupt was triggered. Differences greater than 5% were observed as a result of the interrupt in some cases, with the discrepancies occurring in a non-uniform manner across the imager. The differences measured were not repeatable from one measurement to another. Examination of the individual frames showed that the EPID was consistently losing a small amount of dose at the termination of every exposure. Inclusion of one additional frame in every image rectified the unexpected behaviour, reducing the differences to 1% or less. Although integrated EPID images nominally capture the entire dose delivered during an exposure, a small amount of dose is consistently being lost at the end of every exposure. The amount of missing dose is random, depending on the exact beam termination time within a frame. Inclusion of an extra frame at the end of each exposure effectively rectifies the problem, making the EPID more suitable for clinical dosimetry applications. The authors received support from Varian Medical Systems in the form of software and equipment loans as well as technical support. © 2012 American Association of Physicists in Medicine.
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Bisht, Sandeep; Pandey, Piyush; Sood, Anchal; Sharma, Shivesh; Bisht, N. S.
2010-01-01
Several naphthalene and anthracene degrading bacteria were isolated from rhizosphere of Populus deltoides, which were growing in non-contaminated soil. Among these, four isolates, i.e. Kurthia sp., Micrococcus varians, Deinococcus radiodurans and Bacillus circulans utilized chrysene, benzene, toluene and xylene, in addition to anthracene and naphthalene. Kurthia sp and B. circulans showed positive chemotactic response for naphthalene and anthracene. The mean growth rate constant (K) of isolates were found to increase with successive increase in substrate concentration (0.5 to 1.0 mg/50ml). B. circulans SBA12 and Kurthia SBA4 degraded 87.5% and 86.6% of anthracene while, Kurthia sp. SBA4, B. circulans SBA12, and M. varians SBA8 degraded 85.3 %, 95.8 % and 86.8 % of naphthalene respectively after 6 days of incubation as determined by HPLC analysis. PMID:24031572
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Source to Skin Distance (SSD) Characteristics from Varian CX Linear Accelerator
NASA Astrophysics Data System (ADS)
Bahari Nurdin, Wira; Purnomo, Aji; Dewang, Syamsir
2018-03-01
This study aims to describe the characteristics of the source to skin distance (SSD) of Varian CX linear accelerator (LINAC) using the X-ray beam of 6 MV and 10 MV. The variation of the source to the SSD are 90, 100 and 110 cms; the depth of the water phantom used are 5, 10, 15, 20, and 25 cms, respectively. The depth of the water phantom was created for analysis of percentage depth dose (PDD) and profile dose. It can be concluded from the tests that from the measured SSD, SSD of 110 cm with the depth water phantom of 20-25 cm for energy beam of 6 MV and at all levels of depth for 10 MV energy corresponding tolerance limits to be used in clinical radiotherapy. For the SSD 90 and 100, the values beam symmetry and flatness obtained slightly beyond the limits of tolerance.
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MRI Artifacts of a Metallic Stent Derived From a Human Aorta Specimen
DOE Office of Scientific and Technical Information (OSTI.GOV)
Soto, M. E.; Flores, P.; Marrufo, O.
Magnetic resonance imaging has proved to be a useful technique to get images of the whole body. However, the presence of ferromagnetic material can cause susceptibility artifacts, which result from microscopic gradients that occur near the boundaries between areas displaying different magnetic susceptibility. These gradients cause dephasing of spins and frequency shifts in the surrounding tissues. Intravoxel dephasing and spatial mis-registration can degrade image quality. An aorta with a metallic stent was preserved in formaldehyde at 10% inside acrylic cylinders and used to obtain MR images. We tested pulsed spin echo and gradient echo sequences to improve image quality. Allmore » experiments were performed on a 7T/21 cm Varian system (Varian, Inc, Palo Alto, CA) equipped with Direct Drive technology and a 16-rung birdcage coil transceiver. The presence of metallic stents produces a lack of signal that might give falsely reassuring appearances within the vessel lumen.« less
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A Monte Carlo model for photoneutron generation by a medical LINAC
NASA Astrophysics Data System (ADS)
Sumini, M.; Isolan, L.; Cucchi, G.; Sghedoni, R.; Iori, M.
2017-11-01
For an optimal tuning of the radiation protection planning, a Monte Carlo model using the MCNPX code has been built, allowing an accurate estimate of the spectrometric and geometrical characteristics of photoneutrons generated by a Varian TrueBeam Stx© medical linear accelerator. We considered in our study a device working at the reference energy for clinical applications of 15 MV, stemmed from a Varian Clinac©2100 modeled starting from data collected thanks to several papers available in the literature. The model results were compared with neutron and photon dose measurements inside and outside the bunker hosting the accelerator obtaining a complete dose map. Normalized neutron fluences were tallied in different positions at the patient plane and at different depths. A sensitivity analysis with respect to the flattening filter material were performed to enlighten aspects that could influence the photoneutron production.
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Kapusta-Duch, Joanna; Leszczyńska, Teresa; Florkiewicz, Adam; Filipiak-Florkiewicz, Agnieszka
2011-01-01
The aim of the present study was to compare lead and cadmium contents in cruciferous vegetables grown under diversified ecological conditions for three consecutive years, independently of the climatic and agrotechnical conditions. The research was conducted in the Cracow region of Poland and tests vegetables near the Steelworks, from ecological farms, and from local markets. The heavy metal contents were determined using the validated Atomic Absorption Spectrometry method, including electrothermal atomization, with an ET-AAS graphite cuvette (Varian AA240Z, made by Varian). Cruciferous vegetables cultivated in the areas surrounding the steelworks were characterized by alarmingly high lead content versus ecological and commercially available vegetables, while the contents of this metal in vegetables from the two latter locations did not differ. It cannot be definitively stated that the origin of vegetables influenced their cadmium content.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
NONE
Deformable image registration has now been commercially available for several years, with solid performance in a number of sites and for several applications including contour and dose mapping. However, more complex applications have arisen, such as assessing response to radiation therapy over time, registering images pre- and post-surgery, and auto-segmentation from atlases. These applications require innovative registration algorithms to achieve accurate alignment. The goal of this session is to highlight emerging registration technology and these new applications. The state of the art in image registration will be presented from an engineering perspective. Translational clinical applications will also be discussed tomore » tie these new registration approaches together with imaging and radiation therapy applications in specific diseases such as cervical and lung cancers. Learning Objectives: To understand developing techniques and algorithms in deformable image registration that are likely to translate into clinical tools in the near future. To understand emerging imaging and radiation therapy clinical applications that require such new registration algorithms. Research supported in part by the National Institutes of Health under award numbers P01CA059827, R01CA166119, and R01CA166703. Disclosures: Phillips Medical systems (Hugo), Roger Koch (Christensen) support, Varian Medical Systems (Brock), licensing agreements from Raysearch (Brock) and Varian (Hugo).; K. Brock, Licensing Agreement - RaySearch Laboratories. Research Funding - Varian Medical Systems; G. Hugo, Research grant from National Institutes of Health, award number R01CA166119.; G. Christensen, Research support from NIH grants CA166119 and CA166703 and a gift from Roger Koch. There are no conflicts of interest.« less
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WE-H-202-04: Advanced Medical Image Registration Techniques
DOE Office of Scientific and Technical Information (OSTI.GOV)
Christensen, G.
Deformable image registration has now been commercially available for several years, with solid performance in a number of sites and for several applications including contour and dose mapping. However, more complex applications have arisen, such as assessing response to radiation therapy over time, registering images pre- and post-surgery, and auto-segmentation from atlases. These applications require innovative registration algorithms to achieve accurate alignment. The goal of this session is to highlight emerging registration technology and these new applications. The state of the art in image registration will be presented from an engineering perspective. Translational clinical applications will also be discussed tomore » tie these new registration approaches together with imaging and radiation therapy applications in specific diseases such as cervical and lung cancers. Learning Objectives: To understand developing techniques and algorithms in deformable image registration that are likely to translate into clinical tools in the near future. To understand emerging imaging and radiation therapy clinical applications that require such new registration algorithms. Research supported in part by the National Institutes of Health under award numbers P01CA059827, R01CA166119, and R01CA166703. Disclosures: Phillips Medical systems (Hugo), Roger Koch (Christensen) support, Varian Medical Systems (Brock), licensing agreements from Raysearch (Brock) and Varian (Hugo).; K. Brock, Licensing Agreement - RaySearch Laboratories. Research Funding - Varian Medical Systems; G. Hugo, Research grant from National Institutes of Health, award number R01CA166119.; G. Christensen, Research support from NIH grants CA166119 and CA166703 and a gift from Roger Koch. There are no conflicts of interest.« less
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Njeh, Christopher F; Salmon, Howard W; Schiller, Claire
2017-01-01
Intensity-modulated radiation therapy (IMRT) delivery using "step-and-shoot" technique on Varian C-Series linear accelerator (linac) is influenced by the communication frequency between the multileaf collimator and linac controllers. Hence, the dose delivery accuracy is affected by the dose rate. Our aim was to quantify the impact of using two dose rates on plan quality assurance (QA). Twenty IMRT patients were selected for this study. The plan QA was measured at two different dose rates. A gamma analysis was performed, and the degree of plan modulation on the QA pass rate was also evaluated in terms of average monitor unit per segment (MU/segment) and the total number of segments. The mean percentage gamma pass rate of 94.9% and 93.5% for 300 MU/min and 600 MU/min dose rate, respectively, was observed. There was a significant ( P = 0.001) decrease in percentage gamma pass rate when the dose rate was increased from 300 MU/min to 600 MU/min. There was a weak, but significant association between the percentage pass rate at both dose rate and total number of segments. The total number of MU was significantly correlated to the total number of segments ( r = 0.59). We found a positive correlation between the percentage pass rate and mean MU/segment, r = 0.52 and r = 0.57 for 300 MU/min and 600 MU/min, respectively. IMRT delivery using step-and-shoot technique on Varian 2300CD is impacted by the dose rate and the total amount of segments.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Sansourekidou, P; Allen, C
2015-06-15
Purpose: To evaluate the Raystation v4.51 Electron Monte Carlo algorithm for Varian Trilogy, IX and 2100 series linear accelerators and commission for clinical use. Methods: Seventy two water and forty air scans were acquired with a water tank in the form of profiles and depth doses, as requested by vendor. Data was imported into Rayphysics beam modeling module. Energy spectrum was modeled using seven parameters. Contamination photons were modeled using five parameters. Source phase space was modeled using six parameters. Calculations were performed in clinical version 4.51 and percent depth dose curves and profiles were extracted to be compared tomore » water tank measurements. Sensitivity tests were performed for all parameters. Grid size and particle histories were evaluated per energy for statistical uncertainty performance. Results: Model accuracy for air profiles is poor in the shoulder and penumbra region. However, model accuracy for water scans is acceptable. All energies and cones are within 2%/2mm for 90% of the points evaluated. Source phase space parameters have a cumulative effect. To achieve distributions with satisfactory smoothness level a 0.1cm grid and 3,000,000 particle histories were used for commissioning calculations. Calculation time was approximately 3 hours per energy. Conclusion: Raystation electron Monte Carlo is acceptable for clinical use for the Varian accelerators listed. Results are inferior to Elekta Electron Monte Carlo modeling. Known issues were reported to Raysearch and will be resolved in upcoming releases. Auto-modeling is limited to open cone depth dose curves and needs expansion.« less
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WE-H-202-03: Accounting for Large Geometric Changes During Radiotherapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hugo, G.
2016-06-15
Deformable image registration has now been commercially available for several years, with solid performance in a number of sites and for several applications including contour and dose mapping. However, more complex applications have arisen, such as assessing response to radiation therapy over time, registering images pre- and post-surgery, and auto-segmentation from atlases. These applications require innovative registration algorithms to achieve accurate alignment. The goal of this session is to highlight emerging registration technology and these new applications. The state of the art in image registration will be presented from an engineering perspective. Translational clinical applications will also be discussed tomore » tie these new registration approaches together with imaging and radiation therapy applications in specific diseases such as cervical and lung cancers. Learning Objectives: To understand developing techniques and algorithms in deformable image registration that are likely to translate into clinical tools in the near future. To understand emerging imaging and radiation therapy clinical applications that require such new registration algorithms. Research supported in part by the National Institutes of Health under award numbers P01CA059827, R01CA166119, and R01CA166703. Disclosures: Phillips Medical systems (Hugo), Roger Koch (Christensen) support, Varian Medical Systems (Brock), licensing agreements from Raysearch (Brock) and Varian (Hugo).; K. Brock, Licensing Agreement - RaySearch Laboratories. Research Funding - Varian Medical Systems; G. Hugo, Research grant from National Institutes of Health, award number R01CA166119.; G. Christensen, Research support from NIH grants CA166119 and CA166703 and a gift from Roger Koch. There are no conflicts of interest.« less
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WE-H-202-02: Biomechanical Modeling of Anatomical Response Over the Course of Therapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Brock, K.
2016-06-15
Deformable image registration has now been commercially available for several years, with solid performance in a number of sites and for several applications including contour and dose mapping. However, more complex applications have arisen, such as assessing response to radiation therapy over time, registering images pre- and post-surgery, and auto-segmentation from atlases. These applications require innovative registration algorithms to achieve accurate alignment. The goal of this session is to highlight emerging registration technology and these new applications. The state of the art in image registration will be presented from an engineering perspective. Translational clinical applications will also be discussed tomore » tie these new registration approaches together with imaging and radiation therapy applications in specific diseases such as cervical and lung cancers. Learning Objectives: To understand developing techniques and algorithms in deformable image registration that are likely to translate into clinical tools in the near future. To understand emerging imaging and radiation therapy clinical applications that require such new registration algorithms. Research supported in part by the National Institutes of Health under award numbers P01CA059827, R01CA166119, and R01CA166703. Disclosures: Phillips Medical systems (Hugo), Roger Koch (Christensen) support, Varian Medical Systems (Brock), licensing agreements from Raysearch (Brock) and Varian (Hugo).; K. Brock, Licensing Agreement - RaySearch Laboratories. Research Funding - Varian Medical Systems; G. Hugo, Research grant from National Institutes of Health, award number R01CA166119.; G. Christensen, Research support from NIH grants CA166119 and CA166703 and a gift from Roger Koch. There are no conflicts of interest.« less
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WE-H-202-01: Memorial Introduction
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kirby, N.
2016-06-15
Deformable image registration has now been commercially available for several years, with solid performance in a number of sites and for several applications including contour and dose mapping. However, more complex applications have arisen, such as assessing response to radiation therapy over time, registering images pre- and post-surgery, and auto-segmentation from atlases. These applications require innovative registration algorithms to achieve accurate alignment. The goal of this session is to highlight emerging registration technology and these new applications. The state of the art in image registration will be presented from an engineering perspective. Translational clinical applications will also be discussed tomore » tie these new registration approaches together with imaging and radiation therapy applications in specific diseases such as cervical and lung cancers. Learning Objectives: To understand developing techniques and algorithms in deformable image registration that are likely to translate into clinical tools in the near future. To understand emerging imaging and radiation therapy clinical applications that require such new registration algorithms. Research supported in part by the National Institutes of Health under award numbers P01CA059827, R01CA166119, and R01CA166703. Disclosures: Phillips Medical systems (Hugo), Roger Koch (Christensen) support, Varian Medical Systems (Brock), licensing agreements from Raysearch (Brock) and Varian (Hugo).; K. Brock, Licensing Agreement - RaySearch Laboratories. Research Funding - Varian Medical Systems; G. Hugo, Research grant from National Institutes of Health, award number R01CA166119.; G. Christensen, Research support from NIH grants CA166119 and CA166703 and a gift from Roger Koch. There are no conflicts of interest.« less
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MO-D-BRB-02: SBRT Treatment Planning and Delivery
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, Y.
2016-06-15
Increased use of SBRT and hypofractionation in radiation oncology practice has posted a number of challenges to medical physicist, ranging from planning, image-guided patient setup and on-treatment monitoring, to quality assurance (QA) and dose delivery. This symposium is designed to provide current knowledge necessary for the safe and efficient implementation of SBRT in various linac platforms, including the emerging digital linacs equipped with high dose rate FFF beams. Issues related to 4D CT, PET and MRI simulations, 3D/4D CBCT guided patient setup, real-time image guidance during SBRT dose delivery using gated/un-gated VMAT/IMRT, and technical advancements in QA of SBRT (inmore » particular, strategies dealing with high dose rate FFF beams) will be addressed. The symposium will help the attendees to gain a comprehensive understanding of the SBRT workflow and facilitate their clinical implementation of the state-of-art imaging and planning techniques. Learning Objectives: Present background knowledge of SBRT, describe essential requirements for safe implementation of SBRT, and discuss issues specific to SBRT treatment planning and QA. Update on the use of multi-dimensional and multi-modality imaging for reliable guidance of SBRT. Discuss treatment planning and QA issues specific to SBRT. Provide a comprehensive overview of emerging digital linacs and summarize the key geometric and dosimetric features of the new generation of linacs for substantially improved SBRT. NIH/NCI; Varian Medical Systems; F. Yin, Duke University has a research agreement with Varian Medical Systems. In addition to research grant, I had a technology license agreement with Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Cardenas, C; The University of Texas Graduate School of Biomedical Sciences, Houston, TX; Nitsch, P
Purpose: To investigate out-of-field electron doses and neutron production from electron beams from modern Varian and Elekta linear accelerators. Methods: Electron dose measurements were made using 10×10cm{sup 2} applicators on two Varian 21iXs, a Varian TrueBeam, and an Elekta Versa HD operating at energies from 6 to 20 MeV. Out-of-field dose profiles and PDD curves were measured in a Wellhofer water phantom using a Farmer chamber. Neutron measurements were made with a combination of moderator buckets and gold activation-foils placed on the treatment couch at various locations in the patient plane on both the 21iX and Versa HD linear accelerators.more » Results: Electron doses were highest for the highest electron energies. Dose profile curves for the Varian units were found to be lower than those from the Versa HD unit, and were lower than photon beams. Elekta’s dose profiles were higher and exhibited a second dose peak around 20–30 cm from central-axis. Electron doses in this region (0.8–1.3% of dmax at central-axis) were close to 5 times (2.5–4.8) greater than doses from photon beams with similar energies. Electron doses decreased sharply with depth before becoming nearly constant; the dose was found to decrease to a depth of approximately E(MeV)/4 in cm. Q-values and neutron dose equivalent increased with energy and were typically higher on central-axis. 18 MV photon beam neutron dose equivalents were greater than any electron beam, being approximately 40 times greater than for the 20 MeV electron beam (21iX). Conclusion: The Versa HD exhibited higher than expected out-of-field electron doses in comparison to typical radiotherapy photon beams. Fortunately, out-of-field electron doses can be substantially reduced by applying a water-equivalent bolus with thickness of E(MeV)/4 in cm. Neutron contamination from clinical electron beams can be considered negligible in relation to photon beams but may need to be considered for special cases. This work was supported by Public Health Service Grant CA180803 awarded by the National Cancer Institute, United States Department of Health and Human Services.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Salinas Aranda, F; Suarez, V; Arbiser, S
2016-06-15
Purpose: To implement an end-to-end QA test of the radiation therapy imaging, planning and delivery process, aimed to assess the dosimetric agreement accuracy between planned and delivered treatment, in order to identify and correct possible sources of deviation. To establish an internal standard for machine commissioning acceptance. Methods: A test involving all steps of the radiation therapy: imaging, planning and delivery process was designed. The test includes analysis of point dose and planar dose distributions agreement between TPS calculated and measured dose. An ad hoc 16 cm diameter PMMA phantom was constructed with one central and four peripheral bores thatmore » can accommodate calibrated electron density inserts. Using Varian Eclipse 10.0 and Elekta XiO 4.50 planning systems, IMRT, RapidArc and 3DCRT with hard and dynamic wedges plans were planned on the phantom and tested. An Exradin A1SL chamber is used with a Keithley 35617EBS electrometer for point dose measurements in the phantom. 2D dose distributions were acquired using MapCheck and Varian aS1000 EPID.Gamma analysis was performed for evaluation of 2D dose distribution agreement using MapCheck software and Varian Portal Dosimetry Application.Varian high energy Clinacs Trilogy, 2100C/CD, 2000CR and low energy 6X/EX where tested.TPS-CT# vs. electron density table were checked for CT-scanners used. Results: Calculated point doses were accurate to 0.127% SD: 0.93%, 0.507% SD: 0.82%, 0.246% SD: 1.39% and 0.012% SD: 0.01% for LoX-3DCRT, HiX-3DCRT, IMRT and RapidArc plans respectively. Planar doses pass gamma 3% 3mm in all cases and 2% 2mm for VMAT plans. Conclusion: Implementation of a simple and reliable quality assurance tool was accomplished. The end-to-end proved efficient, showing excellent agreement between planned and delivered dose evidencing strong consistency of the whole process from imaging through planning to delivery. This test can be used as a first step in beam model acceptance for clinical use.« less
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SU-E-T-370: Measurement of Conical Cone Output Factors for the Varian Edge Linear Accelerator
DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, H; Kim, J; Gordon, J
Purpose: To quantify the impact of detector type, SSD/depth, and intermediate reference on conical cone output factor (OF) measurements for the Varian Edge linac. Methods: OF's for 4, 5, 7.5, 10, 12.5, 15, and 17.5 mm diameter cones relative to 10cmx10cm field were measured for the 6X FFF and 10X FFF energies, with jaws set to 5cmx5cm. Measurements were performed with an Edge diode (0.8mmx0.8mmx0.03mm WxLxT), stereotatic diode SFD, photon diode, CC01 and pinpoint chambers (2mm diameter for both). 95cm SSD/5cm depth were used in a water tank. For the measurement with diodes, OF's were cross-referred to CC13 ion chambermore » measurements with 3cmx3cm field, as recommended, to help mitigate the energy variation in diode response with field size. Results were compared to the representative data from Varian measured with Edge detector. With SFD, OF's at 98.5cm SSD/1.5cm depth and 90cm SSD/10cm depth were also measured. Results: OF's measured with the Edge detector matched within 1.3% (max diff) with the representative data from Varian. For the SFD, OF's matched within 1.3% for the 4, 5 and 17.5 mm cones and within 3.7% for the other cones. OF's with photon diode were within 1.3% except for the 4 and 5 mm cones where they were 8.1% and 3.7%, respectively. OF's for the CC01 and pinpoint chamber deviated up to 36% and 44%, respectively for the 4 mm cone. OF's after intermediate reference with 3cmx3cm field changed by 3.7% for SFD, 0.8% for photon diode, and 0.6% for Edge detector. OF's at 98.5cm SSD/1.5cm depth were 10.8% higher than that at 95cm SSD/5cm depth, and OF's at 90cm SSD/1.5cm depth were 7.5% lower. Conclusion: OF's measured with the Edge detector appear to be reliable. CC01 and pinpoint chambers do not appear suitable for measuring the small cone OF's. SSD/depth affects OF measurements significantly.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Gardner, S; Gulam, M; Song, K
2014-06-01
Purpose: The Varian EDGE machine is a new stereotactic platform, combining Calypso and VisionRT localization systems with a stereotactic linac. The system includes TrueBeam DeveloperMode, making possible the use of XML-scripting for automation of linac-related tasks. This study details the use of DeveloperMode to automate commissioning tasks for Varian EDGE, thereby improving efficiency and measurement consistency. Methods: XML-scripting was used for various commissioning tasks,including couch model verification,beam-scanning,and isocenter verification. For couch measurements, point measurements were acquired for several field sizes (2×2,4×4,10×10cm{sup 2}) at 42 gantry angles for two couch-models. Measurements were acquired with variations in couch position(rails in/out,couch shifted inmore » each of motion axes) compared to treatment planning system(TPS)-calculated values,which were logged automatically through advanced planning interface(API) scripting functionality. For beam scanning, XML-scripts were used to create custom MLC-apertures. For isocenter verification, XML-scripts were used to automate various Winston-Lutz-type tests. Results: For couch measurements, the time required for each set of angles was approximately 9 minutes. Without scripting, each set required approximately 12 minutes. Automated measurements required only one physicist, while manual measurements required at least two physicists to handle linac positions/beams and data recording. MLC apertures were generated outside of the TPS,and with the .xml file format, double-checking without use of TPS/operator console was possible. Similar time efficiency gains were found for isocenter verification measurements Conclusion: The use of XML scripting in TrueBeam DeveloperMode allows for efficient and accurate data acquisition during commissioning. The efficiency improvement is most pronounced for iterative measurements, exemplified by the time savings for couch modeling measurements(approximately 10 hours). The scripting also allowed for creation of the files in advance without requiring access to TPS. The API scripting functionality enabled efficient creation/mining of TPS data. Finally, automation reduces the potential for human error in entering linac values at the machine console,and the script provides a log of measurements acquired for each session. This research was supported in part by a grant from Varian Medical Systems, Palo Alto, CA.« less
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An MCNP-based model of a medical linear accelerator x-ray photon beam.
Ajaj, F A; Ghassal, N M
2003-09-01
The major components in the x-ray photon beam path of the treatment head of the VARIAN Clinac 2300 EX medical linear accelerator were modeled and simulated using the Monte Carlo N-Particle radiation transport computer code (MCNP). Simulated components include x-ray target, primary conical collimator, x-ray beam flattening filter and secondary collimators. X-ray photon energy spectra and angular distributions were calculated using the model. The x-ray beam emerging from the secondary collimators were scored by considering the total x-ray spectra from the target as the source of x-rays at the target position. The depth dose distribution and dose profiles at different depths and field sizes have been calculated at a nominal operating potential of 6 MV and found to be within acceptable limits. It is concluded that accurate specification of the component dimensions, composition and nominal accelerating potential gives a good assessment of the x-ray energy spectra.
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Ford Motor Company NDE facility shielding design.
Metzger, Robert L; Van Riper, Kenneth A; Jones, Martin H
2005-01-01
Ford Motor Company proposed the construction of a large non-destructive evaluation laboratory for radiography of automotive power train components. The authors were commissioned to design the shielding and to survey the completed facility for compliance with radiation doses for occupationally and non-occupationally exposed personnel. The two X-ray sources are Varian Linatron 3000 accelerators operating at 9-11 MV. One performs computed tomography of automotive transmissions, while the other does real-time radiography of operating engines and transmissions. The shield thickness for the primary barrier and all secondary barriers were determined by point-kernel techniques. Point-kernel techniques did not work well for skyshine calculations and locations where multiple sources (e.g. tube head leakage and various scatter fields) impacted doses. Shielding for these areas was determined using transport calculations. A number of MCNP [Briesmeister, J. F. MCNPCA general Monte Carlo N-particle transport code version 4B. Los Alamos National Laboratory Manual (1997)] calculations focused on skyshine estimates and the office areas. Measurements on the operational facility confirmed the shielding calculations.
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Conceptual Study of LSTAT Integration to Robotics and Other Advanced Medical Technologies
2004-07-31
Robotic Manipulators............................................................................... 37 3.2.4 Digital X -ray...11 Figure 7 OEC 9800 digital x -ray system (GE Healthcare) ....................................................... 21 Figure 8 portable...digital x -ray equipment (Varian, Inc.) ........................................................... 22 Figure 9 Portable ultrasound units
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Brunner, Stephen; Nett, Brian E; Tolakanahalli, Ranjini; Chen, Guang-Hong
2011-02-21
X-ray scatter is a significant problem in cone-beam computed tomography when thicker objects and larger cone angles are used, as scattered radiation can lead to reduced contrast and CT number inaccuracy. Advances have been made in x-ray computed tomography (CT) by incorporating a high quality prior image into the image reconstruction process. In this paper, we extend this idea to correct scatter-induced shading artifacts in cone-beam CT image-guided radiation therapy. Specifically, this paper presents a new scatter correction algorithm which uses a prior image with low scatter artifacts to reduce shading artifacts in cone-beam CT images acquired under conditions of high scatter. The proposed correction algorithm begins with an empirical hypothesis that the target image can be written as a weighted summation of a series of basis images that are generated by raising the raw cone-beam projection data to different powers, and then, reconstructing using the standard filtered backprojection algorithm. The weight for each basis image is calculated by minimizing the difference between the target image and the prior image. The performance of the scatter correction algorithm is qualitatively and quantitatively evaluated through phantom studies using a Varian 2100 EX System with an on-board imager. Results show that the proposed scatter correction algorithm using a prior image with low scatter artifacts can substantially mitigate scatter-induced shading artifacts in both full-fan and half-fan modes.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Heintz, P; Heintz, B; Sandoval, D
Purpose: Computerized radiation therapy treatment planning is performed on almost all patients today. However it is seldom used for laboratory irradiations. The first objective is to assess whether modern radiation therapy treatment planning (RTP) systems accurately predict the subject dose by comparing in vivo and decedent dose measurements to calculated doses. The other objective is determine the importance of using a RTP system for laboratory irradiations. Methods: 5 MOSFET radiation dosimeters were placed enterically in each subject (2 sedated Rhesus Macaques) to measure the absorbed dose at 5 levels (carina, lung, heart, liver and rectum) during whole body irradiation. Themore » subjects were treated with large opposed lateral fields and extended distances to cover the entire subject using a Varian 600C linac. CT simulation was performed ante-mortem (AM) and post-mortem (PM). To compare AM and PM doses, calculation points were placed at the location of each dosimeter in the treatment plan. The measured results were compared to the results using Varian Eclipse and Prowess Panther RTP systems. Results: The Varian and Prowess treatment planning system agreed to within in +1.5% for both subjects. However there were significant differences between the measured and calculated doses. For both animals the calculated central axis dose was higher than prescribed by 3–5%. This was caused in part by inaccurate measurement of animal thickness at the time of irradiation. For one subject the doses ranged from 4% to 7% high and the other subject the doses ranged 7% to 14% high when compared to the RTP doses. Conclusions: Our results suggest that using proper CT RTP system can more accurately deliver the prescribed dose to laboratory subjects. It also shows that there is significant dose variation in such subjects when inhomogeneities are not considered in the planning process.« less
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Scannell, Amalia G M; Kenneally, Paul M; Arendt, Elke K
2004-06-01
Porcine longissimus dorsi muscles were cured by brine injection. Curing brine containing 15% (w/v) NaCl, 1.33% (w/v) glucose, 750 ppm sodium nitrite, and appropriate levels of either Lactobacillus sakei LAD, L. sakei LAD plus Kocuria varians FT4 (formally Micrococcus varians), L. sakei LAD plus papain and GDL (glucono-delta-lactone) plus K. varians FT4, was injected to the muscle at a pumping rate 15% w/v. The effect of these treatments on the proteolysis in the ham system was compared to a control ham, produced without starter culture and containing GDL acidulant to control pH and antibiotics to reduce the contribution of background microflora. Hydrolysis of sarcoplasmic and myofibrillar protein fractions was evaluated by SDS-PAGE and reverse phase-HPLC. Hams with different treatments were also investigated for differences in amino acid profile, protein and non-protein nitrogen level, colour, pH, water activity and moisture and microbiological evolution. There was no significant difference in the gross compositional analysis of any of the treatments compared to the control. There was no significant difference (p>0.05) in the protein content, non-protein nitrogen level, SDS-PAGE and free amino acid analysis between the control ham and ham inoculated with proteolytic starter culture. However, it was observed that hams containing starter cultures exhibited decreases in certain peptide fractions and corresponding increases in some free amino acids compared to the uninoculated control. It can be concluded that, while the principle mechanisms resulting in the proteolysis of this non-dried ham product involve the activity of endogeneous cathepsins, the addition of proteolytic starter cultures influence the amino acid profile thereby potentially enhancing the sensorial attributes of the ham. Copyright 2004 Elsevier B.V.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jiang, Runqing; Zhan, Lixin; Osei, Ernest
2014-08-15
Volumetric modulated arc therapy (VMAT) allows fast delivery of stereotactic radiotherapy. However, the discrepancies between the calculated and delivered dose distributions due to respiratory motion and dynamic multileaf collimators (MLCs) interplay are not avoidable. The purpose of this study is to investigate RapidArc lung SBRT treatment delivered by the flattening filter-free (FFF) beam and flattened beam with Varian TrueBeam machine. CIRS Dynamic Thorax Phantom with in-house made lung tumor insertion was CT scanned both in free breathing and 4DCT. 4DCT was used to determine the internal target volume. The free breathing CT scan was used for treatment planning. A 5more » mm margin was given to ITV to generate a planning target volume. Varian Eclipse treatment planning was used to generate RapidArc plans based on the 6 MV flattened beam and 6MV FFF beam. The prescription dose was 48 Gy in 4 fractions. At least 95% of PTV was covered by the prescribed dose. The RapidArc plans with 6 MV flattened beam and 6MV FFF beam were delivered with Varian TrueBeam machine. The dosimetric measurements were performed with Gafchromic XR-RV3 film, which was placed in the lung tumor insertion. The interplay between the dynamic MLC-based delivery of VMAT and the respiratory motion of the tumor degraded target coverage and created undesired hot or cold dose spots inside the lung tumor. Lung SBRT RapidArc treatments delivered by the FFF beam of TrueBeam linear accelerator is superior to the flattened beam. Further investigation will be performed by Monte Carlo simulation.« less
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González-Ortegón, E; Walton, M E M; Moghaddam, B; Vilas, C; Prieto, A; Kennedy, H A; Pedro Cañavate, J; Le Vay, L
2015-01-15
In a restored wetland (South of Spain), where different flow regimes control water exchange with the adjacent Guadalquivir estuary, the native Palaemon varians coexists with an exotic counterpart species Palaemon macrodactylus. This controlled m\\acrocosm offers an excellent opportunity to investigate how the effects of water management, through different flow regimes, and the presence of a non-native species affect the aquatic community and the trophic niche (by gut contents and C-N isotopic composition) of the native shrimp Palaemon varians. We found that increased water exchange rate (5% day(-1) in mixed ponds vs. 0.1% day(-1) in extensive ponds) modified the aquatic community of this wetland; while extensive ponds are dominated by isopods and amphipods with low presence of P. macrodactylus, mixed ponds presented high biomass of mysids, corixids, copepods and both shrimp species. An estuarine origin of nutrients and primary production might explain seasonal and spatial differences found among ponds of this wetland. A combined analysis of gut contents and isotopic composition of the native and the exotic species showed that: (1) native P. varians is mainly omnivorous (2) while the non-native P. macrodactylus is more zooplanktivorous and (3) a dietary overlap occurred when both species coexist at mixed ponds where a higher water exchange and high abundance of mysids and copepods diversifies the native species' diet. Thus differences in the trophic ecology of both species are clearly explained by water management. This experimental study is a valuable tool for integrated management between river basin and wetlands since it allows quantification of wetland community changes in response to the flow regime. Copyright © 2014 Elsevier B.V. All rights reserved.
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NASA Astrophysics Data System (ADS)
Jung, Hyunuk; Shin, Jungsuk; Chung, Kwangzoo; Han, Youngyih; Kim, Jinsung; Choi, Doo Ho
2015-05-01
The aim of this study was to develop an independent dose verification system by using a Monte Carlo (MC) calculation method for intensity modulated radiation therapy (IMRT) conducted by using a Varian Novalis Tx (Varian Medical Systems, Palo Alto, CA, USA) equipped with a highdefinition multi-leaf collimator (HD-120 MLC). The Geant4 framework was used to implement a dose calculation system that accurately predicted the delivered dose. For this purpose, the Novalis Tx Linac head was modeled according to the specifications acquired from the manufacturer. Subsequently, MC simulations were performed by varying the mean energy, energy spread, and electron spot radius to determine optimum values of irradiation with 6-MV X-ray beams by using the Novalis Tx system. Computed percentage depth dose curves (PDDs) and lateral profiles were compared to the measurements obtained by using an ionization chamber (CC13). To validate the IMRT simulation by using the MC model we developed, we calculated a simple IMRT field and compared the result with the EBT3 film measurements in a water-equivalent solid phantom. Clinical cases, such as prostate cancer treatment plans, were then selected, and MC simulations were performed. The accuracy of the simulation was assessed against the EBT3 film measurements by using a gamma-index criterion. The optimal MC model parameters to specify the beam characteristics were a 6.8-MeV mean energy, a 0.5-MeV energy spread, and a 3-mm electron radius. The accuracy of these parameters was determined by comparison of MC simulations with measurements. The PDDs and the lateral profiles of the MC simulation deviated from the measurements by 1% and 2%, respectively, on average. The computed simple MLC fields agreed with the EBT3 measurements with a 95% passing rate with 3%/3-mm gamma-index criterion. Additionally, in applying our model to clinical IMRT plans, we found that the MC calculations and the EBT3 measurements agreed well with a passing rate of greater than 95% on average with a 3%/3-mm gamma-index criterion. In summary, the Novalis Tx Linac head equipped with a HD-120 MLC was successfully modeled by using a Geant4 platform, and the accuracy of the Geant4 platform was successfully validated by comparisons with measurements. The MC model we have developed can be a useful tool for pretreatment quality assurance of IMRT plans and for commissioning of radiotherapy treatment planning.
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NASA Astrophysics Data System (ADS)
Hagan, Aaron; Sawant, Amit; Folkerts, Michael; Modiri, Arezoo
2018-01-01
We report on the design, implementation and characterization of a multi-graphic processing unit (GPU) computational platform for higher-order optimization in radiotherapy treatment planning. In collaboration with a commercial vendor (Varian Medical Systems, Palo Alto, CA), a research prototype GPU-enabled Eclipse (V13.6) workstation was configured. The hardware consisted of dual 8-core Xeon processors, 256 GB RAM and four NVIDIA Tesla K80 general purpose GPUs. We demonstrate the utility of this platform for large radiotherapy optimization problems through the development and characterization of a parallelized particle swarm optimization (PSO) four dimensional (4D) intensity modulated radiation therapy (IMRT) technique. The PSO engine was coupled to the Eclipse treatment planning system via a vendor-provided scripting interface. Specific challenges addressed in this implementation were (i) data management and (ii) non-uniform memory access (NUMA). For the former, we alternated between parameters over which the computation process was parallelized. For the latter, we reduced the amount of data required to be transferred over the NUMA bridge. The datasets examined in this study were approximately 300 GB in size, including 4D computed tomography images, anatomical structure contours and dose deposition matrices. For evaluation, we created a 4D-IMRT treatment plan for one lung cancer patient and analyzed computation speed while varying several parameters (number of respiratory phases, GPUs, PSO particles, and data matrix sizes). The optimized 4D-IMRT plan enhanced sparing of organs at risk by an average reduction of 26% in maximum dose, compared to the clinical optimized IMRT plan, where the internal target volume was used. We validated our computation time analyses in two additional cases. The computation speed in our implementation did not monotonically increase with the number of GPUs. The optimal number of GPUs (five, in our study) is directly related to the hardware specifications. The optimization process took 35 min using 50 PSO particles, 25 iterations and 5 GPUs.
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Hagan, Aaron; Sawant, Amit; Folkerts, Michael; Modiri, Arezoo
2018-01-16
We report on the design, implementation and characterization of a multi-graphic processing unit (GPU) computational platform for higher-order optimization in radiotherapy treatment planning. In collaboration with a commercial vendor (Varian Medical Systems, Palo Alto, CA), a research prototype GPU-enabled Eclipse (V13.6) workstation was configured. The hardware consisted of dual 8-core Xeon processors, 256 GB RAM and four NVIDIA Tesla K80 general purpose GPUs. We demonstrate the utility of this platform for large radiotherapy optimization problems through the development and characterization of a parallelized particle swarm optimization (PSO) four dimensional (4D) intensity modulated radiation therapy (IMRT) technique. The PSO engine was coupled to the Eclipse treatment planning system via a vendor-provided scripting interface. Specific challenges addressed in this implementation were (i) data management and (ii) non-uniform memory access (NUMA). For the former, we alternated between parameters over which the computation process was parallelized. For the latter, we reduced the amount of data required to be transferred over the NUMA bridge. The datasets examined in this study were approximately 300 GB in size, including 4D computed tomography images, anatomical structure contours and dose deposition matrices. For evaluation, we created a 4D-IMRT treatment plan for one lung cancer patient and analyzed computation speed while varying several parameters (number of respiratory phases, GPUs, PSO particles, and data matrix sizes). The optimized 4D-IMRT plan enhanced sparing of organs at risk by an average reduction of [Formula: see text] in maximum dose, compared to the clinical optimized IMRT plan, where the internal target volume was used. We validated our computation time analyses in two additional cases. The computation speed in our implementation did not monotonically increase with the number of GPUs. The optimal number of GPUs (five, in our study) is directly related to the hardware specifications. The optimization process took 35 min using 50 PSO particles, 25 iterations and 5 GPUs.
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U.S. EPA High-Field NMR Facility with Remote Accessibility
EPA’s High-Field Nuclear Magnetic Resonance Research Facility housed in Athens, GA has two Varian 600 MHz NMR spectrometers used for conducting sophisticated experiments in environmental science. Off-site users can ship their samples and perform their NMR experiments remotely fr...
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Szczerba, Izabela; Krzemiński, Zbigniew
2002-01-01
The aim of the study was to assess the prevalence of different bacteria in the oral cavity. The bacteria were present in the oral cavities of 73 (48.7%) of 150 individuals. Nesterenkonia halobia, the most frequently isolated species, was found in 20 (27%) individuals, Micrococcus luteus in 16 (22%), Kocuria kristinae in 12 (16%), Kocuria varians in 10 (14%), Dermacoccus sedentarius in 9 (12%), Micrococcus lylae in 8 (11%), and Kytococcus nishinomiyaensis in 3 (4%). Mean counts of these microorganisms were relatively low and amounted in log10 CFU/ml saliva for M. luteus 1.87 +/- 0.52, for M. lylae 2.03 +/- 0.39, for N. halobia 2.14 +/- 0.56, for K. kristinae 2.20 +/- 0.69, for K. varians 2.19 +/- 0.67, for K. nishinomiyaensis 1.72 +/- 0.39, and for D. sedentarius 2.27 +/- 0.55. The factor limiting the population sizes of these microorganisms was most probably the antagonistic activity of the bacteria living in oral cavity.
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New method for estimation of fluence complexity in IMRT fields and correlation with gamma analysis
NASA Astrophysics Data System (ADS)
Hanušová, T.; Vondráček, V.; Badraoui-Čuprová, K.; Horáková, I.; Koniarová, I.
2015-01-01
A new method for estimation of fluence complexity in Intensity Modulated Radiation Therapy (IMRT) fields is proposed. Unlike other previously published works, it is based on portal images calculated by the Portal Dose Calculation algorithm in Eclipse (version 8.6, Varian Medical Systems) in the plane of the EPID aS500 detector (Varian Medical Systems). Fluence complexity is given by the number and the amplitudes of dose gradients in these matrices. Our method is validated using a set of clinical plans where fluence has been smoothed manually so that each plan has a different level of complexity. Fluence complexity calculated with our tool is in accordance with the different levels of smoothing as well as results of gamma analysis, when calculated and measured dose matrices are compared. Thus, it is possible to estimate plan complexity before carrying out the measurement. If appropriate thresholds are determined which would distinguish between acceptably and overly modulated plans, this might save time in the re-planning and re-measuring process.
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SU-F-T-258: Efficacy of Exit Fluence-Based Dose Calculation for Prostate Radiation Therapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Siebers, J; Gardner, J; Neal, B
Purpose: To investigate the efficacy of exit-fluence-based dose computation for prostate radiotherapy by determining if it estimates true dose more accurately than the original planning dose. Methods: Virtual exit-fluencebased dose computation was performed for 19 patients, each with 9–12 repeat CT images. For each patient, a 78 Gy treatment plan was created utilizing 5 mm CTV-to-PTV and OAR-to-PRV margins. A Monte Carlo framework was used to compute dose and exit-fluence images for the planning image and for each repeat CT image based on boney-anatomyaligned and prostate-centroid-aligned CTs. Identical source particles were used for the MC dose-computations on the planning andmore » repeat CTs to maximize correlation. The exit-fluence-based dose and image were computed by multiplying source particle weights by FC(x,y)=FP(x,y)/FT(x,y), where (x,y) are the source particle coordinates projected to the exit-fluence plane and we denote the dose/fluence from the plan by (DP,FP), from the repeat-CT as (DT,FT), and the exit-fluence computation by (DFC,FFC). DFC mimics exit-fluence backprojection through the planning image as FT=FFC. Dose estimates were intercompared to judge the efficacy of exit-fluence-based dose computation. Results: Boney- and prostate-centroid aligned results are combined as there is no statistical difference between them, yielding 420 dose comparisons per dose-volume metric. DFC is more accurate than DP for 46%, 33%, and 44% of cases in estimating CTV D98, D50, and D2 respectively. DFC improved rectum D50 and D2 estimates 54% and 49% respectively and bladder D50 and D2 47 and 49% respectively. While averaged over all patients and images DFC and DP were within 3.1% of DT, they differed from DT by as much as 22% for GTV D98, 71% for the Bladder D50, 17% for Bladder D2, 19% for Rectum D2. Conclusion: Exit-fluence based dose computations infrequently improve CTV or OAR dose estimates and should be used with caution. Research supported in part by Varian Medical Systems.« less
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Characterization of grape Gibberellin Insensitive 1 mutant alleles in transgenic Arabidopsis
USDA-ARS?s Scientific Manuscript database
We generated a dozen of different mutations in the grape Gibberellin Insensitive or GAI sequence, transformed them into Arabidopsis under the control of 35S, Arabidopsis or grape GAI promoter, and evaluated the impact of these mutant alleles on plant growth and development. These GAI sequence varian...
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NASA Astrophysics Data System (ADS)
Conver, Timothy S.; Koropchak, John A.
1995-06-01
This paper describes detailed work done in our lab to compare analytical figures of merit for pneumatic, ultrasonic and thermospray sample introduction (SI) systems with three different inductively coupled plasma-atomic emission spectrometry (ICP-AES) instruments. One instrument from Leeman Labs, Inc. has an air path echelle spectrometer and a 27 MHz ICP. For low dissolved solid samples with this instrument, we observed that the ultrasonic nebulizer (USN) and fused silica aperture thermospray (FSApT) both offered similar LOD improvements as compared to pneumatic nebulization (PN), 14 and 16 times, respectively. Average sensitivities compared to PN were better for the USN, by 58 times, compared to 39 times for the FSApT. For solutions containing high dissolved solids we observed that FSApT optimized at the same conditions as for low dissolved solids, whereas USN required changes in power and gas flows to maintain a stable discharge. These changes degraded the LODs for USN substantially as compared to those utilized for low dissolved solid solutions, limiting improvement compared to PN to an average factor of 4. In general, sensitivities for USN were degraded at these new conditions. When solutions with 3000 μg/g Ca were analyzed, LOD improvements were smaller for FSApT and USN, but FSApT showed an improvement over USN of 6.5 times. Sensitivities compared to solutions without high dissolved solids were degraded by 19% on average for FSApT, while those for USN were degraded by 26%. The SI systems were also tested with a Varian Instruments Liberty 220 having a vacuum path Czerny-Turner monochromator and a 40 MHz generator. The sensitivities with low dissolved solids solutions compared to PN were 20 times better for the USN and 39 times better for FSApT, and LODs for every element were better for FSApT. Better correlation between relative sensitivities and anticipated relative analyte mass fluxes for FSApT and USN was observed with the Varian instrument. LOD improvements averaged 18 times lower than PN with FSApT while with USN values averaged 8 times lower. When solutions with high dissolved solids were studied it was found that FSApT still offered 5.5 times better LODs than PN and USN offered 4.6 times better LODs than PN. Sensitivities for FSApT averaged 20 times better, while those for USN were 13 times better compared to PN. Finally, background RSDs on the Varian system were generally higher for FSApT than for the USN for similar sample types. A third instrument used for a small set of elements was a Perkin-Elmer model 5500 ICP-AES. This system has a 27 MHz generator with a N 2 purged Czerny-Turner monochromator. LOD trends, background RSDs, and sensitivities were similar to those with the Leeman instrument. However, matrix effects more closely resembled those seen with the Varian instrument for both SI systems. To compare performance and recoveries on a real sample, a National Institute of Standards and Technology, Standard Reference Material 1643c trace elements in water, was analyzed using the Varian system and it was found that both SI systems offered similar recoveries.
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Martin, Colin J; Abuhaimed, Abdullah; Sankaralingam, Marimuthu; Metwaly, Mohamed; Gentle, David J
2016-06-01
Cone beam computed tomography (CBCT) systems are fitted to radiotherapy linear accelerators and used for patient positioning prior to treatment by image guided radiotherapy (IGRT). Radiotherapists' and radiographers' knowledge of doses to organs from CBCT imaging is limited. The weighted CT dose index for a reference beam of width 20 mm (CTDIw,ref) is displayed on Varian CBCT imaging equipment known as an On-Board Imager (OBI) linked to the Truebeam linear accelerator. This has the potential to provide an indication of organ doses. This knowledge would be helpful for guidance of radiotherapy clinicians preparing treatments. Monte Carlo simulations of imaging protocols for head, thorax and pelvic scans have been performed using EGSnrc/BEAMnrc, EGSnrc/DOSXYZnrc, and ICRP reference computational male and female phantoms to derive the mean absorbed doses to organs and tissues, which have been compared with values for the CTDIw,ref displayed on the CBCT scanner console. Substantial variations in dose were observed between male and female phantoms. Nevertheless, the CTDIw,ref gave doses within ±21% for the stomach and liver in thorax scans and 2 × CTDIw,ref can be used as a measure of doses to breast, lung and oesophagus. The CTDIw,ref could provide indications of doses to the brain for head scans, and the colon for pelvic scans. It is proposed that knowledge of the link between CTDIw for CBCT should be promoted and included in the training of radiotherapy staff.
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Development of a patient-specific 3D dose evaluation program for QA in radiation therapy
NASA Astrophysics Data System (ADS)
Lee, Suk; Chang, Kyung Hwan; Cao, Yuan Jie; Shim, Jang Bo; Yang, Dae Sik; Park, Young Je; Yoon, Won Sup; Kim, Chul Yong
2015-03-01
We present preliminary results for a 3-dimensional dose evaluation software system ( P DRESS, patient-specific 3-dimensional dose real evaluation system). Scanned computed tomography (CT) images obtained by using dosimetry were transferred to the radiation treatment planning system (ECLIPSE, VARIAN, Palo Alto, CA) where the intensity modulated radiation therapy (IMRT) nasopharynx plan was designed. We used a 10 MV photon beam (CLiX, VARIAN, Palo Alto, CA) to deliver the nasopharynx treatment plan. After irradiation, the TENOMAG dosimeter was scanned using a VISTA ™ scanner. The scanned data were reconstructed using VistaRecon software to obtain a 3D dose distribution of the optical density. An optical-CT scanner was used to readout the dose distribution in the gel dosimeter. Moreover, we developed the P DRESS by using Flatform, which were developed by our group, to display the 3D dose distribution by loading the DICOM RT data which are exported from the radiotherapy treatment plan (RTP) and the optical-CT reconstructed VFF file, into the independent P DRESS with an ioniz ation chamber and EBT film was used to compare the dose distribution calculated from the RTP with that measured by using a gel dosimeter. The agreement between the normalized EBT, the gel dosimeter and RTP data was evaluated using both qualitative and quantitative methods, such as the isodose distribution, dose difference, point value, and profile. The profiles showed good agreement between the RTP data and the gel dosimeter data, and the precision of the dose distribution was within ±3%. The results from this study showed significantly discrepancies between the dose distribution calculated from the treatment plan and the dose distribution measured by a TENOMAG gel and by scanning with an optical CT scanner. The 3D dose evaluation software system ( P DRESS, patient specific dose real evaluation system), which were developed in this study evaluates the accuracies of the three-dimensional dose distributions. Further applications of the system utility are expected to result from future studies.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Santoso, A; Song, K; Gardner, S
Purpose: 4D-CBCT facilitates assessment of tumor motion at treatment position. We investigated the effect of gantry speed on 4D-CBCT image quality and dose using the Varian Edge On-Board Imager (OBI). Methods: A thoracic protocol was designed using a 125 kVp spectrum. Image quality parameters were obtained via 4D acquisition using a Catphan phantom with a gating system. A sinusoidal waveform was executed with a five second period and superior-inferior motion. 4D-CBCT scans were sorted into 4 and 10 phases. Image quality metrics included spatial resolution, contrast-to-noise ratio (CNR), uniformity index (UI), Hounsfield unit (HU) sensitivity, and RMS error (RMSE) ofmore » motion amplitude. Dosimetry was accomplished using Gafchromic XR-QA2 films within a CIRS Thorax phantom. This was placed on the gating phantom using the same motion waveform. Results: High contrast resolution decreased linearly from 5.93 to 4.18 lp/cm, 6.54 to 4.18 lp/cm, and 5.19 to 3.91 lp/cm for averaged, 4 phase, and 10 phase 4DCBCT volumes respectively as gantry speed increased from 1.0 to 6.0 degs/sec. CNRs decreased linearly from 4.80 to 1.82 as the gantry speed increased from 1.0 to 6.0 degs/sec, respectively. No significant variations in UIs, HU sensitivities, or RMSEs were observed with variable gantry speed. Ion chamber measurements compared to film yielded small percent differences in plastic water regions (0.1–9.6%), larger percent differences in lung equivalent regions (7.5–34.8%), and significantly larger percent differences in bone equivalent regions (119.1–137.3%). Ion chamber measurements decreased from 17.29 to 2.89 cGy with increasing gantry speed from 1.0 to 6.0 degs/sec. Conclusion: Maintaining technique factors while changing gantry speed changes the number of projections used for reconstruction. Increasing the number of projections by decreasing gantry speed decreases noise, however, dose is increased. The future of 4DCBCT’s clinical utility relies on further investigation of image optimization.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jiang, X; Fox, T; Schreibmann, E
2014-06-15
Purpose: To create a non-supervised quality assurance program to monitor image-based patient setup. The system acts a secondary check by independently computing shifts and rotations and interfaces with Varian's database to verify therapist's work and warn against sub-optimal setups. Methods: Temporary digitally-reconstructed radiographs (DRRs) and OBI radiographic image files created by Varian's treatment console during patient setup are intercepted and used as input in an independent registration module customized for accuracy that determines the optimal rotations and shifts. To deal with the poor quality of OBI images, a histogram equalization of the live images to the DDR counterparts is performedmore » as a pre-processing step. A search for the most sensitive metric was performed by plotting search spaces subject to various translations and convergence analysis was applied to ensure the optimizer finds the global minima. Final system configuration uses the NCC metric with 150 histogram bins and a one plus one optimizer running for 2000 iterations with customized scales for translations and rotations in a multi-stage optimization setup that first corrects and translations and subsequently rotations. Results: The system was installed clinically to monitor and provide almost real-time feedback on patient positioning. On a 2 month-basis uncorrected pitch values were of a mean 0.016° with standard deviation of 1.692°, and couch rotations of − 0.090°± 1.547°. The couch shifts were −0.157°±0.466° cm for the vertical, 0.045°±0.286 laterally and 0.084°± 0.501° longitudinally. Uncorrected pitch angles were the most common source of discrepancies. Large variations in the pitch angles were correlated with patient motion inside the mask. Conclusion: A system for automated quality assurance of therapist's registration was designed and tested in clinical practice. The approach complements the clinical software's automated registration in terms of algorithm configuration and performance and constitutes a practical approach to implement safe and cost-effective radiotherapy.« less
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Abraham, S; Fogliata, A; Jordaan, A; Clivio, A; Vanetti, E; Cozzi, L
2013-01-01
Objective: To evaluate the use of volumetric-modulated arc therapy [VMAT, RapidArc® (RA); Varian Medical Systems, Palo Alto, CA] for the treatment of cutaneous Kaposi’s sarcoma (KS) of lower extremities with adequate target coverage and high bone sparing, and to compare VMAT with electron beam therapy. Methods: 10 patients were planned with either RA or electron beams. The dose was prescribed to 30 Gy, 10 fractions, to mean the planning target volume (PTV), and significant maximum dose to bone was limited to 30 Gy. Plans were designed for 6-MV photon beams for RA and 6 MeV for electrons. Dose distributions were computed with AcurosXB® (Varian Medical Systems) for photons and with a Monte Carlo algorithm for electrons. Results: V90% was 97.3±1.2 for RA plans and 78.2±2.6 for electrons; similarly, V107% was 2.5±2.2 and 37.7±3.4, respectively. RA met coverage criteria. Concerning bone sparing, D2% was 29.6±1.1 for RA and 31.0±2.4 for electrons. Although acceptable for bone involvement, pronounced target coverage violations were obtained for electron plans. Monitor units were similar for electrons and RA, although for the latter they increased when superior bone sparing was imposed. Delivery times were 12.1±4.0 min for electrons and 4.8±1.3 min for the most modulated RA plans. Conclusion: High plan quality was shown for KS in the lower extremities using VMAT, and this might simplify their management in comparison with the more conventional usage of electrons, particularly in institutes with limited staff resources and heavy workloads. Advances in knowledge: VMAT is also dosimetrically extremely advantageous in a typology of treatments where electron beam therapy is mainly considered to be effective owing to the limited penetration of the beams. PMID:23392192
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TH-CD-207A-04: Optimized Respiratory Gating for Abnormal Breathers in Pancreatic SBRT
DOE Office of Scientific and Technical Information (OSTI.GOV)
Campbell, W; Miften, M; Schefter, T
Purpose: Pancreatic SBRT is uniquely challenging due to both the erratic/unstable motion of the pancreas and the close proximity of the radiosensitive small bowel. Respiratory gating can mitigate this effect, but the irregularity of motion severely affects traditional phase-based gating. The purpose of this study was to analyze real-time motion data of pancreatic tumors to optimize the efficacy and accuracy of respiratory gating, with the overall goal of enabling dose escalated pancreatic SBRT. Methods: Fifteen pancreatic SBRT patients received 30–33 Gy in 5 fractions on a Varian TrueBeam STx unit. Abdominal compression was used to reduce the amplitude of tumormore » motion, and daily cone-beam computed tomography (CBCT) scans were acquired prior to each treatment for target localization purposes. For this study, breathing data (phase and amplitude) were collected during each CBCT scan using Varian’s Real-Time Position Management system. An in-house template matching technique was used to track the superior-inferior motion of implanted fiducial markers in CBCT projection images. Using tumor motion and breathing data, phase-based or amplitude-based respiratory gating was simulated for all 75 fractions, targeting either end-exhalation or end-inhalation phases of breathing. Results: For the average patient, gating at end-exhalation offered the best reductions in effective motion for equal duty cycles. However, optimal central phase angle varied widely (range: 0–92%, mean±SD: 49±12%), and phase-based gating windows typically associated with end-exhalation (i.e., “30–70%”) were rarely ideal. Amplitude-based gating significantly outperformed phase-based gating, with average effective ranges for amplitude-based gating 25% lower than phase-based gating ranges (as much as 73% lower). Amplitude-based gating was consistently better suited to accommodate abnormal breathing patterns. For both phase-based and amplitude-based gating, end-exhalation provided significantly better results than end-inhalation. Conclusion: Amplitude-based gating reliably outperformed phase-based gating, and end-exhalation was more suitable than end-inhalation. These results will be used to guide future dose-escalation trials. Research funding provided by Varian Medical Systems to Miften and Jones.« less
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SU-F-BRB-05: Collision Avoidance Mapping Using Consumer 3D Camera
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cardan, R; Popple, R
2015-06-15
Purpose: To develop a fast and economical method of scanning a patient’s full body contour for use in collision avoidance mapping without the use of ionizing radiation. Methods: Two consumer level 3D cameras used in electronic gaming were placed in a CT simulator room to scan a phantom patient set up in a high collision probability position. A registration pattern and computer vision algorithms were used to transform the scan into the appropriate coordinate systems. The cameras were then used to scan the surface of a gantry in the treatment vault. Each scan was converted into a polygon mesh formore » collision testing in a general purpose polygon interference algorithm. All clinically relevant transforms were applied to the gantry and patient support to create a map of all possible collisions. The map was then tested for accuracy by physically testing the collisions with the phantom in the vault. Results: The scanning fidelity of both the gantry and patient was sufficient to produce a collision prediction accuracy of 97.1% with 64620 geometry states tested in 11.5 s. The total scanning time including computation, transformation, and generation was 22.3 seconds. Conclusion: Our results demonstrate an economical system to generate collision avoidance maps. Future work includes testing the speed of the framework in real-time collision avoidance scenarios. Research partially supported by a grant from Varian Medical Systems.« less
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A novel electron gun for inline MRI-linac configurations.
Constantin, Dragoş E; Holloway, Lois; Keall, Paul J; Fahrig, Rebecca
2014-02-01
This work introduces a new electron gun geometry capable of robust functioning in the presence of a high strength external magnetic field for axisymmetric magnetic resonance imaging (MRI)-linac configurations. This allows an inline MRI-linac to operate without the need to isolate the linear accelerator (linac) using a magnetic shield. This MRI-linac integration approach not only leaves the magnet homogeneity unchanged but also provides the linac flexibility to move along the magnet axis of symmetry if the source to target distance needs to be adjusted. Simple electron gun geometry modifications of a Varian 600 C electron gun are considered and solved in the presence of an external magnetic field in order to determine a set of design principles for the new geometry. Based on these results, a new gun geometry is proposed and optimized in the fringe field of a 0.5 T open bore MRI magnet (GE Signa SP). A computer model for the 6 MeV Varian 600 C linac is used to determine the capture efficiency of the new electron gun-linac system in the presence of the fringe field of the same MRI scanner. The behavior of the new electron gun plus the linac system is also studied in the fringe fields of two other magnets, a 1.0 T prototype open bore magnet and a 1.5 T GE Conquest scanner. Simple geometrical modifications of the original electron gun geometry do not provide feasible solutions. However, these tests show that a smaller transverse cathode diameter with a flat surface and a slightly larger anode diameter could alleviate the current loss due to beam interactions with the anode in the presence of magnetic fields. Based on these findings, an initial geometry resembling a parallel plate capacitor with a hole in the anode is proposed. The optimization procedure finds a cathode-anode distance of 5 mm, a focusing electrode angle of 5°, and an anode drift tube length of 17.1 mm. Also, the linac can be displaced with ± 15 cm along the axis of the 0.5 T magnet without capture efficiency reduction below the experimental value in zero field. In this range of linac displacements, the electron beam generated by the new gun geometry is more effectively injected into the linac in the presence of an external magnetic field, resulting in approximately 20% increase of the target current compared to the original gun geometry behavior at zero field. The new gun geometry can generate and accelerate electron beams in external magnetic fields without current loss for fields higher than 0.11 T. The new electron-gun geometry is robust enough to function in the fringe fields of the other two magnets with a target current loss of no more than 16% with respect to the current obtained with no external magnetic fields. In this work, a specially designed electron gun was presented which can operate in the presence of axisymmetric strong magnetic fringe fields of MRI magnets. Computer simulations show that the electron gun can produce high quality beams which can be injected into a straight through linac such as Varian 600 C and accelerated with more efficiency in the presence of the external magnetic fields. Also, the new configuration allows linac displacements along the magnet axis in a range equal to the diameter of the imaging spherical volume of the magnet under consideration. The new electron gun-linac system can function in the fringe field of a MRI magnet if the field strength at the cathode position is higher than 0.11 T. The capture efficiency of the linac depends on the magnetic field strength and the field gradient. The higher the gradient the better the capture efficiency. The capture efficiency does not degrade more than 16%.
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A novel electron gun for inline MRI-linac configurations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Constantin, Dragoş E., E-mail: dragos.constantin@varian.com; Fahrig, Rebecca; Holloway, Lois
2014-02-15
Purpose: This work introduces a new electron gun geometry capable of robust functioning in the presence of a high strength external magnetic field for axisymmetric magnetic resonance imaging (MRI)-linac configurations. This allows an inline MRI-linac to operate without the need to isolate the linear accelerator (linac) using a magnetic shield. This MRI-linac integration approach not only leaves the magnet homogeneity unchanged but also provides the linac flexibility to move along the magnet axis of symmetry if the source to target distance needs to be adjusted. Methods: Simple electron gun geometry modifications of a Varian 600C electron gun are considered andmore » solved in the presence of an external magnetic field in order to determine a set of design principles for the new geometry. Based on these results, a new gun geometry is proposed and optimized in the fringe field of a 0.5 T open bore MRI magnet (GE Signa SP). A computer model for the 6 MeV Varian 600C linac is used to determine the capture efficiency of the new electron gun-linac system in the presence of the fringe field of the same MRI scanner. The behavior of the new electron gun plus the linac system is also studied in the fringe fields of two other magnets, a 1.0 T prototype open bore magnet and a 1.5 T GE Conquest scanner. Results: Simple geometrical modifications of the original electron gun geometry do not provide feasible solutions. However, these tests show that a smaller transverse cathode diameter with a flat surface and a slightly larger anode diameter could alleviate the current loss due to beam interactions with the anode in the presence of magnetic fields. Based on these findings, an initial geometry resembling a parallel plate capacitor with a hole in the anode is proposed. The optimization procedure finds a cathode-anode distance of 5 mm, a focusing electrode angle of 5°, and an anode drift tube length of 17.1 mm. Also, the linac can be displaced with ±15 cm along the axis of the 0.5 T magnet without capture efficiency reduction below the experimental value in zero field. In this range of linac displacements, the electron beam generated by the new gun geometry is more effectively injected into the linac in the presence of an external magnetic field, resulting in approximately 20% increase of the target current compared to the original gun geometry behavior at zero field. The new gun geometry can generate and accelerate electron beams in external magnetic fields without current loss for fields higher than 0.11 T. The new electron-gun geometry is robust enough to function in the fringe fields of the other two magnets with a target current loss of no more than 16% with respect to the current obtained with no external magnetic fields. Conclusions: In this work, a specially designed electron gun was presented which can operate in the presence of axisymmetric strong magnetic fringe fields of MRI magnets. Computer simulations show that the electron gun can produce high quality beams which can be injected into a straight through linac such as Varian 600C and accelerated with more efficiency in the presence of the external magnetic fields. Also, the new configuration allows linac displacements along the magnet axis in a range equal to the diameter of the imaging spherical volume of the magnet under consideration. The new electron gun-linac system can function in the fringe field of a MRI magnet if the field strength at the cathode position is higher than 0.11 T. The capture efficiency of the linac depends on the magnetic field strength and the field gradient. The higher the gradient the better the capture efficiency. The capture efficiency does not degrade more than 16%.« less
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A novel electron gun for inline MRI-linac configurations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Constantin, Dragoş E., E-mail: dragos.constantin@varian.com; Fahrig, Rebecca; Holloway, Lois
Purpose: This work introduces a new electron gun geometry capable of robust functioning in the presence of a high strength external magnetic field for axisymmetric magnetic resonance imaging (MRI)-linac configurations. This allows an inline MRI-linac to operate without the need to isolate the linear accelerator (linac) using a magnetic shield. This MRI-linac integration approach not only leaves the magnet homogeneity unchanged but also provides the linac flexibility to move along the magnet axis of symmetry if the source to target distance needs to be adjusted. Methods: Simple electron gun geometry modifications of a Varian 600C electron gun are considered andmore » solved in the presence of an external magnetic field in order to determine a set of design principles for the new geometry. Based on these results, a new gun geometry is proposed and optimized in the fringe field of a 0.5 T open bore MRI magnet (GE Signa SP). A computer model for the 6 MeV Varian 600C linac is used to determine the capture efficiency of the new electron gun-linac system in the presence of the fringe field of the same MRI scanner. The behavior of the new electron gun plus the linac system is also studied in the fringe fields of two other magnets, a 1.0 T prototype open bore magnet and a 1.5 T GE Conquest scanner. Results: Simple geometrical modifications of the original electron gun geometry do not provide feasible solutions. However, these tests show that a smaller transverse cathode diameter with a flat surface and a slightly larger anode diameter could alleviate the current loss due to beam interactions with the anode in the presence of magnetic fields. Based on these findings, an initial geometry resembling a parallel plate capacitor with a hole in the anode is proposed. The optimization procedure finds a cathode-anode distance of 5 mm, a focusing electrode angle of 5°, and an anode drift tube length of 17.1 mm. Also, the linac can be displaced with ±15 cm along the axis of the 0.5 T magnet without capture efficiency reduction below the experimental value in zero field. In this range of linac displacements, the electron beam generated by the new gun geometry is more effectively injected into the linac in the presence of an external magnetic field, resulting in approximately 20% increase of the target current compared to the original gun geometry behavior at zero field. The new gun geometry can generate and accelerate electron beams in external magnetic fields without current loss for fields higher than 0.11 T. The new electron-gun geometry is robust enough to function in the fringe fields of the other two magnets with a target current loss of no more than 16% with respect to the current obtained with no external magnetic fields. Conclusions: In this work, a specially designed electron gun was presented which can operate in the presence of axisymmetric strong magnetic fringe fields of MRI magnets. Computer simulations show that the electron gun can produce high quality beams which can be injected into a straight through linac such as Varian 600C and accelerated with more efficiency in the presence of the external magnetic fields. Also, the new configuration allows linac displacements along the magnet axis in a range equal to the diameter of the imaging spherical volume of the magnet under consideration. The new electron gun-linac system can function in the fringe field of a MRI magnet if the field strength at the cathode position is higher than 0.11 T. The capture efficiency of the linac depends on the magnetic field strength and the field gradient. The higher the gradient the better the capture efficiency. The capture efficiency does not degrade more than 16%.« less
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Toward a web-based real-time radiation treatment planning system in a cloud computing environment.
Na, Yong Hum; Suh, Tae-Suk; Kapp, Daniel S; Xing, Lei
2013-09-21
To exploit the potential dosimetric advantages of intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), an in-depth approach is required to provide efficient computing methods. This needs to incorporate clinically related organ specific constraints, Monte Carlo (MC) dose calculations, and large-scale plan optimization. This paper describes our first steps toward a web-based real-time radiation treatment planning system in a cloud computing environment (CCE). The Amazon Elastic Compute Cloud (EC2) with a master node (named m2.xlarge containing 17.1 GB of memory, two virtual cores with 3.25 EC2 Compute Units each, 420 GB of instance storage, 64-bit platform) is used as the backbone of cloud computing for dose calculation and plan optimization. The master node is able to scale the workers on an 'on-demand' basis. MC dose calculation is employed to generate accurate beamlet dose kernels by parallel tasks. The intensity modulation optimization uses total-variation regularization (TVR) and generates piecewise constant fluence maps for each initial beam direction in a distributed manner over the CCE. The optimized fluence maps are segmented into deliverable apertures. The shape of each aperture is iteratively rectified to be a sequence of arcs using the manufacture's constraints. The output plan file from the EC2 is sent to the simple storage service. Three de-identified clinical cancer treatment plans have been studied for evaluating the performance of the new planning platform with 6 MV flattening filter free beams (40 × 40 cm(2)) from the Varian TrueBeam(TM) STx linear accelerator. A CCE leads to speed-ups of up to 14-fold for both dose kernel calculations and plan optimizations in the head and neck, lung, and prostate cancer cases considered in this study. The proposed system relies on a CCE that is able to provide an infrastructure for parallel and distributed computing. The resultant plans from the cloud computing are identical to PC-based IMRT and VMAT plans, confirming the reliability of the cloud computing platform. This cloud computing infrastructure has been established for a radiation treatment planning. It substantially improves the speed of inverse planning and makes future on-treatment adaptive re-planning possible.
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Toward a web-based real-time radiation treatment planning system in a cloud computing environment
NASA Astrophysics Data System (ADS)
Hum Na, Yong; Suh, Tae-Suk; Kapp, Daniel S.; Xing, Lei
2013-09-01
To exploit the potential dosimetric advantages of intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), an in-depth approach is required to provide efficient computing methods. This needs to incorporate clinically related organ specific constraints, Monte Carlo (MC) dose calculations, and large-scale plan optimization. This paper describes our first steps toward a web-based real-time radiation treatment planning system in a cloud computing environment (CCE). The Amazon Elastic Compute Cloud (EC2) with a master node (named m2.xlarge containing 17.1 GB of memory, two virtual cores with 3.25 EC2 Compute Units each, 420 GB of instance storage, 64-bit platform) is used as the backbone of cloud computing for dose calculation and plan optimization. The master node is able to scale the workers on an ‘on-demand’ basis. MC dose calculation is employed to generate accurate beamlet dose kernels by parallel tasks. The intensity modulation optimization uses total-variation regularization (TVR) and generates piecewise constant fluence maps for each initial beam direction in a distributed manner over the CCE. The optimized fluence maps are segmented into deliverable apertures. The shape of each aperture is iteratively rectified to be a sequence of arcs using the manufacture’s constraints. The output plan file from the EC2 is sent to the simple storage service. Three de-identified clinical cancer treatment plans have been studied for evaluating the performance of the new planning platform with 6 MV flattening filter free beams (40 × 40 cm2) from the Varian TrueBeamTM STx linear accelerator. A CCE leads to speed-ups of up to 14-fold for both dose kernel calculations and plan optimizations in the head and neck, lung, and prostate cancer cases considered in this study. The proposed system relies on a CCE that is able to provide an infrastructure for parallel and distributed computing. The resultant plans from the cloud computing are identical to PC-based IMRT and VMAT plans, confirming the reliability of the cloud computing platform. This cloud computing infrastructure has been established for a radiation treatment planning. It substantially improves the speed of inverse planning and makes future on-treatment adaptive re-planning possible.
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An Inversion Recovery NMR Kinetics Experiment
ERIC Educational Resources Information Center
Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping
2011-01-01
A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this…
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Ambient air spiked with 1-10 ppbv concentrations of 41 toxic volatile organic compounds (VOCs) listed in U.S. Environmental Protection Agency (EPA) Compendium Method TO-14A was monitored using solid sorbents for sample collection and a Varian Saturn 2000 ion trap mass spectrome...
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Shintani, Naoya; Monzen, Hajime; Tamura, Masaya; Asai, Yoshiyuki; Shimomura, Kouhei; Matsumoto, Kenji; Okumura, Masahiko; Nishimura, Yasumasa
2016-01-01
The purpose of this study is to evaluate the mechanical accuracy of a respiratory-gated radiation system that combines the Linear Indicator-equipped Abches respiration-monitoring device and the Varian Real-time Position Management system (LI-RPM system). This combined configuration, implemented for the first time in Japan, was compared with the stand-alone Varian RPM system (RPM system). The delay times, dose profiles, and output waveforms of the LI-RPM and RPM systems were evaluated using a self-produced dynamic phantom. The delay times for the LI-RPM and RPM systems were both 0.1 s for 4 s and 8 s test periods. The corresponding output waveform correlation factors (R 2 ) for the 4 s and 8 s test periods were 0.9981 and 0.9975, respectively. No difference was observed in the dose profiles of the two systems. Thus, the present results indicate that the proposed LI-RPM combined respiratory-gated radiation system has similar properties to the RPM system. However, it offers several advantages in terms of its versatility, including its alignment assistance capabilities for non-coplanar treatments.
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Kocuria Species Peritonitis: Although Rare, We Have To Care
Dotis, John; Printza, Nikoleta; Stabouli, Stella; Papachristou, Fotios
2015-01-01
Kocuria species are found in the environment and on human skin. These micro-organisms are generally considered to be nonpathogenic saprophytes, rarely causing infection. However, the peritoneum has been reported to be a site of Kocuria infection. We reviewed all cases of peritonitis in peritoneal dialysis (PD) patients caused by Kocuria species that were reported in the worldwide literature. In total, 12 episodes of Kocuria species peritonitis have been reported in 9 PD patients. The median age of the patients was 62 years (range: 8 – 78 years). In the reported episodes, 4 different Kocuria species were isolated, with K. varians being the predominant species (41.7%). The most common initial symptom was abdominal pain (83.3%), followed by turbid effluent (75%) and fever (33.3%). Intraperitoneal first-generation cephalosporins and glycopeptides were the most-used antibiotics, with first-generation cephalosporins being more often preferred as first-line therapy. The median duration of treatment was 14 days, and in 2 episodes, the Tenckhoff catheter was removed. Although Kocuria peritonitis in PD patients is rare, it should be promptly treated because relapses can occur, especially with K. varians episodes. PMID:24584591
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Consistency and reproducibility of the VMAT plan delivery using three independent validation methods
Chandraraj, Varatharaj; Manickam, Ravikumar; Esquivel, Carlos; Supe, Sanjay S; Papanikolaou, Nikos
2010-01-01
The complexity of VMAT delivery requires new methods and potentially new tools for the commissioning of these systems. It appears that great consideration is needed for quality assurance (QA) of these treatments since there are limited devices that are dedicated to the QA of rotational delivery. In this present study, we have evaluated the consistency and reproducibility of one prostate and one lung VMAT plans for 31 consecutive days using three different approaches: 1) MLC DynaLog files, 2) in vivo measurements using the multiwire ionization chamber DAVID, and 3) using PTWseven29 2D ARRAY with the OCTAVIUS phantom at our Varian Clinac linear accelerator. Overall, the three methods of testing the reproducibility and consistency of the VMAT delivery were in agreement with each other. All methods showed minimal daily deviations that contributed to clinically insignificant dose variations from day to day. Based on our results, we conclude that the VMAT delivery using a Varian 2100CD linear accelerator equipped with 120 MLC is highly reproducible. PACS numbers: 87.55.Qr and 87.56.Fc
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Saleh, Z; Tang, X; Song, Y
Purpose: To investigate the long term stability and viability of using EPID-based daily output QA via in-house and vendor driven protocol, to replace conventional QA tools and improve QA efficiency. Methods: Two Varian TrueBeam machines (TB1&TB2) equipped with electronic portal imaging devices (EPID) were employed in this study. Both machines were calibrated per TG-51 and used clinically since Oct 2014. Daily output measurement for 6/15 MV beams were obtained using SunNuclear DailyQA3 device as part of morning QA. In addition, in-house protocol was implemented for EPID output measurement (10×10 cm fields, 100 MU, 100cm SID, output defined over an ROImore » of 2×2 cm around central axis). Moreover, the Varian Machine Performance Check (MPC) was used on both machines to measure machine output. The EPID and DailyQA3 based measurements of the relative machine output were compared and cross-correlated with monthly machine output as measured by an A12 Exradin 0.65cc Ion Chamber (IC) serving as ground truth. The results were correlated using Pearson test. Results: The correlations among DailyQA3, in-house EPID and Varian MPC output measurements, with the IC for 6/15 MV were similar for TB1 (0.83–0.95) and TB2 (0.55–0.67). The machine output for the 6/15MV beams on both machines showed a similar trend, namely an increase over time as indicated by all measurements, requiring a machine recalibration after 6 months. This drift is due to a known issue with pressurized monitor chamber which tends to leak over time. MPC failed occasionally but passed when repeated. Conclusion: The results indicate that the use of EPID for daily output measurements has the potential to become a viable and efficient tool for daily routine LINAC QA, thus eliminating weather (T,P) and human setup variability and increasing efficiency of the QA process.« less
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A comparison of phantom scatter from flattened and flattening filter free high-energy photon beams.
Richmond, Neil; Allen, Vince; Daniel, Jim; Dacey, Rob; Walker, Chris
2015-01-01
Flattening filter free (FFF) photon beams have different dosimetric properties from those of flattened beams. The aim of this work was to characterize the collimator scatter (Sc) and total scatter (Scp) from 3 FFF beams of differing quality indices and use the resulting mathematical fits to generate phantom scatter (Sp) data. The similarities and differences between Sp of flattened and FFF beams are described. Sc and Scp data were measured for 3 flattened and 3 FFF high-energy photon beams (Varian 6 and 10MV and Elekta 6MV). These data were fitted to logarithmic power law functions with 4 numerical coefficients. The agreement between our experimentally determined flattened beam Sp and published data was within ± 1.2% for all 3 beams investigated and all field sizes from 4 × 4 to 40 × 40cm(2). For the FFF beams, Sp was only within 1% of the same flattened beam published data for field sizes between 6 × 6 and 14 × 14cm(2). Outside this range, the differences were much greater, reaching - 3.2%, - 4.5%, and - 4.3% for the fields of 40 × 40cm(2) for the Varian 6-MV, Varian 10-MV, and Elekta 6-MV FFF beams, respectively. The FFF beam Sp increased more slowly with increasing field size than that of the published and measured flattened beam of a similar reference field size quality index, i.e., there is less Phantom Scatter than that found with flattened beams for a given field size. This difference can be explained when the fluence profiles of the flattened and FFF beams are considered. The FFF beam has greatly reduced fluence off axis, especially as field size increases, compared with the flattened beam profile; hence, less scatter is generated in the phantom reaching the central axis. Copyright © 2015 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.
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SU-E-T-543: Measurement of Neutron Activation From Different High Energy Varian Linear Accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Thatcher, T; Madsen, S; Sudowe, R
2015-06-15
Purpose: Linear accelerators producing photons above 10 MeV may induce photonuclear reactions in high Z components of the accelerator. These liberated neutrons can then activate the structural components of the accelerator and other materials in the beam path through neutron capture reactions. The induced activity within the accelerator may contribute to additional dose to both patients and personnel. This project seeks to determine the total activity and activity per activated isotope following irradiation in different Varian accelerators at energies above 10 MeV. Methods: A Varian 21IX accelerator was used to irradiate a 30 cm × 30 cm × 20 cmmore » solid water phantom with 15 MV x-rays. The phantom was placed at an SSD of 100 cm and at the center of a 20 cm × 20 cm field. Activation induced gamma spectra were acquired over a 5 minute interval after 1 and 15 minutes from completion of the irradiation. All measurements were made using a CANBERRA Falcon 5000 Portable HPGe detector. The majority of measurements were made in scattering geometry with the detector situated at 90° to the incident beam, 30 cm from the side of the phantom and approximately 10 cm from the top. A 5 minute background count was acquired and automatically subtracted from all subsequent measurements. Photon spectra were acquired for both open and MLC fields. Results: Based on spectral signatures, nuclides have been identified and their activities calculated for both open and MLC fields. Preliminary analyses suggest that activities from the activation products in the microcurie range. Conclusion: Activation isotopes have been identified and their relative activities determined. These activities are only gross estimates since efficiencies have not been determined for this source-detector geometry. Current efforts are focused on accurate determination of detector efficiencies using Monte Carlo calculations.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Kumar, Syam; Anjana
Purpose: To evaluate the fluence for the midline and lateralized tumors for VMAT technique using 2D seven29 detector array combined with the Octavius phantom. Methods: 60 cases that are already being treated with volumetric modulated arc therapy (VMAT) have selected for this study. This includes tumors situated at the medial and lateral. Medial refers to the tumor situated at the midline of the body and lateral means toward the side or away from the midline of the body. Verification plans were created for each treatment plan in Varian Eclipse treatment planning system (version10, Varian medical systems, Palo Alto,CA) with themore » 2D Seven29 detector array and the Octavius phantom(PTW, Freiburg, Germany). Measurements were performed on a Varian Clinac 2100 iX, linear accelerator equipped with a millennium 120 leaf collimator. Analysis was done by comparing the fluence measured for the tumors situated on the midline and tumors situated laterally. Results: Fluence measured for all the delivered plans were analyzed using Verisoft software (PTW, Freiburg, Germany). The gamma pass percentage for midline tumors were found to be higher compared with the lateralized ones. The standard deviation between gamma values for midline and lateralized tumors is 2.18 and 3.5 respectively. Also the standard deviation between the point doses for midline and lateralized tumors is 0.38 and 0.29 respectively. The average gamma passing rate for midline tumors is 96.55% and for lateralized tumors are 94.94% for 3%DD and 3mm DTA criteria. From the T test, it was found that there is no significant difference between the gamma pass percentage between midline and lateralized tumors with p value of 0.28. Conclusion: There is no particular correlation found in the gamma pass criteria for midline and lateralized tumors.« less
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TU-FG-201-05: Varian MPC as a Statistical Process Control Tool
DOE Office of Scientific and Technical Information (OSTI.GOV)
Carver, A; Rowbottom, C
Purpose: Quality assurance in radiotherapy requires the measurement of various machine parameters to ensure they remain within permitted values over time. In Truebeam release 2.0 the Machine Performance Check (MPC) was released allowing beam output and machine axis movements to be assessed in a single test. We aim to evaluate the Varian Machine Performance Check (MPC) as a tool for Statistical Process Control (SPC). Methods: Varian’s MPC tool was used on three Truebeam and one EDGE linac for a period of approximately one year. MPC was commissioned against independent systems. After this period the data were reviewed to determine whethermore » or not the MPC was useful as a process control tool. Analyses on individual tests were analysed using Shewhart control plots, using Matlab for analysis. Principal component analysis was used to determine if a multivariate model was of any benefit in analysing the data. Results: Control charts were found to be useful to detect beam output changes, worn T-nuts and jaw calibration issues. Upper and lower control limits were defined at the 95% level. Multivariate SPC was performed using Principal Component Analysis. We found little evidence of clustering beyond that which might be naively expected such as beam uniformity and beam output. Whilst this makes multivariate analysis of little use it suggests that each test is giving independent information. Conclusion: The variety of independent parameters tested in MPC makes it a sensitive tool for routine machine QA. We have determined that using control charts in our QA programme would rapidly detect changes in machine performance. The use of control charts allows large quantities of tests to be performed on all linacs without visual inspection of all results. The use of control limits alerts users when data are inconsistent with previous measurements before they become out of specification. A. Carver has received a speaker’s honorarium from Varian.« less
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SU-F-T-66: Characteristics of Electron Beams From Varian Trubeam
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dimofte, A; Kennedy, C; Zhu, T
2016-06-15
Purpose: The purpose of this study was to compare the electron beam data between Truebeam and 2300ix Varian accelerators for percent depth dose for broad beam and small circular cutouts, cone factors, head scatter factor as a function of cone size and SSD, phantom scatter factor, blocking factor, distance factor and virtual source position. Methods: Measurements were performed for Truebeam and 2300ix Varian accelerators. The main energies used were: 6, 9, 12, 16 and 20 MeV. PDD was measured at SSD = 100 cm for open beam and small circular cutouts (r = 0.5, 1.0, 1.5, 2.0, 3.0, 4.0 andmore » 6.6cm) for different energies. Measurements to determine the head scatter factor (H) were done as a function of radius for six representative energies and five cone sizes (6, 10, 15, 20 and 25cm2). The phantom scatter factor (PSF) is defined as the ratio of blocking factor in water at reference depth and head scatter factor in air. PSF was measured as a function of radius and electron energy. Distance factor was measured for all energies and cones for three SSD’s (100, 110 and 120cm). Results: The percent depth dose (PDD) was measured for small cutouts of radius r = 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0 and 5.6cm. Blocking factor (BF) was measured for Truebeam and 2300ix accelerators, for different circular cutouts and energies for a 10×10 cone. Cone factors were compared between the two accelerators for different energies and applicator sizes. Conclusion: Cone factors measured for the two accelerator types differ by up to 5% for the largest applicator size. Blocking factors differs by up to 3%, with the largest variation for the smallest field size (0.5cm). Distance factor for different SSD’s differ by up to 4.5%.« less
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SU-E-T-315: Dosimetric Effects of Couch Top Shift On VMAT Delivery in Absence of Indexing
DOE Office of Scientific and Technical Information (OSTI.GOV)
Islam, M; Jin, H; Ferguson, S
2015-06-15
Purpose: To investigate dosimetric effects of couch top shift for volumetric-modulated arc therapy (VMAT) in absence of indexing of immobilization devices. Methods: A total of twelve VMAT treatment plans were selected from three regions (lung, abdomen, and pelvis) to account for the variation of the patient position relative to the couch top. The treatment plans were generated using the Varian Eclipse system. A pinpoint ionization chamber (PTW TN31014) was placed at the center of 16-cm solid water phantom and the dose was delivered using the Varian TrueBeam STx with BrainLAB ExacTrac couch top. To simulate the day-to-day variation of themore » patient position relative to couch top, the couch top was laterally shifted up to 50 mm, with an increment of 5 mm from 0 to 20 mm; and of 10 mm afterwards, and the phantom was moved back to 0 cm shift for measurement. The dose was also delivered using a Varian tennis racket grid insert at 0 cm shift to simulate the absence of couch top. The treatment plans were delivered with 6, 10, and 15 MV photons using the same leaf sequencing to investigate the energy dependence of couch top shift. The dose difference was normalized to 0 cm shift for the regular couch top for comparison. Results: The percent difference of dose was found to increase with lateral shift for all energies; however, the average differences were close to 0% and the maximum difference was within 1% along the lateral shifts. The differences with the absence of couch top were 2.2±0.5% (6MV), 1.7±0.3% (10MV), and 1.6±0.2% (15MV), respectively. Conclusion: The inclusion of couch top is recommended in treatment planning to minimize the dosimetric uncertainty between calculated and delivered dose even in absence of indexing of immobilization devices in VMAT delivery.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Dewyngaert, K; Jozsef, G; Formenti, S
Purpose: To report on the clinical validation of the Varian Pivotal™ Treatment Solution for Prone Breast Care: a platform for prone breast radiation therapy. Methods: Patients treated using Breast Conserving Radiation Therapy may benefit from treatment in the prone position with the breast tissue falling freely away from the body. This geometry allows the breast tissue to be treated while avoiding the lung and heart tissue. Eighteen patients simulated and treated using the Varian Medical Systems Pivotal™ Treatment Solution for Prone Breast Care were monitored over the course of treatment for positioning integrity and reproducibility. As this carbon-fiber platform actuallymore » replaces a portion of the couch top, indexing is inherent to its design. Patients were positioned on the couch and aligned using fiducial markers and lateral SSD to the breast fiducial point. The daily couch coordinates then serves as indicators for positioning variability with this system. Results: The variations in couch vertical, longitudinal and lateral positions were centered on a mean value of zero with standard deviations of 0.44cm, 0.75cm and 0.79cm respectively. Other factors explored were variations in distance of mid-sternum to table edge and patient rotation into the opening. The median rotation of the chest wall was found to be 11.5 degrees at CT-Simulation with a median distance of 2.5cm from midsternum to support opening. Patient rotation was not associated with either breast size or distance from edge of platform. Conclusion: The Pivotal™ Treatment solution consists of a couch top that replaces the standard top and as such is open from beneath without obstruction. This is a distinction from all other solutions which rely on a platform positioned above and indexed to the treatment couch. We found the reproducibility to be consistent with our historical measures while offering benefits of an integrated solution as stated above. supported by Professional Services Agreeement with Varian Medical Systems.« less
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SU-E-T-50: Automatic Validation of Megavoltage Beams Modeled for Clinical Use in Radiation Therapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Melchior, M; Salinas Aranda, F; 21st Century Oncology, Ft. Myers, FL
2014-06-01
Purpose: To automatically validate megavoltage beams modeled in XiO™ 4.50 (Elekta, Stockholm, Sweden) and Varian Eclipse™ Treatment Planning Systems (TPS) (Varian Associates, Palo Alto, CA, USA), reducing validation time before beam-on for clinical use. Methods: A software application that can automatically read and analyze DICOM RT Dose and W2CAD files was developed using MatLab integrated development environment.TPS calculated dose distributions, in DICOM RT Dose format, and dose values measured in different Varian Clinac beams, in W2CAD format, were compared. Experimental beam data used were those acquired for beam commissioning, collected on a water phantom with a 2D automatic beam scanningmore » system.Two methods were chosen to evaluate dose distributions fitting: gamma analysis and point tests described in Appendix E of IAEA TECDOC-1583. Depth dose curves and beam profiles were evaluated for both open and wedged beams. Tolerance parameters chosen for gamma analysis are 3% and 3 mm dose and distance, respectively.Absolute dose was measured independently at points proposed in Appendix E of TECDOC-1583 to validate software results. Results: TPS calculated depth dose distributions agree with measured beam data under fixed precision values at all depths analyzed. Measured beam dose profiles match TPS calculated doses with high accuracy in both open and wedged beams. Depth and profile dose distributions fitting analysis show gamma values < 1. Relative errors at points proposed in Appendix E of TECDOC-1583 meet therein recommended tolerances.Independent absolute dose measurements at points proposed in Appendix E of TECDOC-1583 confirm software results. Conclusion: Automatic validation of megavoltage beams modeled for their use in the clinic was accomplished. The software tool developed proved efficient, giving users a convenient and reliable environment to decide whether to accept or not a beam model for clinical use. Validation time before beam-on for clinical use was reduced to a few hours.« less
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Silva, Diego B; Bueno, Vanda H P; Van Loon, Joop J A; Peñaflor, Maria Fernanda G V; Bento, José Maurício S; Van Lenteren, Joop C
2018-01-01
Plants emit volatile compounds in response to insect herbivory, which may play multiple roles as defensive compounds and mediators of interactions with other plants, microorganisms and animals. Herbivore-induced plant volatiles (HIPVs) may act as indirect plant defenses by attracting natural enemies of the attacking herbivore. We report here the first evidence of the attraction of three Neotropical mirid predators (Macrolophus basicornis, Engytatus varians and Campyloneuropsis infumatus) toward plants emitting volatiles induced upon feeding by two tomato pests, the leaf miner Tuta absoluta and the phloem feeder Bemisia tabaci, in olfactometer bioassays. Subsequently, we compared the composition of volatile blends emitted by insect-infested tomato plants by collecting headspace samples and analyzing them with GC-FID and GC-MS. Egg deposition by T. absoluta did not make tomato plants more attractive to the mirid predators than uninfested tomato plants. Macrolophus basicornis is attracted to tomato plants infested with either T. absoluta larvae or by a mixture of B. tabaci eggs, nymphs and adults. Engytatus varians and C. infumatus responded to volatile blends released by tomato plants infested with T. absoluta larvae over uninfested plants. Also, multiple herbivory by T. absoluta and B. tabaci did not increase the attraction of the mirids compared to infestation with T. absoluta alone. Terpenoids represented the most important class of compounds in the volatile blends and there were significant differences between the volatile blends emitted by tomato plants in response to attack by T. absoluta, B. tabaci, or by both insects. We, therefore, conclude that all three mirids use tomato plant volatiles to find T. absoluta larvae. Multiple herbivory did neither increase, nor decrease attraction of C. infumatus, E. varians and M. basicornis. By breeding for higher rates of emission of selected terpenes, increased attractiveness of tomato plants to natural enemies may improve the effectiveness of biological control.
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SU-E-T-91: Correction Method to Determine Surface Dose for OSL Detectors
DOE Office of Scientific and Technical Information (OSTI.GOV)
Reynolds, T; Higgins, P
Purpose: OSL detectors are commonly used in clinic due to their numerous advantages, such as linear response, negligible energy, angle and temperature dependence in clinical range, for verification of the doses beyond the dmax. Although, due to the bulky shielding envelope, this type of detectors fails to measure skin dose, which is an important assessment of patient ability to finish the treatment on time and possibility of acute side effects. This study aims to optimize the methodology of determination of skin dose for conventional accelerators and a flattening filter free Tomotherapy. Methods: Measurements were done for x-ray beams: 6 MVmore » (Varian Clinac 2300, 10×10 cm{sup 2} open field, SSD = 100 cm) and for 5.5 MV (Tomotherapy, 15×40 cm{sup 2} field, SAD = 85 cm). The detectors were placed at the surface of the solid water phantom and at the reference depth (dref=1.7cm (Varian 2300), dref =1.0 cm (Tomotherapy)). The measurements for OSLs were related to the externally exposed OSLs measurements, and further were corrected to surface dose using an extrapolation method indexed to the baseline Attix ion chamber measurements. A consistent use of the extrapolation method involved: 1) irradiation of three OSLs stacked on top of each other on the surface of the phantom; 2) measurement of the relative dose value for each layer; and, 3) extrapolation of these values to zero thickness. Results: OSL measurements showed an overestimation of surface doses by the factor 2.31 for Varian 2300 and 2.65 for Tomotherapy. The relationships: SD{sup 2300} = 0.68 × M{sup 2300}-12.7 and SDτoμo = 0.73 × Mτoμo-13.1 were found to correct the single OSL measurements to surface doses in agreement with Attix measurements to within 0.1% for both machines. Conclusion: This work provides simple empirical relationships for surface dose measurements using single OSL detectors.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhou, S; Fan, Q; Lei, Y
Purpose: In-Water-Output-Ratio (IWOR) plays a significant role in linac-based radiotherapy treatment planning, linking MUs to delivered radiation dose. For an open rectangular field, IWOR depends on both its width and length, and changes rapidly when one of them becomes small. In this study, a universal functional form is proposed to fit the open field IWOR tables in Varian TrueBeam representative datasets for all photon energies. Methods: A novel Generalized Mean formula is first used to estimate the Equivalent Square (ES) for a rectangular field. The formula’s weighting factor and power index are determined by collapsing all data points as muchmore » as possible onto a single curve in IWOR vs. ES plot. The result is then fitted with a novel universal function IWOR=1+b*Log(ES/10cm)/(ES/10cm)^c via a least-square procedure to determine the optimal values for parameters b and c. The maximum relative residual error in IWOR over the entire two-dimensional measurement table with field sizes between 3cm and 40cm is used to evaluate the quality of fit for the function. Results: The two-step fitting strategy works very well in determining the optimal parameter values for open field IWOR of each photon energies in the Varian data-set. Relative residual error ≤0.71% is achieved for all photon energies (including Flattening-Filter-Free modes) with field sizes between 3cm and 40cm. The optimal parameter values change smoothly with regular photon beam quality. Conclusion: The universal functional form fits the Varian TrueBeam open field IWOR measurement tables accurately with small relative residual errors for all photon energies. Therefore, it can be an excellent choice to represent IWOR in absolute dose and MU calculations. The functional form can also be used as a QA/commissioning tool to verify the measured data quality and consistency by checking the IWOR data behavior against the function for new photon energies with arbitrary beam quality.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Kim, S; Rangaraj, D
2016-06-15
Purpose: Although cone-beam CT (CBCT) imaging became popular in radiation oncology, its imaging dose estimation is still challenging. The goal of this study is to assess the kilovoltage CBCT doses using GMctdospp - an EGSnrc based Monte Carlo (MC) framework. Methods: Two Varian OBI x-ray tube models were implemented in the GMctpdospp framework of EGSnrc MC System. The x-ray spectrum of 125 kVp CBCT beam was acquired from an EGSnrc/BEAMnrc simulation and validated with IPEM report 78. Then, the spectrum was utilized as an input spectrum in GMctdospp dose calculations. Both full and half bowtie pre-filters of the OBI systemmore » were created by using egs-prism module. The x-ray tube MC models were verified by comparing calculated dosimetric profiles (lateral and depth) to ion chamber measurements for a static x-ray beam irradiation to a cuboid water phantom. An abdominal CBCT imaging doses was simulated in GMctdospp framework using a 5-year-old anthropomorphic phantom. The organ doses and effective dose (ED) from the framework were assessed and compared to the MOSFET measurements and convolution/superposition dose calculations. Results: The lateral and depth dose profiles in the water cuboid phantom were well matched within 6% except a few areas - left shoulder of the half bowtie lateral profile and surface of water phantom. The organ doses and ED from the MC framework were found to be closer to MOSFET measurements and CS calculations within 2 cGy and 5 mSv respectively. Conclusion: This study implemented and validated the Varian OBI x-ray tube models in the GMctdospp MC framework using a cuboid water phantom and CBCT imaging doses were also evaluated in a 5-year-old anthropomorphic phantom. In future study, various CBCT imaging protocols will be implemented and validated and consequently patient CT images will be used to estimate the CBCT imaging doses in patients.« less
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Rainbow, P.S.; Poirier, L.; Smith, B.D.; Brix, K.V.; Luoma, S.N.
2006-01-01
The chemical form of accumulated trace metal in prey is important in controlling the bioavailataility of dietary metal to a predator. This study investigated the trophic transfer of radiolabelled Ag, Cd and Zn from the polychaete worm Nereis diversicolor to the decapod crustacean Palaemonetes varians. We used 2 populations of worms with different proportions of accumulated metals in different subcellular fractions as prey, and loaded the worms with radiolabelled metals either from sediment or from solution. Accumulated radiolabelled metals were fractionated into 5 components : metal-rich granules (MRG), cellular debris, organelles, metallothionein-like proteins (MTLP), and other (heat-sensitive) proteins (HSP). Assimilation efficiencies (AE) of the metals by P. varians were measured from the 4 categories of prey (i.e. 2 populations, radiolabelled from sediment or solution). There were significant differences for each metal between the AEs from the different prey categories, confirming that origin of prey and route of uptake of accumulated trace metal will cause intraspecific differences in subsequent metal assimilation. Correlations were sought between AEs and selected fractions or combinations of fractions of metals in the prey-MRG, Trophically Available Metal (TAM = MTLP + HSP + organelles) and total protein (MTLP + HSP). TAM explained 28% of the variance in AEs for Ag, but no consistent relationships emerged between AEs and TAM or total protein when the metals were considered separately. AEs did, however, show significant positive regressions with both TAM and total protein when the 3 metals were considered together, explaining only about 21 % of the variance in each case. A significant negative relationship was observed between MRG and AE for all metals combined. The predator (P. varians) can assimilate dietary metal from a range of the fractions binding metals in the prey (N. diversicolor), with different assimilation efficiencies summated across these fractions. TAM and/or total protein may represent an approximate minimum for trophic availability but neither of these alone is a fully accurate predictor. ?? Inter-Research 2006.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
McCabe, B; Wiersma, R
Purpose: Low temporal latency between a gating on/off signal and a linac beam on/off during respiratory gating is critical for patient safety. Although, a measurement of temporal lag is recommended by AAPM Task Group 142 for commissioning and annual quality assurance, there currently exists no published method. Here we describe a simple, inexpensive, and reliable method to precisely measure gating lag at millisecond resolutions. Methods: A Varian Real-time Position Management™ (RPM) gating simulator with rotating disk was modified with a resistive flex sensor (Spectra Symbol) attached to the gating box platform. A photon diode was placed at machine isocenter. Outputmore » signals of the flex sensor and diode were monitored with a multichannel oscilloscope (Tektronix™ DPO3014). Qualitative inspection of the gating window/beam on synchronicity were made by setting the linac to beam on/off at end-expiration, and the oscilloscope's temporal window to 100 ms to visually examine if the on/off timing was within the recommended 100-ms tolerance. Quantitative measurements were made by saving the signal traces and analyzing in MatLab™. The on and off of the beam signal were located and compared to the expected gating window (e.g. 40% to 60%). Four gating cycles were measured and compared. Results: On a Varian TrueBeam™ STx linac with RPM gating software, the average difference in synchronicity at beam on and off for four cycles was 14 ms (3 to 30 ms) and 11 ms (2 to 32 ms), respectively. For a Varian Clinac™ 21EX the average difference at beam on and off was 127 ms (122 to 133 ms) and 46 ms (42 to 49 ms), respectively. The uncertainty in the synchrony difference was estimated at ±6 ms. Conclusion: This new gating QA method is easy to implement and allows for fast qualitative inspection and quantitative measurements for commissioning and TG-142 annual QA measurements.« less
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Lee, T-F; Ting, H-M; Chao, P-J; Wang, H-Y; Shieh, C-S; Horng, M-F; Wu, J-M; Yeh, S-A; Cho, M-Y; Huang, E-Y; Huang, Y-J; Chen, H-C; Fang, F-M
2012-01-01
Objective We compared and evaluated the differences between two models for treating bilateral breast cancer (BBC): (i) dose–volume-based intensity-modulated radiation treatment (DV plan), and (ii) dose–volume-based intensity-modulated radiotherapy with generalised equivalent uniform dose-based optimisation (DV-gEUD plan). Methods The quality and performance of the DV plan and DV-gEUD plan using the Pinnacle3® system (Philips, Fitchburg, WI) were evaluated and compared in 10 patients with stage T2–T4 BBC. The plans were delivered on a Varian 21EX linear accelerator (Varian Medical Systems, Milpitas, CA) equipped with a Millennium 120 leaf multileaf collimator (Varian Medical Systems). The parameters analysed included the conformity index, homogeneity index, tumour control probability of the planning target volume (PTV), the volumes V20 Gy and V30 Gy of the organs at risk (OAR, including the heart and lungs), mean dose and the normal tissue complication probability. Results Both plans met the requirements for the coverage of PTV with similar conformity and homogeneity indices. However, the DV-gEUD plan had the advantage of dose sparing for OAR: the mean doses of the heart and lungs, lung V20 Gy, and heart V30 Gy in the DV-gEUD plan were lower than those in the DV plan (p<0.05). Conclusions A better result can be obtained by starting with a DV-generated plan and then improving it by adding gEUD-based improvements to reduce the number of iterations and to improve the optimum dose distribution. Advances to knowledge The DV-gEUD plan provided superior dosimetric results for treating BBC in terms of PTV coverage and OAR sparing than the DV plan, without sacrificing the homogeneity of dose distribution in the PTV. PMID:23091290
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SU-F-T-634: Feasibility Study of Respiratory Gated RapidArc SBRT Using a 6MV FFF Photon Beam
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dou, K; Safaraz, M; Rodgers, J
Purpose: To conduct a feasibility study on retrospective respiratory gating and marker tracking for lung stereotactic body radiotherapy (SBRT) with a gated RapidArc delivery using a 6MV flattened filter free photon mode. Methods: A CIRS dynamic thorax phantom Model 008A with different inserts was used for treatment planning and respiratory gating. 4D CT had a free breathing simulation followed by a respiration gated, ten phased CT using a Philips Brilliance CT with a Varian RPM respiratory gating system. The internal target volume was created from the ten phase gated CT images, followed by exporting to a Varian Eclipse TPS v11more » for treatment planning on the free breath images. Both MIP and AIP were also generated for comparison of planning and target motion tracking. The planned dose was delivered with a 6MV FFF photon beam from a Varian TrueBeam accelerator. Gated target motion was also verified by tracking the implanted makers during delivery using continuous kV imaging in addition to CBCT, kV and MV localization and verification. Results: Gating was studied in three situations of lower, normal, and faster breathing at a respiratory cycle of 5, 15 and 25 breaths per minute, respectively. 4D treatment planning was performed at a normal breathing of 15 breaths per minute. The gated patterns obtained using the TrueBeam IR camera were compared with the planned ones while gating operation was added prior to delivery . Gating was realized only when the measured respiratory patterns matched to the planned ones. The gated target motion was verified within the tolerance by kV and MV imaging. Either free breathing CT or averaged CT images were studied to be good for image guidance to align the target. Conclusion: Gated RapidArc SBRT delivered with a 6MV FFF photon beam is realized using a dynamic lung phantom.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Gao, S; Balter, P; Wang, X
2015-06-15
Purpose: To determine the best dosimetric metric measured by our routine QA devices for diagnosing photon target failure on a Varian C-series linac. Methods: We have retrospectively reviewed and analyzed the dosimetry data from a Varian linac with a target degradation that was undiagnosed for one year. A failure in the daily QA symmetry tests was the first indication of an issue. The beam was steered back to a symmetric shape and water scans indicated the beam energy had changed but stayed within the manufacturer’s specifications and agreed reasonably with our treatment planning system data. After the problem was identifiedmore » and the target was replaced, we retrospectively analyzed our QA data including diagonals normalized flatness (F-DN) from the daily device (DQA3), profiles from an ionization chamber array (IC Profiler), as well as profiles and PDDs from a 3D water Scanner (3DS). These metrics were cross-compared to determine which was the best early indicator of target degradation. Results: A 3% change in FDN measured by the DQA3 was found to be an early indicator of target degradation. It is more sensitive than changes in output, symmetry, flatness or PDD. All beam shape metrics (flatness at dmax and 10 cm depth, and F-DN) indicated an energy increase while the PDD indicated an energy decrease. This disagreement between the beam-shape based energy metrics (F-DN and flatness) and PDD based energy metric may indicate target failure as opposed to an energy change resulting from changes in the incident electron energy. Conclusion: Photon target degradation has been identified as a failure mode for linacs. The manufacturer’s test for this condition is highly invasive and requires machine down time. We have demonstrated that the condition could be caught early based upon data acquired during routine QA activities, such as the F-DN.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhang, Ruohui; Department of Medical Physics, Medical Faculty Mannheim, Heidelberg University; Fan, Xiaomei
2014-08-15
Objective: The purpose of this study is to propose an alternative planning approach for VMAT using constant dose rate and gantry speed arc therapy(CDR-CAS-IMAT) implementation on conventional Linac Varian 23EX and used IMRT as a benchmark to evaluate the performance. Methods and materials: Eighteen patients with thoracic esophageal carcinoma who were previously treated with IMRT on Varian 23EX were retrospectively planned for CDR-CAS-IMAT plans. Dose prescription was set to 60 Gy to PTVs in 30 fractions. The planning objectives for PTVs and OAR were corresponding with the IMRT plans. Dose to the PTVs and OAR were compared to IMRT withmore » respect to plan quality, MU, treatment time and delivery accuracy. Results: CDR-CAS-IMAT plans led to equivalent or superior plan quality as compared to IMRT, PTV's CI relative increased 16.2%, while small deviations were observed on minimum dose for PTV. Volumes in the cord receiving 40Gy were increased from 3.6% with IMRT to 7.0%. Treatment times were reduced significantly with CDR-CAS-IMAT(mean 85.7s vs. 232.1s, p < .05), however, MU increased by a factor of 1.3 and lung V10/5/3.5/aver were relative increase 6.7%,12%,17.9%,4.2%, respectively. And increased the E-P low dose area volume decreased the hight dose area. There were no significant difference in Delta4 measurements results between both planning techniques. Conclusion: CDR-CAS-IMAT plans can be implemented smoothly and quickly into a busy cancer center, which improved PTV CI and reduces treatment time but increased the MU and low dose irradiated area. An evaluation of weight loss must be performed during treatment for CDR-CAS-IMAT patients.« less
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Optimized Varian aSi portal dosimetry: development of datasets for collective use.
Van Esch, Ann; Huyskens, Dominique P; Hirschi, Lukas; Baltes, Christof
2013-11-04
Although much literature has been devoted to portal dosimetry with the Varian amorphous silicon (aSi) portal imager, the majority of the described methods are not routinely adopted because implementation procedures are cumbersome and not within easy reach of most radiotherapy centers. To make improved portal dosimetry solutions more generally available, we have investigated the possibility of converting optimized configurations into ready-to-use standardized datasets. Firstly, for all commonly used photon energies (6, 10, 15, 18, and 20 MV), basic beam data acquired on 20 aSi panels were used to assess the interpanel reproducibility. Secondly, a standardized portal dose image prediction (PDIP) algorithm configuration was created for every energy, using a three-step process to optimize the aSi dose response function and profile correction files for the dosimetric calibration of the imager panel. An approximate correction of the backscatter of the Exact arm was also incorporated. Thirdly, a set of validation fields was assembled to assess the accuracy of the standardized configuration. Variations in the basic beam data measured on different aSi panels very rarely exceeded 2% (2 mm) and are of the same order of magnitude as variations between different Clinacs when measuring in reference conditions in water. All studied aSi panels can hence be regarded as nearly identical. Standardized datasets were successfully created and implemented. The test package proved useful in highlighting possible problems and illustrating remaining limitations, but also in demonstrating the good overall results (95% pass rate for 3%,3 mm) that can be obtained. The dosimetric behavior of all tested aSi panels was found to be nearly identical for all tested energies. The approach of using standardized datasets was then successfully tested through the creation and evaluation of PDIP preconfigured datasets that can be used within the Varian portal dosimetry solution.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Borges, C.; Zarza-Moreno, M.; Heath, E.
2012-01-15
Purpose: The most recent Varian micro multileaf collimator (MLC), the High Definition (HD120) MLC, was modeled using the BEAMNRC Monte Carlo code. This model was incorporated into a Varian medical linear accelerator, for a 6 MV beam, in static and dynamic mode. The model was validated by comparing simulated profiles with measurements. Methods: The Varian Trilogy (2300C/D) accelerator model was accurately implemented using the state-of-the-art Monte Carlo simulation program BEAMNRC and validated against off-axis and depth dose profiles measured using ionization chambers, by adjusting the energy and the full width at half maximum (FWHM) of the initial electron beam. Themore » HD120 MLC was modeled by developing a new BEAMNRC component module (CM), designated HDMLC, adapting the available DYNVMLC CM and incorporating the specific characteristics of this new micro MLC. The leaf dimensions were provided by the manufacturer. The geometry was visualized by tracing particles through the CM and recording their position when a leaf boundary is crossed. The leaf material density and abutting air gap between leaves were adjusted in order to obtain a good agreement between the simulated leakage profiles and EBT2 film measurements performed in a solid water phantom. To validate the HDMLC implementation, additional MLC static patterns were also simulated and compared to additional measurements. Furthermore, the ability to simulate dynamic MLC fields was implemented in the HDMLC CM. The simulation results of these fields were compared with EBT2 film measurements performed in a solid water phantom. Results: Overall, the discrepancies, with and without MLC, between the opened field simulations and the measurements using ionization chambers in a water phantom, for the off-axis profiles are below 2% and in depth-dose profiles are below 2% after the maximum dose depth and below 4% in the build-up region. On the conditions of these simulations, this tungsten-based MLC has a density of 18.7 g cm{sup -3} and an overall leakage of about 1.1 {+-} 0.03%. The discrepancies between the film measured and simulated closed and blocked fields are below 2% and 8%, respectively. Other measurements were performed for alternated leaf patterns and the agreement is satisfactory (to within 4%). The dynamic mode for this MLC was implemented and the discrepancies between film measurements and simulations are within 4%. Conclusions: The Varian Trilogy (2300 C/D) linear accelerator including the HD120 MLC was successfully modeled and simulated using the Monte Carlo BEAMNRC code by developing an independent CM, the HDMLC CM, either in static and dynamic modes.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Keller, J; Hardin, M; Giaddui, T
Purpose: To test whether unified vendor specified beam conformance for matched machines implies volumetric modulated arc radiotherapy(VMAT) delivery consistency. Methods: Twenty-two identical patient QA plans, eleven 6MV and eleven 15MV, were delivered to the Delta{sup 4}(Scandidos, Uppsala, Sweden) on two Varian TrueBEAM matched machines. Sixteen patient QA plans, nine 6 MV and seven 10 MV, were delivered to Delta{sup 4} on two Elekta Agility matched machines. The percent dose deviation(%DDev), distance-to-agreement(DTA), and the gamma analysis(γ) were collected for all plans and the differences in measurements were tabulated between matched machines. A paired t-test analysis of the data with an alphamore » of 0.05 determines statistical significance. Power(P) was calculated to detect a difference of 5%; all data except Elekta %DDev sets were strong with above a 0.85 power. Results: The average differences for Varian machines (%DDev, DTA, and γ) are 6.4%, 1.6% and 2.7% for 6MV, respectively, and 8.0%, 0.6%, and 2.5% for 15MV. The average differences for matched Elekta machines (%DDev, DTA, and γ) are 10.2%, 0.6% and 0.9% for 6 MV, respectively, and 7.0%, 1.9%, and 2.8% for 10MV.A paired t-test shows for Varian the %DDev difference is significant for 6MV and 15MV(p-value6MV=0.019, P6MV=0.96; p-value15MV=0.0003, P15MV=0.86). Differences in DTA are insignificant for both 6MV and 15MV(p-value6MV=0.063, P6MV=1; p-value15MV=0.907, P15MV=1). Varian differences in gamma are significant for both energies(p-value6MV=0.025, P6MV=0.99; p-value15MV=0.013, P15MV=1). A paired t-test shows for Elekta the difference in %DDev is significant for 6MV but not 10MV(p-value6MV=0.00065, P6MV=0.68; p-value10MV=0.262, P10MV=0.39). Differences in DTA are statistically insignificant(p-value6MV=0.803, P6MV = 1; p-value10MV=0.269, P10MV=1). Elekta differences in gamma are significant for 10MV only(p-value6MV=0.094, P6MV=1; p-value10MV=0.011, P10MV=1). Conclusion: These results show vendor specified beam conformance across machines does not ensure equivalent patient specific QA pass rates. Gamma differences are statistically significant in three of the four comparisons for two pairs of vendor matched machines.« less
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Mukumoto, Nobutaka; Tsujii, Katsutomo; Saito, Susumu; Yasunaga, Masayoshi; Takegawa, Hideki; Yamamoto, Tokihiro; Numasaki, Hodaka; Teshima, Teruki
2009-10-01
To develop an infrastructure for the integrated Monte Carlo verification system (MCVS) to verify the accuracy of conventional dose calculations, which often fail to accurately predict dose distributions, mainly due to inhomogeneities in the patient's anatomy, for example, in lung and bone. The MCVS consists of the graphical user interface (GUI) based on a computational environment for radiotherapy research (CERR) with MATLAB language. The MCVS GUI acts as an interface between the MCVS and a commercial treatment planning system to import the treatment plan, create MC input files, and analyze MC output dose files. The MCVS consists of the EGSnrc MC codes, which include EGSnrc/BEAMnrc to simulate the treatment head and EGSnrc/DOSXYZnrc to calculate the dose distributions in the patient/phantom. In order to improve computation time without approximations, an in-house cluster system was constructed. The phase-space data of a 6-MV photon beam from a Varian Clinac unit was developed and used to establish several benchmarks under homogeneous conditions. The MC results agreed with the ionization chamber measurements to within 1%. The MCVS GUI could import and display the radiotherapy treatment plan created by the MC method and various treatment planning systems, such as RTOG and DICOM-RT formats. Dose distributions could be analyzed by using dose profiles and dose volume histograms and compared on the same platform. With the cluster system, calculation time was improved in line with the increase in the number of central processing units (CPUs) at a computation efficiency of more than 98%. Development of the MCVS was successful for performing MC simulations and analyzing dose distributions.
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Chi, Yujie; Tian, Zhen; Jia, Xun
2016-08-07
Monte Carlo (MC) particle transport simulation on a graphics-processing unit (GPU) platform has been extensively studied recently due to the efficiency advantage achieved via massive parallelization. Almost all of the existing GPU-based MC packages were developed for voxelized geometry. This limited application scope of these packages. The purpose of this paper is to develop a module to model parametric geometry and integrate it in GPU-based MC simulations. In our module, each continuous region was defined by its bounding surfaces that were parameterized by quadratic functions. Particle navigation functions in this geometry were developed. The module was incorporated to two previously developed GPU-based MC packages and was tested in two example problems: (1) low energy photon transport simulation in a brachytherapy case with a shielded cylinder applicator and (2) MeV coupled photon/electron transport simulation in a phantom containing several inserts of different shapes. In both cases, the calculated dose distributions agreed well with those calculated in the corresponding voxelized geometry. The averaged dose differences were 1.03% and 0.29%, respectively. We also used the developed package to perform simulations of a Varian VS 2000 brachytherapy source and generated a phase-space file. The computation time under the parameterized geometry depended on the memory location storing the geometry data. When the data was stored in GPU's shared memory, the highest computational speed was achieved. Incorporation of parameterized geometry yielded a computation time that was ~3 times of that in the corresponding voxelized geometry. We also developed a strategy to use an auxiliary index array to reduce frequency of geometry calculations and hence improve efficiency. With this strategy, the computational time ranged in 1.75-2.03 times of the voxelized geometry for coupled photon/electron transport depending on the voxel dimension of the auxiliary index array, and in 0.69-1.23 times for photon only transport.
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Qin, Nan; Shen, Chenyang; Tsai, Min-Yu; Pinto, Marco; Tian, Zhen; Dedes, Georgios; Pompos, Arnold; Jiang, Steve B; Parodi, Katia; Jia, Xun
2018-01-01
One of the major benefits of carbon ion therapy is enhanced biological effectiveness at the Bragg peak region. For intensity modulated carbon ion therapy (IMCT), it is desirable to use Monte Carlo (MC) methods to compute the properties of each pencil beam spot for treatment planning, because of their accuracy in modeling physics processes and estimating biological effects. We previously developed goCMC, a graphics processing unit (GPU)-oriented MC engine for carbon ion therapy. The purpose of the present study was to build a biological treatment plan optimization system using goCMC. The repair-misrepair-fixation model was implemented to compute the spatial distribution of linear-quadratic model parameters for each spot. A treatment plan optimization module was developed to minimize the difference between the prescribed and actual biological effect. We used a gradient-based algorithm to solve the optimization problem. The system was embedded in the Varian Eclipse treatment planning system under a client-server architecture to achieve a user-friendly planning environment. We tested the system with a 1-dimensional homogeneous water case and 3 3-dimensional patient cases. Our system generated treatment plans with biological spread-out Bragg peaks covering the targeted regions and sparing critical structures. Using 4 NVidia GTX 1080 GPUs, the total computation time, including spot simulation, optimization, and final dose calculation, was 0.6 hour for the prostate case (8282 spots), 0.2 hour for the pancreas case (3795 spots), and 0.3 hour for the brain case (6724 spots). The computation time was dominated by MC spot simulation. We built a biological treatment plan optimization system for IMCT that performs simulations using a fast MC engine, goCMC. To the best of our knowledge, this is the first time that full MC-based IMCT inverse planning has been achieved in a clinically viable time frame. Copyright © 2017 Elsevier Inc. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Muralidhar, K Raja; Pangam, Suresh; Ponaganti, Srinivas
2016-06-15
Purpose: 1. online verification of patient position during treatment using calypso electromagnetic localization and tracking system. 2. Verification and comparison of positional accuracy between cone beam computed tomography and calypso system. 3. Presenting the advantage of continuation localization in Stereotactic radiosurgery treatments. Methods: Ten brain tumor cases were taken for this study. Patients with head mask were under gone Computed Tomography (CT). Before scanning, mask was cut on the fore head area to keep surface beacons on the skin. Slice thickness of 0.65 mm were taken for this study. x, y, z coordinates of these beacons in TPS were enteredmore » into tracking station. Varian True Beam accelerator, equipped with On Board Imager was used to take Cone beam Computed Tomography (CBCT) to localize the patient. Simultaneously Surface beacons were used to localize and track the patient throughout the treatment. The localization values were compared in both systems. For localization CBCT considered as reference. Tracking was done throughout the treatment using Calypso tracking system using electromagnetic array. This array was in tracking position during imaging and treatment. Flattening Filter free beams of 6MV photons along with Volumetric Modulated Arc Therapy was used for the treatment. The patient movement was observed throughout the treatment ranging from 2 min to 4 min. Results: The average variation observed between calypso system and CBCT localization was less than 0.5 mm. These variations were due to manual errors while keeping beacon on the patient. Less than 0.05 cm intra-fraction motion was observed throughout the treatment with the help of continuous tracking. Conclusion: Calypso target localization system is one of the finest tools to perform radiosurgery in combination with CBCT. This non radiographic method of tracking is a real beneficial method to treat patients confidently while observing real-time motion information of the patient.« less
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CBH1 homologs and varian CBH1 cellulase
Goedegebuur, Frits; Gualfetti, Peter; Mitchinson, Colin; Neefe, Paulien
2014-07-01
Disclosed are a number of homologs and variants of Hypocrea jecorina Cel7A (formerly Trichoderma reesei cellobiohydrolase I or CBH1), nucleic acids encoding the same and methods for producing the same. The homologs and variant cellulases have the amino acid sequence of a glycosyl hydrolase of family 7A wherein one or more amino acid residues are substituted and/or deleted.
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Zinc uptake and regulation by the sublittoral prawn Pandalus montagui (Crustacea: Decapoda)
NASA Astrophysics Data System (ADS)
Nugegoda, D.; Rainbow, P. S.
1988-06-01
The sublittoral decapod crustacean Pandalus montagui Leach in artificial seawater at 10°C regulates the total body zinc concentration to a constant level in dissolved zinc concentrations up to ca. 22 μg Zn l -1, beyond which there is net accumulation of body zinc. This threshold of zinc regulation breakdown is lower than that in the littoral decapods Palaemon elegans (ca. 93 μg Zn l -1) and Palaemonetes varians (ca. 190 μg Zn l -1) under the same physico-chemical conditions. Correspondingly, zinc uptake rates of the three species of decapods decrease in the order P. montagui > P. elegans > P. varians. It is concluded that regulation of total body zinc concentration is more efficient in decapods adapted to the fluctuating environments of littoral habitats, possibly as a result of changes in permeability of uptake surfaces in combination with improved zinc excretion systems. The moult cycle is important in determining the ability of an individual prawn to regulate zinc. Body zinc in Pandalus montagui consists of at least two pools of zinc exchanging at different rates which the environment. Zinc and copper are not evenly distributed in the tissues of P. montagui.
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Stackebrandt, E; Koch, C; Gvozdiak, O; Schumann, P
1995-10-01
The results of a phylogenetic and chemotaxonomic analysis of the genus Micrococcus indicated that it is significantly heterogeneous. Except for Micrococcus lylae, no species groups phylogenetically with the type species of the genus, Micrococcus luteus. The other members of the genus form three separate phylogenetic lines which on the basis of chemotaxonomic properties can be assigned to four genera. These genera are the genus Kocuria gen. nov. for Micrococcus roseus, Micrococcus varians, and Micrococcus kristinae, described as Kocuria rosea comb. nov., Kocuria varians comb. nov., and Kocuria kristinae comb. nov., respectively; the genus Nesterenkonia gen. nov. for Micrococcus halobius, described as Nesterenkonia halobia comb. nov.; the genus Nesterenkonia gen. nov. for Micrococcus halobius, described as Nesterenkonia halobia comb. nov.; the genus Dermacoccus gen. nov. for Micrococcus nishinomiyaensis, described as Dermacoccus nishinomiyaensis comb. nov.; and the genus Kytocossus gen. nov. for Micrococcus sedentarius, described as Kytococcus sedentarius comb. nov. M. luteus and M. lylae, which are closely related phylogenetically but differ in some chemotaxonomic properties, are the only species that remain in the genus Micrococcus Cohn 1872. An emended description of the genus Micrococcus is given [corrected].
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NASA Astrophysics Data System (ADS)
Rit, S.; Vila Oliva, M.; Brousmiche, S.; Labarbe, R.; Sarrut, D.; Sharp, G. C.
2014-03-01
We propose the Reconstruction Toolkit (RTK, http://www.openrtk.org), an open-source toolkit for fast cone-beam CT reconstruction, based on the Insight Toolkit (ITK) and using GPU code extracted from Plastimatch. RTK is developed by an open consortium (see affiliations) under the non-contaminating Apache 2.0 license. The quality of the platform is daily checked with regression tests in partnership with Kitware, the company supporting ITK. Several features are already available: Elekta, Varian and IBA inputs, multi-threaded Feldkamp-David-Kress reconstruction on CPU and GPU, Parker short scan weighting, multi-threaded CPU and GPU forward projectors, etc. Each feature is either accessible through command line tools or C++ classes that can be included in independent software. A MIDAS community has been opened to share CatPhan datasets of several vendors (Elekta, Varian and IBA). RTK will be used in the upcoming cone-beam CT scanner developed by IBA for proton therapy rooms. Many features are under development: new input format support, iterative reconstruction, hybrid Monte Carlo / deterministic CBCT simulation, etc. RTK has been built to freely share tomographic reconstruction developments between researchers and is open for new contributions.
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Evaluation of the new respiratory gating system
Shi, Chengyu; Tang, Xiaoli; Chan, Maria
2018-01-01
Objective The newly released Respiratory Gating for Scanners (RGSC; Varian Medical Systems, Palo Alto, CA, USA) system has limited existing quality assurance (QA) protocols and pertinent publications. Herein, we report our experiences of the RGSC system acceptance and QA. Methods The RGSC system integration was tested with peripheral equipment, spatial reproducibility, and dynamic localization accuracy for regular and irregular breathing patterns, respectively. A QUASAR Respiratory Motion Phantom and a mathematical fitting method were used for data acquisition and analysis. Results The results showed that the RGSC system could accurately measure regular motion periods of 3–10 s. For irregular breathing patterns, differences from the existing Real-time Position Management (RPM; Varian Medical Systems, Palo Alto, CA) system were observed. For dynamic localization measurements, the RGSC system showed 76% agreement with the programmed test data within ±5% tolerance in terms of fitting period. As s comparison, the RPM system showed 66% agreement within ±5% tolerance, and 65% for the RGSC versus RPM measurements. Conclusions New functions and positioning accuracy improve the RGSC system’s ability to achieve higher dynamic treatment precision. A 4D phantom is helpful for the QA tests. Further investigation is required for the whole RGSC system performance QA. PMID:29722356
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MO-FG-202-01: A Fast Yet Sensitive EPID-Based Real-Time Treatment Verification System
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ahmad, M; Nourzadeh, H; Neal, B
2016-06-15
Purpose: To create a real-time EPID-based treatment verification system which robustly detects treatment delivery and patient attenuation variations. Methods: Treatment plan DICOM files sent to the record-and-verify system are captured and utilized to predict EPID images for each planned control point using a modified GPU-based digitally reconstructed radiograph algorithm which accounts for the patient attenuation, source energy fluence, source size effects, and MLC attenuation. The DICOM and predicted images are utilized by our C++ treatment verification software which compares EPID acquired 1024×768 resolution frames acquired at ∼8.5hz from Varian Truebeam™ system. To maximize detection sensitivity, image comparisons determine (1) ifmore » radiation exists outside of the desired treatment field; (2) if radiation is lacking inside the treatment field; (3) if translations, rotations, and magnifications of the image are within tolerance. Acquisition was tested with known test fields and prior patient fields. Error detection was tested in real-time and utilizing images acquired during treatment with another system. Results: The computational time of the prediction algorithms, for a patient plan with 350 control points and 60×60×42cm^3 CT volume, is 2–3minutes on CPU and <27 seconds on GPU for 1024×768 images. The verification software requires a maximum of ∼9ms and ∼19ms for 512×384 and 1024×768 resolution images, respectively, to perform image analysis and dosimetric validations. Typical variations in geometric parameters between reference and the measured images are 0.32°for gantry rotation, 1.006 for scaling factor, and 0.67mm for translation. For excess out-of-field/missing in-field fluence, with masks extending 1mm (at isocenter) from the detected aperture edge, the average total in-field area missing EPID fluence was 1.5mm2 the out-of-field excess EPID fluence was 8mm^2, both below error tolerances. Conclusion: A real-time verification software, with EPID images prediction algorithm, was developed. The system is capable of performing verifications between frames acquisitions and identifying source(s) of any out-of-tolerance variations. This work was supported in part by Varian Medical Systems.« less
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SU-F-BRA-12: End-User Oriented Tools and Procedures for Testing Brachytherapy TPSs Employing MBDCAs
DOE Office of Scientific and Technical Information (OSTI.GOV)
Peppa, V; Pappas, E; Lahanas, V
2015-06-15
Purpose: To develop user-oriented tools for commissioning and dosimetry testing of {sup 192}Ir brachytherapy treatment planning systems (TPSs) employing model based dose calculation algorithms (MBDCAs). Methods: A software tool (BrachyGuide) has been developed for the automatic generation of MCNP6 input files from any CT based plan exported in DICOM RT format from Elekta and Varian TPSs. BrachyGuide also facilitates the evaluation of imported Monte Carlo (MC) and TPS dose distributions in terms of % dose differences and gamma index (CT overlaid colormaps or relative frequency plots) as well as DVHs and related indices. For users not equipped to perform MC,more » a set of computational models was prepared in DICOM format, accompanied by treatment plans and corresponding MCNP6 generated reference data. BrachyGuide can then be used to compare institutional and reference data as per TG186. The model set includes a water sphere with the MBDCA WG {sup 192}Ir source placed centrically and in two eccentric positions, a water sphere with cubic bone and lung inhomogeneities and a five source dwells plan, and a patient equivalent model with an Accelerated Partial Breast Irradiation (APBI) plan. Results: The tools developed were used for the dosimetry testing of the Acuros and ACE MBDCAs implemented in BrachyVision v.13 and Oncentra Brachy v.4.5, respectively. Findings were consistent with previous results in the literature. Besides points close to the source dwells, Acuros was found to agree within type A uncertainties with the reference MC results. Differences greater than MC type A uncertainty were observed for ACE at distances >5cm from the source dwells and in bone. Conclusion: The tools developed are efficient for brachytherapy MBDCA planning commissioning and testing. Since they are appropriate for distribution over the web, they will be put at the AAPM WG MBDCA’s disposal. Research co-financed by the ESF and Greek funds. NSRF operational Program: Education and Lifelong Learning Investing in Knowledge Society-Aristeia. Varian Medical Systems and Nucletron, an Elekta company provided access to TPSs for research purposes. Miss Peppa was supported by IKY-fellowships of excellence for postgraduate studies in Greece,Siemens Program.« less
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Tumor Volume Is a Prognostic Factor in Non-Small-Cell Lung Cancer Treated With Chemoradiotherapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Alexander, Brian M.; Othus, Megan; Caglar, Hale B.
2011-04-01
Purpose: To investigate whether primary tumor and nodal volumes defined on radiotherapy planning scans are correlated with outcome (survival and recurrence) after combined-modality treatment. Methods and Materials: A retrospective review of patients with Stage III non-small-cell lung cancer treated with chemoradiation at Brigham and Women's Hospital/Dana-Farber Cancer Institute from 2000 to 2006 was performed. Tumor and nodal volume measurements, as computed by Eclipse (Varian, Palo Alto, CA), were used as independent variables, along with existing clinical factors, in univariate and multivariate analyses for association with outcomes. Results: For patients treated with definitive chemoradiotherapy, both nodal volume (hazard ratio [HR], 1.09;more » p < 0.01) and tumor volume (HR, 1.03; p < 0.01) were associated with overall survival on multivariate analysis. Both nodal volume (HR, 1.10; p < 0.01) and tumor volume (HR, 1.04; p < 0.01) were also associated with local control but not distant metastases. Conclusions: In addition to traditional surgical staging variables, disease burden, measured by primary tumor and nodal metastases volume, provides information that may be helpful in determining prognosis and identifying groups of patients for which more aggressive local therapy is warranted.« less
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WE-C-217BCD-08: Rapid Monte Carlo Simulations of DQE(f) of Scintillator-Based Detectors.
Star-Lack, J; Abel, E; Constantin, D; Fahrig, R; Sun, M
2012-06-01
Monte Carlo simulations of DQE(f) can greatly aid in the design of scintillator-based detectors by helping optimize key parameters including scintillator material and thickness, pixel size, surface finish, and septa reflectivity. However, the additional optical transport significantly increases simulation times, necessitating a large number of parallel processors to adequately explore the parameter space. To address this limitation, we have optimized the DQE(f) algorithm, reducing simulation times per design iteration to 10 minutes on a single CPU. DQE(f) is proportional to the ratio, MTF(f)̂2 /NPS(f). The LSF-MTF simulation uses a slanted line source and is rapidly performed with relatively few gammas launched. However, the conventional NPS simulation for standard radiation exposure levels requires the acquisition of multiple flood fields (nRun), each requiring billions of input gamma photons (nGamma), many of which will scintillate, thereby producing thousands of optical photons (nOpt) per deposited MeV. The resulting execution time is proportional to the product nRun x nGamma x nOpt. In this investigation, we revisit the theoretical derivation of DQE(f), and reveal significant computation time savings through the optimization of nRun, nGamma, and nOpt. Using GEANT4, we determine optimal values for these three variables for a GOS scintillator-amorphous silicon portal imager. Both isotropic and Mie optical scattering processes were modeled. Simulation results were validated against the literature. We found that, depending on the radiative and optical attenuation properties of the scintillator, the NPS can be accurately computed using values for nGamma below 1000, and values for nOpt below 500/MeV. nRun should remain above 200. Using these parameters, typical computation times for a complete NPS ranged from 2-10 minutes on a single CPU. The number of launched particles and corresponding execution times for a DQE simulation can be dramatically reduced allowing for accurate computation with modest computer hardware. NIHRO1 CA138426. Several authors work for Varian Medical Systems. © 2012 American Association of Physicists in Medicine.
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Magnetized Target Fusion - Field Reversed Configuration Formation and Injection (MTF-FRC)
2009-11-06
from accidental breakage and personnel from injury in that event. The pumps for the vacuum system included a Varian dry scroll pump that was...a dry scroll (oil-free) mechanical pump could be used, as mTorr pressures would be sufficient for the vacuum switch voltage hold-off and operation...56 FIGURE 46. ROUGHING PUMP AND VACUUM -GAUGE CONTROLLERS BENEATH THETA COIL CABLE HEADER
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Targeted Radiation Therapy for Cancer Initiative
2016-09-01
grant continues to facilitate continuing medical education for the staff at MAMC on image -guided radiotherapy. A site visit to the Varian Medical ...CONTRACTING ORGANIZATION: Geneva Foundation Tacoma, WA REPORT DATE: September 2016 TYPE OF REPORT: Annual PREPARED FOR: U.S. Army Medical Research...98402 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) U.S. Army Medical Research and Materiel Command Fort
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SU-E-T-195: Commissioning the Neutron Production of a Varian TrueBeam Linac
DOE Office of Scientific and Technical Information (OSTI.GOV)
Irazola, L; Brualla, L; Rosello, J
2015-06-15
Purpose: The purpose of this work is the characterization of a new Varian TrueBeam™ facility in terms of neutron production, in order to estimate neutron equivalent dose in organs during radiotherapy treatments. Methods: The existing methodology [1] was used with the reference SRAMnd detector, calibrated in terms of thermal neutron fluence at the reference field operated by PTB (Physikalisch-Technische-Bundesanstalt) at the GeNF (Geesthacht-Neutron-Facility) with the GKSS reactor FRG-1 [2]. Thermal neutron fluence for the 5 available possibilities was evaluated: 15 MV and 10&6 MV with and without Flattening Filter (FF and FFF, respectively). Irradiation conditions are as described in [3].more » In addition, three different collimator-MLC configurations were studied for 15 MV: (a) collimator of 10×10 cm{sup 2} and MLC fully retracted (reference), (b) field sizes of 20×20 cm{sup 2} and 10×10 cm{sup 2} for collimator and MLC respectively, and (c) collimator and MLC aperture of 10×10 cm{sup 2}. Results: Thermal fluence rate at the “reference point” [3], as a consequence of the neutron production, obtained for (a) conformation in 15 MV is (1.45±0.11) x10{sup 4} n•cm{sup 2}/MU. Configurations (b) and (c) gave fluences of 96.6% and 97.8% of the reference (a). Neutron production decreases up to 8.6% and 5.7% for the 10 MV FF and FFF beams, respectively. Finally, it decreases up to 2.8% and 0.1% for the 6 MV FF and FFF modes, respectively. Conclusion: This work evaluates thermal neutron production of Varian TrueBeam™ system for organ equivalent dose estimation. The small difference in collimator-MLC configuration shows the universality of the methodology [3]. A decrease in this production is shown when decreasing energy from 15 to 10 MV and an almost negligible production was found for 6 MV. Moreover, a lower neutron contribution is observed for the FFF modes.[1]Phys Med Biol,2012;57:6167–6191.[2]Radiat Meas,2010;45:1513–1517.[3]Med Phys,2015;42:276–281.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Caillet, V; Colvill, E; Royal North Shore Hospital, Sydney, NSW
Purpose: The objective of this study was to investigate the dosimetric benefits of multi-leaf collimator (MLC) tracking for lung SABR treatments in end-to-end clinically realistic planning and delivery scenarios. Methods: The clinical benefits of MLC tracking were assessed using previously delivered treatment plans and physical experiments. The 10 most recent single lesion lung SABR patients were re-planned following a 4D-GTV-based real-time adaptive protocol (PTV defined as the end-of-exhalation GTV plus 5.0 mm margins). The plans were delivered on a Trilogy Varian linac. Electromagnetic transponders (Calypso, Varian Medical Systems, USA) were embedded into a programmable moving phantom (HexaMotion platform) tracked withmore » the Varian Calypso system. For each physical experiment, the MLC positions were collected and used as input for dose reconstruction. For both planned and physical experiments, the OAR dose metrics from the conventional and real-time adaptive SABR plans (Mean Lung Dose (MLD), V20 for lung, and near-maximum dose (D2%) for spine and heart) were statistically compared. The Wilcoxon test was used to compare plan and physical experiment dose metrics. Results: While maintaining target coverage, percentage reductions in dose metrics to the OARs were observed for both planned and physical experiments. Comparing the two plans showed MLD percentage reduction (MLDr) of 25.4% (absolute differences of 1.41 Gy) and 28.9% (1.29%) for the V20r. D2% percentage reduction for spine and heart were respectively 27.9% (0.3 Gy) and 20.2% (0.3 Gy). For the physical experiments, MLDr was 23.9% (1.3 Gy), and V20r 37.4% (1.6%). D2% reduction for spine and heart were respectively 27.3% (0.3 Gy) and 19.6% (0.3 Gy). For both plans and physical experiments, significant OAR dose differences (p<0.05) were found between the conventional SABR and real-time adaptive plans. Conclusion: Application of MLC tracking for lung SABR patients has the potential to reduce the dose to OARs during radiation therapy.« less
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SU-E-J-189: Credentialing of IGRT Equipment and Processes for Clinical Trials
DOE Office of Scientific and Technical Information (OSTI.GOV)
Court, L; Aristophanous, M; Followill, D
2014-06-01
Purpose: Current dosimetry phantoms used for clinical trial credentialing do not directly assess IGRT processes. This work evaluates a custom-built IGRT phantom for credentialing of multiple IGRT modalities and processes. Methods: An IGRT phantom was built out of a low-density body with two inserts. Insert A is used for the CT simulation. Insert B is used for the actual treatment. The inserts contain identical targets in different locations. Relative positions are unknown to the user. The user simulates the phantom (with insert A) as they would a patient, including marking the phantom. A treatment plan is created and sent tomore » the treatment unit. The phantom (with insert B) is then positioned using local IGRT practice. Shifts (planned isocenter, if applicable, and final isocenter) are marked on the phantom using room lasers. The mechanical reproducibility of re-inserting the inserts within the phantom body was tested using repeat high-resolution CT scans. The phantom was tested at 7 centers, selected to include a wide variety of imaging equipment. Results: Mechanical reproducibility was measured as 0.5-0.9mm, depending on the direction. Approaches tested to mark (and transfer) simulation isocenter included lasers, fiducials and reflective markers. IGRT approaches included kV imaging (Varian Trilogy, Brainlab ExacTrac), kV CT (CT-on-rails), kV CBCT (Varian Trilogy, Varian Truebeam, Elekta Agility) and MV CT (Tomotherapy). Users were able to successfully use this phantom for all combinations of equipment and processes. IGRT-based shifts agreed with the truth within 0.8mm, 0.8mm and 1.9mm in the LR, AP, and SI directions, respectively. Conclusion: Based on these preliminary results, the IGRT phantom can be used for credentialing of clinical trials with an action level of 1mm in AP and LR directions, and 2mm in the SI direction, consistent with TG142. We are currently testing with additional institutions with different equipment and processes, including Cyberknife. This project was funded by the Cancer Prevention Research Institute of Texas.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Vazquez Quino, L; Huerta Hernandez, C; Morrow, A
2016-06-15
Purpose: To evaluate the use of MobiusFX as a pre-treatment verification IMRT QA tool and compare it with a commercial 4D detector array for VMAT plan QA. Methods: 15 VMAT plan QA of different treatment sites were delivered and measured by traditional means with the 4D detector array ArcCheck (Sun Nuclear corporation) and at the same time measurement in linac treatment logs (Varian Dynalogs files) were analyzed from the same delivery with MobiusFX software (Mobius Medical Systems). VMAT plan QAs created in Eclipse treatment planning system (Varian) in a TrueBeam linac machine (Varian) were delivered and analyzed with the gammamore » analysis routine from SNPA software (Sun Nuclear corporation). Results: Comparable results in terms of the gamma analysis with 99.06% average gamma passing with 3%,3mm passing rate is observed in the comparison among MobiusFX, ArcCheck measurements, and the Treatment Planning System dose calculated. When going to a stricter criterion (1%,1mm) larger discrepancies are observed in different regions of the measurements with an average gamma of 66.24% between MobiusFX and ArcCheck. Conclusion: This work indicates the potential for using MobiusFX as a routine pre-treatment patient specific IMRT method for quality assurance purposes and its advantages as a phantom-less method which reduce the time for IMRT QA measurement. MobiusFX is capable of produce similar results of those by traditional methods used for patient specific pre-treatment verification VMAT QA. Even the gamma results comparing to the TPS are similar the analysis of both methods show that the errors being identified by each method are found in different regions. Traditional methods like ArcCheck are sensitive to setup errors and dose difference errors coming from the linac output. On the other hand linac log files analysis record different errors in the VMAT QA associated with the MLCs and gantry motion that by traditional methods cannot be detected.« less
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A comparison of phantom scatter from flattened and flattening filter free high-energy photon beams
DOE Office of Scientific and Technical Information (OSTI.GOV)
Richmond, Neil, E-mail: neil.richmond@stees.nhs.uk; Allen, Vince; Daniel, Jim
2015-04-01
Flattening filter free (FFF) photon beams have different dosimetric properties from those of flattened beams. The aim of this work was to characterize the collimator scatter (S{sub c}) and total scatter (S{sub cp}) from 3 FFF beams of differing quality indices and use the resulting mathematical fits to generate phantom scatter (S{sub p}) data. The similarities and differences between S{sub p} of flattened and FFF beams are described. S{sub c} and S{sub cp} data were measured for 3 flattened and 3 FFF high-energy photon beams (Varian 6 and 10 MV and Elekta 6 MV). These data were fitted to logarithmicmore » power law functions with 4 numerical coefficients. The agreement between our experimentally determined flattened beam S{sub p} and published data was within ± 1.2% for all 3 beams investigated and all field sizes from 4 × 4 to 40 × 40 cm{sup 2}. For the FFF beams, S{sub p} was only within 1% of the same flattened beam published data for field sizes between 6 × 6 and 14 × 14 cm{sup 2}. Outside this range, the differences were much greater, reaching − 3.2%, − 4.5%, and − 4.3% for the fields of 40 × 40 cm{sup 2} for the Varian 6-MV, Varian 10-MV, and Elekta 6-MV FFF beams, respectively. The FFF beam S{sub p} increased more slowly with increasing field size than that of the published and measured flattened beam of a similar reference field size quality index, i.e., there is less Phantom Scatter than that found with flattened beams for a given field size. This difference can be explained when the fluence profiles of the flattened and FFF beams are considered. The FFF beam has greatly reduced fluence off axis, especially as field size increases, compared with the flattened beam profile; hence, less scatter is generated in the phantom reaching the central axis.« less
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A Varian DynaLog file-based procedure for patient dose-volume histogram-based IMRT QA.
Calvo-Ortega, Juan F; Teke, Tony; Moragues, Sandra; Pozo, Miquel; Casals-Farran, Joan
2014-03-06
In the present study, we describe a method based on the analysis of the dynamic MLC log files (DynaLog) generated by the controller of a Varian linear accelerator in order to perform patient-specific IMRT QA. The DynaLog files of a Varian Millennium MLC, recorded during an IMRT treatment, can be processed using a MATLAB-based code in order to generate the actual fluence for each beam and so recalculate the actual patient dose distribution using the Eclipse treatment planning system. The accuracy of the DynaLog-based dose reconstruction procedure was assessed by introducing ten intended errors to perturb the fluence of the beams of a reference plan such that ten subsequent erroneous plans were generated. In-phantom measurements with an ionization chamber (ion chamber) and planar dose measurements using an EPID system were performed to investigate the correlation between the measured dose changes and the expected ones detected by the reconstructed plans for the ten intended erroneous cases. Moreover, the method was applied to 20 cases of clinical plans for different locations (prostate, lung, breast, and head and neck). A dose-volume histogram (DVH) metric was used to evaluate the impact of the delivery errors in terms of dose to the patient. The ionometric measurements revealed a significant positive correlation (R² = 0.9993) between the variations of the dose induced in the erroneous plans with respect to the reference plan and the corresponding changes indicated by the DynaLog-based reconstructed plans. The EPID measurements showed that the accuracy of the DynaLog-based method to reconstruct the beam fluence was comparable with the dosimetric resolution of the portal dosimetry used in this work (3%/3 mm). The DynaLog-based reconstruction method described in this study is a suitable tool to perform a patient-specific IMRT QA. This method allows us to perform patient-specific IMRT QA by evaluating the result based on the DVH metric of the planning CT image (patient DVH-based IMRT QA).
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Measurement of time delay for a prospectively gated CT simulator.
Goharian, M; Khan, R F H
2010-04-01
For the management of mobile tumors, respiratory gating is the ideal option, both during imaging and during therapy. The major advantage of respiratory gating during imaging is that it is possible to create a single artifact-free CT data-set during a selected phase of the patient's breathing cycle. The purpose of the present work is to present a simple technique to measure the time delay during acquisition of a prospectively gated CT. The time delay of a Philips Brilliance BigBore (Philips Medical Systems, Madison, WI) scanner attached to a Varian Real-Time Position Management (RPM) system (Varian Medical Systems, Palo Alto, CA) was measured. Two methods were used to measure the CT time delay: using a motion phantom and using a recorded data file from the RPM system. In the first technique, a rotating wheel phantom was altered by placing two plastic balls on its axis and rim, respectively. For a desired gate, the relative positions of the balls were measured from the acquired CT data and converted into corresponding phases. Phase difference was calculated between the measured phases and the desired phases. Using period of motion, the phase difference was converted into time delay. The Varian RPM system provides an external breathing signal; it also records transistor-transistor logic (TTL) 'X-Ray ON' status signal from the CT scanner in a text file. The TTL 'X-Ray ON' indicates the start of CT image acquisition. Thus, knowledge of the start time of CT acquisition, combined with the real-time phase and amplitude data from the external respiratory signal, provides time-stamping of all images in an axial CT scan. The TTL signal with time-stamp was used to calculate when (during the breathing cycle) a slice was recorded. Using the two approaches, the time delay between the prospective gating signal and CT simulator has been determined to be 367 +/- 40 ms. The delay requires corrections both at image acquisition and while setting gates for the treatment delivery; otherwise the simulation and treatment may not be correlated with the patient's breathing.
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Using weighted power mean for equivalent square estimation.
Zhou, Sumin; Wu, Qiuwen; Li, Xiaobo; Ma, Rongtao; Zheng, Dandan; Wang, Shuo; Zhang, Mutian; Li, Sicong; Lei, Yu; Fan, Qiyong; Hyun, Megan; Diener, Tyler; Enke, Charles
2017-11-01
Equivalent Square (ES) enables the calculation of many radiation quantities for rectangular treatment fields, based only on measurements from square fields. While it is widely applied in radiotherapy, its accuracy, especially for extremely elongated fields, still leaves room for improvement. In this study, we introduce a novel explicit ES formula based on Weighted Power Mean (WPM) function and compare its performance with the Sterling formula and Vadash/Bjärngard's formula. The proposed WPM formula is ESWPMa,b=waα+1-wbα1/α for a rectangular photon field with sides a and b. The formula performance was evaluated by three methods: standard deviation of model fitting residual error, maximum relative model prediction error, and model's Akaike Information Criterion (AIC). Testing datasets included the ES table from British Journal of Radiology (BJR), photon output factors (S cp ) from the Varian TrueBeam Representative Beam Data (Med Phys. 2012;39:6981-7018), and published S cp data for Varian TrueBeam Edge (J Appl Clin Med Phys. 2015;16:125-148). For the BJR dataset, the best-fit parameter value α = -1.25 achieved a 20% reduction in standard deviation in ES estimation residual error compared with the two established formulae. For the two Varian datasets, employing WPM reduced the maximum relative error from 3.5% (Sterling) or 2% (Vadash/Bjärngard) to 0.7% for open field sizes ranging from 3 cm to 40 cm, and the reduction was even more prominent for 1 cm field sizes on Edge (J Appl Clin Med Phys. 2015;16:125-148). The AIC value of the WPM formula was consistently lower than its counterparts from the traditional formulae on photon output factors, most prominent on very elongated small fields. The WPM formula outperformed the traditional formulae on three testing datasets. With increasing utilization of very elongated, small rectangular fields in modern radiotherapy, improved photon output factor estimation is expected by adopting the WPM formula in treatment planning and secondary MU check. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
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Kerns, James R; Followill, David S; Lowenstein, Jessica; Molineu, Andrea; Alvarez, Paola; Taylor, Paige A; Stingo, Francesco C; Kry, Stephen F
2016-05-01
Accurate data regarding linear accelerator (Linac) radiation characteristics are important for treatment planning system modeling as well as regular quality assurance of the machine. The Imaging and Radiation Oncology Core-Houston (IROC-H) has measured the dosimetric characteristics of numerous machines through their on-site dosimetry review protocols. Photon data are presented and can be used as a secondary check of acquired values, as a means to verify commissioning a new machine, or in preparation for an IROC-H site visit. Photon data from IROC-H on-site reviews from 2000 to 2014 were compiled and analyzed. Specifically, data from approximately 500 Varian machines were analyzed. Each dataset consisted of point measurements of several dosimetric parameters at various locations in a water phantom to assess the percentage depth dose, jaw output factors, multileaf collimator small field output factors, off-axis factors, and wedge factors. The data were analyzed by energy and parameter, with similarly performing machine models being assimilated into classes. Common statistical metrics are presented for each machine class. Measurement data were compared against other reference data where applicable. Distributions of the parameter data were shown to be robust and derive from a student's t distribution. Based on statistical and clinical criteria, all machine models were able to be classified into two or three classes for each energy, except for 6 MV for which there were eight classes. Quantitative analysis of the measurements for 6, 10, 15, and 18 MV photon beams is presented for each parameter; supplementary material has also been made available which contains further statistical information. IROC-H has collected numerous data on Varian Linacs and the results of photon measurements from the past 15 years are presented. The data can be used as a comparison check of a physicist's acquired values. Acquired values that are well outside the expected distribution should be verified by the physicist to identify whether the measurements are valid. Comparison of values to this reference data provides a redundant check to help prevent gross dosimetric treatment errors.
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Meng, Bowen; Lee, Ho; Xing, Lei; Fahimian, Benjamin P.
2013-01-01
Purpose: X-ray scatter results in a significant degradation of image quality in computed tomography (CT), representing a major limitation in cone-beam CT (CBCT) and large field-of-view diagnostic scanners. In this work, a novel scatter estimation and correction technique is proposed that utilizes peripheral detection of scatter during the patient scan to simultaneously acquire image and patient-specific scatter information in a single scan, and in conjunction with a proposed compressed sensing scatter recovery technique to reconstruct and correct for the patient-specific scatter in the projection space. Methods: The method consists of the detection of patient scatter at the edges of the field of view (FOV) followed by measurement based compressed sensing recovery of the scatter through-out the projection space. In the prototype implementation, the kV x-ray source of the Varian TrueBeam OBI system was blocked at the edges of the projection FOV, and the image detector in the corresponding blocked region was used for scatter detection. The design enables image data acquisition of the projection data on the unblocked central region of and scatter data at the blocked boundary regions. For the initial scatter estimation on the central FOV, a prior consisting of a hybrid scatter model that combines the scatter interpolation method and scatter convolution model is estimated using the acquired scatter distribution on boundary region. With the hybrid scatter estimation model, compressed sensing optimization is performed to generate the scatter map by penalizing the L1 norm of the discrete cosine transform of scatter signal. The estimated scatter is subtracted from the projection data by soft-tuning, and the scatter-corrected CBCT volume is obtained by the conventional Feldkamp-Davis-Kress algorithm. Experimental studies using image quality and anthropomorphic phantoms on a Varian TrueBeam system were carried out to evaluate the performance of the proposed scheme. Results: The scatter shading artifacts were markedly suppressed in the reconstructed images using the proposed method. On the Catphan©504 phantom, the proposed method reduced the error of CT number to 13 Hounsfield units, 10% of that without scatter correction, and increased the image contrast by a factor of 2 in high-contrast regions. On the anthropomorphic phantom, the spatial nonuniformity decreased from 10.8% to 6.8% after correction. Conclusions: A novel scatter correction method, enabling unobstructed acquisition of the high frequency image data and concurrent detection of the patient-specific low frequency scatter data at the edges of the FOV, is proposed and validated in this work. Relative to blocker based techniques, rather than obstructing the central portion of the FOV which degrades and limits the image reconstruction, compressed sensing is used to solve for the scatter from detection of scatter at the periphery of the FOV, enabling for the highest quality reconstruction in the central region and robust patient-specific scatter correction. PMID:23298098
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-29
... Emirates to Iran of a Varian Ximatron oncology system, which was subject to the Regulations,\\3\\ and the...). Maghazehe had knowledge that a U.S. hospital was discarding the oncology system and that a company in Iran... the oncology system to the Iranian company, Maghazehe worked with a U.S. company to arrange for the de...
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Klystron Manufacturing Technology Program.
1983-09-01
processes, and methodology used on the current production tube, VKU-7735E, and the new methods and techniques used to improve and reduce the cost of...the bellows. This alignment is c~tclto the smoothi operation of the internal tuniing mezhanism. IT METRD - VKCU-7795F The new assembly method changes...Varian, the MT contractor that the new methodology , technologies and process changes introduced into the MT power klystron and autotuner assembly - VKU
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Accurate Measurements of Aircraft Engine Soot Emissions Using a CAPS PMssa Monitor
NASA Astrophysics Data System (ADS)
Onasch, Timothy; Thompson, Kevin; Renbaum-Wolff, Lindsay; Smallwood, Greg; Make-Lye, Richard; Freedman, Andrew
2016-04-01
We present results of aircraft engine soot emissions measurements during the VARIAnT2 campaign using CAPS PMssa monitors. VARIAnT2, an aircraft engine non-volatile particulate matter (nvPM) emissions field campaign, was focused on understanding the variability in nvPM mass measurements using different measurement techniques and accounting for possible nvPM sampling system losses. The CAPS PMssa monitor accurately measures both the optical extinction and scattering (and thus single scattering albedo and absorption) of an extracted sample using the same sample volume for both measurements with a time resolution of 1 second and sensitivity of better than 1 Mm-1. Absorption is obtained by subtracting the scattering signal from the total extinction. Given that the single scattering albedo of the particulates emitted from the aircraft engine measured at both 630 and 660 nm was on the order of 0.1, any inaccuracy in the scattering measurement has little impact on the accuracy of the ddetermined absorption coefficient. The absorption is converted into nvPM mass using a documented Mass Absorption Coefficient (MAC). Results of soot emission indices (mass soot emitted per mass of fuel consumed) for a turbojet engine as a function of engine power will be presented and compared to results obtained using an EC/OC monitor.
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Work, Thierry M.; Aeby, G.S.; Stanton, F.G.; Fenner, D.
2008-01-01
Coral disease surveys in American Samoa and Hawai‘i revealed colonies with a distinct dark discoloration affecting 20–60% of the colony surface (Fig. 1a). In some cases, tissue loss with algal infiltration was present within discolored areas. On microscopy, these lesions had marked overgrowth of the coral skeleton and tissues with septate branching structures that stained positive with Grocott’s Methenamine Silver (fungal hyphae) accompanied by necrosis and fragmentation of coral tissues (Fig. 1b). We have observed this condition grossly and microscopically in Pavona varians, Psammocora nierstraszi, and Montipora sp. in American Samoa and in Pavona maldivensis and P. varians in Hawai‘i. This condition resembles Dark Spots Disease from the Caribbean (Solano et al. 1993) that also shows endolithic hypermycosis (Galloway et al. 2007), suggesting that the association between dark discoloration of corals and overgrowth of endolithic fungi may be common (Western Atlantic, Indo-Pacific). Based on gross and microscopic morphology, tissue atrophy may precede overgrowth of endolithic fungi, but this awaits confirmation through systematic studies that monitor the development of lesions over time (pathogenesis). Using standardized terminology (Work and Aeby 2006) to describe lesions facilitates regional comparisons of coral disease.
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Arce, Pedro; Lagares, Juan Ignacio
2018-01-25
We have verified the GAMOS/Geant4 simulation model of a 6 MV VARIAN Clinac 2100 C/D linear accelerator by the procedure of adjusting the initial beam parameters to fit the percentage depth dose and cross-profile dose experimental data at different depths in a water phantom. Thanks to the use of a wide range of field sizes, from 2 × 2 cm 2 to 40 × 40 cm 2 , a small phantom voxel size and high statistics, fine precision in the determination of the beam parameters has been achieved. This precision has allowed us to make a thorough study of the different physics models and parameters that Geant4 offers. The three Geant4 electromagnetic physics sets of models, i.e. Standard, Livermore and Penelope, have been compared to the experiment, testing the four different models of angular bremsstrahlung distributions as well as the three available multiple-scattering models, and optimizing the most relevant Geant4 electromagnetic physics parameters. Before the fitting, a comprehensive CPU time optimization has been done, using several of the Geant4 efficiency improvement techniques plus a few more developed in GAMOS.
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Morris, J. P.; Thatje, S.; Cottin, D.; Oliphant, A.; Brown, A.; Shillito, B.; Ravaux, J.; Hauton, C.
2015-01-01
Range shifts are of great importance as a response for species facing climate change. In the light of current ocean-surface warming, many studies have focused on the capacity of marine ectotherms to shift their ranges latitudinally. Bathymetric range shifts offer an important alternative, and may be the sole option for species already at high latitudes or those within enclosed seas; yet relevant data are scant. Hydrostatic pressure (HP) and temperature have wide ranging effects on physiology, importantly acting in synergy thermodynamically, and therefore represent key environmental constraints to bathymetric migration. We present data on transcriptional regulation in a shallow-water marine crustacean (Palaemonetes varians) at atmospheric and high HP following 168-h exposures at three temperatures across the organisms’ thermal scope, to establish the potential physiological limit to bathymetric migration by neritic fauna. We observe changes in gene expression indicative of cellular macromolecular damage, disturbances in metabolic pathways and a lack of acclimation after prolonged exposure to high HP. Importantly, these effects are ameliorated (less deleterious) at higher temperatures, and exacerbated at lower temperatures. These data, alongside previously published behavioural and heat-shock analyses, have important implications for our understanding of the potential for climate-driven bathymetric range shifts PMID:26716003
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TH-D-BRB-04: Pinnacle Scripting: Improving Efficiency While Maintaining Safety
DOE Office of Scientific and Technical Information (OSTI.GOV)
Moore, J.
2016-06-15
Scripting capabilities and application programming interfaces (APIs) are becoming commonly available in modern treatment planning systems. These links to the treatment planning system (TPS) allow users to read data from the TPS, and in some cases use TPS functionality and write data back to the TPS. Such tools are powerful extensions, allowing automation of routine clinical tasks and supporting research, particularly research involving repetitive tasks on large patient populations. The data and functionality exposed by scripting/API capabilities is vendor dependent, as are the languages used by script/API engines, such as the Microsoft .NET framework or Python. Scripts deployed in amore » clinical environment must be commissioned and validated like any other software tool. This session will provide an overview of scripting applications and a discussion of best practices, followed by a practical introduction to the scripting capabilities of three commercial treatment planning systems. Learning Objectives: Understand the scripting capabilities available in several treatment planning systems Learn how to get started using scripting capabilities Understand the best practices for safe script deployment in a clinical environment R. Popple, Varian Medical Systems has provided research support unrelated to the topic of this session.R. Cardan, Varian Medical Systems for grant research, product evaluation, and teaching honorarium.« less
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Design of experiments in medical physics: Application to the AAA beam model validation.
Dufreneix, S; Legrand, C; Di Bartolo, C; Bremaud, M; Mesgouez, J; Tiplica, T; Autret, D
2017-09-01
The purpose of this study is to evaluate the usefulness of the design of experiments in the analysis of multiparametric problems related to the quality assurance in radiotherapy. The main motivation is to use this statistical method to optimize the quality assurance processes in the validation of beam models. Considering the Varian Eclipse system, eight parameters with several levels were selected: energy, MLC, depth, X, Y 1 and Y 2 jaw dimensions, wedge and wedge jaw. A Taguchi table was used to define 72 validation tests. Measurements were conducted in water using a CC04 on a TrueBeam STx, a TrueBeam Tx, a Trilogy and a 2300IX accelerator matched by the vendor. Dose was computed using the AAA algorithm. The same raw data was used for all accelerators during the beam modelling. The mean difference between computed and measured doses was 0.1±0.5% for all beams and all accelerators with a maximum difference of 2.4% (under the 3% tolerance level). For all beams, the measured doses were within 0.6% for all accelerators. The energy was found to be an influencing parameter but the deviations observed were smaller than 1% and not considered clinically significant. Designs of experiment can help define the optimal measurement set to validate a beam model. The proposed method can be used to identify the prognostic factors of dose accuracy. The beam models were validated for the 4 accelerators which were found dosimetrically equivalent even though the accelerator characteristics differ. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Brualla, Lorenzo, E-mail: lorenzo.brualla@uni-due.de; Zaragoza, Francisco J.; Sempau, Josep
Purpose: External beam radiotherapy is the only conservative curative approach for Stage I non-Hodgkin lymphomas of the conjunctiva. The target volume is geometrically complex because it includes the eyeball and lid conjunctiva. Furthermore, the target volume is adjacent to radiosensitive structures, including the lens, lacrimal glands, cornea, retina, and papilla. The radiotherapy planning and optimization requires accurate calculation of the dose in these anatomical structures that are much smaller than the structures traditionally considered in radiotherapy. Neither conventional treatment planning systems nor dosimetric measurements can reliably determine the dose distribution in these small irradiated volumes. Methods and Materials: The Montemore » Carlo simulations of a Varian Clinac 2100 C/D and human eye were performed using the PENELOPE and PENEASYLINAC codes. Dose distributions and dose volume histograms were calculated for the bulbar conjunctiva, cornea, lens, retina, papilla, lacrimal gland, and anterior and posterior hemispheres. Results: The simulated results allow choosing the most adequate treatment setup configuration, which is an electron beam energy of 6 MeV with additional bolus and collimation by a cerrobend block with a central cylindrical hole of 3.0 cm diameter and central cylindrical rod of 1.0 cm diameter. Conclusions: Monte Carlo simulation is a useful method to calculate the minute dose distribution in ocular tissue and to optimize the electron irradiation technique in highly critical structures. Using a voxelized eye phantom based on patient computed tomography images, the dose distribution can be estimated with a standard statistical uncertainty of less than 2.4% in 3 min using a computing cluster with 30 cores, which makes this planning technique clinically relevant.« less
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Reliability of fMRI for Studies of Language in Post-Stroke Aphasia Subjects
Eaton, Kenneth P.; Szaflarski, Jerzy P.; Altaye, Mekibib; Ball, Angel L.; Kissela, Brett M.; Banks, Christi; Holland, Scott K.
2008-01-01
Quantifying change in brain activation patterns associated with post-stroke recovery and reorganization of language function over time requires accurate understanding of inter-scan and inter-subject variability. Here we report inter-scan variability measures for fMRI activation patterns associated with verb generation (VG) and semantic decision/tone decision (SDTD) tasks in 4 healthy controls and 4 aphasic left middle cerebral artery (LMCA) stroke subjects. A series of 10 fMRI scans was completed on a 4T Varian scanner for each task for each subject, except for one stroke subject who completed 5 and 6 scans for SDTD and VG, thus yielding 35 and 36 total stroke subject scans for SDTD and VG, respectively. Group composite and intraclass correlation coefficient (ICC) maps were computed across all subjects and trials for each task. The patterns of reliable activation for the VG and SDTD tasks correspond well to those regions typically activated by these tasks in healthy and aphasic subjects. ICCs for activation were consistently high (R0.05 ≈ 0.8) for individual tasks among both control and aphasic subjects. These voxel-wise measures of reliability highlight regions of low inter-scan variability within language circuitry for control and post-recovery stroke subjects. ICCs computed from the combination of the SDTD/VG data were markedly reduced for both control and aphasic subjects as compared with the ICCs for the individual tasks. These quantitative measures of inter-scan variability support the proposed use of these fMRI paradigms for longitudinal mapping of neural reorganization of language processing following left hemispheric insult. PMID:18411061
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Non-Invasive Nanodiagnostics of Cancer (NINOC)
2008-04-01
context. Since the delivery and detection principles are universal, the same nanocarriers can be used with different contrast reporter moieties such...conventional solution-state 1H NMR allowed us only to estimate the changes in the extent of cross-linking upon the synthesis (Figure 9 2). As expected...time of Gd-loaded nanogels was estimated from 1H NMR spectra acquired using a Varian INOVA 500MHz spectrometer and relaxivity (R1) was calculated. In
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Three Dimensional Imaging of Helicon Wave Fields Via Magnetic Induction Probes
2009-07-13
Elastomer Flange 50 The chamber is pumped by a Varian TV-300 HT turbomolecular vacuum pump with a pumping speed of 250 l/s backed by a dry scroll ... vacuum diffusion chamber with pump locations .................................................. 49 Figure 3.2. RF power delivery system...steel, 0.5 meter diameter by 1.0 meter long vacuum chamber. It has 24 access ports / flanges of varying diameter for diagnostic feed-throughs, pumping
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BioTerNet Networking and Strain Tracking
2006-07-01
lactobacillus 74 74 100.0% 0 lechevalieria 16 16 100.0% 0 leclercia 7 5 71.4% 0 legionella 369 337 91.3% 0 leuconostoc 6 5 83.3% 0 listeria 118 93 78.8% 1... Lactobacillus -delbrucki-bulgaricus 166 Streptococcus-porcini 77 Listeria-grayi 167 Streptococcus-salivarius 78 Listeria-innocua 168 Streptococcus-sanguis 79...varians Kribbella 1 1 solani Kytococcus 1 1 schroeteri Lactobacillus 47 29 acidophilus agilis alimentarius amylovorus animalis bifermentans brevis
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NASA Technical Reports Server (NTRS)
1986-01-01
A former NASA employee who discovered a kind of plastic that soaked up energy, dampened vibrations, and was a good noise abatement material, founded a company to market noise deadening adhesives, sheets, panels and enclosures. Known as SMART products, they are 75-80% lighter than ordinary soundproofing material and have demonstrated a high degree of effectiveness. The company, Varian Associates, makes enclosures for high voltage terminals and other electronic system components, and easily transportable audiometric test booths.
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Intraoperative Radiation Therapy: Characterization and Application
1989-03-01
difficult to obtain. Notably, carcinomas of the pancreas, stomach, colon, and rectum, and sarcomas of soft tissue are prime candidates for IORT (2:131...Their pioneering efforts served as the basis for all my work. Mr. John Brohas of the AFIT Model Fabrication Shop aided my efforts considerably by... fabricated to set the collimator jaws to the required 10 cm x 10 cm aperture. The necessary parts are available from Varian. This will help eliminate errors
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Ultra-Low Threshold Vertical-Cavity Surface-Emitting Lasers for USAF Applications
2005-01-01
molecular beam epitaxy , semiconductors, finite element method, modeling and simulation, oxidation furnace 16. SECURITY CLASSIFICATION OF: 19a. NAME OF...Patterson Air Force Base). Device material growth was accomplished by means of molecular beam epitaxy (MBE) using a Varian GENII MBE system owned by the...grown by molecular beam epitaxy on a GaAs substrate. Vertical posts, with square and circular cross sections ranging in size from 5 to 40 microns
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mille, M; Lee, C; Failla, G
Purpose: To use the Attila deterministic solver as a supplement to Monte Carlo for calculating out-of-field organ dose in support of epidemiological studies looking at the risks of second cancers. Supplemental dosimetry tools are needed to speed up dose calculations for studies involving large-scale patient cohorts. Methods: Attila is a multi-group discrete ordinates code which can solve the 3D photon-electron coupled linear Boltzmann radiation transport equation on a finite-element mesh. Dose is computed by multiplying the calculated particle flux in each mesh element by a medium-specific energy deposition cross-section. The out-of-field dosimetry capability of Attila is investigated by comparing averagemore » organ dose to that which is calculated by Monte Carlo simulation. The test scenario consists of a 6 MV external beam treatment of a female patient with a tumor in the left breast. The patient is simulated by a whole-body adult reference female computational phantom. Monte Carlo simulations were performed using MCNP6 and XVMC. Attila can export a tetrahedral mesh for MCNP6, allowing for a direct comparison between the two codes. The Attila and Monte Carlo methods were also compared in terms of calculation speed and complexity of simulation setup. A key perquisite for this work was the modeling of a Varian Clinac 2100 linear accelerator. Results: The solid mesh of the torso part of the adult female phantom for the Attila calculation was prepared using the CAD software SpaceClaim. Preliminary calculations suggest that Attila is a user-friendly software which shows great promise for our intended application. Computational performance is related to the number of tetrahedral elements included in the Attila calculation. Conclusion: Attila is being explored as a supplement to the conventional Monte Carlo radiation transport approach for performing retrospective patient dosimetry. The goal is for the dosimetry to be sufficiently accurate for use in retrospective epidemiological investigations.« less
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SU-E-T-503: IMRT Optimization Using Monte Carlo Dose Engine: The Effect of Statistical Uncertainty.
Tian, Z; Jia, X; Graves, Y; Uribe-Sanchez, A; Jiang, S
2012-06-01
With the development of ultra-fast GPU-based Monte Carlo (MC) dose engine, it becomes clinically realistic to compute the dose-deposition coefficients (DDC) for IMRT optimization using MC simulation. However, it is still time-consuming if we want to compute DDC with small statistical uncertainty. This work studies the effects of the statistical error in DDC matrix on IMRT optimization. The MC-computed DDC matrices are simulated here by adding statistical uncertainties at a desired level to the ones generated with a finite-size pencil beam algorithm. A statistical uncertainty model for MC dose calculation is employed. We adopt a penalty-based quadratic optimization model and gradient descent method to optimize fluence map and then recalculate the corresponding actual dose distribution using the noise-free DDC matrix. The impacts of DDC noise are assessed in terms of the deviation of the resulted dose distributions. We have also used a stochastic perturbation theory to theoretically estimate the statistical errors of dose distributions on a simplified optimization model. A head-and-neck case is used to investigate the perturbation to IMRT plan due to MC's statistical uncertainty. The relative errors of the final dose distributions of the optimized IMRT are found to be much smaller than those in the DDC matrix, which is consistent with our theoretical estimation. When history number is decreased from 108 to 106, the dose-volume-histograms are still very similar to the error-free DVHs while the error in DDC is about 3.8%. The results illustrate that the statistical errors in the DDC matrix have a relatively small effect on IMRT optimization in dose domain. This indicates we can use relatively small number of histories to obtain the DDC matrix with MC simulation within a reasonable amount of time, without considerably compromising the accuracy of the optimized treatment plan. This work is supported by Varian Medical Systems through a Master Research Agreement. © 2012 American Association of Physicists in Medicine.
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Generation of a novel phase-space-based cylindrical dose kernel for IMRT optimization.
Zhong, Hualiang; Chetty, Indrin J
2012-05-01
Improving dose calculation accuracy is crucial in intensity-modulated radiation therapy (IMRT). We have developed a method for generating a phase-space-based dose kernel for IMRT planning of lung cancer patients. Particle transport in the linear accelerator treatment head of a 21EX, 6 MV photon beam (Varian Medical Systems, Palo Alto, CA) was simulated using the EGSnrc/BEAMnrc code system. The phase space information was recorded under the secondary jaws. Each particle in the phase space file was associated with a beamlet whose index was calculated and saved in the particle's LATCH variable. The DOSXYZnrc code was modified to accumulate the energy deposited by each particle based on its beamlet index. Furthermore, the central axis of each beamlet was calculated from the orientation of all the particles in this beamlet. A cylinder was then defined around the central axis so that only the energy deposited within the cylinder was counted. A look-up table was established for each cylinder during the tallying process. The efficiency and accuracy of the cylindrical beamlet energy deposition approach was evaluated using a treatment plan developed on a simulated lung phantom. Profile and percentage depth doses computed in a water phantom for an open, square field size were within 1.5% of measurements. Dose optimized with the cylindrical dose kernel was found to be within 0.6% of that computed with the nontruncated 3D kernel. The cylindrical truncation reduced optimization time by approximately 80%. A method for generating a phase-space-based dose kernel, using a truncated cylinder for scoring dose, in beamlet-based optimization of lung treatment planning was developed and found to be in good agreement with the standard, nontruncated scoring approach. Compared to previous techniques, our method significantly reduces computational time and memory requirements, which may be useful for Monte-Carlo-based 4D IMRT or IMAT treatment planning.
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Parsai, E Ishmael; Zhang, Zhengdong; Feldmeier, John J
2009-01-01
The commercially available brachytherapy treatment-planning systems today, usually neglects the attenuation effect from stainless steel (SS) tube when Fletcher-Suit-Delclos (FSD) is used in treatment of cervical and endometrial cancers. This could lead to potential inaccuracies in computing dwell times and dose distribution. A more accurate analysis quantifying the level of attenuation for high-dose-rate (HDR) iridium 192 radionuclide ((192)Ir) source is presented through Monte Carlo simulation verified by measurement. In this investigation a general Monte Carlo N-Particles (MCNP) transport code was used to construct a typical geometry of FSD through simulation and compare the doses delivered to point A in Manchester System with and without the SS tubing. A quantitative assessment of inaccuracies in delivered dose vs. the computed dose is presented. In addition, this investigation expanded to examine the attenuation-corrected radial and anisotropy dose functions in a form parallel to the updated AAPM Task Group No. 43 Report (AAPM TG-43) formalism. This will delineate quantitatively the inaccuracies in dose distributions in three-dimensional space. The changes in dose deposition and distribution caused by increased attenuation coefficient resulted from presence of SS are quantified using MCNP Monte Carlo simulations in coupled photon/electron transport. The source geometry was that of the Vari Source wire model VS2000. The FSD was that of the Varian medical system. In this model, the bending angles of tandem and colpostats are 15 degrees and 120 degrees , respectively. We assigned 10 dwell positions to the tandem and 4 dwell positions to right and left colpostats or ovoids to represent a typical treatment case. Typical dose delivered to point A was determined according to Manchester dosimetry system. Based on our computations, the reduction of dose to point A was shown to be at least 3%. So this effect presented by SS-FSD systems on patient dose is of concern.
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SU-F-T-306: Validation of Mobius 3D and FX for Elekta Linear Accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Nelson, C; Garcia, M; Calderon, E
2016-06-15
Purpose: Log file based IMRT and VMAT QA is a system that analyzes treatment log files and uses delivery parameters to compute the dose to the patient/phantom. This system was previously commissioned for Varian machines, the purpose of this work is to describe the process for commissioning Mobius for use with Elekta machines. Methods: Twelve IMRT and VMAT plans (6×) were planned and delivered and dose was measured using MapCheck, the results were compared to that computed by Mobius. For 10x and 18x, plans were generated, copied to a phantom and delivered, the dose was measured using a single ionmore » chamber. The difference in measured dose to computed dose (Mobius) was used to adjust the dynamic leaf gap (DLG) in Mobius to achieve optimal agreement between measurements, Mobius and treatment plans. Results: For the measured dose comparison, the average 3%/3mm gamma 97.1% of pixels passed criteria using MapCheck where Mobius computed 96.9% of voxels passing. For 10×, a DLG of −5.5 was determined to achieve optimal results for TPS and measured ion chamber data with an average 0.1% difference and −1.7% respectively. For 18×, a DLG of −3 was determined to achieve optimal results from the TPS and measured data with an average of −0.7% and −1.4% difference on average from a set of IMRT and VMAT plans. The 6x data needed no DLG correction to arrive at agreement with the TPS and the MapCheck measured data. Conclusion: We have validated with measurements for IMRT and VMAT cases the use of Mobius FX with Elekta treatment machines for IMRT and VMAT QA. For 6×, no adjustments to the DLG were required to obtain good results utilizing Mobius whereas for 10× and 18×, the DLG had to be adjusted to obtain optimum agreement with measured data and our TPS.« less
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NASA Astrophysics Data System (ADS)
Baptista, M.; Di Maria, S.; Vieira, S.; Vaz, P.
2017-11-01
Cone-Beam Computed Tomography (CBCT) enables high-resolution volumetric scanning of the bone and soft tissue anatomy under investigation at the treatment accelerator. This technique is extensively used in Image Guided Radiation Therapy (IGRT) for pre-treatment verification of patient position and target volume localization. When employed daily and several times per patient, CBCT imaging may lead to high cumulative imaging doses to the healthy tissues surrounding the exposed organs. This work aims at (1) evaluating the dose distribution during a CBCT scan and (2) calculating the organ doses involved in this image guiding procedure for clinically available scanning protocols. Both Monte Carlo (MC) simulations and measurements were performed. To model and simulate the kV imaging system mounted on a linear accelerator (Edge™, Varian Medical Systems) the state-of-the-art MC radiation transport program MCNPX 2.7.0 was used. In order to validate the simulation results, measurements of the Computed Tomography Dose Index (CTDI) were performed, using standard PMMA head and body phantoms, with 150 mm length and a standard pencil ionizing chamber (IC) 100 mm long. Measurements for head and pelvis scanning protocols, usually adopted in clinical environment were acquired, using two acquisition modes (full-fan and half fan). To calculate the organ doses, the implemented MC model of the CBCT scanner together with a male voxel phantom ("Golem") was used. The good agreement between the MCNPX simulations and the CTDIw measurements (differences up to 17%) presented in this work reveals that the CBCT MC model was successfully validated, taking into account the several uncertainties. The adequacy of the computational model to map dose distributions during a CBCT scan is discussed in order to identify ways to reduce the total CBCT imaging dose. The organ dose assessment highlights the need to evaluate the therapeutic and the CBCT imaging doses, in a more balanced approach, and the importance of improving awareness regarding the increased risk, arising from repeated exposures.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, S; Wu, Y; Chang, X
Purpose: A novel computer software system, namely APDV (Automatic Pre-Delivery Verification), has been developed for verifying patient treatment plan parameters right prior to treatment deliveries in order to automatically detect and prevent catastrophic errors. Methods: APDV is designed to continuously monitor new DICOM plan files on the TMS computer at the treatment console. When new plans to be delivered are detected, APDV checks the consistencies of plan parameters and high-level plan statistics using underlying rules and statistical properties based on given treatment site, technique and modality. These rules were quantitatively derived by retrospectively analyzing all the EBRT treatment plans ofmore » the past 8 years at authors’ institution. Therapists and physicists will be notified with a warning message displayed on the TMS computer if any critical errors are detected, and check results, confirmation, together with dismissal actions will be saved into database for further review. Results: APDV was implemented as a stand-alone program using C# to ensure required real time performance. Mean values and standard deviations were quantitatively derived for various plan parameters including MLC usage, MU/cGy radio, beam SSD, beam weighting, and the beam gantry angles (only for lateral targets) per treatment site, technique and modality. 2D-based rules of combined MU/cGy ratio and averaged SSD values were also derived using joint probabilities of confidence error ellipses. The statistics of these major treatment plan parameters quantitatively evaluate the consistency of any treatment plans which facilitates automatic APDV checking procedures. Conclusion: APDV could be useful in detecting and preventing catastrophic errors immediately before treatment deliveries. Future plan including automatic patient identify and patient setup checks after patient daily images are acquired by the machine and become available on the TMS computer. This project is supported by the Agency for Healthcare Research and Quality (AHRQ) under award 1R01HS0222888. The senior author received research grants from ViewRay Inc. and Varian Medical System.« less
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SU-F-T-480: Evaluation of the Role of Varian Machine Performance Check (MPC) in Our Daily QA Routine
DOE Office of Scientific and Technical Information (OSTI.GOV)
Juneja, B; Gao, S; Balter, P
2016-06-15
Purpose: (A) To assess the role of Varian MPC in our daily QA routine, and (B) evaluate the accuracy and precision of MPC. Methods: The MPC was performed weekly, for five months, on a Varian TrueBeam for five photon (6x, 10x, 15x, 6xFFF, and 10xFFF) and electron (6e, 9e, 12e, 16e, and 20e) energies. Output results were compared to those determined with an ionization chamber (TN30001, PTW-Freiburg) in plastic and a daily check device (DQA3, Sun Nuclear). Consistency of the Mechanical measurements over five months was analyzed and compared to monthly IsoCal results. Results: The MPC randomly showed large deviationsmore » (3–7%) that disappeared upon reacquisition. The MPC output closely matched monthly ion chamber and DQA3 measurements. The maximum and mean absolute difference between monthly and MPC was 1.18% and 0.28±0.21% for all energies. The maximum and mean absolute difference between DQA3 and MPC was 3.26% and 0.85±0.61%. The results suggest the MPC is comparable to the DQA3 for measuring output. The DQA3 provides wedge output, flatness, symmetry, and energy constancy checks, which are missing from the current implementation of the MPC. However, the MPC provides additional mechanical tests, such as size of the radiation isocenter (0.33±0.02 mm) and its coincidence with MV and kV isocenters (0.17±0.05 and 0.21±0.03 mm). It also provides positional accuracy of individual jaws (maximum σ, 0.33mm), all the MLC leaves (0.08mm), gantry (0.05°) and collimator (0.13°) rotation angles, and couch positioning (0.11mm) accuracy. MPC mechanical tests could replace our current daily on-board imaging QA routine and provide some additional QA not currently performed. Conclusion: MPC has the potential to be a valuable tool that facilitates reliable daily QA including many mechanical tests that are not currently performed. This system can add to our daily QA, but further development would be needed to fully replace our current Daily QA device.« less
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TH-A-18C-10: Dynamic Intensity Weighted Region of Interest Imaging
DOE Office of Scientific and Technical Information (OSTI.GOV)
Pearson, E; Pan, X; Pelizzari, C
2014-06-15
Purpose: For image guidance tasks full image quality is not required throughout the entire image. With dynamic filtration of the kV imaging beam the noise properties of the CT image can be locally controlled, providing a high quality image around the target volume with a lower quality surrounding region while providing substantial dose sparing to the patient as well as reduced scatter fluence on the detector. Methods: A dynamic collimation device with 3mm copper blades has been designed to mount in place of the bowtie filter on the On-Board Imager (Varian Medical Systems). The beam intensity is reduced by 95%more » behind the copper filters and the aperture is controlled dynamically to conformally illuminate a given ROI during a standard cone-beam CT scan. A data correction framework to account for the physical effects of the collimator prior to reconstruction was developed. Furthermore, to determine the dose savings and scatter reduction a monte carlo model was built in BEAMnrc with specifics from the Varian Monte Carlo Data Package. The MC model was validated with Gafchromic film. Results: The reconstructed image shows image quality comparable to a standard scan in the specified ROI, with higher noise and streaks in the outer region but still sufficient information for alignment to high contrast structures. The monte carlo modeling showed that the scatter-to-primary ratio was reduced from 1.26 for an unfiltered scan to 0.45 for an intensity weighted scan, suggesting that image quality may be improved in the inner ROI. Dose in the inner region was reduced 10–15% due to reduced scatter and by as much as 75% in the outer region. Conclusion: Dynamic intensity-weighted ROI imaging allows reduction of imaging dose to sensitive organs away from the target region while providing images that retain their utility for patient setup and procedure guidance. Funding was provided in part by Varian Medical Systems and NIH Grants 1RO1CA120540, T32EB002103, S10 RR021039 and P30 CA14599. The contents of this work are solely the responsibility of the authors and do not necessarily represent the official views of any of the supporting organizations.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wang, L; Ding, G
Purpose: Dose calculation accuracy for the out-of-field dose is important for predicting the dose to the organs-at-risk when they are located outside primary beams. The investigations on evaluating the calculation accuracy of treatment planning systems (TPS) on out-of-field dose in existing publications have focused on low energy (6MV) photon. This study evaluates out-of-field dose calculation accuracy of AAA algorithm for 15MV high energy photon beams. Methods: We used the EGSnrc Monte Carlo (MC) codes to evaluate the AAA algorithm in Varian Eclipse TPS (v.11). The incident beams start with validated Varian phase-space sources for a TrueBeam linac equipped with Millenniummore » 120 MLC. Dose comparisons between using AAA and MC for CT based realistic patient treatment plans using VMAT techniques for prostate and lung were performed and uncertainties of organ dose predicted by AAA at out-of-field location were evaluated. Results: The results show that AAA calculations under-estimate doses at the dose level of 1% (or less) of prescribed dose for CT based patient treatment plans using VMAT techniques. In regions where dose is only 1% of prescribed dose, although AAA under-estimates the out-of-field dose by 30% relative to the local dose, it is only about 0.3% of prescribed dose. For example, the uncertainties of calculated organ dose to liver or kidney that is located out-of-field is <0.3% of prescribed dose. Conclusion: For 15MV high energy photon beams, very good agreements (<1%) in calculating dose distributions were obtained between AAA and MC. The uncertainty of out-of-field dose calculations predicted by the AAA algorithm for realistic patient VMAT plans is <0.3% of prescribed dose in regions where the dose relative to the prescribed dose is <1%, although the uncertainties can be much larger relative to local doses. For organs-at-risk located at out-of-field, the error of dose predicted by Eclipse using AAA is negligible. This work was conducted in part using the resources of Varian research grant VUMC40590-R.« less
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Commissioning of a Varian Clinac iX 6 MV photon beam using Monte Carlo simulation
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dirgayussa, I Gde Eka, E-mail: ekadirgayussa@gmail.com; Yani, Sitti; Haryanto, Freddy, E-mail: freddy@fi.itb.ac.id
2015-09-30
Monte Carlo modelling of a linear accelerator is the first and most important step in Monte Carlo dose calculations in radiotherapy. Monte Carlo is considered today to be the most accurate and detailed calculation method in different fields of medical physics. In this research, we developed a photon beam model for Varian Clinac iX 6 MV equipped with MilleniumMLC120 for dose calculation purposes using BEAMnrc/DOSXYZnrc Monte Carlo system based on the underlying EGSnrc particle transport code. Monte Carlo simulation for this commissioning head LINAC divided in two stages are design head Linac model using BEAMnrc, characterize this model using BEAMDPmore » and analyze the difference between simulation and measurement data using DOSXYZnrc. In the first step, to reduce simulation time, a virtual treatment head LINAC was built in two parts (patient-dependent component and patient-independent component). The incident electron energy varied 6.1 MeV, 6.2 MeV and 6.3 MeV, 6.4 MeV, and 6.6 MeV and the FWHM (full width at half maximum) of source is 1 mm. Phase-space file from the virtual model characterized using BEAMDP. The results of MC calculations using DOSXYZnrc in water phantom are percent depth doses (PDDs) and beam profiles at depths 10 cm were compared with measurements. This process has been completed if the dose difference of measured and calculated relative depth-dose data along the central-axis and dose profile at depths 10 cm is ≤ 5%. The effect of beam width on percentage depth doses and beam profiles was studied. Results of the virtual model were in close agreement with measurements in incident energy electron 6.4 MeV. Our results showed that photon beam width could be tuned using large field beam profile at the depth of maximum dose. The Monte Carlo model developed in this study accurately represents the Varian Clinac iX with millennium MLC 120 leaf and can be used for reliable patient dose calculations. In this commissioning process, the good criteria of dose difference in PDD and dose profiles were achieve using incident electron energy 6.4 MeV.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhang, Q; Driewer, J; Wang, S
Purpose The accuracy of Varian PerfectPitch six degree of freedom (DOF) robotic couch was examined using Varian Isocal phantom and cone-beam CT (CBCT) system. Methods CBCT images of the Isocal phantom were taken at different pitch and roll angles. The pitch and roll angles were varied from 357 to 3 degrees in one degree increments by input from service console, generating a total of 49 combinations with couch angle (yaw) zero. The center positions of the 16 tungsten carbide BBs contained in the Isocal were determined with in-house image processing software. Expected BBs positions at different rotation angles were determinedmore » mathematically by applying a combined translation/rotation operator to BB positions at zero pitch and roll values. A least square method was used to minimize the difference between the expected BB positions and their measured positions. In this way rotation angles were obtained and compared with input values from the console. Results A total of 49 CBCT images with voxel sizes 0.51 mm × 0.51 mm × 1 mm were used in analysis. Among the 49 calculations, the maximum rotation angle differences were 0.1 degree, 0.15 degree, and 0.09 degree, for pitch, roll, and couch rotation, respectively. The mean ± standard-deviation angle differences were 0.028±0.001 degree, −0.043±0.003 degree, and −0.009±0.001 degree, for pitch, roll, and couch rotation, respectively. The maximum isocenter shifts were 0.3 mm, 0.5 mm, 0.4 mm in x, y, z direction respectively following IEC6127 convention. The mean isocenter shifts were 0.07±0.02 mm, −0.05±0.06 mm, and −0.12±0.02 mm in x, y and z directions. Conclusion The accuracy of the Varian PerfectPitch six DOF couch was studied with CBCTs of the Isocal phantom. The rotational errors were less than 0.15 degree and isocenter shifts were less than 0.5 mm in any direction. This accuracy is sufficient for stereotactic radiotherapy clinical applications.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mooney, K; Yaddanapudi, S; Mutic, S
2015-06-15
Purpose: To identify the beam profile parameters that can be used to detect energy changes in a flattening filter-free photon beams. Methods: Flattening filter-free beam profiles (inline, crossline, and diagonals) were measured for multiple field sizes (25×25cm and 10×10cm) at 6MV on a clinical system (Truebeam, Varian Medical Systems Palo Alto CA). Profiles were acquired for baseline energy and detuned beams by changing the bending magnet current (BMC), above and below baseline. The following profile parameters were measured: flatness (off-axis ratio at 80% of field size), symmetry, uniformity, slope, and the off-axis ratio (OAR) at several off-axis distances. Tolerance valuesmore » were determined from repeated measurements. Each parameter was evaluated for sensitivity to the induced beam changes, and the minimum detectable BMC change was calculated for each parameter by calculating the change in BMC that would Result in a change in the parameter above the measurement tolerance. Results: Tolerance values for the parameters were-Flatness≤0.1%; Symmetry≤0.4%; Uniformity≤0.01%; Slope≤ 0.001%/mm. The measurements made with a field size of 25cm and a depth of d=1.5cm showed the greatest sensitivity to bending magnet current variations. Uniformity had the highest sensitivity, able to detect a change in BMC of BMC=0.02A. The OARs and slope were sensitive to the magnitude and direction of BMC change. The sensitivity in the flatness parameter was BMC=0.04A; slope was sensitive to BMC=0.05A. The sensitivity decreased for OARs measured closer to central axis-BMC(8cm)=0.23A; BMC(5cm)=0.47A; BMC(2cm)=1.35A. Symmetry was not sensitive to changes in BMC. Conclusion: These tests allow for better QA of FFF beams by setting tolerance levels to beam parameter baseline values which reflect variations in machine calibration. Uniformity is most sensitive to BMC changes, while OARs provide information about magnitude and direction of miscalibration. Research funding provided by Varian Medical Systems. Dr. Sasa Mutic receives compensation for providing patient safety training services from Varian Medical Systems, the sponsor of this study.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhang, JY; Hong, DL
Purpose: The purpose of this study is to investigate the patient set-up error and interfraction target coverage in cervical cancer using image-guided adaptive radiotherapy (IGART) with cone-beam computed tomography (CBCT). Methods: Twenty cervical cancer patients undergoing intensity modulated radiotherapy (IMRT) were randomly selected. All patients were matched to the isocenter using laser with the skin markers. Three dimensional CBCT projections were acquired by the Varian Truebeam treatment system. Set-up errors were evaluated by radiation oncologists, after CBCT correction. The clinical target volume (CTV) was delineated on each CBCT, and the planning target volume (PTV) coverage of each CBCT-CTVs was analyzed.more » Results: A total of 152 CBCT scans were acquired from twenty cervical cancer patients, the mean set-up errors in the longitudinal, vertical, and lateral direction were 3.57, 2.74 and 2.5mm respectively, without CBCT corrections. After corrections, these were decreased to 1.83, 1.44 and 0.97mm. For the target coverage, CBCT-CTV coverage without CBCT correction was 94% (143/152), and 98% (149/152) with correction. Conclusion: Use of CBCT verfication to measure patient setup errors could be applied to improve the treatment accuracy. In addition, the set-up error corrections significantly improve the CTV coverage for cervical cancer patients.« less
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Breast Tumor Detection and Treatment Using Tarvacin Labeled with Arsenic Radionuclides
2007-04-01
have also purchased and tested isotopically enriched 76GeO2. Materials and Methods. All reagents and solvents were purchased from Sigma-Aldrich...and dimethylsulfoxide were purchased from Pierce (Rockford, IL). BOND ELUT ENV cartridges with a sorbent mass of 25 mg were purchased from Varian...two days prior to the above target processing. Briefly, 2.0 mg of SATA (N-Succinimidyl S- Acetylthioacetate) was dissolved in 500 μL of DMSO , giving a
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Clinical Significance and Mechanistic Insights into Ovarian Cancer Mitochondrial Dysfunction
2017-05-01
during the reporting period. If there is nothing to report under a particular item, state “Nothing to Report.” • Publications, conference papers , and...yes Books or other non-periodical, one-time publications. Nothing to Report Other publications, conference papers , and presentations...scites w ere obtained from stage III-IV ovarian cancer patients (S U N Y / P enn S tate H ershey IR B approved study). O varian cancer cells w ere
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Poster - Thur Eve - 10: Long term stability of VMAT quality assurance parameters using an EPID.
Pekar, J; Diamond, K R
2012-07-01
The rapidly growing use of volumetric modulated arc therapy (VMAT) treatments in radiation therapy calls for a quantitative, automated, and reliable quality assurance (QA) procedure that can be used routinely in the clinical setting. In this work, we present a series VMAT QA procedures used to assess dynamic multi-leaf collimator (MLC) positional accuracy, variable dose-rate accuracy, and MLC leaf speed accuracy. The QA procedures were performed using amorphous silicon electronic portal imaging devices (EPID) to determine the long term stability of the measured parameters on two Varian linear accelerators. The measurements were repeated weekly on both linear accelerators for a period of three months and the EPID images were analyzed using custom Matlab software. The results of the picket fence tests indicate that MLC leaf positions can be identified to within 0.11 mm and 0.15 mm for static gantry delivery and VMAT delivery respectively. In addition, the dose-rate, gantry speed and MLC leaf speed tests both show very good stability over the measurement period. The measurements thus far, suggest that a number of the dosimetry tests may be suitable for quarterly QA for Varian iX and Trilogy linacs. However, additional measurements are required to confirm the frequency with which each test is required for safe and reliable VMAT delivery at our centre. © 2012 American Association of Physicists in Medicine.
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Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array
Yoganathan, S. A.; Das, K. J. Maria; Raj, D. Gowtham; Kumar, Shaleen
2015-01-01
The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams. PMID:26170552
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Öğretici, Akın, E-mail: akinogretici@gmail.com; Akbaş, Uğur; Köksal, Canan
The aim of this research was to investigate the fetal doses of pregnant patients undergoing conformal radiotherapy or intensity-modulated radiation therapy (IMRT) for breast cancers. An Alderson Rando phantom was chosen to simulate a pregnant patient with breast cancer who is receiving radiation therapy. This phantom was irradiated using the Varian Clinac DBX 600 system (Varian Medical System, Palo Alto, CA) linear accelerator, according to the standard treatment plans of both three-dimensional conformal radiation therapy (3-D CRT) and IMRT techniques. Thermoluminescent dosimeters were used to measure the irradiated phantom's virtually designated uterus area. Thermoluminescent dosimeter measurements (in the phantom) revealedmore » that the mean cumulative fetal dose for 3-D CRT is 1.39 cGy and for IMRT it is 8.48 cGy, for a pregnant breast cancer woman who received radiation treatment of 50 Gy. The fetal dose was confirmed to increase by 70% for 3-D CRT and 40% for IMRT, if it is closer to the irradiated field by 5 cm. The mean fetal dose from 3-D CRT is 1.39 cGy and IMRT is 8.48 cGy, consistent with theoretic calculations. The IMRT technique causes the fetal dose to be 5 times more than that of 3-D CRT. Theoretic knowledge concerning the increase in the peripheral doses as the measurements approached the beam was also practically proven.« less
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Comparison of four commercial devices for RapidArc and sliding window IMRT QA
Chandraraj, Varatharaj; Manickam, Ravikumar; Esquivel, Carlos; Supe, Sanjay S.; Papanikolaou, Nikos
2011-01-01
For intensity‐modulated radiation therapy, evaluation of the measured dose against the treatment planning calculated dose is essential in the context of patient‐specific quality assurance. The complexity of volumetric arc radiotherapy delivery attributed to its dynamic and synchronization nature require new methods and potentially new tools for the quality assurance of such techniques. In the present study, we evaluated and compared the dosimetric performance of EDR2 film and three other commercially available quality assurance devices: IBA I'MatriXX array, PTW Seven29 array and the Delta 4 array. The evaluation of these dosimetric systems was performed for RapidArc and IMRT deliveries using a Varian NovalisTX linear accelerator. The plans were generated using the Varian Eclipse treatment planning system. Our results showed that all four QA techniques yield equivalent results. All patient QAs passed our institutional clinical criteria of gamma index based on a 3% dose difference and 3 mm distance to agreement. In addition, the Bland‐Altman analysis was performed which showed that all the calculated gamma values of all three QA devices were within 5% from those of the film. The results showed that the four QA systems used in this patient‐specific IMRT QA analysis are equivalent. We concluded that the dosimetric systems under investigation can be used interchangeably for routine patient specific QA. PACS numbers: 87.55.Qr, 87.56.Fc
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NASA Astrophysics Data System (ADS)
de Arrizabalaga y Prado, L.; de La Fuente Marcos, R.
2005-03-01
Ancient historians refer to a temple in Rome, dedicated to the Syrian sun god Elagabal, by his high priest, the Roman emperor called Varius (204-222AD, commonly called Elagabalus or Heliogabalus). On the basis of their texts, it has been thought that Varius either built a new temple, or rededicated an existing one, expropriated from some other deity, in order to house his god's principal cult object: a large black meteorite, or baetyl, which Varius brought from its temple at Emesa, in Syria, to Rome. In this paper we analyze the hypothesis that the site of the Varian Temple of Elagabal may have been that now known as the Vigna Barberini. A stratigraphic analysis shows that the Vigna Barberini is an artificial platform, built on the rubble of earlier hillside structures, dating from prehistoric times to the Julio-Claudian period. The platform, with more or less its present shape, is of Flavian date, and at that time contained a portico surrounding a central garden. On top of these, a Severan level corresponds to the base of the foundations of a temple that are very solid and go very deep. The azimuth of the temple wall oriented south-east is about 113°. Using a computer program, we have thoroughly scan ned the night sky in AD 1-250, looking for celestial objects that may have been worshipped in the temple. After taking into account the effects of precession, the main candidate for a celestial body worshipped from this site appears to be the star Sirius. In several Mediterranean cultures, the heliacal ortus, or earliest pre-dawn sighting of Sirius (when Sirius again rises into visibility after being hidden by the Sun's light for about 70 days) was thought to have astrological significance. We have compiled the relevant astronomical data for the heliacal ortus of Sirius in the time span 0-250 AD. During that period of time, it falls between 18th and 20th July. The azimuth angle of Sirius, when rising on the heliacal ortus day ci rca 150 AD, is about 111°. Being realistic and taking into consideration the topographical conditions surrounding the location of the temple our analysis suggests that the alignment is too accurate (113° vs. 111°) to be mere coincidence, and that the platform was very probably erected before Varius reign. Based on the astronomical modeling evidence, it appears very likely that the foundations of the temple where erected following the heliacal ortus of Sirius.
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Computer-aided analysis of star shot films for high-accuracy radiation therapy treatment units
NASA Astrophysics Data System (ADS)
Depuydt, Tom; Penne, Rudi; Verellen, Dirk; Hrbacek, Jan; Lang, Stephanie; Leysen, Katrien; Vandevondel, Iwein; Poels, Kenneth; Reynders, Truus; Gevaert, Thierry; Duchateau, Michael; Tournel, Koen; Boussaer, Marlies; Cosentino, Dorian; Garibaldi, Cristina; Solberg, Timothy; De Ridder, Mark
2012-05-01
As mechanical stability of radiation therapy treatment devices has gone beyond sub-millimeter levels, there is a rising demand for simple yet highly accurate measurement techniques to support the routine quality control of these devices. A combination of using high-resolution radiosensitive film and computer-aided analysis could provide an answer. One generally known technique is the acquisition of star shot films to determine the mechanical stability of rotations of gantries and the therapeutic beam. With computer-aided analysis, mechanical performance can be quantified as a radiation isocenter radius size. In this work, computer-aided analysis of star shot film is further refined by applying an analytical solution for the smallest intersecting circle problem, in contrast to the gradient optimization approaches used until today. An algorithm is presented and subjected to a performance test using two different types of radiosensitive film, the Kodak EDR2 radiographic film and the ISP EBT2 radiochromic film. Artificial star shots with a priori known radiation isocenter size are used to determine the systematic errors introduced by the digitization of the film and the computer analysis. The estimated uncertainty on the isocenter size measurement with the presented technique was 0.04 mm (2σ) and 0.06 mm (2σ) for radiographic and radiochromic films, respectively. As an application of the technique, a study was conducted to compare the mechanical stability of O-ring gantry systems with C-arm-based gantries. In total ten systems of five different institutions were included in this study and star shots were acquired for gantry, collimator, ring, couch rotations and gantry wobble. It was not possible to draw general conclusions about differences in mechanical performance between O-ring and C-arm gantry systems, mainly due to differences in the beam-MLC alignment procedure accuracy. Nevertheless, the best performing O-ring system in this study, a BrainLab/MHI Vero system, and the best performing C-arm system, a Varian Truebeam system, showed comparable mechanical performance: gantry isocenter radius of 0.12 and 0.09 mm, respectively, ring/couch rotation of below 0.10 mm for both systems and a wobble of 0.06 and 0.18 mm, respectively. The methodology described in this work can be used to monitor mechanical performance constancy of high-accuracy treatment devices, with means available in a clinical radiation therapy environment.
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Glaser, Adam K; Andreozzi, Jacqueline M; Zhang, Rongxiao; Pogue, Brian W; Gladstone, David J
2015-07-01
To test the use of a three-dimensional (3D) optical cone beam computed tomography reconstruction algorithm, for estimation of the imparted 3D dose distribution from megavoltage photon beams in a water tank for quality assurance, by imaging the induced Cherenkov-excited fluorescence (CEF). An intensified charge-coupled device coupled to a standard nontelecentric camera lens was used to tomographically acquire two-dimensional (2D) projection images of CEF from a complex multileaf collimator (MLC) shaped 6 MV linear accelerator x-ray photon beam operating at a dose rate of 600 MU/min. The resulting projections were used to reconstruct the 3D CEF light distribution, a potential surrogate of imparted dose, using a Feldkamp-Davis-Kress cone beam back reconstruction algorithm. Finally, the reconstructed light distributions were compared to the expected dose values from one-dimensional diode scans, 2D film measurements, and the 3D distribution generated from the clinical Varian ECLIPSE treatment planning system using a gamma index analysis. A Monte Carlo derived correction was applied to the Cherenkov reconstructions to account for beam hardening artifacts. 3D light volumes were successfully reconstructed over a 400 × 400 × 350 mm(3) volume at a resolution of 1 mm. The Cherenkov reconstructions showed agreement with all comparative methods and were also able to recover both inter- and intra-MLC leaf leakage. Based upon a 3%/3 mm criterion, the experimental Cherenkov light measurements showed an 83%-99% pass fraction depending on the chosen threshold dose. The results from this study demonstrate the use of optical cone beam computed tomography using CEF for the profiling of the imparted dose distribution from large area megavoltage photon beams in water.
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Motion vector field phase-to-amplitude resampling for 4D motion-compensated cone-beam CT
NASA Astrophysics Data System (ADS)
Sauppe, Sebastian; Kuhm, Julian; Brehm, Marcus; Paysan, Pascal; Seghers, Dieter; Kachelrieß, Marc
2018-02-01
We propose a phase-to-amplitude resampling (PTAR) method to reduce motion blurring in motion-compensated (MoCo) 4D cone-beam CT (CBCT) image reconstruction, without increasing the computational complexity of the motion vector field (MVF) estimation approach. PTAR is able to improve the image quality in reconstructed 4D volumes, including both regular and irregular respiration patterns. The PTAR approach starts with a robust phase-gating procedure for the initial MVF estimation and then switches to a phase-adapted amplitude gating method. The switch implies an MVF-resampling, which makes them amplitude-specific. PTAR ensures that the MVFs, which have been estimated on phase-gated reconstructions, are still valid for all amplitude-gated reconstructions. To validate the method, we use an artificially deformed clinical CT scan with a realistic breathing pattern and several patient data sets acquired with a TrueBeamTM integrated imaging system (Varian Medical Systems, Palo Alto, CA, USA). Motion blurring, which still occurs around the area of the diaphragm or at small vessels above the diaphragm in artifact-specific cyclic motion compensation (acMoCo) images based on phase-gating, is significantly reduced by PTAR. Also, small lung structures appear sharper in the images. This is demonstrated both for simulated and real patient data. A quantification of the sharpness of the diaphragm confirms these findings. PTAR improves the image quality of 4D MoCo reconstructions compared to conventional phase-gated MoCo images, in particular for irregular breathing patterns. Thus, PTAR increases the robustness of MoCo reconstructions for CBCT. Because PTAR does not require any additional steps for the MVF estimation, it is computationally efficient. Our method is not restricted to CBCT but could rather be applied to other image modalities.
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The use of computed radiography plates to determine light and radiation field coincidence.
Kerns, James R; Anand, Aman
2013-11-01
Photo-stimulable phosphor computed radiography (CR) has characteristics that allow the output to be manipulated by both radiation and optical light. The authors have developed a method that uses these characteristics to carry out radiation field and light field coincidence quality assurance on linear accelerators. CR detectors from Kodak were used outside their cassettes to measure both radiation and light field edges from a Varian linear accelerator. The CR detector was first exposed to a radiation field and then to a slightly smaller light field. The light impinged on the detector's latent image, removing to an extent the portion exposed to the light field. The detector was then digitally scanned. A MATLAB-based algorithm was developed to automatically analyze the images and determine the edges of the light and radiation fields, the vector between the field centers, and the crosshair center. Radiographic film was also used as a control to confirm the radiation field size. Analysis showed a high degree of repeatability with the proposed method. Results between the proposed method and radiographic film showed excellent agreement of the radiation field. The effect of varying monitor units and light exposure time was tested and found to be very small. Radiation and light field sizes were determined with an uncertainty of less than 1 mm, and light and crosshair centers were determined within 0.1 mm. A new method was developed to digitally determine the radiation and light field size using CR photo-stimulable phosphor plates. The method is quick and reproducible, allowing for the streamlined and robust assessment of light and radiation field coincidence, with no observer interpretation needed.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mukherjee, S; Yao, W
2015-06-15
Purpose: To study different noise-reduction algorithms and to improve the image quality of low dose cone beam CT for patient positioning in radiation therapy. Methods: In low-dose cone-beam CT, the reconstructed image is contaminated with excessive quantum noise. In this study, three well-developed noise reduction algorithms namely, a) penalized weighted least square (PWLS) method, b) split-Bregman total variation (TV) method, and c) compressed sensing (CS) method were studied and applied to the images of a computer–simulated “Shepp-Logan” phantom and a physical CATPHAN phantom. Up to 20% additive Gaussian noise was added to the Shepp-Logan phantom. The CATPHAN phantom was scannedmore » by a Varian OBI system with 100 kVp, 4 ms and 20 mA. For comparing the performance of these algorithms, peak signal-to-noise ratio (PSNR) of the denoised images was computed. Results: The algorithms were shown to have the potential in reducing the noise level for low-dose CBCT images. For Shepp-Logan phantom, an improvement of PSNR of 2 dB, 3.1 dB and 4 dB was observed using PWLS, TV and CS respectively, while for CATPHAN, the improvement was 1.2 dB, 1.8 dB and 2.1 dB, respectively. Conclusion: Penalized weighted least square, total variation and compressed sensing methods were studied and compared for reducing the noise on a simulated phantom and a physical phantom scanned by low-dose CBCT. The techniques have shown promising results for noise reduction in terms of PSNR improvement. However, reducing the noise without compromising the smoothness and resolution of the image needs more extensive research.« less
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NASA Astrophysics Data System (ADS)
Montanari, Davide; Scolari, Enrica; Silvestri, Chiara; Jiang Graves, Yan; Yan, Hao; Cervino, Laura; Rice, Roger; Jiang, Steve B.; Jia, Xun
2014-03-01
Cone beam CT (CBCT) has been widely used for patient setup in image-guided radiation therapy (IGRT). Radiation dose from CBCT scans has become a clinical concern. The purposes of this study are (1) to commission a graphics processing unit (GPU)-based Monte Carlo (MC) dose calculation package gCTD for Varian On-Board Imaging (OBI) system and test the calculation accuracy, and (2) to quantitatively evaluate CBCT dose from the OBI system in typical IGRT scan protocols. We first conducted dose measurements in a water phantom. X-ray source model parameters used in gCTD are obtained through a commissioning process. gCTD accuracy is demonstrated by comparing calculations with measurements in water and in CTDI phantoms. Twenty-five brain cancer patients are used to study dose in a standard-dose head protocol, and 25 prostate cancer patients are used to study dose in pelvis protocol and pelvis spotlight protocol. Mean dose to each organ is calculated. Mean dose to 2% voxels that have the highest dose is also computed to quantify the maximum dose. It is found that the mean dose value to an organ varies largely among patients. Moreover, dose distribution is highly non-homogeneous inside an organ. The maximum dose is found to be 1-3 times higher than the mean dose depending on the organ, and is up to eight times higher for the entire body due to the very high dose region in bony structures. High computational efficiency has also been observed in our studies, such that MC dose calculation time is less than 5 min for a typical case.
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Jin, Lihui; Price, Robert A; Wang, Lu; Meyer, Joshua; Fan, James Jiajin; Ma, Chang Ming Charlie
2016-02-01
The CyberKnife M6 (CK-M6) Series introduced a multileaf collimator (MLC) for extending its capability from stereotactic radiosurgery/stereotactic radiotherapy (SBRT) to conventionally fractionated radiotherapy. This work is to investigate the dosimetric quality of plans that are generated using MLC-shaped beams on the CK-M6, as well as their delivery time, via comparisons with the intensity modulated radiotherapy plans that were clinically used on a Varian Linac for treating hepatic lesions. Nine patient cases were selected and divided into three groups with three patients in each group: (1) the group-one patients were treated conventionally (25 fractions); (2) the group-two patients were treated with SBRT-like hypofractionation (5 fractions); and (3) the group-three patients were treated similar to group-one patients, but with two planning target volumes (PTVs) and two different prescription dose levels correspondingly. The clinically used plans were generated on the eclipse treatment planning system (TPS) and delivered on a Varian Linac (E-V plans). The multiplan (MP) TPS was used to replan these clinical cases with the MLC as the beam device for the CK-M6 (C-M plans). After plans were normalized to the same PTV dose coverage, comparisons between the C-M and E-V plans were performed based on D(99%) (percentage of prescription dose received by 99% of the PTV), D(0.1cm(3)) (the percentage of prescription dose to 0.1 cm(3) of the PTV), and doses received by critical structures. Then, the delivery times for the C-M plans will be obtained, which are the MP TPS generated estimations assuming having an imaging interval of 60 s. The difference in D(99%) between C-M and E-V plans is +0.6% on average (+ or - indicating a higher or lower dose from C-M plans than from E-V plans) with a range from -4.1% to +3.8%, and the difference in D(0.1cm(3)) was -1.0% on average with a range from -5.1% to +2.9%. The PTV conformity index (CI) for the C-M plans ranges from 1.07 to 1.29 with a mean of 1.19, slightly inferior to the E-V plans, in which the CI ranges from 1.00 to 1.15 with a mean of 1.07. Accounting for all nine patients in three groups, 45% of the critical structures received a lower mean dose for the C-M plans as compared with the E-V plans, and similarly, 48% received a lower maximum dose. Furthermore, the average difference of the mean critical structure dose between the C-M and E-V plans over all critical structures for all patients showed only +2.10% relative to the prescription dose and the similar comparison finds the average difference of the maximum critical structure dose of only +1.24%. The estimated delivery times for the C-M plans on the CK-M6 range from 18 to 24 minutes while they are from 7 to 13.7 min for the E-V plans on the Varian Linac. For treating hepatic lesions, for the C-M plans that are comparable to E-V plans in quality, the times needed to deliver these C-M plans on the CK-M6 are longer than the delivery time for the E-V plans on the Varian Linac, but may be clinically acceptable.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Shen, Youtao; Zhong, Yuncheng; Lai, Chao-Jen
2013-10-15
Purpose: To measure and investigate the improvement of microcalcification (MC) visibility in cone beam breast CT with a high pitch (75 μm), thick (500 μm) scintillator CMOS/CsI flat panel detector (Dexela 2923, Perkin Elmer).Methods: Aluminum wires and calcium carbonate grains of various sizes were embedded in a paraffin cylinder to simulate imaging of calcifications in a breast. Phantoms were imaged with a benchtop experimental cone beam CT system at various exposure levels. In addition to the Dexela detector, a high pitch (50 μm), thin (150 μm) scintillator CMOS/CsI flat panel detector (C7921CA-09, Hamamatsu Corporation, Hamamatsu City, Japan) and a widelymore » used low pitch (194 μm), thick (600 μm) scintillator aSi/CsI flat panel detector (PaxScan 4030CB, Varian Medical Systems) were also used in scanning for comparison. The images were independently reviewed by six readers (imaging physicists). The MC visibility was quantified as the fraction of visible MCs and measured as a function of the estimated mean glandular dose (MGD) level for various MC sizes and detectors. The modulation transfer functions (MTFs) and detective quantum efficiencies (DQEs) were also measured and compared for the three detectors used.Results: The authors have demonstrated that the use of a high pitch (75 μm) CMOS detector coupled with a thick (500 μm) CsI scintillator helped make the smaller 150–160, 160–180, and 180–200 μm MC groups more visible at MGDs up to 10.8, 9, and 10.8 mGy, respectively. It also made the larger 200–212 and 212–224 μm MC groups more visible at MGDs up to 7.2 mGy. No performance improvement was observed for 224–250 μm or larger size groups. With the higher spatial resolution of the Dexela detector based system, the apparent dimensions and shapes of MCs were more accurately rendered. The results show that with the aforementioned detector, a 73% visibility could be achieved in imaging 160–180 μm MCs as compared to 28% visibility achieved by the low pitch (194 μm) aSi/CsI flat panel detector. The measurements confirm that the Hamamatsu detector has the highest MTF, followed by the Dexel detector, and then the Varian detector. However, the Dexela detector, with its thick (500 μm) CsI scintillator and low noise level, has the highest DQE at all frequencies, followed by the Varian detector, and then the Hamamatsu detector. The findings on the MC visibility correlated well with the differences in MTFs, noise power spectra, and DQEs measured for these three detectors.Conclusions: The authors have demonstrated that the use of the CMOS type Dexela detector with its high pitch (75 μm) and thick (500 μm) CsI scintillator could help improve the MC visibility. However, the improvement depended on the exposure level and the MC size. For imaging larger MCs or scanning at high exposure levels, there was little advantage in using the Dexela detector as compared to the aSi type Varian detector. These findings correlate well with the higher measured DQEs of the Dexela detector, especially at higher frequencies.« less
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Shen, Youtao; Zhong, Yuncheng; Lai, Chao-Jen; Wang, Tianpeng; Shaw, Chris C.
2013-01-01
Purpose: To measure and investigate the improvement of microcalcification (MC) visibility in cone beam breast CT with a high pitch (75 μm), thick (500 μm) scintillator CMOS/CsI flat panel detector (Dexela 2923, Perkin Elmer). Methods: Aluminum wires and calcium carbonate grains of various sizes were embedded in a paraffin cylinder to simulate imaging of calcifications in a breast. Phantoms were imaged with a benchtop experimental cone beam CT system at various exposure levels. In addition to the Dexela detector, a high pitch (50 μm), thin (150 μm) scintillator CMOS/CsI flat panel detector (C7921CA-09, Hamamatsu Corporation, Hamamatsu City, Japan) and a widely used low pitch (194 μm), thick (600 μm) scintillator aSi/CsI flat panel detector (PaxScan 4030CB, Varian Medical Systems) were also used in scanning for comparison. The images were independently reviewed by six readers (imaging physicists). The MC visibility was quantified as the fraction of visible MCs and measured as a function of the estimated mean glandular dose (MGD) level for various MC sizes and detectors. The modulation transfer functions (MTFs) and detective quantum efficiencies (DQEs) were also measured and compared for the three detectors used. Results: The authors have demonstrated that the use of a high pitch (75 μm) CMOS detector coupled with a thick (500 μm) CsI scintillator helped make the smaller 150–160, 160–180, and 180–200 μm MC groups more visible at MGDs up to 10.8, 9, and 10.8 mGy, respectively. It also made the larger 200–212 and 212–224 μm MC groups more visible at MGDs up to 7.2 mGy. No performance improvement was observed for 224–250 μm or larger size groups. With the higher spatial resolution of the Dexela detector based system, the apparent dimensions and shapes of MCs were more accurately rendered. The results show that with the aforementioned detector, a 73% visibility could be achieved in imaging 160–180 μm MCs as compared to 28% visibility achieved by the low pitch (194 μm) aSi/CsI flat panel detector. The measurements confirm that the Hamamatsu detector has the highest MTF, followed by the Dexel detector, and then the Varian detector. However, the Dexela detector, with its thick (500 μm) CsI scintillator and low noise level, has the highest DQE at all frequencies, followed by the Varian detector, and then the Hamamatsu detector. The findings on the MC visibility correlated well with the differences in MTFs, noise power spectra, and DQEs measured for these three detectors. Conclusions: The authors have demonstrated that the use of the CMOS type Dexela detector with its high pitch (75 μm) and thick (500 μm) CsI scintillator could help improve the MC visibility. However, the improvement depended on the exposure level and the MC size. For imaging larger MCs or scanning at high exposure levels, there was little advantage in using the Dexela detector as compared to the aSi type Varian detector. These findings correlate well with the higher measured DQEs of the Dexela detector, especially at higher frequencies. PMID:24089917
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Shen, Youtao; Zhong, Yuncheng; Lai, Chao-Jen; Wang, Tianpeng; Shaw, Chris C
2013-10-01
To measure and investigate the improvement of microcalcification (MC) visibility in cone beam breast CT with a high pitch (75 μm), thick (500 μm) scintillator CMOS/CsI flat panel detector (Dexela 2923, Perkin Elmer). Aluminum wires and calcium carbonate grains of various sizes were embedded in a paraffin cylinder to simulate imaging of calcifications in a breast. Phantoms were imaged with a benchtop experimental cone beam CT system at various exposure levels. In addition to the Dexela detector, a high pitch (50 μm), thin (150 μm) scintillator CMOS/CsI flat panel detector (C7921CA-09, Hamamatsu Corporation, Hamamatsu City, Japan) and a widely used low pitch (194 μm), thick (600 μm) scintillator aSi/CsI flat panel detector (PaxScan 4030CB, Varian Medical Systems) were also used in scanning for comparison. The images were independently reviewed by six readers (imaging physicists). The MC visibility was quantified as the fraction of visible MCs and measured as a function of the estimated mean glandular dose (MGD) level for various MC sizes and detectors. The modulation transfer functions (MTFs) and detective quantum efficiencies (DQEs) were also measured and compared for the three detectors used. The authors have demonstrated that the use of a high pitch (75 μm) CMOS detector coupled with a thick (500 μm) CsI scintillator helped make the smaller 150-160, 160-180, and 180-200 μm MC groups more visible at MGDs up to 10.8, 9, and 10.8 mGy, respectively. It also made the larger 200-212 and 212-224 μm MC groups more visible at MGDs up to 7.2 mGy. No performance improvement was observed for 224-250 μm or larger size groups. With the higher spatial resolution of the Dexela detector based system, the apparent dimensions and shapes of MCs were more accurately rendered. The results show that with the aforementioned detector, a 73% visibility could be achieved in imaging 160-180 μm MCs as compared to 28% visibility achieved by the low pitch (194 μm) aSi/CsI flat panel detector. The measurements confirm that the Hamamatsu detector has the highest MTF, followed by the Dexel detector, and then the Varian detector. However, the Dexela detector, with its thick (500 μm) CsI scintillator and low noise level, has the highest DQE at all frequencies, followed by the Varian detector, and then the Hamamatsu detector. The findings on the MC visibility correlated well with the differences in MTFs, noise power spectra, and DQEs measured for these three detectors. The authors have demonstrated that the use of the CMOS type Dexela detector with its high pitch (75 μm) and thick (500 μm) CsI scintillator could help improve the MC visibility. However, the improvement depended on the exposure level and the MC size. For imaging larger MCs or scanning at high exposure levels, there was little advantage in using the Dexela detector as compared to the aSi type Varian detector. These findings correlate well with the higher measured DQEs of the Dexela detector, especially at higher frequencies.
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2015-05-19
ablated the targets in the same spots during the PLD process. The beams quickly created craters in these spots. That led to cracks and rapid (in...nanoparticles in the near-IR range taken with the newly acquired (with the support from the DoD Grant) UV -VIS-NIR Spectrophotometer Cary from Varian. As...reagent film has the capability of recovering from the exposure to very high ammonia concentrations without experiencing any irreversible damage . Based on
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Theoretical and material studies on thin-film electroluminescent devices
NASA Technical Reports Server (NTRS)
Summers, C. J.; Goldman, J. A.; Brennan, K.
1988-01-01
During this report period work was performed on the modeling of High Field Electronic Transport in Bulk ZnS and ZnSe, and also on the surface cleaning of Si for MBE growth. Some MBE growth runs have also been performed in the Varian GEN II System. A brief outline of the experimental work is given. A complete summary will be done at the end of the next reporting period at the completion of the investigation. The theoretical studies are included.
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Flexible Case - Grain Interaction in Ballistic Weapon Systems. Volume I. Technical Accomplishments.
1976-10-01
Summary of Test Measurements for Motor No. 2 K-i Appendix I Software Documentation and User ’s Manual L-1 Multiplexor Driver Program for the F Varian...the - .4 case. Thus, any force applied to the steel pl ug causes a slight deflectionof the strain gaged element that can be interpreted as a stress...were extruded by manual pressure.The failure gages were installed in a similar manner with the exception that they were bonded in place with standard AGC
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1989-06-01
University of Southampton. The Chairman of the scientific program for the 3 rd Workshop was designated by The International Advisory Board and approved...Magnetiche, the Minister of Foreign Affairs, the European Research Office of the US Army and the US Navy, Bruker Spectrospin S.r.l., Varian S.p.a...Natural Organic Substances, Department of Chemistry, Polythecnic of Milan; °FIDIA Research Laboratories, Department of Chemistry, Abano Terme (Italy
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Optical Behavior of III-TM-N Materials and Devices
2008-09-26
0296 University of Florida GaN films were doped with Eu to a concentration of ~0.12 at. % during growth at 800 °C by molecular beam epitaxy , with...MAGNETIC SEMICONDUCTOR GROWTH AND CHARACTERIZATION Growth of the films presented occurred in a Varian Gen II by gas-source molecular beam epitaxy ...versus temperature for films of either undoped AlN, single phase AlMnN, or Mn4N. AlCrN films were grown by Molecular Beam Epitaxy (MBE) on c-plane
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1989-10-15
Baker Co., polysorbate (Tween 80), beta- glucuronidase (Type VII), N-methyl-N’-nitro-N-nitrosoguanidine (MNNG), clofibrate , phenobllbital, DCA, TCA...TCOH conjugated wit’a glucuronic acid was determined in an aliquot of sample treated with beta-glucuronidase. A Varian Model 3700 gas chromatQgraph...diaminobenzoic acid fluorimetric assay. The fraction of DNA unwound during the two hour incubation at OC was calculated as: (Total DNA - DS DNA)t
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Counter, S Allen; Nikkhou, Sahar; Brené, Stefan; Damberg, Peter; Sierakowiak, Adam; Klason, Tomas; Berglin, Cecilia Engmér; Laurell, Göran
2013-01-01
Previous in vivo experimental magnetic resonance imaging (MRI) investigations of the mammalian inner ear at 4.7 Tesla have indicated that intravenously injected gadolinium (Gd) penetrates the perilymphatic labyrinth, but not the endolymphatic membranous labyrinth. In the present study, high field MRI at 9.4T was used to visualize the in vivo mouse vestibulo-cochlea system, and to determine whether the endolymphatic system is permeable to a Gd complex. A 9.4 T Varian magnet equipped with a 12 cm inner diameter gradient system with maximum gradient strength of 600 mT/m, a millipede coil (Varian design) and a Gd contrast agent were used for image acquisition in the normal C57 BL-6 mouse. High-resolution 2D and 3D images of the mouse cochlea were acquired within 80 minutes following intravenous injection of Gd. Gd initially permeated the perilymphatic scala tympani and scala vestibuli, and permitted visualization of both cochlear turns from base to apex. The superior, inferior and lateral semicircular canals were subsequently visualized in 3 planes. The membranous endolymphatic labyrinth was impermeable to intravenously injected Gd, and thus showed no apparent uptake of Gd at 9.4T. The 9.4T field strength MRI permitted acquisition of high resolution images of anatomical and physiological features of the normal, wild type mouse perilymphatic inner ear in vivo, and provided further evidence that the endolymphatic system is impermeable to intravenously injected Gd.
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Serban, M; Ruo, R; Sarfehnia, A; Parker, W; Evans, M
2012-07-01
Fast electron Monte Carlo systems have been developed commercially, and implemented for clinical practice in radiation therapy clinics. In this work the Varian eMC (electron Monte Carlo) algorithm was commissioned for clinical electron beams of energies between 6 MeV and 20 MeV. Beam outputs, PDDs and profiles were measured for 29 regular and irregular cutouts using the IC-10 (Wellhöfer) ionization chamber. Detailed percentage depth dose comparisons showed that the agreement between measurement and eMC for different characteristic points on the PDD are generally less than 1 mm and always less than 2 mm, with the eMC calculated values being lower than the measured values. Of the 145 measured output factors, 19 cases fail a ±2% agreement but only 8 cases fail a ±3% agreement between calculation and measurement. Comparison of central axis dose distributions for two electron energies (9, and 20 MeV) for a 10 × 10 cm 2 field, centrally shielded with Pb of width 0 cm (open), 1, 2 and 3 cm, shows agreement to within 3% except near the surface. Comparison of central axis dose distributions for 9 MeV in heterogeneous phantoms including bone and lung inserts showed agreement of 1 mm and 3 mm respectively with measured TLD data. The overall agreement between measurement and eMC calculation has enabled us to begin implementing this calculation model for clinical use. © 2012 American Association of Physicists in Medicine.
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Analysis techniques of charging damage studied on three different high-current ion implanters
NASA Astrophysics Data System (ADS)
Felch, S. B.; Larson, L. A.; Current, M. I.; Lindsey, D. W.
1989-02-01
One of the Greater Silicon Valley Implant Users' Group's recent activities has been to sponsor a round-robin on charging damage, where identical wafers were implanted on three different state-of-the-art, high-current ion implanters. The devices studied were thin-dielectric (250 Å SiO2), polysilicon-gate MOS capacitors isolated by thick field oxide. The three implanters involved were the Varian/Extrion 160XP, the Eaton/Nova 10-80, and the Applied Materials PI9000. Each implanter vendor was given 48 wafers to implant with 100 keV As+ ions at a dose of 1 × 1016 cm-2. Parameters that were varied include the beam current, electron flood gun current, and chamber pressure. The charge-to-breakdown, breakdown voltage, and leakage current of several devices before anneal have been measured. The results from these tests were inconclusive as to the physical mechanism of charging and as to the effectiveness of techniques to reduce its impact on devices. However, the methodology of this study is discussed in detail to aid in the planning of future experiments. Authors' industrial affiliations: S.B. Felch, Varian Research Center, 611 Hansen Way, Palo Alto, CA 94303, USA; L.A. Larson, National Semiconductor Corp., P.O. Box 58090, Santa Clara, CA 95052-8090, USA; M.I. Current, Applied Materials, 3050 Bowers Ave., Santa Clara, CA 95054, USA; D.W. Lindsey, Eaton/NOVA, 931 Benicia Ave, Sunnyvale, CA 94086, USA.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Weston, Mark; Juhasz, Janos
Purpose: The accuracy of treatment delivery for left breast/chest wall patients using deep inspiration breath hold (DIBH) is being monitored using a distance measuring laser (DML) Methods: A commercially available DML (DLS-C15, Dimetix) was mounted behind a Varian TrilogyTM linac. Relative to the machine isocenter, the laser from the beam was offset by 8 cm to the left and by 1 cm in the superior direction. This position was selected because this point is situated on the sternum for the majority of the left breast/chest-wall patients treated at our institution. The Varian Real-Time Positioning Management™ (RPM) guided DIBH treatments atmore » our institution is delivered by placing the system’s tracking block on the patient’s abdomen. The treatment beam is enabled only when the block is in between a predefined abdomen motion range as determined during the CT simulation process. A LabVIEW program was developed to record both beam status (i.e. on/off) and distance measurements. In this study the DML was only used to monitor the position of a single point on the chest and no clinical decisions/adjustments were made based on these measurements. Results and Conclusions: Thus far, 34 fractions have been recorded for 4 patients. As such, the performance of our DIBH treatment technique cannot be fairly evaluated at this point. However, deviations between expected and measured distances have been observed and if these are found to be reproducible, then modifications in our treatment procedures and policies will have to take place.« less
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NASA Astrophysics Data System (ADS)
Maidana, Carlos Omar
As part of an accelerator based Cargo Inspection System, studies were made to develop a Cabinet Safe System by Optimization of the Beam Optics of Microwave Linear Accelerators of the IAC-Varian series working on the S-band and standing wave pi/2 mode. Measurements, modeling and simulations of the main subsystems were done and a Multiple Solenoidal System was designed. This Cabinet Safe System based on a Multiple Solenoidal System minimizes the radiation field generated by the low efficiency of the microwave accelerators by optimizing the RF waveguide system and by also trapping secondaries generated in the accelerator head. These secondaries are generated mainly due to instabilities in the exit window region and particles backscattered from the target. The electron gun was also studied and software for its right mechanical design and for its optimization was developed as well. Besides the standard design method, an optimization of the injection process is accomplished by slightly modifying the gun configuration and by placing a solenoid on the waist position while avoiding threading the cathode with the magnetic flux generated. The Multiple Solenoidal System and the electron gun optimization are the backbone of a Cabinet Safe System that could be applied not only to the 25 MeV IAC-Varian microwave accelerators but, by extension, to machines of different manufacturers as well. Thus, they constitute the main topic of this dissertation.
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SU-E-T-364: 6X FFF and 10X FFF Portal Dosimetry Output Factor Verification: Application for SRS/SBRT
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gulam, M; Bellon, M; Gopal, A
2014-06-01
Purpose: To enhance portal dosimetry of high dose rate SRS/SBRT plan verifications with extensive imager measurement of output factors (OF). Methods: Electronic portal image dosimetry (EPID), implemented on the Varian Edge allows for acquisition of its two energies: 6X FFF and 10 FFF (1400 and 2400 MU/min, respectively) at source to imager distance (SID) =100cm without imager saturation. Square and rectangular aSi OF following EPID calibration were obtained. Data taken was similar to that obtained during beam commissioning (of almost all field sizes from 1×1 to 15×15 and 20×20 cm{sup 2}, [Trilogy] and [Edge], respectively) to construct a table usingmore » the OF tool for use in the Portal Dosimetry Prediction Algorithm (PDIP v11). The Trilogy 6x SRS 1000 MU/min EPID data were taken at 140 SID. The large number of OF were obtained for comparison to that obtained with diode detectors and ion chambers (cc13 for >3×3 field size). As Edge PDIP verification is currently ongoing, EPID measurements of three SRS/SBRT plans for the Trilogy were taken and compared to results obtained prior to these measurements. Results: The relative difference output factors of field sizes 2×2 and higher compared to commissioning data were (mean+/-SD, [range]): Edge 6X (−1.9+/−2.9%, [−5.9%,3.1%]), Edge 10X (−0.7+/−1.2%, [− 3.3%,0.8%] and Trilogy (0.03+/−0.5%, [−1.4%,1.1%]) with EPID over predicting. The results for the 140 SID showed excellent agreement throughout except at the 1×1 to 1×15 and 15×1 field sizes where differences were: −10.6%, −6.0% and −5.8%. The differences were also most pronounced for the 1×1 at 100 SID. They were −7.4% and −11.5% for 6X and 10X, respectively. The Gamma (3%, 1mm) for three clinical plans improved by 8.7+/−1.8%. Conclusion: Results indicate that imager output factor measurements at any SID of high dose rate SRS/SBRT are quite reliable for portal dosimetry plan verification except for the smallest fields. This work was not funded by Varian Oncology Systems. Some authors have other work partly funded by Varian Oncology Systems.« less
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Daily QA of linear accelerators using only EPID and OBI
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sun, Baozhou, E-mail: bsun@radonc.wustl.edu; Goddu, S. Murty; Yaddanapudi, Sridhar
2015-10-15
Purpose: As treatment delivery becomes more complex, there is a pressing need for robust quality assurance (QA) tools to improve efficiency and comprehensiveness while simultaneously maintaining high accuracy and sensitivity. This work aims to present the hardware and software tools developed for comprehensive QA of linear accelerator (LINAC) using only electronic portal imaging devices (EPIDs) and kV flat panel detectors. Methods: A daily QA phantom, which includes two orthogonally positioned phantoms for QA of MV-beams and kV onboard imaging (OBI) is suspended from the gantry accessory holder to test both geometric and dosimetric components of a LINAC and an OBI.more » The MV component consists of a 0.5 cm water-equivalent plastic sheet incorporating 11 circular steel plugs for transmission measurements through multiple thicknesses and one resolution plug for MV-image quality testing. The kV-phantom consists of a Leeds phantom (TOR-18 FG phantom supplied by Varian) for testing low and high contrast resolutions. In the developed process, the existing LINAC tools were used to automate daily acquisition of MV and kV images and software tools were developed for simultaneous analysis of these images. A method was developed to derive and evaluate traditional QA parameters from these images [output, flatness, symmetry, uniformity, TPR{sub 20/10}, and positional accuracy of the jaws and multileaf collimators (MLCs)]. The EPID-based daily QA tools were validated by performing measurements on a detuned 6 MV beam to test its effectiveness in detecting errors in output, symmetry, energy, and MLC positions. The developed QA process was clinically commissioned, implemented, and evaluated on a Varian TrueBeam LINAC (Varian Medical System, Palo Alto, CA) over a period of three months. Results: Machine output constancy measured with an EPID (as compared against a calibrated ion-chamber) is shown to be within ±0.5%. Beam symmetry and flatness deviations measured using an EPID and a 2D ion-chamber array agree within ±0.5% and ±1.2% for crossline and inline profiles, respectively. MLC position errors of 0.5 mm can be detected using a picket fence test. The field size and phantom positioning accuracy can be determined within 0.5 mm. The entire daily QA process takes ∼15 min to perform tests for 5 photon beams, MLC tests, and imaging checks. Conclusions: The exclusive use of EPID-based QA tools, including a QA phantom and simultaneous analysis software tools, has been demonstrated as a viable, efficient, and comprehensive process for daily evaluation of LINAC performance.« less
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NASA Astrophysics Data System (ADS)
Lee, Hyun Jeong; Yea, Ji Woon; Oh, Se An
2015-07-01
Respiratory-gated radiation therapy (RGRT) has been used to minimize the dose to normal tissue in lung-cancer radiotherapy. The present research aims to improve the regularity of respiration in RGRT by using a video-coached respiration guiding system. In the study, 16 patients with lung cancer were evaluated. The respiration signals of the patients were measured by using a realtime position management (RPM) respiratory gating system (Varian, USA), and the patients were trained using the video-coaching respiration guiding system. The patients performed free breathing and guided breathing, and the respiratory cycles were acquired for ~5 min. Then, Microsoft Excel 2010 software was used to calculate the mean and the standard deviation for each phase. The standard deviation was computed in order to analyze the improvement in the respiratory regularity with respect to the period and the displacement. The standard deviation of the guided breathing decreased to 48.8% in the inhale peak and 24.2% in the exhale peak compared with the values for the free breathing of patient 6. The standard deviation of the respiratory cycle was found to be decreased when using the respiratory guiding system. The respiratory regularity was significantly improved when using the video-coaching respiration guiding system. Therefore, the system is useful for improving the accuracy and the efficiency of RGRT.
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Preclinical x-ray dark-field imaging: foreign body detection
NASA Astrophysics Data System (ADS)
Braig, Eva-Maria; Muenzel, Daniela; Fingerle, Alexander; Herzen, Julia; Rummeny, Ernst; Pfeiffer, Franz; Noel, Peter
2017-03-01
The purpose of this study was to evaluate the performance of X-ray dark-field imaging for detection of retained foreign bodies in ex-vivo hands and feet. X-ray dark-field imaging, acquired with a three-grating Talbot-Lau interferometer, has proven to provide access to sub-resolution structures due to small-angle scattering. The study was institutional review board (IRB) approved. Foreign body parts included pieces of wood and metal which were placed in a formalin fixated human ex-vivo hand. The samples were imaged with a grating-based interferometer consisting of a standard microfocus X-ray tube (60 kVp, 100 W) and a Varian 2520-DX detector (pixel size: 127 μm). The attenuation and the dark-field signals provide complementary diagnostic information for this clinical task. With regard to detecting of wooden objects, which are clinically the most relevant, only the dark-field image revealed the locations. The signal is especially strong for dry wood which in comparison is poorly to non-visible in computed tomography. The detection of high atomic-number or dense material and wood-like or porous materials in a single X-ray scan is enabled by the simultaneous acquisition of the conventional attenuation and dark-field signal. Our results reveal that with this approach one can reach a significantly improved sensitivity for detection of foreign bodies, while an easy implementation into the clinical arena is becoming feasible.
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NASA Astrophysics Data System (ADS)
Davidson, S.; Cui, J.; Followill, D.; Ibbott, G.; Deasy, J.
2008-02-01
The Dose Planning Method (DPM) is one of several 'fast' Monte Carlo (MC) computer codes designed to produce an accurate dose calculation for advanced clinical applications. We have developed a flexible machine modeling process and validation tests for open-field and IMRT calculations. To complement the DPM code, a practical and versatile source model has been developed, whose parameters are derived from a standard set of planning system commissioning measurements. The primary photon spectrum and the spectrum resulting from the flattening filter are modeled by a Fatigue function, cut-off by a multiplying Fermi function, which effectively regularizes the difficult energy spectrum determination process. Commonly-used functions are applied to represent the off-axis softening, increasing primary fluence with increasing angle ('the horn effect'), and electron contamination. The patient dependent aspect of the MC dose calculation utilizes the multi-leaf collimator (MLC) leaf sequence file exported from the treatment planning system DICOM output, coupled with the source model, to derive the particle transport. This model has been commissioned for Varian 2100C 6 MV and 18 MV photon beams using percent depth dose, dose profiles, and output factors. A 3-D conformal plan and an IMRT plan delivered to an anthropomorphic thorax phantom were used to benchmark the model. The calculated results were compared to Pinnacle v7.6c results and measurements made using radiochromic film and thermoluminescent detectors (TLD).
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Proton Therapy Dose Characterization and Verification
2013-10-01
predefined acceptance criteria. The Calypso System accurately localizes LT and LO patients in the IBA proton therapy vault at the University of Pennsylvania...earlier vet>ions of mdioct.’omio 0 lm. Thcrr ’" Jechnkul 1\\Sues ~nd challenge~ tluu mu.~t be ad~ts:led and rrsolvtd pnor lo Ibm nppllculion for do...IOcmatthch«enter) from a Varian l100linc1!r aecdcmtur (llnac) dirr<ltd plll’nllel lo nn EBTI film ~nd wtchtd bCiwttn slit!• of ••.lhd wurcr1 M. The plwuom
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2009-03-01
the MV–kV correlation method by sinusoidally moving a block of solid water (measuring 5 × 5× 10 cm3) containing three embedded BB metallic markers (3 mm...in diameter). A 4D motion platform (Washington University, St Louis, MO) holding the block of solid water (figure 1) was programmed to produce the...Varian Medical Systems, Palo Alto, CA). The SS-IMRT plans were delivered to either the moving pelvic phantom or the cube of solid water attached to the
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Rong Yi, E-mail: rong@humonc.wisc.ed; Smilowitz, Jennifer; Tewatia, Dinesh
2010-10-01
Precise calibration of Hounsfield units (HU) to electron density (HU-density) is essential to dose calculation. On-board kV cone beam computed tomography (CBCT) imaging is used predominantly for patients' positioning, but will potentially be used for dose calculation. The impacts of varying 3 imaging parameters (mAs, source-imager distance [SID], and cone angle) and phantom size on the HU number accuracy and HU-density calibrations for CBCT imaging were studied. We proposed a site-specific calibration method to achieve higher accuracy in CBCT image-based dose calculation. Three configurations of the Computerized Imaging Reference Systems (CIRS) water equivalent electron density phantom were used to simulatemore » sites including head, lungs, and lower body (abdomen/pelvis). The planning computed tomography (CT) scan was used as the baseline for comparisons. CBCT scans of these phantom configurations were performed using Varian Trilogy{sup TM} system in a precalibrated mode with fixed tube voltage (125 kVp), but varied mAs, SID, and cone angle. An HU-density curve was generated and evaluated for each set of scan parameters. Three HU-density tables generated using different phantom configurations with the same imaging parameter settings were selected for dose calculation on CBCT images for an accuracy comparison. Changing mAs or SID had small impact on HU numbers. For adipose tissue, the HU discrepancy from the baseline was 20 HU in a small phantom, but 5 times lager in a large phantom. Yet, reducing the cone angle significantly decreases the HU discrepancy. The HU-density table was also affected accordingly. By performing dose comparison between CT and CBCT image-based plans, results showed that using the site-specific HU-density tables to calibrate CBCT images of different sites improves the dose accuracy to {approx}2%. Our phantom study showed that CBCT imaging can be a feasible option for dose computation in adaptive radiotherapy approach if the site-specific calibration is applied.« less
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SU-F-T-256: 4D IMRT Planning Using An Early Prototype GPU-Enabled Eclipse Workstation
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hagan, A; Modiri, A; Sawant, A
Purpose: True 4D IMRT planning, based on simultaneous spatiotemporal optimization has been shown to significantly improve plan quality in lung radiotherapy. However, the high computational complexity associated with such planning represents a significant barrier to widespread clinical deployment. We introduce an early prototype GPU-enabled Eclipse workstation for inverse planning. To our knowledge, this is the first GPUintegrated Eclipse system demonstrating the potential for clinical translation of GPU computing on a major commercially-available TPS. Methods: The prototype system comprised of four NVIDIA Tesla K80 GPUs, with a maximum processing capability of 8.5 Tflops per K80 card. The system architecture consisted ofmore » three key modules: (i) a GPU-based inverse planning module using a highly-parallelizable, swarm intelligence-based global optimization algorithm, (ii) a GPU-based open-source b-spline deformable image registration module, Elastix, and (iii) a CUDA-based data management module. For evaluation, aperture fluence weights in an IMRT plan were optimized over 9 beams,166 apertures and 10 respiratory phases (14940 variables) for a lung cancer case (GTV = 95 cc, right lower lobe, 15 mm cranio-caudal motion). Sensitivity of the planning time and memory expense to parameter variations was quantified. Results: GPU-based inverse planning was significantly accelerated compared to its CPU counterpart (36 vs 488 min, for 10 phases, 10 search agents and 10 iterations). The optimized IMRT plan significantly improved OAR sparing compared to the original internal target volume (ITV)-based clinical plan, while maintaining prescribed tumor coverage. The dose-sparing improvements were: Esophagus Dmax 50%, Heart Dmax 42% and Spinal cord Dmax 25%. Conclusion: Our early prototype system demonstrates that through massive parallelization, computationally intense tasks such as 4D treatment planning can be accomplished in clinically feasible timeframes. With further optimization, such systems are expected to enable the eventual clinical translation of higher-dimensional and complex treatment planning strategies to significantly improve plan quality. This work was partially supported through research funding from National Institutes of Health (R01CA169102) and Varian Medical Systems, Palo Alto, CA, USA.« less
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Counter, S Allen; Nikkhou, Sahar; Brené, Stefan; Damberg, Peter; Sierakowiak, Adam; Klason, Tomas; Berglin, Cecilia Engmér; Laurell, Göran
2013-01-01
Objective: Previous in vivo experimental magnetic resonance imaging (MRI) investigations of the mammalian inner ear at 4.7 Tesla have indicated that intravenously injected gadolinium (Gd) penetrates the perilymphatic labyrinth, but not the endolymphatic membranous labyrinth. In the present study, high field MRI at 9.4T was used to visualize the in vivo mouse vestibulo-cochlea system, and to determine whether the endolymphatic system is permeable to a Gd complex. Methods: A 9.4 T Varian magnet equipped with a 12 cm inner diameter gradient system with maximum gradient strength of 600 mT/m, a millipede coil (Varian design) and a Gd contrast agent were used for image acquisition in the normal C57 BL-6 mouse. Results: High-resolution 2D and 3D images of the mouse cochlea were acquired within 80 minutes following intravenous injection of Gd. Gd initially permeated the perilymphatic scala tympani and scala vestibuli, and permitted visualization of both cochlear turns from base to apex. The superior, inferior and lateral semicircular canals were subsequently visualized in 3 planes. The membranous endolymphatic labyrinth was impermeable to intravenously injected Gd, and thus showed no apparent uptake of Gd at 9.4T. Conclusion: The 9.4T field strength MRI permitted acquisition of high resolution images of anatomical and physiological features of the normal, wild type mouse perilymphatic inner ear in vivo, and provided further evidence that the endolymphatic system is impermeable to intravenously injected Gd. PMID:23894262
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Mancosu, Pietro; Pasquino, Massimo; Reggiori, Giacomo; Masi, Laura; Russo, Serenella; Stasi, Michele
2017-09-01
In modern radiation therapy accurate small fields dosimetry is a challenge and its standardization is fundamental to harmonize delivered dose in different institutions. This study presents a multicenter characterization of MLC-defined small field for Elekta and Varian linear accelerators. Measurements were performed using the Exradin W1 plastic scintillator detector. The project enrolled 24 Italian centers. Each center performed Tissue Phantom Ratio (TPR), in-plane and cross-plane dose profiles of 0.8×0.8cm 2 field, and Output Factor (OF) measurements for square field sizes ranging from 0.8 to 10cm. Set-up conditions were 10cm depth in water phantom at SSD 90cm. Measurements were performed using two twin Exradin W1 plastic scintillator detectors (PSD) correcting for the Cerenkov effect as proposed by the manufacturer. Data analysis from 12 Varian and 12 Elekta centers was performed. Measurements of 7 centers were not included due to cable problems. TPR measurements showed standard deviations (SD)<1%; SD<0.4mm for the profile penumbra was obtained, while FWHM measurements showed SD<0.5mm. OF measurements showed SD<1.5% for field size greater than 2×2cm 2 . Median OFs values were in agreement with the recent bibliography. High degree of consistency was registered for all the considered parameters. This work confirmed the importance of multicenter dosimetric intercomparison. W1 PSD could be considered as a good candidate for small field measurements. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Beaudry, J.; Bergman, A.; British Columbia Cancer Agency - Vancouver Centre, Vancouver, BC
Lung tumours move due to respiratory motion. This is managed during planning by acquiring a 4DCT and capturing the excursion of the GTV (gross tumour volume) throughout the breathing cycle within an IGTV (Internal Gross Tumour Volume) contour. Patients undergo a verification cone-beam CT (CBCT) scan immediately prior to treatment. 3D reconstructed images do not consider tumour motion, resulting in image artefacts, such as blurring. This may lead to difficulty in identifying the tumour on reconstructed images. It would be valuable to create a 4DCBCT reconstruction of the tumour motion to confirm that does indeed remain within the planned IGTV.more » CBCT projections of a Quasar Respiratory Motion Phantom are acquired in Treatment mode (half-fan scan) on a Varian TrueBeam accelerator. This phantom contains a mobile, low-density lung insert with an embedded 3cm diameter tumour object. It is programmed to create a 15s periodic, 2cm (sup/inf) displacement. A Varian Real-time Position Management (RPM) tracking-box is placed on the phantom breathing platform. Breathing phase information is automatically integrated into the projection image files. Using in-house Matlab programs and RTK (Reconstruction Tool Kit) open-source toolboxes, the projections are re-binned into 10 phases and a 4DCBCT scan reconstructed. The planning IGTV is registered to the 4DCBCT and the tumour excursion is verified to remain within the planned contour. This technique successfully reconstructs 4DCBCT images using clinical modes for a breathing phantom. UBC-BCCA ethics approval has been obtained to perform 4DCBCT reconstructions on lung patients (REB#H12-00192). Clinical images will be accrued starting April 2014.« less
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Performance optimization of the Varian aS500 EPID system.
Berger, Lucie; François, Pascal; Gaboriaud, Geneviève; Rosenwald, Jean-Claude
2006-01-01
Today, electronic portal imaging devices (EPIDs) are widely used as a replacement to portal films for patient position verification, but the image quality is not always optimal. The general aim of this study was to optimize the acquisition parameters of an amorphous silicon EPID commercially available for clinical use in radiation therapy with the view to avoid saturation of the system. Special attention was paid to selection of the parameter corresponding to the number of rows acquired between accelerator pulses (NRP) for various beam energies and dose rates. The image acquisition system (IAS2) has been studied, and portal image acquisition was found to be strongly dependent on the accelerator pulse frequency. This frequency is set for each "energy - dose rate" combination of the linear accelerator. For all combinations, the image acquisition parameters were systematically changed to determine their influence on the performances of the Varian aS500 EPID system. New parameters such as the maximum number of rows (MNR) and the number of pulses per frame (NPF) were introduced to explain portal image acquisition theory. Theoretical and experimental values of MNR and NPF were compared, and they were in good agreement. Other results showed that NRP had a major influence on detector saturation and dose per image. A rule of thumb was established to determine the optimum NRP value to be used. This practical application was illustrated by a clinical example in which the saturation of the aSi EPID was avoided by NRP optimization. Moreover, an additional study showed that image quality was relatively insensitive to this parameter.
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Beigi, Manije; Afarande, Fatemeh; Ghiasi, Hosein
2016-01-01
The aim of this study was to compare two bunkers designed by only protocols recommendations and Monte Carlo (MC) based upon data derived for an 18 MV Varian 2100Clinac accelerator. High energy radiation therapy is associated with fast and thermal photoneutrons. Adequate shielding against the contaminant neutron has been recommended by IAEA and NCRP new protocols. The latest protocols released by the IAEA (safety report No. 47) and NCRP report No. 151 were used for the bunker designing calculations. MC method based upon data was also derived. Two bunkers using protocols and MC upon data were designed and discussed. From designed door's thickness, the door designed by the MC simulation and Wu-McGinley analytical method was closer in both BPE and lead thickness. In the case of the primary and secondary barriers, MC simulation resulted in 440.11 mm for the ordinary concrete, total concrete thickness of 1709 mm was required. Calculating the same parameters value with the recommended analytical methods resulted in 1762 mm for the required thickness using 445 mm as recommended by TVL for the concrete. Additionally, for the secondary barrier the thickness of 752.05 mm was obtained. Our results showed MC simulation and the followed protocols recommendations in dose calculation are in good agreement in the radiation contamination dose calculation. Difference between the two analytical and MC simulation methods revealed that the application of only one method for the bunker design may lead to underestimation or overestimation in dose and shielding calculations.
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Poster - 42: TB - ARC: A Total Body photon ARC technique using a commercially available linac
DOE Office of Scientific and Technical Information (OSTI.GOV)
Evans, Michael D. C.; Ruo, Russell; Patrocinio, Ho
We have developed a total body photon irradiation technique using multiple overlapping open field arcs (TB-ARC). This simple technique uses predetermined arc-weights, with MUs calculated as a function of prescription depth only. Patients lie on a stretcher, in the prone/supine treatment position with AP/PA arcs. This treatment position has many advantages including ease of delivery (especially for tall, pediatric or compromised patients), dose uniformity, simplicity for organ shielding, and imaging capabilities. Using a Varian TrueBeam linac, 14 arcs using 40×40 cm{sup 2} 6 MV open photon beams, sweeping across 10 degrees each, complete a 140 degree arc. The nominal SSDmore » at zero degrees is 200 cm. Arcs at the sweep limits (+/− 70 degrees) are differentially weighted and deliver a dose within 10% of the prescription on central axis, at a depth of 10 cm over a superior-inferior length of 275 cm. CT planning using Varian Eclipse enables dose evaluation. A custom made beam spoiler, consisting of a 2.5 m sheet of polycarbonate (6 mm thick) increases the surface dose from 45% to 90%. This beam spoiler also serves as a support in the event that differential attenuation is required for organs such as lung, heart, liver, kidneys. The geometry of the sweeping beam technique limits organ dose (using varying thicknesses of melting alloy) to about 20% and 40% of prescription at dmax and midplane respectively. Digital imaging with a portable DR cassette enables proper attenuator location prior to treatment.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jin, Lihui, E-mail: lihui.jin@fccc.edu; Price, Robert A.; Wang, Lu
Purpose: The CyberKnife M6 (CK-M6) Series introduced a multileaf collimator (MLC) for extending its capability from stereotactic radiosurgery/stereotactic radiotherapy (SBRT) to conventionally fractionated radiotherapy. This work is to investigate the dosimetric quality of plans that are generated using MLC-shaped beams on the CK-M6, as well as their delivery time, via comparisons with the intensity modulated radiotherapy plans that were clinically used on a Varian Linac for treating hepatic lesions. Methods: Nine patient cases were selected and divided into three groups with three patients in each group: (1) the group-one patients were treated conventionally (25 fractions); (2) the group-two patients weremore » treated with SBRT-like hypofractionation (5 fractions); and (3) the group-three patients were treated similar to group-one patients, but with two planning target volumes (PTVs) and two different prescription dose levels correspondingly. The clinically used plans were generated on the ECLIPSE treatment planning system (TPS) and delivered on a Varian Linac (E-V plans). The multiplan (MP) TPS was used to replan these clinical cases with the MLC as the beam device for the CK-M6 (C-M plans). After plans were normalized to the same PTV dose coverage, comparisons between the C-M and E-V plans were performed based on D{sub 99%} (percentage of prescription dose received by 99% of the PTV), D{sub 0.1cm{sup 3}} (the percentage of prescription dose to 0.1 cm{sup 3} of the PTV), and doses received by critical structures. Then, the delivery times for the C-M plans will be obtained, which are the MP TPS generated estimations assuming having an imaging interval of 60 s. Results: The difference in D{sub 99%} between C-M and E-V plans is +0.6% on average (+ or − indicating a higher or lower dose from C-M plans than from E-V plans) with a range from −4.1% to +3.8%, and the difference in D{sub 0.1cm{sup 3}} was −1.0% on average with a range from −5.1% to +2.9%. The PTV conformity index (CI) for the C-M plans ranges from 1.07 to 1.29 with a mean of 1.19, slightly inferior to the E-V plans, in which the CI ranges from 1.00 to 1.15 with a mean of 1.07. Accounting for all nine patients in three groups, 45% of the critical structures received a lower mean dose for the C-M plans as compared with the E-V plans, and similarly, 48% received a lower maximum dose. Furthermore, the average difference of the mean critical structure dose between the C-M and E-V plans over all critical structures for all patients showed only +2.10% relative to the prescription dose and the similar comparison finds the average difference of the maximum critical structure dose of only +1.24%. The estimated delivery times for the C-M plans on the CK-M6 range from 18 to 24 minutes while they are from 7 to 13.7 min for the E-V plans on the Varian Linac. Conclusions: For treating hepatic lesions, for the C-M plans that are comparable to E-V plans in quality, the times needed to deliver these C-M plans on the CK-M6 are longer than the delivery time for the E-V plans on the Varian Linac, but may be clinically acceptable.« less
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Linked gas chromatograph-thermal energy analyzer/ion trap mass spectrometer
DOE Office of Scientific and Technical Information (OSTI.GOV)
Alcaraz, A.; Martin, W.H.; Andresen, B.D.
1991-05-01
The capability of comparing a nitrogen chromatogram generated from a gas chromatograph (GC, Varian model 3400) linked to a thermal energy analyzer (TEA, Thermedics Inc. Model 610) with a total ion chromatogram (from a Finnigan-MAT Ion Trap Mass Spectrometer, ITMS) has provided a new means to screen and identifying trace levels of nitrogen-containing compounds in complex mixtures. Prior to the work described here, it has not been possible to simultaneously acquire TEA and MS data. What was needed was a viable GC-TEA/ITMS interface to combine the capabilities of both instruments. 4 figs.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Benites, J.; Alumno del Posgrado en CBAP, Universidad Autonoma de Nayarit, Carretera Tepic-Compostela km9. C.P. 63780. Xalisco-Nayarit-Mexico; Vega-Carrillo, H. R.
Neutron spectra and the ambient dose equivalent were calculated inside the bunker of a 15 MV Varian linac model CLINAC iX. Calculations were carried out using Monte Carlo methods. Neutron spectra in the vicinity of isocentre show the presence of evaporation and knock-on neutrons produced by the source term, while epithermal and thermal neutron remain constant regardless the distance respect to isocentre, due to room return. Along the maze neutron spectra becomes softer as the detector moves along the maze. The ambient dose equivalent is decreased but do not follow the 1/r{sup 2} rule due to changes in the neutronmore » spectra.« less
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New facility for ion beam materials characterization and modification at Los Alamos
DOE Office of Scientific and Technical Information (OSTI.GOV)
Tesmer, J.R.; Maggiore, C.J.; Parkin, D.M.
1988-01-01
The Ion Beam Materials Laboratory (IBML) is a new Los Alamos laboratory devoted to the characterization and modification of the near surfaces of materials. The primary instruments of the IBML are a tandem electrostatic accelerator, a National Electrostatics Corp. Model 9SDH, coupled with a Varian CF-3000 ion implanter. The unique organizational structure of the IBML as well as the operational characteristics of the 9SDH (after approximately 3000 h of operation) and the laboratories' research capabilities will be discussed. Examples of current research results will also be presented. 5 refs., 2 figs.
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Reactive Atmosphere Processing of BaTiO(3) and Origins of Its Photorefractive Effect
1989-04-01
BaTiO3 structure. Dickinson et al.10 prepared a series of compounds in which various amounts of primarily trivalent metals (Ti 3+ , V, Cr, Mn, Fe, Co...which was contained in a capillary tube mounted next to the BaTiO3 sample. The chromium sample was calibrated against a Varian 3.3x10-47 pitch on KCI...3 1 (13) where M is a trivalent metal ion and [V02+]I is the impurity- related concentration of oxygen vacancies. Note that the charge of the metal
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Xu, H; Song, K; Chetty, I
Purpose: To determine the 6 degree of freedom systematic deviations between 2D/3D and CBCT image registration with various imaging setups and fusion algorithms on the Varian Edge Linac. Methods: An anthropomorphic head phantom with radio opaque targets embedded was scanned with CT slice thicknesses of 0.8, 1, 2, and 3mm. The 6 DOF systematic errors were assessed by comparing 2D/3D (kV/MV with CT) with 3D/3D (CBCT with CT) image registrations with different offset positions, similarity measures, image filters, and CBCT slice thicknesses (1 and 2 mm). The 2D/3D registration accuracy of 51 fractions for 26 cranial SRS patients was alsomore » evaluated by analyzing 2D/3D pre-treatment verification taken after 3D/3D image registrations. Results: The systematic deviations of 2D/3D image registration using kV- kV, MV-kV and MV-MV image pairs were within ±0.3mm and ±0.3° for translations and rotations with 95% confidence interval (CI) for a reference CT with 0.8 mm slice thickness. No significant difference (P>0.05) on target localization was observed between 0.8mm, 1mm, and 2mm CT slice thicknesses with CBCT slice thicknesses of 1mm and 2mm. With 3mm CT slice thickness, both 2D/3D and 3D/3D registrations performed less accurately in longitudinal direction than thinner CT slice thickness (0.60±0.12mm and 0.63±0.07mm off, respectively). Using content filter and using similarity measure of pattern intensity instead of mutual information, improved the 2D/3D registration accuracy significantly (P=0.02 and P=0.01, respectively). For the patient study, means and standard deviations of residual errors were 0.09±0.32mm, −0.22±0.51mm and −0.07±0.32mm in VRT, LNG and LAT directions, respectively, and 0.12°±0.46°, −0.12°±0.39° and 0.06°±0.28° in RTN, PITCH, and ROLL directions, respectively. 95% CI of translational and rotational deviations were comparable to those in phantom study. Conclusion: 2D/3D image registration provided on the Varian Edge radiosurgery, 6 DOF-based system provides accurate target positioning for frameless image-guided cranial stereotactic radiosurgery.« less
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The 1985 pittsburgh conference: a special instrumentation report.
1985-03-29
For the first time in its 36 years of operation, the Pittsburgh Conference and Exposition on Analytical Chemistry and Applied Spectroscopy had a sharp drop in attendance-down 16 percent to 20,731. That loss was attributed to the fact that the meeting was held in New Orleans for the first time, and most of the lost attendees were students and young professionals who had previously come for only 1 day. The number of exhibitors and the number of booths, however, were both up about 15 percent, to 730 and 1856, respectively. A large proportion of that increase was contributed by foreign companies exhibiting for the first time, but there were also some well-known names, such as General Electric and Xerox, making first forays into analytical chemistry. There was also a sharp increase in the number and type of instruments displayed. "The key skill now in analytical chemistry," says Perkin-Elmer president Horace McDonell, Jr., "may be simply finding the right tool to obtain the answers you need." The predominant theme of the show, as it has been for the past few years, was automation of both laboratories and instruments. That trend is having major effects in chemical laboratories, but it is also affecting the instrument companies themselves. At large companies such as Varian, Beckman, and Perkin-Elmer, as much as 50 percent of the research and development budget is now going toward development of software-a much higher percentage than it was even 5 years ago. Another trend in automation also seemed clear at the show. As recently as 2 or 3 years ago, much of the available software for chemistry was designed for Apple and similar computers. Now, the laboratory standard is the IBM PC. As a representative of another company that manufactures computers noted with only slight exaggeration, "There's probably not a booth on the floor that doesn't have one."
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, D; Gach, H; Li, H
Purpose: The daily treatment MRIs acquired on MR-IGRT systems, like diagnostic MRIs, suffer from intensity inhomogeneity issue, associated with B1 and B0 inhomogeneities. An improved homomorphic unsharp mask (HUM) filtering method, automatic and robust body segmentation, and imaging field-of-view (FOV) detection methods were developed to compute the multiplicative slow-varying correction field and correct the intensity inhomogeneity. The goal is to improve and normalize the voxel intensity so that the images could be processed more accurately by quantitative methods (e.g., segmentation and registration) that require consistent image voxel intensity values. Methods: HUM methods have been widely used for years. A bodymore » mask is required, otherwise the body surface in the corrected image would be incorrectly bright due to the sudden intensity transition at the body surface. In this study, we developed an improved HUM-based correction method that includes three main components: 1) Robust body segmentation on the normalized image gradient map, 2) Robust FOV detection (needed for body segmentation) using region growing and morphologic filters, and 3) An effective implementation of HUM using repeated Gaussian convolution. Results: The proposed method was successfully tested on patient images of common anatomical sites (H/N, lung, abdomen and pelvis). Initial qualitative comparisons showed that this improved HUM method outperformed three recently published algorithms (FCM, LEMS, MICO) in both computation speed (by 50+ times) and robustness (in intermediate to severe inhomogeneity situations). Currently implemented in MATLAB, it takes 20 to 25 seconds to process a 3D MRI volume. Conclusion: Compared to more sophisticated MRI inhomogeneity correction algorithms, the improved HUM method is simple and effective. The inhomogeneity correction, body mask, and FOV detection methods developed in this study would be useful as preprocessing tools for many MRI-related research and clinical applications in radiotherapy. Authors have received research grants from ViewRay and Varian.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yu, V; Nguyen, D; Tran, A
Purpose: To develop and clinically implement 4π radiotherapy, an inverse optimization platform that maximally utilizes non-coplanar intensity modulated radiotherapy (IMRT) beams to significantly improve critical organ sparing. Methods: A 3D scanner was used to digitize the human and phantom subject surfaces, which were positioned in the computer assisted design (CAD) model of a TrueBeam machine to create a virtual geometrical model, based on which, the feasible beam space was calculated for different tumor locations. Beamlets were computed for all feasible beams using convolution/superposition. A column generation algorithm was employed to optimize patient specific beam orientations and fluence maps. Optimal routingmore » through all selected beams were calculated by a level set method. The resultant plans were converted to XML files and delivered to phantoms in the TrueBeam developer mode. Finally, 4π plans were recomputed in Eclipse and manually delivered to recurrent GBM patients. Results: Compared to IMRT utilizing manually selected beams and volumetric modulated arc therapy plans, markedly improved dosimetry was observed using 4π for the brain, head and neck, liver, lung, and prostate patients. The improvements were due to significantly improved conformality and reduced high dose spillage to organs mediolateral to the PTV. The virtual geometrical model was experimentally validated. Safety margins with 99.9% confidence in collision avoidance were included to the model based model accuracy estimates determined via 300 physical machine to phantom distance measurements. Automated delivery in the developer mode was completed in 10 minutes and collision free. Manual 4 π treatment on the GBM cases resulted in significant brainstem sparing and took 35–45 minutes including multiple images, which showed submillimeter cranial intrafractional motion. Conclusion: The mathematical modeling utilized in 4π is accurate to create and guide highly complex non-coplanar IMRT treatments that consistently and significantly outperform human-operator-created plans. Deliverability of such plans is clinically demonstrated. This work is funded by Varian Medical Systems and the NSF Graduate Research Fellowship DGE-1144087.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jani, S; Kishan, A; O'Connell, D
2014-06-01
Purpose: To investigate if pelvic nodal coverage for prostate patients undergoing intensity modulated radiotherapy (IMRT) can be predicted using mutual image information computed between planning and cone-beam CTs (CBCTs). Methods: Four patients with high-risk prostate adenocarcinoma were treated with IMRT on a Varian TrueBeam. Plans were designed such that 95% of the nodal planning target volume (PTV) received the prescription dose of 45 Gy (N=1) or 50.4 Gy (N=3). Weekly CBCTs (N=25) were acquired and the nodal clinical target volumes and organs at risk were contoured by a physician. The percent nodal volume receiving prescription dose was recorded as amore » ground truth. Using the recorded shifts performed by the radiation therapists at the time of image acquisition, CBCTs were aligned with the planning kVCT. Mutual image information (MI) was calculated between the CBCT and the aligned planning CT within the contour of the nodal PTV. Due to variable CBCT fields-of-view, CBCT images covering less than 90% of the nodal volume were excluded from the analysis, resulting in the removal of eight CBCTs. Results: A correlation coefficient of 0.40 was observed between the MI metric and the percent of the nodal target volume receiving the prescription dose. One patient's CBCTs had clear outliers from the rest of the patients. Upon further investigation, we discovered image artifacts that were present only in that patient's images. When those four images were excluded, the correlation improved to 0.81. Conclusion: This pilot study shows the potential of predicting pelvic nodal dosimetry by computing the mutual image information between planning CTs and patient setup CBCTs. Importantly, this technique does not involve manual or automatic contouring of the CBCT images. Additional patients and more robust exclusion criteria will help validate our findings.« less
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SU-G-BRC-04: Collimator Angle Optimization in Volumetric Modulated Arc Therapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Andersen, A; Johnson, C; Bartlett, G
2016-06-15
Purpose: Volumetric modulated arc therapy (VMAT) has revolutionized radiation treatment by decreasing treatment time and monitor units, thus reducing scattered and whole body radiation dose. As the collimator angle changes the apparent leaf gap becomes larger which can impact plan quality, organ at risk (OAR) sparing as well as IMRT QA passing rate which is investigated. Methods: Two sites (prostate and head and neck) that have maximum utilization of VMAT were investigated. Two previously treated VMAT patients were chosen. For each patient 10 plans were created by maintaining constant optimization constraints while varying collimator angles from 0-90 deg at anmore » interval of 10 degrees for the first arc and the appropriate complimentary angle for the second arc. Plans were created with AAA algorithm using 6 MV beam on a Varian IX machine with Millennium 120 MLC. The dose-volume histogram (DVH) for each plan was exported and dosimetric parameters (D98, D95, D50, D2) as well homogeneity index (HI) and conformity index (CI) were computed. Each plan was validated for QA using ArcCheck with gamma index passing criteria of 2%/2 mm and 3%/3 mm. Additionally, normal tissue complication probability (NTCP) for each OAR was computed using Uzan-Nahum software. Results: The CI values for both sites had no impact as target volume coverage in every collimator angle were the same since it was optimized for adequate coverage. The HI which is representative of DVH gradient or dose uniformity in PTV showed a clear trend in both sites. The NTCP for OAR (brain and cochlea) in H&N plan and (bladder and rectum) in prostate plan showed a distinct superiority for collimator angles between 15-30 deg. The gamma passing rates were not correlated with angle. Conclusion: Based on CI, HI, NTCP and gamma passing index, it can be concluded that collimator angles should be maintained within 15–30 deg.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, K; Able, A
Purpose: To evaluate an Enhanced Dynamic Wedge (EDW) as part of machine commission process with feature study. Methods: The EDW system in this study was from a Truebeam, which is the Linear accelerator manufactured by Varian Medical Systems. The EDW feature vectors includes selected elements. These elements were dosimetric output spots check, field size, wedge angles, dose rate, collimator orientation, and different energy settings. Point dose measurement was done by a PTW farmer chamber, and profiles were measured by Gafchromic EBT2 films positing at different depths of the Solidwater based on the study elements. The output spot measurements were donemore » with PTW farmer chamber with Solidwater setting for all orientation and wedge angles in the EDW system. The profiles comparisons were done by IMRT measurement function in RIT software at version 6.3. And the films were scanned by Vidar scanner. Dosimetry calculation were done by using the same Solidwater scanned by GE LightSpeed CT in Eclipse Treatment Planning System (TPS). Then measurements were compared to simulation results in TPS. Results: The energy average percentage difference between chamber measurement and TPS was 0.16% with standard deviation (SD) at 0.93%. For selected features, the average percentage difference between film measurement and computation was 0.93% with SD at 1.55% in horizontal profiles, and 1.18% with SD at 0.98% at vertical profiles. The average gamma difference for film measurement and TPS computing results was at 0.924 with SD at 0.314. Conclusion: A feature vector was developed to describe the commission of EDW, and developing a complete set of features for sufficiency of commission of a LINAC function could provide optimal commission instance with acceptable confident level of clinical application of the machine. Given the institution specific vector pattern and big data process, it could provide wide range clinical outcome comparison information in application of EDW.« less
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The role of complexity metrics in a multi-institutional dosimetry audit of VMAT
Agnew, Christina E; Hussein, Mohammad; Tsang, Yatman; McWilliam, Alan; Hounsell, Alan R; Clark, Catharine H
2016-01-01
Objective: To demonstrate the benefit of complexity metrics such as the modulation complexity score (MCS) and monitor units (MUs) in multi-institutional audits of volumetric-modulated arc therapy (VMAT) delivery. Methods: 39 VMAT treatment plans were analysed using MCS and MU. A virtual phantom planning exercise was planned and independently measured using the PTW Octavius® phantom and seven29® 2D array (PTW-Freiburg GmbH, Freiburg, Germany). MCS and MU were compared with the median gamma index pass rates (2%/2 and 3%/3 mm) and plan quality. The treatment planning systems (TPS) were grouped by VMAT modelling being specifically designed for the linear accelerator manufacturer's own treatment delivery system (Type 1) or independent of vendor for VMAT delivery (Type 2). Differences in plan complexity (MCS and MU) between TPS types were compared. Results: For Varian® linear accelerators (Varian® Medical Systems, Inc., Palo Alto, CA), MCS and MU were significantly correlated with gamma pass rates. Type 2 TPS created poorer quality, more complex plans with significantly higher MUs and MCS than Type 1 TPS. Plan quality was significantly correlated with MU for Type 2 plans. A statistically significant correlation was observed between MU and MCS for all plans (R = −0.84, p < 0.01). Conclusion: MU and MCS have a role in assessing plan complexity in audits along with plan quality metrics. Plan complexity metrics give some indication of plan deliverability but should be analysed with plan quality. Advances in knowledge: Complexity metrics were investigated for a national rotational audit involving 34 institutions and they showed value. The metrics found that more complex plans were created for planning systems which were independent of vendor for VMAT delivery. PMID:26511276
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Shende, Ravindra; Patel, Ganesh
2017-01-01
Objective of present study is to determine optimum value of DLG and its validation prior to being incorporated in TPS for Varian TrueBeam™ millennium 120 leaves MLC. Partial transmission through the rounded leaf ends of the Multi Leaf Collimator (MLC) causes a conflict between the edges of the light field and radiation field. Parameter account for this partial transmission is called Dosimetric Leaf Gap (DLG). The complex high precession technique, such as Intensity Modulated Radiation Therapy (IMRT), entails the modeling of optimum value of DLG inside Eclipse Treatment Planning System (TPS) for precise dose calculation. Distinct synchronized uniformed extension of sweeping dynamic MLC leaf gap fields created by Varian MLC shaper software were use to determine DLG. DLG measurements performed with both 0.13 cc semi-flex ionization chamber and 2D-Array I-Matrix were used to validate the DLG; similarly, values of DLG from TPS were estimated from predicted dose. Similar mathematical approaches were employed to determine DLG from delivered and TPS predicted dose. DLG determined from delivered dose measured with both ionization chamber (DLG Ion ) and I-Matrix (DLG I-Matrix ) compared with DLG estimate from TPS predicted dose (DLG TPS ). Measurements were carried out for all available 6MV, 10MV, 15MV, 6MVFFF and 10MVFFF beam energies. Maximum and minimum DLG deviation between measured and TPS calculated DLG was found to be 0.2 mm and 0.1 mm, respectively. Both of the measured DLGs (DLG Ion and DLG I-Matrix ) were found to be in a very good agreement with estimated DLG from TPS (DLG TPS ). Proposed method proved to be helpful in verifying and validating the DLG value prior to its clinical implementation in TPS.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
McGlade, J; Kassaee, A
2015-06-15
Purpose: To evaluate planning methods for anal canal cancer and compare the results of 9-field Intensity Modulated Radiotherapy (IMRT), Volumetric Modulated Arc Therapy (Varian, RapidArc), and Proton Pencil Beam Scanning (PBS). Methods: We generated plans with IMRT, RapidArc (RA) and PBS for twenty patients for both initial phase including nodes and cone down phase of treatment using Eclipe (Varian). We evaluated the advantage of each technique for each phase. RA plans used 2 to 4 arcs and various collimator orientations. PBS used two posterior oblique fields. We evaluated the plans comparing dose volume histogram (DVH), locations of hot spots, andmore » PTV dose conformity. Results: Due to complex shape of target, for RA plans, multiple arcs (>2) are required to achieve optimal PTV conformity. When the PTV exceeds 15 cm in the superior-inferior direction, limitations of deliverability start to dominate. The PTV should be divided into a superior and an inferior structure. The optimization is performed with fixed jaws for each structure and collimator set to 90 degrees for the inferior PTV. Proton PBS plans show little advantage in small bowel sparing when treating the nodes. However, PBS plan reduces volumetric dose to the bladder at the cost of higher doses to the perineal skin. IMRT plans provide good target conformity, but they generate hot spots outside of the target volume. Conclusion: When using one planning technique for entire course of treatment, Multiple arc (>2) RA plans are better as compared to IMRT and PBS plans. When combining techniques, RA for the initial phase in combination with PBS for the cone down phase results in the most optimal plans.« less
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SU-F-T-431: Dosimetric Validation of Acuros XB Algorithm for Photon Dose Calculation in Water
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kumar, L; Yadav, G; Kishore, V
2016-06-15
Purpose: To validate the Acuros XB algorithm implemented in Eclipse Treatment planning system version 11 (Varian Medical System, Inc., Palo Alto, CA, USA) for photon dose calculation. Methods: Acuros XB is a Linear Boltzmann transport equation (LBTE) solver that solves LBTE equation explicitly and gives result equivalent to Monte Carlo. 6MV photon beam from Varian Clinac-iX (2300CD) was used for dosimetric validation of Acuros XB. Percentage depth dose (PDD) and profiles (at dmax, 5, 10, 20 and 30 cm) measurements were performed in water for field size ranging from 2×2,4×4, 6×6, 10×10, 20×20, 30×30 and 40×40 cm{sup 2}. Acuros XBmore » results were compared against measurements and anisotropic analytical algorithm (AAA) algorithm. Results: Acuros XB result shows good agreement with measurements, and were comparable to AAA algorithm. Result for PDD and profiles shows less than one percent difference from measurements, and from calculated PDD and profiles by AAA algorithm for all field size. TPS calculated Gamma error histogram values, average gamma errors in PDD curves before dmax and after dmax were 0.28, 0.15 for Acuros XB and 0.24, 0.17 for AAA respectively, average gamma error in profile curves in central region, penumbra region and outside field region were 0.17, 0.21, 0.42 for Acuros XB and 0.10, 0.22, 0.35 for AAA respectively. Conclusion: The dosimetric validation of Acuros XB algorithms in water medium was satisfactory. Acuros XB algorithm has potential to perform photon dose calculation with high accuracy, which is more desirable for modern radiotherapy environment.« less
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Jamema, S V; Upreti, R R; Sharma, S; Deshpande, D D
2008-09-01
The purpose of this work is to report the results of commissioning and to establish a quality assurance (QA) program for commercial 3D treatment planning system (TPS) based on IAEA Technical Report Series 430. Eclipse v 7.3.10, (Varian Medical Systems, Palo Alto, CA, U.S.A.) TPS was commissioned for a Clinac 6EX (Varian Medical Systems, Palo Alto, CA, USA) linear accelerator. CT images of a phantom with various known in-homogeneities were acquired. The images were transferred to TPS and tested for various parameters related to patient data acquisition, anatomical modeling, plan evaluation and dose calculation. Dosimetric parameters including open, asymmetric and wedged shaped fields, oblique incidence, buildup region behavior and SSD dependence were evaluated. Representative clinical cases were tested for MU calculation and point doses. The maximum variation between the measured and the known CT numbers was 20 +/- 11.7 HU (1 SD). The results of all non-dosimetric tests were found within tolerance, however expansion at the sharp corners was found distorted. The accuracy of the DVH calculations depends on the grid size. TPS calculations of all the dosimetric parameters were in good agreement with the measured values, however for asymmetric open and wedged fields, few points were found out of tolerance. Smaller grid size calculation showed better agreement of dose calculation in the build-up region. Independent tests for MU calculation showed a variation within +/-2% (relative to planning system), meanwhile variation of 3.0% was observed when the central axis was blocked. The test results were in agreement with the tolerance specified by IAEA TRS 430. A subset of the commissioning tests has been identified as a baseline data for an ongoing QA program.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ferreira, C; Ahmad, S; Firestone, B
Purpose: To compare dosimetrically three plan calculation systems (Plato, Varian Brachytherapy, and in-house-made Excel) available for I-125 COMS eye plaque treatment with measurement. Methods: All systems assume homogeneous media and calculations are based on a three-dimensional Cartesian coordinates, Plato and Brachytherapy Planning are based on AAPM TG-43 and the in-house Excel program only on inverse square corrections. Doses at specific depths were measured with EBT3 Gafchromic film from a fully loaded and a partially loaded 16 mm plaque (13 and 8 seeds respectively, I-125, model 6711 GE, Oncura). Measurements took place in a water tank, utilizing solid water blocks andmore » a 3D-printed plaque holder. Taking advantage that gafchromic film has low energy dependence, a dose step wedge was delivered with 6 MV photon beam from a Varian 2100 EX linac for calibration. The gray-scale to dose in cGy was obtained with an Epson Expression 10000 XL scanner in the green channel. Treatment plans were generated for doses of 2200 cGy to a depth of 7 mm, and measurements were taken on a sagittal plane. Results: The calculated dose at the prescription point was 2242, 2344, and 2211 cGy with Excel, Brachyvision and Plato respectively for a fully loaded plaque, for the partially loaded plaque the doses were 2266, 2477, and 2193 cGy respectively. At 5 mm depth the doses for Brachyvision and Plato were comparable (3399 and 3267 cGy respectively), however, the measured dose in film was 3180 cGy which was lower by as much as 6.4% in the fully loaded plaque and 7.6% in the partially loaded plaque. Conclusion: Careful methodology and calibration are essential when measuring doses at specific depth due to the sensitivity and rapid dose fall off of I-125.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Cui, Congwu; Zeng, Grace G.; Department of Radiation Oncology, University of Toronto, Toronto, ON
2014-08-15
We investigated the setup variations over the treatment courses of 113 patients with intact prostate treated with 78Gy/39fx. Institutional standard bladder and bowel preparation and image guidance protocols were used in CT simulation and treatment. The RapidArc treatment plans were optimized in Varian Eclipse treatment planning system and delivered on Varian 2100X Clinacs equipped with On-Board Imager to localize the target before beam-on. The setup variations were calculated in terms of mean and standard deviation of couch shifts. No correlation was observed between the mean shift and standard deviation over the treatment course and patient age, initial prostate volume andmore » rectum size. The mean shifts in the first and last 5 fractions are highly correlated (P < 10{sup −10}) while the correlation of the standard deviations cannot be determined. The Mann-Kendall tests indicate trends of the mean daily Ant-Post and Sup-Inf shifts of the group. The target is inferior by ∼1mm to the planned position when the treatment starts and moves superiorly, approaching the planned position at 10th fraction, and then gradually moves back inferiorly by ∼1mm in the remain fractions. In the Ant-Post direction, the prostate gradually moves posteriorly during the treatment course from a mean shift of ∼2.5mm in the first fraction to ∼1mm in the last fraction. It may be related to a systematic rectum size change in the progress of treatment. The biased mean shifts in Ant-Post and Sup-Inf direction of most patients suggest systematically larger rectum and smaller bladder during the treatment than at CT simulation.« less
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NASA Astrophysics Data System (ADS)
Townson, Reid W.; Zavgorodni, Sergei
2014-12-01
In GPU-based Monte Carlo simulations for radiotherapy dose calculation, source modelling from a phase-space source can be an efficiency bottleneck. Previously, this has been addressed using phase-space-let (PSL) sources, which provided significant efficiency enhancement. We propose that additional speed-up can be achieved through the use of a hybrid primary photon point source model combined with a secondary PSL source. A novel phase-space derived and histogram-based implementation of this model has been integrated into gDPM v3.0. Additionally, a simple method for approximately deriving target photon source characteristics from a phase-space that does not contain inheritable particle history variables (LATCH) has been demonstrated to succeed in selecting over 99% of the true target photons with only ~0.3% contamination (for a Varian 21EX 18 MV machine). The hybrid source model was tested using an array of open fields for various Varian 21EX and TrueBeam energies, and all cases achieved greater than 97% chi-test agreement (the mean was 99%) above the 2% isodose with 1% / 1 mm criteria. The root mean square deviations (RMSDs) were less than 1%, with a mean of 0.5%, and the source generation time was 4-5 times faster. A seven-field intensity modulated radiation therapy patient treatment achieved 95% chi-test agreement above the 10% isodose with 1% / 1 mm criteria, 99.8% for 2% / 2 mm, a RMSD of 0.8%, and source generation speed-up factor of 2.5. Presented as part of the International Workshop on Monte Carlo Techniques in Medical Physics
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Beigi, Manije; Afarande, Fatemeh; Ghiasi, Hosein
2016-01-01
Aim The aim of this study was to compare two bunkers designed by only protocols recommendations and Monte Carlo (MC) based upon data derived for an 18 MV Varian 2100Clinac accelerator. Background High energy radiation therapy is associated with fast and thermal photoneutrons. Adequate shielding against the contaminant neutron has been recommended by IAEA and NCRP new protocols. Materials and methods The latest protocols released by the IAEA (safety report No. 47) and NCRP report No. 151 were used for the bunker designing calculations. MC method based upon data was also derived. Two bunkers using protocols and MC upon data were designed and discussed. Results From designed door's thickness, the door designed by the MC simulation and Wu–McGinley analytical method was closer in both BPE and lead thickness. In the case of the primary and secondary barriers, MC simulation resulted in 440.11 mm for the ordinary concrete, total concrete thickness of 1709 mm was required. Calculating the same parameters value with the recommended analytical methods resulted in 1762 mm for the required thickness using 445 mm as recommended by TVL for the concrete. Additionally, for the secondary barrier the thickness of 752.05 mm was obtained. Conclusion Our results showed MC simulation and the followed protocols recommendations in dose calculation are in good agreement in the radiation contamination dose calculation. Difference between the two analytical and MC simulation methods revealed that the application of only one method for the bunker design may lead to underestimation or overestimation in dose and shielding calculations. PMID:26900357
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DOE Office of Scientific and Technical Information (OSTI.GOV)
DiCostanzo, D; Ayan, A; Woollard, J
Purpose: To predict potential failures of hardware within the Varian TrueBeam linear accelerator in order to proactively replace parts and decrease machine downtime. Methods: Machine downtime is a problem for all radiation oncology departments and vendors. Most often it is the result of unexpected equipment failure, and increased due to lack of in-house clinical engineering support. Preventative maintenance attempts to assuage downtime, but often is ineffective at preemptively preventing many failure modes such as MLC motor failures, the need to tighten a gantry chain, or the replacement of a jaw motor, among other things. To attempt to alleviate downtime, softwaremore » was developed in house that determines the maximum value of each axis enumerated in the Truebeam trajectory log files. After patient treatments, this data is stored in a SQL database. Microsoft Power BI is used to plot the average maximum error of each day of each machine as a function of time. The results are then correlated with actual faults that occurred at the machine with the help of Varian service engineers. Results: Over the course of six months, 76,312 trajectory logs have been written into the database and plotted in Power BI. Throughout the course of analysis MLC motors have been replaced on three machines due to the early warning of the trajectory log analysis. The service engineers have also been alerted to possible gantry issues on one occasion due to the aforementioned analysis. Conclusion: Analyzing the trajectory log data is a viable and effective early warning system for potential failures of the TrueBeam linear accelerator. With further analysis and tightening of the tolerance values used to determine a possible imminent failure, it should be possible to pinpoint future issues more thoroughly and for more axes of motion.« less
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A novel EPID design for enhanced contrast and detective quantum efficiency
NASA Astrophysics Data System (ADS)
Rottmann, Joerg; Morf, Daniel; Fueglistaller, Rony; Zentai, George; Star-Lack, Josh; Berbeco, Ross
2016-09-01
Beams-eye-view imaging applications such as real-time soft-tissue motion estimation are hindered by the inherently low image contrast of electronic portal imaging devices (EPID) currently available for clinical use. We introduce and characterize a novel EPID design that provides substantially increased detective quantum efficiency (DQE), contrast-to-noise ratio (CNR) and sensitivity without degradation in spatial resolution. The prototype design features a stack of four conventional EPID layers combined with low noise integrated readout electronics. Each layer consists of a copper plate, a scintillator (\\text{G}{{\\text{d}}2}{{\\text{O}}2}{{\\text{S}}{}}\\text{:Tb} ) and a photodiode/TFT-switch (aSi:H). We characterize the prototype’s signal response to a 6 MV photon beam in terms of modulation transfer function (MTF), DQE and CNR. The presampled MTF is estimated using a slanted slit technique, the DQE is calculated from measured normalized noise power spectra (nNPS) and the MTF and CNR is estimated using a Las Vegas contrast phantom. The prototype has been designed and built to be interchangeable with the current clinical EPID on the Varian TrueBeam platform (AS-1200) in terms of size and data output specifications. Performance evaluation is conducted in absolute values as well as in relative terms using the Varian AS-1200 EPID as a reference detector. A fivefold increase of DQE(0) to about 6.7% was observed by using the four-layered design versus the AS-1200 reference detector. No substantial differences are observed between each layer’s individual MTF and the one for all four layers operating combined indicating that defocusing due to beam divergence is negligible. Also, using four layers instead of one increases the signal to noise ratio by a factor of 1.7.
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Effect of starter culture and turmeric on physico-chemical quality of carabeef pastirma.
Maurya, P; Borpuzari, R N; Nath, D R; Nath, N C
2010-01-01
Carabeef samples were sliced, pressed, cured and divided into 6 groups. Starter cultures (Micrococcus varians M483 (MV), Staphylococcus carnosus (SC), Lactobacillus sakei (LS), M. varians M483+ Lb. sakei and Staph. carnosus + Lb. sakei) were inoculated at the dose of 10(6)-0(7)cfu/g and stored at 10 ± 1°C for 7 days. Uninoculated samples were maintained as control. Samples were then divided into 2 treatment groups. Samples of treatment 1 (T1) were smeared with a paste of turmeric followed by application of a thick layer of the paste of garlic, cumin, black pepper and red pepper whereas, samples of treatment 2 (T2) were applied with a thick layer of spices as above without turmeric. With the gradual fall in pH there was a reduction in water-holding capacity (WHC) of samples. The WHC of samples treated with SC+LS of T1 reduced to 6.3 ± 0.03 cm(2) and those inoculated with MV+LS of T2 to 6.2 ± 0.03 cm(2). The extract release volume (ERV) increased in all samples during storage. The least ERV of 11.7 and 11.6 ml were recorded in samples inoculated with MV of T1 and T2, respectively. The tyrosine (TV) and thiobarbituric acid (TBA) number of turmeric treated samples were significantly lower than non turmeric treated samples. The samples inoculated with LS had the least TV of 30.9 mg tyrosine/100 g of meat and TBA number of 0.06 mg manoladehyde/kg of meat. Samples inoculated with MV and LS of both T1 and T2 were better in physico-chemical qualities.
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Quality assurance methodology for Varian RapidArc treatment plans
Cirino, Eileen T.; Xiong, Li; Mower, Herbert W.
2010-01-01
With the commercial introduction of the Varian RapidArc, a new modality for treatment planning and delivery, the need has arisen for consistent and efficient techniques for performing patient‐specific quality assurance (QA) tests. In this paper we present our methodology for a RapidArc treatment plan QA procedure. For our measurements we used a 2D diode array (MapCHECK) embedded at 5 cm water equivalent depth in MapPHAN 5 phantom and an Exradin A16 ion chamber placed in six different positions in a cylindrical homogeneous phantom (QUASAR). We also checked the MUs for the RapidArc plans by using independent software (RadCalc). The agreement between Eclipse calculations and MapCHECK/MapPHAN 5 measurements was evaluated using both absolute distance‐to‐agreement (DTA) and gamma index with 10% dose threshold (TH), 3% dose difference (DD), and 3 mm DTA. The average agreement was 94.4% for the DTA approach and 96.3% for the gamma index approach. In high‐dose areas, the discrepancy between calculations and ion chamber measurements using the QUASAR phantom was within 4.5% for prostate cases. For the RadCalc calculations, we used the average SSD along the arc; however, for some patients the agreement for the MUs obtained with RadCalc versus Eclipse was inadequate (discrepancy>5%). In these cases, the plan was divided into partial arc plans so that RadCalc could perform a better estimation of the MUs. The discrepancy was further reduced to within ~4% using this approach. Regardless of the variation in prescribed dose and location of the treated areas, we obtained very good results for all patients studied in this paper. PACS number: 87.55.Qr
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Genetic diversity of improved salt tolerant calli of maize (Zea mays L.) using RAPD
NASA Astrophysics Data System (ADS)
Saputro, Triono Bagus; Dianawati, Siti; Sholihah, Nur Fadlillatus; Ermavitalini, Dini
2017-06-01
Maize is one of important cultivated plants in the world, in terms of production rates, utilization rates and demands. Unfortunately, the increment of demands were not followed by the increase of production rates since the cultivation area were significantly decrease. Coastal area is the marginal land that have a good potential to extend the cultivation area. The main challenge of this area is the high content of salt. The aims of this research were try to induce a new varian of local maize through in vitro culture and observe its genetic variation using RAPD. Bluto variety from Madura island was used as an explant in callus induction. Induction of callus were conducted using MS basal medium supplemented with 3 mg/L of 2,4 D under dark condition. While the selection stage was conducted using MS basal medium supplemented with 3 mg/L of 2,4 D with the addition of various concentration of NaCl (0 mg/L; 2500 mg/L; 5000 mg/L; and 7500 mg/L). The research were arranged in a completely randomized design with three replications. The exposion of NaCl were significantly decrease the mass of maize callus. The highest addition of callus weight was 210 mgs in control treatment, while the lowest is in 7500 mg/L with 3 mgs. The RAPD technique was utilized to characterize the genotype of maize callus. Out of five primers, only three primers can produce polymorphic bands named OPA10, OPB07 and OPC02. Taken together, the surviving callus of Bluto varians can be further developed as potential somaclone that has high tolerance to salt stress.
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NASA Astrophysics Data System (ADS)
Strehlow, Brian; Friday, Sarah; McCauley, Mark; Hill, Malcolm
2016-12-01
On coral reefs, Symbiodinium spp. are found in most cnidarian species, but reside in only a small number of sponge species. Of the sponges that do harbor Symbiodinium, most are found in the family Clionaidae, which represents a minor fraction of the poriferan diversity on a reef. Our goal was to determine whether Symbiodinium can be taken up by sponge hosts that do not typically harbor these algal symbionts, and then to follow the fate of any Symbiodinium that enter the intracellular space. We used the filter-feeding capacity of sponges to initiate intracellular interactions between sponge-specialist clade G Symbiodinium and six sponge species that do not associate with Symbiodinium. Using a pulse-chase experimental design, we determined that all of the species we examined captured Symbiodinium, and undamaged intracellular algae were found up to 1 h after inoculation. In a longer-term experiment, Symbiodinium populations in Amphimedon erina persisted in sponge cells for at least 5 d post-inoculation. While no evidence of digestion was detected, the population decreased exponentially after inoculation. We contrast these data with the characteristics of symbiont acquisition and establishment in Cliona varians, which normally harbors Symbiodinium. Explants from experimentally derived aposymbiotic sponges were placed in the field where they acquired Symbiodinium from ambient sources (i.e., we did not inoculate them as in the pulse-chase experiments). We began to detect Symbiodinium cells in C. varians after 12 d, and the algal population increased exponentially until densities approached those typically found in this host (after 128 d). We discuss the implications of this work in light of growing interest in the evolution of specificity between hosts and symbionts, and the fundamental and realized niche of Symbiodinium.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Gräfe, James; Khan, Rao; Meyer, Tyler
2014-08-15
In this study we investigate the deliverability of dosimetric plans generated by the irregular surface compensator (ISCOMP) algorithm for 6 MV photon beams in Eclipse (Varian Medical System, CA). In contrast to physical tissue compensation, the electronic ISCOMP uses MLCs to dynamically modulate the fluence of a photon beam in order to deliver a uniform dose at a user defined plane in tissue. This method can be used to shield critical organs that are located within the treatment portal or improve dose uniformity by tissue compensation in inhomogeneous regions. Three site specific plans and a set of test fields weremore » evaluated using the γ-metric of 3%/ 3 mm on Varian EPID, MapCHECK, and Gafchromic EBT3 film with a clinical tolerance of >95% passing rates. Point dose measurements with an NRCC calibrated ionization chamber were also performed to verify the absolute dose delivered. In all cases the MapCHECK measured plans met the gamma criteria. The mean passing rate for the six EBT3 film field measurements was 96.2%, with only two fields at 93.4 and 94.0% passing rates. The EPID plans passed for fields encompassing the central ∼10 × 10 cm{sup 2} region of the detector; however for larger fields and greater off-axis distances discrepancies were observed and attributed to the profile corrections and modeling of backscatter in the portal dose calculation. The magnitude of the average percentage difference for 21 ion chamber point dose measurements and 17 different fields was 1.4 ± 0.9%, and the maximum percentage difference was −3.3%. These measurements qualify the algorithm for routine clinical use subject to the same pre-treatment patient specific QA as IMRT.« less
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The role of complexity metrics in a multi-institutional dosimetry audit of VMAT.
McGarry, Conor K; Agnew, Christina E; Hussein, Mohammad; Tsang, Yatman; McWilliam, Alan; Hounsell, Alan R; Clark, Catharine H
2016-01-01
To demonstrate the benefit of complexity metrics such as the modulation complexity score (MCS) and monitor units (MUs) in multi-institutional audits of volumetric-modulated arc therapy (VMAT) delivery. 39 VMAT treatment plans were analysed using MCS and MU. A virtual phantom planning exercise was planned and independently measured using the PTW Octavius(®) phantom and seven29(®) 2D array (PTW-Freiburg GmbH, Freiburg, Germany). MCS and MU were compared with the median gamma index pass rates (2%/2 and 3%/3 mm) and plan quality. The treatment planning systems (TPS) were grouped by VMAT modelling being specifically designed for the linear accelerator manufacturer's own treatment delivery system (Type 1) or independent of vendor for VMAT delivery (Type 2). Differences in plan complexity (MCS and MU) between TPS types were compared. For Varian(®) linear accelerators (Varian(®) Medical Systems, Inc., Palo Alto, CA), MCS and MU were significantly correlated with gamma pass rates. Type 2 TPS created poorer quality, more complex plans with significantly higher MUs and MCS than Type 1 TPS. Plan quality was significantly correlated with MU for Type 2 plans. A statistically significant correlation was observed between MU and MCS for all plans (R = -0.84, p < 0.01). MU and MCS have a role in assessing plan complexity in audits along with plan quality metrics. Plan complexity metrics give some indication of plan deliverability but should be analysed with plan quality. Complexity metrics were investigated for a national rotational audit involving 34 institutions and they showed value. The metrics found that more complex plans were created for planning systems which were independent of vendor for VMAT delivery.
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Biltekin, Fatih; Yeginer, Mete; Ozyigit, Gokhan
2015-07-01
We analysed the effects of field size, depth, beam modifier and beam type on the amount of in-field and out-of-field neutron contamination for medical linear accelerators (linacs). Measurements were carried out for three high-energy medical linacs of Elekta Synergy Platform, Varian Clinac DHX High Performance and Philips SL25 using bubble detectors. The photo-neutron measurements were taken in the first two linacs with 18 MV nominal energy, whereas the electro-neutrons were measured in the three linacs with 9 MeV, 10 MeV, 15 MeV and 18 MeV. The central neutron doses increased with larger field sizes as a dramatic drop off was observed in peripheral areas. Comparing with the jaws-shaped open-field of 10 × 10 cm, the motorised and physical wedges contributed to neutron contamination at central axis by 60% and 18%, respectively. The similar dose increment was observed in MLC-shaped fields. The contributions of MLCs were in the range of 55-59% and 19-22% in Elekta and Varian linacs comparing with 10 × 10 and 20 × 20 cm open fields shaped by the jaws, respectively. The neutron doses at shallow depths were found to be higher than the doses found at deeper regions. The electro-neutron dose at the 18 MeV energy was higher than the doses at the electron energies of 15 MeV and 9 MeV by a factor of 3 and 50, respectively. The photo- and electro-neutron dose should be taken into consideration in the radiation treatment with high photon and electron energies. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
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Clinical assessment of the jaw-tracking function in IMRT for a brain tumor
NASA Astrophysics Data System (ADS)
Kim, Jin-Young; Kim, Shin-Wook; Choe, Bo-Young; Suh, Tae-Suk; Park, Sung-Kwang; Jo, Sun-Mi; Oh, Won-Yong; Shin, Jung-Wook; Cho, Gyu-Seok; Nam, Sang-Hee; Chung, Jin-Beom; Kim, Jung-Ki; Lee, Young-Kyu
2015-01-01
Intensity-modulated radiotherapy (IMRT) improves dose conformity and saves critical organs. IMRT is widely used in cases of head and neck, prostate, and brain cancer due to the close location of the targets to critical structures. However, because IMRT has a larger amount of radiation exposure than 3 dimensional-conformal radiation therapy (3D-CRT), it has disadvantages such as increases in the low dose irradiation to normal tissues and in the accumulated dose for the whole volume due to leakage and transmission of the multi-leaf collimator (MLC). The increased accumulated dose and the larger low dose may increase the occurrence of secondary malignant neoplasms. For these reasons, the jaw-tracking function of the TrueBeam (Varian Medical Systems, Palo Alto, CA) was developed to reduce the leakage and the transmission dose of the MLC with linear accelerators. However, the change in the superficial dose has not been verified with a quantitative analysis of the dose reduction in a brain tumor. Therefore, in the present study, we intended to verify the clinical possibility of utilizing the jaw-tracking function for a brain tumor by comparing treatment plans and superficial doses. To accomplish this, we made three types of original treatment plans using Eclipse11 (Varian Medical Systems, Palo Alto, CA): 1) farther than 2 cm from the organs at risk (OAR); 2) within 2 cm of the OAR; and 3) intersecting with the OAR. Jaw-tracking treatment plans were also made with copies of the original treatment plan using Smart LMC Version 11.0.31 (Varian Medical Systems, Palo Alto, CA). A comparison between the original treatment plans and jaw-tracking treatment plans was performed using the difference of the mean dose and maximum dose to the OARs in cumulative Dose Volume Histogram (DVH). In addition, the dependencies of the effects of transmission and the scattering doses according to jaw motion were assessed through the difference in the surface doses. In the DVH comparison, a maximum dose difference of 0.4% was observed between the planning methods in the case of over 2 cm distance, and the maximum dose of 0.6% was obtained for within the 2 cm distance. For the case intersecting with the OAR, the maximum dose difference of 2.3% was achieved. According to these results, the differences in the mean doses and the maximum doses to the OARs ware larger when the OARs and the planning target volume (PTV) were closer. In addition, small differences in the surface dose measurements were observed. In the case of the inside field, the differences were under 2% of the prescription dose while the difference was under 0.1% in the case of the outside field. Therefore, treatment plans with the jaw-tracking function consistently affected the dose reduction for a brain tumor, and the clinical possibility could be verified as the surface dose was not increased.
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Fontanarosa, Davide; Orlandini, Lucia Clara; Andriani, Italo; Bernardi, Luca
2009-10-01
In external photon beam therapies, the technique of dynamic wedge is a well established method for dose inhomogeneity compensation. The introduction of the enhanced dynamic wedge (EDW) on Varian LINACs considerably improved the pre-existing techniques. In the process of commissioning a Varian LINAC into a PINNACLE3 treatment planning system (TPS), the user is required to import quite a few measurements of EDW profiles and percentage depth doses (PDDs). Standard measurement devices like ionization chambers in a water phantom are not the most indicated ones for this situation where each measurement point is obtained by integrating during the entire exposure: Measurements would result to be a very laborious and time consuming operation, most of the times not practically possible. The goal of the present work is to introduce an alternative and hands-on procedure to perform the measurements using a combination of GafchromicTM EBT films, irradiated sideways in one single shot for both profiles and PDDs, and a single standard ionization chamber. The scanned profiles obtained at different depths have easily been imported in the TPS; for the PDD measurements, a correction was proven necessary to account for a "self-shielding" effect introduced by the presence of the films themselves, when irradiated sideways, resulting in an underestimation of the dose at deeper depths. A correction curve was derived comparing TPS open field validated measurements with the curves extracted from GafchromicTM EBT films. Finally, the curve was applied to all the wedged fields PDD measurements and could minimize the errors. The comparison for the 15 MV photon beam between the measured and the calculated 48 profiles and 12 PDDs (field sizes from 5 x 5 to 20 x 20 cm2, wedge angles ranging from 15 degrees to 60 degrees) was acceptable. The confidence limit (CL) was used as fit indicator, as suggested by the ESTRO Booklet No. 7: For the investigated PDDs the maximum value was 6.40 in the build up region and 2.83 beyond the maximum dose point; regarding cross beam profiles, the CLs were below 3 for 85% of the points within the field and for 96% of the points outside the field; in the penumbra region, a more appropriate parameter to evaluate the agreement between calculated and measured doses is the distance to agreement; only 73% of the profiles had CLs below 15, but for the remaining ones, distance-to-agreement values were within 3 mm. A hundred ionization chamber point dose measurements (for square and elongated fields at different depth and for points in field and out of field) were performed in a water phantom and 98 of them confirmed the TPS calculations with differences lower than 3% and considerably lower in most of the cases. This article gives valuable guidance and insight to other physicists attempting to approach EDW commissioning in the PINNACLE TPS software using Gafchromic EBT films.
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Motion vector field upsampling for improved 4D cone-beam CT motion compensation of the thorax
NASA Astrophysics Data System (ADS)
Sauppe, Sebastian; Rank, Christopher M.; Brehm, Marcus; Paysan, Pascal; Seghers, Dieter; Kachelrieß, Marc
2017-03-01
To improve the accuracy of motion vector fields (MVFs) required for respiratory motion compensated (MoCo) CT image reconstruction without increasing the computational complexity of the MVF estimation approach, we propose a MVF upsampling method that is able to reduce the motion blurring in reconstructed 4D images. While respiratory gating improves the temporal resolution, it leads to sparse view sampling artifacts. MoCo image reconstruction has the potential to remove all motion artifacts while simultaneously making use of 100% of the rawdata. However the MVF accuracy is still below the temporal resolution of the CBCT data acquisition. Increasing the number of motion bins would increase reconstruction time and amplify sparse view artifacts, but not necessarily the accuracy of MVF. Therefore we propose a new method to upsample estimated MVFs and use those for MoCo. To estimate the MVFs, a modified version of the Demons algorithm is used. Our proposed method is able to interpolate the original MVFs up to a factor that each projection has its own individual MVF. To validate the method we use an artificially deformed clinical CT scan, with a breathing pattern of a real patient, and patient data acquired with a TrueBeamTM4D CBCT system (Varian Medical Systems). We evaluate our method for different numbers of respiratory bins, each again with different upsampling factors. Employing our upsampling method, motion blurring in the reconstructed 4D images, induced by irregular breathing and the limited temporal resolution of phase-correlated images, is substantially reduced.
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Andersen, Claus E; Nielsen, Søren Kynde; Greilich, Steffen; Helt-Hansen, Jakob; Lindegaard, Jacob Christian; Tanderup, Kari
2009-03-01
A prototype of a new dose-verification system has been developed to facilitate prevention and identification of dose delivery errors in remotely afterloaded brachytherapy. The system allows for automatic online in vivo dosimetry directly in the tumor region using small passive detector probes that fit into applicators such as standard needles or catheters. The system measures the absorbed dose rate (0.1 s time resolution) and total absorbed dose on the basis of radioluminescence (RL) and optically stimulated luminescence (OSL) from aluminum oxide crystals attached to optical fiber cables (1 mm outer diameter). The system was tested in the range from 0 to 4 Gy using a solid-water phantom, a Varian GammaMed Plus 192Ir PDR afterloader, and dosimetry probes inserted into stainless-steel brachytherapy needles. The calibrated system was found to be linear in the tested dose range. The reproducibility (one standard deviation) for RL and OSL measurements was 1.3%. The measured depth-dose profiles agreed well with the theoretical expectations computed with the EGSNRC Monte Carlo code, suggesting that the energy dependence for the dosimeter probes (relative to water) is less than 6% for source-to-probe distances in the range of 2-50 mm. Under certain conditions, the RL signal could be greatly disturbed by the so-called stem signal (i.e., unwanted light generated in the fiber cable upon irradiation). The OSL signal is not subject to this source of error. The tested system appears to be adequate for in vivo brachytherapy dosimetry.
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Improved scatter correction using adaptive scatter kernel superposition
NASA Astrophysics Data System (ADS)
Sun, M.; Star-Lack, J. M.
2010-11-01
Accurate scatter correction is required to produce high-quality reconstructions of x-ray cone-beam computed tomography (CBCT) scans. This paper describes new scatter kernel superposition (SKS) algorithms for deconvolving scatter from projection data. The algorithms are designed to improve upon the conventional approach whose accuracy is limited by the use of symmetric kernels that characterize the scatter properties of uniform slabs. To model scatter transport in more realistic objects, nonstationary kernels, whose shapes adapt to local thickness variations in the projection data, are proposed. Two methods are introduced: (1) adaptive scatter kernel superposition (ASKS) requiring spatial domain convolutions and (2) fast adaptive scatter kernel superposition (fASKS) where, through a linearity approximation, convolution is efficiently performed in Fourier space. The conventional SKS algorithm, ASKS, and fASKS, were tested with Monte Carlo simulations and with phantom data acquired on a table-top CBCT system matching the Varian On-Board Imager (OBI). All three models accounted for scatter point-spread broadening due to object thickening, object edge effects, detector scatter properties and an anti-scatter grid. Hounsfield unit (HU) errors in reconstructions of a large pelvis phantom with a measured maximum scatter-to-primary ratio over 200% were reduced from -90 ± 58 HU (mean ± standard deviation) with no scatter correction to 53 ± 82 HU with SKS, to 19 ± 25 HU with fASKS and to 13 ± 21 HU with ASKS. HU accuracies and measured contrast were similarly improved in reconstructions of a body-sized elliptical Catphan phantom. The results show that the adaptive SKS methods offer significant advantages over the conventional scatter deconvolution technique.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Labine, Alexandre; Carrier, Jean-François; Bedwani, Stéphane
2014-08-15
Purpose: To investigate an automatic bronchial and vessel bifurcations detection algorithm for deformable image registration (DIR) assessment to improve lung cancer radiation treatment. Methods: 4DCT datasets were acquired and exported to Varian treatment planning system (TPS) EclipseTM for contouring. The lungs TPS contour was used as the prior shape for a segmentation algorithm based on hierarchical surface deformation that identifies the deformed lungs volumes of the 10 breathing phases. Hounsfield unit (HU) threshold filter was applied within the segmented lung volumes to identify blood vessels and airways. Segmented blood vessels and airways were skeletonised using a hierarchical curve-skeleton algorithm basedmore » on a generalized potential field approach. A graph representation of the computed skeleton was generated to assign one of three labels to each node: the termination node, the continuation node or the branching node. Results: 320 ± 51 bifurcations were detected in the right lung of a patient for the 10 breathing phases. The bifurcations were visually analyzed. 92 ± 10 bifurcations were found in the upper half of the lung and 228 ± 45 bifurcations were found in the lower half of the lung. Discrepancies between ten vessel trees were mainly ascribed to large deformation and in regions where the HU varies. Conclusions: We established an automatic method for DIR assessment using the morphological information of the patient anatomy. This approach allows a description of the lung's internal structure movement, which is needed to validate the DIR deformation fields for accurate 4D cancer treatment planning.« less
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NASA Astrophysics Data System (ADS)
Vazquez-Quino, L. A.; Huerta-Hernandez, C. I.; Rangaraj, D.
2017-05-01
MobiusFX, an add-on software module from Mobius Medical Systems for IMRT and VMAT QA, uses measurements in linac treatment logs to calculate and verify the 3D dose delivered to patients. In this study, 10 volumetric-modulated arc therapy (VMAT) prostate plans were planned and delivered in a Varian TrueBeam linac. The plans consisted of beams with 6 and 10 MV energy and 2 to 3 arcs per plan. The average gamma value with criterion of 3% and 3mm MobiusFX and TPS: 99.96%, 2% and 2mm MobiusFX and TPS: 98.70 %. Further comparison with ArcCheck measurements was conducted.
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An investigation on some of the tumor treatment cases using x-rays and electron beams
NASA Astrophysics Data System (ADS)
Ucar, Burcu; Yigitoglu, Ibrahim; Arslan Kabalay, Ipek; Altiparmak, Duygu; Kilicaslan, Sinem
2015-07-01
In this work, we discussed some of the applications which X-rays and electron beam used in radiotherapy for tumor treatments. This study has been performed at Radiation Oncology Department, Medicine Faculty in Gaziosmanpasa University by using the VARIAN CLINICA DHX linear accelerator which is operated in the range of 6 MeV - 15 MeV. Processes for the treatments that X-rays used for pancreas, bladder and prostate tumors and the processes that the electron beam used for some of the derm tumors are studied. Effects of X-rays and electron beams to treatments process are examined and the obtained results are presented comparatively.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mynampati, D; Scripes, P Godoy; Kuo, H
2015-06-15
Purpose: To evaluate dosimetric differences between superposition beam model (AAA) and determinant photon transport solver (AXB) in lung SBRT and Cranial SRS dose computations. Methods: Ten Cranial SRS and ten Lung SBRT plans using Varian, AAA -11.0 were re-planned using Acuros -XB-11.0 with fixed MU. 6MV photon Beam model with HD120-MLC used for dose calculations. Four non-coplanar conformal arcs used to deliver 21Gy or 18Gy to SRS targets (0.4 to 6.2cc). 54Gy (3Fractions) or 50Gy (5Fractions) was planned for SBRT targets (7.3 to 13.9cc) using two VAMT non-coplanar arcs. Plan comparison parameters were dose to 1% PTV volume (D1), dosemore » to 99% PTV volume( D99), Target mean (Dmean), Conformity index (ratio of prescription isodose volume to PTV), Homogeneity Index [ (D2%-D98%)/Dmean] and R50 (ratio of 50% of prescription isodose volume to PTV). OAR parameters were Brain volume receiving 12Gy dose (V12Gy) and maximum dose (D0.03) to Brainstem for SRS. For lung SBRT, maximum dose to Heart and Cord, Mean lung dose (MLD) and volume of lung receiving 20Gy (V20Gy) were computed. PTV parameters compared by percentage difference between AXB and AAA parameters. OAR parameters and HI compared by absolute difference between two calculations. For analysis, paired t-test performed over the parameters. Results: Compared to AAA, AXB SRS plans have on average 3.2% lower D99, 6.5% lower CI and 3cc less Brain-V12. However, AXB SBRT plans have higher D1, R50 and Dmean by 3.15%, 1.63% and 2.5%. For SRS and SBRT, AXB plans have average HI 2 % and 4.4% higher than AAA plans. In both techniques, all other parameters vary within 1% or 1Gy. In both sets only two parameters have P>0.05. Conclusion: Even though t-test results signify difference between AXB and AAA plans, dose differences in dose estimations by both algorithms are clinically insignificant.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Chang, X; Mazur, T; Yang, D
Purpose: To investigate an approach of automatically recognizing anatomical sites and imaging views (the orientation of the image acquisition) in 2D X-ray images. Methods: A hierarchical (binary tree) multiclass recognition model was developed to recognize the treatment sites and views in x-ray images. From top to bottom of the tree, the treatment sites are grouped hierarchically from more general to more specific. Each node in the hierarchical model was designed to assign images to one of two categories of anatomical sites. The binary image classification function of each node in the hierarchical model is implemented by using a PCA transformationmore » and a support vector machine (SVM) model. The optimal PCA transformation matrices and SVM models are obtained by learning from a set of sample images. Alternatives of the hierarchical model were developed to support three scenarios of site recognition that may happen in radiotherapy clinics, including two or one X-ray images with or without view information. The performance of the approach was tested with images of 120 patients from six treatment sites – brain, head-neck, breast, lung, abdomen and pelvis – with 20 patients per site and two views (AP and RT) per patient. Results: Given two images in known orthogonal views (AP and RT), the hierarchical model achieved a 99% average F1 score to recognize the six sites. Site specific view recognition models have 100 percent accuracy. The computation time to process a new patient case (preprocessing, site and view recognition) is 0.02 seconds. Conclusion: The proposed hierarchical model of site and view recognition is effective and computationally efficient. It could be useful to automatically and independently confirm the treatment sites and views in daily setup x-ray 2D images. It could also be applied to guide subsequent image processing tasks, e.g. site and view dependent contrast enhancement and image registration. The senior author received research grants from ViewRay Inc. and Varian Medical System.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ouyang, L; Lee, H; Wang, J
2014-06-01
Purpose: To evaluate a moving-blocker-based approach in estimating and correcting megavoltage (MV) and kilovoltage (kV) scatter contamination in kV cone-beam computed tomography (CBCT) acquired during volumetric modulated arc therapy (VMAT). Methods: XML code was generated to enable concurrent CBCT acquisition and VMAT delivery in Varian TrueBeam developer mode. A physical attenuator (i.e., “blocker”) consisting of equal spaced lead strips (3.2mm strip width and 3.2mm gap in between) was mounted between the x-ray source and patient at a source to blocker distance of 232mm. The blocker was simulated to be moving back and forth along the gantry rotation axis during themore » CBCT acquisition. Both MV and kV scatter signal were estimated simultaneously from the blocked regions of the imaging panel, and interpolated into the un-blocked regions. Scatter corrected CBCT was then reconstructed from un-blocked projections after scatter subtraction using an iterative image reconstruction algorithm based on constraint optimization. Experimental studies were performed on a Catphan 600 phantom and an anthropomorphic pelvis phantom to demonstrate the feasibility of using moving blocker for MV-kV scatter correction. Results: MV scatter greatly degrades the CBCT image quality by increasing the CT number inaccuracy and decreasing the image contrast, in addition to the shading artifacts caused by kV scatter. The artifacts were substantially reduced in the moving blocker corrected CBCT images in both Catphan and pelvis phantoms. Quantitatively, CT number error in selected regions of interest reduced from 377 in the kV-MV contaminated CBCT image to 38 for the Catphan phantom. Conclusions: The moving-blockerbased strategy can successfully correct MV and kV scatter simultaneously in CBCT projection data acquired with concurrent VMAT delivery. This work was supported in part by a grant from the Cancer Prevention and Research Institute of Texas (RP130109) and a grant from the American Cancer Society (RSG-13-326-01-CCE)« less
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Imaging doses in radiation therapy from kilovoltage cone-beam computed tomography
NASA Astrophysics Data System (ADS)
Hyer, Daniel Ellis
Advances in radiation treatment delivery, such as intensity modulated radiation therapy (IMRT), have made it possible to deliver large doses of radiation with a high degree of conformity. While highly conformal treatments offers the advantage of sparing surrounding normal tissue, this benefit can only be realized if the patient is accurately positioned during each treatment fraction. The need to accurately position the patient has led to the development and use of gantry mounted kilovoltage cone-beam computed tomography (kV-CBCT) systems. These systems are used to acquire high resolution volumetric images of the patient which are then digitally registered with the planning CT dataset to confirm alignment of the patient on the treatment table. While kV-CBCT is a very useful tool for aligning the patient prior to treatment, daily use in a high fraction therapy regimen results in a substantial radiation dose. In order to quantify the radiation dose associated with CBCT imaging, an anthropomorphic phantom representing a 50th percentile adult male and a fiber-optic coupled (FOC) dosimetry system were both constructed as part of this dissertation. These tools were then used to directly measure organ doses incurred during clinical protocols for the head, chest, and pelvis. For completeness, the dose delivered from both the X-ray Volumetric Imager (XVI, Elekta Oncology Systems, Crawley, UK) and the On-Board Imager (OBI, Varian Medical Systems, Palo Alto, CA) were investigated. While this study provided a direct measure of organ doses for estimating risk to the patient, a practical method for estimating organ doses that could be performed with phantoms and dosimeters currently available at most clinics was also desired. To accomplish this goal, a 100 mm pencil ion chamber was used to measure the "cone beam dose index" (CBDI) inside standard CT dose index (CTDI) acrylic phantoms. A weighted CBDI (CBDIw), similar to the weighted CT dose index (CTDIw), was then calculated to represent the average dose in the acrylic phantom. By comparing this value to the measured organ doses, organ dose conversion coefficients were developed. These conversion coefficients allow specific organ doses to be estimated quickly and easily using readily available clinical equipment.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Onozato, Yusuke; Kadoya, Noriyuki, E-mail: kadoya.n@rad.med.tohoku.ac.jp; Fujita, Yukio
2014-06-01
Purpose: The purpose of this study was to estimate the accuracy of the dose calculation of On-Board Imager (Varian, Palo Alto, CA) cone beam computed tomography (CBCT) with deformable image registration (DIR), using the multilevel-threshold (MLT) algorithm and histogram matching (HM) algorithm in pelvic radiation therapy. Methods and Materials: One pelvis phantom and 10 patients with prostate cancer treated with intensity modulated radiation therapy were studied. To minimize the effect of organ deformation and different Hounsfield unit values between planning CT (PCT) and CBCT, we modified CBCT (mCBCT) with DIR by using the MLT (mCBCT{sub MLT}) and HM (mCBCT{sub HM})more » algorithms. To evaluate the accuracy of the dose calculation, we compared dose differences in dosimetric parameters (mean dose [D{sub mean}], minimum dose [D{sub min}], and maximum dose [D{sub max}]) for planning target volume, rectum, and bladder between PCT (reference) and CBCTs or mCBCTs. Furthermore, we investigated the effect of organ deformation compared with DIR and rigid registration (RR). We determined whether dose differences between PCT and mCBCTs were significantly lower than in CBCT by using Student t test. Results: For patients, the average dose differences in all dosimetric parameters of CBCT with DIR were smaller than those of CBCT with RR (eg, rectum; 0.54% for DIR vs 1.24% for RR). For the mCBCTs with DIR, the average dose differences in all dosimetric parameters were less than 1.0%. Conclusions: We evaluated the accuracy of the dose calculation in CBCT, mCBCT{sub MLT}, and mCBCT{sub HM} with DIR for 10 patients. The results showed that dose differences in D{sub mean}, D{sub min}, and D{sub max} in mCBCTs were within 1%, which were significantly better than those in CBCT, especially for the rectum (P<.05). Our results indicate that the mCBCT{sub MLT} and mCBCT{sub HM} can be useful for improving the dose calculation for adaptive radiation therapy.« less
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Prior image constrained image reconstruction in emerging computed tomography applications
NASA Astrophysics Data System (ADS)
Brunner, Stephen T.
Advances have been made in computed tomography (CT), especially in the past five years, by incorporating prior images into the image reconstruction process. In this dissertation, we investigate prior image constrained image reconstruction in three emerging CT applications: dual-energy CT, multi-energy photon-counting CT, and cone-beam CT in image-guided radiation therapy. First, we investigate the application of Prior Image Constrained Compressed Sensing (PICCS) in dual-energy CT, which has been called "one of the hottest research areas in CT." Phantom and animal studies are conducted using a state-of-the-art 64-slice GE Discovery 750 HD CT scanner to investigate the extent to which PICCS can enable radiation dose reduction in material density and virtual monochromatic imaging. Second, we extend the application of PICCS from dual-energy CT to multi-energy photon-counting CT, which has been called "one of the 12 topics in CT to be critical in the next decade." Numerical simulations are conducted to generate multiple energy bin images for a photon-counting CT acquisition and to investigate the extent to which PICCS can enable radiation dose efficiency improvement. Third, we investigate the performance of a newly proposed prior image constrained scatter correction technique to correct scatter-induced shading artifacts in cone-beam CT, which, when used in image-guided radiation therapy procedures, can assist in patient localization, and potentially, dose verification and adaptive radiation therapy. Phantom studies are conducted using a Varian 2100 EX system with an on-board imager to investigate the extent to which the prior image constrained scatter correction technique can mitigate scatter-induced shading artifacts in cone-beam CT. Results show that these prior image constrained image reconstruction techniques can reduce radiation dose in dual-energy CT by 50% in phantom and animal studies in material density and virtual monochromatic imaging, can lead to radiation dose efficiency improvement in multi-energy photon-counting CT, and can mitigate scatter-induced shading artifacts in cone-beam CT in full-fan and half-fan modes.
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SU-E-T-367: Optimization of DLG Using TG-119 Test Cases and a Weighted Mean Approach
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sintay, B; Vanderstraeten, C; Terrell, J
2014-06-01
Purpose: Optimization of the dosimetric leaf gap (DLG) is an important step in commissioning the Eclipse treatment planning system for sliding window intensity-modulated radiation therapy (SW-IMRT) and RapidArc. Often the values needed for optimal dose delivery differ markedly from those measured at commissioning. We present a method to optimize this value using the AAPM TG-119 test cases. Methods: For SW-IMRT and RapidArc, TG-119 based test plans were created using a water-equivalent phantom. Dose distributions measured on film and ion chamber (IC) readings taken in low-gradient regions within the targets were analyzed separately. Since DLG is a single value per energy,more » SW-IMRT and RapidArc must be considered simultaneously. Plans were recalculated using a linear sweep from 0.02cm (the minimum DLG) to 0.3 cm. The calculated point doses were compared to the measured doses for each plan, and based on these comparisons an optimal DLG value was computed for each plan. TG-119 cases are designed to push the system in various ways, thus, a weighted mean of the DLG was computed where the relative importance of each type of plan was given a score from 0.0 to 1.0. Finally, SW-IMRT and RapidArc are assigned an overall weight based on clinical utilization. Our routine patient-QA (PQA) process was performed as independent validation. Results: For a Varian TrueBeam, the optimized DLG varied with σ = 0.044cm for SW-IMRT and σ = 0.035cm for RapidArc. The difference between the weighted mean SW-IMRT and RapidArc value was 0.038cm. We predicted utilization of 25% SW-IMRT and 75% RapidArc. The resulting DLG was ~1mm different than that found by commissioning and produced an average error of <1% for SW-IMRT and RapidArc PQA test cases separately. Conclusion: The weighted mean method presented is a useful tool for determining an optimal DLG value for commissioning Eclipse.« less
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Alexeev, Timur; Kavanagh, Brian; Miften, Moyed; Altunbas, Cem
2018-02-01
Scattered radiation remains to be a major cause of image quality degradation in Flat Panel Detector (FPD)-based Cone-beam computed tomography (CBCT). We have been investigating a novel two-dimensional antiscatter grid (2D-ASG) concept to reduce scatter intensity, and hence improve CBCT image quality. We present the first CBCT imaging experiments performed with the 2D-ASG prototype, and demonstrate its efficacy in improving CBCT image quality. A 2D-ASG prototype with septa focused to x-ray source was additively manufactured from tungsten and mounted on a Varian TrueBeam CBCT system. CBCT projections of phantoms were acquired with an offset detector geometry using TrueBeam's "developer" mode. To minimize the effect of gantry flex, projections were gain corrected on angle-specific bases. CBCT images were reconstructed using a filtered backprojection algorithm and image quality improvement was quantified by measuring contrast-to-noise ratio (CNR) and CT number accuracy in images acquired with no antiscatter grid (NO-ASG), conventional one dimensional antiscatter grid (1D-ASG), and the 2D-ASG prototype. A significant improvement in contrast resolution was achieved using our 2D-ASG prototype compared to results of 1D-ASG and NO-ASG acquisitions. Compared to NO-ASG and 1D-ASG experiments, the CNR of material inserts improved by as much as 86% and 54% respectively. Using 2D-ASG, CT number underestimation in water equivalent material section of the phantom was reduced by up to 325 HU when compared to NO-ASG and up to 179 HU when compared to 1D-ASG. We successfully performed the first CBCT imaging experiments with a 2D-ASG prototype. 2D-ASG provided significantly higher CT number accuracy, higher CNR, and diminished scatter-induced image artifacts in qualitative evaluations. We strongly believe that utilization of a 2D-ASG may potentially lead to better soft tissue visualization in CBCT and may enable novel clinical applications that require high CT number accuracy. © 2017 American Association of Physicists in Medicine.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Etmektzoglou, A; Mishra, P; Svatos, M
Purpose: To automate creation and delivery of robotic linac trajectories with TrueBeam Developer Mode, an open source spreadsheet-based trajectory generation tool has been developed, tested and made freely available. The computing power inherent in a spreadsheet environment plus additional functions programmed into the tool insulate users from the underlying schema tedium and allow easy calculation, parameterization, graphical visualization, validation and finally automatic generation of Developer Mode XML scripts which are directly loadable on a TrueBeam linac. Methods: The robotic control system platform that allows total coordination of potentially all linac moving axes with beam (continuous, step-and-shoot, or combination thereof) becomesmore » available in TrueBeam Developer Mode. Many complex trajectories are either geometric or can be described in analytical form, making the computational power, graphing and programmability available in a spreadsheet environment an easy and ideal vehicle for automatic trajectory generation. The spreadsheet environment allows also for parameterization of trajectories thus enabling the creation of entire families of trajectories using only a few variables. Standard spreadsheet functionality has been extended for powerful movie-like dynamic graphic visualization of the gantry, table, MLC, room, lasers, 3D observer placement and beam centerline all as a function of MU or time, for analysis of the motions before requiring actual linac time. Results: We used the tool to generate and deliver extended SAD “virtual isocenter” trajectories of various shapes such as parameterized circles and ellipses. We also demonstrated use of the tool in generating linac couch motions that simulate respiratory motion using analytical parameterized functions. Conclusion: The SAGE tool is a valuable resource to experiment with families of complex geometric trajectories for a TrueBeam Linac. It makes Developer Mode more accessible as a vehicle to quickly translate research ideas into machine readable scripts without programming knowledge. As an open source initiative, it also enables researcher collaboration on future developments. I am a full time employee at Varian Medical Systems, Palo Alto, California.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zaks, D; Fletcher, R; Salamon, S
Purpose: To develop an online framework that tracks a patient’s plan from initial simulation to treatment and that helps automate elements of the physics plan checks usually performed in the record and verify (RV) system and treatment planning system. Methods: We have developed PlanTracker, an online plan tracking system that automatically imports new patients tasks and follows it through treatment planning, physics checks, therapy check, and chart rounds. A survey was designed to collect information about the amount of time spent by medical physicists in non-physics related tasks. We then assessed these non-physics tasks for automation. Using these surveys, wemore » directed our PlanTracker software development towards the automation of intra-plan physics review. We then conducted a systematic evaluation of PlanTracker’s accuracy by generating test plans in the RV system software designed to mimic real plans, in order to test its efficacy in catching errors both real and theoretical. Results: PlanTracker has proven to be an effective improvement to the clinical workflow in a radiotherapy clinic. We present data indicating that roughly 1/3 of the physics plan check can be automated, and the workflow optimized, and show the functionality of PlanTracker. When the full system is in clinical use we will present data on improvement of time use in comparison to survey data prior to PlanTracker implementation. Conclusion: We have developed a framework for plan tracking and automatic checks in radiation therapy. We anticipate using PlanTracker as a basis for further development in clinical/research software. We hope that by eliminating the most simple and time consuming checks, medical physicists may be able to spend their time on plan quality and other physics tasks rather than in arithmetic and logic checks. We see this development as part of a broader initiative to advance the clinical/research informatics infrastructure surrounding the radiotherapy clinic. This research project has been financially supported by Varian Medical Systems, Palo Alto, CA, through a Varian MRA.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Otageri, P; Grant, E; Maricle, S
Purpose: To evaluate the effects of MLC modeling after commissioning the Varian TrueBeam LINAC in Pinnacle version 9.2. Methods: Stepand-shoot IMRT QAs were investigated when we observed our measured absolute dose results using ion chamber (Capintec PR-05P) were uncharacteristically low; about 4–5% compared to doses calculated by Pinnacle{sup 3} (Phillips, Madison, WI). This problem was predominant for large and highly modulated head and neck (HN) treatments. Intuitively we knew this had to be related to shortcomings in the MLC modeling in Pinnacle. Using film QA we were able to iteratively adjust the MLC parameters. We confirmed results by re-testing fivemore » failed IMRT QA patients; and ion chamber measurements were verified in Quasar anthropomorphic phantom. Results: After commissioning the LINAC in Pinnacle version 9.2, the MLC transmission for 6X, 10X and 15X were 2.0%, 1.7% and 2.0%, respectively, and additional Interleaf leakage for all three energies was 0.5%. These parameters were obtained from profiles scanned with an Edge detector (Sun Nuclear, Melbourne, FL) during machine commissioning. A Verification testing with radiographic EDR2 film (Kodak, Rochester, NY) measurement was performed by creating a closed MLC leaf pattern and analyzing using RIT software (RIT, Colorado Springs, CO). This reduced MLC transmission for 6X, 10X and 15X to 0.7%, 0.9% and 0.9%, respectively; while increasing additional Interleaf leakage for all three energies to 1.0%. Conclusion: Radiographic film measurements were used to correct MLC transmission values for step and shoot IMRT fields used in Pinnacle version 9.2. After adjusting the MLC parameters to correlate with the film QA, there was still very good agreement between the Pinnacle model and commissioning data. Using the same QA methodology, we were also able to improve the beam models for the Varian C-series linacs, Novalis-Tx, and TrueBeam M-120 linacs.« less
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Onwudili, Jude A; Hajizadeh, Yaghoub; Zainal, Safari; Upton, John; Williams, Paul T
2011-12-15
The seventeen 2378-substituted polychlorinated dibenzo-p-dioxins and dibenzo-p-furans (PCDD/Fs) congeners have been separated and analyzed in sewage sludge and incinerator flyash samples using a CP-Sil 88 column (50 m × 0.25 mm I.D., 0.25 μm film thickness) operating at a maximum oven temperature of 240°C. The column was used on a Varian 450-GC with a Varian 320-MS Triple Quadrupole. Calibration standards were used to determine the transition chemistries of the 2378-substituted PCDD/F congeners in the gas chromatography/mass spectrometry (GC-MS/MS) system. The five-point calibration curve for each of the congeners showed very good linearity with R(2) values greater than 0.999. The recovery of labelled compounds ranged from 50% to 120%. Analytical results from a reference flyash (BCR-490) and a reference sewage sludge (BCR-677) compared very well with the certified values, giving percentage deviations in I-TEQ (international toxic equivalents) of 4.93% and 0.53%, respectively. Results from 'real' flyash samples underscored the level of progress made in the abatement of dioxin emissions from incinerators; the old incinerator flyash contained much higher PCDD/F concentrations than the modern one. In addition, the concentrations profiles of PCDD/Fs in the 'real' sewage sludge from two UK wastewater treatment plants (WWTPs) showed that one contained a total PCDD/Fs content of 314 ng I-TEQ kg(-1), while the other gave a total of 53 ng I-TEQ kg(-1). Over an 18-month period of operation, no significant loss of analytical performance was observed from the low-temperature column. Copyright © 2011 Elsevier B.V. All rights reserved.
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Faught, Austin M; Davidson, Scott E; Popple, Richard; Kry, Stephen F; Etzel, Carol; Ibbott, Geoffrey S; Followill, David S
2017-09-01
The Imaging and Radiation Oncology Core-Houston (IROC-H) Quality Assurance Center (formerly the Radiological Physics Center) has reported varying levels of compliance from their anthropomorphic phantom auditing program. IROC-H studies have suggested that one source of disagreement between institution submitted calculated doses and measurement is the accuracy of the institution's treatment planning system dose calculations and heterogeneity corrections used. In order to audit this step of the radiation therapy treatment process, an independent dose calculation tool is needed. Monte Carlo multiple source models for Varian flattening filter free (FFF) 6 MV and FFF 10 MV therapeutic x-ray beams were commissioned based on central axis depth dose data from a 10 × 10 cm 2 field size and dose profiles for a 40 × 40 cm 2 field size. The models were validated against open-field measurements in a water tank for field sizes ranging from 3 × 3 cm 2 to 40 × 40 cm 2 . The models were then benchmarked against IROC-H's anthropomorphic head and neck phantom and lung phantom measurements. Validation results, assessed with a ±2%/2 mm gamma criterion, showed average agreement of 99.9% and 99.0% for central axis depth dose data for FFF 6 MV and FFF 10 MV models, respectively. Dose profile agreement using the same evaluation technique averaged 97.8% and 97.9% for the respective models. Phantom benchmarking comparisons were evaluated with a ±3%/2 mm gamma criterion, and agreement averaged 90.1% and 90.8% for the respective models. Multiple source models for Varian FFF 6 MV and FFF 10 MV beams have been developed, validated, and benchmarked for inclusion in an independent dose calculation quality assurance tool for use in clinical trial audits. © 2017 American Association of Physicists in Medicine.
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SU-F-T-48: Clinical Implementation of Brachytherapy Planning System for COMS Eye Plaques
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ferreira, C; Islam, M; Ahmad, S
Purpose: To commission the Brachytherapy Planning (BP) system (Varian, Palo Alto, CA) for the Collaborative Ocular Melanoma Study (COMS) eye plaques by evaluating dose differences against original plans from Nucletron Planning System (NPS). Methods: NPS system is the primary planning software for COMS-plaques at our facility; however, Brachytherapy Planning 11.0.47 (Varian Medical Systems) is used for secondary check and for seed placement configurations not originally commissioned. Dose comparisons of BP and NPS plans were performed for prescription of 8500 cGy at 5 mm depth and doses to normal structures: opposite retina, inner sclera, macula, optic disk and lens. Plans weremore » calculated for Iodine-125 seeds (OncoSeeds, Model 6711) using COMS-plaques of 10, 12, 14, 16, 18 and 20 mm diameters. An in-house program based on inverse-square was utilized to calculate point doses for comparison as well. Results: The highest dose difference between BP and NPS was 3.7% for the prescription point for all plaques. Doses for BP were higher than doses reported by NPS for all points. The largest percent differences for apex, opposite retina, inner sclera, macula, optic disk, and lens were 3.2%, 0.9%, 13.5%, 20.5%, 15.7% and 2.2%, respectively. The dose calculated by the in-house program was 1.3% higher at the prescription point, and were as high as 42.1%, for points away from the plaque (i.e. opposite retina) when compared to NPS. Conclusion: Doses to the tumor, lens, retina, and optic nerve are paramount for a successful treatment and vision preservation. Both systems are based on TG-43 calculations and assume water medium tissue homogeneity (ρe=1, water medium). Variations seen may result from the different task group versions and/or mathematical algorithms of the software. BP was commissioned to serve as a backup system and it also enables dose calculation in cases where seeds don’t follow conventional placement configuration.« less
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SU-E-T-344: Validation and Clinical Experience of Eclipse Electron Monte Carlo Algorithm (EMC)
DOE Office of Scientific and Technical Information (OSTI.GOV)
Pokharel, S; Rana, S
2014-06-01
Purpose: The purpose of this study is to validate Eclipse Electron Monte Carlo (Algorithm for routine clinical uses. Methods: The PTW inhomogeneity phantom (T40037) with different combination of heterogeneous slabs has been CT-scanned with Philips Brilliance 16 slice scanner. The phantom contains blocks of Rando Alderson materials mimicking lung, Polystyrene (Tissue), PTFE (Bone) and PMAA. The phantom has 30×30×2.5 cm base plate with 2cm recesses to insert inhomogeneity. The detector systems used in this study are diode, tlds and Gafchromic EBT2 films. The diode and tlds were included in CT scans. The CT sets are transferred to Eclipse treatment planningmore » system. Several plans have been created with Eclipse Monte Carlo (EMC) algorithm 11.0.21. Measurements have been carried out in Varian TrueBeam machine for energy from 6–22mev. Results: The measured and calculated doses agreed very well for tissue like media. The agreement was reasonably okay for the presence of lung inhomogeneity. The point dose agreement was within 3.5% and Gamma passing rate at 3%/3mm was greater than 93% except for 6Mev(85%). The disagreement can reach as high as 10% in the presence of bone inhomogeneity. This is due to eclipse reporting dose to the medium as opposed to the dose to the water as in conventional calculation engines. Conclusion: Care must be taken when using Varian Eclipse EMC algorithm for dose calculation for routine clinical uses. The algorithm dose not report dose to water in which most of the clinical experiences are based on rather it just reports dose to medium directly. In the presence of inhomogeneity such as bone, the dose discrepancy can be as high as 10% or even more depending on the location of normalization point or volume. As Radiation oncology as an empirical science, care must be taken before using EMC reported monitor units for clinical uses.« less
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SU-F-E-07: Web-Based Training for Radiosurgery: Methods and Metrics for Global Reach
DOE Office of Scientific and Technical Information (OSTI.GOV)
Schulz, R; Thomas, E; Popple, R
Purpose: Webinars have become an evolving tool with greater or lesser success in reaching health care providers (HCPs). This study seeks to assess best practices and metrics for success in webinar deployment for optimal global reach. Methods: Webinars have been developed and launched to reach practicing health care providers in the field of radiation oncology and radiosurgery. One such webinar was launched in early February 2016. “Multiple Brain Metastases & Volumetric Modulated Arc Radiosurgery: Refining the Single-Isocenter Technique to Benefit Surgeons and Patients” presented by Drs. Fiveash and Thomas from UAB was submitted to and accredited by the Institute formore » Medical Education as qualifying for CME as well as MDCB for educational credit for dosimetrists, in order to encourage participation. MedicalPhysicsWeb was chosen as the platform to inform attendees regarding the webinar. Further IME accredited the activity for 1 AMA PRA Category 1 credit for physicians & medical physicists. The program was qualified by the ABR in meeting the criteria for self-assessment towards fulfilling MOC requirements. Free SAMs credits were underwritten by an educational grant from Varian Medical Systems. Results: The webinar in question attracted 992 pre-registrants from 66 countries. Outside the US and Canada; 11 were from the Americas; 32 were from Europe; 9 from the Middle East and Africa. Australasia and the Indian subcontinent represented the remaining 14 countries. Pre-registrants included 423 Medical Physicists, 225 Medical Dosimetrists, 24 Radiation Therapists, 66 Radiation Oncologists & other. Conclusion: The effectiveness of CME and SAM-CME programs such as this can be gauged by the high rate of respondents who state an intention to change practice habits, a primary goal of continuing medical education and self-assessment. This webinar succeeded in being the most successful webinar on Medical Physics Web as measured by pre-registration, participation and participation to pre-registration ratio. R.A. Schulz is an employee of Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Chao, M; Yuan, Y; Rosenzweig, K
2015-06-15
Purpose: To develop a novel technique to enhance the image contrast of clinical cone beam CT projections and extract respiratory signals based on anatomical motion using the modified Amsterdam Shroud (AS) method to benefit image guided radiation therapy. Methods: Thoracic cone beam CT projections acquired prior to treatment were preprocessed to increase their contrast for better respiratory signal extraction. Air intensity on raw images was firstly estimated and then applied to correct the projections to generate new attenuation images that were subsequently improved with deeper anatomy feature enhancement through taking logarithm operation, derivative along superior-inferior direction, respectively. All pixels onmore » individual post-processed two dimensional images were horizontally summed to one column and all projections were combined side by side to create an AS image from which patient’s respiratory signal was extracted. The impact of gantry rotation on the breathing signal rendering was also investigated. Ten projection image sets from five lung cancer patients acquired with the Varian Onboard Imager on 21iX Clinac (Varian Medical Systems, Palo Alto, CA) were employed to assess the proposed technique. Results: Application of the air correction on raw projections showed that more than an order of magnitude of contrast enhancement was achievable. The typical contrast on the raw projections is around 0.02 while that on attenuation images could greater than 0.5. Clear and stable breathing signal can be reliably extracted from the new images while the uncorrected projection sets failed to yield clear signals most of the time. Conclusion: Anatomy feature plays a key role in yielding breathing signal from the projection images using the AS technique. The air correction process facilitated the contrast enhancement significantly and attenuation images thus obtained provides a practical solution to obtaining markerless breathing motion tracking.« less
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Technology assessment of multileaf collimation: a North American users survey.
Klein, E E; Tepper, J; Sontag, M; Franklin, M; Ling, C; Kubo, D
1999-06-01
The American Association of Physicists in Medicine (AAPM) initiated an Assessment of Technology Subcommittee (ATS) to help the radiotherapy community evaluate emerging technologies. The ATS decided to first address multileaf collimation (MLC) by means of a North American users survey. The survey attempted to address issues such as MLC utility, efficacy, cost-effectiveness, and customer satisfaction. The survey was designed with 38 questions, with cross-tabulation set up to decipher a particular clinic's perception of MLC. The surveys were coded according to MLC types, which were narrowed to four: Elekta, Siemens, Varian 52-leaf, and Varian 80-leaf. A 40% return rate was desired. A 44% (108 of 250) return was achieved. On an MLC machine, 76.5% of photon patients are being treated with MLC. The main reasons for not using MLC were stair stepping, field size limitation, and physician objection. The most common sites in which MLC is being used are lung, pelvis, and prostate. The least used sites are head & neck and mantle fields. Of the facilities, 31% claimed an increase in number of patients being treated since MLC was installed, and 44% claimed an increase in the number of fields. Though the staffing for block cutting has decreased, therapist staffing has not. However, 91% of the facilities claimed a decreased workload for the therapists, despite the increase in daily treated patients and fields. Of the facilities that justified MLC purchase for more daily patients, 63% are actually treating more patients. Only 26% of the facilities that justified an MLC purchase for intensity-modulated radiotherapy (IMRT) are currently using it for that purpose. The satisfaction rating (1 = low to 5 = high) for department groups averaged 4.0. Therapists ranked MLC as 4.6. Our survey shows that most users have successfully introduced MLC into the clinic as a block replacement. Most have found MLC to be cost-effective and efficient. The use of MLC for IMRT has progressed slower, but users anticipate escalated use.
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Bhushan, Manindra; Yadav, Girigesh; Tripathi, Deepak; Kumar, Lalit; Kishore, Vimal; Dewan, Abhinav; Kumar, Gourav; Wahi, Inderjit Kaur; Gairola, Munish
2018-03-08
To evaluate the feasibility of flattening filter free beam (FFFB) for the treatment of gastric tumors and to review their benefits over 6MV flatten beam (6MV_FFB). Fifteen patients with histologically proven gastric carcinoma were selected. CT scans with slice thickness of 0.3 cm were acquired and planning target volume (PTV) and organ at risk (OAR) were delineated. Plans were made retrospectively for each patient for the prescription dose of 45 Gy/25 fractions to the PTV. Four isocentric plans were compared in the present study on Varian TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA, USA). PTV D98% was 44.41 ± 0.12, 44.38 ± 0.13, 44.59 ± 0.14, and 44.49 ± 0.19 Gy for IMRT 6MV_FFB, IMRT 6MV_FFFB, VMAT 6MV_FFB, and VMAT 6MV_FFFB respectively. 6MV_FFFB beam minimizes the mean heart dose D mean (P = 0.001). VMAT dominates over IMRT when it came to kidney doses V 12Gy (P = 0.02), V 23Gy (P = 0.015), V 28Gy (P = 0.011), and D max (P < 0.01). VMAT has significantly reduced the doses to kidneys. It was analyzed that 6MV_FFFB significantly reduces the dose to normal tissues (P = 0.006 and P = 0.018). VMAT significantly reduces the TMU, which is required to deliver the similar dose by IMRT (P < 0.01). Unflattened beam spares the organs at risk significantly to avoid the chances of secondary malignancies and reduces the intra-fraction motion during treatment due to provision of higher dose rate. Hence, we conclude that 6MV unflattened beam can be used to treat gastric carcinoma.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Giaddui, T; Hardin, M; Keller, J
Purpose: To evaluate patient specific quality assurance (PSQA) for the delivery of volumetric modulated arc therapy (VMAT) by disease site. To compare planning-delivery system (PDS) PSQA pass rates in a dual vendor institution. Methods: PSQA is performed for VMAT plans using a ScandiDos Delta4 phantom. Verification plans are calculated using Varian Eclipse and Elekta Monaco treatment planning systems (TPS) for patients treated using Varian Truebeam and Elekta linear accelerators respectively. Individual arcs are delivered to the Delta4 phantoms and assessed using the gamma index pass criterion(3% Dose Deviation(DD%), 3mm Distance to Agreement(DTA),10% dose threshold and 90% gamma index). Results: Amore » total of 287 VMAT plans and 680 arcs were analyzed. The passing rates for VMAT QA plans were 95% and 98% for head/neck and pelvis/prostate plans respectively, and 100% for chest/abdomen, spine, lung Stereotactic Body Radiotherapy (SBRT) and Stereotactic Radiosurgery(SRS) plans. Average gamma indices were: (99 ± 2) % for pelvis/prostate, chest/abdomen and lung SBRT plans, (97 ± 4) % for head and neck plans and (98 ± 3) % for spine plans. The average DD% and DTA pass rates ranged from 82% to 90% and 98% to 99% respectively for plans in different disease sites. Paired t-test analysis (two tails) indicated no significant differences in the gamma indices between plans delivered using different PDS; the P values were: 0.08, 0.45, and 0.94 for lung SBRT, head/neck and pelvis/prostate plans respectively. The statistical power for comparing PDS in different disease sites with an alpha of 0.05 is 1. Conclusion: The Gamma indices based on 3% DD%, 3 mm DTA and 10% dose threshold for the VMAT QA plans in all disease sites were well above 90%, suggesting the possibility of using a more stringent PSQA criterion. No significant differences were observed in the QA of VMAT plans delivered using different PDS.« less
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SU-G-TeP4-07: Automatic EPID-Based 2D Measurement of MLC Leaf Offset as a Quality Control Tool
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ritter, T; Moran, J; Schultz, B
Purpose: The MLC dosimetric leaf gap (DLG) and transmission are measured parameters which impact the dosimetric accuracy of IMRT and VMAT plans. This investigation aims to develop an efficient and accurate routine constancy check of the physical DLG in two dimensions. Methods: The manufacturer’s recommended DLG measurement method was modified by using 5 fields instead of 11 and by utilizing the Electronic Portal Imaging Device (EPID). Validations were accomplished using an ion chamber (IC) in solid water and a 2D IC array. EPID data was collected for 6 months on multiple TrueBeam linacs using both Millennium and HD MLCs atmore » 5 different clinics in an international consortium. Matlab code was written to automatically analyze the images and calculate the 2D results. Sensitivity was investigated by introducing deliberate leaf position errors. MLC calibration and initialization history was recorded to allow quantification of their impact. Results were analyzed using statistical process control (SPC). Results: The EPID method took approximately 5 minutes. Due to detector response, the EPID measured DLG and transmission differed from the IC values but were reproducible and consistent with changes measured using the ICs. For the Millennium MLC, the EPID measured DLG and transmission were both consistently lower than IC results. The EPID method was implemented as leaf offset and transmission constancy tests (LOC and TC). Based on 6 months of measurements, the initial leaf-specific action thresholds for changes from baseline were set to 0.1 mm. Upper and lower control limits for variation were developed for each machine. Conclusion: Leaf offset and transmission constancy tests were implemented on Varian HD and Millennium MLCs using an EPID and found to be efficient and accurate. The test is effective for monitoring MLC performance using dynamic delivery and performing process control on the DLG in 2D, thus enhancing dosimetric accuracy. This work was supported by a grant from Varian Medical Systems.« less
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TH-AB-BRB-04: Quality Assurance for Advanced Digital Linac Implementations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yu, V.
2016-06-15
Current state-of-the art digital C-arm medical linear accelerators are capable of delivering radiation treatments with high level of automation, which affords coordinated motions of gantry, couch, and multileaf collimator (MLC) with dose rate modulations. The new machine capacity has shown the potential to bring substantially improved radiation dosimetry and/or delivery efficiency to many challenging diseases. Combining an integrated beam orientation optimization algorithm with automated machine navigation, markedly improved dose conformity has been achieved using 4ρ therapy. Trajectory modulated radiation therapy (TMAT) can be used to deliver highly conformal dose to partial breast or to carve complex dose distribution for therapymore » involving extended volumes such as total marrow and total lymph node treatment. Dynamic electron arc radiotherapy (DEAR) not only overcomes the deficiencies of conventional electron therapy in dose conformity and homogeneity but also achieves so without patient-specific shields. The combination of MLC and couch tracking provides improved motion management of thoracic and abdominal tumors. A substantial body of work has been done in these technological advances for clinical translation. The proposed symposium will provide a timely review of these exciting opportunities. Learning Objectives: Recognize the potential of using digitally controlled linacs for clinically significant improvements in delivered dose distributions for various treatment sites. Identify existing approaches to treatment planning, optimization and delivery for treatment techniques utilizing the advanced functions of digital linacs and venues for further development and improvement. Understand methods for testing and validating delivery system performance. Identify tools available on current delivery systems for implementation and control for such treatments. Obtain the update in clinical applications, trials and regulatory approval. K. Sheng, NIH U19AI067769, NIH R43CA183390, NIH R01CA188300, Varian Medical Systems V. Yu, Varian Medical Systems, AAPM Summer Undergraduate Fellowship, NSF graduate fellowship S. Nill, Elekta AB. Cancer Research UK under Programme C33589/A19727, NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research.« less
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TH-AB-BRB-00: Research Opportunities with Digital Linear Accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
NONE
2016-06-15
Current state-of-the art digital C-arm medical linear accelerators are capable of delivering radiation treatments with high level of automation, which affords coordinated motions of gantry, couch, and multileaf collimator (MLC) with dose rate modulations. The new machine capacity has shown the potential to bring substantially improved radiation dosimetry and/or delivery efficiency to many challenging diseases. Combining an integrated beam orientation optimization algorithm with automated machine navigation, markedly improved dose conformity has been achieved using 4ρ therapy. Trajectory modulated radiation therapy (TMAT) can be used to deliver highly conformal dose to partial breast or to carve complex dose distribution for therapymore » involving extended volumes such as total marrow and total lymph node treatment. Dynamic electron arc radiotherapy (DEAR) not only overcomes the deficiencies of conventional electron therapy in dose conformity and homogeneity but also achieves so without patient-specific shields. The combination of MLC and couch tracking provides improved motion management of thoracic and abdominal tumors. A substantial body of work has been done in these technological advances for clinical translation. The proposed symposium will provide a timely review of these exciting opportunities. Learning Objectives: Recognize the potential of using digitally controlled linacs for clinically significant improvements in delivered dose distributions for various treatment sites. Identify existing approaches to treatment planning, optimization and delivery for treatment techniques utilizing the advanced functions of digital linacs and venues for further development and improvement. Understand methods for testing and validating delivery system performance. Identify tools available on current delivery systems for implementation and control for such treatments. Obtain the update in clinical applications, trials and regulatory approval. K. Sheng, NIH U19AI067769, NIH R43CA183390, NIH R01CA188300, Varian Medical Systems V. Yu, Varian Medical Systems, AAPM Summer Undergraduate Fellowship, NSF graduate fellowship S. Nill, Elekta AB. Cancer Research UK under Programme C33589/A19727, NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Chiu, T; Kearney, V; Liu, H
Purpose: Dynamic tumor tracking or motion compensation techniques have proposed to modify beam delivery following lung tumor motion on the flight. Conventional treatment plan QA could be performed in advance since every delivery may be different. Markerless lung tumor tracking using beams eye view EPID images provides a best treatment evaluation mechanism. The purpose of this study is to improve the accuracy of the online markerless lung tumor motion tracking method. Methods: The lung tumor could be located on every frame of MV images during radiation therapy treatment by comparing with corresponding digitally reconstructed radiograph (DRR). A kV-MV CT correspondingmore » curve is applied on planning kV CT to generate MV CT images for patients in order to enhance the similarity between DRRs and MV treatment images. This kV-MV CT corresponding curve was obtained by scanning a same CT electron density phantom by a kV CT scanner and MV scanner (Tomotherapy) or MV CBCT. Two sets of MV DRRs were then generated for tumor and anatomy without tumor as the references to tracking the tumor on beams eye view EPID images. Results: Phantom studies were performed on a Varian TrueBeam linac. MV treatment images were acquired continuously during each treatment beam delivery at 12 gantry angles by iTools. Markerless tumor tracking was applied with DRRs generated from simulated MVCT. Tumors were tracked on every frame of images and compared with expected positions based on programed phantom motion. It was found that the average tracking error were 2.3 mm. Conclusion: This algorithm is capable of detecting lung tumors at complicated environment without implanting markers. It should be noted that the CT data has a slice thickness of 3 mm. This shows the statistical accuracy is better than the spatial accuracy. This project has been supported by a Varian Research Grant.« less
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Wang, L; Xing, L; Le, Q
2012-06-01
In H&N cancer patients, the development of oral mucositis is related closely to the radiation dose to the oral cavity. It is generally presumed that the existence of metallic dental implants makes it worse due to the scattering effect of the metal. This study investigates the effects of the dental implants on radiation doses to PTV, tongue mucosa, and other structures for IMRT H&N cancer patients by Monte Carlo (MC) dose calculations. Two H&N cancer patients who have dental implant and are treated by IMRT technique are selected for the purpose. The BEAMnrc/DOSXYZnrc MC codes are employed for the CT-image based dose calculations. The radiation sources are the validated Varian phase-space files for 6MV linac beams. The CT image artifacts caused by the dental fillings are replaced by tissue material. Two sets of MC calculations for each patient are performed at a calculation statistics of 1%: one treats all dental implants as bones, the other substitutes the implants by metal of either titanium or gold with correct density. Doses in PTV and various tissue structures are compared for the two scenarios. With titanium implant, there is no significant difference in doses to PTV and tongue mucosa from that when treating implant as bone. With gold implant, the mean dose to PTV is slightly lowered by 1%; the mean dose to tongue mucosa is reduced by less than 0.5%, although the maximum dose is increased by 5%. The scattering dose from titanium implants is not of concern for H&N patients irradiated by 6MV IMRT beams. For gold implants, the scattering dose to tongue mucosa is not as severe as presumed; and the dose to PTV could be slightly compromised due to the attenuation effect of the metal. This work was supported in part by Varian Medical Systems. © 2012 American Association of Physicists in Medicine.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hancock, S; Clements, C; Hyer, D
2016-06-15
Purpose: To develop and demonstrate application of a method that characterizes deviation of linac x-ray beams from the centroid of the volumetric radiation isocenter as a function of gantry, collimator, and table variables. Methods: A set of Winston-Lutz ball-bearing images was used to determine the gantry radiation isocenter as the midrange of deviation values resulting from gantry and collimator rotation. Also determined were displacement of table axis from gantry isocenter and recommended table axis adjustment. The method, previously reported, has been extended to include the effect of collimator walkout by obtaining measurements with 0 and 180 degree collimator rotation formore » each gantry angle. Twelve images were used to characterize the volumetric isocenter for the full range of available gantry, collimator, and table rotations. Results: Three Varian True Beam, two Elekta Infinity and four Versa HD linacs at five institutions were tested using identical methodology. Varian linacs exhibited substantially less deviation due to head sag than Elekta linacs (0.4 mm vs. 1.2 mm on average). One linac from each manufacturer had additional isocenter deviation of 0.3 to 0.4 mm due to jaw instability with gantry and collimator rotation. For all linacs, the achievable isocenter tolerance was dependent on adjustment of collimator position offset, transverse position steering, and alignment of the table axis with gantry isocenter, facilitated by these test results. The pattern and magnitude of table axis wobble vs. table angle was reproducible and unique to each machine. Conclusion: This new method provides a comprehensive set of isocenter deviation values including all variables. It effectively facilitates minimization of deviation between beam center and target (ball-bearing) position. This method was used to quantify the effect of jaw instability on isocenter deviation and to identify the offending jaw. The test is suitable for incorporation into a routine machine QA program. Software development was performed by Radiological Imaging Technology, Inc.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yao, R; Chisela, W
2015-06-15
Purpose: To investigate the use of EPID transit dosimetry for monitoring daily dose variations in radiation treatment delivery. Methods: A patient with head and neck cancer treated using nine field IMRT beams was used in this study. The prescription was 45 Gy in 25 fractions. A KV CBCT was acquired before each treatment on a Varian NTX linear accelerator. Integrated images using MV EPID were acquired for each treatment beam. Planning CT images, treatment plan, and daily integrated images were imported into a commercial QA software Dosimetry Check (v4r4 Math Resolutions, LLC, Columbia, MD) to calculate 3D dose of themore » day assuming 25 fractions treatment. Planning CT images were deformed and registered to each daily CBCT using Varian SmartAdapt (v11.MR2). ROIs were then propagated from planning CT to daily CBCT. The correlation between maximum, average dose of ROIs and ROI volume, center of mass shift, Dice Similarity Coefficient (DSC) were investigated. Results: Not all parameters investigated showed strong correlations. For PTV and CTV, the average dose has inverse correlation with their volume change (correlation coefficient −0.52, −0.50, respectively) and DSC (−0.59, −0.59, respectively). The average dose of right parotid has correlation with its volume change (0.56). The maximum dose of spinal cord has correlation with the center of mass superior-inferior shift (0.52) and inverse correlation with the center of mass anterior-posterior shift (−0.73). Conclusion: Transit dosimetry using EPID images collected during treatment delivery offers great potential to monitor daily dose variations due to patient anatomy change, motion, and setup errors in radiation treatment delivery. It can provide a patient-specific QA tool valuable for adaptive radiation therapy. Further work is needed to validate the technique.« less
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A novel technique for VMAT QA with EPID in cine mode on a Varian TrueBeam linac
NASA Astrophysics Data System (ADS)
Liu, Bo; Adamson, Justus; Rodrigues, Anna; Zhou, Fugen; Yin, Fang-fang; Wu, Qiuwen
2013-10-01
Volumetric modulated arc therapy (VMAT) is a relatively new treatment modality for dynamic photon radiation therapy. Pre-treatment quality assurance (QA) is necessary and many efforts have been made to apply electronic portal imaging device (EPID)-based IMRT QA methods to VMAT. It is important to verify the gantry rotation speed during delivery as this is a new variable that is also modulated in VMAT. In this paper, we present a new technique to perform VMAT QA using an EPID. The method utilizes EPID cine mode and was tested on Varian TrueBeam in research mode. The cine images were acquired during delivery and converted to dose matrices after profile correction and dose calibration. A sub-arc corresponding to each cine image was extracted from the original plan and its portal image prediction was calculated. Several analyses were performed including 3D γ analysis (2D images + gantry angle axis), 2D γ analysis, and other statistical analyses. The method was applied to 21 VMAT photon plans of 3 photon energies. The accuracy of the cine image information was investigated. Furthermore, this method's sensitivity to machine delivery errors was studied. The pass rate (92.8 ± 1.4%) for 3D γ analysis was comparable to those from Delta4 system (99.9 ± 0.1%) under similar criteria (3%, 3 mm, 5% threshold and 2° angle to agreement) at 6 MV. The recorded gantry angle and start/stop MUs were found to have sufficient accuracy for clinical QA. Machine delivery errors can be detected through combined analyses of 3D γ, gantry angle, and percentage dose difference. In summary, we have developed and validated a QA technique that can simultaneously verify the gantry angle and delivered MLC fluence for VMAT treatment.This technique is efficient and its accuracy is comparable to other QA methods.
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SU-E-T-257: Output Constancy: Reducing Measurement Variations in a Large Practice Group
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hedrick, K; Fitzgerald, T; Miller, R
2014-06-01
Purpose: To standardize output constancy check procedures in a large medical physics practice group covering multiple sites, in order to identify and reduce small systematic errors caused by differences in equipment and the procedures of multiple physicists. Methods: A standardized machine output constancy check for both photons and electrons was instituted within the practice group in 2010. After conducting annual TG-51 measurements in water and adjusting the linac to deliver 1.00 cGy/MU at Dmax, an acrylic phantom (comparable at all sites) and PTW farmer ion chamber are used to obtain monthly output constancy reference readings. From the collected charge reading,more » measurements of air pressure and temperature, and chamber Ndw and Pelec, a value we call the Kacrylic factor is determined, relating the chamber reading in acrylic to the dose in water with standard set-up conditions. This procedure easily allows for multiple equipment combinations to be used at any site. The Kacrylic factors and output results from all sites and machines are logged monthly in a central database and used to monitor trends in calibration and output. Results: The practice group consists of 19 sites, currently with 34 Varian and 8 Elekta linacs (24 Varian and 5 Elekta linacs in 2010). Over the past three years, the standard deviation of Kacrylic factors measured on all machines decreased by 20% for photons and high energy electrons as systematic errors were found and reduced. Low energy electrons showed very little change in the distribution of Kacrylic values. Small errors in linac beam data were found by investigating outlier Kacrylic values. Conclusion: While the use of acrylic phantoms introduces an additional source of error through small differences in depth and effective depth, the new standardized procedure eliminates potential sources of error from using many different phantoms and results in more consistent output constancy measurements.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jin, L; Price, R; Wang, L
Purpose: The CyberKnife (CK) M6 Series introduced a mulitleaf collimator (MLC) beam for extending its capability to the conventional radiotherapy. This work is to investigate delivery efficiency of this system as compared to a standard Varian linac when treating hepatic lesions. Methods: Nine previously treated patients were divided into three groups with three patients in each. Group one: fractionated radiotherapy; Group two: SBRT-like treatments and Group three: fractionated radiotherapy targeting two PTVs. The clinically used plans were generated with the Eclipse treatment planning system (TPS). We re-planned these cases using a Mulitplan (MP) TPS for the CK M6 and normalizedmore » to the same PTV dose coverage. CK factors (CF) (defined as modulation scaling factor in this work), number of nodes (NN), number of MLC segments (NS) and beam delivery time (BT) with an estimated image interval of 60 seconds, were used for evaluation of delivery efficiency. Results: Generated plans from the MP and Eclipse TPS demonstrated the similar quality in terms of PTV confomality index, minimum and maximum PTV doses, and doses received by critical structures. Group one: CF ranged from 8.1 to 8.7, NN from 30 to 40, NS from 120 to 155 and BT from 20 to 23 minutes; group two: CF from 4.7 to 8.5, NN from 15 to 19, NS from 82 to 141 and BT from 18 to 24 minutes; and group three: CF from 7.9 to 10, NN from 47 to 49, NS from 110 to 113 and BT from 20 to 22 minutes. Conclusions: Delivery time is longer for the CK M6 than for the Varian linac (7.8 to 13.7 minutes). Further investigation will be necessary to determine if a PTV reduction from the tracking feature will shorten the delivery time without decreasing plan quality.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Fu,; Chen, Y; Yu, Y
Purpose: Orthogonal kV image pairs are used for target localization when fiducial markers are implanted. CBCT is used to verify cone SRS setup. Therefore it is necessary to evaluate the isocenter congruence between radiation fields and kV imaging center. This study used a simple method to evaluate the isocenter congruence, and compared the results for MLC and cone fields on two different Linacs. Methods: Varian OBI block was attached on the couch. It has a central 1mm BB with markers on three surfaces to align with laser. KV and MV images were taken at four cardinal angles. A 3x3cm2 MLCmore » field and a 20mm cone field were irradiated respectively. On each kV image, the distance from BB center to the kV graticule center were measured. On the MV image of MLC field, the center of radiation field was determined manually, while for cone field, the Varian AM maintenance software was used to analyze the distance between BB and radiation field. The subtraction of the two distances gives the discrepancy between kV and radiation centers. Each procedure was repeated on five days at Trilogy and TrueBeam respectively. Results: The maximum discrepancy was found in the longitudinal direction at 180° gantry angel. It was 1.5±0.1mm for Trilogy and 0.6±0.1mm for TrueBeam. For Trilogy, although radiation center wobbled only 0.7mm and image center wobbled 0.8mm, they wobbled to the opposite direction. KV Pair using gantry 180° should be avoided in this case. Cone vs. kV isocenter has less discrepancy than MLC for Trilogy. Conclusion: Radiation isocenter of MLC and cone field is different, so is between Trilogy and TrueBeam. The method is simple and reproducible to check kV and radiation isocenter congruence.« less
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MO-FG-CAMPUS-TeP3-03: Calculation of Proton Pencil Beam Properties with Full Beamline Model in TOPAS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wulff, J; Abel, E
2016-06-15
Purpose: Introducing Monte Carlo based dose calculation algorithms into proton therapy planning systems (TPS) leads to improved accuracy. However accurate modelling of the proton pencil beam impinging the patient is necessary. Current approaches rely on measurement-driven reconstruction of phase-space and spectrum properties, typically constrained to analytical model functions. In this study a detailed Monte Carlo model of the complete cyclotron-based delivery system was created with the aim of providing more representative beam properties at treatment position. Methods: A model of the Varian Probeam proton system from the cyclotron exit to isocenter was constructed in the TOPAS Monte Carlo framework. Themore » beam evolution through apertures and magnetic elements was validated using Transport/Turtle calculations and additionally against measurements from the Probeam™ system at Scripps Proton Therapy Center (SPTC) in San Diego, CA. A voxelized water phantom at isocenter allowed for comparison of the dose-depth curve from the Probeam model with that of a corresponding Gaussian beam over the entire energy range (70–240 MeV). Measurements of relative beam fluence cross-profiles and depth-dose curves at and around isocenter were also compared to the MC results. Results: The simulated TOPAS beam envelope was found to agree with both the Transport/Turtle and measurements to within 5% for most of the beamline. The MC predicted energy spectrum at isocenter was found to deviate increasingly from Gaussian at energies below 160 MeV. The corresponding effects on the depth dose curve agreed well with measurements. Conclusion: Given the flexibility of TOPAS and available details of the delivery system, an accurate characterization of a proton pencil beam at isocenter is possible. Incorporation of the MC derived properties of the proton pencil beam can eliminate analytical approximations and ultimately increase treatment plan accuracy and quality. Both authors are employees of Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Kim, S; Alaei, P
2015-06-15
Purpose: To implement full/half bowtie filter models in a commercial treatment planning system (TPS) to calculate kilovoltage (kV) x-ray imaging dose of Varian On-Board Imager (OBI) cone beam CT (CBCT) system. Methods: Full/half bowtie filters of Varian OBI were created as compensator models in Pinnacle TPS (version 9.6) using Matlab software (version 2011a). The profiles of both bowtie filters were acquired from the manufacturer, imported into the Matlab system and hard coded in binary file format. A Pinnacle script was written to import each bowtie filter data into a Pinnacle treatment plan as a compensator. A kV x-ray beam modelmore » without including the compensator model was commissioned per each bowtie filter setting based on percent depth dose and lateral profile data acquired from Monte Carlo simulations. To validate the bowtie filter models, a rectangular water phantom was generated in the planning system and an anterior/posterior beam with each bowtie filter was created. Using the Pinnacle script, each bowtie filter compensator was added to the treatment plan. Lateral profile at the depth of 3cm and percent depth dose were measured using an ion chamber and compared with the data extracted from the treatment plans. Results: The kV x-ray beams for both full and half bowtie filter have been modeled in a commercial TPS. The difference of lateral and depth dose profiles between dose calculations and ion chamber measurements were within 6%. Conclusion: Both full/half bowtie filter models provide reasonable results in kV x-ray dose calculations in the water phantom. This study demonstrates the possibility of using a model-based treatment planning system to calculate the kV imaging dose for both full and half bowtie filter modes. Further study is to be performed to evaluate the models in clinical situations.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wu, L; Huang, B; Rowedder, B
Purpose: The Smart leaf motion calculator (SLMC) in Eclipse treatment planning system is an advanced fluence delivery modeling algorithm as it takes into account fine MLC features including inter-leaf leakage, rounded leaf tips, non-uniform leaf thickness, and the spindle cavity etc. In this study, SLMC and traditional Varian LMC (VLMC) algorithms were investigated, for the first time, in dosimetric characteristics and delivery accuracy of sliding window (SW) IMRT. Methods: The SW IMRT plans of 51 cancer cases were included to evaluate dosimetric characteristics and dose delivery accuracy from leaf motion calculated by SLMC and VLMC, respectively. All plans were deliveredmore » using a Varian TrueBeam Linac. The DVH and MUs of the plans were analyzed. Three patient specific QA tools - independent dose calculation software IMSure, Delta4 phantom, and EPID portal dosimetry were also used to measure the delivered dose distribution. Results: Significant differences in the MUs were observed between the two LMCs (p≤0.001).Gamma analysis shows an excellent agreement between the planned dose distribution calculated by both LMC algorithms and delivered dose distribution measured by three QA tools in all plans at 3%/3 mm, leading to a mean pass rate exceeding 97%. The mean fraction of pixels with gamma < 1 of SLMC is slightly lower than that of VLMC in the IMSure and Delta4 results, but higher in portal dosimetry (the highest spatial resolution), especially in complex cases such as nasopharynx. Conclusion: The study suggests that the two LMCs generates the similar target coverage and sparing patterns of critical structures. However, SLMC is modestly more accurate than VLMC in modeling advanced MLC features, which may lead to a more accurate dose delivery in SW IMRT. Current clinical QA tools might not be specific enough to differentiate the dosimetric discrepancies at the millimeter level calculated by these two LMC algorithms. NIH/NIGMS grant U54 GM104944, Lincy Endowed Assistant Professorship.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hasson, B; Young, M; Workie, D
2014-06-01
Purpose: To develop and implement a Deep Inhalation Breath Hold program (DIBH) for treatment of patients with Left-sided breast cancer in a community hospital. Methods: All patients with left sided breast cancer underwent a screening free breathing CT. Evaluation of the conventional tangent treatment fields and the heart was conducted. If the heart would not be excluded using tangents, the patient then received DIBH breathe coaching. The patients returned for a 4D CT simulation. The patients breathing cycle was monitored using the Varian Real-Time position ManagementTM (RPM) system to assess duration of DIBH, amplitude, phase and recovery time to normalmore » breathing. Then a DIBH CT was obtained at the desired amplitude. Duplicate plans were developed for both free breathing and DIBH on the Eclipse planning system and comparison DVH's were created. The plan that provided the prescribed treatment coverage and the least doses to the OAR (heart, Lt. Lung) was determined. Those patients selected to receive treatment with DIBH were set up for treatment, and breathing was monitored using the RPM system. Practice trials were used to confirm that the amplitude, phase and recovery were consistent with findings from simulation. Results: 10 patients have been treated using the DIBH procedure in our clinic. The DIBH patients had an average increase of 80% lung volume on DIBH, decreased lung volume receiving 50% of the dose, and decreases in the V20 dose. Significant reduction in the maximum and mean dose to the heart, as well as the dose to 1CC of the volume for the DIBH plans. Conclusion: Using the RPM system already available in the clinic, staff training, and patient coaching a simple DIBH program was setup. The use of DIBH has shown promise in reducing doses to the critical organs while maintaining PTV coverage for left sided breast treatments.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Foy, J; Marsh, R; Owen, D
2015-06-15
Purpose: Creating high quality SBRT treatment plans for the spine is often tedious and time consuming. In addition, the quality of treatment plans can vary greatly between treatment facilities due to inconsistencies in planning methods. This study investigates the performance of knowledge-based planning (KBP) for spine SBRT. Methods: Treatment plans were created for 28 spine SBRT patients. Each case was planned to meet strict dose objectives and guidelines. After physician and physicist approval, the plans were added to a custom model in a KBP system (RapidPlan, Varian Eclipse v13.5). The model was then trained to be able to predict estimatedmore » DVHs and provide starting objective functions for future patients based on both generated and manual objectives. To validate the model, ten additional spine SBRT cases were planned manually as well as using the model objectives. Plans were compared based on planning time and quality (ability to meet the plan objectives, including dose metrics and conformity). Results: The average dose to the spinal cord and the cord PRV differed between the validation and control plans by <0.25% demonstrating iso-toxicity. Six out of 10 validation plans met all dose objectives without the need for modifications, and overall, target dose coverage was increased by about 4.8%. If the validation plans did not meet the dose requirements initially, only 1–2 iterations of modifying the planning parameters were required before an acceptable plan was achieved. While manually created plans usually required 30 minutes to 3 hours to create, KBP can be used to create similar quality plans in 15–20 minutes. Conclusion: KBP for spinal tumors has shown to greatly decrease the amount of time required to achieve high quality treatment plans with minimal human intervention and could feasibly be used to standardize plan quality between institutions. Supported by Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Willett, A; Gilmore, M; Rowbottom, C
2016-06-15
Purpose: The purpose of this work was to see if the EPID is a viable alternative to other QA devices for routine FFF QA and plan dose measurements. Methods: Sensitivity measurements were made to assess response to small changes in field size and beam steering. QA plans were created where field size was varied from baseline values (5–5.5cm, 20–20.5cm). Beam steering was adjusted by altering values in service mode (Symmetry 0–3%). Plans were measured using the Varian portal imager (aS1200 DMI panel), QA3 (Sun Nuclear), and Starcheck Maxi (PTW). FFF beam parameters as stated in Fogliata et al were calculated.more » Constancy measurements were taken using all 3 QC devices to measure a MLC defined 20×20cm field. Two clinical SABR patient plans were measured on a Varian Edge linac, using the Portal Dosimetry module in ARIA, and results compared with analysis made using Delta4 (ScandiDos). Results: The EPID and the Starcheck performed better at detecting clinically relevant changes in field size with the QA3 performing better when detecting similar changes in beam symmetry. Consistency measurements with the EPID and Starcheck were equivalent, with comparable standard deviations. Clinical plan measurements on the EPID compared well with Delta4 results at 3%/1mm. Conclusion: Our results show that for FFF QA measurements such as field size and symmetry, using the EPID is a viable alternative to other QA devices. The EPID could potentially be used for QC measurements with a focus on geometric accuracy, such as MLC positional QA, due to its high resolution compared to other QA devices (EPID 0.34mm, Starcheck 3mm, QA3 5mm). Good agreement between Delta4 and portal dosimetry also indicated the EPID may be a suitable alternative for measurement of clinical plans.« less
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SU-F-T-240: EPID-Based Quality Assurance for Dosimetric Credentialing
DOE Office of Scientific and Technical Information (OSTI.GOV)
Miri, N; Lehmann, J; Vial, P
Purpose: We propose a novel dosimetric audit method for clinical trials using EPID measurements at each center and a standardized EPID to dose conversion algorithm. The aim of this work is to investigate the applicability of the EPID method to different linear accelerator, EPID and treatment planning system (TPS) combinations. Methods: Combination of delivery and planning systems were three Varian linacs including one Pinnacle and two Eclipse TPS and, two ELEKTA linacs including one Pinnacle and one Monaco TPS. All Varian linacs had the same EPID structure and similarly for the ELEKTA linacs. Initially, dose response of the EPIDs wasmore » investigated by acquiring integrated pixel value (IPV) of the central area of 10 cm2 images versus MUs, 5-400 MU. Then, the EPID to dose conversion was investigated for different system combinations. Square field size images, 2, 3, 4, 6, 10, 15, 20, 25 cm2 acquired by all systems were converted to dose at isocenter of a virtual flat phantom then the dose was compared to the corresponding TPS dose. Results: All EPIDs showed a relatively linear behavior versus MU except at low MUs which showed irregularities probably due to initial inaccuracies of irradiation. Furthermore, for all the EPID models, the model predicted TPS dose with a mean dose difference percentage of 1.3. However the model showed a few inaccuracies for ELEKTA EPID images at field sizes larger than 20 cm2. Conclusion: The EPIDs demonstrated similar behavior versus MU and the model was relatively accurate for all the systems. Therefore, the model could be employed as a global dosimetric method to audit clinical trials. Funding has been provided from Department of Radiation Oncology, TROG Cancer Research and the University of Newcastle. Narges Miri is a recipient of a University of Newcastle postgraduate scholarship.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Cui, G; Trakul, N; Chang, E
Purpose: To evaluate the reproducibility of target position using moderate voluntary breath-hold during liver stereotactic ablative radiotherapy (SABR). Methods: Two patients who underwent liver SABR on a Varian TrueBeam STx linac were used for this study. Fiducial markers were placed in and around the target in the liver as surrogates for the target position and motion. GTVs were contoured by assessing tumor extent on contrast enhanced CT. The PTV was created from the GTV by adding 2 mm margins to account for the residual motion during breath-holds. A portable biofeedback system was used to facilitate the breath-hold to a reproduciblemore » position. The Varian RPM system was used for gating the linac. Proceeding each treatment, orthogonal kV pairs were taken, and alignment to nearby bony anatomy was performed. Then the breath-hold CBCT was acquired to align the fiducial markers. On-line fluoroscopy was used to fine-tune the breath-hold gating thresholds to correlate with the positions of the fiducial markers. The inter-fraction reproducibility of the target was evaluated by the offsets of the daily breath-hold CBCTs from the paired kV matches as a direct measure of the target position relative to the bony anatomy. The intra-fraction reproducibility of the target position was assessed by the gated window of the RPM marker block for each fraction. Results: The absolute mean offsets between the CBCT and paired kV matches in the vertical, longitudinal, and lateral directions were 0.06 cm, 0.10 cm, and 0.06 cm for patient 1, and 0.37 cm, 0.62 cm, and 0.09 cm for patient 2. The gated window of the RPM marker block for the breath-hold for each fraction was within 0.63 ± 0.16 cm and 0.59 ± 0.12 cm for patients 1 and 2, respectively. Conclusion: Moderate voluntary breath-hold showed good inter- and intra-fraction reproducibility of target position during liver SABR.« less
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Comparative analysis of respiratory motion tracking using Microsoft Kinect v2 sensor.
Silverstein, Evan; Snyder, Michael
2018-05-01
To present and evaluate a straightforward implementation of a marker-less, respiratory motion-tracking process utilizing Kinect v2 camera as a gating tool during 4DCT or during radiotherapy treatments. Utilizing the depth sensor on the Kinect as well as author written C# code, respiratory motion of a subject was tracked by recording depth values obtained at user selected points on the subject, with each point representing one pixel on the depth image. As a patient breathes, specific anatomical points on the chest/abdomen will move slightly within the depth image across pixels. By tracking how depth values change for a specific pixel, instead of how the anatomical point moves throughout the image, a respiratory trace can be obtained based on changing depth values of the selected pixel. Tracking these values was implemented via marker-less setup. Varian's RPM system and the Anzai belt system were used in tandem with the Kinect to compare respiratory traces obtained by each using two different subjects. Analysis of the depth information from the Kinect for purposes of phase- and amplitude-based binning correlated well with the RPM and Anzai systems. Interquartile Range (IQR) values were obtained comparing times correlated with specific amplitude and phase percentages against each product. The IQR time spans indicated the Kinect would measure specific percentage values within 0.077 s for Subject 1 and 0.164 s for Subject 2 when compared to values obtained with RPM or Anzai. For 4DCT scans, these times correlate to less than 1 mm of couch movement and would create an offset of 1/2 an acquired slice. By tracking depth values of user selected pixels within the depth image, rather than tracking specific anatomical locations, respiratory motion can be tracked and visualized utilizing the Kinect with results comparable to that of the Varian RPM and Anzai belt. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Kumar, Syam; Aparna
2015-06-15
Purpose: To study the dosimetric properties of Enhanced Dynamic Wedge (EDW) using PTW Seven29 ion chamber array Methods: PTW Seven29 ion chamber array and Solid Water phantoms for different depths were used for the study. The study was carried out in Varian Clinac ix with photon energies, 6MV & 15MV. Primarily the solid water phantoms with the 2D array were scanned using a CT scanner (GE Optima 580) at different depths. These scanned images were used for EDW planning in an Eclipse treatment planning system (version 10). Planning was done for different wedge angles and for different depths for 6MVmore » & 15MV. A dose of 100 CGy was delivered in each cases. For each delivery, calculated the Monitoring Unit (MU) required. Same set-up was created before delivering the plans in Varian Clinac-ix. For each clinically relevant depth and for different wedge angles, the same MU was delivered as calculated. Different wedged dose distributions where reconstructed from the measured 2D array data using the in-house developed excel program. Results: It is observed that the shoulder like region in the profile which reduces as depth increases. For the same depth and energy, the percentage difference between planned and measured dose is lesser than 3%. For smaller wedge angles, the percentage difference is found to be greater than 3% for the largest wedge angle. Standard deviation between measured doses at shoulder region for planned and measured profiles is 0.08 and 0.02 respectively. Standard deviations between planned and measured wedge factors for different depths (2.5cm, 5cm, 10cm, and 15cm) are (0.0021, 0.0007, 0.0050, 0.0001) for 6MV and (0.0024, 0.0191, 0.0013, 0.0005) for 15MV respectively. Conclusion: The 2D Seven29 ion chamber array is a good tool for the Enhanced Dynamic Wedge (EDW) dosimetry.« less
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TH-EF-BRB-02: Feasibility of Optimization for Dynamic Trajectory Radiotherapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fix, MK; Frei, D; Volken, W
2016-06-15
Purpose: Over the last years, volumetric modulated arc therapy (VMAT) has been widely introduced into clinical routine using a coplanar delivery technique. However, VMAT might be improved by including dynamic couch and collimator rotations, leading to dynamic trajectory radiotherapy (DTRT). In this work the feasibility and the potential benefit of DTRT was investigated. Methods: A general framework for the optimization was developed using the Eclipse Scripting Research Application Programming Interface (ESRAPI). Based on contoured target and organs at risk (OARs), the structures are extracted using the ESRAPI. Sampling potential beam directions, regularly distributed on a sphere using a Fibanocci-lattice, themore » fractional volume-overlap of each OAR and the target is determined and used to establish dynamic gantry-couch movements. Then, for each gantry-couch track the most suitable collimator angle is determined for each control point by optimizing the area between the MLC leaves and the target contour. The resulting dynamic trajectories are used as input to perform the optimization using a research version of the VMAT optimization algorithm and the ESRAPI. The feasibility of this procedure was tested for a clinically motivated head and neck case. Resulting dose distributions for the VMAT plan and for the dynamic trajectory treatment plan were compared based on DVH-parameters. Results: While the DVH for the target is virtually preserved, improvements in maximum dose for the DTRT plan were achieved for all OARs except for the inner-ear, where maximum dose remains the same. The major improvements in maximum dose were 6.5% of the prescribed dose (66 Gy) for the parotid and 5.5% for the myelon and the eye. Conclusion: The result of this work suggests that DTRT has a great potential to reduce dose to OARs with similar target coverage when compared to conventional VMAT treatment plans. This work was supported by Varian Medical Systems. This work was supported by Varian Medical Systems.« less
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Photon spectral characteristics of dissimilar 6 MV linear accelerators.
Hinson, William H; Kearns, William T; deGuzman, Allan F; Bourland, J Daniel
2008-05-01
This work measures and compares the energy spectra of four dosimetrically matched 6 MV beams, generated from four physically different linear accelerators. The goal of this work is twofold. First, this study determines whether the spectra of dosimetrically matched beams are measurably different. This study also demonstrates that the spectra of clinical photon beams can be measured as a part of the beam data collection process for input to a three-dimensional (3D) treatment planning system. The spectra of 6 MV beams that are dosimetrically matched for clinical use were studied to determine if the beam spectra are similarly matched. Each of the four accelerators examined had a standing waveguide, but with different physical designs. The four accelerators were two Varian 2100C/Ds (one 6 MV/18 MV waveguide and one 6 MV/10 MV waveguide), one Varian 600 C with a vertically mounted waveguide and no bending magnet, and one Siemens MD 6740 with a 6 MV/10 MV waveguide. All four accelerators had percent depth dose curves for the 6 MV beam that were matched within 1.3%. Beam spectra were determined from narrow beam transmission measurements through successive thicknesses of pure aluminum along the central axis of the accelerator, made with a graphite Farmer ion chamber with a Lucite buildup cap. An iterative nonlinear fit using a Marquardt algorithm was used to find each spectrum. Reconstructed spectra show that all four beams have similar energy distributions with only subtle differences, despite the differences in accelerator design. The measured spectra of different 6 MV beams are similar regardless of accelerator design. The measured spectra show excellent agreement with those found by the auto-modeling algorithm in a commercial 3D treatment planning system that uses a convolution dose calculation algorithm. Thus, beam spectra can be acquired in a clinical setting at the time of commissioning as a part of the routine beam data collection.
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Klein, Eric E; Esthappan, Jacqueline; Li, Zuofeng
2003-01-01
Understanding head scatter characteristics of photon beams is vital to properly commission treatment planning (TP) algorithms. Simultaneously, having definitive surface and buildup region dosimetry is important to optimize bolus. The Elekta Precise linacs have unique beam flattening filter configurations for each photon beam (6, 10, and 18 MV) in terms of material and location. We performed a comprehensive set of surface and buildup dose measurements with a thin window parallel-plate (PP) chamber to examine effects of field size (FS), source-to-skin distance (SSD), and attenuating media. Relative ionization data were converted to fractional depth dose (FDD) after correcting for bias effects and using the Gerbi method to account for chamber characteristics. Data were compared with a similar vintage Varian linac. At short SSDs the surface and buildup dose characteristics were similar to published data for Varian and Elekta accelerators. The FDD at surface (FDD(0)) for 6, 10, and 18 MV photons was 0.171, 0.159, and 0.199, respectively, for a 15x15 cm2, 100 cm SSD field. A blocking tray increased FDD(0) to 0.200, 0.200, and 0.256, while the universal wedge decreased FDD(0) to 0.107, 0.124, and 0.176. FDD(0) increased linearly with FS (approximately 1.16%/cm). FDD(0) decreased exponentially for 10 and 18 MV with increasing SSD. However, the 6 MV FDD(0) actually increased slightly with increasing SSD. This is likely due to the unique distal flattening filter for 6 MV. The measured buildup curves have been used to optimize TP calculations and guide bolus decisions. Overall the FDD(0) and buildup doses were very similar to published data. Of interest were the relatively low 10 MV surface doses, and the 6 MV FDD(0)'s dependence on SSD.
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SU-E-J-153: Reconstructing 4D Cone Beam CT Images for Clinical QA of Lung SABR Treatments
DOE Office of Scientific and Technical Information (OSTI.GOV)
Beaudry, J; Bergman, A; British Columbia Cancer Agency, Vancouver, BC
Purpose: To verify that the planned Primary Target Volume (PTV) and Internal Gross Tumor Volume (IGTV) fully enclose a moving lung tumor volume as visualized on a pre-SABR treatment verification 4D Cone Beam CT. Methods: Daily 3DCBCT image sets were acquired immediately prior to treatment for 10 SABR lung patients using the on-board imaging system integrated into a Varian TrueBeam (v1.6: no 4DCBCT module available). Respiratory information was acquired during the scan using the Varian RPM system. The CBCT projections were sorted into 8 bins offline, both by breathing phase and amplitude, using in-house software. An iterative algorithm based onmore » total variation minimization, implemented in the open source reconstruction toolkit (RTK), was used to reconstruct the binned projections into 4DCBCT images. The relative tumor motion was quantified by tracking the centroid of the tumor volume from each 4DCBCT image. Following CT-CBCT registration, the planning CT volumes were compared to the location of the CBCT tumor volume as it moves along its breathing trajectory. An overlap metric quantified the ability of the planned PTV and IGTV to contain the tumor volume at treatment. Results: The 4DCBCT reconstructed images visibly show the tumor motion. The mean overlap between the planned PTV (IGTV) and the 4DCBCT tumor volumes was 100% (94%), with an uncertainty of 5% from the 4DCBCT tumor volume contours. Examination of the tumor motion and overlap metric verify that the IGTV drawn at the planning stage is a good representation of the tumor location at treatment. Conclusion: It is difficult to compare GTV volumes from a 4DCBCT and a planning CT due to image quality differences. However, it was possible to conclude the GTV remained within the PTV 100% of the time thus giving the treatment staff confidence that SABR lung treatements are being delivered accurately.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Carver, R; Popple, R; Benhabib, S
Purpose: To evaluate the accuracy of electron dose distribution calculated by the Varian Eclipse electron Monte Carlo (eMC) algorithm for use with recent commercially available bolus electron conformal therapy (ECT). Methods: eMC-calculated electron dose distributions for bolus ECT have been compared to those previously measured for cylindrical phantoms (retromolar trigone and nose), whose axial cross sections were based on the mid-PTV CT anatomy for each site. The phantoms consisted of SR4 muscle substitute, SR4 bone substitute, and air. The bolus ECT treatment plans were imported into the Eclipse treatment planning system and calculated using the maximum allowable histories (2×10{sup 9}),more » resulting in a statistical error of <0.2%. Smoothing was not used for these calculations. Differences between eMC-calculated and measured dose distributions were evaluated in terms of absolute dose difference as well as distance to agreement (DTA). Results: Results from the eMC for the retromolar trigone phantom showed 89% (41/46) of dose points within 3% dose difference or 3 mm DTA. There was an average dose difference of −0.12% with a standard deviation of 2.56%. Results for the nose phantom showed 95% (54/57) of dose points within 3% dose difference or 3 mm DTA. There was an average dose difference of 1.12% with a standard deviation of 3.03%. Dose calculation times for the retromolar trigone and nose treatment plans were 15 min and 22 min, respectively, using 16 processors (Intel Xeon E5-2690, 2.9 GHz) on a Varian Eclipse framework agent server (FAS). Results of this study were consistent with those previously reported for accuracy of the eMC electron dose algorithm and for the .decimal, Inc. pencil beam redefinition algorithm used to plan the bolus. Conclusion: These results show that the accuracy of the Eclipse eMC algorithm is suitable for clinical implementation of bolus ECT.« less
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Lee, Richard; Gete, Ermias; Duzenli, Cheryl
2015-01-01
The purpose of this study was to investigate amplitude gating combined with a coached breathing strategy for 10 MV flattening filter‐free (FFF) volumetric‐modulated arc therapy (VMAT) on the Varian TrueBeam linac. Ten patient plans for VMAT SABR liver were created using the Eclipse treatment planning system (TPS). The verification plans were then transferred to a CT‐scanned Quasar phantom and delivered on a TrueBeam linac using a 10 MV FFF beam and Varian's real‐time position management (RPM) system for respiratory gating based on breathing amplitude. Breathing traces were acquired from ten patients using two kinds of breathing patterns: free breathing and an interrupted (~5 s pause) end of exhale coached breathing pattern. Ion chamber and Gafchromic film measurements were acquired for a gated delivery while the phantom moved under the described breathing patterns, as well as for a nongated stationary phantom delivery. The gate window was set to obtain a range of residual target motion from 2–5 mm. All gated deliveries on a moving phantom have been shown to be dosimetrically equivalent to the nongated deliveries on a static phantom, with differences in point dose measurements under 1% and average gamma 2%/2 mm agreement above 98.7%. Comparison with the treatment planning system also resulted in good agreement, with differences in point‐dose measurements under 2.5% and average gamma 3%/3 mm agreement of 97%. The use of a coached breathing pattern significantly increases the duty cycle, compared with free breathing, and allows for shorter treatment times. Patients' free‐breathing patterns contain considerable variability and, although dosimetric results for gated delivery may be acceptable, it is difficult to achieve efficient treatment delivery. A coached breathing pattern combined with a 5 mm amplitude gate, resulted in both high‐quality dose distributions and overall shortest gated beam delivery times. PACS number: 87.55.Qr PMID:26219000
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Liu, Paul Z.Y.; Lee, Christopher; McKenzie, David R.; Suchowerska, Natalka
2016-01-01
Flattening filter‐free (FFF) beams are becoming the preferred beam type for stereotactic radiosurgery (SRS) and stereotactic ablative radiation therapy (SABR), as they enable an increase in dose rate and a decrease in treatment time. This work assesses the effects of the flattening filter on small field output factors for 6 MV beams generated by both Elekta and Varian linear accelerators, and determines differences between detector response in flattened (FF) and FFF beams. Relative output factors were measured with a range of detectors (diodes, ionization chambers, radiochromic film, and microDiamond) and referenced to the relative output factors measured with an air core fiber optic dosimeter (FOD), a scintillation dosimeter developed at Chris O'Brien Lifehouse, Sydney. Small field correction factors were generated for both FF and FFF beams. Diode measured detector response was compared with a recently published mathematical relation to predict diode response corrections in small fields. The effect of flattening filter removal on detector response was quantified using a ratio of relative detector responses in FFF and FF fields for the same field size. The removal of the flattening filter was found to have a small but measurable effect on ionization chamber response with maximum deviations of less than ±0.9% across all field sizes measured. Solid‐state detectors showed an increased dependence on the flattening filter of up to ±1.6%. Measured diode response was within ±1.1% of the published mathematical relation for all fields up to 30 mm, independent of linac type and presence or absence of a flattening filter. For 6 MV beams, detector correction factors between FFF and FF beams are interchangeable for a linac between FF and FFF modes, providing that an additional uncertainty of up to ±1.6% is accepted. PACS number(s): 87.55.km, 87.56.bd, 87.56.Da PMID:27167280
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Barbiere, J; Beninati, G; Ndlovu, A
2015-06-15
Purpose: It has been argued that a 3D-conformal technique (3DCRT) is suitable for SBRT due to its simplicity for non-coplanar planning and delivery. It has also been hypothesized that a high dose delivered in a short time can enhance indirect cell death due to vascular damage as well as limiting intrafraction motion. Flattening Filter Free (FFF) photon beams are ideal for high dose rate treatment but their conical profiles are not ideal for 3DCRT. The purpose of our work is to present a method to efficiently segment an FFF beam for standard 3DCRT planning. Methods: A 10×10 cm Varian Truemore » Beam 6X FFF beam profile was analyzed using segmentation theory to determine the optimum segmentation intensity required to create an 8 cm uniform dose profile. Two segments were automatically created in sequence with a Varian Eclipse treatment planning system by converting isodoses corresponding to the calculated segmentation intensity to contours and applying the “fit and shield” tool. All segments were then added to the FFF beam to create a single merged field. Field blocking can be incorporated but was not used for clarity. Results: Calculation of the segmentation intensity using an algorithm originally proposed by Xia and Verhey indicated that each segment should extend to the 92% isodose. The original FFF beam with 100% at the isocenter at a depth of 10 cm was reduced to 80% at 4cm from the isocenter; the segmented beam had +/−2.5 % uniformity up to 4.4cm from the isocenter. An additional benefit of our method is a 50% decrease in the 80%-20% penumbra of 0.6cm compared to 1.2cm in the original FFF beam. Conclusion: Creation of two optimum segments can flatten a FFF beam and also reduce its penumbra for clinical 3DCRT SBRT treatment.« less
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SU-E-T-129: Are Knowledge-Based Planning Dose Estimates Valid for Distensible Organs?
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lalonde, R; Heron, D; Huq, M
2015-06-15
Purpose: Knowledge-based planning programs have become available to assist treatment planning in radiation therapy. Such programs can be used to generate estimated DVHs and planning constraints for organs at risk (OARs), based upon a model generated from previous plans. These estimates are based upon the planning CT scan. However, for distensible OARs like the bladder and rectum, daily variations in volume may make the dose estimates invalid. The purpose of this study is to determine whether knowledge-based DVH dose estimates may be valid for distensible OARs. Methods: The Varian RapidPlan™ knowledge-based planning module was used to generate OAR dose estimatesmore » and planning objectives for 10 prostate cases previously planned with VMAT, and final plans were calculated for each. Five weekly setup CBCT scans of each patient were then downloaded and contoured (assuming no change in size and shape of the target volume), and rectum and bladder DVHs were recalculated for each scan. Dose volumes were then compared at 75, 60,and 40 Gy for the bladder and rectum between the planning scan and the CBCTs. Results: Plan doses and estimates matched well at all dose points., Volumes of the rectum and bladder varied widely between planning CT and the CBCTs, ranging from 0.46 to 2.42 for the bladder and 0.71 to 2.18 for the rectum, causing relative dose volumes to vary between planning CT and CBCT, but absolute dose volumes were more consistent. The overall ratio of CBCT/plan dose volumes was 1.02 ±0.27 for rectum and 0.98 ±0.20 for bladder in these patients. Conclusion: Knowledge-based planning dose volume estimates for distensible OARs are still valid, in absolute volume terms, between treatment planning scans and CBCT’s taken during daily treatment. Further analysis of the data is being undertaken to determine how differences depend upon rectum and bladder filling state. This work has been supported by Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Butson, M; Carroll, S; Whitaker, M
2015-06-15
Purpose: Tangential breast irradiation is a standard treatment technique for breast cancer therapy. One aspect of dose delivery includes dose delivered to the skin caused by electron contamination. This effect is especially important for highly oblique beams used on the medical tangent where the electron contamination deposits dose on the contralateral breast side. This work aims to investigate and predict as well as define a method to reduce this dose during tangential breast radiotherapy. Methods: Analysis and calculation of breast skin and subcutaneous dose is performed using a Varian Eclipse planning system, AAA algorithm for 6MV x-ray treatments. Measurements weremore » made using EBT3 Gafchromic film to verify the accuracy of planning data. Various materials were tested to assess their ability to remove electron contamination on the contralateral breast. Results: Results showed that the Varian Eclipse AAA algorithm could accurately estimate contralateral breast dose in the build-up region at depths of 2mm or deeper. Surface dose was underestimated by the AAA algorithm. Doses up to 12% of applied dose were seen on the contralateral breast surface and up to 9 % at 2mm depth. Due to the nature of this radiation, being mainly low energy electron contamination, a bolus material could be used to reduce this dose to less than 3%. This is accomplished by 10 mm of superflab bolus or by 1 mm of lead. Conclusion: Contralateral breast skin and subcutaneous dose is present for tangential breast treatment and has been measured to be up to 12% of applied dose from the medial tangent beam. This dose is deposited at shallow depths and is accurately calculated by the Eclipse AAA algorithm at depths of 2mm or greater. Bolus material placed over the contralateral can be used to effectively reduce this skin dose.« less
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Deufel, Christopher L; Furutani, Keith M; Dahl, Robert A; Haddock, Michael G
2016-01-01
The ability to create treatment plans for intraoperative high-dose-rate (IOHDR) brachytherapy is limited by lack of imaging and time constraints. An automated method for creation of a library of high-dose-rate brachytherapy plans that can be used with standard planar applicators in the intraoperative setting is highly desirable. Nonnegative least squares algebraic methods were used to identify dwell time values for flat, rectangular planar applicators. The planar applicators ranged in length and width from 2 cm to 25 cm. Plans were optimized to deliver an absorbed dose of 10 Gy to three different depths from the patient surface: 0 cm, 0.5 cm, and 1.0 cm. Software was written to calculate the optimized dwell times and insert dwell times and positions into a .XML plan template that can be imported into the Varian brachytherapy treatment planning system. The user may import the .XML template into the treatment planning system in the intraoperative setting to match the patient applicator size and prescribed treatment depth. A total of 1587 library plans were created for IOHDR brachytherapy. Median plan generation time was approximately 1 minute per plan. Plan dose was typically 100% ± 1% (mean, standard deviation) of the prescribed dose over the entire length and width of the applicator. Plan uniformity was best for prescription depths of 0 cm and 0.5 cm from the patient surface. An IOHDR plan library may be created using automated methods. Thousands of plan templates may be optimized and prepared in a few hours to accommodate different applicator sizes and treatment depths and reduce treatment planning time. The automated method also enforces dwell time symmetry for symmetrical applicator geometries, which simplifies quality assurance. Copyright © 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.
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SU-F-T-263: Dosimetric Characteristics of the Cine Acquisition Mode of An A-Si EPID
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bawazeer, O; Deb, P; Sarasanandarajah, S
2016-06-15
Purpose: To investigate the dosimetric characteristics of Varian a-Si-500 electronic portal imaging device (EPID) operated in cine mode particularly considering linearity with delivered dose, dose rate, field size, phantom thickness, MLC speed and common IMRT fields. Methods: The EPID that attached to a Varian Clinac 21iX linear accelerator, was irradiated with 6 and 18 MV using 600 MU/min. Image acquisition is controlled by the IAS3 software, Trigger delay was 6 ms, BeamOnDelay and FrameStartDelay were zero. Different frame rates were utilized. Cine mode response was calculated using MATLAB as summation of mean pixel values in a region of interest ofmore » the acquired images. The performance of cine mode was compared to integrated mode and dose measurements in water using CC13 ionization chamber. Results: Figure1 illustrates that cine mode has nonlinear response for small MU, when delivering 10 MU was about 0.5 and 0.64 for 6 and 18 MV respectively. This is because the missing acquired images that were calculated around four images missing in each delivery. With the increase MU the response became linear and comparable with integrated mode and ionization chamber within 2%. Figure 2 shows that cine mode has comparable response with integrated mode and ionization chamber within 2% with changing dose rate for 10 MU delivered. This indicates that the dose rate change has no effect on nonlinearity of cine mode response. Except nonlinearity, cine mode is well matched to integrated mode response within 2% for field size, phantom thickness, MLC speed dependences. Conclusion: Cine mode has similar dosimetric characteristics to integrated mode with open and IMRT fields, and the main limitation with cine mode is missing images. Therefore, the calibration of EPID images with this mode should be run with large MU, and when IMRT verification field has low MU, the correction for missing images are required.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Cebe, M; Pacaci, P; Mabhouti, H
Purpose: In this study, the two available calculation algorithms of the Varian Eclipse treatment planning system(TPS), the electron Monte Carlo(eMC) and General Gaussian Pencil Beam(GGPB) algorithms were used to compare measured and calculated peripheral dose distribution of electron beams. Methods: Peripheral dose measurements were carried out for 6, 9, 12, 15, 18 and 22 MeV electron beams of Varian Triology machine using parallel plate ionization chamber and EBT3 films in the slab phantom. Measurements were performed for 6×6, 10×10 and 25×25cm{sup 2} cone sizes at dmax of each energy up to 20cm beyond the field edges. Using the same filmmore » batch, the net OD to dose calibration curve was obtained for each energy. Films were scanned 48 hours after irradiation using an Epson 1000XL flatbed scanner. Dose distribution measured using parallel plate ionization chamber and EBT3 film and calculated by eMC and GGPB algorithms were compared. The measured and calculated data were then compared to find which algorithm calculates peripheral dose distribution more accurately. Results: The agreement between measurement and eMC was better than GGPB. The TPS underestimated the out of field doses. The difference between measured and calculated doses increase with the cone size. The largest deviation between calculated and parallel plate ionization chamber measured dose is less than 4.93% for eMC, but it can increase up to 7.51% for GGPB. For film measurement, the minimum gamma analysis passing rates between measured and calculated dose distributions were 98.2% and 92.7% for eMC and GGPB respectively for all field sizes and energies. Conclusion: Our results show that the Monte Carlo algorithm for electron planning in Eclipse is more accurate than previous algorithms for peripheral dose distributions. It must be emphasized that the use of GGPB for planning large field treatments with 6 MeV could lead to inaccuracies of clinical significance.« less
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Wang, Lilie; Ding, George X
2018-06-12
Therapeutic radiation to cancer patients is accompanied by unintended radiation to organs outside the treatment field. It is known that the model-based dose algorithm has limitation in calculating the out-of-field doses. This study evaluated the out-of-field dose calculated by the Varian Eclipse treatment planning system (v.11 with AAA algorithm) in realistic treatment plans with the goal of estimating the uncertainties of calculated organ doses. Photon beam phase-space files for TrueBeam linear accelerator were provided by Varian. These were used as incident sources in EGSnrc Monte Carlo simulations of radiation transport through the downstream jaws and MLC. Dynamic movements of the MLC leaves were fully modeled based on treatment plans using IMRT or VMAT techniques. The Monte Carlo calculated out-of-field doses were then compared with those calculated by Eclipse. The dose comparisons were performed for different beam energies and treatment sites, including head-and-neck, lung, and pelvis. For 6 MV (FF/FFF), 10 MV (FF/FFF), and 15 MV (FF) beams, Eclipse underestimated out-of-field local doses by 30%-50% compared with Monte Carlo calculations when the local dose was <1% of prescribed dose. The accuracy of out-of-field dose calculations using Eclipse is improved when collimator jaws were set at the smallest possible aperture for MLC openings. The Eclipse system consistently underestimates out-of-field dose by a factor of 2 for all beam energies studied at the local dose level of less than 1% of prescribed dose. These findings are useful in providing information on the uncertainties of out-of-field organ doses calculated by Eclipse treatment planning system. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
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SU-E-T-178: Experimental Study of Acceptable Movement Conditions for SBRT Lung Treatments
DOE Office of Scientific and Technical Information (OSTI.GOV)
Carrasco de Fez, P; Ruiz-Martinez, A; Jornet, N
2014-06-01
Purpose: To experimentally study the acceptable movement conditions for SBRT lung treatments we quantified with film dosimetry the change in dose distributions due to periodic movements of 5 different amplitudes and 4 respiratory gating duty cycles on a SBRT treatment plan. Methods: We planned a SBRT treatment plan for the QUASAR™ (Modus Medical) phantom equipped with the respiratory motion device. We placed a 3 mm water-equivalent sphere simulating a tumour inside the lung-equivalent insert. This sphere is divided in two hemispheres that allow placing films in between. We used radiochromic EBT2™ (Ashland) films. We oriented the lung insert in suchmore » a way that sagittal dose distributions could be measured. We applied a sinusoidal movement with 3 s period for 5 different amplitudes of 0(static), 5, 7, 10, 15 and 20 mm without gating. For the 20 mm amplitude we studied the gating technique with 4 duty cycles of 20, 40, 60 and 80% of the respiratory cycle. Each situation was irradiated in a Clinac 2100 linac (Varian) equipped with the RPM™ system. FilmQA Pro™ (Ashland) software together with an Expression 10000XL scanner (EPSON) were used to analyze and compare the measured dose distributions with those planned by the Eclipse™ TPS v. 8.9 (Varian) by means of gamma analysis with 6 criteria: 5%/3mm, 5%/2mm, 5%/1mm, 3%/3mm, 3%/2mm and 2%/2mm (threshold of 10%). Results: Movements with amplitude of less than 7mm do not significantly modified the dosimetry. Gating duty cycles of less than 40% yielded also acceptable results for a 2 cm amplitude movement. Conclusion: To safely perform daily accurate SBRT treatments, movements have to be restricted to 7 mm amplitude (±3.5 mm). Otherwise, a gating strategy should be considered.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Bogue, J; Parsai, E
Purpose: The current generation of inflatable multichannel brachytherapy applicators, such as the Varian Capri, have limited implementation to only vaginal and rectal cancers. While there are similar designs utilizing rigid, non-inflatable applicators, these alternatives could cause increased dose to surrounding tissue due to air gaps. Modification of the Capri could allow for easier treatment planning by reducing the number of channels and increased versatility by modifying the applicator to include an attachable single tandem for cervical or multiple tandems for endometrial applications. Methods: A Varian Capri applicator was simulated in water to replicate a patient. Multiple plans were optimized tomore » deliver a prescribed dose of 100 cGy at 5mm away from the exterior of the applicator using six to thirteen existing channels. The current model was expanded upon to include a detachable tandem or multiple tandoms to increase its functionality to both cervical and endometrial cancers. Models were constructed in both threedimensional rendering software and Monte Carlo to allow prototyping and simulations. Results: Treatment plans utilizing six to thirteen channels produced limited dosimetric differences between channel arrangements, with a seven channel plan very closely approximating the thirteen channels. It was concluded that only seven channels would be necessary in future simulations to give an accurate representation of the applicator. Tandem attachments were prototyped for the applicator to demonstrate the ease of which they could be included. Future simulation in treatment planning software and Monte Carlo results will be presented to further define the ideal applicator geometry Conclusion: The current Capri applicator design could be easily modified to increase applicability to include cervical and endometrial treatments in addition to vaginal and rectal cancers. This new design helps in a more versatile single use applicator that can easily be inserted and to further reduce dose to critical structures during brachytherapy treatments.« less
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SU-E-T-647: Quality Assurance of VMAT by Gamma Analysis Dependence On Low-Dose Threshold
DOE Office of Scientific and Technical Information (OSTI.GOV)
Song, J; Kim, M; Lee, S
2015-06-15
Purpose: The AAPM TG-119 instructed institutions to use low-dose threshold (LDT) of 10% or a ROI determined by the jaw when they collected gamma analysis QA data of planar dose distribution. Also, based on a survey by Nelms and Simon, more than 70% of institutions use a LDT between 0% and 10% for gamma analysis. However, there are no clinical data to quantitatively demonstrate the impact of the LDT on the gamma index. Therefore, we performed a gamma analysis with LDTs of 0% to 15% according to both global and local normalization and different acceptance criteria: 3%/3 mm, 2%/2 mm,more » and 1%/1 mm. Methods: A total of 30 treatment plans—10 head and neck, 10 brain, and 10 prostate cancer cases—were randomly selected from the Varian Eclipse TPS, retrospectively. For the gamma analysis, a predicted portal image was acquired through a portal dose calculation algorithm in the Eclipse TPS, and a measured portal image was obtained using a Varian Clinac iX and an EPID. Then, the gamma analysis was performed using the Portal Dosimetry software. Results: For the global normalization, the gamma passing rate (%GP) decreased as the LDT increased, and all cases of low-dose thresholds exhibited a %GP above 95% for both the 3%/3 mm and 2%/2 mm criteria. However, for local normalization, the %GP increased as LDT increased. The gamma passing rate with LDT of 10% increased by 6.86%, 9.22% and 6.14% compared with the 0% in the case of the head and neck, brain and prostate for 3%/3 mm criteria, respectively. Conclusion: Applying the LDT in the global normalization does not have critical impact to judge patient-specific QA results. However, LDT for the local normalization should be carefully selected because applying the LDT could affect the average of the %GP to increase rapidly.« less
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SU-E-T-425: Spherical Dose Distributions for Radiosurgery Using a Standardized MLC Plan
DOE Office of Scientific and Technical Information (OSTI.GOV)
Popple, R; Brezovich, I; Wu, X
2014-06-01
Purpose: To investigate a standardized MLC treatment plan to generate small spherical dose distributions. Methods: The static virtual cone plan comprised six table positions with clockwise and counterclockwise arcs having collimator angles 45 and 135 degrees, respectively, at each position. The central two leaves of a 2.5 mm leaf width MLC were set to a constant gap. Control points were weighted proportional to the sine of the gantry angle. Plans were created for the 10 MV flattening-filter-free beam of a TrueBeam STx (Varian Medical Systems) with gaps of 1, 1.5, 2, and 3 mm and were delivered to a phantommore » containing radiochromic film. Dose was calculated using the Eclipse AAA (Varian Medical Systems). A dynamic plan in which the table and gantry moved simultaneously with 1.5 mm gap was also created and delivered using the TrueBeam developer mode. Results: The full-width-half-max (FWHM) varied with leaf gap, ranging from 5.2 to 6.2 mm. Calculated FWHM was smaller than measured by 0.7 mm for the 1 mm gap and ≤ 0.4 mm for the larger gaps. The measured-to-calculated dose ratio was 0.93, 0.96, 1.01, and 0.99 for 1 mm, 1.5 mm, 2 mm, and 3 mm gaps, respectively. The dynamic results were the same as the static. The position deviations between the phantom target position and the center of the dose distribution were < 0.4 mm. Conclusion: The virtual cone can deliver spherical dose distributions suitable for radio surgery of small targets such as the trigeminal nerve. The Eclipse AAA accurately calculates the expected dose, particularly for leaf gap ≥ 1.5 mm. The measured dose distribution is slightly larger than the calculation, which is likely due to systematic leaf position error, isocenter variation due to gantry sag and table eccentricity, and inaccuracy in MLC leaf end modeling.« less
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SU-F-T-437: 3 Field VMAT Technique for Irradiation of Large Pelvic Tumors
DOE Office of Scientific and Technical Information (OSTI.GOV)
Stakhursky, V
2016-06-15
Purpose: VMAT treatment planning for large pelvic volume irradiation could be suboptimal due to inability of Varian linac to split MLC carriage during VMAT delivery for fields larger than 14.5cm in X direction (direction of leaf motion). We compare the dosimetry between 3 VMAT planning techniques, two 2-arc field techniques and a 3-arc field technique: a) two small in X direction (less than 14.5cm) arc fields, complementing each other to cover the whole lateral extent of target during gantry rotation, b) two large arc fields, each covering the targets completely during the rotation, c) a 3 field technique with 2more » small in X direction arcs and 1 large field covering whole target. Methods: 5 GYN cancer patients were selected to evaluate the 3 VMAT planning techniques. Treatment plans were generated using Varian Eclipse (ver. 11) TPS. Dose painting technique was used to deliver 5300 cGy to primary target and 4500 cGy to pelvic/abdominal node target. All the plans were normalized so that the prescription dose of 5300 cGy covered 95% of primary target volume. PTV and critical structures DVH curves were compared to evaluate all 3 planning techniques. Results: The dosimetric differences between the two 2-arc techniques were minor. The small field 2-arc technique showed a colder hot spot (0.4% averaged), while variations in maximum doses to critical structures were statistically nonsignificant (under 1.3%). In comparison, the 3-field technique demonstrated a colder hot spot (1.1% less, 105.8% averaged), and better sparing of critical structures. The maximum doses to larger bowel, small bowel and gluteal fold were 3% less, cord/cauda sparing was 4.2% better, and bladder maximum dose was 4.6% less. The differences in maximum doses to stomach and rectum were statistically nonsignificant. Conclusion: 3-arc VMAT technique for large field irradiation of pelvis demonstrates dosimetric advantages compared to 2-arc VMAT techniques.« less
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TH-AB-BRA-12: Experimental Results From the First High-Field Inline MRI-Linac
DOE Office of Scientific and Technical Information (OSTI.GOV)
Keall, P; Dong, B; Zhang, K
Purpose: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid MRI-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-Linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-Linac system. This work describes our experimental results from the first high-field inline MRI-Linac. Methods: A 1.5 Tesla magnet (Sonata, Siemens) was located in a purpose built RF cage enabling shielding from and close proximity to a linear accelerator with inline orientation. A portable linear acceleratormore » (Linatron, Varian) was installed together with a multi-leaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-Linac experiments was performed to investigate: (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array and; (3) electron focusing measured using GafChromic film. Results: (1) The macropodine phantom image quality with the beam on was almost identical to that with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background noise when the radiation beam was on. (3) Film measurements demonstrated electron focusing occurring at the center of the radiation field. Conclusion: The first high-field MRI-Linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field in-line MRI-Linac and study a number of the technical challenges and solutions. Supported by the Australian National Health and Medical Research Council, the Australian Research Council, the Australian Cancer Research Foundation and the Health and Hospitals Fund.« less
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Technical Note: Experimental results from a prototype high-field inline MRI-linac
DOE Office of Scientific and Technical Information (OSTI.GOV)
Liney, G. P., E-mail: gary.liney@sswahs.nsw.gov.au
Purpose: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid magnetic resonance imaging (MRI)-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-linac system. This work describes results from a prototype experimental system to demonstrate the feasibility of a high field inline MR-linac. Methods: The magnet is a 1.5 T MRI system (Sonata, Siemens Healthcare) was located in a purpose built radiofrequency (RF) cage enablingmore » shielding from and close proximity to a linear accelerator with inline (and future perpendicular) orientation. A portable linear accelerator (Linatron, Varian) was installed together with a multileaf collimator (Millennium, Varian) to provide dynamic field collimation and the whole assembly built onto a stainless-steel rail system. A series of MRI-linac experiments was performed to investigate (1) image quality with beam on measured using a macropodine (kangaroo) ex vivo phantom; (2) the noise as a function of beam state measured using a 6-channel surface coil array; and (3) electron contamination effects measured using Gafchromic film and an electronic portal imaging device (EPID). Results: (1) Image quality was unaffected by the radiation beam with the macropodine phantom image with the beam on being almost identical to the image with the beam off. (2) Noise measured with a surface RF coil produced a 25% elevation of background intensity when the radiation beam was on. (3) Film and EPID measurements demonstrated electron focusing occurring along the centerline of the magnet axis. Conclusions: A proof-of-concept high-field MRI-linac has been built and experimentally characterized. This system has allowed us to establish the efficacy of a high field inline MRI-linac and study a number of the technical challenges and solutions.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Nguyen, V; James, J; Wang, B
Purpose: To describe an in-house video goggle feedback system for motion management during simulation and treatment of radiation therapy patients. Methods: This video goggle system works by splitting and amplifying the video output signal directly from the Varian Real-Time Position Management (RPM) workstation or TrueBeam imaging workstation into two signals using a Distribution Amplifier. The first signal S[1] gets reconnected back to the monitor. The second signal S[2] gets connected to the input of a Video Scaler. The S[2] signal can be scaled, cropped and panned in real time to display only the relevant information to the patient. The outputmore » signal from the Video Scaler gets connected to an HDMI Extender Transmitter via a DVI-D to HDMI converter cable. The S[2] signal can be transported from the HDMI Extender Transmitter to the HDMI Extender Receiver located inside the treatment room via a Cat5e/6 cable. Inside the treatment room, the HDMI Extender Receiver is permanently mounted on the wall near the conduit where the Cat5e/6 cable is located. An HDMI cable is used to connect from the output of the HDMI Receiver to the video goggles. Results: This video goggle feedback system is currently being used at two institutions. At one institution, the system was just recently implemented for simulation and treatments on two breath-hold gated patients with 8+ total fractions over a two month period. At the other institution, the system was used to treat 100+ breath-hold gated patients on three Varian TrueBeam linacs and has been operational for twelve months. The average time to prepare the video goggle system for treatment is less than 1 minute. Conclusion: The video goggle system provides an efficient and reliable method to set up a video feedback signal for radiotherapy patients with motion management.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Cardan, R; Popple, R; Smith, H
Purpose: To elucidate realistic clinical treatment planning workload and timelines to improve understanding for patients, payers, and other institutions involved in radiotherapy processes. Methods: A web based tool was developed using Oracle Express (Oracle Corp, Redwood City, CA) which allowed communication between the physicians and staff about the current state of the patient plan. For 6 years, all patient courses were logged and time-stamped in 22 discreet steps which detailed start and stop times for simulation, contouring, and treatment planning tasks. This data was combined with the treatment planning database (TPDB) using the Eclipse Scripting API (Varian Medical Systems, Palomore » Alto, CA) to cross-identify plans between the two systems. This time data was analyzed across our dosimetry staff and treatment modality. Results: In 6 years, 110,477 patient statuses were time-logged for 9683 courses of treatment using our internal software. The courses contained 8305 unique patients who were binned into one of 11 diagnosis site categories. 8253 courses could be reconciled against the TPDB using timestamp data from patient statuses. The average planning volume per dosimetrist was 375.8 ± 142.4 plans per year with the average number of planning revisions per dosimetrist of 71.0 ± 27.1 plans per year. The median treatment planning times by modality ranged from to 48.3 hours for IMRT plans 5 fields or less to 119.6 hours for IMRT with 8 or more fields. Two arc VMAT, three arc VMAT, and 3D plans median times were 89.1 hours, 113.8 hours, and 50.9 hours respectively. Conclusion: Using our web based tool, we have demonstrated the ability to quantify treatment planning timelines and workloads which could help in setting appropriate expectations for patients, payers, and hospital administration. COI: Author received monies from Varian Medical Systems for research and teaching honorarium.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Laoui, S; Dietrich, S; Sehgal, V
2016-06-15
Purpose: Radiation dose delivery for endometrial cancer using HDR techniques is limited by dose to bladder and rectum. A dosimetric study was performed using Varian Capri vaginal brachytherapy applicator to determine the optimal channel configuration which minimizes dose to bladder and rectum, while providing good target coverage. Methods: A total of 17 patients, 63 plans clinically delivered, and 252 simulated plans using Varian BrachyVision planning system were generated to investigate optimal channel configuration which results in minimum dose to bladder and rectum while providing adequate target coverage. The Capri applicator consists of 13 lumens arranged in two concentric rings, onemore » central lumen and six lumens per ring. Manual dose shaping is invariably required to lower the dose to critical organs. Three-dimensional plans were simulated for 4 channel arrangements, all 13 channels, channel 12 o’clock (close to bladder) and 6 o’clock (close to rectum) deactivated, central channel deactivated, and central channel in addition to 12 o’clock and 6 o’clock deactivated. A relationship between V100, the volume that receives the prescribed dose, and the amount of curie-seconds required to deliver it, was established. Results: Using all 13 channels results in maximum dose to bladder and rectum. Deactivating central channel in addition to 12 o’clock and 6 o’clock resulted in minimizing bladder and rectum doses but compromised target coverage. The relationship between V100, the volume that receives the prescribed dose, and the curie seconds was found to be linear. Conclusion: Deactivating channels 12 o’clock and 6 o’clock was shown to be the optimal configuration leading to minimum dose to bladder and rectum without compromising target coverage. The linear relationship between V100 and the curie- seconds can be used as a verification parameter.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Legge, K; O’Connor, D J; Nguyen, D
Purpose: To determine prostate motion during SBRT boost treatments with a Rectafix rectal sparing device in place using kV imaging during treatment. Methods: Patients each had three gold fiducial markers inserted into the prostate and received two VMAT boost fractions of 9.5–10 Gy under the PROMETHEUS clinical trial protocol with a Rectafix rectal retractor in place. Two-dimensional kilovoltage images of fiducial markers were acquired continuously during delivery. Three patients were treated on a Varian Clinac iX linear accelerator (6X, 600 MU/min), where kV images were acquired at 5 Hz during treatment. Seven patients were treated on a Varian Truebeam linearmore » accelerator (10XFFF, 2400 MU/min) where kV images were acquired every 3 seconds. Images were processed off-line using the Kilovoltage Intrafraction Monitoring (KIM) software after treatment. KIM determines prostate position in three dimensions from 2D kV projections using a probability density model and a pre-treatment kV arc. The 3D displacement of the prostate was quantified as a function of time throughout each fraction. Results: From all fractions analyzed, it was found that the prostate had moved less than 1 mm in any direction from its initial position 84.6% of the time. The prostate was between 1 and 2 mm from its initial position 14.2% of the time, between 2 and 3 mm of its initial position 0.8% of the time and was greater than 3 mm from its initial position only 0.4% of the time. Conclusion: The amount of prostate motion observed during prostate SBRT boost treatments with a Rectafix device in place was minimal and lower than that observed in non-Rectafix studies. The Rectafix device reduces rectal dose as well as immobilizing the prostate. Kimberley Legge is the recipient of an Australian Postgraduate Award.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Santoro, J; Witten, M; Haas, J
Purpose: Brachytherapy has been the standard of care for cervical cancer for 100 years. The treatment can be administered using an HDR (high dose rate) remote afterloader with a {sup 192}Ir source in an outpatient setting, a PDR afterloader with a {sup 192}Ir source, or with LDR manually loaded or a remote afterloader utilizing {sup 192}Ir or {sup 137}Cs sources in an inpatient setting. The procedure involves the placement of a tandem and ovoid, tandem and ring, or tandem and cylinder applicator in an operating room setting with the patient under general anesthesia. Inaccuracies introduced into the process occurring betweenmore » placement of the applicator and actual delivery can introduce uncertainty into the actual dose delivered to the tumor and critical organs. In this study we seek to investigate the dosimetric difference between an SBRT-based radiotherapy boost and conventional Brachytherapy in treating cervical cancer. Methods: Five HDR tandem and ovoid patients were planned using the Brachyvision treatment planning system and treated in four fractions using the Varian Varisource afterloader (Varian Medical Systems). For the same cohort, the patient planning CTs were imported into Multiplan (Accuray Inc) and a dose/fractionation-equivalent CyberKnife SBRT plan was retrospectively generated. Dosimetric quantities such as target/CTV D90, V90, D2cc for rectum, bladder, and bowel were measured and compared between the two modalities. Results: The CTV D90 for the tandem and ovoid was 2540cGy (90.7%) and 3009cGy (107.5%) for the CyberKnife plan. The D2cc for the rectum, bladder, and bowel were 1576cGy, 1641cGy, and 996cGy for the tandem and ovoid and 1374cGy, 1564cGy, and 1547cGy for CyberKnife. Conclusion: The D2cc doses to critical structures are comparable in both modalities. The CTV coverage is far superior for the CyberKnife plan. The dose distribution for CyberKnife has the advantage of increased conformality and lower maximum CTV dose.« less
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SU-F-T-458: Tracking Trends of TG-142 Parameters Via Analysis of Data Recorded by 2D Chamber Array
DOE Office of Scientific and Technical Information (OSTI.GOV)
Alexandrian, A; Kabat, C; Defoor, D
Purpose: With increasing QA demands of medical physicists in clinical radiation oncology, the need for an effective method of tracking clinical data has become paramount. A tool was produced which scans through data automatically recorded by a 2D chamber array and extracts relevant information recommended by TG-142. Using this extracted information a timely and comprehensive analysis of QA parameters can be easily performed enabling efficient monthly checks on multiple linear accelerators simultaneously. Methods: A PTW STARCHECK chamber array was used to record several months of beam outputs from two Varian 2100 series linear accelerators and a Varian NovalisTx−. In conjunctionmore » with the chamber array, a beam quality phantom was used to simultaneously to determine beam quality. A minimalist GUI was created in MatLab that allows a user to set the file path of the data for each modality to be analyzed. These file paths are recorded to a MatLab structure and then subsequently accessed by a script written in Python (version 3.5.1) which then extracts values required to perform monthly checks as outlined by recommendations from TG-142. The script incorporates calculations to determine if the values recorded by the chamber array fall within an acceptable threshold. Results: Values obtained by the script are written to a spreadsheet where results can be easily viewed and annotated with a “pass” or “fail” and saved for further analysis. In addition to creating a new scheme for reviewing monthly checks, this application allows for able to succinctly store data for follow up analysis. Conclusion: By utilizing this tool, parameters recommended by TG-142 for multiple linear accelerators can be rapidly obtained and analyzed which can be used for evaluation of monthly checks.« less
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NASA Astrophysics Data System (ADS)
Morton, Daniel R.
Modern image guided radiation therapy involves the use of an isocentrically mounted imaging system to take radiographs of a patient's position before the start of each treatment. Image guidance helps to minimize errors associated with a patients setup, but the radiation dose received by patients from imaging must be managed to ensure no additional risks. The Varian On-Board Imager (OBI) (Varian Medical Systems, Inc., Palo Alto, CA) does not have an automatic exposure control system and therefore requires exposure factors to be manually selected. Without patient specific exposure factors, images may become saturated and require multiple unnecessary exposures. A software based automatic exposure control system has been developed to predict optimal, patient specific exposure factors. The OBI system was modelled in terms of the x-ray tube output and detector response in order to calculate the level of detector saturation for any exposure situation. Digitally reconstructed radiographs are produced via ray-tracing through the patients' volumetric datasets that are acquired for treatment planning. The ray-trace determines the attenuation of the patient and subsequent x-ray spectra incident on the imaging detector. The resulting spectra are used in the detector response model to determine the exposure levels required to minimize detector saturation. Images calculated for various phantoms showed good agreement with the images that were acquired on the OBI. Overall, regions of detector saturation were accurately predicted and the detector response for non-saturated regions in images of an anthropomorphic phantom were calculated to generally be within 5 to 10 % of the measured values. Calculations were performed on patient data and found similar results as the phantom images, with the calculated images being able to determine detector saturation with close agreement to images that were acquired during treatment. Overall, it was shown that the system model and calculation method could potentially be used to predict patients' exposure factors before their treatment begins, thus preventing the need for multiple exposures.
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Elith, Craig A; Dempsey, Shane E; Warren-Forward, Helen M
2013-01-01
Introduction The primary aim of this study is to compare intensity modulated radiation therapy (IMRT) to volumetric modulated arc therapy (VMAT) for the radical treatment of prostate cancer using version 10.0 (v10.0) of Varian Medical Systems, RapidArc radiation oncology system. Particular focus was placed on plan quality and the implications on departmental resources. The secondary objective was to compare the results in v10.0 to the preceding version 8.6 (v8.6). Methods Twenty prostate cancer cases were retrospectively planned using v10.0 of Varian's Eclipse and RapidArc software. Three planning techniques were performed: a 5-field IMRT, VMAT using one arc (VMAT-1A), and VMAT with two arcs (VMAT-2A). Plan quality was assessed by examining homogeneity, conformity, the number of monitor units (MUs) utilized, and dose to the organs at risk (OAR). Resource implications were assessed by examining planning and treatment times. The results obtained using v10.0 were also compared to those previously reported by our group for v8.6. Results In v10.0, each technique was able to produce a dose distribution that achieved the departmental planning guidelines. The IMRT plans were produced faster than VMAT plans and displayed improved homogeneity. The VMAT plans provided better conformity to the target volume, improved dose to the OAR, and required fewer MUs. Treatments using VMAT-1A were significantly faster than both IMRT and VMAT-2A. Comparison between versions 8.6 and 10.0 revealed that in the newer version, VMAT planning was significantly faster and the quality of the VMAT dose distributions produced were of a better quality. Conclusion VMAT (v10.0) using one or two arcs provides an acceptable alternative to IMRT for the treatment of prostate cancer. VMAT-1A has the greatest impact on reducing treatment time. PMID:26229615
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SU-F-J-16: Planar KV Imaging Dose Reduction Study
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gershkevitsh, E; Zolotuhhin, D
Purpose: IGRT has become an indispensable tool in modern radiotherapy with kV imaging used in many departments due to superior image quality and lower dose when compared to MV imaging. Many departments use manufacturer supplied protocols for imaging which are not always optimised between image quality and radiation dose (ALARA). Methods: Whole body phantom PBU-50 (Kyoto Kagaku ltd., Japan) for imaging in radiology has been imaged on Varian iX accelerator (Varian Medical Systems, USA) with OBI 1.5 system. Manufacturer’s default protocols were adapted by modifying kV and mAs values when imaging different anatomical regions of the phantom (head, thorax, abdomen,more » pelvis, extremities). Images with different settings were independently reviewed by two persons and their suitability for IGRT set-up correction protocols were evaluated. The suitable images with the lowest mAs were then selected. The entrance surface dose (ESD) for manufacturer’s default protocols and modified protocols were measured with RTI Black Piranha (RTI Group, Sweden) and compared. Image quality was also measured with kVQC phantom (Standard Imaging, USA) for different protocols. The modified protocols have been applied for clinical work. Results: For most cases optimized protocols reduced the ESD on average by a factor of 3(range 0.9–8.5). Further reduction in ESD has been observed by applying bow-tie filter designed for CBCT. The largest reduction in dose (12.2 times) was observed for Thorax lateral protocol. The dose was slightly increased (by 10%) for large pelvis AP protocol. Conclusion: Manufacturer’s default IGRT protocols could be optimised to reduce the ESD to the patient without losing the necessary image quality for patient set-up correction. For patient set-up with planar kV imaging the bony anatomy is mostly used and optimization should focus on this aspect. Therefore, the current approach with anthropomorphic phantom is more advantageous in optimization over standard kV quality control phantoms and SNR metrics.« less
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Men, Kuo; Dai, Jianrong; Chen, Xinyuan; Li, Minghui; Zhang, Ke; Huang, Peng
2017-04-01
To improve the image quality and accuracy of dose calculation for cone-beam computed tomography (CT) images through implementation of a dual-energy cone-beam computed tomography method (DE-CBCT), and evaluate the improvement quantitatively. Two sets of CBCT projections were acquired using the X-ray volumetric imaging (XVI) system on a Synergy (Elekta, Stockholm, Sweden) system with 120kV (high) and 70kV (low) X-rays, respectively. Then, the electron density relative to water (relative electron density (RED)) of each voxel was calculated using a projection-based dual-energy decomposition method. As a comparison, single-energy cone-beam computed tomography (SE-CBCT) was used to calculate RED with the Hounsfield unit-RED calibration curve generated by a CIRS phantom scan with identical imaging parameters. The imaging dose was measured with a dosimetry phantom. The image quality was evaluated quantitatively using a Catphan 503 phantom with the evaluation indices of the reproducibility of the RED values, high-contrast resolution (MTF 50% ), uniformity, and signal-to-noise ratio (SNR). Dose calculation of two simulated volumetric-modulated arc therapy plans using an Eclipse treatment-planning system (Varian Medical Systems, Palo Alto, CA, USA) was performed on an Alderson Rando Head and Neck (H&N) phantom and a Pelvis phantom. Fan-beam planning CT images for the H&N and Pelvis phantom were set as the reference. A global three-dimensional gamma analysis was used to compare dose distributions with the reference. The average gamma values for targets and OAR were analyzed with paired t-tests between DE-CBCT and SE-CBCT. In two scans (H&N scan and body scan), the imaging dose of DE-CBCT increased by 1.0% and decreased by 1.3%. It had a better reproducibility of the RED values (mean bias: 0.03 and 0.07) compared with SE-CBCT (mean bias: 0.13 and 0.16). It also improved the image uniformity (57.5% and 30.1%) and SNR (9.7% and 2.3%), but did not affect the MTF 50% . Gamma analyses of the 3D dose distribution with criteria of 1%/1mm showed a pass rate of 99.0-100% and 85.3-97.6% for DE-CBCT and 73.5-99.1% and 80.4-92.7% for SE-CBCT. The average gamma values were reduced significantly by DE-CBCT (p< 0.05). Gamma index maps showed that matching of the dose distribution between CBCT-based and reference was improved by DE-CBCT. DE-CBCT can achieve both better image quality and higher accuracy of dose calculation, and could be applied to adaptive radiotherapy. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
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Constantin, Magdalena; Perl, Joseph; LoSasso, Tom; Salop, Arthur; Whittum, David; Narula, Anisha; Svatos, Michelle; Keall, Paul J
2011-07-01
To create an accurate 6 MV Monte Carlo simulation phase space for the Varian TrueBeam treatment head geometry imported from CAD (computer aided design) without adjusting the input electron phase space parameters. GEANT4 v4.9.2.p01 was employed to simulate the 6 MV beam treatment head geometry of the Varian TrueBeam linac. The electron tracks in the linear accelerator were simulated with Parmela, and the obtained electron phase space was used as an input to the Monte Carlo beam transport and dose calculations. The geometry components are tessellated solids included in GEANT4 as GDML (generalized dynamic markup language) files obtained via STEP (standard for the exchange of product) export from Pro/Engineering, followed by STEP import in Fastrad, a STEP-GDML converter. The linac has a compact treatment head and the small space between the shielding collimator and the divergent are of the upper jaws forbids the implementation of a plane for storing the phase space. Instead, an IAEA (International Atomic Energy Agency) compliant phase space writer was implemented on a cylindrical surface. The simulation was run in parallel on a 1200 node Linux cluster. The 6 MV dose calculations were performed for field sizes varying from 4 x 4 to 40 x 40 cm2. The voxel size for the 60 x 60 x 40 cm3 water phantom was 4 x 4 x 4 mm3. For the 10 x 10 cm2 field, surface buildup calculations were performed using 4 x 4 x 2 mm3 voxels within 20 mm of the surface. For the depth dose curves, 98% of the calculated data points agree within 2% with the experimental measurements for depths between 2 and 40 cm. For depths between 5 and 30 cm, agreement within 1% is obtained for 99% (4 x 4), 95% (10 x 10), 94% (20 x 20 and 30 x 30), and 89% (40 x 40) of the data points, respectively. In the buildup region, the agreement is within 2%, except at 1 mm depth where the deviation is 5% for the 10 x 10 cm2 open field. For the lateral dose profiles, within the field size for fields up to 30 x 30 cm2, the agreement is within 2% for depths up to 10 cm. At 20 cm depth, the in-field maximum dose difference for the 30 x 30 cm2 open field is within 4%, while the smaller field sizes agree within 2%. Outside the field size, agreement within 1% of the maximum dose difference is obtained for all fields. The calculated output factors varied from 0.938 +/- 0.015 for the 4 x 4 cm2 field to 1.088 +/- 0.024 for the 40 x 40 cm2 field. Their agreement with the experimental output factors is within 1%. The authors have validated a GEANT4 simulated IAEA-compliant phase space of the TrueBeam linac for the 6 MV beam obtained using a high accuracy geometry implementation from CAD. These files are publicly available and can be used for further research.
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NASA Technical Reports Server (NTRS)
Sparks, S. D.
1973-01-01
The Varian cup and slat dynode chain was modified to have a flat cathode. These modifications were incorporated in an all-electrostatic photomultiplier tube having a rise time of 0.25 n sec. The tube delivered under the contract had a flat S-20 opaque cathode with a useful diameter of 5 mm. The design of the tube is such that a III to V cathode support is mounted in place of the existing cathode substrate. This cathode support is designed to accept a transferred III to V cathode and maintain the cathode surface in the same position as the S-20 photocathode.
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A SiPM based real time dosimeter for radiotherapic beams
NASA Astrophysics Data System (ADS)
Berra, A.; Conti, V.; Lietti, D.; Milan, L.; Novati, C.; Ostinelli, A.; Prest, M.; Romanó, C.; Vallazza, E.
2015-02-01
This paper describes the development of a scintillator dosimeter prototype for radiotherapic applications based on plastic scintillating fibers readout by Silicon PhotoMultipliers. The dosimeter, whose probes are water equivalent, could be used for quality control measurements, beam characterization and in vivo dosimetry, allowing a real time measurement of the dose spatial distribution. This paper describes the preliminary percentual depth dose scan performed with clinical 6 and 18 MV photon beams, comparing the results with a reference curve. The measurements were performed using a Varian Clinac iX linear accelerator at the Radiotherapy Department of the St. Anna Hospital in Como (IT). The prototype has given promising results, allowing real time measurements of relative dose without applying any correction factors.
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Tarbuk, Anita; Grancarić, Ana Marija; Situm, Mirna; Martinis, Mladen
2010-04-01
Skin cancer incidence in Croatia is steadily increasing in spite of public and governmental permanently measurements. It is clear that will soon become a major public health problem. The primary cause of skin cancer is believed to be a long exposure to solar ultraviolet (UV) radiation. The future designers of UV protective materials should be able to block totally the ultraviolet radiation. The aim of this paper is to present results of measurements concerning UV protecting ability of garments and sun-screening textiles using transmission spectrophotometer Cary 50 Solarscreen (Varian) according to AS/NZS 4399:1996; to show that standard clothing materials are not always adequate to prevent effect of UV radiation to the human skin; and to suggest the possibilities for its improvement for this purpose.
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Neutron Fluence and Dose from a Varian Clinic 1800 Accelerator
1992-06-01
steel wedge 318 630 ± 40 37.8 ± 2.4 900 ± 57 2.83 ± 0.18 1.189 ± 0.075 318 Pb block 316 677 ± 44 40.6 ± 2.6 966 ± 62 3.06 ± 0.20...1.285 ± 0.082 319 Pb block 318 679 ± 43 40.7 ± 2.6 969 ± 62 3.07 ± 0.19 1.280 ± 0.082 328 Pb block 1913 654 ± 41 235 t 15 5590...J-08 10175 500 0.320 2875 8 254 J-08 10056 500 0.320 2875 20 255 J-08 9996 500 0.320 2875 29 256 J-08 10082 500 0.320 2875 40 257 J-09 10062 500
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NASA Astrophysics Data System (ADS)
Fogliata, Antonella; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio; Mancosu, Pietro; Cozzi, Luca
2011-05-01
This corrigendum intends to clarify some important points that were not clearly or properly addressed in the original paper, and for which the authors apologize. The original description of the first Acuros algorithm is from the developers, published in Physics in Medicine and Biology by Vassiliev et al (2010) in the paper entitled 'Validation of a new grid-based Boltzmann equation solver for dose calculation in radiotherapy with photon beams'. The main equations describing the algorithm reported in our paper, implemented as the 'Acuros XB Advanced Dose Calculation Algorithm' in the Varian Eclipse treatment planning system, were originally described (for the original Acuros algorithm) in the above mentioned paper by Vassiliev et al. The intention of our description in our paper was to give readers an overview of the algorithm, not pretending to have authorship of the algorithm itself (used as implemented in the planning system). Unfortunately our paper was not clear, particularly in not allocating full credit to the work published by Vassiliev et al on the original Acuros algorithm. Moreover, it is important to clarify that we have not adapted any existing algorithm, but have used the Acuros XB implementation in the Eclipse planning system from Varian. In particular, the original text of our paper should have been as follows: On page 1880 the sentence 'A prototype LBTE solver, called Attila (Wareing et al 2001), was also applied to external photon beam dose calculations (Gifford et al 2006, Vassiliev et al 2008, 2010). Acuros XB builds upon many of the methods in Attila, but represents a ground-up rewrite of the solver where the methods were adapted especially for external photon beam dose calculations' should be corrected to 'A prototype LBTE solver, called Attila (Wareing et al 2001), was also applied to external photon beam dose calculations (Gifford et al 2006, Vassiliev et al 2008). A new algorithm called Acuros, developed by the Transpire Inc. group, was built upon many of the methods in Attila, but represents a ground-up rewrite of the solver where the methods were especially adapted for external photon beam dose calculations, and described in Vassiliev et al (2010). Acuros XB is the Varian implementation of the original Acuros algorithm in the Eclipse planning system'. On page 1881, the sentence 'Monte Carlo and explicit LBTE solution, with sufficient refinement, will converge on the same solution. However, both methods produce errors (inaccuracies). In explicit LBTE solution methods, errors are primarily systematic, and result from discretization of the solution variables in space, angle, and energy. In both Monte Carlo and explicit LBTE solvers, a trade-off exists between speed and accuracy: reduced computational time may be achieved when less stringent accuracy criteria are specified, and vice versa' should cite the reference Vassiliev et al (2010). On page 1882, the beginning of the sub-paragraph The radiation transport model should start with 'The following description of the Acuros XB algorithm is as outlined by Vassiliev et al (2010) and reports the main steps of the radiation transport model as implemented in Eclipse'. The authors apologize for this lack of clarity in our published paper, and trust that this corrigendum gives full credit to Vassiliev et al in their earlier paper, with respect to previous work on the Acuros algorithm. However we wish to note that the entire contents of the data and results published in our paper are original and the work of the listed authors. References Gifford K A, Horton J L Jr, Wareing T A, Failla G and Mourtada F 2006 Comparison of a finite-element multigroup discrete-ordinates code with Monte Carlo for radiotherapy calculations Phys. Med. Biol. 51 2253-65 Vassiliev O N, Wareing T A, Davis I M, McGhee J, Barnett D, Horton J L, Gifford K, Failla G, Titt U and Mourtada F 2008 Feasibility of a multigroup deterministic solution method for three-dimensional radiotherapy dose calculations Int. J. Radiat. Oncol. Biol. Phys. 72 220-7 Vassiliev O N, Wareing T A, McGhee J, Failla G, Salehpour M R and Mourtada F 2010 Validation of a new grid based Boltzmann equation solver for dose calculation in radiotherapy with photon beams Phys. Med. Biol. 55 581-98 Wareing T A, McGhee J M, Morel J E and Pautz S D 2001 Discontinuous finite element Sn methods on three-dimensional unstructured grids Nucl. Sci. Eng. 138 256-68
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Robertson, S; Kaurin, D; Sweeney, L
2014-06-01
Purpose: Our institution uses a manual laser-based system for primary localization and verification during radiation treatment of left-sided breast cancer patients using deep inspiration breath hold (DIBH). This primary system was compared with sternum-placed Calypso(R) beacons (Varian Medical Systems, CA). Only intact breast patients are considered for this analysis. Methods: During computed tomography (CT) simulation, patients have BB and Calypso(R) surface beacons positioned sternally and marked for free-breathing and DIBH CTs. During dosimetry planning, BB longitudinal displacement between free breathing and DIBH CT determines laser mark (BH mark) location. Calypso(R) beacon locations from the DIBH CT are entered at themore » Tracking Station. During Linac simulation and treatment, patients inhale until the cross-hair and/or lasers coincide with the BH Mark, which can be seen using our high quality cameras (Pelco, CA). Daily Calypso(R) displacement values (difference from the DIBH-CT-based plan) are recorded.The displacement mean and standard deviation was calculated for each patient (77 patients, 1845 sessions). An aggregate mean and standard deviation was calculated weighted by the number of patient fractions.Some patients were shifted based on MV ports. A second data set was calculated with Calypso(R) values corrected by these shifts. Results: Mean displacement values indicate agreement within 1±3mm, with improvement for shifted data (Table). Conclusion: Both unshifted and shifted data sets show the Calypso(R) system coincides with the laser system within 1±3mm, demonstrating either localization/verification system will Resultin similar clinical outcomes. Displacement value uncertainty unilaterally reduces when shifts are taken into account.« less
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NASA Astrophysics Data System (ADS)
Haryani, S.; Kurniawan, C.; Kasmui
2018-04-01
Synthesis of complex compound is one field of research which intensively studied. Metal-dithiocarbamate complexes find wide-ranging applications in nanomaterial and metal separation science, and have potential use as chemotherapeutic, pesticides, and as additives to lubricants. However, the information about is reaction kinetic and mechanism are very much lacking. The research and analyzes results show that reaction synthesis ligand DBDTC and complex compounds Cu-DBDTC. Optimum reaction condition of formation of complex compounds Cu with DBDTC at pH=3, [DBDTC] = 4.10-3 M, and the time of reaction 5 minutes. Based the analysis varian reaction of complex compounds at pH 3 and 4, diffrence significance at the other pH: 5; 5,5; 6; 6,5 ; 7; and 8. The various of mole with reactants comosition difference sigbificance, those the time reaction for 5 and 6 minutes diffrence by significance with the other time, it is 3,4,8, and 10 minutes. The great product to at condition pH 6, the time optimum at 5 minutes and molar ratio of logam: ligand = 1:2. The reaction kinetic equation of complex compound Cu with chelathing ligand DBDTC is V=0.917106 [Cu2+]0.87921 [DBDTC]2.03021. Based on the kinetic data, and formed complex compounds estimation, the mechanism explaining by 2 stages. In the first stage formation of [Cu(DBDTC)], and then [Cu(DBDTC)2] with the last structure geomethry planar rectangle. The result of this research will be more useful if an effort is being done in reaction mechanism by chemical computation method for obtain intermediate, and for constant “k” in same stage, k1.k2. and compound complex constanta (β).
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Kim, Hee Jung; Department of Biomedical Engineering, Seoul National University, Seoul; Department of Radiation Oncology, Soonchunhyang University Hospital, Seoul
2015-01-01
To investigate how accurately treatment planning systems (TPSs) account for the tongue-and-groove (TG) effect, Monte Carlo (MC) simulations and radiochromic film (RCF) measurements were performed for comparison with TPS results. Two commercial TPSs computed the TG effect for Varian Millennium 120 multileaf collimator (MLC). The TG effect on off-axis dose profile at 3 depths of solid water was estimated as the maximum depth and the full width at half maximum (FWHM) of the dose dip at an interleaf position. When compared with the off-axis dose of open field, the maximum depth of the dose dip for MC and RCF rangedmore » from 10.1% to 20.6%; the maximum depth of the dose dip gradually decreased by up to 8.7% with increasing depths of 1.5 to 10 cm and also by up to 4.1% with increasing off-axis distances of 0 to 13 cm. However, TPS results showed at most a 2.7% decrease for the same depth range and a negligible variation for the same off-axis distances. The FWHM of the dose dip was approximately 0.19 cm for MC and 0.17 cm for RCF, but 0.30 cm for Eclipse TPS and 0.45 cm for Pinnacle TPS. Accordingly, the integrated value of TG dose dip for TPS was larger than that for MC and RCF and almost invariant along the depths and off-axis distances. We concluded that the TG dependence on depth and off-axis doses shown in the MC and RCF results could not be appropriately modeled by the TPS versions in this study.« less
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NASA Astrophysics Data System (ADS)
Park, Seyoun; Robinson, Adam; Quon, Harry; Kiess, Ana P.; Shen, Colette; Wong, John; Plishker, William; Shekhar, Raj; Lee, Junghoon
2016-03-01
In this paper, we propose a CT-CBCT registration method to accurately predict the tumor volume change based on daily cone-beam CTs (CBCTs) during radiotherapy. CBCT is commonly used to reduce patient setup error during radiotherapy, but its poor image quality impedes accurate monitoring of anatomical changes. Although physician's contours drawn on the planning CT can be automatically propagated to daily CBCTs by deformable image registration (DIR), artifacts in CBCT often cause undesirable errors. To improve the accuracy of the registration-based segmentation, we developed a DIR method that iteratively corrects CBCT intensities by local histogram matching. Three popular DIR algorithms (B-spline, demons, and optical flow) with the intensity correction were implemented on a graphics processing unit for efficient computation. We evaluated their performances on six head and neck (HN) cancer cases. For each case, four trained scientists manually contoured the nodal gross tumor volume (GTV) on the planning CT and every other fraction CBCTs to which the propagated GTV contours by DIR were compared. The performance was also compared with commercial image registration software based on conventional mutual information (MI), VelocityAI (Varian Medical Systems Inc.). The volume differences (mean±std in cc) between the average of the manual segmentations and automatic segmentations are 3.70+/-2.30 (B-spline), 1.25+/-1.78 (demons), 0.93+/-1.14 (optical flow), and 4.39+/-3.86 (VelocityAI). The proposed method significantly reduced the estimation error by 9% (B-spline), 38% (demons), and 51% (optical flow) over the results using VelocityAI. Although demonstrated only on HN nodal GTVs, the results imply that the proposed method can produce improved segmentation of other critical structures over conventional methods.
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Feasibility study of an intensity-modulated radiation model for the study of erectile dysfunction.
Koontz, Bridget F; Yan, Hui; Kimura, Masaki; Vujaskovic, Zeljko; Donatucci, Craig; Yin, Fang-Fang
2011-02-01
Preclinical studies of radiotherapy (RT) induced erectile dysfunction (ED) have been limited by radiation toxicity when using large fields. To develop a protocol of rat prostate irradiation using techniques mimicking the current clinical standard of intensity modulated radiotherapy (IMRT). Quality assurance (QA) testing of plan accuracy, animal health 9 weeks after RT, and intracavernosal pressure (ICP) measurement on cavernosal nerve stimulation. Computed tomography-based planning was used to develop a stereotactic radiosurgery (SRS) treatment plan for five young adult male Sprague-Dawley rats. Two treatment planning strategies were utilized to deliver 20 Gy in a single fraction: three-dimensional dynamic conformal arc and intensity-modulated arc (RapidArc). QA testing was performed for each plan type. Treatment was delivered using a NovalisTX (Varian Medical Systems) with high-definition multi-leaf collimators using on-board imaging prior to treatment. Each animal was evaluated for ED 2 months after treatment by nerve stimulation and ICP measurement. The mean prostate volume and target volume (5 mm expansion of prostate) for the five animals was 0.36 and 0.66 cm3, respectively. Both conformal and RapidArc plans provided at least 95% coverage of the target volume, with rapid dose fall-off. QA plans demonstrated strong agreement between doses of calculated and delivered plans, although the conformal arc plan was more homogenous in treatment delivery. Treatment was well tolerated by the animals with no toxicity out to 9 weeks. Compared with control animals, significant reduction in ICP/mean arterial pressure, maximum ICP, and ICP area under the curve were noted. Tightly conformal dynamic arc prostate irradiation is feasible and results in minimal toxicity and measurable changes in erectile function. © 2010 International Society for Sexual Medicine.
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Design and Development of a Megavoltage CT Scanner for Radiation Therapy.
NASA Astrophysics Data System (ADS)
Chen, Ching-Tai
A Varian 4 MeV isocentric therapy accelerator has been modified to perform also as a CT scanner. The goal is to provide low cost computed tomography capability for use in radiotherapy. The system will have three principal uses. These are (i) to provide 2- and 3-dimensional maps of electron density distribution for CT assisted therapy planning, (ii) to aid in patient set up by providing sectional views of the treatment volume and high contrast scout-mode verification images and (iii) to provide a means for periodically checking the patients anatomical conformation against what was used to generate the original therapy plan. The treatment machine was modified by mounting an array of detectors on a frame bolted to the counter weight end of the gantry in such a manner as to define a 'third generation' CT Scanner geometry. The data gathering is controlled by a Z-80 based microcomputer system which transfers the x-ray transmission data to a general purpose PDP 11/34 for processing. There a series of calibration processes and a logarithmic conversion are performed to get projection data. After reordering the projection data to an equivalent parallel beam sinogram format a convolution algorithm is employed to construct the image from the equivalent parallel projection data. Results of phantom studies have shown a spatial resolution of 2.6 mm and an electron density discrimination of less than 1% which are sufficiently good for accurate therapy planning. Results also show that the system is linear to within the precision of our measurement ((DBLTURN).75%) over a wide range of electron densities corresponding to those found in body tissues. Animal and human images are also presented to demonstrate that the system's imaging capability is sufficient to allow the necessary visualization of anatomy.
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Chow, J; Leung, M; Van Dyk, J
2008-07-01
This study provides new information on the evaluation of the lung dose calculation algorithms as a function of the relative electron density of lung, ρ e,lung . Doses calculated using the collapsed cone convolution (CCC) and adaptive convolution (AC) algorithm in lung with the Pinnacle 3 system were compared to those calculated using the Monte Carlo (MC) simulation (EGSnrc-based code). Three groups of lung phantoms, namely, "Slab", "Column" and "Cube" with different ρ e,lung (0.05-0.7), positions, volumes and shapes of lung in water were used. 6 and 18MV photon beams with 4×4 and 10×10cm 2 field sizes produced by a Varian 21EX Linac were used in the MC dose calculations. Results show that the CCC algorithm agrees well with AC to within ±1% for doses calculated in the lung phantoms, indicating that the AC, with 3-4 times less computing time required than CCC, is a good substitute for the CCC method. Comparing the CCC and AC with MC, dose deviations are found when ρ e,lung are ⩽0.1-0.3. The degree of deviation depends on the photon beam energy and field size, and is relatively large when high-energy photon beams with small field are used. For the penumbra widths (20%-80%), the CCC and AC agree well with MC for the "Slab" and "Cube" phantoms with the lung volumes at the central beam axis (CAX). However, deviations >2mm occur in the "Column" phantoms, with two lung volumes separated by a water column along the CAX, using the 18MV (4×4cm 2 ) photon beams with ρ e,lung ⩽0.1. © 2008 American Association of Physicists in Medicine.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Chen, L; Shen, C; Wang, J
Purpose: To reduce cone beam CT (CBCT) imaging dose, we previously proposed a progressive dose control (PDC) scheme to employ temporal correlation between CBCT images at different fractions for image quality enhancement. A temporal non-local means (TNLM) method was developed to enhance quality of a new low-dose CBCT using existing high-quality CBCT. To enhance a voxel value, the TNLM method searches for similar voxels in a window. Due to patient deformation among the two CBCTs, a large searching window was required, reducing image quality and computational efficiency. This abstract proposes a deformation-assisted TNLM (DA-TNLM) method to solve this problem. Methods:more » For a low-dose CBCT to be enhanced using a high-quality CBCT, we first performed deformable image registration between the low-dose CBCT and the high-quality CBCT to approximately establish voxel correspondence between the two. A searching window for a voxel was then set based on the deformation vector field. Specifically, the search window for each voxel was shifted by the deformation vector. A TNLM step was then applied using only voxels within this determined window to correct image intensity at the low-dose CBCT. Results: We have tested the proposed scheme on simulated CIRS phantom data and real patient data. The CITS phantom was scanned on Varian onboard imaging CBCT system with coach shifting and dose reducing for each time. The real patient data was acquired in four fractions with dose reduced from standard CBCT dose to 12.5% of standard dose. It was found that the DA-TNLM method can reduce total dose by over 75% on average in the first four fractions. Conclusion: We have developed a PDC scheme which can enhance the quality of image scanned at low dose using a DA-TNLM method. Tests in phantom and patient studies demonstrated promising results.« less
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NASA Astrophysics Data System (ADS)
Tanny, Sean
The advent of high-energy linear accelerators for dedicated medical use in the 1950's by Henry Kaplan and the Stanford University physics department began a revolution in radiation oncology. Today, linear accelerators are the standard of care for modern radiation therapy and can generate high-energy beams that can produce tens of Gy per minute at isocenter. This creates a need for a large amount of shielding material to properly protect members of the public and hospital staff. Standardized vault designs and guidance on shielding properties of various materials are provided by the National Council on Radiation Protection (NCRP) Report 151. However, physicists are seeking ways to minimize the footprint and volume of shielding material needed which leads to the use of non-standard vault configurations and less-studied materials, such as high-density concrete. The University of Toledo Dana Cancer Center has utilized both of these methods to minimize the cost and spatial footprint of the requisite radiation shielding. To ensure a safe work environment, computer simulations were performed to verify the attenuation properties and shielding workloads produced by a variety of situations where standard recommendations and guidance documents were insufficient. This project studies two areas of concern that are not addressed by NCRP 151, the radiation shielding workload for the vault door with a non-standard design, and the attenuation properties of high-density concrete for both photon and neutron radiation. Simulations have been performed using a Monte-Carlo code produced by the Los Alamos National Lab (LANL), Monte Carlo Neutrons, Photons 5 (MCNP5). Measurements have been performed using a shielding test port designed into the maze of the Varian Edge treatment vault.
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Determination of the optimal tolerance for MLC positioning in sliding window and VMAT techniques
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hernandez, V., E-mail: vhernandezmasgrau@gmail.com; Abella, R.; Calvo, J. F.
2015-04-15
Purpose: Several authors have recommended a 2 mm tolerance for multileaf collimator (MLC) positioning in sliding window treatments. In volumetric modulated arc therapy (VMAT) treatments, however, the optimal tolerance for MLC positioning remains unknown. In this paper, the authors present the results of a multicenter study to determine the optimal tolerance for both techniques. Methods: The procedure used is based on dynalog file analysis. The study was carried out using seven Varian linear accelerators from five different centers. Dynalogs were collected from over 100 000 clinical treatments and in-house software was used to compute the number of tolerance faults as amore » function of the user-defined tolerance. Thus, the optimal value for this tolerance, defined as the lowest achievable value, was investigated. Results: Dynalog files accurately predict the number of tolerance faults as a function of the tolerance value, especially for low fault incidences. All MLCs behaved similarly and the Millennium120 and the HD120 models yielded comparable results. In sliding window techniques, the number of beams with an incidence of hold-offs >1% rapidly decreases for a tolerance of 1.5 mm. In VMAT techniques, the number of tolerance faults sharply drops for tolerances around 2 mm. For a tolerance of 2.5 mm, less than 0.1% of the VMAT arcs presented tolerance faults. Conclusions: Dynalog analysis provides a feasible method for investigating the optimal tolerance for MLC positioning in dynamic fields. In sliding window treatments, the tolerance of 2 mm was found to be adequate, although it can be reduced to 1.5 mm. In VMAT treatments, the typically used 5 mm tolerance is excessively high. Instead, a tolerance of 2.5 mm is recommended.« less
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W. W. Hansen, Microwave Physics, and Silicon Valley
NASA Astrophysics Data System (ADS)
Leeson, David
2009-03-01
The Stanford physicist W. W. Hansen (b. 1909, AB '29 and PhD '32, MIT post-doc 1933-4, Prof. physics '35-'49, d. 1949) played a seminal role in the development of microwave electronics. His contributions underlay Silicon Valley's postwar ``microwave'' phase, when numerous companies, acknowledging their unique scientific debt to Hansen, flourished around Stanford University. As had the prewar ``radio'' companies, they furthered the regional entrepreneurial culture and prepared the ground for the later semiconductor and computer developments we know as Silicon Valley. In the 1930's, Hansen invented the cavity resonator. He applied this to his concept of the radio-frequency (RF) linear accelerator and, with the Varian brothers, to the invention of the klystron, which made microwave radar practical. As WWII loomed, Hansen was asked to lecture on microwaves to the physicists recruited to the MIT Radiation Laboratory. Hansen's ``Notes on Microwaves,'' the Rad Lab ``bible'' on the subject, had a seminal impact on subsequent works, including the Rad Lab Series. Because of Hansen's failing health, his postwar work, and MIT-Stanford rivalries, the Notes were never published, languishing as an underground classic. I have located remaining copies, and will publish the Notes with a biography honoring the centenary of Hansen's birth. After the war, Hansen founded Stanford's Microwave Laboratory to develop powerful klystrons and linear accelerators. He collaborated with Felix Bloch in the discovery of nuclear magnetic resonance. Hansen experienced first-hand Stanford's evolution from its depression-era physics department to corporate, then government funding. Hansen's brilliant career was cut short by his death in 1949, after his induction in the National Academy of Sciences. His ideas were carried on in Stanford's two-mile long linear accelerator and the development of Silicon Valley.
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Comparative performance evaluation of a new a-Si EPID that exceeds quad high-definition resolution.
McConnell, Kristen A; Alexandrian, Ara; Papanikolaou, Niko; Stathakis, Sotiri
2018-01-01
Electronic portal imaging devices (EPIDs) are an integral part of the radiation oncology workflow for treatment setup verification. Several commercial EPID implementations are currently available, each with varying capabilities. To standardize performance evaluation, Task Group Report 58 (TG-58) and TG-142 outline specific image quality metrics to be measured. A LinaTech Image Viewing System (IVS), with the highest commercially available pixel matrix (2688x2688 pixels), was independently evaluated and compared to an Elekta iViewGT (1024x1024 pixels) and a Varian aSi-1000 (1024x768 pixels) using a PTW EPID QC Phantom. The IVS, iViewGT, and aSi-1000 were each used to acquire 20 images of the PTW QC Phantom. The QC phantom was placed on the couch and aligned at isocenter. The images were exported and analyzed using the epidSoft image quality assurance (QA) software. The reported metrics were signal linearity, isotropy of signal linearity, signal-tonoise ratio (SNR), low contrast resolution, and high-contrast resolution. These values were compared between the three EPID solutions. Computed metrics demonstrated comparable results between the EPID solutions with the IVS outperforming the aSi-1000 and iViewGT in the low and high-contrast resolution analysis. The performance of three commercial EPID solutions have been quantified, evaluated, and compared using results from the PTW QC Phantom. The IVS outperformed the other panels in low and high-contrast resolution, but to fully realize the benefits of the IVS, the selection of the monitor on which to view the high-resolution images is important to prevent down sampling and visual of resolution.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wong, Olive; Chan, Biu; Moseley, Joanne
Purpose: We have developed a semi-automated dose accumulation workflow for Head and Neck Cancer (HNC) patients to evaluate volumetric and dosimetric changes that take place during radiotherapy. This work will be used to assess how dosimetric changes affect both toxicity and disease control, hence inform the feasibility and design of a prospective HNC adaptive trial. Methods: RayStation 4.5.2 features deformable image registration (DIR), where structures already defined on the planning CT image set can be deformably mapped onto cone-beam computed tomography (CBCT) images, accounting for daily treatment set-up shifts and changes in patient anatomy. The daily delivered dose can bemore » calculated on each CBCT and mapped back to the planning CT to allow dose accumulation. The process is partially automated using Python scripts developed in collaboration with RaySearch. Results: To date we have performed dose accumulation on 18 HNC patients treated at our institution during 2013–2015 under REB approval. Our semi-automated process establishes clinical feasibility. Generally, dose accumulation for the entire treatment course of one case takes 60–120 minutes: importing all CBCTs requires 20–30 minutes as each patient has 30 to 40 treated fractions; image registration and dose accumulation require 60–90 minutes. This is in contrast to the process without automated scripts where dose accumulation alone would take 3–5 hours. Conclusions: We have developed a reliable workflow for retrospective dose tracking in HNC using RayStation. The process has been validated for HNC patients treated on both Elekta and Varian linacs with CBCTs acquired on XVI and OBI platforms respectively.« less
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NASA Astrophysics Data System (ADS)
Didierlaurent, D.; Ribes, S.; Batatia, H.; Jaudet, C.; Dierickx, L. O.; Zerdoud, S.; Brillouet, S.; Caselles, O.; Courbon, F.
2012-12-01
This study assesses the accuracy of prospective phase-gated PET/CT data binning and presents a retrospective data binning method that improves image quality and consistency. Respiratory signals from 17 patients who underwent 4D PET/CT were analysed to evaluate the reproducibility of temporal triggers used for the standard phase-based gating method. Breathing signals were reprocessed to implement retrospective PET data binning. The mean and standard deviation of time lags between automatic triggers provided by the Real-time Position Management (RPM, Varian) gating device and inhalation peaks derived from respiratory curves were computed for each patient. The total number of respiratory cycles available for 4D PET/CT according to the binning mode (prospective versus retrospective) was compared. The maximum standardized uptake value (SUVmax), biological tumour volume (BTV) and tumour trajectory measures were determined from the PET/CT images of five patients. Compared to retrospective binning (RB), prospective gating approach led to (i) a significant loss in breathing cycles (15%) and (ii) the inconsistency of data binning due to temporal dispersion of triggers (average 396 ms). Consequently, tumour characterization could be impacted. In retrospective mode, SUVmax was up to 27% higher, where no significant difference appeared in BTV. In addition, prospective mode gave an inconsistent spatial location of the tumour throughout the bins. Improved consistency with breathing patterns and greater motion amplitude of the tumour centroid were observed with retrospective mode. The detection of the tumour motion and trajectory was improved also for small temporal dispersion of triggers. This study shows that the binning mode could have a significant impact on 4D PET images. The consistency of triggers with breathing signals should be checked before clinical use of gated PET/CT images, and our RB method improves 4D PET/CT image quantification.
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NASA Astrophysics Data System (ADS)
Siewerdsen, J. H.; Daly, M. J.; Bachar, G.; Moseley, D. J.; Bootsma, G.; Brock, K. K.; Ansell, S.; Wilson, G. A.; Chhabra, S.; Jaffray, D. A.; Irish, J. C.
2007-03-01
High-performance intraoperative imaging is essential to an ever-expanding scope of therapeutic procedures ranging from tumor surgery to interventional radiology. The need for precise visualization of bony and soft-tissue structures with minimal obstruction to the therapy setup presents challenges and opportunities in the development of novel imaging technologies specifically for image-guided procedures. Over the past ~5 years, a mobile C-arm has been modified in collaboration with Siemens Medical Solutions for 3D imaging. Based upon a Siemens PowerMobil, the device includes: a flat-panel detector (Varian PaxScan 4030CB); a motorized orbit; a system for geometric calibration; integration with real-time tracking and navigation (NDI Polaris); and a computer control system for multi-mode fluoroscopy, tomosynthesis, and cone-beam CT. Investigation of 3D imaging performance (noise-equivalent quanta), image quality (human observer studies), and image artifacts (scatter, truncation, and cone-beam artifacts) has driven the development of imaging techniques appropriate to a host of image-guided interventions. Multi-mode functionality presents a valuable spectrum of acquisition techniques: i.) fluoroscopy for real-time 2D guidance; ii.) limited-angle tomosynthesis for fast 3D imaging (e.g., ~10 sec acquisition of coronal slices containing the surgical target); and iii.) fully 3D cone-beam CT (e.g., ~30-60 sec acquisition providing bony and soft-tissue visualization across the field of view). Phantom and cadaver studies clearly indicate the potential for improved surgical performance - up to a factor of 2 increase in challenging surgical target excisions. The C-arm system is currently being deployed in patient protocols ranging from brachytherapy to chest, breast, spine, and head and neck surgery.
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SU-F-J-48: Effect of Scan Length On Magnitude of Imaging Dose in KV CBCT
DOE Office of Scientific and Technical Information (OSTI.GOV)
Deshpande, S; Naidu, S; Sutar, A
Purpose: To study effect of scan length on magnitude of imaging dose deposition in Varian kV CBCT for head & neck and pelvis CBCT. Methods: To study effect of scan length we measured imaging dose at depth of 8 cm for head and neck Cone Beam Computed Tomography (CBCT) acquisition ( X ray beam energy is used 100kV and 200 degree of gantry rotation) and at 16 cm depth for pelvis CBCT acquisition ( X ray beam energy used is 125 kV and 360 degree of gantry rotation) in specially designed phantom. We used farmer chamber which was calibrated inmore » kV X ray range for measurements .Dose was measured with default field size, and reducing field size along y direction to 10 cm and 5 cm. Results: As the energy of the beam decreases the scattered radiation increases and this contributes significantly to the dose deposited in the patient. By reducing the scan length to 10 Cm from default 20.6 cm we found a dose reduction of 14% for head and neck CBCT protocol and a reduction of 26% for pelvis CBCT protocol. Similarly for a scan length of 5cm compared to default the dose reduction in head and neck CBCT protocol is 36% while in the pelvis CBCT protocol the dose reduction is 50%. Conclusion: By limiting the scan length we can control the scatter radiation generated and hence the dose to the patient. However the variation in dose reduction for same length used in two protocols is because of the scan geometry. The pelvis CBCT protocol uses a full rotation and head and neck CBCT protocol uses partial rotation.« less
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Bednarz, Bryan; Hancox, Cindy; Xu, X George
2012-01-01
There is growing concern about radiation-induced second cancers associated with radiation treatments. Particular attention has been focused on the risk to patients treated with intensity-modulated radiation therapy (IMRT) due primarily to increased monitor units. To address this concern we have combined a detailed medical linear accelerator model of the Varian Clinac 2100 C with anatomically realistic computational phantoms to calculate organ doses from selected treatment plans. This paper describes the application to calculate organ-averaged equivalent doses using a computational phantom for three different treatments of prostate cancer: a 4-field box treatment, the same box treatment plus a 6-field 3D-CRT boost treatment and a 7-field IMRT treatment. The equivalent doses per MU to those organs that have shown a predilection for second cancers were compared between the different treatment techniques. In addition, the dependence of photon and neutron equivalent doses on gantry angle and energy was investigated. The results indicate that the box treatment plus 6-field boost delivered the highest intermediate- and low-level photon doses per treatment MU to the patient primarily due to the elevated patient scatter contribution as a result of an increase in integral dose delivered by this treatment. In most organs the contribution of neutron dose to the total equivalent dose for the 3D-CRT treatments was less than the contribution of photon dose, except for the lung, esophagus, thyroid and brain. The total equivalent dose per MU to each organ was calculated by summing the photon and neutron dose contributions. For all organs non-adjacent to the primary beam, the equivalent doses per MU from the IMRT treatment were less than the doses from the 3D-CRT treatments. This is due to the increase in the integral dose and the added neutron dose to these organs from the 18 MV treatments. However, depending on the application technique and optimization used, the required MU values for IMRT treatments can be two to three times greater than 3D CRT. Therefore, the total equivalent dose in most organs would be higher from the IMRT treatment compared to the box treatment and comparable to the organ doses from the box treatment plus the 6-field boost. This is the first time when organ dose data for an adult male patient of the ICRP reference anatomy have been calculated and documented. The tools presented in this paper can be used to estimate the second cancer risk to patients undergoing radiation treatment. PMID:19671968
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NASA Astrophysics Data System (ADS)
Bednarz, Bryan; Hancox, Cindy; Xu, X. George
2009-09-01
There is growing concern about radiation-induced second cancers associated with radiation treatments. Particular attention has been focused on the risk to patients treated with intensity-modulated radiation therapy (IMRT) due primarily to increased monitor units. To address this concern we have combined a detailed medical linear accelerator model of the Varian Clinac 2100 C with anatomically realistic computational phantoms to calculate organ doses from selected treatment plans. This paper describes the application to calculate organ-averaged equivalent doses using a computational phantom for three different treatments of prostate cancer: a 4-field box treatment, the same box treatment plus a 6-field 3D-CRT boost treatment and a 7-field IMRT treatment. The equivalent doses per MU to those organs that have shown a predilection for second cancers were compared between the different treatment techniques. In addition, the dependence of photon and neutron equivalent doses on gantry angle and energy was investigated. The results indicate that the box treatment plus 6-field boost delivered the highest intermediate- and low-level photon doses per treatment MU to the patient primarily due to the elevated patient scatter contribution as a result of an increase in integral dose delivered by this treatment. In most organs the contribution of neutron dose to the total equivalent dose for the 3D-CRT treatments was less than the contribution of photon dose, except for the lung, esophagus, thyroid and brain. The total equivalent dose per MU to each organ was calculated by summing the photon and neutron dose contributions. For all organs non-adjacent to the primary beam, the equivalent doses per MU from the IMRT treatment were less than the doses from the 3D-CRT treatments. This is due to the increase in the integral dose and the added neutron dose to these organs from the 18 MV treatments. However, depending on the application technique and optimization used, the required MU values for IMRT treatments can be two to three times greater than 3D CRT. Therefore, the total equivalent dose in most organs would be higher from the IMRT treatment compared to the box treatment and comparable to the organ doses from the box treatment plus the 6-field boost. This is the first time when organ dose data for an adult male patient of the ICRP reference anatomy have been calculated and documented. The tools presented in this paper can be used to estimate the second cancer risk to patients undergoing radiation treatment.
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Dosimetric comparison of Acuros XB, AAA, and XVMC in stereotactic body radiotherapy for lung cancer.
Tsuruta, Yusuke; Nakata, Manabu; Nakamura, Mitsuhiro; Matsuo, Yukinori; Higashimura, Kyoji; Monzen, Hajime; Mizowaki, Takashi; Hiraoka, Masahiro
2014-08-01
To compare the dosimetric performance of Acuros XB (AXB), anisotropic analytical algorithm (AAA), and x-ray voxel Monte Carlo (XVMC) in heterogeneous phantoms and lung stereotactic body radiotherapy (SBRT) plans. Water- and lung-equivalent phantoms were combined to evaluate the percentage depth dose and dose profile. The radiation treatment machine Novalis (BrainLab AG, Feldkirchen, Germany) with an x-ray beam energy of 6 MV was used to calculate the doses in the composite phantom at a source-to-surface distance of 100 cm with a gantry angle of 0°. Subsequently, the clinical lung SBRT plans for the 26 consecutive patients were transferred from the iPlan (ver. 4.1; BrainLab AG) to the Eclipse treatment planning systems (ver. 11.0.3; Varian Medical Systems, Palo Alto, CA). The doses were then recalculated with AXB and AAA while maintaining the XVMC-calculated monitor units and beam arrangement. Then the dose-volumetric data obtained using the three different radiation dose calculation algorithms were compared. The results from AXB and XVMC agreed with measurements within ± 3.0% for the lung-equivalent phantom with a 6 × 6 cm(2) field size, whereas AAA values were higher than measurements in the heterogeneous zone and near the boundary, with the greatest difference being 4.1%. AXB and XVMC agreed well with measurements in terms of the profile shape at the boundary of the heterogeneous zone. For the lung SBRT plans, AXB yielded lower values than XVMC in terms of the maximum doses of ITV and PTV; however, the differences were within ± 3.0%. In addition to the dose-volumetric data, the dose distribution analysis showed that AXB yielded dose distribution calculations that were closer to those with XVMC than did AAA. Means ± standard deviation of the computation time was 221.6 ± 53.1 s (range, 124-358 s), 66.1 ± 16.0 s (range, 42-94 s), and 6.7 ± 1.1 s (range, 5-9 s) for XVMC, AXB, and AAA, respectively. In the phantom evaluations, AXB and XVMC agreed better with measurements than did AAA. Calculations differed in the density-changing zones (substance boundaries) between AXB/XVMC and AAA. In the lung SBRT cases, a comparative analysis of dose-volumetric data and dose distributions with XVMC demonstrated that the AXB provided better agreement with XVMC than AAA. The computation time of AXB was faster than that of XVMC; therefore, AXB has better balance in terms of the dosimetric performance and computation speed for clinical use than XVMC.
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Photon spectrum and absorbed dose in brain tumor.
Vega-Carrillo, Hector Rene; Silva-Sanchez, Angeles; Rivera-Montalvo, Teodoro
2016-11-01
Using Monte Carlo methods a BOMAB phantom inside a treatment hall with a brain tumor nearby the pituitary gland was treated with photons produced by a Varian 6MV linac. The photon spectrum and the absorbed dose were calculated in the tumor, pituitary gland and the head. The treatment beam was collimated to illuminate only the tumor volume; however photons were noticed in the gland. Photon fluence reaching the tumor is and 15.7 times larger than the fluence in the pituitary gland, on the other hand the absorbed dose in the tumor is 37.1 times larger than the dose in the gland because photons that reach the pituitary gland are scattered, by the head and the tumor, through Compton effect. Copyright © 2016 Elsevier Ltd. All rights reserved.
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Meusy, J J; Martin, G; Soyez, D; van Deijnen, J E; Gallo, J M
1987-09-01
Immunochemical investigations, using dot immunobinding assay (DIA) and enzyme-linked immunosorbent assay (ELISA), and immunocytochemical studies reveal the following new information about crustacean vitellogenesis-inhibiting hormone (VIH): (1) The structure of VIH is sufficiently different from that of the other sinus gland neuropeptides to allow a selective recognition of VIH by polyclonal antibodies. (2) From immunochemical criteria, VIH does not seem strictly species specific. The antisera raised against VIH of Homarus americanus cross-react with sinus gland extracts of Palaemonetes varians, Palaemon serratus, Macrobrachium rosenbergii, Carcinus maenas, and Porcellio dilatatus. (3) In the sinus gland of H. americanus, VIH immunoreactivity is localized mainly in electron-dense granules of medium size (110-185 nm in diameter) while, in P. dilatatus, the labeling is mostly on the largest granules (200-270 nm in diameter).
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Improving a scissor-action couch for conformal arc radiotherapy and radiosurgery.
Li, Kaile; Yu, Cedric X; Ma, Lijun
2004-01-01
We have developed a method to improve the setup accuracy of a Varian Clinac 6/100 couch for delivering conformal arc therapy using a tertiary micro multileaf collimator (MLC) system. Several immobilization devices have been developed to improve the mechanical stability and isocenter alignment of the couch: turn-knob harnesses, double-track alignment plates, and a drop-in rod that attaches the couch to the concrete floor. These add-on components minimize the intercomponent motion of the couch's scissor elevator, which allows consistent treatment setup. The accuracy of our isocenter couch alignment is an improvement over the above devices, within 1 mm of their accuracy. The couch has been used with over 15 patients and with over 50 modulated conformal arc treatment deliveries at our institution.
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Effect of Time Lenght Fermentation to Katsuobushi Oxidation Rate As Fish Flavor Based
NASA Astrophysics Data System (ADS)
Amalia, U.; Rianingsih, L.; Wijayanti, I.
2018-02-01
Katsuobushi or dried smoked skipjack had a distinctive flavor and widely used in traditional Japanese cuisine. This study aimed to evaluate the oxidation rate of Katsuobushi with different lenght fermentation. The processing treatment of the product were the differences of fish boiling time (30 min and 60 min) and the lenght of fermentation: 1 week, 2 weeks and 3 weeks. The glutamic acid content, the oxidation rate (thiobarbituric acid and peroxide value) and Total Plate Count of katsuobushi were analyzed statistically using analysis of varians. Significant differences were found among 3 weeks of fermentation compare to 1 weeks fermentation (P < 0.05). The conclusion of this study was katsuobushi with 60 min boiling and 3 weeks fermentation was potential to be developed become basic ingredients for the fish flavor.
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NASA Astrophysics Data System (ADS)
Sangeetha, S.; Sureka, C. S.
2017-06-01
The present study is focused to compare the characteristics of Varian Clinac 600 C/D flattened and unflattened 6 MV photon beams for small field dosimetry using EGSnrc Monte Carlo Simulation since the small field dosimetry is considered to be the most crucial and provoking task in the field of radiation dosimetry. A 6 MV photon beam of a Varian Clinac 600 C/D medical linear accelerator operates with Flattening Filter (FF) and Flattening-Filter-Free (FFF) mode for small field dosimetry were performed using EGSnrc Monte Carlo user codes (BEAMnrc and DOSXYZnrc) in order to calculate the beam characteristics using Educated-trial and error method. These includes: Percentage depth dose, lateral beam profile, dose rate delivery, photon energy spectra, photon beam uniformity, out-of-field dose, surface dose, penumbral dose and output factor for small field dosimetry (0.5×0.5 cm2 to 4×4 cm2) and are compared with magna-field sizes (5×5 cm2 to 40×40 cm2) at various depths. The results obtained showed that the optimized beam energy and Full-width-half maximum value for small field dosimetry and magna-field dosimetry was found to be 5.7 MeV and 0.13 cm for both FF and FFF beams. The depth of dose maxima for small field size deviates minimally for both FF and FFF beams similar to magna-fields. The depths greater than dmax depicts a steeper dose fall off in the exponential region for FFF beams comparing FF beams where its deviations gets increased with the increase in field size. The shape of the lateral beam profiles of FF and FFF beams varies remains similar for the small field sizes less than 4×4 cm2 whereas it varies in the case of magna-fields. Dose rate delivery for FFF beams shows an eminent increase with a two-fold factor for both small field dosimetry and magna-field sizes. The surface dose measurements of FFF beams for small field size were found to be higher whereas it gets lower for magna-fields than FF beam. The amount of out-of-field dose reduction gets increased with the increase in field size. It is also observed that the photon energy spectrum gets increased with the increase in field size for FFF beam mode. Finally, the output factors for FFF beams were relatively quite low for small field sizes than FF beams whereas it gets higher for magna-field sizes. From this study, it is concluded that the FFF beams depicted minimal deviations in the treatment field region irrespective to the normal tissue region for small field dosimetry compared to FF beams. The more prominent result observed from the study is that the shape of the beam profile remains similar for FF and FFF beams in the case of smaller field size that leads to more accurate treatment planning in the case of IMRT (Image-Guided Radiation Therapy), IGAT (Image-Guided Adaptive Radiation Therapy), SBRT (Stereotactic Body Radiation Therapy), SRS (Stereotactic Radio Surgery), and Tomotherapy techniques where homogeneous dose is not necessary. On the whole, the determination of dosimetric beam characteristics of Varian linac machine using Monte Carlo simulation provides accurate dose calculation as the clinical golden data.
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Maslowski, Alexander; Wang, Adam; Sun, Mingshan; Wareing, Todd; Davis, Ian; Star-Lack, Josh
2018-05-01
To describe Acuros ® CTS, a new software tool for rapidly and accurately estimating scatter in x-ray projection images by deterministically solving the linear Boltzmann transport equation (LBTE). The LBTE describes the behavior of particles as they interact with an object across spatial, energy, and directional (propagation) domains. Acuros CTS deterministically solves the LBTE by modeling photon transport associated with an x-ray projection in three main steps: (a) Ray tracing photons from the x-ray source into the object where they experience their first scattering event and form scattering sources. (b) Propagating photons from their first scattering sources across the object in all directions to form second scattering sources, then repeating this process until all high-order scattering sources are computed using the source iteration method. (c) Ray-tracing photons from scattering sources within the object to the detector, accounting for the detector's energy and anti-scatter grid responses. To make this process computationally tractable, a combination of analytical and discrete methods is applied. The three domains are discretized using the Linear Discontinuous Finite Elements, Multigroup, and Discrete Ordinates methods, respectively, which confer the ability to maintain the accuracy of a continuous solution. Furthermore, through the implementation in CUDA, we sought to exploit the parallel computing capabilities of graphics processing units (GPUs) to achieve the speeds required for clinical utilization. Acuros CTS was validated against Geant4 Monte Carlo simulations using two digital phantoms: (a) a water phantom containing lung, air, and bone inserts (WLAB phantom) and (b) a pelvis phantom derived from a clinical CT dataset. For these studies, we modeled the TrueBeam ® (Varian Medical Systems, Palo Alto, CA) kV imaging system with a source energy of 125 kVp. The imager comprised a 600 μm-thick Cesium Iodide (CsI) scintillator and a 10:1 one-dimensional anti-scatter grid. For the WLAB studies, the full-fan geometry without a bowtie filter was used (with and without the anti-scatter grid). For the pelvis phantom studies, a half-fan geometry with bowtie was used (with the anti-scatter grid). Scattered and primary photon fluences and energies deposited in the detector were recorded. The Acuros CTS and Monte Carlo results demonstrated excellent agreement. For the WLAB studies, the average percent difference between the Monte Carlo- and Acuros-generated scattered photon fluences at the face of the detector was -0.7%. After including the detector response, the average percent differences between the Monte Carlo- and Acuros-generated scatter fractions (SF) were -0.1% without the grid and 0.6% with the grid. For the digital pelvis simulation, the Monte Carlo- and Acuros-generated SFs agreed to within 0.1% on average, despite the scatter-to-primary ratios (SPRs) being as high as 5.5. The Acuros CTS computation time for each scatter image was ~1 s using a single GPU. Acuros CTS enables a fast and accurate calculation of scatter images by deterministically solving the LBTE thus offering a computationally attractive alternative to Monte Carlo methods. Part II describes the application of Acuros CTS to scatter correction of CBCT scans on the TrueBeam system. © 2018 American Association of Physicists in Medicine.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Constantin, Magdalena; Perl, Joseph; LoSasso, Tom
2011-07-15
Purpose: To create an accurate 6 MV Monte Carlo simulation phase space for the Varian TrueBeam treatment head geometry imported from cad (computer aided design) without adjusting the input electron phase space parameters. Methods: geant4 v4.9.2.p01 was employed to simulate the 6 MV beam treatment head geometry of the Varian TrueBeam linac. The electron tracks in the linear accelerator were simulated with Parmela, and the obtained electron phase space was used as an input to the Monte Carlo beam transport and dose calculations. The geometry components are tessellated solids included in geant4 as gdml (generalized dynamic markup language) files obtainedmore » via STEP (standard for the exchange of product) export from Pro/Engineering, followed by STEP import in Fastrad, a STEP-gdml converter. The linac has a compact treatment head and the small space between the shielding collimator and the divergent arc of the upper jaws forbids the implementation of a plane for storing the phase space. Instead, an IAEA (International Atomic Energy Agency) compliant phase space writer was implemented on a cylindrical surface. The simulation was run in parallel on a 1200 node Linux cluster. The 6 MV dose calculations were performed for field sizes varying from 4 x 4 to 40 x 40 cm{sup 2}. The voxel size for the 60x60x40 cm{sup 3} water phantom was 4x4x4 mm{sup 3}. For the 10x10 cm{sup 2} field, surface buildup calculations were performed using 4x4x2 mm{sup 3} voxels within 20 mm of the surface. Results: For the depth dose curves, 98% of the calculated data points agree within 2% with the experimental measurements for depths between 2 and 40 cm. For depths between 5 and 30 cm, agreement within 1% is obtained for 99% (4x4), 95% (10x10), 94% (20x20 and 30x30), and 89% (40x40) of the data points, respectively. In the buildup region, the agreement is within 2%, except at 1 mm depth where the deviation is 5% for the 10x10 cm{sup 2} open field. For the lateral dose profiles, within the field size for fields up to 30x30 cm{sup 2}, the agreement is within 2% for depths up to 10 cm. At 20 cm depth, the in-field maximum dose difference for the 30x30 cm{sup 2} open field is within 4%, while the smaller field sizes agree within 2%. Outside the field size, agreement within 1% of the maximum dose difference is obtained for all fields. The calculated output factors varied from 0.938{+-}0.015 for the 4x4 cm{sup 2} field to 1.088{+-}0.024 for the 40x40 cm{sup 2} field. Their agreement with the experimental output factors is within 1%. Conclusions: The authors have validated a geant4 simulated IAEA-compliant phase space of the TrueBeam linac for the 6 MV beam obtained using a high accuracy geometry implementation from cad. These files are publicly available and can be used for further research.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Polan, D; Kamp, J; Lee, JY
Purpose: To perform validation and commissioning of a commercial deformable image registration (DIR) algorithm (Velocity, Varian Medical Systems) for numerous clinical sites using single and multi-modality images. Methods: In this retrospective study, the DIR algorithm was evaluated for 10 patients in each of the following body sites: head and neck (HN), prostate, liver, and gynecological (GYN). HN DIRs were evaluated from planning (p)CT to re-pCT and pCTs to daily CBCTs using dice similarity coefficients (DSC) of corresponding anatomical structures. Prostate DIRs were evaluated from pCT to CBCTs using DSC and target registration error (TRE) of implanted RF beacons within themore » prostate. Liver DIRs were evaluated from pMR to pCT using DSC and TRE of vessel bifurcations. GYN DIRs were evaluated between fractionated brachytherapy MRIs using DSC of corresponding anatomical structures. Results: Analysis to date has given average DSCs for HN pCT-to-(re)pCT DIR for the brainstem, cochleas, constrictors, spinal canal, cord, esophagus, larynx, parotids, and submandibular glands as 0.88, 0.65, 0.67, 0.91, 0.77, 0.69, 0.77, 0.87, and 0.71, respectively. Average DSCs for HN pCT-to-CBCT DIR for the constrictors, spinal canal, esophagus, larynx, parotids, and submandibular glands were 0.64, 0.90, 0.62, 0.82, 0.75, and 0.69, respectively. For prostate pCT-to-CBCT DIR the DSC for the bladder, femoral heads, prostate, and rectum were 0.71, 0.82, 0.69, and 0.61, respectively. Average TRE using implanted beacons was 3.35 mm. For liver pCT-to-pMR, the average liver DSC was 0.94 and TRE was 5.26 mm. For GYN MR-to-MR DIR the DSC for the bladder, sigmoid colon, GTV, and rectum were 0.79, 0.58, 0.67, and 0.76, respectively. Conclusion: The Velocity DIR algorithm has been evaluated over a number of anatomical sites. This work functions to document the uncertainties in the DIR in the commissioning process so that these can be accounted for in the development of downstream clinical processes. This work was supported in part by a co-development agreement with Varian Medical Systems.« less
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SU-F-T-476: Performance of the AS1200 EPID for Periodic Photon Quality Assurance
DOE Office of Scientific and Technical Information (OSTI.GOV)
DeMarco, J; Fraass, B; Yang, W
2016-06-15
Purpose: To assess the dosimetric performance of a new amorphous silicon flat-panel electronic portal imaging device (EPID) suitable for high-intensity, flattening-filter-free delivery mode. Methods: An EPID-based QA suite was created with automation to periodically monitor photon central-axis output and two-dimensional beam profile constancy as a function of gantry angle and dose-rate. A Varian TrueBeamTM linear accelerator installed with Developer Mode was used to customize and deliver XML script routines for the QA suite using the dosimetry mode image acquisition for an aS1200 EPID. Automatic post-processing software was developed to analyze the resulting DICOM images. Results: The EPID was used tomore » monitor photon beam output constancy (central-axis), flatness, and symmetry over a period of 10 months for four photon beam energies (6x, 15x, 6xFFF, and 10xFFF). EPID results were consistent to those measured with a standard daily QA check device. At the four cardinal gantry angles, the standard deviation of the EPID central-axis output was <0.5%. Likewise, EPID measurements were independent for the wide range of dose rates (including up to 2400 mu/min for 10xFFF) studied with a standard deviation of <0.8% relative to the nominal dose rate for each energy. Also, profile constancy and field size measurements showed good agreement with the reference acquisition of 0° gantry angle and nominal dose rate. XML script files were also tested for MU linearity and picket-fence delivery. Using Developer Mode, the test suite was delivered in <60 minutes for all 4 photon energies with 4 dose rates per energy and 5 picket-fence acquisitions. Conclusion: Dosimetry image acquisition using a new EPID was found to be accurate for standard and high-intensity photon beams over a broad range of dose rates over 10 months. Developer Mode provided an efficient platform to customize the EPID acquisitions by using custom script files which significantly reduced the time. This work was funded in part by Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Gulam, M; Gardner, S; Zhao, B
2014-06-15
Purpose: To measure attenuation for modelling of the KVue Couchtop for 6X and 10X FFF SRS/SBRT treatment Methods: Treatment planning simulation studies were done using 6X FFF beams to estimate the dosimetric impact of KVue couchtops (including the Q-Fix IGRT [carbon fiber] and Calypso [nonconductive Kevlar material]) with a structure model obtained from a research workstation (Eclipse, advanced planning interface (API) v13). Prior to installation on the Varian Edge linac, the couchtop along with (Kevlar) rails were CT scanned with the rails at various positions. An additional scan with the couchtop 15cm above the CT table top was obtained withmore » 20cm solid water to facilitate precised/indexed data acquisition. Measurements for attenuation were obtained for field sizes of 2, 4 and 10 cm{sup 2} at 42 gantry angles including 6 pairs of opposing fields and other angles for oblique delivery where the beams traversed the couchtop and or rails. The delivery was fully automated with xml scripts running in developer mode. The results were then used to determine an accurate structure model for AAA (Eclipse v11) planning of IMRT and RapidArc delivery. Results: The planning simulation relative dose attenuation for oblique entry was not significantly different than the Exact IGRT or BrainLab iBeam couch except that the rails added 6% additional attenuation. The relative attenuation measurements for PA, PA (rails: inner position), oblique, oblique (rails: outer position), oblique (rails: inner position) were: −2.0%, −2.5%, −15.6%, −2.5%, −5.0% for 6X FFF and −1.4%, −1.5%, −12.2%, − 2.5%, −5.0% for 10X FFF with slight decrease in attenuation versus field size. A Couch structure model (with HU values) was developed. Calculation compared to measurement showed good agreement except for oblique (rails: outer position) where differences approached a magnitude of 6%. Conclusion: A model of the couch structures has been developed accounting for attenuation for FFF beams.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Masi, K; Ditman, M; Marsh, R
Purpose: There is potentially a wide variation in plan quality for a certain disease site, even for clinics located in the same system of hospitals. We have used a prostate-specific knowledge-based planning (KBP) model as a quality control tool to investigate the variation in prostate treatment planning across a network of affiliated radiation oncology departments. Methods: A previously created KBP model was applied to 10 patients each from 4 community-based clinics (Clinics A, B, C, and D). The KBP model was developed using RapidPlan (Eclipse v13.5, Varian Medical Systems) from 60 prostate/prostate bed IMRT plans that were originally planned usingmore » an in-house treatment planning system at the central institution of the community-based clinics. The dosimetric plan quality (target coverage and normal-tissue sparing) of each model-generated plan was compared to the respective clinically-used plan. Each community-based clinic utilized the same planning goals to develop the clinically-used plans that were used at the main institution. Results: Across all 4 clinics, the model-generated plans decreased the mean dose to the rectum by varying amounts (on average, 12.5, 2.6, 4.5, and 2.7 Gy for Clinics A, B, C, and D, respectively). The mean dose to the bladder also decreased with the model-generated plans (5.4, 2.3, 3.0, and 4.1 Gy, respectively). The KBP model also identified that target coverage (D95%) improvements were possible for for Clinics A, B, and D (0.12, 1.65, and 2.75%) while target coverage decreased by 0.72% for Clinic C, demonstrating potentially different trade-offs made in clinical plans at different institutions. Conclusion: Quality control of dosimetric plan quality across a system of radiation oncology practices is possible with knowledge-based planning. By using a quality KBP model, smaller community-based clinics can potentially identify the areas of their treatment plans that may be improved, whether it be in normal-tissue sparing or improved target coverage. M. Matuszak has research funding for KBP from Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Rottmann, J; Myronakis, M; Hu, Y
Purpose: Beams-eye-view imaging applications such as real-time soft-tissue motion estimation and MV-CBCT are hindered by the inherently low image contrast of electronic portal imaging devices (EPID) currently in clinical use. We investigate a cost effective scintillating glass that provides substantially increased detective quantum efficiency (DQE) and contrast to noise ratio (CNR). Methods: A pixelated scintillator prototype was built from LKH-5 glass. The array is 12mm thick; 42.4×42.4cm2 wide and features 1.51mm pixel pitch with 20µm separation (glue+septa). The LKH-5 array was mounted on the active matrix flat panel imager (AMPFI) of an AS-1200 (Varian) with the GdO2S2:Tb removed. A secondmore » AS-1200 was utilized as reference detector. The prototype EPID was characterized in terms of CNR, modulation transfer function (MTF) and DQE. Additionally, the visibility of various fiducial markers typically used in the clinic as well as a realistic 3D-printed lung tumor model was assessed. All items were placed in a 12cm thick solid water phantom. CNR is estimated using a Las Vegas contrast phantom, presampled MTF is estimated using a slanted slit technique and the DQE is calculated from measured normalized noise power spectra (NPS) and the MTF. Results: DQE(0) for the LKH-5 prototype increased by a factor of 8× to about 10%, compared to the AS-1200 equipped with its standard GdO2S2:Tb scintillator. CNR increased by a factor of 5.3×. Due to the pixel size the MTF50 decreased by about 55% to 0.23lp/mm. The visibility of all fiducial markers as well as the tumor model were however markedly improved in comparison to an acquisition with the same parameters using the GdO2S2:Tb scintillator. Conclusion: LKH-5 scintillating glasses allow the cost effective construction of thick pixelated scintillators for portal imaging which can yield a substantial increase in DQE and CNR. Soft tissue and fiducial marker visibility was found to be markedly improved. The project was supported in part by NIH grant R01CA188446-01 and a grant from Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ding, G; Yin, F; Ren, L
Purpose: In order to track the tumor movement for patient positioning verification during arc treatment delivery or in between 3D/IMRT beams for stereotactic body radiation therapy (SBRT), the limited-angle kV projections acquisition simultaneously during arc treatment delivery or in-between static treatment beams as the gantry moves to the next beam angle was proposed. The purpose of this study is to estimate additional imaging dose resulting from multiple tomosynthesis acquisitions in-between static treatment beams and to compare with that of a conventional kV-CBCT acquisition. Methods: kV imaging system integrated into Varian TrueBeam accelerators was modeled using EGSnrc Monte Carlo user code,more » BEAMnrc and DOSXYZnrc code was used in dose calculations. The simulated realistic kV beams from the Varian TrueBeam OBI 1.5 system were used to calculate dose to patient based on CT images. Organ doses were analyzed using DVHs. The imaging dose to patient resulting from realistic multiple tomosynthesis acquisitions with each 25–30 degree kV source rotation between 6 treatment beam gantry angles was studied. Results: For a typical lung SBRT treatment delivery much lower (20–50%) kV imaging doses from the sum of realistic six tomosynthesis acquisitions with each 25–30 degree x-ray source rotation between six treatment beam gantry angles were observed compared to that from a single CBCT image acquisition. Conclusion: This work indicates that the kV imaging in this proposed Limited-angle Intra-fractional Verification (LIVE) System for SBRT Treatments has a negligible imaging dose increase. It is worth to note that the MV imaging dose caused by MV projection acquisition in-between static beams in LIVE can be minimized by restricting the imaging to the target region and reducing the number of projections acquired. For arc treatments, MV imaging acquisition in LIVE does not add additional imaging dose as the MV images are acquired from treatment beams directly during the treatment.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wen, N; Glide-Hurst, C; Zhong, H
2014-06-15
Purpose: We evaluated the performance of two commercially available and one open source B-Spline deformable image registration (DIR) algorithms between T2-weighted MRI and treatment planning CT using the DICE indices. Methods: CT simulation (CT-SIM) and MR simulation (MR-SIM) for four prostate cancer patients were conducted on the same day using the same setup and immobilization devices. CT images (120 kVp, 500 mAs, voxel size = 1.1x1.1x3.0 mm3) were acquired using an open-bore CT scanner. T2-weighted Turbo Spine Echo (T2W-TSE) images (TE/TR/α = 80/4560 ms/90°, voxel size = 0.7×0.7×2.5 mm3) were scanned on a 1.0T high field open MR-SIM. Prostates, seminalmore » vesicles, rectum and bladders were delineated on both T2W-TSE and CT images by the attending physician. T2W-TSE images were registered to CT images using three DIR algorithms, SmartAdapt (Varian), Velocity AI (Velocity) and Elastix (Klein et al 2010) and contours were propagated. DIR results were evaluated quantitatively or qualitatively by image comparison and calculating organ DICE indices. Results: Significant differences in the contours of prostate and seminal vesicles were observed between MR and CT. On average, volume changes of the propagated contours were 5%, 2%, 160% and 8% for the prostate, seminal vesicles, bladder and rectum respectively. Corresponding mean DICE indices were 0.7, 0.5, 0.8, and 0.7. The intraclass correlation coefficient (ICC) was 0.9 among three algorithms for the Dice indices. Conclusion: Three DIR algorithms for CT/MR registration yielded similar results for organ propagation. Due to the different soft tissue contrasts between MRI and CT, organ delineation of prostate and SVs varied significantly, thus efforts to develop other DIR evaluation metrics are warranted. Conflict of interest: Submitting institution has research agreements with Varian Medical System and Philips Healthcare.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hardcastle, N; Booth, J; Caillet, V
Purpose: To assess endo-bronchial electromagnetic beacon insertion and to quantify the geometric accuracy of using beacons as a surrogate for tumour motion in real-time multileaf collimator (MLC) tracking of lung tumours. Methods: The LIGHT SABR trial is a world-first clinical trial in which the MLC leaves move with lung tumours in real time on a standard linear accelerator. Tracking is performed based on implanted electromagnetic beacons (CalypsoTM, Varian Medical Systems, USA) as a surrogate for tumour motion. Five patients have been treated and have each had three beacons implanted endo-bronchially under fluoroscopic guidance. The centre of mass (C.O.M) has beenmore » used to adapt the MLC in real-time. The geometric error in using the beacon C.O.M as a surrogate for tumour motion was measured by measuring the tumour and beacon C.O.M in all phases of the respiratory cycle of a 4DCT. The surrogacy error was defined as the difference in beacon and tumour C.O.M relative to the reference phase (maximum exhale). Results: All five patients have had three beacons successfully implanted with no migration between simulation and end of treatment. Beacon placement relative to tumour C.O.M varied from 14 to 74 mm and in one patient spanned two lobes. Surrogacy error was measured in each patient on the simulation 4DCT and ranged from 0 to 3 mm. Surrogacy error as measured on 4DCT was subject to artefacts in mid-ventilation phases. Surrogacy error was a function of breathing phase and was typically larger at maximum inhale. Conclusion: Beacon placement and thus surrogacy error is a major component of geometric uncertainty in MLC tracking of lung tumours. Surrogacy error must be measured on each patient and incorporated into margin calculation. Reduction of surrogacy error is limited by airway anatomy, however should be taken into consideration when performing beacon insertion and planning. This research is funded by Varian Medical Systems via a collaborative research agreement.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Chin, E; Hoppe, R; Million, L
2015-06-15
Purpose: Integration of coordinated robotic table motion with inversely-planned arc delivery has the potential to resolve table-top delivery limitations of large-field treatments such as Total Body Irradiation (TBI), Total Lymphoid Irradiation (TLI), and Cranial-Spinal Irradiation (CSI). We formulate the foundation for Trajectory Modulated Arc Therapy (TMAT), and using Varian Developer Mode capabilities, experimentally investigate its practical implementation for such techniques. Methods: A MATLAB algorithm was developed for inverse planning optimization of the table motion, MLC positions, and gantry motion under extended-SSD geometry. To maximize the effective field size, delivery trajectories for TMAT TBI were formed with the table rotated atmore » 270° IEC and dropped vertically to 152.5cm SSD. Preliminary testing of algorithm parameters was done through retrospective planning analysis. Robotic delivery was programmed using custom XML scripting on the TrueBeam Developer Mode platform. Final dose was calculated using the Eclipse AAA algorithm. Initial verification of delivery accuracy was measured using OSLDs on a solid water phantom of varying thickness. Results: A comparison of DVH curves demonstrated that dynamic couch motion irradiation was sufficiently approximated by static control points spaced in intervals of less than 2cm. Optimized MLC motion decreased the average lung dose to 68.5% of the prescription dose. The programmed irradiation integrating coordinated table motion was deliverable on a TrueBeam STx linac in 6.7 min. With the couch translating under an open 10cmx20cm field angled at 10°, OSLD measurements along the midline of a solid water phantom at depths of 3, 5, and 9cm were within 3% of the TPS AAA algorithm with an average deviation of 1.2%. Conclusion: A treatment planning and delivery system for Trajectory Modulated Arc Therapy of extended volumes has been established and experimentally demonstrated for TBI. Extension to other treatment techniques such as TLI and CSI is readily achievable through the developed platform. Grant Funding by Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Keehan, S; Franich, R; Taylor, M
Purpose: To determine the potential error involved in the interpretation of neutron measurements from medical linear accelerators (linacs) using TLD-600H and TLD-700H if standard AmBe and {sup 252}Cf neutron sources are used for calibration without proper inclusion of neutron energy spectrum information. Methods: The Kerma due to neutrons can be calculated from the energy released by various nuclear interactions (elastic and inelastic scatter, (n,α), (n,p), (n,d), (n,t), (n,2n), etc.). The response of each TLD can be considered the sum of the neutron and gamma components; each proportional to the Kerma. Using the difference between the measured TLD responses and themore » ratio of the calculated Kerma for each material, the neutron component of the response can be calculated. The Monte Carlo code MCNP6 has been used to calculate the neutron energy spectra resulting from photonuclear interactions in a Varian 21EX linac. TLDs have been exposed to the mixed (γ-n) field produced by a linac and AmBe and {sup 252}Cf standard neutron sources. Results: For dosimetry of neutrons from AmBe or {sup 252}Cf sources, assuming TLD-700H insensitivity to neutrons will Result in 10% or 20% overestimation of neutron doses respectively.For dosimetry of neutrons produced in a Varian 21EX, applying a calibration factor derived from a standard AmBe or {sup 252}Cf source will Result in an overestimation of neutron fluence, by as much as a factor of 47.The assumption of TLD-700H insensitivity to neutrons produced by linacs leads to a negligible error due to the extremely high Kerma ratio (600H/700H) of 3000 for the assumed neutron spectrum. Conclusion: Lithium-enriched TLDs calibrated with AmBe and/or {sup 252}Cf neutron sources are not accurate for use under the neutron energy spectrum produced by a medical linear accelerator.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Glaser, A; Andreozzi, J; Davis, S
Purpose: A novel optical dosimetry technique for the QA and verification of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) radiotherapy plans was investigated for the first time by capturing images of the induced Cherenkov radiation in water. Methods: An intensified CCD camera (ICCD) was used to acquire a two-dimensional (2D) projection image of the Cherenkov radiation induced by IMRT and VMAT plans, based on the Task Group 119 C-Shape geometry. Plans were generated using the Varian Eclipse treatment planning system (TPS) and delivered using 6 MV x-rays from a Varian TrueBeam Linear Accelerator (Linac) incident on a watermore » tank. The ICCD acquisition was gated to the Linac, operated for single pulse imaging, and binned to a resolution of 512×512 pixels. The resulting videos were analyzed temporally for regions of interest (ROI) covering the planning target volume (PTV) and organ at risk (OAR) and summed to obtain an overall light distribution, which was compared to the expected dose distribution from the TPS using a gammaindex analysis. Results: The chosen camera settings resulted in data at 23.5 frames per second. Temporal intensity plots of the PTV and OAR ROIs confirmed the preferential delivery of dose to the PTV versus the OAR, and the gamma analysis yielded 95.2% and 95.6% agreement between the light distribution and expected TPS dose distribution based upon a 3% / 3 mm dose difference and distance-to-agreement criterion for the IMRT and VMAT plans respectively. Conclusion: The results from this initial study demonstrate the first documented use of Cherenkov radiation for optical dosimetry of dynamic IMRT and VMAT treatment plans. The proposed modality has several potential advantages over alternative methods including the real-time nature of the acquisition, and upon future refinement may prove to be a robust and novel dosimetry method with both research and clinical applications. NIH R01CA109558 and R21EB017559.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Moseley, D; Dave, M
Purpose: Use Varian TrueBeam Developer mode to quantify the mechanical limits of the couch and to simulate 4D respiratory motion. Methods: An in-house MATLAB based GUI was created to make the BEAM XML files. The couch was moved in a triangular wave in the S/I direction with varying amplitudes (1mm, 5mm, 10mm, and 50mm) and periods (3s, 6s, and 9s). The periods were determined by specifying the speed. The theoretical positions were compared to the values recorded by the machine at 50 Hz. HD videos were taken for certain tests as external validation. 4D Respiratory motion was simulated by anmore » A/P MV beam being delivered while the couch moved in an elliptical manner. The ellipse had a major axis of 2 cm (S/I) and a minor axis of 1 cm (A/P). Results: The path planned by the TrueBeam deviated from the theoretical triangular form as the speed increased. Deviations were noticed starting at a speed of 3.33 cm/s (50mm amplitude, 6s period). The greatest deviation occurred in the 50mm- 3s sequence with a correlation value of −0.13 and a 27% time increase; the plan essentially became out of phase. Excluding these two, the plans had correlation values of 0.99. The elliptical sequence effectively simulated a respiratory pattern with a period of 6s. The period could be controlled by changing the speeds or the dose rate. Conclusion: The work first shows the quantification of the mechanical limits of the couch and the speeds at which the proposed plans begin to deviate. These limits must be kept in mind when programming other couch sequences. The methodology can be used to quantify the limits of other axes. Furthermore, the work shows the possibility of creating 4D respiratory simulations without using specialized phantoms or motion-platforms. This can be further developed to program patient-specific breathing patterns.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ono, K; Fujimoto, S; Akagi, Y
2014-06-01
Purpose: The aim of this dosimetric study was to develop 3D dose verification system for volumetric modulated arc therapy (VMAT) using polyacrylamide-based gel (PAGAT) dosimeter improved the sensitivity by magnesium chloride (MgCl{sub 2}). Methods: PAGAT gel containing MgCl{sub 2} as a sensitizer was prepared in this study. Methacrylic-acid-based gel (MAGAT) was also prepared to compare the dosimetric characteristics with PAGAT gel. The cylindrical glass vials (4 cm diameter, 12 cm length) filled with each polymer gel were irradiated with 6 MV photon beam using Novalis Tx linear accelerator (Varian/BrainLAB). The irradiated polymer gel dosimeters were scanned with Signa 1.5 Tmore » MRI system (GE), and dose calibration curves were obtained using T{sub 2} relaxation rate (R{sub 2} = 1/T{sub 2}). Dose rate (100-600 MU min{sup −1}) and fractionation (1-8 fractions) were varied. In addition, a cubic acrylic phantom (10 × 10 × 10 cm{sup 3}) filled with improved PAGAT gel inserted into the IMRT phantom (IBA) was irradiated with VMAT (RapidArc). C-shape structure was used for the VMAT planning by the Varian Eclipse treatment planning system (TPS). The dose comparison of TPS and measurements with the polymer gel dosimeter was accomplished by the gamma index analysis, overlaying the dose profiles for a set of data on selected planes using in-house developed software. Results: Dose rate and fractionation dependence of improved PAGAT gel were smaller than MAGAT gel. A high similarity was found by overlaying the dose profiles measured with improved PAGAT gel dosimeter and the TPS dose, and the mean pass rate of the gamma index analysis using 3%/3 mm criteria was achieved 90% on orthogonal planes for VMAT using improved PAGAT gel dosimeter. Conclusion: In-house developed 3D dose verification system using improved polyacrylamide-based gel dosimeter had a potential as an effective tool for VMAT QA.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, Y; Cai, J; Meltsner, S
2016-06-15
Purpose: The Varian tandem and ring applicators are used to deliver HDR Ir-192 brachytherapy for cervical cancer. The source path within the ring is hard to predict due to the larger interior ring lumen. Some studies showed the source could be several millimeters different from planned positions, while other studies demonstrated minimal dosimetric impact. A global shift can be applied to limit the effect of positioning offsets. The purpose of this study was to assess the necessities of implementing a global source shift using Monte Carlo (MC) simulations. Methods: The MCNP5 radiation transport code was used for all MC simulations.more » To accommodate TG-186 guidelines and eliminate inter-source attenuation, a BrachyVision plan with 10 dwell positions (0.5cm step sizes) was simulated as the summation of 10 individual sources with equal dwell times for simplification. To simplify the study, the tandem was also excluded from the MC model. Global shifts of ±0.1, ±0.3, ±0.5 cm were then simulated as distal and proximal from the reference positions. Dose was scored in water for all MC simulations and was normalized to 100% at the normalization point 0.5 cm from the cap in the ring plane. For dose comparison, Point A was 2 cm caudal from the buildup cap and 2 cm lateral on either side of the ring axis. With seventy simulations, 108 photon histories gave a statistical uncertainties (k=1) <2% for (0.1 cm)3 voxels. Results: Compared to no global shift, average Point A doses were 0.0%, 0.4%, and 2.2% higher for distal global shifts, and 0.4%, 2.8%, and 5.1% higher for proximal global shifts, respectively. The MC Point A doses differed by < 1% when compared to BrachyVision. Conclusion: Dose variations were not substantial for ±0.3 cm global shifts, which is common in clinical practice.« less
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SU-F-E-06: Dosimetric Characterization of Small Photons Beams of a Novel Linear Accelerator
DOE Office of Scientific and Technical Information (OSTI.GOV)
Almonte, A; Polanco, G; Sanchez, E
2016-06-15
Purpose: The aim of the present contribution was to measure the main dosimetric quantities of small fields produced by UNIQUE and evaluate its matching with the corresponding dosimetric data of one 21EX conventional linear accelerator (Varian) in operation at the same center. The second step was to evaluate comparative performance of the EDGE diode detector and the PinPoint micro-ionization chamber for dosimetry of small fields. Methods: UNIQUE is configured with MLC (120 leaves with 0.5 cm leaf width) and a single low photon energy of 6 MV. Beam data were measured with scanning EDGE diode detector (volume of 0.019 mm{supmore » 3}), a PinPoint micro-ionization chamber (PTW) and for larger fields (≥ 4×4cm{sup 2}) a PTW Semi flex chamber (0.125 cm{sup 3}) was used. The scanning system used was the 3D cylindrical tank manufactured by Sun Nuclear, Inc. The measurement of PDD and profiles were done at 100 cm SSD and 1.5 depth; the relative output factors were measured at 10 cm depth. Results: PDD and the profile data showed less than 1% variation between the two linear accelerators for fields size between 2×2 cm{sup 2} and 5×5cm{sup 2}. Output factor differences was less than 1% for field sizes between 3×3 cm{sup 2} and 10×10 cm{sup 2} and less of 1.5 % for fields of 1.5×1.5 cm{sup 2} and 2×2 cm{sup 2} respectively. The dmax value of the EDGE diode detector, measured from the PDD, was 8.347 mm for 0.5×0,5cm{sup 2} for UNIQUE. The performance of EDGE diode detector was comparable for all measurements in small fields. Conclusion: UNIQUE linear accelerator show similar dosimetrics characteristics as conventional 21EX Varian linear accelerator for small, medium and large field sizes.EDGE detector show good performance by measuring dosimetrics quantities in small fields typically used in IMRT and radiosurgery treatments.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Chibani, O; Tahanout, F; Ma, C
2016-06-15
Purpose: To commission a new MLC model for the GEPTS Monte Carlo system. The model is based on the concept of leaves and interleaves effective densities Methods: GEPTS is a Monte Carlo system to be used for external beam planning verification. GEPTS incorporates detailed photon and electron transport algorithms (Med.Phys. 29, 2002, 835). A new GEPTS model for the Varian Millennium MLC is presented. The model accounts for: 1) thick (1 cm) and thin (0.5 cm) leaves, 2) tongue-and-groove design, 3) High-Transmission (HT) and Low-Transmission (LT) interleaves, and 4) rounded leaf end. Leaf (and interleaf) height is set equal tomore » 6 cm. Instead of modeling air gaps, screw holes, and complex leaf heads, “effective densities” are assigned to: 1) thin leaves, 2) thick leaves, 3) HT-, and 4) LT-interleaves. Results: The new MLC model is used to calculate dose profiles for Closed-MLC and Tongue-and-Groove fields at 5 cm depth for 6, 10 and 15 MV Varian beams. Calculations are compared with 1) Pin-point ionization chamber transmission ratios and 2) EBT3 Radiochromic films. Pinpoint readings were acquired beneath thick and thin leaves, and HT and LT interleaves. The best fit of measured dose profiles was obtained for the following parameters: Thick-leaf density = 16.1 g/cc, Thin-leaf density = 17.2 g/cc; HT Interleaf density = 12.4 g/cc, LT Interleaf density = 14.3 g/cc; Interleaf thickness = 1.1 mm. Attached figures show comparison of calculated and measured transmission ratios for the 3 energies. Note this is the only study where transmission profiles are compared with measurements for 3 different energies. Conclusion: The new MLC model reproduces transmission measurements within 0.1%. The next step is to implement the MLC model for real plans and quantify the improvement in dose calculation accuracy gained using this model for IMRT plans with high modulation factors.« less
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SU-G-JeP1-06: Correlation of Lung Tumor Motion with Tumor Location Using Electromagnetic Tracking
DOE Office of Scientific and Technical Information (OSTI.GOV)
Muccigrosso, D; Maughan, N; Parikh, P
Purpose: It is well known that lung tumors move with respiration. However, most measurements of lung tumor motion have studied long treatment times with intermittent imaging; those populations may not necessarily represent conventional LINAC patients. We summarized the correlation between tumor motion and location in a multi-institutional trial with electromagnetic tracking, and identified the patient cohort that would most benefit from respiratory gating. Methods: Continuous electromagnetic transponder data (Varian Medical, Seattle, WA) of lung tumor motion was collected from 14 patients (214 total fractions) across 3 institutions during external beam radiation therapy in a prospective clinical trial (NCT01396551). External interventionmore » from the clinician, such as couch shifts, instructed breath-holds, and acquisition pauses, were manually removed from the 10 Hz tracking data according to recorded notes. The average three-dimensional displacement from the breathing cycle’s end-expiratory to end-inhalation phases (peak-to-peak distance) of the transponders’ isocenter was calculated for each patient’s treatment. A weighted average of each isocenter was used to assess the effects of location on motion. A total of 14 patients were included in this analysis, grouped by their transponders’ location in the lung: upper, medial, and lower. Results: 8 patients had transponders in the upper lung, and 3 patients each in the medial lobe and lower lung. The weighted average ± standard deviation of all peak-to-peak distances for each group was: 1.04 ± 0.39 cm in the lower lung, 0.56 ± 0.14 cm in the medial lung, and 0.30 ± 0.06 cm in the upper lung. Conclusion: Tumors in the lower lung are most susceptible to excessive motion and daily variation, and would benefit most from continuous motion tracking and gating. Those in the medial lobe might be at moderate risk. The upper lobes have limited motion. These results can guide different motion management strategies between lung tumor locations. This is part of an NIH-funded prospective clinical trial (NCT01396551), using an electromagnetic transponder tracking system and additional funding from Varian Medical (Seattle, WA).« less
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WE-G-BRA-02: SafetyNet: Automating Radiotherapy QA with An Event Driven Framework
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hadley, S; Kessler, M; Litzenberg, D
2015-06-15
Purpose: Quality assurance is an essential task in radiotherapy that often requires many manual tasks. We investigate the use of an event driven framework in conjunction with software agents to automate QA and eliminate wait times. Methods: An in house developed subscription-publication service, EventNet, was added to the Aria OIS to be a message broker for critical events occurring in the OIS and software agents. Software agents operate without user intervention and perform critical QA steps. The results of the QA are documented and the resulting event is generated and passed back to EventNet. Users can subscribe to those eventsmore » and receive messages based on custom filters designed to send passing or failing results to physicists or dosimetrists. Agents were developed to expedite the following QA tasks: Plan Revision, Plan 2nd Check, SRS Winston-Lutz isocenter, Treatment History Audit, Treatment Machine Configuration. Results: Plan approval in the Aria OIS was used as the event trigger for plan revision QA and Plan 2nd check agents. The agents pulled the plan data, executed the prescribed QA, stored the results and updated EventNet for publication. The Winston Lutz agent reduced QA time from 20 minutes to 4 minutes and provided a more accurate quantitative estimate of radiation isocenter. The Treatment Machine Configuration agent automatically reports any changes to the Treatment machine or HDR unit configuration. The agents are reliable, act immediately, and execute each task identically every time. Conclusion: An event driven framework has inverted the data chase in our radiotherapy QA process. Rather than have dosimetrists and physicists push data to QA software and pull results back into the OIS, the software agents perform these steps immediately upon receiving the sentinel events from EventNet. Mr Keranen is an employee of Varian Medical Systems. Dr. Moran’s institution receives research support for her effort for a linear accelerator QA project from Varian Medical Systems. Other quality projects involving her effort are funded by Blue Cross Blue Shield of Michigan, Breast Cancer Research Foundation, and the NIH.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Audet, C; Poffenbarger, B; Hwang, A
2015-06-15
Purpose: To investigate some limitations of single isocenter VMAT for cranial multiple met cases. Methods: A single isocenter VMAT plan (Varian, Eclipse AAA10 commissioned down to 1 cm) was designed for two 7mm diameter spherical targets in a rectangular Solid Water (Gammex) phantom. The targets were separated by a distance of 6cm and the isocenter was centered in one of the targets. The plan was delivered (Varian, Truebeam STx) three separate times with different artificial couch angle errors of 0, 0.5 and 1 degree. The coronal dose distributions were measured with calibrated EBT3 film placed at mid-phantom. EBT3 film dosimetrymore » was also performed on the delivery of separate multiple arc vmat plans to targets below 6mm in diameter. Results: Measurements of the sup/inf dose profiles through the high dose distributions show no movement of the central axis high dose region and shifts of the high dose region intended for the off-axis target. For the 1 degree rotation error, the high dose region was shifted 1.04mm from the target. This corresponds to the shift expected from triangulation (60mmxTan(1deg)=1.047mm). Furthermore, a streak of 10% interleaf leakage dose was observed and is likely a Result of the off axis target traveling a wide path such that a long length of MLC is exposed for the whole arc. The calculated dose was about 10% to 15% low compared to that measured on film for a 5mm diameter target. Conclusion: Judicious use of additional margin for off axis targets or limits on the span of multiple mets treated with one isocenter is recommended. The magnitude of the margin should be based on the rotational errors evaluated for the positioning system and the distance of the target from the isocenter. A lower limit of lesion size that can be accurately treated with VMAT should be determined.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ono, K; Fujimoto, S; Akagi, Y
Purpose: To evaluate the dosimetric impact of the interplay effect between multileaf collimator (MLC) movement and tumor respiratory motion during delivery of volumetric modulate arc therapy (VMAT) by using customized polymer gel dosimeter. Methods: Polyacrylamide-based gel dosimeter contained magnesium chloride as a sensitizer (iPAGAT) was used in this study. An excellent gas barrier PAN (BAREX) techno bottle (φ8 cm, 650 mL) filled with iPAGAT was set to the QUASAR™ respiratory motion phantom, and was moved with motion amplitudes of 1 and 2 cm with a 4 second period during VMAT delivery by the Novalis Tx linear accelerator (Varian/BrainLAB). Two sphericalmore » tumors with a 2 cm diameter (GTV1 and GTV2) were defined, and ITV1 (GTV1+1 cm) and ITV2 (GTV2+2 cm) with expansion in the superior-inferior (S-I) direction were also defined with simulated respiratory motion. PTV margin was 2 mm around the ITV considering the setup uncertainty. Two single arc VMAT plans with 30 Gy at 3 Gy per fraction (GTV: D98>100%, PTV: D95=100%) were generated by the Varian Eclipse treatment planning system. Three-dimensional dose distribution in iPAGAT was read out by the Signa 1.5T MRI system (GE), and was evaluated by dose-volume histogram (DVH) using in-house developed software. Results: According to DVH analysis by iPAGAT, D98 of GTV1 and GTV2 were more than 100% of the prescribed dose. In contrast, D95 of PTV1 and PTV2 were about 85% and 65%, respectively. Furthermore, low-to-intermediate dose was widespread with motion amplitude of 2 cm. Conclusion: DVH analysis using iPAGAT polymer gel dosimeter was performed in this study. As a result, interplay effect was negligible, since dose coverage of GTV was sufficient during VMAT delivery with simulated respiratory motion. However, the dose reduction of PTV and the spread of low-to-intermediate dose compared to the planned dose require scrupulous attention for large tumor respiratory motion.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Shea, S; Diak, A; Surucu, M
2015-06-15
Purpose: To investigate the effect of readout bandwidth and voxel size on the appearance of distortion artifacts caused by a titanium brachytherapy applicator. Methods: An acrylic phantom was constructed to rigidly hold a MR conditional, titanium Fletcher-Suit-Delclos-style applicator set (Varian Medical Systems) for imaging on CT (Philips Brilliance) and 1.5T MRI (Siemens Magnetom Aera). Several variants of MRI parameters were tried for 2D T2-weighted turbo spin echo imaging in comparison against the standard clinical protocol with the criteria to keep relative SNR loss less than 20% and imaging time as short as possible. Two 3D sequences were also used formore » comparison with similar parameters. The applicator tandem was segmented on axial CT images (0.4×0.4×1.5mm {sup 3} resolution) and the CT images were registered to the 3D MR images in Eclipse (Varian). The applicator volume was then overlaid on all MRI sets in 3D-Slicer and distances were measured from the tandem tip to the MRI artifact edge in right/left/superior and anterior/posterior/superior directions from coronal and sagittal 2D acquisitions, respectively, or 3D data reformats. Artifact regions were also manually contoured in coronal/sagittal orientations for area measurements. Results: As would be expected, reductions in voxel size and increases in readout bandwidth reduced artifact size (average max artifact length decreased by 0.95 mm and average max area decrease by 0.27 cm{sup 2}). Interestingly, bandwidth increases yielded reductions in area (0.19 cm{sup 2}) and in distance measurements (1 mm) even with voxel increases, as compared to a standard protocol. This could be useful when high performance protocols are not feasible due to long imaging times. Conclusion: We have characterized artifacts caused by cervical brachytherapy applicator across multiple sequence parameters at 1.5T. Future work will focus on finalizing an optimal protocol that balances artifact reduction with imaging time and then testing this new protocol in patients.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ferreyra, M; Salinas Aranda, F; Dodat, D
Purpose: To use end-to-end testing to validate a 6 MV high dose rate photon beam, configured for Eclipse AAA algorithm using Golden Beam Data (GBD), for SBRT treatments using RapidArc. Methods: Beam data was configured for Varian Eclipse AAA algorithm using the GBD provided by the vendor. Transverse and diagonals dose profiles, PDDs and output factors down to a field size of 2×2 cm2 were measured on a Varian Trilogy Linac and compared with GBD library using 2% 2mm 1D gamma analysis. The MLC transmission factor and dosimetric leaf gap were determined to characterize the MLC in Eclipse. Mechanical andmore » dosimetric tests were performed combining different gantry rotation speeds, dose rates and leaf speeds to evaluate the delivery system performance according to VMAT accuracy requirements. An end-to-end test was implemented planning several SBRT RapidArc treatments on a CIRS 002LFC IMRT Thorax Phantom. The CT scanner calibration curve was acquired and loaded in Eclipse. PTW 31013 ionization chamber was used with Keithley 35617EBS electrometer for absolute point dose measurements in water and lung equivalent inserts. TPS calculated planar dose distributions were compared to those measured using EPID and MapCheck, as an independent verification method. Results were evaluated with gamma criteria of 2% dose difference and 2mm DTA for 95% of points. Results: GBD set vs. measured data passed 2% 2mm 1D gamma analysis even for small fields. Machine performance tests show results are independent of machine delivery configuration, as expected. Absolute point dosimetry comparison resulted within 4% for the worst case scenario in lung. Over 97% of the points evaluated in dose distributions passed gamma index analysis. Conclusion: Eclipse AAA algorithm configuration of the 6 MV high dose rate photon beam using GBD proved efficient. End-to-end test dose calculation results indicate it can be used clinically for SBRT using RapidArc.« less
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Robar, J; Parsons, D; Berman, A; MacDonald, A
2012-06-01
This study demonstrates feasibility and advantages of volume of interest (VOI) cone beam CT (CBCT) imaging performed with an x-ray beam generated from 2.35 MeV electrons incident on a carbon linear accelerator target. The electron beam energy was reduced to 2.35 MeV in a Varian 21EX linear accelerator containing a 7.6 mm thick carbon x-ray target. Arbitrary imaging volumes were defined in the planning system to produce dynamic MLC sequences capable of tracking off-axis VOIs in phantoms. To reduce truncation artefacts, missing data in projection images were completed using a priori DRR information from the planning CT set. The feasibility of the approach was shown through imaging of an anthropomorphic phantom and the head-and-neck section of a lamb. TLD800 and EBT2 radiochromic film measurements were used to compare the VOI dose distributions with those for full-field techniques. CNR was measured for VOIs ranging from 4 to 15 cm diameter. The 2.35 MV/Carbon beam provides favorable CNR characteristics, although marked boundary and cupping artefacts arise due to truncation of projection data. These artefacts are largely eliminated using the DRR filling technique. Imaging dose was reduced by 5-10% and 75% inside and outside of the VOI, respectively, compared to full-field imaging for a cranial VOI. For the 2.35 MV/Carbon beam, CNR was shown to be approximately invariant with VOI dimension for bone and lung objects. This indicates that the advantage of the VOI approach with the low-Z target beam is substantial imaging dose reduction, not improvement of image quality. VOI CBCT using a 2.35 MV/Carbon beam is a feasible technique whereby a chosen imaging volume can be defined in the planning system and tracked during acquisition. The novel x-ray beam affords good CNR characteristics while imaging dose is localized to the chosen VOI. Funding for this project has been received from Varian Medical, Incorporated. © 2012 American Association of Physicists in Medicine.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Modiri, A; Gu, X; Sawant, A
2014-06-15
Purpose: We present a particle swarm optimization (PSO)-based 4D IMRT planning technique designed for dynamic MLC tracking delivery to lung tumors. The key idea is to utilize the temporal dimension as an additional degree of freedom rather than a constraint in order to achieve improved sparing of organs at risk (OARs). Methods: The target and normal structures were manually contoured on each of the ten phases of a 4DCT scan acquired from a lung SBRT patient who exhibited 1.5cm tumor motion despite the use of abdominal compression. Corresponding ten IMRT plans were generated using the Eclipse treatment planning system. Thesemore » plans served as initial guess solutions for the PSO algorithm. Fluence weights were optimized over the entire solution space i.e., 10 phases × 12 beams × 166 control points. The size of the solution space motivated our choice of PSO, which is a highly parallelizable stochastic global optimization technique that is well-suited for such large problems. A summed fluence map was created using an in-house B-spline deformable image registration. Each plan was compared with a corresponding, internal target volume (ITV)-based IMRT plan. Results: The PSO 4D IMRT plan yielded comparable PTV coverage and significantly higher dose—sparing for parallel and serial OARs compared to the ITV-based plan. The dose-sparing achieved via PSO-4DIMRT was: lung Dmean = 28%; lung V20 = 90%; spinal cord Dmax = 23%; esophagus Dmax = 31%; heart Dmax = 51%; heart Dmean = 64%. Conclusion: Truly 4D IMRT that uses the temporal dimension as an additional degree of freedom can achieve significant dose sparing of serial and parallel OARs. Given the large solution space, PSO represents an attractive, parallelizable tool to achieve globally optimal solutions for such problems. This work was supported through funding from the National Institutes of Health and Varian Medical Systems. Amit Sawant has research funding from Varian Medical Systems, VisionRT Ltd. and Elekta.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Lin, L; Huang, S; Kang, M
Purpose: Eclipse proton Monte Carlo AcurosPT 13.7 was commissioned and experimentally validated for an IBA dedicated PBS nozzle in water. Topas 1.3 was used to isolate the cause of differences in output and penumbra between simulation and experiment. Methods: The spot profiles were measured in air at five locations using Lynx. PTW-34070 Bragg peak chamber (Freiburg, Germany) was used to collect the relative integral Bragg peak for 15 proton energies from 100 MeV to 225 MeV. The phase space parameters (σx, σθ, ρxθ) number of protons per MU, energy spread and calculated mean energy provided by AcurosPT were identically implementedmore » into Topas. The absolute dose, profiles and field size factors measured using ionization chamber arrays were compared with both AcurosPT and Topas. Results: The beam spot size, σx, and the angular spread, σθ, in air were both energy-dependent: in particular, the spot size in air at isocentre ranged from 2.8 to 5.3 mm, and the angular spread ranged from 2.7 mrad to 6 mrad. The number of protons per MU increased from ∼9E7 at 100 MeV to ∼1.5E8 at 225 MeV. Both AcurosPT and TOPAS agree with experiment within 2 mm penumbra difference or 3% dose difference for scenarios including central axis depth dose and profiles at two depths in multi-spot square fields, from 40 to 200 mm, for all the investigated single-energy and multi-energy beams, indicating clinically acceptable source model and radiation transport algorithm in water. Conclusion: By comparing measured data and TOPAS simulation using the same source model, the AcurosPT 13.7 was validated in water within 2 mm penumbra difference or 3% dose difference. Benchmarks versus an independent Monte Carlo code are recommended to study the agreement in output, filed size factors and penumbra differences. This project is partially supported by the Varian grant under the master agreement between University of Pennsylvania and Varian.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wilson, B; Vancouver Cancer Centre, Vancouver, BC; Gete, E
2016-06-15
Purpose: This work investigates the dosimetric accuracy of a trajectory based delivery technique in which an optimized radiation beam is delivered along a Couch-Gantry trajectory that is formed by simultaneous rotation of the linac gantry and the treatment couch. Methods: Nine trajectory based cranial SRS treatment plans were created using in-house optimization software. The plans were calculated for delivery on the TrueBeam STx linac with 6MV photon beam. Dose optimization was performed along a user-defined trajectory using MLC modulation, dose rate modulation and jaw tracking. The pre-defined trajectory chosen for this study is formed by a couch rotation through itsmore » full range of 180 degrees while the gantry makes four partial arc sweeps which are 170 degrees each. For final dose calculation, the trajectory based plans were exported to the Varian Eclipse Treatment Planning System. The plans were calculated on a homogeneous cube phantom measuring 18.2×18.2×18.2 cm3 with the analytical anisotropic algorithm (AAA) using a 1mm3 calculation voxel. The plans were delivered on the TrueBeam linac via the developer’s mode. Point dose measurements were performed on 9 patients with the IBA CC01 mini-chamber with a sensitive volume of 0.01 cc. Gafchromic film measurements along the sagittal and coronal planes were performed on three of the 9 treatment plans. Point dose values were compared with ion chamber measurements. Gamma analysis comparing film measurement and AAA calculations was performed using FilmQA Pro. Results: The AAA calculations and measurements were in good agreement. The point dose difference between AAA and ion chamber measurements were within 2.2%. Gamma analysis test pass rates (2%, 2mm passing criteria) for the Gafchromic film measurements were >95%. Conclusion: We have successfully tested TrueBeam’s ability to deliver accurate trajectory based treatments involving simultaneous gantry and couch rotation with MLC and dose rate modulation along the trajectory.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mueller, S; Joosten, A; Fix, MK
Purpose: To estimate the dosimetric potential of mixed beam radiotherapy (MBRT) by using a single process optimizing the shape and weight of photon and electron apertures simultaneously based on Monte Carlo beamlet dose distributions. Methods: A simulated annealing based direct aperture optimization capable to perform simultaneous optimization was developed to generate treatment plans for MERT, photon-IMRT and MBRT. Both photon and electron apertures are collimated with the photon-MLC and are delivered in a segmented manner. For dosimetric comparison and for investigating the dependency on the number of apertures, photon-IMRT, MERT and MBRT plans were generated for an academic case consistingmore » of a water phantom containing two shallow PTVs differing in the maximal depth of 5 and 7 cm, respectively and two OARs in distal and lateral direction to the PTVs. Results: For the superficial PTV, the dose homogeneity (V95%–V107%) and the mean dose (in percent of the prescribed dose) to the distal and the lateral OARs of the MBRT plan (94.9%, 16.9%, 17.8%) are superior or comparable to those for the MERT (74%, 18.4%, 15.4%) and the photon-IMRT plan (89.4%, 20.8%, 24.7%). For the enlarged PTV, the dosimetric superiority of MBRT compared to MERT and photon-IMRT is even more pronounced. Furthermore, an MBRT plan with 12 electron and 10 photon apertures lead to an objective function value 38% lower than that of a photon-IMRT plan with 40 apertures. Conclusion: The results of simultaneous optimization for MBRT are promising with regards to further OAR sparing and improved dose coverage to the PTV compared to photon-IMRT and MERT. Especially superficial targets with deeper subparts (>5 cm) could substantially benefit. Moreover, MBRT seems to be a possible solution of two downsides of photon-IMRT, namely the extended low dose bath and the requirement of numerous apertures. This work was supported by Varian Medical Systems. This work was supported by Varian Medical Systems.« less
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TH-AB-BRB-01: Trajectory Modulated Arc Therapy: Application to Partial Breast Irradiation
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hristov, D.
2016-06-15
Current state-of-the art digital C-arm medical linear accelerators are capable of delivering radiation treatments with high level of automation, which affords coordinated motions of gantry, couch, and multileaf collimator (MLC) with dose rate modulations. The new machine capacity has shown the potential to bring substantially improved radiation dosimetry and/or delivery efficiency to many challenging diseases. Combining an integrated beam orientation optimization algorithm with automated machine navigation, markedly improved dose conformity has been achieved using 4ρ therapy. Trajectory modulated radiation therapy (TMAT) can be used to deliver highly conformal dose to partial breast or to carve complex dose distribution for therapymore » involving extended volumes such as total marrow and total lymph node treatment. Dynamic electron arc radiotherapy (DEAR) not only overcomes the deficiencies of conventional electron therapy in dose conformity and homogeneity but also achieves so without patient-specific shields. The combination of MLC and couch tracking provides improved motion management of thoracic and abdominal tumors. A substantial body of work has been done in these technological advances for clinical translation. The proposed symposium will provide a timely review of these exciting opportunities. Learning Objectives: Recognize the potential of using digitally controlled linacs for clinically significant improvements in delivered dose distributions for various treatment sites. Identify existing approaches to treatment planning, optimization and delivery for treatment techniques utilizing the advanced functions of digital linacs and venues for further development and improvement. Understand methods for testing and validating delivery system performance. Identify tools available on current delivery systems for implementation and control for such treatments. Obtain the update in clinical applications, trials and regulatory approval. K. Sheng, NIH U19AI067769, NIH R43CA183390, NIH R01CA188300, Varian Medical Systems V. Yu, Varian Medical Systems, AAPM Summer Undergraduate Fellowship, NSF graduate fellowship S. Nill, Elekta AB. Cancer Research UK under Programme C33589/A19727, NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mihailidis, D; Mallah, J; Zhu, D
2016-06-15
Purpose: The dosimetric leaf gap (DLG) is an important parameter to be measured for dynamic beam delivery of modern linacs, like the Varian Truebeam (TB). The clinical effects of DLG-values on IMRT and/or VMAT commissioning of two “matched” TB linacs will be presented.Methods and Materials: The DLG values on two TB linacs were measured for all energy modalities (filtered and FFF-modes) as part of the dynamic delivery mode commissioning (IMRT and/or VMAT. After the standard beam data was modeled in eclipse treatment planning system (TPS) and validated, IMRT validation was performed based on TG1191 benchmark, IROC Head-Neck (H&N) phantom andmore » sample of clinical cases, all measured on both linacs. Although there was a single-set of data entered in the TPS, a noticeable difference was observed for the DLG-values between the linacs. The TG119, IROC phantom and selected patient plans were furnished with DLG-values of TB1 for both linacs and the delivery was performed on both TB linacs for comparison. Results: The DLG values of TB1 was first used for both linacs to perform the testing comparisons. The QA comparison of TG119 plans revealed a great dependence of the results to the DLG-values used for the linac for all energy modalities studied, especially when moving from 3%/3mm to 2%/2mm γ-analysis. Conclusion: The DLG-values have a definite influence on the dynamic dose, delivery that increases with the plan complexity. We recommend that the measured DLG-values are assigned to each of the “matched” linacs, even if a single set of beam data describes multiple linacs. The user should perform a detail test of the dynamic delivery of each linac based on end-to-end benchmark suites like TG119 and IROC phantoms.1Ezzel G., et al., “IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119.” Med. Phys. 36:5359–5373 (2009). partly supported by CAMC Cancer Center and Alliance Oncology.« less
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Gete, Ermias; Duzenli, Cheryl; Teke, Tony
2014-01-01
A Monte Carlo (MC) validation of the vendor‐supplied Varian TrueBeam 6 MV flattened (6X) phase‐space file and the first implementation of the Siebers‐Keall MC MLC model as applied to the HD120 MLC (for 6X flat and 6X flattening filterfree (6X FFF) beams) are described. The MC model is validated in the context of VMAT patient‐specific quality assurance. The Monte Carlo commissioning process involves: 1) validating the calculated open‐field percentage depth doses (PDDs), profiles, and output factors (OF), 2) adapting the Siebers‐Keall MLC model to match the new HD120‐MLC geometry and material composition, 3) determining the absolute dose conversion factor for the MC calculation, and 4) validating this entire linac/MLC in the context of dose calculation verification for clinical VMAT plans. MC PDDs for the 6X beams agree with the measured data to within 2.0% for field sizes ranging from 2 × 2 to 40 × 40 cm2. Measured and MC profiles show agreement in the 50% field width and the 80%‐20% penumbra region to within 1.3 mm for all square field sizes. MC OFs for the 2 to 40 cm2 square fields agree with measurement to within 1.6%. Verification of VMAT SABR lung, liver, and vertebra plans demonstrate that measured and MC ion chamber doses agree within 0.6% for the 6X beam and within 2.0% for the 6X FFF beam. A 3D gamma factor analysis demonstrates that for the 6X beam, > 99% of voxels meet the pass criteria (3%/3 mm). For the 6X FFF beam, > 94% of voxels meet this criteria. The TrueBeam accelerator delivering 6X and 6X FFF beams with the HD120 MLC can be modeled in Monte Carlo to provide an independent 3D dose calculation for clinical VMAT plans. This quality assurance tool has been used clinically to verify over 140 6X and 16 6X FFF TrueBeam treatment plans. PACS number: 87.55.K‐ PMID:24892341
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hu, Y; Rottmann, J; Myronakis, M
2016-06-15
Purpose: The purpose of this study was to validate the use of a cascaded linear system model for MV cone-beam CT (CBCT) using a multi-layer (MLI) electronic portal imaging device (EPID) and provide experimental insight into image formation. A validated 3D model provides insight into salient factors affecting reconstructed image quality, allowing potential for optimizing detector design for CBCT applications. Methods: A cascaded linear system model was developed to investigate the potential improvement in reconstructed image quality for MV CBCT using an MLI EPID. Inputs to the three-dimensional (3D) model include projection space MTF and NPS. Experimental validation was performedmore » on a prototype MLI detector installed on the portal imaging arm of a Varian TrueBeam radiotherapy system. CBCT scans of up to 898 projections over 360 degrees were acquired at exposures of 16 and 64 MU. Image volumes were reconstructed using a Feldkamp-type (FDK) filtered backprojection (FBP) algorithm. Flat field images and scans of a Catphan model 604 phantom were acquired. The effect of 2×2 and 4×4 detector binning was also examined. Results: Using projection flat fields as an input, examination of the modeled and measured NPS in the axial plane exhibits good agreement. Binning projection images was shown to improve axial slice SDNR by a factor of approximately 1.4. This improvement is largely driven by a decrease in image noise of roughly 20%. However, this effect is accompanied by a subsequent loss in image resolution. Conclusion: The measured axial NPS shows good agreement with the theoretical calculation using a linear system model. Binning of projection images improves SNR of large objects on the Catphan phantom by decreasing noise. Specific imaging tasks will dictate the implementation image binning to two-dimensional projection images. The project was partially supported by a grant from Varian Medical Systems, Inc. and grant No. R01CA188446-01 from the National Cancer Institute.« less
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Clinical implementation of AXB from AAA for breast: Plan quality and subvolume analysis.
Guebert, Alexandra; Conroy, Leigh; Weppler, Sarah; Alghamdi, Majed; Conway, Jessica; Harper, Lindsay; Phan, Tien; Olivotto, Ivo A; Smith, Wendy L; Quirk, Sarah
2018-05-01
Two dose calculation algorithms are available in Varian Eclipse software: Anisotropic Analytical Algorithm (AAA) and Acuros External Beam (AXB). Many Varian Eclipse-based centers have access to AXB; however, a thorough understanding of how it will affect plan characteristics and, subsequently, clinical practice is necessary prior to implementation. We characterized the difference in breast plan quality between AXB and AAA for dissemination to clinicians during implementation. Locoregional irradiation plans were created with AAA for 30 breast cancer patients with a prescription dose of 50 Gy to the breast and 45 Gy to the regional node, in 25 fractions. The internal mammary chain (IMC CTV ) nodes were covered by 80% of the breast dose. AXB, both dose-to-water and dose-to-medium reporting, was used to recalculate plans while maintaining constant monitor units. Target coverage and organ-at-risk doses were compared between the two algorithms using dose-volume parameters. An analysis to assess location-specific changes was performed by dividing the breast into nine subvolumes in the superior-inferior and left-right directions. There were minimal differences found between the AXB and AAA calculated plans. The median difference between AXB and AAA for breast CTV V 95% , was <2.5%. For IMC CTV , the median differences V 95% , and V 80% were <5% and 0%, respectively; indicating IMC CTV coverage only decreased when marginally covered. Mean superficial dose increased by a median of 3.2 Gy. In the subvolume analysis, the medial subvolumes were "hotter" when recalculated with AXB and the lateral subvolumes "cooler" with AXB; however, all differences were within 2 Gy. We observed minimal difference in magnitude and spatial distribution of dose when comparing the two algorithms. The largest observable differences occurred in superficial dose regions. Therefore, clinical implementation of AXB from AAA for breast radiotherapy is not expected to result in changes in clinical practice for prescribing or planning breast radiotherapy. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Soh, R; Lee, J; Harianto, F
Purpose: To determine and compare the correction factors obtained for TLDs in 2 × 2cm{sup 2} small field in lung heterogenous phantom using Acuros XB (AXB) and EGSnrc. Methods: This study will simulate the correction factors due to the perturbation of TLD-100 chips (Harshaw/Thermoscientific, 3 × 3 × 0.9mm{sup 3}, 2.64g/cm{sup 3}) in small field lung medium for Stereotactic Body Radiation Therapy (SBRT). A physical lung phantom was simulated by a 14cm thick composite cork phantom (0.27g/cm{sup 3}, HU:-743 ± 11) sandwiched between 4cm thick Plastic Water (CIRS,Norfolk). Composite cork has been shown to be a good lung substitute materialmore » for dosimetric studies. 6MV photon beam from Varian Clinac iX (Varian Medical Systems, Palo Alto, CA) with field size 2 × 2cm{sup 2} was simulated. Depth dose profiles were obtained from the Eclipse treatment planning system Acuros XB (AXB) and independently from DOSxyznrc, EGSnrc. Correction factors was calculated by the ratio of unperturbed to perturbed dose. Since AXB has limitations in simulating actual material compositions, EGSnrc will also simulate the AXB-based material composition for comparison to the actual lung phantom. Results: TLD-100, with its finite size and relatively high density, causes significant perturbation in 2 × 2cm{sup 2} small field in a low lung density phantom. Correction factors calculated by both EGSnrc and AXB was found to be as low as 0.9. It is expected that the correction factor obtained by EGSnrc wlll be more accurate as it is able to simulate the actual phantom material compositions. AXB have a limited material library, therefore it only approximates the composition of TLD, Composite cork and Plastic water, contributing to uncertainties in TLD correction factors. Conclusion: It is expected that the correction factors obtained by EGSnrc will be more accurate. Studies will be done to investigate the correction factors for higher energies where perturbation may be more pronounced.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, X; Xiong, W; Gewanter, R
Purpose: Average or maximum intensity projection (AIP or MIP) images derived from 4DCT images are often used as a reference image for target alignment when free breathing Cone-beam CT (FBCBCT) is used for positioning a moving target at treatment. This method can be highly accurate if the patient has stable respiratory motion. However, a patient’s breathing pattern often varies irregularly. The purpose of this study is to investigate the effect of irregular respiration on the positioning accuracy of a moving target with FBCBCT. Methods: Eight patients’ respiratory motion curves were selected to drive a Quasar phantom with embedded cubic andmore » spherical targets. A 4DCT of the moving phantom was acquired on a CT scanner (Philips Brilliance 16) equipped with a Varian RPM system. The phase binned 4DCT images and the corresponding MIP and AIP images were transferred into Eclipse for analysis. CBCTs of the phantom driven by the same breathing curves were acquired on a Varian TrueBeam and fused such that the zero positions of moving targets are the same on both CBCT and AIP images. The sphere and cube volumes and centrioid differences (alignment error) determined by MIP, AIP and FBCBCT images were compared. Results: Compared to the volume determined by FBCBCT, the volumes of cube and sphere in MIP images were 22.4%±8.8% and 34.2%±6.2% larger while the volumes in AIP images were 7.1%±6.2% and 2.7%±15.3% larger, respectively. The alignment errors for the cube and sphere with center-center matches between MIP and FBCBCT were 3.5±3.1mm and 3.2±2.3mm, and the alignment errors between AIP and FBCBCT were 2.1±2.6mm and 2.1±1.7mm, respectively. Conclusion: AIP images appear to be superior reference images than MIP images. However, irregular respiratory motions could compromise the positioning accuracy of a moving target if the target center-center match is used to align FBCBCT and AIP images.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Glaser, Adam K., E-mail: Adam.K.Glaser@dartmouth.edu, E-mail: Brian.W.Pogue@dartmouth.edu; Andreozzi, Jacqueline M.; Davis, Scott C.
Purpose: A novel technique for optical dosimetry of dynamic intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) plans was investigated for the first time by capturing images of the induced Cherenkov radiation in water. Methods: A high-sensitivity, intensified CCD camera (ICCD) was configured to acquire a two-dimensional (2D) projection image of the Cherenkov radiation induced by IMRT and VMAT plans, based on the Task Group 119 (TG-119) C-Shape geometry. Plans were generated using the Varian Eclipse treatment planning system (TPS) and delivered using 6 MV x-rays from a Varian TrueBeam Linear Accelerator (Linac) incident on a water tank dopedmore » with the fluorophore quinine sulfate. The ICCD acquisition was gated to the Linac target trigger pulse to reduce background light artifacts, read out for a single radiation pulse, and binned to a resolution of 512 × 512 pixels. The resulting videos were analyzed temporally for various regions of interest (ROI) covering the planning target volume (PTV) and organ at risk (OAR), and summed to obtain an overall light intensity distribution, which was compared to the expected dose distribution from the TPS using a gamma-index analysis. Results: The chosen camera settings resulted in 23.5 frames per second dosimetry videos. Temporal intensity plots of the PTV and OAR ROIs confirmed the preferential delivery of dose to the PTV versus the OAR, and the gamma analysis yielded 95.9% and 96.2% agreement between the experimentally captured Cherenkov light distribution and expected TPS dose distribution based upon a 3%/3 mm dose difference and distance-to-agreement criterion for the IMRT and VMAT plans, respectively. Conclusions: The results from this initial study demonstrate the first documented use of Cherenkov radiation for video-rate optical dosimetry of dynamic IMRT and VMAT treatment plans. The proposed modality has several potential advantages over alternative methods including the real-time nature of the acquisition, and upon future refinement may prove to be a robust and novel dosimetry method with both research and clinical applications.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Mathew, D; Tanny, S; Parsai, E
2015-06-15
Purpose: The current small field dosimetry formalism utilizes quality correction factors to compensate for the difference in detector response relative to dose deposited in water. The correction factors are defined on a machine-specific basis for each beam quality and detector combination. Some research has suggested that the correction factors may only be weakly dependent on machine-to-machine variations, allowing for determinations of class-specific correction factors for various accelerator models. This research examines the differences in small field correction factors for three detectors across two Varian Truebeam accelerators to determine the correction factor dependence on machine-specific characteristics. Methods: Output factors were measuredmore » on two Varian Truebeam accelerators for equivalently tuned 6 MV and 6 FFF beams. Measurements were obtained using a commercial plastic scintillation detector (PSD), two ion chambers, and a diode detector. Measurements were made at a depth of 10 cm with an SSD of 100 cm for jaw-defined field sizes ranging from 3×3 cm{sup 2} to 0.6×0.6 cm{sup 2}, normalized to values at 5×5cm{sup 2}. Correction factors for each field on each machine were calculated as the ratio of the detector response to the PSD response. Percent change of correction factors for the chambers are presented relative to the primary machine. Results: The Exradin A26 demonstrates a difference of 9% for 6×6mm{sup 2} fields in both the 6FFF and 6MV beams. The A16 chamber demonstrates a 5%, and 3% difference in 6FFF and 6MV fields at the same field size respectively. The Edge diode exhibits less than 1.5% difference across both evaluated energies. Field sizes larger than 1.4×1.4cm2 demonstrated less than 1% difference for all detectors. Conclusion: Preliminary results suggest that class-specific correction may not be appropriate for micro-ionization chamber. For diode systems, the correction factor was substantially similar and may be useful for class-specific reference conditions.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Giaddui, T; Li, N; Moore, K
Purpose: To establish a workflow for NRG-GY006 IMRT pre-treatment reviews, incorporating advanced radiotherapy technologies being evaluated as part of the clinical trial. Methods: Pre-Treatment reviews are required for every IMRT case as part of NRG-GY006 (a randomized phase II trial of radiation therapy and cisplatin alone or in combination with intravenous triapine in women with newly diagnosed bulky stage I B2, stage II, IIIB, or IVA cancer of the uterine cervix or stage II-IVA vaginal cancer. The pretreatment review process includes structures review and generating an active bone marrow(ABM)- to be used as an avoidance structure during IMRT optimization- andmore » evaluating initial IMRT plan quality using knowledgeengineering based planning (KBP). Institutions will initially submit their simulation CT scan, structures file and PET/CT to IROC QA center for generating ABM. The ABM will be returned to the institution for use in planning. Institutions will then submit an initial IMRT plan for review and will receive information back following implementation of a KBP algorithm, for use in re-optimization, before submitting the final IMRT used for treatment. Results: ABM structure is generated using MIM vista software (Version 6.5, MIM corporation, Inc.). Here, the planning CT and the diagnostic PET/CT are fused and a sub threshold structure is auto segmented above the mean value of the SUV of the bone marrow. The generated ABM were compared with those generated with other software system (e.g. Velocity, Varian) and Dice coefficient (reflects the overlap of structures) ranged between 80 – 90% was achieved. A KBP model was built in Varian Eclipse TPS using the RapidPlan KBP software to perform plan quality assurance. Conclusion: The workflow for IMRT pretreatment reviews has been established. It represents a major improvement of NRG Oncology clinical trial quality assurance and incorporates the latest radiotherapy technologies as part of NCI clinical trials. This project was supported by grants U24CA180803 (IROC), UG1CA189867 (NCORP), U10CA180868 (NRG Oncology Operations), U10CA180822 (NRG Oncology SDMC) from the National Cancer Institute (NCI) and PA CURE grant.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhao, H; Sarkar, V; Rassiah-Szegedi, P
2014-06-01
Purpose: To investigate and report the discrepancy of scanned percent depth dose (PDD) for photon beams with physical wedge in place when using ion chambers with different sensitive volumes. Methods/Materials: PDD curves of open fields and physical wedged fields (15, 30, 45, and 60 degree wedge) were scanned for photon beams (6MV and 10MV, Varian iX) with field size of 5x5 and 10x10 cm using three common scanning chambers with different sensitive volumes - PTW30013 (0.6cm3), PTW23323 (0.1cm3) and Exradin A16 (0.007cm3). The scanning system software used was OmniPro version 6.2, and the scanning water tank was the Scanditronix Wellhoffermore » RFA 300.The PDD curves from the three chambers were compared. Results: Scanned PDD curves of the same energy beams for open fields were almost identical between three chambers, but the wedged fields showed non-trivial differences. The largest differences were observed between chamber PTW30013 and Exradin A16. The differences increased as physical wedge angle increased. The differences also increased with depth, and were more pronounced for 6MV beam. Similar patterns were shown for both 5x5 and 10x10 cm field sizes. For open fields, all PDD values agreed with each other within 1% at 10cm depth and within 1.62% at 20 cm depth. For wedged fields, the difference of PDD values between PTW30013 and A16 reached 4.09% at 10cm depth, and 5.97% at 20 cm depth for 6MV with 60 degree physical wedge. Conclusion: We observed a significant difference in scanned PDD curves of photon beams with physical wedge in place obtained when using different sensitive volume ion chambers. The PDD curves scanned with the smallest sensitive volume ion chamber showed significant difference from larger chamber results, beyond 10cm depth. We believe this to be caused by varying response to beam hardening by the wedges.« less
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TU-H-CAMPUS-TeP2-02: FLASH Irradiation Improves the Therapeutic Index Following GI Tract Irradiation
DOE Office of Scientific and Technical Information (OSTI.GOV)
Schueler, E; Trovati, S; King, G
Purpose: To investigate and characterize the radiobiological effectiveness of very high dose rate radiotherapy (FLASH) compared to conventional irradiation in an in vivo model. Methods: The gastrointestinal (GI) tract of C57BL/6 mice were irradiated with doses ranging between 10 and 18 Gy using a custom stereotactic jig. A Varian Clinac 21EX was modified to allow dose rates ranging from 0.05 to 240 Gy/s at the position of the mirror. With the gantry at 180 degrees, the jig holding the individual animals was placed above the mirror to take advantage of the reduced source to target distance. Mice were irradiated withmore » 20MeV electrons. Following irradiation, the mice were monitored twice daily for morbidity and daily for weight changes. Results: Mice irradiated with FLASH irradiation had lower weight loss compared to the mice receiving conventional irradiation. Following FLASH irradiation, a maximum weight loss of ∼20% was observed at day 6 with subsequent recovery, while following conventional irradiation, higher weight losses was observed with fewer instances of recovery. Concerning survival, all mice in the conventionally irradiated groups had a 100% mortality in the range of 15.5–18 Gy, while the mice irradiated with FLASH irradiation had a 100% survival in the same range. Conclusion: These results have demonstrated proof of principle that FLASH irradiations have a dramatic impact on the overall survival of mice following GI tract irradiations. If the increase in the therapeutic window can be validated and understood, this would revolutionize the field of radiation oncology and lead to increased cure rates with reduced side effects following treatment, resulting in increased quality of life for cancer survivors. Funding: DoD, Award#:W81XWH-14-1-0014, Weston Havens Foundation, Bio-X (Stanford University), the Office of the Dean of the Medical School, the Office of the Provost (Stanford University), and the Swedish Childhood Cancer Foundation; BL and PM are founders of TibaRay,Inc.; BL and PM have received research grants from Varian and RaySearch Laboratory.« less
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Verma, Vivek
2017-10-01
To quantitate financial conflicts of interest (FCOIs) among radiation oncology peer-reviewers, specifically editorial board members of the 3 American Society for Radiation Oncology journals. The public Centers for Medicare and Medicaid Services Open Payments database delineates payments in 3 categories (general payments, research funding, and company ownership). After excluding non-US and non-MDs, names of board members were searched. Values of each FCOI were extracted for 2013 to 2015 and compiled. Of 85 board members, 65 (76%) received any form of payment during the overall period. The majority of delivered payments were general payments: 59 (69%) received at least 1 general payment during these 3 years. In each year, 9 board members (11%) received research funding, and 3 board members (4%) reported company ownership. Over the studied period, all board members received a sum total of $5,387,985; this was composed of $665,801 (12%) in general payments, $3,758,968 (70%) in research funding, and $963,216 (18%) in company ownership. The mean general payment and research funding amounts (all members) were $2,621 and $14,741, respectively. Median (interquartile range) general payments and research funding only in board members receiving payments were $419 ($91-$5072) and $56,250 ($13,345-$200,000), respectively. When assessing general payments according to amount, the vast majority of editorial board members received lower-quantity or no such payments, along with a smaller proportion that received higher-volume payments. The most frequent sources of general payments were Varian, Elekta, and Bristol-Myers Squibb. Merck and Varian were the most frequent funding sources for research payments. In this population, the majority of FCOIs were general payments, but research funding comprised the highest monetary sums. Large-volume FCOIs do not apply to the vast majority of editorial board members, implying that the maintained integrity of academic peer-review is likely not influenced to a large extent by FCOIs. Copyright © 2017 Elsevier Inc. All rights reserved.
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TU-E-BRA-05: Reverse Geometry Imaging with MV Detector for Improved Image Resolution.
Ganguly, A; Abel, E; Sun, M; Fahrig, R; Virshup, G; Star-Lack, J
2012-06-01
Thick pixilated scintillators can offer significant improvements in quantum efficiency over phosphor screen megavoltage (MV) detectors. However spatial resolution can be compromised due to the spreading of light across pixels within septa. Of particular interest are the lower energy x-ray photons and associated light photons that produce higher image contrast but are stopped near the scintillator entrance surface. They suffer the most scattering in the scintillator prior to detection in the photodiodes. Reversing the detector geometry, so that the incident x-ray beam passes through the photodiode array into the scintillator, allows the light to scatter less prior to detection. This also reduces the Swank noise since now higher and lower energy x-ray photons tend to produce similar electronic signals. In this work, we present simulations and measurements of detector MTF for the conventional/forward and reverse geometries to demonstrate this phenomenon. A tabletop system consisting of a Varian CX1 1MeV linear accelerator and a modified Varian Paxscan4030 with the readout electronics moved away from the incident the beam was used. A special holder was used to press a 2.5W×5.0L×2.0Hcm 3 pixellated Cesium Iodide (CsI:Tl) scintillator array on to the detector glass. The CsI array had a pitch of 0.784mm with plastic septa between pixels and the photodiode array pitch was 0.192 mm. The MTF in the forward and reverse geometries was measured using a 0.5mm thick Tantalum slanted edge. Geant4-based Monte Carlo simulations were performed for comparison. The measured and simulated MTFs matched to within 3.4(±3.7)% in the forward and 4.4(±1.5)% in reverse geometries. The reverse geometry MTF was higher than the forward geometry MTF at all spatial frequencies and doubled to .25 at 0.3lp/mm. A novel method of improving the image resolution at MV energies was demonstrated. The improvements should be more pronounced with increased scintillator thickness. Funding support provided by NIH (grant number NIH R01 CA138426). © 2012 American Association of Physicists in Medicine.
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Dose verification for respiratory-gated volumetric modulated arc therapy (VMAT)
Qian, Jianguo; Xing, Lei; Liu, Wu; Luxton, Gary
2011-01-01
A novel commercial medical linac system (TrueBeam™, Varian Medical Systems, Palo Alto, CA) allows respiratory-gated volumetric modulated arc therapy (VMAT), a new modality for treating moving tumors with high precision and improved accuracy by allowing for regular motion associated with a patient's breathing during VMAT delivery. The purpose of this work is to adapt a previously-developed dose reconstruction technique to evaluate the fidelity of VMAT treatment during gated delivery under clinic-relevant periodic motion related to patient breathing. A Varian TrueBeam system was used in this study. VMAT plans were created for three patients with lung or pancreas tumors. Conventional 6 MV and 15 MV beams with flattening filter and high dose-rate 10 MV beams with no flattening filter were used in these plans. Each patient plan was delivered to a phantom first without gating and then with gating for three simulated respiratory periods (3, 4.5 and 6 seconds). Using the adapted log file-based dose reconstruction procedure supplemented with ion chamber array (Seven29™, PTW, Freiburg, Germany) measurements, the delivered dose was used to evaluate the fidelity of gated VMAT delivery. Comparison of Seven29 measurements with and without gating showed good agreement with gamma-index passing rates above 99% for 1%/1mm dose accuracy/distance-to-agreement criteria. With original plans as reference, gamma-index passing rates were 100% for the reconstituted plans (1%/1 mm criteria) and 93.5–100% for gated Seven29 measurements (3%/3 mm criteria). In the presence of leaf error deliberately introduced into the gated delivery of a pancreas patient plan, both dose reconstruction and Seven29 measurement consistently indicated substantial dosimetric differences from the original plan. In summary, a dose reconstruction procedure was demonstrated for evaluating the accuracy of respiratory-gated VMAT delivery. This technique showed that under clinical operation, the TrueBeam system faithfully realized treatment plans with gated delivery. This methodology affords a useful tool for machine and patient-specific quality assurance of the newly available respiratory-gated VMAT. PMID:21753232
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SU-F-J-147: Magnetic Field Dose Response Considerations for a Linac Monitor Chamber
DOE Office of Scientific and Technical Information (OSTI.GOV)
Reynolds, M; Fallone, B
Purpose: The impact of magnetic fields on the readings of a linac monitor chamber have not yet been investigated. Herein we examine the total dose response as well as any deviations in the beam parameters of flatness and symmetry when a Varian monitor chamber is irradiated within an applied magnetic field. This work has direct application to the development of Linac-MR systems worldwide. Methods: A Varian monitor chamber was modeled in the Monte Carlo code PENELOPE and irradiated in the presence of a magnetic field with a phase space generated from a model of a Linac-MR prototype system. The magneticmore » field strength was stepped from 0 to 3.0T in both parallel and perpendicular directions with respect to the normal surface of the phase space. Dose to each of the four regions in the monitor chamber were scored separately for every magnetic field adaptation to evaluate the effect of the magnetic field on flatness and symmetry. Results: When the magnetic field is perpendicular to the phase space normal we see a change in dose response with a maximal deviation (10–25% depending on the chamber region) near 0.75T. In the direction of electron deflection we expectedly see opposite responses in chamber regions leading to a measured asymmetry. With a magnetic field parallel to the phase space normal we see no measured asymmetries, however there is a monotonic rise in dose response leveling off at about +12% near 2.5T. Conclusion: Attention must be given to correct for the strength and direction of the magnetic field at the location of the linac monitor chamber in hybrid Linac-MR devices. Elsewise the dose sampled by these chambers may not represent the actual dose expected at isocentre; additionally there may be a need to correct for the symmetry of the beam recorded by the monitor chamber. Fallone is a co-founder and CEO of MagnetTx Oncology Solutions (under discussions to license Alberta bi-planar linac MR for commercialization).« less
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SU-F-T-562: Validation of EPID-Based Dosimetry for FSRS Commissioning
DOE Office of Scientific and Technical Information (OSTI.GOV)
Song, Y; Saleh, Z; Obcemea, C
Purpose: The prevailing approach to frameless SRS (fSRS) small field dosimetry is Gafchromic film. Though providing continuous information, its intrinsic uncertainties in fabrication, response, scan, and calibration often make film dosimetry subject to different interpretations. In this study, we explored the feasibility of using EPID portal dosimetry as a viable alternative to film for small field dosimetry. Methods: Plans prescribed a dose of 21 Gy were created on a flat solid water phantom with Eclipse V11 and iPlan for small static square fields (1.0 to 3.0 cm). In addition, two clinical test plans were computed by employing iPlan on amore » CIRS Kesler head phantom for target dimensions of 1.2cm and 2.0cm. Corresponding portal dosimetry plans were computed using the Eclipse TPS and delivered on a Varian TrueBeam machine. EBT-XD film dosimetry was performed as a reference. The isocenter doses were measured using EPID, OSLD, stereotactic diode, and CC01 ion chamber. Results: EPID doses at the center of the square field were higher than Eclipse TPS predicted portal doses, with the mean difference being 2.42±0.65%. Doses measured by EBT-XD film, OSLD, stereotactic diode, and CC01 ion chamber revealed smaller differences (except OSLDs), with mean differences being 0.36±3.11%, 4.12±4.13%, 1.7±2.76%, 1.45±2.37% for Eclipse and −1.36±0.85%, 2.38±4.2%, −0.03±0.50%, −0.27±0.78% for iPlan. The profiles measured by EPID and EBT-XD film resembled TPS (Eclipse and iPlan) predicted ones within 3.0%. For the two clinical test plans, the EPID mean doses at the center of field were 2.66±0.68% and 2.33±0.32% higher than TPS predicted doses. Conclusion: We found that results obtained with EPID portal dosimetry were slightly higher (∼2%) than those obtained with EBT-XD film, diode, and CC01 ion chamber with the exception of OSLDs, but well within IROC tolerance (5.0%). Therefore, EPID has the potential to become a viable real-time alternative method to film dosimetry.« less
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Concomitant Imaging Dose and Cancer Risk in Image Guided Thoracic Radiation Therapy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhang, Yibao; Wu, Hao; Chen, Zhe
Purpose: Kilovoltage cone beam computed tomography (CT) (kVCBCT) imaging guidance improves the accuracy of radiation therapy but imposes an extra radiation dose to cancer patients. This study aimed to investigate concomitant imaging dose and associated cancer risk in image guided thoracic radiation therapy. Methods and Materials: The planning CT images and structure sets of 72 patients were converted to CT phantoms whose chest circumferences (C{sub chest}) were calculated retrospectively. A low-dose thorax protocol on a Varian kVCBCT scanner was simulated by a validated Monte Carlo code. Computed doses to organs and cardiac substructures (for 5 selected patients of various dimensions)more » were regressed as empirical functions of C{sub chest}, and associated cancer risk was calculated using the published models. The exposures to nonthoracic organs in children were also investigated. Results: The structural mean doses decreased monotonically with increasing C{sub chest}. For all 72 patients, the median doses to the heart, spinal cord, breasts, lungs, and involved chest were 1.68, 1.33, 1.64, 1.62, and 1.58 cGy/scan, respectively. Nonthoracic organs in children received 0.6 to 2.8 cGy/scan if they were directly irradiated. The mean doses to the descending aorta (1.43 ± 0.68 cGy), left atrium (1.55 ± 0.75 cGy), left ventricle (1.68 ± 0.81 cGy), and right ventricle (1.85 ± 0.84 cGy) were significantly different (P<.05) from the heart mean dose (1.73 ± 0.82 cGy). The blade shielding alleviated the exposure to nonthoracic organs in children by an order of magnitude. Conclusions: As functions of patient size, a series of models for personalized estimation of kVCBCT doses to thoracic organs and cardiac substructures have been proposed. Pediatric patients received much higher doses than did the adults, and some nonthoracic organs could be irradiated unexpectedly by the default scanning protocol. Increased cancer risks and disease adverse events in the thorax were strongly related to higher imaging doses and smaller chest dimensions.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Wu, Q; Devpura, S; Feghali, K
2016-06-15
Purpose: To investigate correlation of normal lung CT density changes with dose accuracy and outcome after SBRT for patients with early stage lung cancer. Methods: Dose distributions for patients originally planned and treated using a 1-D pencil beam-based (PB-1D) dose algorithm were retrospectively recomputed using algorithms: 3-D pencil beam (PB-3D), and model-based Methods: AAA, Acuros XB (AXB), and Monte Carlo (MC). Prescription dose was 12 Gy × 4 fractions. Planning CT images were rigidly registered to the followup CT datasets at 6–9 months after treatment. Corresponding dose distributions were mapped from the planning to followup CT images. Following the methodmore » of Palma et al .(1–2), Hounsfield Unit (HU) changes in lung density in individual, 5 Gy, dose bins from 5–45 Gy were assessed in the peri-tumor region, defined as a uniform, 3 cm expansion around the ITV(1). Results: There is a 10–15% displacement of the high dose region (40–45 Gy) with the model-based algorithms, relative to the PB method, due to the electron scattering of dose away from the tumor into normal lung tissue (Fig.1). Consequently, the high-dose lung region falls within the 40–45 Gy dose range, causing an increase in HU change in this region, as predicted by model-based algorithms (Fig.2). The patient with the highest HU change (∼110) had mild radiation pneumonitis, and the patient with HU change of ∼80–90 had shortness of breath. No evidence of pneumonitis was observed for the 3 patients with smaller CT density changes (<50 HU). Changes in CT densities, and dose-response correlation, as computed with model-based algorithms, are in excellent agreement with the findings of Palma et al. (1–2). Conclusion: Dose computed with PB (1D or 3D) algorithms was poorly correlated with clinically relevant CT density changes, as opposed to model-based algorithms. A larger cohort of patients is needed to confirm these results. This work was supported in part by a grant from Varian Medical Systems, Palo Alto, CA.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Modiri, A; Hagan, A; Gu, X
Purpose 4D-IMRT planning, combined with dynamic MLC tracking delivery, utilizes the temporal dimension as an additional degree of freedom to achieve improved OAR-sparing. The computational complexity for such optimization increases exponentially with increase in dimensionality. In order to accomplish this task in a clinically-feasible time frame, we present an initial implementation of GPU-based 4D-IMRT planning based on particle swarm optimization (PSO). Methods The target and normal structures were manually contoured on ten phases of a 4DCT scan of a NSCLC patient with a 54cm3 right-lower-lobe tumor (1.5cm motion). Corresponding ten 3D-IMRT plans were created in the Eclipse treatment planning systemmore » (Ver-13.6). A vendor-provided scripting interface was used to export 3D-dose matrices corresponding to each control point (10 phases × 9 beams × 166 control points = 14,940), which served as input to PSO. The optimization task was to iteratively adjust the weights of each control point and scale the corresponding dose matrices. In order to handle the large amount of data in GPU memory, dose matrices were sparsified and placed in contiguous memory blocks with the 14,940 weight-variables. PSO was implemented on CPU (dual-Xeon, 3.1GHz) and GPU (dual-K20 Tesla, 2496 cores, 3.52Tflops, each) platforms. NiftyReg, an open-source deformable image registration package, was used to calculate the summed dose. Results The 4D-PSO plan yielded PTV coverage comparable to the clinical ITV-based plan and significantly higher OAR-sparing, as follows: lung Dmean=33%; lung V20=27%; spinal cord Dmax=26%; esophagus Dmax=42%; heart Dmax=0%; heart Dmean=47%. The GPU-PSO processing time for 14940 variables and 7 PSO-particles was 41% that of CPU-PSO (199 vs. 488 minutes). Conclusion Truly 4D-IMRT planning can yield significant OAR dose-sparing while preserving PTV coverage. The corresponding optimization problem is large-scale, non-convex and computationally rigorous. Our initial results indicate that GPU-based PSO with further software optimization can make such planning clinically feasible. This work was supported through funding from the National Institutes of Health and Varian Medical Systems.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Devpura, S; Li, H; Liu, C
Purpose: To correlate dose distributions computed using six algorithms for recurrent early stage non-small cell lung cancer (NSCLC) patients treated with stereotactic body radiotherapy (SBRT), with outcome (local failure). Methods: Of 270 NSCLC patients treated with 12Gyx4, 20 were found to have local recurrence prior to the 2-year time point. These patients were originally planned with 1-D pencil beam (1-D PB) algorithm. 4D imaging was performed to manage tumor motion. Regions of local failures were determined from follow-up PET-CT scans. Follow-up CT images were rigidly fused to the planning CT (pCT), and recurrent tumor volumes (Vrecur) were mapped to themore » pCT. Dose was recomputed, retrospectively, using five algorithms: 3-D PB, collapsed cone convolution (CCC), anisotropic analytical algorithm (AAA), AcurosXB, and Monte Carlo (MC). Tumor control probability (TCP) was computed using the Marsden model (1,2). Patterns of failure were classified as central, in-field, marginal, and distant for Vrecur ≥95% of prescribed dose, 95–80%, 80–20%, and ≤20%, respectively (3). Results: Average PTV D95 (dose covering 95% of the PTV) for 3-D PB, CCC, AAA, AcurosXB, and MC relative to 1-D PB were 95.3±2.1%, 84.1±7.5%, 84.9±5.7%, 86.3±6.0%, and 85.1±7.0%, respectively. TCP values for 1-D PB, 3-D PB, CCC, AAA, AcurosXB, and MC were 98.5±1.2%, 95.7±3.0, 79.6±16.1%, 79.7±16.5%, 81.1±17.5%, and 78.1±20%, respectively. Patterns of local failures were similar for 1-D and 3D PB plans, which predicted that the majority of failures occur in centraldistal regions, with only ∼15% occurring distantly. However, with convolution/superposition and MC type algorithms, the majority of failures (65%) were predicted to be distant, consistent with the literature. Conclusion: Based on MC and convolution/superposition type algorithms, average PTV D95 and TCP were ∼15% lower than the planned 1-D PB dose calculation. Patterns of failure results suggest that MC and convolution/superposition type algorithms predict different outcomes for patterns of failure relative to PB algorithms. Work supported in part by Varian Medical Systems, Palo Alto, CA.« less
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Comparison of dose accuracy between 2D array detectors and Epid for IMRT of nasopharynx cancer
NASA Astrophysics Data System (ADS)
Altiparmak, Duygu; Coban, Yasin; Merih, Adil; Avci, Gulhan Guler; Yigitoglu, Ibrahim
2017-02-01
The aim of this study is to perform the dosimetric controls of nasopharynx cancer patient's intensity modulated radiation therapy (IMRT) treatment plans that generated by treatment planing system (TPS) with using two different equipments and also to make comparison in terms of their reliability and practicability. This study has been performed at Radiation Oncology Department, Medicine Faculty in Gaziosmanpasa University by using the VARIAN CLINAC DHX linear accelerator which is operated in the range of 6 MV. Selected 10 nasopharynx patients planned in TPS (Eclipce V13.0) and approved for treatment by medical physicists and radiation oncologists. These plans recalculated on EPID and mapcheck which are 2D dosimetric equipments to obtain dose maps. To compare these two dosimetric equipments gamma analysis method has been preferred. Achieved data is presented and discussed.
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NASA Astrophysics Data System (ADS)
Latifah, R.; Bunawas; Noor, J. A. E.
2018-03-01
Linear accelerator (linac) becomes the most commonly used treatment to damage and kill cancer cell. Photon and electron as the radiation beam are produced by accelerating electrons to very high energy. Neutrons are generated when incident high photon energy interacts with component of linac such as target, flattering filter and collimator via photoneutrons reaction. The neutrons can also produce activation of materials in treatment room to generate radioactive materials. We have estimated the concentration of Argon-41 as activated product from argon-40 in the linac room using foil activation. The results show that the Argon-41 concentration in linac room which is operated 15 MV for 1 treatment (1 minute) is 1440 Bq/m3. Accordingly that concentration, the occupational dose is 6.4 mSv per year.
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The (HMI9293) acquisition of a 200 MHz nuclear magnetic resonance spectrometer
NASA Astrophysics Data System (ADS)
Hageman, James H.
1994-09-01
With the funds awarded from DOD-AFOSR and matching funds from New Mexico State a new Varian Gemini 200 MHz nmr was purchased and installed in the spring of 1994. This instrument is capable of 1H and 130 nmr, is very sensitive, and can also do Hetcor experiments to facilitate proton assignments. It is very easy to use and has proven thus far to be extremely reliable. The change in the research output in the department has been significant. Whereas previously students had to sometimes wait days to run routine nmr spectra because our high field instrument was otherwise occupied with longer experiments, now they can run spectra immediately (or with minimal wait). This speeds up structure assignments, and gives students instant gratification when experiments succeed and rapid feedback when they are not successful.
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Szczerba, Izabela
2003-01-01
The aim of work was to evaluate the frequency of occurrence of bacteria from genera of Micrococcus, Kocuria, Nesterenkonia, kytococcus and Dermatococcus on human skin and mucous membranes in healthy population. Among 150 investigated persons these bacteria were found in 122 (81.3%). The frequency of isolation was similar in both sex (82.4% in female and 79.7% in male). Most often the strains were isolated from oral cavity (48.7%), and from skin of palm and forearm (40.7% and 37.3%). Least frequency of occurrence was observed in vestibule of nose (26%). The predominant isolated strains were: M. luteus (26.2%), and N. halobia (21%) followed by K. varians (16.4%), M. lylae (12.2%), D. sedentarius (9.1%), K. kristinae (7.3%), K. nishinomiyaensis (7.3%), K. rosea (0.3%).
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Effect of various SnO2 pH on ZnO/SnO2-composite film via immersion technique
NASA Astrophysics Data System (ADS)
Malek, M. F.; Mohamed, R.; Mamat, M. H.; Ismail, A. S.; Yusoff, M. M.; Rusop, M.
2018-05-01
ZnO/SnO2-composite film has been synthesized via immersion technique with various pH of SnO2. The pH of SnO2 were varied between 4.5 and 6.5. The optical measurements of the samples were carried out using Varian Cary 5000 UV-Vis spectrophotometer within the range from 350 nm to 800 nm at room temperature in air with a data interval of 1 nm. On the other hand, the optical photoluminescence properties were measured by a photoluminescence spectrometer (PL, model: Horiba Jobin Yvon - 79 DU420A-OE-325) using a He-Cd laser as the excitation source at 325 nm. These highly oriented ZnO/SnO2-composite film are potential for the creation of functional materials, such as the sensors, solar cells and etc.
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Antibacterial activity of oregano (Origanum vulgare Linn.) against gram positive bacteria.
Saeed, Sabahat; Tariq, Perween
2009-10-01
The present investigation is focused on antibacterial potential of infusion, decoction and essential oil of oregano (Origanum vulgare) against 111 Gram-positive bacterial isolates belonging to 23 different species related to 3 genera. Infusion and essential oil exhibited antibacterial activity against Staphylococcus saprophyticus, S. aureus, Micrococcus roseus, M. kristinae, M. nishinomiyaensis, M. lylae, M. luteus, M. sedentarius, M. varians, Bacillus megaterium, B. thuringiensis, B. alvei, B. circulans, B. brevis, B. coagulans, B. pumilus, B. laterosporus, B. polymyxa, B. macerans, B. subtilis, B. firmus, B. cereus and B. lichiniformis. The infusion exhibited maximum activity against B. laterosporus (17.5 mm mean zone of inhibition+/-1.5 Standard deviation) followed by B. polymyxa (17.0 mm+/-2.0 SD) and essential oil of oregano exhibited maximum activity against S. saprophyticus (16.8 mm+/-1.8 SD) followed by B. circulans (14.5 mm+/-0.5 SD). While all these tested isolates were found resistant to decoction of oregano.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hu, E; Lasio, G; Yi, B
2014-06-01
Purpose: The Iterative Subtraction Algorithm (ISA) method generates retrospectively a pre-selected motion phase cone-beam CT image from the full motion cone-beam CT acquired at standard rotation speed. This work evaluates ISA method with real lung patient data. Methods: The goal of the ISA algorithm is to extract motion and no- motion components form the full reconstruction CBCT. The workflow consists of subtracting from the full CBCT all of the undesired motion phases and obtain a motion de-blurred single-phase CBCT image, followed by iteration of this subtraction process. ISA is realized as follows: 1) The projections are sorted to various phases,more » and from all phases, a full reconstruction is performed to generate an image CTM. 2) Generate forward projections of CTM at the desired phase projection angles, the subtraction of projection and the forward projection will reconstruct a CTSub1, which diminishes the desired phase component. 3) By adding back the CTSub1 to CTm, no motion CBCT, CTS1, can be computed. 4) CTS1 still contains residual motion component. 5) This residual motion component can be further reduced by iteration.The ISA 4DCBCT technique was implemented using Varian Trilogy accelerator OBI system. To evaluate the method, a lung patient CBCT dataset was used. The reconstruction algorithm is FDK. Results: The single phase CBCT reconstruction generated via ISA successfully isolates the desired motion phase from the full motion CBCT, effectively reducing motion blur. It also shows improved image quality, with reduced streak artifacts with respect to the reconstructions from unprocessed phase-sorted projections only. Conclusion: A CBCT motion de-blurring algorithm, ISA, has been developed and evaluated with lung patient data. The algorithm allows improved visualization of a single phase motion extracted from a standard CBCT dataset. This study has been supported by National Institute of Health through R01CA133539.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Dong, X; Petrongolo, M; Wang, T
Purpose: A general problem of dual-energy CT (DECT) is that the decomposition is sensitive to noise in the two sets of dual-energy projection data, resulting in severely degraded qualities of decomposed images. We have previously proposed an iterative denoising method for DECT. Using a linear decomposition function, the method does not gain the full benefits of DECT on beam-hardening correction. In this work, we expand the framework of our iterative method to include non-linear decomposition models for noise suppression in DECT. Methods: We first obtain decomposed projections, which are free of beam-hardening artifacts, using a lookup table pre-measured on amore » calibration phantom. First-pass material images with high noise are reconstructed from the decomposed projections using standard filter-backprojection reconstruction. Noise on the decomposed images is then suppressed by an iterative method, which is formulated in the form of least-square estimation with smoothness regularization. Based on the design principles of a best linear unbiased estimator, we include the inverse of the estimated variance-covariance matrix of the decomposed images as the penalty weight in the least-square term. Analytical formulae are derived to compute the variance-covariance matrix from the measured decomposition lookup table. Results: We have evaluated the proposed method via phantom studies. Using non-linear decomposition, our method effectively suppresses the streaking artifacts of beam-hardening and obtains more uniform images than our previous approach based on a linear model. The proposed method reduces the average noise standard deviation of two basis materials by one order of magnitude without sacrificing the spatial resolution. Conclusion: We propose a general framework of iterative denoising for material decomposition of DECT. Preliminary phantom studies have shown the proposed method improves the image uniformity and reduces noise level without resolution loss. In the future, we will perform more phantom studies to further validate the performance of the purposed method. This work is supported by a Varian MRA grant.« less
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TU-E-BRB-08: Dual Gated Volumetric Modulated Arc Therapy.
Wu, J; Fahimian, B; Wu, H; Xing, L
2012-06-01
Gated Volumetric Modulated Arc Therapy (VMAT) is an emerging treatment modality for Stereotactic Body Radiotherapy (SBRT). However, gating significantly prolongs treatment time. In order to enhance treatment efficiency, a novel dual gated VMAT, in which dynamic arc deliveries are executed sequentially in alternating exhale and inhale phases, is proposed and evaluated experimentally. The essence of dual gated VMAT is to take advantage of the natural pauses that occur at inspiration and exhalation by alternatively delivering the dose at the two phases, instead of the exhale window only. The arc deliveries at the two phases are realized by rotating gantry forward at the exhale window and backward at the inhale in an alternative fashion. Custom XML scripts were developed in Varian's TrueBeam STx Developer Mode to enable dual gated VMAT delivery. RapidArc plans for a lung case were generated for both inhale and exhale phases. The two plans were then combined into a dual gated arc by interleaving the arc treatment nodes of the two RapidArc plans. The dual gated plan was delivered in the development mode of TrueBeam LINAC onto a motion phantom and the delivery was measured by using pinpoint chamber/film/diode array (delta 4). The measured dose distribution was compared with that computed using Eclipse AAA algorithm. The treatment delivery time was recorded and compared with the corresponding single gated plans. Relative to the corresponding single gated delivery, it was found that treatment time efficiency was improved by 95.5% for the case studied here. Pinpoint chamber absolute dose measurement agreed the calculation to within 0.7%. Diode chamber array measurements revealed that 97.5% of measurement points of dual gated RapidArc delivery passed the 3% and 3mm gamma-test criterion. A dual gated VMAT treatment has been developed and implemented successfully with nearly doubled treatment delivery efficiency. © 2012 American Association of Physicists in Medicine.
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Coscia, Gianluca; Vaccara, Elena; Corvisiero, Roberta; Cavazzani, Paolo; Ruggieri, Filippo Grillo; Taccini, Gianni
2009-07-01
In the authors' hospital, stereotactic radiotherapy treatments are performed with a Varian Clinac 600C equipped with a BrainLAB m3 micro-multileaf-collimator generally using the dynamic conformal arc technique. Patient immobilization during the treatment is achieved with a fixation mask supplied by BrainLAB, made with two reinforced thermoplastic sheets fitting the patient's head. With this work the authors propose a method to evaluate treatment geometric accuracy and, consequently, to determine the amount of the margin to keep in the CTV-PTV expansion during the treatment planning. The reproducibility of the isocenter position was tested by simulating a complete treatment on the anthropomorphic phantom Alderson Rando, inserting in between two phantom slices a high sensitivity Gafchromic EBT film, properly prepared and calibrated, and repeating several treatment sessions, each time removing the fixing mask and replacing the film inside the phantom. The comparison between the dose distributions measured on films and computed by TPS, after a precise image registration procedure performed by a commercial piece of software (FILMQA, 3cognition LLC (Division of ISP), Wayne, NJ), allowed the authors to measure the repositioning errors, obtaining about 0.5 mm in case of central spherical PTV and about 1.5 mm in case of peripheral irregular PTV. Moreover, an evaluation of the errors in the registration procedure was performed, giving negligible values with respect to the quantities to be measured. The above intrinsic two-dimensional estimate of treatment accuracy has to be increased for the error in the third dimension, but the 2 mm margin the authors generally use for the CTV-PTV expansion seems adequate anyway. Using the same EBT films, a dosimetric verification of the treatment planning system was done. Measured dose values are larger or smaller than the nominal ones depending on geometric irradiation conditions, but, in the authors' experimental conditions, always within 4%.
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SU-F-T-626: Intracranial SRS Re-Treatment Without Acquisition of New CT Images
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wiant, D; Manning, M; Liu, H
Purpose: Linear accelerator based stereotactic radiosurgery (SRS) for multiple intracranial lesions with frequent surveillance is becoming a popular treatment option. This strategy leads to retreatment with SRS as new lesions arise. Currently, each course of treatment uses magnetic resonance (MR) and computed tomography (CT) images for treatment planning. We propose that new MR images, with course 1 CT images, may be used for future treatment plans with negligible loss of dosimetric accuracy. Methods: Ten patients that received multiple courses of SRS were retrospectively reviewed. The treatment plans and contours from non-initial courses were copied to the initial CTs and recalculated.more » Doses metrics for the plans calculated on the initial CTs and later CTs were compared. All CT scans were acquired on a Philips CT scanner with a 600 mm field of view and 1 mm slice thickness (Philips Healthcare, Andover, MA). All targets were planned to 20 Gy and calculated in Eclipse V. 13.6 (Varian, Palo Alto, CA) using analytic anisotropic algorithm with 1 mm calculation grid. Results: Sixteen lesions were evaluated. The mean time between courses was 250 +/− 215 days (range 103–979). The mean target volume was 2.0 +/− 2.9 cc (range 0.1–10.1). The average difference in mean target dose between the two calculations was 0.2 +/− 0.3 Gy (range 0.0 – 1.0). The mean conformity index (CI) was 1.28 +/− 0.14 (range 1.07 – 1.82). The average difference in CI was 0.03 +/− 0.16 (range 0.00 – 0.44). Targets volumes < 0.5 cc showed the largest changes in both metrics. Conclusion: Continued treatment based on initial CT images is feasible. Dose calculation on the initial CT for future treatments provides reasonable dosimetric accuracy. Changes in dose metrics are largest for small volumes, and are likely dominated by partial volume effects in target definition.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ding, A; Han, B; Bush, K
Purpose: Dosimetric verification of VMAT/SBRT is currently performed on one or two planes in a phantom with either film or array detectors. A robust and easy-to-use 3D dosimetric tool has been sought since the advent of conformal radiation therapy. Here we present such a strategy for independent 3D VMAT/SBRT plan verification system by a combined use of EPID and cloud-based Monte Carlo (MC) dose calculation. Methods: The 3D dosimetric verification proceeds in two steps. First, the plan was delivered with a high resolution portable EPID mounted on the gantry, and the EPID-captured gantry-angle-resolved VMAT/SBRT field images were converted into fluencemore » by using the EPID pixel response function derived from MC simulations. The fluence was resampled and used as the input for an in-house developed Amazon cloud-based MC software to reconstruct the 3D dose distribution. The accuracy of the developed 3D dosimetric tool was assessed using a Delta4 phantom with various field sizes (square, circular, rectangular, and irregular MLC fields) and different patient cases. The method was applied to validate VMAT/SBRT plans using WFF and FFF photon beams (Varian TrueBeam STX). Results: It was found that the proposed method yielded results consistent with the Delta4 measurements. For points on the two detector planes, a good agreement within 1.5% were found for all the testing fields. Patient VMAT/SBRT plan studies revealed similar level of accuracy: an average γ-index passing rate of 99.2± 0.6% (3mm/3%), 97.4± 2.4% (2mm/2%), and 72.6± 8.4 % ( 1mm/1%). Conclusion: A valuable 3D dosimetric verification strategy has been developed for VMAT/SBRT plan validation. The technique provides a viable solution for a number of intractable dosimetry problems, such as small fields and plans with high dose gradient.« less
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SU-E-J-114: Web-Browser Medical Physics Applications Using HTML5 and Javascript.
Bakhtiari, M
2012-06-01
Since 2010, there has been a great attention about HTML5. Application developers and browser makers fully embrace and support the web of the future. Consumers have started to embrace HTML5, especially as more users understand the benefits and potential that HTML5 can mean for the future.Modern browsers such as Firefox, Google Chrome, and Safari are offering better and more robust support for HTML5, CSS3, and JavaScript. The idea is to introduce the HTML5 to medical physics community for open source software developments. The benefit of using HTML5 is developing portable software systems. The HTML5, CSS, and JavaScript programming languages were used to develop several applications for Quality Assurance in radiation therapy. The canvas element of HTML5 was used for handling and displaying the images, and JavaScript was used to manipulate the data. Sample application were developed to: 1. analyze the flatness and symmetry of the radiotherapy fields in a web browser, 2.analyze the Dynalog files from Varian machines, 3. visualize the animated Dynamic MLC files, 4. Simulation via Monte Carlo, and 5. interactive image manipulation. The programs showed great performance and speed in uploading the data and displaying the results. The flatness and symmetry program and Dynalog file analyzer ran in a fraction of second. The reason behind this performance is using JavaScript language which is a lower level programming language in comparison to the most of the scientific programming packages such as Matlab. The second reason is that JavaScript runs locally on client side computers not on the web-servers. HTML5 and JavaScript can be used to develop useful applications that can be run online or offline on different modern web-browsers. The programming platform can be also one of the modern web-browsers which are mostly open source (such as Firefox). © 2012 American Association of Physicists in Medicine.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Thomas, S; Yuen, C; Huang, V
Purpose: In this abstract we implement and validate a 4D VMAT Acuros XB dose calculation using Gafchromic film. Special attention is paid to the physical material assignment in the CT dataset and to reported dose to water and dose to medium. Methods: A QUASAR phantom with a 3 cm sinusoidal tumor motion and 5 second period was scanned using 4D computed tomography. A CT was also obtained of the static QUASAR phantom with the tumor at the central position. A VMAT plan was created on the average CT dataset and was delivered on a Varian TrueBeam linear accelerator. The trajectorymore » log file from this treatment was acquired and used to create 10 VMAT subplans (one for each portion of the breathing cycle). Motion for each subplan was simulated by moving the beam isocentre in the superior/inferior direction in the Treatment Planning System on the static CT scan. The 10 plans were calculated (both dose to medium and dose to water) and summed for 1) the original HU values from the static CT scan and 2) the correct physical material assignment in the CT dataset. To acquire a breathing phase synchronized film measurements the trajectory log was used to create a VMAT delivery plan which includes dynamic couch motion using the Developer Mode. Three different treatment start phases were investigated (mid inhalation, full inhalation and full exhalation). Results: For each scenario the coronal dose distributions were measured using Gafchromic film and compared to the corresponding calculation with Film QA Pro Software using a Gamma test with a 3%/3mm distance to agreement criteria. Good agreement was found between calculation and measurement. No statistically significant difference in agreement was found between calculations to original HU values vs calculations to over-written (material-assigned) HU values. Conclusion: The investigated 4D dose calculation method agrees well with measurement.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hardin, M; Elson, H; Lamba, M
2014-06-01
Purpose: To quantify the clinically observed dose enhancement adjacent to cranial titanium fixation plates during post-operative radiotherapy. Methods: Irradiation of a titanium burr hole cover was simulated using Monte Carlo code MCNPX for a 6 MV photon spectrum to investigate backscatter dose enhancement due to increased production of secondary electrons within the titanium plate. The simulated plate was placed 3 mm deep in a water phantom, and dose deposition was tallied for 0.2 mm thick cells adjacent to the entrance and exit sides of the plate. These results were compared to a simulation excluding the presence of the titanium tomore » calculate relative dose enhancement on the entrance and exit sides of the plate. To verify simulated results, two titanium burr hole covers (Synthes, Inc. and Biomet, Inc.) were irradiated with 6 MV photons in a solid water phantom containing GafChromic MD-55 film. The phantom was irradiated on a Varian 21EX linear accelerator at multiple gantry angles (0–180 degrees) to analyze the angular dependence of the backscattered radiation. Relative dose enhancement was quantified using computer software. Results: Monte Carlo simulations indicate a relative difference of 26.4% and 7.1% on the entrance and exit sides of the plate respectively. Film dosimetry results using a similar geometry indicate a relative difference of 13% and -10% on the entrance and exit sides of the plate respectively. Relative dose enhancement on the entrance side of the plate decreased with increasing gantry angle from 0 to 180 degrees. Conclusion: Film and simulation results demonstrate an increase in dose to structures immediately adjacent to cranial titanium fixation plates. Increased beam obliquity has shown to alleviate dose enhancement to some extent. These results are consistent with clinically observed effects.« less
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SU-F-E-18: Training Monthly QA of Medical Accelerators: Illustrated Instructions for Self-Learning
DOE Office of Scientific and Technical Information (OSTI.GOV)
Court, L; Wang, H; Aten, D
Purpose: To develop and test clear illustrated instructions for training of monthly mechanical QA of medical linear accelerators. Methods: Illustrated instructions were created for monthly mechanical QA with tolerance tabulated, and underwent several steps of review and refinement. Testers with zero QA experience were then recruited from our radiotherapy department (1 student, 2 computational scientists and 8 dosimetrists). The following parameters were progressively de-calibrated on a Varian C-series linac: Group A = gantry angle, ceiling laser position, X1 jaw position, couch longitudinal position, physical graticule position (5 testers); Group B = Group A + wall laser position, couch lateral andmore » vertical position, collimator angle (3 testers); Group C = Group B + couch angle, wall laser angle, and optical distance indicator (3 testers). Testers were taught how to use the linac, and then used the instructions to try to identify these errors. A physicist observed each session, giving support on machine operation, as necessary. The instructions were further tested with groups of therapists, graduate students and physics residents at multiple institutions. We have also changed the language of the instructions to simulate using the instructions with non-English speakers. Results: Testers were able to follow the instructions. They determined gantry, collimator and couch angle errors within 0.4, 0.3, and 0.9degrees of the actual changed values, respectively. Laser positions were determined within 1mm, and jaw positions within 2mm. Couch position errors were determined within 2 and 3mm for lateral/longitudinal and vertical errors, respectively. Accessory positioning errors were determined within 1mm. ODI errors were determined within 2mm when comparing with distance sticks, and 6mm when using blocks, indicating that distance sticks should be the preferred approach for inexperienced staff. Conclusion: Inexperienced users were able to follow these instructions, and catch errors within the criteria suggested by AAPM TG142 for linacs used for IMRT.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, C; Chetty, I; Mao, W
Purpose: To utilize deformable dose accumulation (DDA) to determine how cold spots within the PTV change over the course of fractionated head and neck (H&N) radiotherapy. Methods: Voxel-based dose was tracked using a DDA platform. The DDA process consisted of B-spline-based deformable image registration (DIR) and dose accumulation between planning CT’s and daily cone-beam CT’s for 10 H&N cancer patients. Cold spots within the PTV (regions receiving less than the prescription, 70 Gy) were contoured on the cumulative dose distribution. These cold spots were mapped to each fraction, starting from the first fraction to determine how they changed. Spatial correlationmore » between cold spot regions over each fraction, relative to the last fraction, was computed using the Jaccard index Jk (Mk,N), where N is the cold spot within the PTV at the end of the treatment, and Mk the same region for fraction k. Results: Figure 1 shows good spatial correlation between cold spots, and highlights expansion of the cold spot region over the course of treatment, as a result of setup uncertainties, and anatomical changes. Figure 2 shows a plot of Jk versus fraction number k averaged over 10 patients. This confirms the good spatial correlation between cold spots over the course of treatment. On average, Jk reaches ∼90% at fraction 22, suggesting that possible intervention (e.g. reoptimization) may mitigate the cold spot region. The cold spot, D99, averaged over 10 patients corresponded to a dose of ∼65 Gy, relative to the prescription dose of 70 Gy. Conclusion: DDA-based tracking provides spatial dose information, which can be used to monitor dose in different regions of the treatment plan, thereby enabling appropriate mid-treatment interventions. This work is supported in part by Varian Medical Systems, Palo Alto, CA.« less