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Sample records for linac-based isocentric electron-photon

  1. Post mastectomy chest wall irradiation using mixed electron-photon beams with or without isocentric technique.

    PubMed

    Hamdy, H K; Zikry, M S

    2008-01-01

    To describe our technique in delivering post mastectomy radiotherapy to chest wall using electron-photon mixed beam with or without isocentric application of the tangential photon portals, and to evaluate the associated acute and delayed morbidities. Twenty-two females with invasive breast cancer were subjected to modified radical mastectomy with adequate axillary dissection. All the patients have either tumour > or = 5 cm and/ or positive axillary nodes > 3. Chest wall was irradiated by a mixed beam of 6-Mev electrons (10Gy) and opposed tangential fields using 6 Mev-photons (36 Gy) followed by 6-Mev electrons boost to the scar of mastectomy for 4 Gy/2 fractions. We randomly allocated our patients to receive the photon beam with or without the isocentric technique. The mean dose to the planned target volume (PTV) by mixed beam was 44 Gy (96%) with a mean dose of 42 Gy (91%) to the overlying skin for the whole study group. In cases with right breast disease (17 cases), the mean right lung tissue volume within the PTV was 220 ml (15%). It was relatively higher with the non-iscocentric technique, 281 ml (19%), compared to the isocentric technique of 159 ml (10.5%). In cases with left breast disease (5 cases), the mean left lung volume within the PTV was 175 ml (14%). Larger volume of the lung tissue was included with the non-isocentric technique, 197 ml (16%) compared to the isocentric technique of 153 ml (12%). The mean scattered doses to the rest of the lung tissue, the rest of the heart in left breast cases, and the contra-lateral breast for the whole study group were 2.8 Gy, 1.8 Gy, and 1.4 Gy respectively and was comparable in both treatment arms. None of the cases developed any element of acute radiation related pneumonitis. Delayed radiation induced pneumonitis was seen in 2 cases (18%), with the chest wall treated with radiation with the non-isocentric technique. This study clearly demonstrated the utility of mixed beam in irradiating the chest wall after

  2. Planning and delivery comparison of six linac-based stereotactic radiosurgery techniques

    NASA Astrophysics Data System (ADS)

    Thakur, Varun Singh

    This work presents planning and delivery comparison of linac-based SRS treatment techniques currently available for single lesion cranial SRS. In total, two dedicated SRS systems (Novalis Tx, Cyberknife) and a HI-ART TomoTherapy system with six different delivery techniques are evaluated. Four delivery techniques are evaluated on a Novalis Tx system: circular cones, dynamic conformal arcs (DCA), static non-coplanar intensity modulated radiotherapy (NCP-IMRT), and volumetric modulated arc therapy (RapidArc) techniques are compared with intensity modulation based helical Tomotherapy on the HI-ART Tomotherapy system and with non-isocentric, multiple overlapping based robotic radiosurgery using the CyberKnife system. Thirteen patients are retrospectively selected for the study. The target volumes of each patient are transferred to a CT scan of a Lucy phantom (Standard Imaging Inc., Middleton, WI, USA) designed for end-to-end SRS QA. In order to evaluate the plans, several indices scoring the conformality, homogeneity and gradients in the plan are calculated and compared for each of the plans. Finally, to check the clinical deliverability of the plans and the delivery accuracy of different systems, a few targets are delivered on each system. A comparison between planned dose on treatment planning system and dose delivered on Gafchromic EBT film (ISP, Wayne, New Jersey, USA) is carried out by comparing dose beam profiles, isodose lines and by calculating gamma index.

  3. Summary of the linac based radiation sources working group

    SciTech Connect

    Ben-Zvi, I.; Corbett, J.; Johnson, E.; Kim, K.J.; Sheffield, R.

    1992-10-01

    Technological advances have occurred in the past few years that have made linac based Free-Electron Lasers (FEL) promising candidates for the generation of short wavelength radiation. Although the FELs use undulators or wigglers, they produce stimulated radiation rather than the spontaneous emission found in insertion devices on the second and third generation sources of today. This stimulated emission process endows the FEL with properties presenting unique opportunities in many fields of science. Among these characteristics are: coherence, spectral brightness, peak power,high average power. Additional scope for experimental growth is provided by the flexible pulse structure of linac based sources, making possible developments in high resolution timing experiments. Invited presentations to the working group on linac based radiation sources covered various key subjects, aiming at establishing the ground work for various machine designs. Design issues of FEL light sources were worked out in a few sessions, including sub-group sessions. We have also discussed the question of R&D necessary for the development of high quality FEL light sources. A high priority was placed on laser photocathode rf gun development, emittance preservation and FEL mechanism studies. This report describes the technological foundation for high brightness beams, the design of FELs using these beams and recommendations for research and development in FEL physics.

  4. Summary of the linac based radiation sources working group

    SciTech Connect

    Ben-Zvi, I.; Corbett, J.; Johnson, E.; Kim, K.J.; Sheffield, R.

    1992-01-01

    Technological advances have occurred in the past few years that have made linac based Free-Electron Lasers (FEL) promising candidates for the generation of short wavelength radiation. Although the FELs use undulators or wigglers, they produce stimulated radiation rather than the spontaneous emission found in insertion devices on the second and third generation sources of today. This stimulated emission process endows the FEL with properties presenting unique opportunities in many fields of science. Among these characteristics are: coherence, spectral brightness, peak power,high average power. Additional scope for experimental growth is provided by the flexible pulse structure of linac based sources, making possible developments in high resolution timing experiments. Invited presentations to the working group on linac based radiation sources covered various key subjects, aiming at establishing the ground work for various machine designs. Design issues of FEL light sources were worked out in a few sessions, including sub-group sessions. We have also discussed the question of R D necessary for the development of high quality FEL light sources. A high priority was placed on laser photocathode rf gun development, emittance preservation and FEL mechanism studies. This report describes the technological foundation for high brightness beams, the design of FELs using these beams and recommendations for research and development in FEL physics.

  5. Gamma ray pulsars. [electron-photon cascades

    NASA Technical Reports Server (NTRS)

    Oegelman, H.; Ayasli, S.; Hacinliyan, A.

    1977-01-01

    Data from the SAS-2 high-energy gamma-ray experiment reveal the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma-ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields (10 to the 12th power gauss) correspond to many radiation lengths which cause electrons to emit photons by magnetic bremsstrahlung and which cause these photons to pair-produce. The cascade develops until the mean photon energy drops below the pair-production threshold which is in the gamma-ray range; at this stage, the photons break out from the source.

  6. Coupled electron-photon radiation transport

    SciTech Connect

    Lorence, L.; Kensek, R.P.; Valdez, G.D.; Drumm, C.R.; Fan, W.C.; Powell, J.L.

    2000-01-17

    Massively-parallel computers allow detailed 3D radiation transport simulations to be performed to analyze the response of complex systems to radiation. This has been recently been demonstrated with the coupled electron-photon Monte Carlo code, ITS. To enable such calculations, the combinatorial geometry capability of ITS was improved. For greater geometrical flexibility, a version of ITS is under development that can track particles in CAD geometries. Deterministic radiation transport codes that utilize an unstructured spatial mesh are also being devised. For electron transport, the authors are investigating second-order forms of the transport equations which, when discretized, yield symmetric positive definite matrices. A novel parallelization strategy, simultaneously solving for spatial and angular unknowns, has been applied to the even- and odd-parity forms of the transport equation on a 2D unstructured spatial mesh. Another second-order form, the self-adjoint angular flux transport equation, also shows promise for electron transport.

  7. Poster — Thur Eve — 65: A dosimetric comparison of isocentric and non-isocentric coplanar SBRT VMAT plans for peripheral lung tumours

    SciTech Connect

    Conroy, L; Liu, HW; Lau, H; Smith, WL

    2014-08-15

    Volumetric modulated arc therapy (VMAT) delivers lung sterotactic body radiotherapy (SBRT) in shorter treatment time and less monitor units with comparable coverage and organ at risk sparing compared to conventional SBRT treatments. Isocentric VMAT treatment of peripheral lung tumours occasionally requires couch shifts that can inhibit 360° gantry rotation, resulting in additional imaging shifts for each treatment session, and increased potential for involuntary in-fraction motion. Here, we investigate whether non-isocentric VMAT plans can achieve comparable plan quality to isocentric plans for peripheral lung tumours. Three patient plans were selected with targets displaced > 8.5 cm (range: 8.8 – 9.9 cm) laterally from patient midline. For each patient, a plan with isocentre placed within the target volume (isocentric plan) was created and optimized. The same optimization parameters were then used to create a plan with the isocentre at patient midline (non-isocentric plan). Plan quality was evaluated and compared based on planning target volume (PTV) coverage, high dose spillage, dose homogeneity, intermediate dose spillage, dose fall-off gradient, and organ at risk contraints. Non-isocentric plans of equivalent plan quality to isocentric plans were achieved for all patients by optimizing collimator rotations. Field isocentres can be placed at patient midline, as opposed to inside the target volume, with no significant degradation in VMAT plan quality for lateral tumour displacements up to 10 cm. Non-isocentric treatment of peripheral lung tumours could result in decreased overall treatment session time and eliminate the need for imaging shifts prior to VMAT treatment.

  8. Linac based photofission inspection system employing novel detection concepts

    NASA Astrophysics Data System (ADS)

    Stevenson, John; Gozani, Tsahi; Elsalim, Mashal; Condron, Cathie; Brown, Craig

    2011-10-01

    Rapiscan Systems is developing a LINAC based cargo inspection system for detection of special nuclear material (SNM) in cargo containers. The system, called Photofission Based Alarm Resolution (PBAR) is being developed under a DHD/DNDO Advanced Technology Demonstration (ATD) program. The PBAR system is based on the Rapiscan Eagle P9000 X-ray system, which is a portal system with a commercial 9 MeV LINAC X-ray source. For the purposes of the DNDO ATD program, a conveyor system was installed in the portal to allow scanning and precise positioning of 20 ft ISO cargo containers. The system uses a two step inspection process. In the first step, the basic scan, the container is quickly and completely inspected using two independent radiography arrays: the conventional primary array with high spatial resolution and a lower resolution spectroscopic array employing the novel Z-Spec method. The primary array uses cadmium tungstate (CdWO 4) detectors with conventional current mode readouts using photodiodes. The Z-Spec array uses small plastic scintillators capable of performing very fast (up to 10 8 cps) gamma-ray spectroscopy. The two radiography arrays are used to locate high-Z objects in the image such as lead, tungsten, uranium, which could be potential shielding materials as well as SNM itself. In the current system, the Z-Spec works by measuring the energy spectrum of transmitted X-rays. For high-Z materials the higher end of the energy spectrum is more attenuated than for low-Z materials and thus has a lower mean energy and a narrower width than low- and medium-Z materials. The second step in the inspection process is the direct scan or alarm clearing scan. In this step, areas of the container image, which were identified as high Z, are re-inspected. This is done by precisely repositioning the container to the location of the high-Z object and performing a stationary irradiation of the area with X-ray beam. Since there are a large number of photons in the 9 MV

  9. The linear accelerator mechanical and radiation isocentre assessment with an electronic portal imaging device (EPID).

    PubMed

    Liu, G; van Doorn, T; Bezak, E

    2004-09-01

    Regular checks on the performance of radiotherapy treatment units are essential and a variety of protocols has been published. These protocols identify that the determination of isocentre must be accurate and unambiguous since both the localization of a radiation field on a patient and positioning aids are referenced to it. An EPID (BIS 710) with a combined light and radiation scintillation detector screen was used to assess mechanical and radiation isocentres for different collimator and gantry angles. Crosshair positions within light field images were determined from fitted Gaussian intensity profiles and then used to calculate the displacement of the mechanical isocentre. For comparison, the position of the crosshair was also recorded on a graph paper. The radiation field centre was first calculated from the set up geometry for given gantry/collimator angles and then compared with measured values to assess the displacement of the radiation isocentre. The radiation isocentre was also checked by locating a marker, positioned on the couch, on the EPID radiation images for different treatment couch angles. The mechanical and radiation isocentres were determined from the EPID light field and radiation images respectively with an accuracy of 0.3 mm using simple PC based programs. The study has demonstrated the feasibility of using the EPID to assess mechanical and radiation isocentres of a linear accelerator in a quick and efficient way with a higher degree of accuracy achieved as compared to more conventional methods, e.g. the star shot.

  10. Isocentric stereotactic three-dimensional digitizer for neurosurgery.

    PubMed

    Takizawa, T

    1993-01-01

    A new system has been developed, comprising a frameless isocentric stereotactic mechanism and a three-dimensional (3-D) digitizer for intraoperative spatial monitoring. The 3-D digitizer's multiarticulated arm has three joints related to Cartesian coordinates, two quadrant arcs forming an isocenter system, a microdrive, and a probe holder. The frameless isocentric mechanism is useful for open stereotaxy. Routine CT- or MRI-guided stereotactic surgery is also possible, due to the high level of accuracy of the system. Before surgery, CT and/or MR images are acquired after placing on the scalp three or four external markers. For surgical procedures which require high accuracy, Laitinen's noninvasive CT or MRI localizing markers are used. CT or MR images are entered into a computer using an image scanner, and are stored on a floppy disk. After the patient's head is fixed to the operating table using a Mayfield clamp, the 3-D digitizer is used to read the spatial points and external markers on the scalp or the reference points of Laitinen's localizing markers. During the procedure, the coordinates on the patient's head are automatically entered into the computer and matched with those of the 3-D digitizer and CT/MR images on the CRT display. This system has been used in 22 cases of open craniotomy and 33 cases of burr hole surgery, both carried out using the stereotactic function and the 3-D spatial monitoring function in parallel. Errors in mechanical accuracy of the 3-D digitizer were less than 0.8 mm, and the maximum error during operation was presumed not to exceed 2 mm.

  11. Electron/Photon Verification Calculations Using MCNP4B

    SciTech Connect

    D. P. Gierga; K. J. Adams

    1999-04-01

    MCNP4BW was released in February 1997 with significant enhancements to electron/photon transport methods. These enhancements have been verified against a wide range of published electron/photon experiments, spanning high energy bremsstrahlung production to electron transmission and reflection. The impact of several MCNP tally options and physics parameters was explored in detail. The agreement between experiment and simulation was usually within two standard deviations of the experimental and calculational errors. Furthermore, sub-step artifacts for bremsstrahlung production were shown to be mitigated. A detailed suite of electron depth dose calculations in water is also presented. Areas for future code development have also been explored and include the dependence of cell and detector tallies on different bremsstrahlung angular models and alternative variance reduction splitting schemes for bremsstrahlung production.

  12. Stereotactic radiosurgery for intracranial metastases: linac-based and gamma-dedicated unit approach.

    PubMed

    Alongi, Filippo; Fiorentino, Alba; Mancosu, Pietro; Navarria, Pierina; Giaj Levra, Niccolò; Mazzola, Rosario; Scorsetti, Marta

    2016-07-01

    For intracranial metastases, the role of stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy is well recognized. Historically, the first technology, for stereotactic device able to irradiate a brain tumor volume, was Gamma Knife® (GK). Due to the technological advancement of linear accelerator (Linac), there was a continuous increasing interest in SRS Linac-based applications. In those decades, it was assumed a superiority of GK compared to SRS Linac-based for brain tumor in terms of dose conformity and rapid fall-off dose close to the target. Expert commentary: Recently, due to the Linac technologic advancement, the choice of SRS GK-based is not necessarily so exclusive. The current review discussed in details the technical and clinical aspects comparing the two approaches for brain metastases.

  13. Electronic/photonic interfaces for ultrafast data processing.

    SciTech Connect

    Overberg, Mark E.; Geib, Kent Martin; Serkland, Darwin Keith; Hsu, Alan Yuan-Chun; Keeler, Gordon Arthur; Finnegan, Patrick Sean

    2008-09-01

    This report summarizes a 3-month program that explored the potential areas of impact for electronic/photonic integration technologies, as applied to next-generation data processing systems operating within 100+ Gb/s optical networks. The study included a technology review that targeted three key functions of data processing systems, namely receive/demultiplexing/clock recovery, data processing, and transmit/multiplexing. Various technical approaches were described and evaluated. In addition, we initiated the development of high-speed photodetectors and hybrid integration processes, two key elements of an ultrafast data processor. Relevant experimental results are described herein.

  14. An Electron/Photon/Relaxation Data Library for MCNP6

    SciTech Connect

    Hughes, III, H. Grady

    2015-08-07

    The capabilities of the MCNP6 Monte Carlo code in simulation of electron transport, photon transport, and atomic relaxation have recently been significantly expanded. The enhancements include not only the extension of existing data and methods to lower energies, but also the introduction of new categories of data and methods. Support of these new capabilities has required major additions to and redesign of the associated data tables. In this paper we present the first complete documentation of the contents and format of the new electron-photon-relaxation data library now available with the initial production release of MCNP6.

  15. Radial Moment Calculations of Coupled Electron-Photon Beams

    SciTech Connect

    FRANKE,BRIAN C.; LARSEN,EDWARD W.

    2000-07-19

    The authors consider the steady-state transport of normally incident pencil beams of radiation in slabs of material. A method has been developed for determining the exact radial moments of 3-D beams of radiation as a function of depth into the slab, by solving systems of 1-D transport equations. They implement these radial moment equations in the ONEBFP discrete ordinates code and simulate energy-dependent, coupled electron-photon beams using CEPXS-generated cross sections. Modified P{sub N} synthetic acceleration is employed to speed up the iterative convergence of the 1-D charged particle calculations. For high-energy photon beams, a hybrid Monte Carlo/discrete ordinates method is examined. They demonstrate the efficiency of the calculations and make comparisons with 3-D Monte Carlo calculations. Thus, by solving 1-D transport equations, they obtain realistic multidimensional information concerning the broadening of electron-photon beams. This information is relevant to fields such as industrial radiography, medical imaging, radiation oncology, particle accelerators, and lasers.

  16. Electron photon verification calculations using MCNP4B

    SciTech Connect

    Gierga, D.P.; Adams, K.J.

    1998-07-01

    MCNP4B was released in February 1997 with significant enhancements to electron/photon transport methods. These enhancements have been verified against a wide range of published electron/photon experiments, spanning high energy bremsstrahlung production to electron transmission and reflection. Three sets of bremsstrahlung experiments were simulated. The first verification calculations for bremsstrahlung production used the experimental results in Faddegon for 15 MeV electrons incident on lead, aluminum, and beryllium targets. The calculated integrated bremsstrahlung yields, the bremsstrahlung energy spectra, and the mean energy of the bremsstrahlung beam were compared with experiment. The impact of several MCNP tally options and physics parameters was explored in detail. The second was the experiment of O`Dell which measured the bremsstrahlung spectra from 10 and 20.9 MeV electrons incident on a gold/tungsten target. The final set was a comparison of relative experimental spectra with calculated results for 9.66 MeV electrons incident on tungsten based on the experiment of Starfelt and Koch. The transmission experiments of Ebert were also studied, including comparisons of transmission coefficients for 10.2 MeV electrons incident on carbon, silver, and uranium foils. The agreement between experiment and simulation was usually within two standard deviations of the experimental and calculational errors.

  17. A new approach to quantify the mechanical and radiation isocentres of radiotherapy treatment machine gantries

    NASA Astrophysics Data System (ADS)

    Skworcow, Piotr; Mills, John A.; Haas, Olivier C. L.; Burnham, Keith J.

    2007-12-01

    In this paper a new method is proposed to quantify and reduce the radiation beam position uncertainty due to the radiotherapy treatment machine gantry deflection. A new tool has been designed and manufactured to provide the means to measure the alignment of the collimator axis and of the beam central axis in space, using the NDI Polaris optical tracking system and Gafchromic® films. The tool can be mounted onto the accessory tray of the linacs from different manufacturers. The approach has been demonstrated with measurements of the mechanical isocentre being performed on ten linacs from three major manufacturers at four clinical sites. Measurements of the radiation isocentre were performed on a single linac. The collimator axis trajectory is modelled using a vector-end effector in order to provide more information than standard mechanical assessment methods. The method uses a mathematical optimization technique to calculate the position of the mechanical isocentre and the 'size' of the collimator axes intersection locus. Deviations of the collimator axes from the isocentre are expressed in terms of systematic and random error. The effects of measurement uncertainties are evaluated both via simulations and experimentally. The use of optical tracking and optimization techniques combined with an operator-induced measurement error compensation algorithm leads to a faster measurement of the mechanical isocentre (20 min for 24 angles) and eliminates operator-induced uncertainties. The uncertainty of the measurement of the mechanical isocentre was between 40 µm and 70 µm in terms of standard deviation. For some of the linacs assessed, the mechanical isocentre obtained using a standard approach with an adjustable pointer was displaced by over 1 mm from that found with the proposed method. The radii of the collimator axes intersection locus found with the proposed method were between 0.4 mm and 0.72 mm for the linacs assessed. Film measurement revealed a misalignment of

  18. Induction-linac based free-electron laser amplifiers for plasma heating

    SciTech Connect

    Jong, R.A.

    1988-08-22

    We describe an induction-linac based free-electron laser amplifier that is presently under construction at the Lawrence Livermore National Laboratory. It is designed to produce up to 2 MW of average power at a frequency of 250 GHz for plasma heating experiments in the Microwave Tokamak Experiment. In addition, we shall describe a FEL amplifier design for plasma heating of advanced tokamak fusion devices. This system is designed to produce average power levels of about 10 MW at frequencies ranging form 280 to 560 GHz. 7 refs., 1 tab.

  19. Induction-linac based free-electron laser amplifiers for plasma heating

    NASA Astrophysics Data System (ADS)

    Jong, R. A.

    1988-08-01

    We describe an induction-linac based free-electron laser amplifier that is presently under construction at the Lawrence Livermore National Laboratory. It is designed to produce up to 2 MW of average power at a frequency of 250 GHz for plasma heating experiments in the Microwave Tokamak Experiment. In addition, we shall describe a FEL amplifier design for plasma heating of advanced tokamak fusion devices. This system is designed to produce average power levels of about 10 MW at frequencies ranging from 280 to 560 GHz.

  20. Magnetic field contribution to the last electron-photon scattering

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2010-11-01

    When the cosmic microwave photons scatter electrons just prior to the decoupling of matter and radiation, magnetic fields do contribute to the Stokes matrix as well as to the scalar, vector and tensor components of the transport equations for the brightness perturbations. The magnetized electron-photon scattering is hereby discussed in general terms by including, for the first time, the contribution of magnetic fields with arbitrary direction and in the presence of the scalar, vector and tensor modes of the geometry. The propagation of relic vectors and relic gravitons is discussed for a varying magnetic field orientation and for different photon directions. The source terms of the transport equations in the presence of the relativistic fluctuations of the geometry are also explicitly averaged over the magnetic field orientations and the problem of a consistent account of the small-scale and large-scale magnetic field is briefly outlined.

  1. The virtual isocentric aiming device: a new mechanical targeting concept.

    PubMed

    Mendel, Thomas; Hänni, Markus; Gueorguiev, Boyko; Wohlrab, David; Hofmann, Gunther Olaf

    2011-12-01

    Minimally invasive fracture fixation can be technically demanding, especially in body regions characterised by complex bone anatomy and the presence of a significant amount of soft tissue. Hence, this procedure is associated with a high risk of implant malposition. As a consequence, radiation exposure to the patient and the surgeon increases within surgery. The purpose of this study was to evaluate the practicability and accuracy of a newly designed virtual isocentric aiming device (VIAD) as compared to the more traditional approach of the freehand insertion of K-wires. Forty polyurethane foam blocks were prepared with a reference wire (W ( R )) and covered by sponge material to simulate soft tissue. For the sake of comparison, both an untrained and an experienced surgeon were selected for the study and were advised to insert a K-wire into the foam block so as to have the same axis as the W ( R ) using both of the aforementioned methods. The clinical parameters of both techniques were analysed. In addition, 3-D precision data computed using CT-scans of each sample were evaluated. Device adjustment prolonged the time required for the experienced surgeon to complete the VIAD procedure when compared to the freehand method. However, using the VIAD, the number of plane changes made to the image intensifier in addition to the number of drill trials was significantly reduced by each surgeon. Furthermore, mechanical K-wire navigation leads to a decrease in the radiation exposure time for the untrained surgeon. VIAD-guided K-wires revealed a significant lower angle of deviation in relation to W ( R ). Tip-to-tip and tip-to-axis distances displayed a trend indicating reduced displacement values as well. The VIAD allows for simple wire insertion with increased precision as well as a reduction in radiation exposure, plane changes of the image intensifier and the number of drill trials compared to the freehand method. The VIAD also satisfies the demand for a less invasive

  2. Dosimetric comparison of helical tomothearpy and linac-based IMRT in whole abdomen radiotherapy

    NASA Astrophysics Data System (ADS)

    Kang, Young-nam; Kim, Dae-Hyun; Jang, Hong Seok; Song, Jin Ho; Choi, Byung Ock; Cho, Seok Goo; Jung, Ji-Young; Kay, Chul Seung

    2012-10-01

    Recent advances in radiotherapy techniques have allowed a significant improvement in the therapeutic ratio of whole abdominal irradiation (WAI) through linear-accelerator (Linac) based intensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT). IMRT has been shown to reduce the dose to organs at risk (OAR) while adequately treating the tumor volume. HT operates by adjusting 51 beam directions, couch speed, pitch and shapes of a binary multileaf collimator (MLC), with the purpose of clinically increasing the befit to the patient. We incorporated helical tomotherapy as a new modality for WAI for the treatment of non-Hodgkin's lymphoma patients whose disease involved the intestine and the mesenteric lymph nodes. Excellent tumor coverage with effective sparing of normal organ sparings, and homogeneous dose distribution could be achieved. This study dosimetrically compared HT and linac-based IMRT by using several indices, including the conformity index (CI) and the homogeneity index (HI) for the planning target volume (PTV), as well as the, max dose and the mean dose and the quality index (QI) for five organs at risk (OARs). The HI and the CI were used to compare the quality of target coverage while the QI was used compare the dosimetric performans for OAR systems. The target coverages between the two systems were similar, but the most QIs were lower than 1, what means that HT is batter at sparing OARs than IMRT. Tomotherapy enabled excellent target coverage, effective sparing of normal tissues, and homogeneous dose distribution without severe acute toxicity.

  3. On isocentre adjustment and quality control in linear accelerator based radiosurgery with circular collimators and room lasers.

    PubMed

    Treuer, H; Hoevels, M; Luyken, K; Gierich, A; Kocher, M; Müller, R P; Sturm, V

    2000-08-01

    We have developed a densitometric method for measuring the isocentric accuracy and the accuracy of marking the isocentre position for linear accelerator based radiosurgery with circular collimators and room lasers. Isocentric shots are used to determine the accuracy of marking the isocentre position with room lasers and star shots are used to determine the wobble of the gantry and table rotation movement, the effect of gantry sag, the stereotactic collimator alignment, and the minimal distance between gantry and table rotation axes. Since the method is based on densitometric measurements, beam spot stability is implicitly tested. The method developed is also suitable for quality assurance and has proved to be useful in optimizing isocentric accuracy. The method is simple to perform and only requires a film box and film scanner for instrumentation. Thus, the method has the potential to become widely available and may therefore be useful in standardizing the description of linear accelerator based radiosurgical systems.

  4. Optimizing LINAC-based stereotactic radiotherapy of uveal melanomas: 7 years' clinical experience

    SciTech Connect

    Dieckmann, Karin . E-mail: Karin.Dieckmann@akhwien.at; Georg, Dietmar; Bogner, Joachim; Zehetmayer, Martin; Petersch, Bernhard; Chorvat, Martin; Weitmann, Hajo; Poetter, Richard

    2006-11-15

    Purpose: To report on the clinical outcome of LINAC-based stereotactic radiotherapy (SRT) of uveal melanomas. Additionally, a new prototype (hardware and software) for automated eye monitoring and gated SRT using a noninvasive eye fixation technique is described. Patients and Methods: Between June 1997 and March 2004, 158 patients suffering from uveal melanoma were treated at a LINAC with 6 MV (5 x 14 Gy; 5 x 12 Gy prescribed to 80% isodose) photon beams. To guarantee identical patient setup during treatment planning (CT and MRI) and treatment delivery, patients were immobilized with a BrainLAB thermoplastic mask. Eye immobilization was achieved by instructing the patient to fixate on a light source integrated into the mask system. A mini-video camera was used to provide on-line information about the eye and pupil position, respectively. A new CT and magnetic resonance (MR) compatible prototype, based on head-and-neck fixation and the infrared tracking system ExacTrac, has been developed and evaluated since 2002. This system records maximum temporal and angular deviations during treatment and, based on tolerance limits, a feedback signal to the LINAC enables gated SRT. Results: After a median follow-up of 33.4 months (range, 3-85 months), local control was achieved in 98%. Fifteen patients (9.0%) developed metastases. Secondary enucleation was performed in 23 patients (13.8%). Long-term side effects were retinopathy (n = 70; 44%), cataract (n = 30; 23%), optic neuropathy (n = 65; 41%), and secondary neovascular glaucoma (n = 23; 13.8%). Typical situations when preset deviation criteria were exceeded were slow drifts (fatigue), large sudden eye movements (irritation), or eye closing (fatigue). In these cases, radiation was reliably interrupted by the gating system. In our clinical setup, the novel system for computer-controlled gated SRT of uveal melanoma was well tolerated by about 30 of the patients treated with this system so far. Conclusion: LINAC-based SRT of

  5. A photocathode rf gun design for a mm-wave linac-based FEL

    SciTech Connect

    Nassiri, A.; Berenc, T,; Foster, J.; Waldschmidt, G.; Zhou, J.

    1995-07-01

    In recent years, advances in the rf gun technology have made it possible to produce small beam emittances suitable for short period microundulators which take advantage of the low emittance beam to reduce the wavelength of FELs. At the Advanced Photon Source, we are studying the design of a compact 50-MeV superconducting mm-wave linac-based FEL for the production of short wavelengths ({approximately}300 nm) to carry out FEL demonstration experiments. The electron source considered for the linac is a 30- GHz, 3 1/2-cell {pi}-mode photocathode rf gun. For cold model rf measurements a 15-GHz prototype structure was fabricated. Here we report on the design, numerical modelling and the initial cold-model rf measurement results on the 15-GHz prototype structure.

  6. High Repetition Rate, LINAC-Based Nuclear Resonance Fluorescence FY 2008 Final Report

    SciTech Connect

    Scott M Watson; Mathew T Kinlaw; James L Jones; Alan W. Hunt; Glen A. Warren

    2008-12-01

    This summarizes the first year of a multi-laboratory/university, multi-year effort focusing on high repetition rate, pulsed LINAC-based nuclear resonance fluorescence (NRF) measurements. Specifically, this FY2008 effort centered on experimentally assessing NRF measurements using pulsed linear electron accelerators, operated at various repetition rates, and identifying specific detection requirements to optimize such measurements. Traditionally, interest in NRF as a detection technology, which continues to receive funding from DHS and DOE/NA-22, has been driven by continuous-wave (CW), Van de Graff-based bremsstrahlung sources. However, in addition to the relatively sparse present-day use of Van de Graff sources, only limited NRF data from special nuclear materials has been presented; there is even less data available regarding shielding effects and photon source optimization for NRF measurements on selected nuclear materials.

  7. Time delay measurement for linac based treatment delivery in synchronized respiratory gating radiotherapy

    SciTech Connect

    Jin Jianyue; Yin Fangfang

    2005-05-01

    A time delay in a respiratory gating system could cause an unexpected phase mismatch for synchronized gating radiotherapy. This study presents a method of identifying and measuring the time delay in a gating system. Various port films were taken for a motion phantom at different gating window levels with a very narrow window size. The time delay for the gating system was determined by comparing the motion curve (the position of a moving object versus the gating time) measured in the port films to the motion curve determined by the video cameras. The measured time delay for a linac-based gating system was 0.17{+-}0.03 s. This time delay could induce target missing if it was not properly taken into account for the synchronized gating radiotherapy. Measurement/verification of the time delay should be considered as an important part of the accepting/commissioning test before the clinical use of the gating system.

  8. Odontoid screw placement using Isocentric 3-dimensional C-arm fluoroscopy.

    PubMed

    Summers, Lori E; Kouri, Joshua G; Yang, Mu; Patrick Jacob, R

    2008-02-01

    We describe the use of isocentric 3-dimensional fluoroscopy to place odontoid screws in 9 patients. We wanted to show the benefits of using isocentric 3-dimensional fluroscopy in odontoid screw placement. Odontoid screw fixation for treatment of type II odontoid fractures has gained popularity since its introduction in the early 1980s. During the last several years, a multitude of new techniques have improved the ease of odontoid screw placement, including biplanar fluoroscopy, cannulated screw systems, and beveled bedside-fixed retractor systems. The use of isocentric C-arm fluoroscopy can improve the ease and facilitate placement of odontoid screws. Nine patients, ranging in ages from 30 to 89 years, presented with type II odontoid fractures. All fractures were either nondisplaced or minimally displaced (<4 mm) and occurred as a result of acute trauma. No patient had evidence of transverse atlantal ligament disruption. Isocentric 3-dimensional fluoroscopy, in conjunction with image-guided navigational software, was used to place 1 or 2 odontoid screws in each patient. Three-dimensional images were acquired intraoperatively, which were then reconstructed and uploaded to the navigational workstation. Screw trajectory was planned and performed with the use of tracked instruments. Successful screw placement, as judged by intraoperative computerized tomography, was attained in all 9 patients. Isocentric 3-dimensional fluoroscopy, in conjunction with an image-guided navigational software system, obviates the need for cumbersome biplanar fluoroscopy, allows for intraoperative image acquisition after surgical exposure, reduces intraoperative registration time, reduces both surgeon and patient radiation exposure, and allows immediate computerized tomographic imaging in the operating room to verify screw position.

  9. Linac-based stereotactic radiotherapy and radiosurgery in patients with meningioma

    PubMed Central

    2014-01-01

    Background It was our purpose to analyze long-term clinical outcome and to identify prognostic factors after Linac-based fractionated stereotactic radiotherapy (Linac-based FSRT) and stereotactic radiosurgery (SRS) in patients with intracranial meningiomas. Materials and methods Between 10/1995 and 03/2009, 297 patients with a median age of 59 years were treated with FSRT for intracranial meningioma. 50 patients had a Grade I meningioma, 20 patients had a Grade II meningioma, 12 patients suffered from a Grade III tumor, and in 215 cases no histology was obtained (Grade 0). Of the 297 patients, 144 underwent FSRT as their primary treatment and 158 underwent postoperative FSRT. 179 patients received normofractionated radiotherapy (nFSRT), 92 patients received hypofractionated FSRT (hFSRT) and 26 patients underwent SRS. Patients with nFSRT received a mean total dose of 57.31 ± 5.82 Gy, patients with hFSRT received a mean total dose of 37.6 ± 4.4 Gy and patients who underwent SRS received a mean total dose of 17.31 ± 2.58 Gy. Results Median follow-up was 35 months. Overall progression free survival (PFS) was 92.3% at 3 years, 87% at 5 years and 84.1% at 10 years. Patients with adjuvant radiotherapy showed significantly better PFS-rates than patients who had been treated with primary radiotherapy. There was no significant difference between PFS-rates of nFSRT, hFSRT and SRS patients. PFS-rates were independent of tumor size. Patients who had received nFSRT showed less acute toxicity than those who had received hFSRT. In the Grade 0/I group the rate of radiologic focal reactions was significantly lower than in the atypical/malignant histology group. Conclusion This large study showed that FSRT is an effective and safe treatment modality with high PFS-rates for intracranial meningioma. We identified “pathological grading” and and “prior surgery” as significant prognostic factors. PMID:24650090

  10. Dosimetry of Gamma Knife and linac-based radiosurgery using radiochromic and diode detectors.

    PubMed

    Somigliana, A; Cattaneo, G M; Fiorino, C; Borelli, S; del Vecchio, A; Zonca, G; Pignoli, E; Loi, G; Calandrino, R; Marchesini, R

    1999-04-01

    In stereotactic radiosurgery the choice of appropriate detectors, whether for absolute or relative dosimetry, is very important due to the steep dose gradient and the incomplete lateral electronic equilibrium. For both linac-based and Leksell Gamma Knife radiosurgery units, we tested the use of calibrated radiochromic film to measure absolute doses and relative dose distributions. In addition a small diode was used to estimate the relative output factors. The data obtained using radiochromic and diode detectors were compared with measurements performed with other conventional methods of dosimetry, with calculated values by treatment planning systems and with data prestored in the treatment planning system supplied by the Leksell Gamma Knife (LGK) vendor. Two stereotactic radiosurgery techniques were considered: Leksell Gamma Knife (using gamma-rays from 60Co) and linac-based radiosurgery (LR) (6 MV x-rays). Different detectors were used for both relative and absolute dosimetry: relative output factors (OFs) were estimated by using radiochromic and radiographic films and a small diode; relative dose distributions in the axial and coronal planes of a spherical polystyrene phantom were measured using radiochromic film and calculated by two different treatment planning systems (TPSs). The absolute dose at the sphere centre was measured by radiochromic film and a small ionization chamber. An accurate selection of radiochromic film was made: samples of unexposed film showing a percentage standard deviation of less than 3% were used for relative dose profiles, and for absolute dose and OF evaluations this value was reduced to 1.5%. Moreover a proper calibration curve was made for each set of measurements. With regard to absolute doses, the results obtained with the ionization chamber are in good correlation with radiochromic film-generated data, for both LGK and LR, showing a dose difference of less than 1%. The output factor evaluations, performed using different methods

  11. Update on the Innovative Carbon/Proton Non-Scaling FFAG Isocentric gantries for Cancer Therapy

    SciTech Connect

    Trbojevic, D.

    2010-05-23

    There is a dramatic increase in numbers of proton/carbon cancer therapy facilities in recent years due to a clear advantage with respect to the other radiation therapy treatments. Cost of the ion cancer therapy is still to high for most of the hospitals and a dominating part comes from the delivery systems. We had previously presented design of the carbon and proton isocentric gantries using the principle of the non-scaling alternating gradient fixed field magnets (NS-FFAG), where a size and weight of the magnets should be dramatically reduced. The weight of the transport elements of the carbon isocentric gantry is estimated to be 1.5 tons compared to the 130 tons a weight of the Heidelberg gantry. The similar claim of 500 kg comes for the transport elements of the proton permanent magnet gantry. We present an update on these designs.

  12. Treatment plan comparison between stereotactic body radiation therapy techniques for prostate cancer: non-isocentric CyberKnife versus isocentric RapidArc.

    PubMed

    Lin, Yu-Wei; Lin, Kuei-Hua; Ho, Hsiu-Wen; Lin, Hsiu-Man; Lin, Li-Ching; Lee, Steve P; Chui, Chen-Shou

    2014-09-01

    The aim of this study was to evaluate the feasibility and dose distribution of two different stereotactic body radiation therapy (SBRT) techniques, isocentric RapidArc (RA) and non-isocentric CyberKnife (CK), for the treatment of localized prostate cancer. Two groups of patients (Groups 1 and 2 with ten patients per group) treated with CK were re-planned with RA. The patients were grouped according to the rectum constraint used (Group1, maximum dose for rectum; Group 2, dose-volume histogram for rectum). The prescription dose was 37.5 Gy in five fractions. The two SBRT techniques were compared by target coverage, normal tissue sparing, and dose distribution parameters. Monitor units (MUs) and the delivery time were likewise compared to assess delivery efficiency. The RA plans consistently exhibited superior PTV coverage and better rectum sparing at low doses in the both groups. The conformity and heterogeneity indices of the RA plans were better than the CK plans. Additionally, the RA plans resulted in fewer low-dose regions, lower MUs, and faster delivery times than the CK plans. The good dosimetric distribution and shorter delivery time make RA an attractive SBRT technique for the treatment of localized prostate cancer. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  13. Linac-based total body irradiation (TBI) with volumetric modulated arc therapy (VMAT)

    NASA Astrophysics Data System (ADS)

    Tas, B.; Durmus, I. F.; Okumus, A.; Uzel, O. E.

    2017-02-01

    To evaluate dose distribution of Volumetric modulated arc therapy (VMAT) planning tecnique using Versa HD® lineer accelerator to deliver Total Body Irradiation (TBI) on the coach. Eight TBI patient's Treatment Planning System (TPS) were performed with dual arc VMAT for each patient. The VMAT-TBI consisted of three isocentres and three dual overlapping arcs. The prescribed dose was 12 Gy. Mean dose to lung and kidney were restricted less than 10 Gy and max. dose to lens were restricted less than 6 Gy. The plans were verified using 2D array and ion chamber. The comparison between calculation and measurement were made by γ-index analysis and absolute dose. An average total delivery time was determined 923±34 seconds and an average MU was determined 2614±228 MUs for dual arc VMAT. Mean dose to lungs was 9.7±0.2 Gy, mean dose to kidneys was 8.8±0.3 Gy, max. dose to lens was 5.5±0.3 Gy and max. dose was 14.6±0.3 Gy, HI of PTV was 1.13±0.2, mean dose to PTV was 12.6±1.5 Gy and mean γ-index pass rate was %97.1±1.9. The results show that the tecnique for TBI using VMAT on the treatment coach is feasible.

  14. Modeling Of Induction-Linac Based Free-Electron Laser Amplifiers

    NASA Astrophysics Data System (ADS)

    Jong, Raynard A.; Fawley, William M.; Scharlemann, Ernst T.

    1989-05-01

    We describe the modeling of an induction-linac based free-electron laser (IFEL) amplifier for producing multi-megawatt levels of microwave power. We have used the Lawrence Livermore National Laboratory (LLNL) free-electron laser simulation code, FRED, and the simulation code for sideband calculations, GINGER for this study. For IFEL amplifiers in the frequency range of interest (200 to 600 GHz), we have devised a wiggler design strategy which incorporates a tapering algorithm that is suitable for free-electron laser (FEL) systems with moderate space-charge effects and that minimizes spontaneous noise growth at frequencies below the fundamental, while enhancing the growth of the signal at the fundamental. In addition, engineering design considerations of the waveguide wall loading and electron beam fill factor in the waveguide set limits on the waveguide dimensions, the wiggler magnet gap spacing, the wiggler period, and the minimum magnetic field strength in the tapered region of the wiggler. As an example, we shall describe an FEL amplifier designed to produce an average power of about 10 MW at a frequency of 280 GHz to be used for electron cyclotron resonance heating of tokamak fusion devices.

  15. Modeling of induction-linac based free-electron laser amplifiers

    NASA Astrophysics Data System (ADS)

    Jong, R. A.; Fawley, W. M.; Scharlemann, E. T.

    1988-12-01

    We describe the modeling of an induction-linac based free-electron laser (IFEL) amplifier for producing multimegawatt levels of microwave power. We have used the Lawrence Livermore National Laboratory (LLNL) free-electron laser simulation code, FRED, and the simulation code for sideband calculations, GINGER for this study. For IFEL amplifiers in the frequency range of interest (200 to 600 GHz), we have devised a wiggler design strategy which incorporates a tapering algorithm that is suitable for Free-Electron Laser (FEL) systems with moderate space-charge effects and that minimizes spontaneous noise growth at frequencies below the fundamental, while enhancing the growth of the signal at the fundamental. In addition, engineering design considerations of the waveguide wall loading and electron beam fill factor in the waveguide set limits on the waveguide dimensions, the wiggler magnet gap spacing, the wiggler period, and the minimum magnetic field strength in the tapered region of the wiggler. As an example, we shall describe an FEL amplifier designed to produce an average power of about 10 MW at a frequency of 280 GHz to be used for electron cyclotron resonance heating of tokamak fusion devices.

  16. Analytical bunch compression studies for a linac-based electron accelerator

    NASA Astrophysics Data System (ADS)

    Schreck, M.; Wesolowski, P.

    2015-10-01

    The current paper deals with analytical bunch compression studies for FLUTE whose results are compared to simulations. FLUTE is a linac-based electron accelerator with a design energy of approximately 40 MeV currently being constructed at the Karlsruhe Institute of Technology. One of the goals of FLUTE is to generate electron bunches with their length lying in the femtosecond regime. In the first phase this will be accomplished using a magnetic bunch compressor. This compressor forms the subject of the studies presented. The paper is divided into two parts. The first part deals with pure geometric investigations of the bunch compressor where space charge effects and the backreaction of bunches with coherent synchrotron radiation are neglected. The second part is dedicated to the treatment of space charge effects. The upshot is that the analytical results in the two parts agree quite well with what is obtained from simulations. This paper shall form the basis for future analytical studies of the FLUTE bunch compressor and of bunch compression, in general.

  17. A tunable, linac based, intense, broad-band THz source forpump-probe experiments

    SciTech Connect

    Schmerge, J.; Adolphsen, C.; Corbett, J.; Dolgashev, V.; Durr, H.; Fazio, M.; Fisher, A.; Frisch, J.; Gaffney, K.; Guehr, M.; Hastings, J.; Hettel, B.; Hoffmann, M.; Hogan, M.; Holtkamp, N.; Huang, X.; Huang, Z.; Kirchmann, P.; LaRue, J.; Limborg, C.; Lindenberg, A.; Loos, H.; Maxwell, T.; Nilsson, A.; Raubenheimer, T.; Reis, D.; Ross, M.; Shen, Z. -X.; Stupakov, G.; Tantawi, S.; Tian, K.; Wu, Z.; Xiang, D.; Yakimenko, V.

    2015-02-02

    We propose an intense THz source with tunable frequency and bandwidth that can directly interact with the degrees of freedom that determine the properties of materials and thus provides a new tool for controlling and directing these ultrafast processes as well as aiding synthesis of new materials with new functional properties. This THz source will broadly impact our understanding of dynamical processes in matter at the atomic-scale and in real time. Established optical pumping schemes using femtosecond visible frequency laser pulses for excitation are extended into the THz frequency regime thereby enabling resonant excitation of bonds in correlated solid state materials (phonon pumping), to drive low energy electronic excitations, to trigger surface chemistry reactions, and to all-optically bias a material with ultrashort electric fields or magnetic fields. A linac-based THz source can supply stand-alone experiments with peak intensities two orders of magnitude stronger than existing laser-based sources, but when coupled with atomic-scale sensitive femtosecond x-ray probes it opens a new frontier in ultrafast science with broad applications to correlated materials, interfacial and liquid phase chemistry, and materials in extreme conditions.

  18. Investigation of Positron Moderator Materials for Electron-Linac-Based Slow Positron Beamlines

    NASA Astrophysics Data System (ADS)

    Suzuki, Ryoichi; Ohdaira, Toshiyuki; Uedono, Akira; Cho, Yang; Yoshida, Sadafumi; Ishida, Yuuki; Ohshima, Takeshi; Itoh, Hisayoshi; Chiwaki, Mitsukuni; Mikado, Tomohisa; Yamazaki, Tetsuo; Tanigawa, Shoichiro

    1998-08-01

    Positron re-emission properties were studied on moderator materials in order to improve the positron moderation system of electron-linac-based intense slow positron beamlines. The re-emitted positron fraction was measured on tungsten, SiC, GaN, SrTiO3, and hydrogen-terminated Si with a variable-energy pulsed positron beam. The results suggested that tungsten is the best material for the primary moderator of the positron beamlines while epitaxially grown n-type 6H SiC is the best material for the secondary moderator. Defect characterization by monoenergetic positron beams and surface characterization by Auger electron spectroscopy were carried out to clarify the mechanism of tungsten moderator degradation induced by high-energy electron irradiation. The characterization experiments revealed that the degradation is due to both radiation-induced vacancy clusters and surface carbon impurities. For the restoration of degraded tungsten moderators, oxygen treatment at ˜900°C is effective. Furthermore, it was found that oxygen at the tungsten surface inhibits positronium formation; as a result, it can increase the positron re-emission fraction.

  19. The clinical outcome of intracranial hemangioblastomas treated with linac-based stereotactic radiosurgery and radiotherapy

    PubMed Central

    Puataweepong, Putipun; Dhanachai, Mantana; Hansasuta, Ake; Dangprasert, Somjai; Sitathanee, Chomporn; Puddhikarant, Parmon; Jiarpinitnun, Chuleeporn; Ruangkanchanasetr, Rawee; Dechsupa, Patchareporn; Pairat, Kumutinee

    2014-01-01

    Recent publications have reported stereotactic radiosurgery as an effective and safe treatment for intracranial hemangioblastomas. However, because of the low incidence of these particular tumors, reports on large patient number studies have not yet been available. The objective of this study was to analyze the clinical results of 14 patients with 56 intracranial hemangioblastomas treated with linear accelerator (linac)-based stereotactic radiosurgery (SRS) and radiotherapy (SRT) in the same institute. The median age of patients was 41 years (range, 28–73 years). Nine of the patients (64%) had von Hippel-Lindau disease. A total of 39 lesions (70%) were treated with CyberKnife (CK), and 17 lesions (30%) were treated with X-Knife. The median pretreatment volume was 0.26 cm3 (range, 0.026–20.4 cm3). The median marginal dose was 20 Gy (range, 10–32 Gy) in 1 fraction (range, 1–10 fractions). The median follow-up time was 24 months (range, 11–89 months). At the last follow-up, 47 tumors (84%) were stable, 7 (13%) decreased and 2 (4%) increased. The 1-, 2- and 6-year local control rates were 98%, 88% and 73%, respectively. No radiation complications were observed in this study. There was a trend toward local failure only in cystic tumors, but this trend was not found to be statistically significant. SRS/SRT achieved a high local control rate in intracranial hemangioblastomas without radiation-induced complications. PMID:24554558

  20. SU-E-T-53: A New Method for Characterizing the Stability of the Treatment Couch Isocentre

    SciTech Connect

    Gete, E; Lee, R; Wilson, B

    2015-06-15

    Purpose: In this work we propose a new method for characterizing the accuracy of a linear accelerator treatment couch’s isocentre. This is accomplished by a direct determination of the coordinates of the center of rotation as a function of rotation angle. Methods: A phantom consisting of five metallic BBs arranged in a plane was constructed. The phantom was positioned on the treatment couch such that the plane of the BBs was horizontal, while the central BB was aligned with the linac isocentre. With the gantry in the vertical position, the couch was rotated through its full range of rotation while EPID images were acquired every 10 degrees. For each rotation angle, the coordinates of the rotation center were calculated from the displacement of each of the four off-center BBs identified on a pair of EPID images taken between successive rotations. The accuracy of the couch isocentre was evaluated from the distribution of the rotation center coordinates. Our results were compared with film based star-shot measurements of the couch isocentre. Results: The measured couch center of rotation consisted of a cloud of points clustered around the linac isocentre within < 0.7 mm distance. The deviations of these points from the linac isocentre were in the range of 0.01 to 0.20 mm in the cross-plane direction, and 0.10 to 0.61 mm in the in-plane direction, with mean values of 0.09 mm and 0.32 mm. These results were consistent with the results obtained from the star-shot method. Conclusion: A new method for determining the location and accuracy of the couch center of rotation has been successfully implemented. This method gives explicit values of the location and the stability of the couch isocentre, and it can be extended to gantry and collimator rotations.

  1. A practical approach to prevent gantry-couch collision for linac-based radiosurgery.

    PubMed

    Hua, Chiaho; Chang, Jenghwa; Yenice, Kamil; Chan, Maria; Amols, Howard

    2004-07-01

    Gantry-couch collision is a serious concern for treatment planning of the linear accelerator (linac) based stereotactic radiosurgery (SRS). The ability to detect collision at the time of planning eliminates the need for backup plans and preserves the useful beam angles that would be deemed unsafe and discarded otherwise. Most collision-detection schemes embedded in commercial planning software guard only against the most apparent collisions. On the other hand, a fool-proof collision-map or lookup table often requires detailed measurement of machine geometry and complex graphic operations. In this study, we have developed a simple analytical method for collision detection with the use of quick machine-specific measurements. The collision detection is mathematically solved by determining whether two facets in three-dimensional space, representing gantry and couch surfaces, intersect with each other. A computer code was implemented and tested on a Varian Clinac 600C linac equipped with a BrainLab micromultileaf collimator (MLC) device. To measure machine-specific parameters, the lesion isocenter was set to the origin of the stereotactic coordinate system. The reference coordinates of couch bracket corners and micro-MLC to the linac isocenter were measured only once in the treatment room before they were incorporated into the computer program. Couch, gantry, and collimator were subsequently translated and rotated to study the clearance of various beam arrangements and lesion locations. Predicted results were verified at the machine. Our method correctly confirmed clearance for a retrospective study of 54 previously treated SRS plans (76 isocenters). It also accurately predicted the collisions for all ten artificially created cases. In conclusion, we have developed an analytical method for SRS collision detection that is accurate, easy to implement, and computationally inexpensive.

  2. Pediatric cerebral arteriovenous malformations: The role of stereotactic linac-based radiosurgery

    SciTech Connect

    Zabel-du Bois, Angelika . E-mail: A.Zabel@dkfz-heidelberg.de; Milker-Zabel, Stefanie; Huber, Peter; Schlegel, Wolfgang; Debus, Juergen

    2006-07-15

    Purpose: To evaluate retrospectively clinical outcome and obliteration rates after linac-based radiosurgery (RS) in children with cerebral arteriovenous malformations (AVM). Methods and Materials: Between 1996 and 2002, 22 children with cerebral AVM were treated at our institution. Mean age at treatment was 11.8 years (range, 4.4-16.4 years). Classification according to Spetzler-Martin was 1 child grade I (4%), 7 grade II (32%), 12 grade III (56%), 1 grade IV (4%), and 1 grade V (4%). Median single dose was 18 Gy/80%-isodose. Median AVM volume was 4.2 mL (range, 0.4-26.5 mL). Median RS-based AVM-score was 1.07 (range, 0.61-3.55). Fifty-nine percent of children experienced intracranial hemorrhage before RS. Median follow-up was 3.1 years (range, 1.7-7.3 years). Results: Actuarial complete obliteration rate (CO) was 54% after 3 years and 65% after 4 years, respectively. Median time interval to CO was 27.1 months. Intracranial hemorrhage after RS was seen in five children after median 13.9 months. Annual bleeding risk was 9.1% after 1 year and 13.6% after 2 years. Maximum diameter {>=}3 cm and AVM-volume {>=}6 mL were significant predictors for intracranial hemorrhage. Neurologic deficits were improved/completely dissolved in 58% of children and remained stable in 42%. No new onset of neurologic dysfunction was seen after RS. Conclusions: RS is safe and effective in pediatric cerebral AVM with high obliteration rates. Size and volume of AVM are significant predictors for intracranial bleeding. The same treatment guidelines as in adults should be applied. Careful long-term follow-up observation is required after RS from long life expectation.

  3. Project for the development of the linac based NCT facility in University of Tsukuba.

    PubMed

    Kumada, H; Matsumura, A; Sakurai, H; Sakae, T; Yoshioka, M; Kobayashi, H; Matsumoto, H; Kiyanagi, Y; Shibata, T; Nakashima, H

    2014-06-01

    A project team headed by University of Tsukuba launched the development of a new accelerator based BNCT facility. In the project, we have adopted Radio-Frequency Quadrupole (RFQ)+Drift Tube Linac (DTL) type linac as proton accelerators. Proton energy generated from the linac was set to 8MeV and average current was 10mA. The linac tube has been constructed by Mitsubishi Heavy Industry Co. For neutron generator device, beryllium is selected as neutron target material; high intensity neutrons are generated by the reaction with beryllium and the 80kW proton beam. Our team chose beryllium as the neutron target material. At present beryllium target system is being designed with Monte-Carlo estimations and heat analysis with ANSYS. The neutron generator consists of moderator, collimator and shielding. It is being designed together with the beryllium target system. We also acquired a building in Tokai village; the building has been renovated for use as BNCT treatment facility. It is noteworthy that the linac tube had been installed in the facility in September 2012. In BNCT procedure, several medical devices are required for BNCT treatment such as treatment planning system, patient positioning device and radiation monitors. Thus these are being developed together with the linac based neutron source. For treatment planning system, we are now developing a new multi-modal Monte-Carlo treatment planning system based on JCDS. The system allows us to perform dose estimation for BNCT as well as particle radiotherapy and X-ray therapy. And the patient positioning device can navigate a patient to irradiation position quickly and properly. Furthermore the device is able to monitor movement of the patient׳s position during irradiation.

  4. Image quality and dose distributions of three linac-based imaging modalities.

    PubMed

    Dzierma, Yvonne; Ames, Evemarie; Nuesken, Frank; Palm, Jan; Licht, Norbert; Rübe, Christian

    2015-04-01

    Linac-based patient imaging is possible with a variety of techniques using different photon energies. The purpose of this work is to compare three imaging systems operating at 6 MV, flattening free filter (FFF) 1 MV, and 121 kV. The dose distributions of all pretreatment set-up images (over 1,000) were retrospectively calculated on the planning computed tomography (CT) images for all patients with prostate and head-and-neck cancer treated at our institution in 2013. We analyzed the dose distribution and the dose to organs at risk. For head-and-neck cancer patients, the imaging dose from 6-MV cone beam CT (CBCT) reached maximum values at around 8 cGy. The 1-MV CBCT dose was about 63-79 % of the 6-MV CBCT dose for all organs at risk. Planar imaging reduced the imaging dose from CBCT to 30-40 % for both megavoltage modalities. The dose from the kilovoltage CBCT was 4-10 % of the 6-MV CBCT dose. For prostate cancer patients, the maximum dose from 6-MV CBCT reached 13-15 cGy, and was reduced to 66-73 % for 1 MV. Planar imaging reduces the MV CBCT dose to 10-20 %. The kV CBCT dose is 15-20 % of the 6-MV CBCT dose, slightly higher than the dose from MV axes. The dose distributions differ markedly in response to the different beam profiles and dose-depth characteristics.

  5. Compact Short-Pulsed Electron Linac Based Neutron Sources for Precise Nuclear Material Analysis

    NASA Astrophysics Data System (ADS)

    Uesaka, M.; Tagi, K.; Matsuyama, D.; Fujiwara, T.; Dobashi, K.; Yamamoto, M.; Harada, H.

    2015-10-01

    An X-band (11.424GHz) electron linac as a neutron source for nuclear data study for the melted fuel debris analysis and nuclear security in Fukushima is under development. Originally we developed the linac for Compton scattering X-ray source. Quantitative material analysis and forensics for nuclear security will start several years later after the safe settlement of the accident is established. For the purpose, we should now accumulate more precise nuclear data of U, Pu, etc., especially in epithermal (0.1-10 eV) neutrons. Therefore, we have decided to modify and install the linac in the core space of the experimental nuclear reactor "Yayoi" which is now under the decommission procedure. Due to the compactness of the X-band linac, an electron gun, accelerating tube and other components can be installed in a small space in the core. First we plan to perform the time-of-flight (TOF) transmission measurement for study of total cross sections of the nuclei for 0.1-10 eV energy neutrons. Therefore, if we adopt a TOF line of less than 10m, the o-pulse length of generated neutrons should be shorter than 100 ns. Electronenergy, o-pulse length, power, and neutron yield are ~30 MeV, 100 ns - 1 micros, ~0.4 kW, and ~1011 n/s (~103 n/cm2/s at samples), respectively. Optimization of the design of a neutron target (Ta, W, 238U), TOF line and neutron detector (Ce:LiCAF) of high sensitivity and fast response is underway. We are upgrading the electron gun and a buncher to realize higher current and beam power with a reasonable beam size in order to avoid damage of the neutron target. Although the neutron flux is limited in case of the X-band electron linac based source, we take advantage of its short pulse aspect and availability for nuclear data measurement with a short TOF system. First, we form a tentative configuration in the current experimental room for Compton scattering in 2014. Then, after the decommissioning has been finished, we move it to the "Yayoi" room and perform

  6. Neural stem cell sparing by linac based intensity modulated stereotactic radiotherapy in intracranial tumors.

    PubMed

    Oehler, Julia; Brachwitz, Tim; Wendt, Thomas G; Banz, Nico; Walther, Mario; Wiezorek, Tilo

    2013-07-24

    cortex benefit most from IMSRT (p  <  0.001). The feasibility of neural stem cell niches sparing with sophisticated linac based inverse IMSRT with 7 beamlets in an unselected cohort of intracranial tumors in relation to topographic situation has been demonstrated. Clinical relevance testing neurotoxicity remains to be demonstrated.

  7. Neural stem cell sparing by linac based intensity modulated stereotactic radiotherapy in intracranial tumors

    PubMed Central

    2013-01-01

    subventricular zone nor the cortex benefit most from IMSRT (p < 0.001). Conclusion The feasibility of neural stem cell niches sparing with sophisticated linac based inverse IMSRT with 7 beamlets in an unselected cohort of intracranial tumors in relation to topographic situation has been demonstrated. Clinical relevance testing neurotoxicity remains to be demonstrated. PMID:23883368

  8. Investigation of the accuracy of MV radiation isocentre calculations in the Elekta cone-beam CT software XVI.

    PubMed

    Riis, Hans L; Moltke, Lars N; Zimmermann, Sune J; Ebert, Martin A; Rowshanfarzad, Pejman

    2016-06-07

    Accurate determination of the megavoltage (MV) radiation isocentre of a linear accelerator (linac) is an important task in radiotherapy. The localization of the MV radiation isocentre is crucial for correct calibration of the in-room lasers and the cone-beam CT scanner used for patient positioning prior to treatment. Linac manufacturers offer tools for MV radiation isocentre localization. As a user, there is no access to the documentation for the underlying method and calculation algorithm used in the commercial software. The idea of this work was to evaluate the accuracy of the software tool for MV radiation isocentre calculation as delivered by Elekta using independent software. The image acquisition was based on the scheme designed by the manufacturer. Eight MV images were acquired in each series of a ball-bearing (BB) phantom attached to the treatment couch. The images were recorded at cardinal angles of the gantry using the electronic portal imaging device (EPID). Eight Elekta linacs with three different types of multileaf collimators (MLCs) were included in the test. The influence of MLC orientation, x-ray energy, and phantom modifications were examined. The acquired images were analysed using the Elekta x-ray volume imaging (XVI) software and in-house developed (IHD) MATLAB code. Results from the two different software were compared. A discrepancy in the longitudinal direction of the isocentre localization was found averaging 0.23 mm up to a maximum of 0.75 mm. The MLC orientation or the phantom asymmetry in the longitudinal direction do not appear to cause the discrepancy. The main cause of the differences could not be clearly identified. However, it is our opinion that the commercial software delivered by the linac manufacturer should be improved to reach better stability and precise results in the MV radiation isocentre calculations.

  9. Investigation of the accuracy of MV radiation isocentre calculations in the Elekta cone-beam CT software XVI

    NASA Astrophysics Data System (ADS)

    Riis, Hans L.; Moltke, Lars N.; Zimmermann, Sune J.; Ebert, Martin A.; Rowshanfarzad, Pejman

    2016-06-01

    Accurate determination of the megavoltage (MV) radiation isocentre of a linear accelerator (linac) is an important task in radiotherapy. The localization of the MV radiation isocentre is crucial for correct calibration of the in-room lasers and the cone-beam CT scanner used for patient positioning prior to treatment. Linac manufacturers offer tools for MV radiation isocentre localization. As a user, there is no access to the documentation for the underlying method and calculation algorithm used in the commercial software. The idea of this work was to evaluate the accuracy of the software tool for MV radiation isocentre calculation as delivered by Elekta using independent software. The image acquisition was based on the scheme designed by the manufacturer. Eight MV images were acquired in each series of a ball-bearing (BB) phantom attached to the treatment couch. The images were recorded at cardinal angles of the gantry using the electronic portal imaging device (EPID). Eight Elekta linacs with three different types of multileaf collimators (MLCs) were included in the test. The influence of MLC orientation, x-ray energy, and phantom modifications were examined. The acquired images were analysed using the Elekta x-ray volume imaging (XVI) software and in-house developed (IHD) MATLAB code. Results from the two different software were compared. A discrepancy in the longitudinal direction of the isocentre localization was found averaging 0.23 mm up to a maximum of 0.75 mm. The MLC orientation or the phantom asymmetry in the longitudinal direction do not appear to cause the discrepancy. The main cause of the differences could not be clearly identified. However, it is our opinion that the commercial software delivered by the linac manufacturer should be improved to reach better stability and precise results in the MV radiation isocentre calculations.

  10. Dosimetric analysis of isocentrically shielded volumetric modulated arc therapy for locally recurrent nasopharyngeal cancer

    PubMed Central

    Lu, Jia-Yang; Huang, Bao-Tian; Xing, Lei; Chang, Daniel T.; Peng, Xun; Xie, Liang-Xi; Lin, Zhi-Xiong; Li, Mei

    2016-01-01

    This study aimed to investigate the dosimetric characteristics of an isocentrically shielded RapidArc (IS-RA) technique for treatment of locally recurrent nasopharyngeal cancer (lrNPC). In IS-RA, the isocenter was placed at the center of the pre-irradiated brainstem (BS)/spinal cord (SC) and the jaws were set to shield the BS/SC while ensuring the target coverage during the whole gantry rotation. For fifteen patients, the IS-RA plans were compared with the conventional RapidArc (C-RA) regarding target coverage, organ-at-risk (OAR) sparing and monitor units (MUs). The relationship between the dose reduction of BS/SC and some geometric parameters including the angle extended by the target with respect to the axis of BS/SC (Ang_BSSC), the minimum distance between the target and BS/SC (Dist_Min) and the target volume were evaluated. The IS-RA reduced the BS/SC doses by approximately 1–4 Gy on average over the C-RA, with more MUs. The IS-RA demonstrated similar target coverage and sparing of other OARs except for slightly improved sparing of optic structures. More dose reduction in the isocentric region was observed in the cases with larger Ang_BSSC or smaller Dist_Min. Our results indicated that the IS-RA significantly improves the sparing of BS/SC without compromising dosimetric requirements of other involved structures for lrNPC. PMID:27173670

  11. Fast Monte Carlo Electron-Photon Transport Method and Application in Accurate Radiotherapy

    NASA Astrophysics Data System (ADS)

    Hao, Lijuan; Sun, Guangyao; Zheng, Huaqing; Song, Jing; Chen, Zhenping; Li, Gui

    2014-06-01

    Monte Carlo (MC) method is the most accurate computational method for dose calculation, but its wide application on clinical accurate radiotherapy is hindered due to its poor speed of converging and long computation time. In the MC dose calculation research, the main task is to speed up computation while high precision is maintained. The purpose of this paper is to enhance the calculation speed of MC method for electron-photon transport with high precision and ultimately to reduce the accurate radiotherapy dose calculation time based on normal computer to the level of several hours, which meets the requirement of clinical dose verification. Based on the existing Super Monte Carlo Simulation Program (SuperMC), developed by FDS Team, a fast MC method for electron-photon coupled transport was presented with focus on two aspects: firstly, through simplifying and optimizing the physical model of the electron-photon transport, the calculation speed was increased with slightly reduction of calculation accuracy; secondly, using a variety of MC calculation acceleration methods, for example, taking use of obtained information in previous calculations to avoid repeat simulation of particles with identical history; applying proper variance reduction techniques to accelerate MC method convergence rate, etc. The fast MC method was tested by a lot of simple physical models and clinical cases included nasopharyngeal carcinoma, peripheral lung tumor, cervical carcinoma, etc. The result shows that the fast MC method for electron-photon transport was fast enough to meet the requirement of clinical accurate radiotherapy dose verification. Later, the method will be applied to the Accurate/Advanced Radiation Therapy System ARTS as a MC dose verification module.

  12. An experimental study of correlations in the development of the electron-photon cascades

    NASA Technical Reports Server (NTRS)

    Kratenko, Y. P.; Caharishnikov, S. A.

    1985-01-01

    In terms of the experimental data on the development of the electron photon cascades (EPC) in Pb from electrons and photons of cosmic rays in the tens GeV energy region a calculation of correlations between the characteristics of longitudinal and lateral development of the EPC as well as those between fluctuations of the cascade particle numbers at different stages of the cascade development was carried out. The results obtained are compared to the numerical EPC calculations.

  13. Single Fraction Versus Fractionated Linac-Based Stereotactic Radiotherapy for Vestibular Schwannoma: A Single-Institution Experience

    SciTech Connect

    Collen, Christine; Ampe, Ben; Gevaert, Thierry; Moens, Maarten; Linthout, Nadine; De Ridder, Mark; Verellen, Dirk; D'Haens, Jean; Storme, Guy

    2011-11-15

    Purpose: To evaluate and compare outcomes for patients with vestibular schwannoma (VS) treated in a single institution with linac-based stereotactic radiosurgery (SRS) or by fractionated stereotactic radiotherapy (SRT). Methods and Materials: One hundred and nineteen patients (SRS = 78, SRT = 41) were treated. For both SRS and SRT, beam shaping is performed by a mini-multileaf collimator. For SRS, a median single dose of 12.5 Gy (range, 11-14 Gy), prescribed to the 80% isodose line encompassing the target, was applied. Of the 42 SRT treatments, 32 treatments consisted of 10 fractions of 3-4 Gy, and 10 patients received 25 sessions of 2 Gy, prescribed to the 100% with the 95% isodose line encompassing the planning target volume. Mean largest tumor diameter was 16.6 mm in the SRS and 24.6 mm in the SRT group. Local tumor control, cranial nerve toxicity, and preservation of useful hearing were recorded. Any new treatment-induced cranial nerve neuropathy was scored as a complication. Results: Median follow-up was 62 months (range, 6-136 months), 5 patients progressed, resulting in an overall 5-year local tumor control of 95%. The overall 5-year facial nerve preservation probability was 88% and facial nerve neuropathy was statistically significantly higher after SRS, after prior surgery, for larger tumors, and in Koos Grade {>=}3. The overall 5-year trigeminal nerve preservation probability was 96%, not significantly influenced by any of the risk factors. The overall 4-year probability of preservation of useful hearing (Gardner-Robertson score 1 or 2) was 68%, not significantly different between SRS or SRT (59% vs. 82%, p = 0.089, log rank). Conclusion: Linac-based RT results in good local control and acceptable clinical outcome in small to medium-sized vestibular schwannomas (VSs). Radiosurgery for large VSs (Koos Grade {>=}3) remains a challenge because of increased facial nerve neuropathy.

  14. Investigating a multi-purpose target for electron linac based photoneutron sources for BNCT of deep-seated tumors

    NASA Astrophysics Data System (ADS)

    Masoudi, S. Farhad; Rasouli, Fatemeh S.

    2015-08-01

    Recent studies in BNCT have focused on investigating appropriate neutron sources as alternatives for nuclear reactors. As the most prominent facilities, the electron linac based photoneutron sources benefit from two consecutive reactions, (e, γ) and (γ, n). The photoneutron sources designed so far are composed of bipartite targets which involve practical problems and are far from the objective of achieving an optimized neutron source. This simulation study deals with designing a compact, optimized, and geometrically simple target for a photoneutron source based on an electron linac. Based on a set of MCNPX simulations, tungsten is found to have the potential of utilizing as both photon converter and photoneutron target. Besides, it is shown that an optimized dimension for such a target slows-down the produced neutrons toward the desired energy range while keeping them economy, which makes achieving the recommended criteria for BNCT of deep-tumors more available. This multi-purpose target does not involve complicated designing, and can be considered as a significant step toward finding application of photoneutron sources for in-hospital treatments. In order to shape the neutron beam emitted from such a target, the beam is planned to pass through an optimized arrangement of materials composed of moderators, filters, reflector, and collimator. By assessment with the recommended in-air parameters, it is shown that the designed beam provides high intensity of desired neutrons, as well as low background contamination. The last section of this study is devoted to investigate the performance of the resultant beam in deep tissue. A typical simulated liver tumor, located within a phantom of human body, was subjected to the irradiation of the designed spectrum. The dosimetric results, including evaluated depth-dose curves and carried out in-phantom parameters show that the proposed configuration establishes acceptable agreement between the appropriate neutron intensity, and

  15. Physical parameters of very small diameter 10 MV X-ray beams for linac-based stereotactic radiosurgery

    NASA Astrophysics Data System (ADS)

    Sham, Edwin

    Physical aspects of very small diameter X-ray beams used for a linac-based stereotactic radiosurgery are presented in this thesis. A 10 MV linac was used as the radiation source. Very small 10 MV photon fields with diameters of 1.5 mm, 3 mm, and 5 mm are produced by special collimators attached to the treatment head of the linac. The radiation beam data were measured with a small field diode detector as well as radiographic and radiochromic films. Measured beam parameters were compared with the same parameters calculated with Monte Carlo (MC) simulations. For very small photon fields with diameters on the order of the focal spot size, MC calculations show that both the percentage depth dose (PDD) distributions and dose profiles are sensitive to the focal spot size. A simple sliding slit technique was developed to measure the focal spot size and shape for accurate MC simulations of very small diameter beams. The measured focal spot of the 10 MV linac is elliptical in shape and fitted by a Gaussian distribution with full-widths-at-half-maximum (FWHMs) of 2.05 mm and 1.34 mm in the principal axes of the ellipse. A Gaussian circle equivalent in area to the experimentally determined focal spot ellipse was used in MC simulations. The resulting PDD and beam profile calculations are in good agreement with the measurements. Dynamic radiosurgery with very small diameter photon beams was carried out using the 10 MV linac. Radiosurgical isodose distributions were measured with radiographic films in a spherical head phantom and calculated with the MC technique. A good agreement between the measured and MC-calculated isodose distributions for very small diameter fields is achieved. The displacement of the center of the measured isodose distributions relative to the laser-defined isocenter was on the order of 0.7 mm. All these results show the potential of linac-based radiosurgery with very small diameter photon beams for clinical use.

  16. Isocentric rotational performance of the Elekta Precise Table studied using a USB-microscope.

    PubMed

    Riis, Hans L; Zimmermann, Sune J; Riis, Poul

    2010-12-21

    The isocentric three-dimensional performance of the Elekta Precise Table was investigated. A pointer was attached to the radiation head of the accelerator and positioned at the geometric rotational axis of the head. A USB-microscope was mounted on the treatment tabletop to measure the table position relative to the pointer tip. The table performance was mapped in terms of USB-microscope images of the pointer tip at different table angles and load configurations. The USB-microscope was used as a detector to measure the pointer tip positions with a resolution down to 0.01 mm. A new elastic model of the treatment table was developed. This model describes the performance of the treatment table quite well except from some deviations due to backlash effects. Geometric and elastic features are described through six parameters. These parameters are calculated using the linear least squares fitting technique. A new method to ensure optimal positioning of the table relative to the accelerator is presented. This method cannot eliminate systematic errors completely. To eliminate systematic errors we suggest that geometric and elastic models of the table and accelerator gantry arm are incorporated in the dose planning system.

  17. Isocentric rotational performance of the Elekta Precise Table studied using a USB-microscope

    NASA Astrophysics Data System (ADS)

    Riis, Hans L.; Zimmermann, Sune J.; Riis, Poul

    2010-12-01

    The isocentric three-dimensional performance of the Elekta Precise Table was investigated. A pointer was attached to the radiation head of the accelerator and positioned at the geometric rotational axis of the head. A USB-microscope was mounted on the treatment tabletop to measure the table position relative to the pointer tip. The table performance was mapped in terms of USB-microscope images of the pointer tip at different table angles and load configurations. The USB-microscope was used as a detector to measure the pointer tip positions with a resolution down to 0.01 mm. A new elastic model of the treatment table was developed. This model describes the performance of the treatment table quite well except from some deviations due to backlash effects. Geometric and elastic features are described through six parameters. These parameters are calculated using the linear least squares fitting technique. A new method to ensure optimal positioning of the table relative to the accelerator is presented. This method cannot eliminate systematic errors completely. To eliminate systematic errors we suggest that geometric and elastic models of the table and accelerator gantry arm are incorporated in the dose planning system.

  18. On achieving a clinically useful D-T neutron isocentric therapy system

    SciTech Connect

    Hilton, J.L.; Hendry, G.O.

    1981-04-01

    The Cyclotron Corporation's Model 4100 Neutron Cancer Therapy System with its output of 8 x 10/sup 12/ (14 MeV) neutron/sec designed for 500 hours is made up of: a factory recyclable miniature 200 kV sealed tube which radially accelerates up to 450 mA of deuterium and tritium ions from four duoplasmatron-type ion sources onto a central target; hand changeable radiation collimators; boronated hydrogenous shielding; isocentric gantry mounting; clinical diagnostics; and controls. The self-contained gas handling system which provides the needed differential gas pressure also stores, pumps, cleans, and recycles the D-T inventory. It is composed of a reversible getter high vacuum pump, a selective noble gas sputter ion pump, and a specialized uranium trap which, by controlled thermal decomposition of uranium hydride, regulates the ion source pressure. A D-T gas inventory of 3.7 k curies provides beam-on time of about three hours, while the gas recycle requires one to two hours. The four-sided target is made up from an array of heat transfer-optimized small copper tubes and their metal surface cladding which results in relatively high neutron output and long target life. The double vacuum walls, providing redundant tritium containment, are combined with other safety features.

  19. LEPS2: the second Laser-Electron Photon facility at SPring-8

    SciTech Connect

    Yosoi, M.

    2011-10-21

    A new project to construct the second beamline for the laser-electron photon beam at SPring-8 (LEPS2) has started. Based on the LEPS experience, the project aims to improve the intensity of the photon beam and to expand the detector acceptance by adopting the BNL-E949 detector, which is a hermetic detector in a large 1 T solenoid magnet. The central region of tracking chambers will be upgraded for the LEPS2. A new LEPS2 experimental building has just been constructed outside the experimental hall of the storage ring. The present status of the development of a frozen-spin polarized HD target is also reported.

  20. LEPS2 : the second Laser-Electron Photon facility at SPring-8

    NASA Astrophysics Data System (ADS)

    Yosoi, M.

    2011-10-01

    A new project to construct the second beamline for the laser-electron photon beam at SPring-8 (LEPS2) has started. Based on the LEPS experience, the project aims to improve the intensity of the photon beam and to expand the detector acceptance by adopting the BNL-E949 detector, which is a hermetic detector in a large 1 T solenoid magnet. The central region of tracking chambers will be upgraded for the LEPS2. A new LEPS2 experimental building has just been constructed outside the experimental hall of the storage ring. The present status of the development of a frozen-spin polarized HD target is also reported.

  1. Deflecting RF cavity design for a recirculating linac based facility for ultrafast X-ray science (LUX)

    SciTech Connect

    Li, Derun; Corlett, J.N.

    2003-05-01

    We report on superconducting deflecting RF cavity designs for a Recirculating Linac Based Facility for Ultrafast X-ray Science (LUX) at Lawrence Berkeley National Laboratory. The deflecting cavities operate in the lowest dipole mode and are required to produce a temporal correlation within flat electron bunches, as needed for x-ray compression in crystal optics. Deflecting voltage of up to 8.5-MV is required at 3.9-GHz. We present a 7-cell cavity design in this paper. Seven such cavities are required to generate the 8.5 MV deflecting voltage. Longitudinal and transverse impedance from LOM (lower order mode) and HOM (higher order mode) are simulated using the MAFIA code. Short-range and long-range wakefield excited through these impedances are calculated. Beam loading effects of the deflecting mode and LOM modes are estimated. Q values of the LOM monopole modes in the cavity may need to be damped to be below 10{sup 4}-10{sup 5} levels in order to maintain the required energy spread.

  2. A Single-Shot Method for Measuring Femtosecond Bunch Length in Linac-Based Free-Electron Lasers

    SciTech Connect

    Huang, Z.; Bane, K.; Ding, Y.; Emma, P.; /SLAC

    2010-08-26

    There is growing interest in the generation and characterization of femtosecond and subfemtosecond pulses from linac-based free-electron lasers (FELs). In this report, following the method of Ricci and Smith [Phys. Rev. ST Accel. Beams 3, 032801 (2000)], we investigate the measurement of the longitudinal bunch profile of an ultrashort electron bunch produced by these FELs. We show that this method can be applied in a straightforward manner at x-ray FEL facilities such as the Linac Coherent Light Source by slightly adjusting the second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final linac. We find that the linac wakefield strongly perturbs the measurement, and through analysis show that it can be compensated in a simple way. We demonstrate the effectiveness of this method and wakefield compensation through numerical simulations, including effects of coherent synchrotron radiation and longitudinal space charge. When used in conjunction with a high-resolution electron spectrometer, this method potentially reveals the temporal profile of the electron beam down to the femtosecond and subfemotsecond scale.

  3. Design of a 10 MeV normal conducting CW proton linac based on equidistant multi-gap CH cavities

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Hui

    2015-09-01

    Continuous wave (CW) high current proton linacs have wide applications as the front end of high power proton machines. The low energy part of such a linac is the most difficult and there is currently no widely accepted solution. Based on the analysis of the focusing properties of the CW low energy proton linac, a 10 MeV low energy normal conducting proton linac based on equidistant seven-gap Cross-bar H-type (CH) cavities is proposed. The linac is composed of ten 7-gap CH cavities and the transverse focusing is maintained by quadrupole doublets located between the cavities. The total length of the linac is less than 6 meters and the average acceleration gradient is about 1.2 MeV/m. The electromagnetic properties of the cavities are investigated by Microwave Studio. At the nominal acceleration gradient the maximum surface electric field in the cavities is less than 1.3 times the Kilpatrick limit, and the Ohmic loss of each cavity is less than 35 kW. Multi-particle beam dynamics simulations are performed with Tracewin code, and the results show that the beam dynamics of the linac are quite stable, the linac has the capability to accelerate up to 30 mA beam with acceptable dynamics behavior. Supported by National Natural Science Foundation of China (11375122, 91126003)

  4. An algorithm for Monte Carlo simulation of coupled electron-photon transport

    NASA Astrophysics Data System (ADS)

    Salvat, F.; Fernández-Varea, J. M.; Sempau, J.; Acosta, E.; Baró, J.

    1997-11-01

    An algorithm for Monte Carlo simulation of coupled electron-photon transport is described. Electron and positron tracks are generated by means of PENELOPE, a mixed procedure developed by Baró et al. [Nucl. Instr. and Meth. B 100 (1995) 31]. The simulation of photon transport follows the conventional, detailed method. Photons are assumed to interact via coherent and incoherent scattering, photoelectric absorption and electron-positron pair production. Photon interactions are simulated through analytical differential cross sections, derived from simple physical models and renormalized to reproduce accurate attenuation coefficients available from the literature. The combined algorithm has been implemented in a FORTRAN 77 computer code that generates electron-photon showers in arbitrary materials for the energy range from ˜1 GeV down to 1 keV or the binding energy of the L-shell of the heaviest element in the medium, whichever is the largest. The code is capable of following secondary particles that are generated within this energy range. The reliability of the algorithm and computer code is demonstrated by comparing simulation results with experimental data and with results from other Monte Carlo codes.

  5. Coherent manipulation of thermal transport by tunable electron-photon and electron-phonon interaction

    NASA Astrophysics Data System (ADS)

    Paolucci, Federico; Timossi, Giuliano; Solinas, Paolo; Giazotto, Francesco

    2017-06-01

    We propose a system where coherent thermal transport between two reservoirs in non-galvanic contact is modulated by independently tuning the electron-photon and the electron-phonon coupling. The scheme is based on two gate-controlled electrodes capacitively coupled through a dc-SQUID (superconducting quantum interference device) as an intermediate phase-tunable resonator. Thereby the electron-photon interaction is modulated by controlling the flux threading the dc-SQUID (superconducting quantum interference device) and the impedance of the two reservoirs, while the electron-phonon coupling is tuned by controlling the charge carrier concentration in the electrodes. To quantitatively evaluate the behavior of the system, we propose to exploit the graphene reservoirs. In this case, the scheme can work at temperatures reaching 1 K, with unprecedented temperature modulations as large as 245 mK, transmittance up to 99%, and energy conversion efficiency up to 50%. Finally, the accuracy of heat transport control allows us to use this system as an experimental tool to determine the electron-phonon coupling in two-dimensional electronic systems.

  6. Program EPICP: Electron photon interaction code, photon test module. Version 94.2

    SciTech Connect

    Cullen, D.E.

    1994-09-01

    The computer code EPICP performs Monte Carlo photon transport calculations in a simple one zone cylindrical detector. Results include deposition within the detector, transmission, reflection and lateral leakage from the detector, as well as events and energy deposition as a function of the depth into the detector. EPICP is part of the EPIC (Electron Photon Interaction Code) system. EPICP is designed to perform both normal transport calculations and diagnostic calculations involving only photons, with the objective of developing optimum algorithms for later use in EPIC. The EPIC system includes other modules that are designed to develop optimum algorithms for later use in EPIC; this includes electron and positron transport (EPICE), neutron transport (EPICN), charged particle transport (EPICC), geometry (EPICG), source sampling (EPICS). This is a modular system that once optimized can be linked together to consider a wide variety of particles, geometries, sources, etc. By design EPICP only considers photon transport. In particular it does not consider electron transport so that later EPICP and EPICE can be used to quantitatively evaluate the importance of electron transport when starting from photon sources. In this report I will merely mention where we expect the results to significantly differ from those obtained considering only photon transport from that obtained using coupled electron-photon transport.

  7. ITS Version 6 : the integrated TIGER series of coupled electron/photon Monte Carlo transport codes.

    SciTech Connect

    Franke, Brian Claude; Kensek, Ronald Patrick; Laub, Thomas William

    2008-04-01

    ITS is a powerful and user-friendly software package permitting state-of-the-art Monte Carlo solution of lineartime-independent coupled electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. Our goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theorists alike with a method for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permits the more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 6, the latest version of ITS, contains (1) improvements to the ITS 5.0 codes, and (2) conversion to Fortran 90. The general user friendliness of the software has been enhanced through memory allocation to reduce the need for users to modify and recompile the code.

  8. On the robustness of VMAT-SABR treatment plans against isocentre positioning uncertainties.

    PubMed

    Stroom, Joep; Vieira, Sandra; Mateus, Dalila; Greco, Carlo; Fogliata, Antonella; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio; Cozzi, Luca

    2014-09-05

    To appraise the robustness of VMAT dose distributions against uncertainties in the positioning of the patients when single fraction SABRT treatments are planned. A set of 18 patients (8 lung, 5 brain, 5 spinal or para-spinal) treated with VMAT in a single fraction of 24Gy were retrospectively analyzed. All approved plans were re-calculated by applying shifts to the isocentre of ±0.5, ±1, ±1.5, ±2 and ±3 mm along the primary X, Y and Z axes. Dose calculations were performed with the AAA and the Acuros engines. Quantitative analysis of DVH was performed on a total of 36 references (18 patients with AAA, 18 with Acuros) and 1080 re-calculated plans to measure the potential degree of deterioration of the plans according to the simulated errors. The dose to the CTV was essentially not affected by the isocenter shifts in all cases. Concerning PTV, The main impact was observed on the near-to-minimum dose D99%. No relevant impact was observed on organs at risk in the case of lung patients. In the case of patients treated in the spinal or para-spinal region, the near-to-maximum dose to the spine showed, in the worst scenario, referring to Acuros calculation, a potential average increase of 0.3Gy with a maximum of 1.9Gy (from 10.3 to 12.2 Gy) or 18%. This was partially mitigated to 12% with 1 mm and to 5% with 0.5 mm shifts. The study showed that shifts in the position of the isocenter as large as 3 mm tend to have modest impacts on the quality of the VMAT plans, scored by means of conventional DVH parameters. From the data shown, the VMAT approach should be considered adequately robust for single fraction SABR.

  9. Poster — Thur Eve — 55: An automated XML technique for isocentre verification on the Varian TrueBeam

    SciTech Connect

    Asiev, Krum; Mullins, Joel; DeBlois, François; Liang, Liheng; Syme, Alasdair

    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. A 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.

  10. Non isocentric film-based intracavitary brachytherapy planning in cervical cancer: a retrospective dosimetric analysis with CT planning.

    PubMed

    Tyagi, Kirti; Mukundan, Hari; Mukherjee, Deboleena; Semwal, Manoj; Sarin, Arti

    2012-09-01

    To compare intracavitary brachytherapy dose estimation for organs at risk (bladder and rectum) based on semi-orthogonal reconstruction of radiographs on non-isocentric X-ray unit and Computed Tomography (CT) - based volumetric planning in cervical cancer. Bladder and rectal points as per International Commission on Radiation Units and Measurements (ICRU) report 38, were retrospectively evaluated on 15 high dose rate intracavitary brachytherapy applications for cervical cancer cases. With the same source configuration as obtained during planning on radiographs performed on a non-isocentric X-ray unit, the mean doses to 2cc of most irradiated part of bladder and rectum were computed by CT planning and these estimates were compared with the doses at ICRU bladder and rectal points. The mean ICRU point dose for bladder was 3.08 Gy (1.9-5.9 Gy) and mean dose to 2 cc (D2cc) bladder was 6.91 Gy (2.9-12.2 Gy). ICRU rectal dose was 3.8 Gy (2.4-4.45 Gy) and was comparable with D2cc rectum dose 4.2 Gy (2.8-5.9 Gy). Comparison of mean total dose (ICRU point vs. D2cc) for each patient was found to be significantly different for bladder (p = 0.000), but not for rectum (p = 0.08). On comparison of ICRU point based planning with volumetric planning on CT, it was found that bladder doses were underestimated by the film based method. However, the rectal doses were found to be similar to the D2cc doses. The results with non isocentric film based treatment planning were similar to the existing literature on orthogonal film based simulator planning.

  11. Real-time in vivo rectal wall dosimetry using MOSkin detectors during linac based stereotactic radiotherapy with rectal displacement.

    PubMed

    Legge, Kimberley; Greer, Peter B; O'Connor, Daryl J; Wilton, Lee; Richardson, Matthew; Hunter, Perry; Wilfert, Alex; Martin, Jarad; Rosenfeld, Anatoly; Cutajar, Dean

    2017-02-27

    MOSFET dosimetry is a method that has been used to measure in-vivo doses during brachytherapy treatments and during linac based radiotherapy treatment. Rectal displacement devices (RDDs) allow for safe dose escalation for prostate cancer treatment. This study used dual MOSkin detectors to assess real-time in vivo rectal wall dose in patients with an RDD in place during a high dose prostate stereotactic body radiation therapy (SBRT) boost trial. The PROMETHEUS study commenced in 2014 and provides a prostate SBRT boost dose with a RDD in place. Twelve patients received two boost fractions of 9.5-10 Gy each delivered to the prostate with a dual arc volumetric modulated arc therapy (VMAT) technique. Two MOSkins in a face-to-face arrangement (dual MOSkin) were used to decrease angular dependence. A dual MOSkin was attached to the anterior surface of the Rectafix and read out at 1 Hz during each treatment. The planned dose at each measurement point was exported from the planning system and compared with the measured dose. The root mean square error normalised to the total planned dose was calculated for each measurement point and treatment arc for the entire course of treatment. The average difference between the measured and planned doses over the whole course of treatment for all arcs measured was 9.7% with a standard deviation of 3.6%. The cumulative MOSkin reading was lower than the total planned dose for 64% of the arcs measured. The average difference between the final measured and final planned doses for all arcs measured was 3.4% of the final planned dose, with a standard deviation of 10.3%. MOSkin detectors were an effective tool for measuring dose delivered to the anterior rectal wall in real time during prostate SBRT boost treatments for the purpose of both ensuring the rectal doses remain within acceptable limits during the treatment and for the verification of final rectal doses.

  12. Space applications of the MITS electron-photon Monte Carlo transport code system

    SciTech Connect

    Kensek, R.P.; Lorence, L.J.; Halbleib, J.A.; Morel, J.E.

    1996-07-01

    The MITS multigroup/continuous-energy electron-photon Monte Carlo transport code system has matured to the point that it is capable of addressing more realistic three-dimensional adjoint applications. It is first employed to efficiently predict point doses as a function of source energy for simple three-dimensional experimental geometries exposed to simulated uniform isotropic planar sources of monoenergetic electrons up to 4.0 MeV. Results are in very good agreement with experimental data. It is then used to efficiently simulate dose to a detector in a subsystem of a GPS satellite due to its natural electron environment, employing a relatively complex model of the satellite. The capability for survivability analysis of space systems is demonstrated, and results are obtained with and without variance reduction.

  13. Photonic analog-to-digital conversion with electronic-photonic integrated circuits

    NASA Astrophysics Data System (ADS)

    Kärtner, F. X.; Amatya, R.; Araghchini, M.; Birge, J.; Byun, H.; Chen, J.; Dahlem, M.; DiLello, N. A.; Gan, F.; Holzwarth, C. W.; Hoyt, J. L.; Ippen, E. P.; Khilo, A.; Kim, J.; Kim, M.; Motamedi, A.; Orcutt, J. S.; Park, M.; Perrott, M.; Popović, M. A.; Ram, R. J.; Smith, H. I.; Zhou, G. R.; Spector, S. J.; Lyszczarz, T. M.; Geis, M. W.; Lennon, D. M.; Yoon, J. U.; Grein, M. E.; Schulein, R. T.

    2008-02-01

    Photonic Analog-to-Digital Conversion (ADC) has a long history. The premise is that the superior noise performance of femtosecond lasers working at optical frequencies enables us to overcome the bottleneck set by jitter and bandwidth of electronic systems and components. We discuss and demonstrate strategies and devices that enable the implementation of photonic ADC systems with emerging electronic-photonic integrated circuits based on silicon photonics. Devices include 2-GHz repetition rate low noise femtosecond fiber lasers, Si-Modulators with up to 20 GHz modulation speed, 20 channel SiN-filter banks, and Ge-photodetectors. Results towards a 40GSa/sec sampling system with 8bits resolution are presented.

  14. Integrated TIGER Series of Coupled Electron/Photon Monte Carlo Transport Codes System.

    SciTech Connect

    VALDEZ, GREG D.

    2012-11-30

    Version: 00 Distribution is restricted to US Government Agencies and Their Contractors Only. The Integrated Tiger Series (ITS) is a powerful and user-friendly software package permitting state-of-the-art Monte Carlo solution of linear time-independent coupled electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. The goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theorists alike with a method for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permits the more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 6, the latest version of ITS, contains (1) improvements to the ITS 5.0 codes, and (2) conversion to Fortran 95. The general user friendliness of the software has been enhanced through memory allocation to reduce the need for users to modify and recompile the code.

  15. Multi-isocentric 4π volumetric-modulated arc therapy approach for head and neck cancer.

    PubMed

    Subramanian, Vallinayagam Shanmuga; Subramani, Vellaiyan; Chilukuri, Srinivas; Kathirvel, Murugesan; Arun, Gandhi; Swamy, Shanmugam Thirumalai; Subramanian, Kala; Fogliata, Antonella; Cozzi, Luca

    2017-09-01

    To explore the feasibility of multi-isocentric 4π volumetric-modulated arc therapy (MI4π-VMAT) for the complex targets of head and neck cancers. Twenty-five previously treated patients of HNC underwent re-planning to improve the dose distributions with either coplanar VMAT technique (CP-VMAT) or noncoplanar MI4π-VMAT plans. The latter, involving 3-6 noncoplanar arcs and 2-3 isocenters were re-optimized using the same priorities and objectives. Dosimetric comparison on standard metrics from dose-volume histograms was performed to appraise relative merits of the two techniques. Pretreatment quality assurance was performed with IMRT phantoms to assess deliverability and accuracy of the MI4π-VMAT plans. The gamma agreement index (GAI) analysis with criteria of 3 mm distance to agreement (DTA) and 3% dose difference (DD) was applied. CP-VMAT and MI4π-VMAT plans achieved the same degree of coverage for all target volumes related to near-to-minimum and near-to-maximum doses. MI4π-VΜΑΤ plans resulted in an improved sparing of organs at risk. The average mean dose reduction to the parotids, larynx, oral cavity, and pharyngeal muscles were 3 Gy, 4 Gy, 5 Gy, and 4.3 Gy, respectively. The average maximum dose reduction to the brain stem, spinal cord, and oral cavity was 6.0 Gy, 3.8 Gy, and 2.4 Gy. Pretreatment QA results showed that plans can be reliably delivered with mean gamma agreement index of 97.0 ± 1.1%. MI4π-VMAT plans allowed to decrease the dose-volume-metrics for relevant OAR and results are reliable from a dosimetric standpoint. Early clinical experience has begun and future studies will report treatment outcome. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

  16. Measurement of cone beam CT coincidence with megavoltage isocentre and image sharpness using the QUASAR™ Penta-Guide phantom

    NASA Astrophysics Data System (ADS)

    Sykes, J. R.; Lindsay, R.; Dean, C. J.; Brettle, D. S.; Magee, D. R.; Thwaites, D. I.

    2008-10-01

    For image-guided radiotherapy (IGRT) systems based on cone beam CT (CBCT) integrated into a linear accelerator, the reproducible alignment of imager to x-ray source is critical to the registration of both the x-ray-volumetric image with the megavoltage (MV) beam isocentre and image sharpness. An enhanced method of determining the CBCT to MV isocentre alignment using the QUASAR™ Penta-Guide phantom was developed which improved both precision and accuracy. This was benchmarked against our existing method which used software and a ball-bearing (BB) phantom provided by Elekta. Additionally, a method of measuring an image sharpness metric (MTF50) from the edge response function of a spherical air cavity within the Penta-Guide phantom was developed and its sensitivity was tested by simulating misalignments of the kV imager. Reproducibility testing of the enhanced Penta-Guide method demonstrated a systematic error of <0.2 mm when compared to the BB method with near equivalent random error (s = 0.15 mm). The mean MTF50 for five measurements was 0.278 ± 0.004 lp mm-1 with no applied misalignment. Simulated misalignments exhibited a clear peak in the MTF50 enabling misalignments greater than 0.4 mm to be detected. The Penta-Guide phantom can be used to precisely measure CBCT MV coincidence and image sharpness on CBCT-IGRT systems.

  17. Measurement of cone beam CT coincidence with megavoltage isocentre and image sharpness using the QUASAR Penta-Guide phantom.

    PubMed

    Sykes, J R; Lindsay, R; Dean, C J; Brettle, D S; Magee, D R; Thwaites, D I

    2008-10-07

    For image-guided radiotherapy (IGRT) systems based on cone beam CT (CBCT) integrated into a linear accelerator, the reproducible alignment of imager to x-ray source is critical to the registration of both the x-ray-volumetric image with the megavoltage (MV) beam isocentre and image sharpness. An enhanced method of determining the CBCT to MV isocentre alignment using the QUASAR Penta-Guide phantom was developed which improved both precision and accuracy. This was benchmarked against our existing method which used software and a ball-bearing (BB) phantom provided by Elekta. Additionally, a method of measuring an image sharpness metric (MTF(50)) from the edge response function of a spherical air cavity within the Penta-Guide phantom was developed and its sensitivity was tested by simulating misalignments of the kV imager. Reproducibility testing of the enhanced Penta-Guide method demonstrated a systematic error of <0.2 mm when compared to the BB method with near equivalent random error (s=0.15 mm). The mean MTF(50) for five measurements was 0.278+/-0.004 lp mm(-1) with no applied misalignment. Simulated misalignments exhibited a clear peak in the MTF(50) enabling misalignments greater than 0.4 mm to be detected. The Penta-Guide phantom can be used to precisely measure CBCT-MV coincidence and image sharpness on CBCT-IGRT systems.

  18. Extension of the Integrated Tiger Series (ITS) of electron-photon Monte Carlo codes to 100 GeV

    SciTech Connect

    Miller, S.G.

    1988-08-01

    Version 2.1 of the Integrated Tiger Series (ITS) of electron-photon Monte Carlo codes was modified to extend their ability to model interactions up to 100 GeV. Benchmarks against experimental results conducted at 10 and 15 GeV confirm the accuracy of the extended codes. 12 refs., 2 figs., 2 tabs.

  19. Evaluation of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) for cerebral cavernous malformations: a 15-year single-center experience.

    PubMed

    Sager, Omer; Beyzadeoglu, Murat; Dincoglan, Ferrat; Uysal, Bora; Gamsiz, Hakan; Demiral, Selcuk; Oysul, Kaan; Dirican, Bahar; Sirin, Sait

    2014-01-01

    Surgery is the principal treatment for safely accessible hemorrhagic and symptomatic cavernous malformations. Nevertheless, the role of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) in the management of high-risk, symptomatic cavernoma lesions warrants further refinement. In this study, we evaluate the use of LINAC-based SRS for cerebral cavernous malformations (CMs) and report our 15-year single-center experience. A retrospective study from the Department of Radiation Oncology and the Department of Neurosurgery at Gulhane Military Medical Academy and Medical Faculty, Ankara from April 1998 to June 2013. Fifty-two patients (22 females and 30 males) with cerebral CM referred to our department underwent high-precision single-dose SRS using a LINAC with 6-MV photons. All patients had at least 1 bleeding episode prior to radiosurgery along with related symptoms. Median dose prescribed to the 85% to 95% isodose line encompassing the target volume was 15 Gy (range, 10-20). Out of the total 52 patients, follow-up data were available for 47 patients (90.4%). Median age was 35 years (range, 19-63). Median follow-up time was 5.17 years (range, 0.08-9.5) after SRS. Three hemorrhages were identified in the post-SRS period. Statistically significant decrease was observed in the annual hemorrhage rate after radiosurgical treatment (pre-SRS 39% vs post-SRS 1.21, P < .0001). Overall, there were no radiosurgery-related complications resulting in mortality. LINAC-based SRS may be considered as a treatment option for high-risk, symptomatic cerebral CM of selected patients with prior bleeding from lesions located at surgically inaccessible or eloquent brain areas.

  20. Hippocampal-Sparing Whole Brain Radiotherapy: A “How-To” Technique, Utilizing Helical Tomotherapy and LINAC-based Intensity Modulated Radiotherapy

    PubMed Central

    Gondi, Vinai; Tolakanahalli, Ranjini; Mehta, Minesh P.; Tewatia, Dinesh; Rowley, Howard; Kuo, John S.; Khuntia, Deepak; Tomé, Wolfgang A.

    2010-01-01

    Purpose Sparing the hippocampus during cranial irradiation poses important technical challenges with respect to contouring and treatment planning. Herein, we report our preliminary experience with whole-brain radiotherapy using hippocampal sparing for patients with brain metastases. Materials/Methods 5 anonymous patients previously treated with whole-brain radiotherapy with hippocampal sparing were reviewed. The hippocampus was contoured, and hippocampal avoidance regions were created using a 5mm volumetric expansion around the hippocampus. Helical tomotherapy and LINAC-based IMRT treatment plans were generated for a prescription dose of 30 Gy in 10 fractions. Results On average, the hippocampal avoidance volume was 3.3 cm3, occupying 2.1% of the whole brain planned target volume. Helical tomotherapy spared the hippocampus, with a median dose of 5.5 Gy and maximum dose of 12.8 Gy. LINAC-based IMRT spared the hippocampus, with a median dose of 7.8 Gy and maximum dose of 15.3 Gy. On a per-fraction basis, mean dose to the hippocampus (normalized to 2-Gy fractions) was reduced by 87% to 0.49 Gy2 using helical tomotherapy and by 81% to 0.73 Gy2 using LINAC-based IMRT. Target coverage and homogeneity was acceptable with both IMRT modalities, with differences largely attributed to more rapid dose fall-off with helical tomotherapy. Conclusion Modern IMRT techniques allow for sparing of the hippocampus with acceptable target coverage and homogeneity. Based on compelling preclinical evidence, a phase II cooperative group trial has been developed to test the postulated neurocognitive benefit. PMID:20598457

  1. Performance of a Novel Repositioning Head Frame for Gamma Knife Perfexion and Image-Guided Linac-Based Intracranial Stereotactic Radiotherapy

    SciTech Connect

    Ruschin, Mark; Nayebi, Nazanin; Carlsson, Per; Brown, Kevin

    2010-09-01

    Purpose: To evaluate the geometric positioning and immobilization performance of a vacuum bite-block repositioning head frame (RHF) system for Perfexion (PFX-SRT) and linac-based intracranial image-guided stereotactic radiotherapy (SRT). Methods and Materials: Patients with intracranial tumors received linac-based image-guided SRT using the RHF for setup and immobilization. Three hundred thirty-three fractions of radiation were delivered in 12 patients. The accuracy of the RHF was estimated for linac-based SRT with online cone-beam CT (CBCT) and for PFX-SRT with a repositioning check tool (RCT) and offline CBCT. The RCT's ability to act as a surrogate for anatomic position was estimated through comparison to CBCT image matching. Immobilization performance was evaluated daily with pre- and postdose delivery CBCT scans and RCT measurements. Results: The correlation coefficient between RCT- and CBCT-reported displacements was 0.59, 0.75, 0.79 (Right, Superior, and Anterior, respectively). For image-guided linac-based SRT, the mean three-dimensional (3D) setup error was 0.8 mm with interpatient ({Sigma}) and interfraction ({sigma}) variations of 0.1 and 0.4 mm, respectively. For PFX-SRT, the initial, uncorrected mean 3D positioning displacement in stereotactic coordinates was 2.0 mm, with {Sigma} = 1.1 mm and {sigma} = 0.8 mm. Considering only RCT setups <1mm (PFX action level) the mean 3D positioning displacement reduced to 1.3 mm, with {Sigma} = 0.9 mm and {sigma} = 0.4 mm. The largest contributing systematic uncertainty was in the superior-inferior direction (mean displacement = -0.5 mm; {Sigma} = 0.9 mm). The largest mean rotation was 0.6{sup o} in pitch. The mean 3D intrafraction motion was 0.4 {+-} 0.3 mm. Conclusion: The RHF provides excellent immobilization for intracranial SRT and PFX-SRT. Some small systematic uncertainties in stereotactic positioning exist and must be considered when generating PFX-SRT treatment plans. The RCT provides reasonable surrogacy

  2. Performance of a novel repositioning head frame for gamma knife perfexion and image-guided linac-based intracranial stereotactic radiotherapy.

    PubMed

    Ruschin, Mark; Nayebi, Nazanin; Carlsson, Per; Brown, Kevin; Tamerou, Messeret; Li, Winnie; Laperriere, Normand; Sahgal, Arjun; Cho, Young-Bin; Ménard, Cynthia; Jaffray, David

    2010-09-01

    To evaluate the geometric positioning and immobilization performance of a vacuum bite-block repositioning head frame (RHF) system for Perfexion (PFX-SRT) and linac-based intracranial image-guided stereotactic radiotherapy (SRT). Patients with intracranial tumors received linac-based image-guided SRT using the RHF for setup and immobilization. Three hundred thirty-three fractions of radiation were delivered in 12 patients. The accuracy of the RHF was estimated for linac-based SRT with online cone-beam CT (CBCT) and for PFX-SRT with a repositioning check tool (RCT) and offline CBCT. The RCT's ability to act as a surrogate for anatomic position was estimated through comparison to CBCT image matching. Immobilization performance was evaluated daily with pre- and postdose delivery CBCT scans and RCT measurements. The correlation coefficient between RCT- and CBCT-reported displacements was 0.59, 0.75, 0.79 (Right, Superior, and Anterior, respectively). For image-guided linac-based SRT, the mean three-dimensional (3D) setup error was 0.8 mm with interpatient (Sigma) and interfraction (sigma) variations of 0.1 and 0.4 mm, respectively. For PFX-SRT, the initial, uncorrected mean 3D positioning displacement in stereotactic coordinates was 2.0 mm, with Sigma = 1.1 mm and sigma = 0.8 mm. Considering only RCT setups <1mm (PFX action level) the mean 3D positioning displacement reduced to 1.3 mm, with Sigma = 0.9 mm and sigma = 0.4 mm. The largest contributing systematic uncertainty was in the superior-inferior direction (mean displacement = -0.5 mm; Sigma = 0.9 mm). The largest mean rotation was 0.6 degrees in pitch. The mean 3D intrafraction motion was 0.4 +/- 0.3 mm. The RHF provides excellent immobilization for intracranial SRT and PFX-SRT. Some small systematic uncertainties in stereotactic positioning exist and must be considered when generating PFX-SRT treatment plans. The RCT provides reasonable surrogacy for internal anatomic displacement. Copyright (c) 2010 Elsevier Inc

  3. Intra-operative 3D guidance and edema detection in prostate brachytherapy using a non-isocentric C-arm

    PubMed Central

    Jain, A.; Deguet, A.; Iordachita, I.; Chintalapani, G.; Vikal, S.; Blevins, J.; Le, Y.; Armour, E.; Burdette, C.; Song, D.; Fichtinger, G.

    2015-01-01

    Purpose Brachytherapy (radioactive seed insertion) has emerged as one of the most effective treatment options for patients with prostate cancer, with the added benefit of a convenient outpatient procedure. The main limitation in contemporary brachytherapy is faulty seed placement, predominantly due to the presence of intra-operative edema (tissue expansion). Though currently not available, the capability to intra-operatively monitor the seed distribution, can make a significant improvement in cancer control. We present such a system here. Methods Intra-operative measurement of edema in prostate brachytherapy requires localization of inserted radioactive seeds relative to the prostate. Seeds were reconstructed using a typical non-isocentric C-arm, and exported to a commercial brachytherapy treatment planning system. Technical obstacles for 3D reconstruction on a non-isocentric C-arm include pose-dependent C-arm calibration; distortion correction; pose estimation of C-arm images; seed reconstruction; and C-arm to TRUS registration. Results In precision-machined hard phantoms with 40–100 seeds and soft tissue phantoms with 45–87 seeds, we correctly reconstructed the seed implant shape with an average 3D precision of 0.35 mm and 0.24 mm, respectively. In a DoD Phase-1 clinical trial on six patients with 48–82 planned seeds, we achieved intra-operative monitoring of seed distribution and dosimetry, correcting for dose inhomogeneities by inserting an average of over four additional seeds in the six enrolled patients (minimum 1; maximum 9). Additionally, in each patient, the system automatically detected intra-operative seed migration induced due to edema (mean 3.84 mm, STD 2.13 mm, Max 16.19 mm). Conclusions The proposed system is the first of a kind that makes intra-operative detection of edema (and subsequent re-optimization) possible on any typical non-isocentric C-arm, at negligible additional cost to the existing clinical installation. It achieves a

  4. Anisotropic Electron-Photon and Electron-Phonon Interactions in Black Phosphorus

    DOE PAGES

    Ling, Xi; Huang, Shengxi; Hasdeo, Eddwi; ...

    2016-03-10

    Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride (GaTe) and tin selenide (SnSe), stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension to the properties of 2D materials and stimulates the development of angle-resolved photonics and electronics. However, understanding the effect of anisotropy has remained unsatisfactory to-date, as shown by a number of inconsistencies in the recent literatures. We use angle-resolved absorption and Raman spectroscopies to investigate the role of anisotropy on the electron-photon and electron-phonon interactions in BP. We highlight a non-trivial dependence between anisotropies andmore » flake thickness, photon and phonon energies. We show that once understood, the anisotropic optical absorption appears to be a reliable and simple way to identify the crystalline orientation of BP, which cannot be determined from Raman spectroscopy without the explicit consideration of excitation wavelength and flake thickness, as commonly used previously.« less

  5. Anisotropic Electron-Photon and Electron-Phonon Interactions in Black Phosphorus

    SciTech Connect

    Ling, Xi; Huang, Shengxi; Hasdeo, Eddwi; Liang, Liangbo; Parkin, William; Tatsumi, Yuki; Nugraha, Ahmad; Puretzky, Alexander A; Das, Paul; Sumpter, Bobby G; Geohegan, David B; Kong, Jing; Saito, Riichiro; Drndic, Marija; Meunier, Vincent; Dresselhaus, M

    2016-03-10

    Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride (GaTe) and tin selenide (SnSe), stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension to the properties of 2D materials and stimulates the development of angle-resolved photonics and electronics. However, understanding the effect of anisotropy has remained unsatisfactory to-date, as shown by a number of inconsistencies in the recent literatures. We use angle-resolved absorption and Raman spectroscopies to investigate the role of anisotropy on the electron-photon and electron-phonon interactions in BP. We highlight a non-trivial dependence between anisotropies and flake thickness, photon and phonon energies. We show that once understood, the anisotropic optical absorption appears to be a reliable and simple way to identify the crystalline orientation of BP, which cannot be determined from Raman spectroscopy without the explicit consideration of excitation wavelength and flake thickness, as commonly used previously.

  6. Means and method for calibrating a photon detector utilizing electron-photon coincidence

    NASA Technical Reports Server (NTRS)

    Srivastava, S. K. (Inventor)

    1984-01-01

    An arrangement for calibrating a photon detector particularly applicable for the ultraviolet and vacuum ultraviolet regions is based on electron photon coincidence utilizing crossed electron beam atom beam collisions. Atoms are excited by electrons which lose a known amount of energy and scatter with a known remaining energy, while the excited atoms emit photons of known radiation. Electrons of the known remaining energy are separated from other electrons and are counted. Photons emitted in a direction related to the particular direction of scattered electrons are detected to serve as a standard. Each of the electrons is used to initiate the measurements of a time interval which terminates with the arrival of a photon exciting the photon detector. Only the number of time intervals related to the coincidence correlation and of electrons scattered in the particular direction with the known remaining energy and photons of a particular radiation level emitted due to the collisions of such scattered electrons are counted. The detector calibration is related to the number of counted electrons and photons.

  7. Potential role for LINAC-based stereotactic radiosurgery for the treatment of 5 or more radioresistant melanoma brain metastases.

    PubMed

    Frakes, Jessica M; Figura, Nicholas B; Ahmed, Kamran A; Juan, Tzu-Hua; Patel, Neha; Latifi, Kujtim; Sarangkasiri, Siriporn; Strom, Tobin J; Chinnaiyan, Prakash; Rao, Nikhil G; Etame, Arnold B

    2015-11-01

    Linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) is a treatment option for patients with melanoma in whom brain metastases have developed. Very limited data are available on treating patients with ≥5 lesions. The authors sought to determine the effectiveness of SRS in patients with ≥5 melanoma brain metastases. A retrospective analysis of metastatic melanoma treated with SRS in a single treatment session for ≥5 lesions was performed. Magnetic resonance imaging studies were reviewed post-SRS to evaluate local control (LC). Disease progression on imaging was defined using the 2009 Response Evaluation Criteria in Solid Tumors (RECIST). Survival curves were calculated from the date of brain metastases diagnosis or the date of SRS by using the Kaplan-Meier (KM) method. Univariate and multivariate analysis (UVA and MVA, respectively) were performed using the Cox proportional-hazards model. The authors identified 149 metastatic brain lesions treated in 28 patients. The median patient age was 60.5 years (range 38-83 years), and the majority of patients (24 [85.7%]) had extracranial metastases. Four patients (14.3%) had received previous whole-brain radiotherapy (WBRT), and 11 (39.3%) had undergone previous SRS. The median planning target volume (PTV) was 0.34 cm3 (range 0.01-12.5 cm3). Median follow-up was 6.3 months (range 1-46 months). At the time of treatment, 7% of patients were categorized as recursive partitioning analysis (RPA) Class I, 89% as RPA Class II, and 4% as RPA Class III. The rate of local failure was 11.4%. Kaplan-Meier LC estimates at 6 and 12 months were 91.3% and 82.2%, respectively. A PTV volume≥0.34 cm3 was a significant predictor of local failure on UVA (HR 16.1, 95% CI 3.2-292.6, p<0.0001) and MVA (HR 14.8, 95% CI 3.0-268.5, p=0.0002). Sixteen patients (57.1%) were noted to have distant failure in the brain with a median time to failure of 3 months (range 1-15 months). Nine patients with distant failures received WBRT, and 7

  8. SU-E-J-70: Evaluation of Multiple Isocentric Intensity Modulated and Volumetric Modulated Arc Therapy Techniques Using Portal Dosimetry

    SciTech Connect

    Muralidhar, K Raja; Pangam, S; Kolla, J; Ponaganti, S; Ali, M; Vuba, S; Mariyappan, P; Babaiah, M; Komanduri, K

    2015-06-15

    Purpose: To develop a method for verification of dose distribution in a patient during treatment using multiple isocentric Intensity modulated and volumetric modulated arc therapy techniques with portal dosimetry. Methods: Varian True Beam accelerator, equipped with an aS1000 megavoltage electronic portal imaging device (EPID) has an integrated image mode for portal dosimetry (PD). The source-to-imager distance was taken at 150 cm to avoid collision to the table. Fourteen fractions were analyzed for this study. During shift in a single plan from one isocenter to another isocenter, EPID also shifted longitudinally for each field by taking the extent of divergence of beam into the consideration for EPID distance of 150cm. Patients were given treatment everyday with EPID placed in proper position for each field. Several parameters were obtained by comparing the dose distribution between fractions to fraction. The impact of the intra-fraction and inter-fraction of the patient in combination with isocenter shift of the beams were observed. Results: During treatment, measurements were performed by EPID and were evaluated by the gamma method. Analysis was done between fractions for multiple isocenter treatments. The pass rates of the gamma analysis with a criterion of 3% and 3 mm for the 14 fractions were over 97.8% with good consistency. Whereas maximum gamma exceeded the criteria in few fractions (in<1 cc vol). Average gamma was observed in the criteria of 0.5%. Maximum dose difference and average dose differences were less than 0.22 CU and 0.01 CU for maximum tolerance of 1.0 CU and 0.2 CU respectively. Conclusion: EPID with extended distance is ideal method to verify the multiple isocentric dose distribution in patient during treatment, especially cold and hot spots in junction dose. Verification of shifts as well as the dose differences between each fraction due to inter-fraction and intra-fraction of the patient can be derived.

  9. Polymer ring resonators for high density photonic and electronic-photonic integration

    NASA Astrophysics Data System (ADS)

    Sun, Haishan

    2009-12-01

    Electrical interconnect based on the copper wires will be the bottleneck for the future performance improvement of multi-core CPUs. Chip scale optical interconnect based on high density photonic and electronic-photonic integration is one of the feasible solutions. Ring resonators are promising photonic components serving as building blocks. High density integration of ring resonators is also important for high throughput lab-on-a-chip biosensors and opto-microwave integrated circuits. Polymer materials are compatible with most semiconductor fabrication processes. Polymers can be easily doped with rare earth ions, quantum dots etc. to make active optical devices. Especially, over several hundreds pm/V electro-optic (EO) coefficients and femtosecond scale response time of EO polymers enables photonic devices with sub 1V to millivolt drive voltages and terahertz bandwidth. This dissertation describes several technologies about design, simulation, fabrication, integration with electronic circuits and fiber optics of polymer ring resonators, and demonstrates three application examples of polymer ring resonators in communications and biochemical sensing. First the Beam Propagation Method (BPM) and the matrix analysis are combined to provide a fast circuit level simulation and design procedure of polymer ring resonators. Several low cost fabrication techniques based on electron beam irradiation effects on EO polymers are introduced. For the practical electronicphotonic integration, a hybrid integration scheme of EO polymer waveguide devices with Si integrated circuits is developed. One application is an all-dielectric RF sensor or receiver with sensitivity of 100 V/m and theoretical bandwidth over 100 GHz. This device is based on a novel structure with polymer ring resonator directly coupled to a side polished optical fiber. The other two examples are biochemical sensors based on multi-slot waveguide and ring resonator reflector structures.

  10. Utilization of optical tracking to validate a software-driven isocentric approach to robotic couch movements for proton radiotherapy

    SciTech Connect

    Hsi, Wen C. E-mail: Wenchien.hsi@sphic.org.cn; Zeidan, Omar A.; Law, Aaron; Schreuder, Andreas N.

    2014-08-15

    Purpose: An optical tracking and positioning system (OTPS) was developed to validate the software-driven isocentric (SDI) approach to control the six-degrees-of-freedom movement of a robotic couch. Methods: The SDI approach to movements rotating around a predefined isocenter, referred to as a GeoIso, instead of a mechanical pivot point was developed by the robot automation industry. With robotic couch-sag corrections for weight load in a traditional SDI approach, movements could be accurately executed for a GeoIso located within a 500 mm cubic volume on the couch for treatments. The accuracy of SDI movement was investigated using the OTPS. The GeoIso was assumed to align with the proton beam isocenter (RadIso) for gantry at the reference angle. However, the misalignment between GeoIso and RadIso was quantitatively investigated by measuring the displacements at various couch angles for a target placed at the RadIso at an initial couch angle. When circular target displacements occur on a plane, a relative isocenter shift (RIS) correction could be applied in the SDI movement to minimize target displacements. Target displacements at a fixed gantry angle without and with RIS correction were measured for 12 robotic couches. Target displacements for various gantry angles were performed on three couches in gantry rooms to study the gantry-induced RadIso shift. The RIS correction can also be applied for the RadIso shift. A new SDI approach incorporating the RIS correction with the couch sag is described in this study. In parallel, the accuracy of SDI translation movements for various weight loads of patients on the couch was investigated during positioning of patients for proton prostate treatments. Results: For a fixed gantry angle, measured target displacements without RIS correction for couch rotations in the horizontal plane varied from 4 to 20 mm. However, measured displacements perpendicular to couch rotation plane were about 2 mm for all couches. Extracted

  11. Results for local control and functional outcome after linac-based image-guided stereotactic radiosurgery in 190 patients with vestibular schwannoma

    PubMed Central

    Badakhshi, Harun; Graf, Reinhold; Böhmer, Dirk; Synowitz, Michael; Wiener, Edzard; Budach, Volker

    2014-01-01

    Background We assessed local control (LC) and functional outcome after linac-based stereotactic radiosurgery (SRS) for vestibular schwannoma (VS). Methods Between 1998 and 2008, 190 patients with VS were treated with SRS. All patients had tumors <2 cm diameter. Patients received 13.5 Gy prescribed to the 80th isodose at the tumor margin. The primary endpoint was LC. Secondary endpoints were symptomatic control and morbidity. Results Median follow-up was 40 months. LC was achieved in 88% of patients. There were no acute reactions exceeding Grade I. Trigeminal nerve dysfunction was present in 21.6% (n = 41) prior to SRS. After treatment, 85% (n = 155) had no change, 4.4,% (n = 8) had a relief of symptoms, 10.4% (n = 19) had new symptoms. Facial nerve dysfunction was present in some patients prior to treatment, e.g. paresis (12.6%; n = 24) and dysgeusia (0.5%; n = 1). After treatment 1.1% (n = 2) reported improvement and 6.1% (n = 11) experienced new symptoms. Hearing problems before SRS were present in 69.5% of patients (n = 132). After treatment, 62.6% (n = 144) had no change, 10.4% (n = 19) experienced improvement and 26.9% (n = 49) became hearing impaired. Conclusion This series of SRS for small VS provided similar LC rates to microsurgery; thus, it is effective as a non-invasive, image-guided procedure. The functional outcomes observed indicate the safety and effectiveness of linac-based SRS. Patients may now be informed of the clinical equivalence of SRS to microsurgery. PMID:23979079

  12. ITS version 5.0 : the integrated TIGER series of coupled electron/photon Monte Carlo transport codes.

    SciTech Connect

    Franke, Brian Claude; Kensek, Ronald Patrick; Laub, Thomas William

    2004-06-01

    ITS is a powerful and user-friendly software package permitting state of the art Monte Carlo solution of linear time-independent couple electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. Our goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theorists alike with a method for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permits the more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 5.0, the latest version of ITS, contains (1) improvements to the ITS 3.0 continuous-energy codes, (2)multigroup codes with adjoint transport capabilities, and (3) parallel implementations of all ITS codes. Moreover the general user friendliness of the software has been enhanced through increased internal error checking and improved code portability.

  13. Linac-based stereotactic radiosurgery (SRS) in the treatment of refractory trigeminal neuralgia: Detailed description of SRS procedure and reported clinical outcomes.

    PubMed

    Pokhrel, Damodar; Sood, Sumit; McClinton, Christopher; Saleh, Habeeb; Badkul, Rajeev; Jiang, Hongyu; Stepp, Timothy; Camarata, Paul; Wang, Fen

    2017-03-01

    To present our linac-based SRS procedural technique for medically and/or surgically refractory trigeminal neuralgia (TN) treatment and simultaneously report our clinical outcomes. Twenty-seven refractory TN patients who were treated with a single fraction of 80 Gy to TN. Treatment delivery was performed with a 4 mm cone size using 7-arc arrangement with differential-weighting for Novalis-TX with six MV-SRS (1000 MU/min) beam and minimized dose to the brainstem. Before each treatment, Winston-Lutz quality assurance (QA) with submillimeter accuracy was performed. Clinical treatment response was evaluated using Barrow Neurological Institute (BNI) pain intensity score, rated from I to V. Out of 27 patients, 22 (81%) and 5 (19%) suffered from typical and atypical TN, respectively, and had median follow-up interval of 12.5 months (ranged: 1-53 months). For 80 Gy prescriptions, delivered total average MU was 19440 ± 611. Average beam-on-time was 19.4 ± 0.6 min. Maximum dose and dose to 0.5 cc of brainstem were 13.4 ± 2.1 Gy (ranged: 8.4-15.9 Gy) and 3.6 ± 0.4 Gy (ranged: 3.0-4.9 Gy), respectively. With a median follow-up of 12.5 months (ranged: 1-45 months) in typical TN patients, the proportion of patients achieving overall pain relief was 82%, of which half achieved a complete pain relief with BNI score of I-II and half demonstrated partial pain reduction with BNI score of IIIA-IIIB. Four typical TN patients (18%) had no response to radiosurgery treatment. Of the patients who responded to treatment, actuarial pain recurrence free survival rates were approximately 100%, 75%, and 50% at 12 months, 15 months, and 24 months, respectively. Five atypical TN patients were included, who did not respond to treatment (BNI score: IV-V). However, no radiation-induced cranial-toxicity was observed in all patients treated. Linac-based SRS for medically and/or surgically refractory TN is a fast, effective, and safe treatment option for patients with typical TN who had excellent

  14. Equivalence in Dose Fall-Off for Isocentric and Nonisocentric Intracranial Treatment Modalities and Its Impact on Dose Fractionation Schemes

    SciTech Connect

    Ma Lijun; Sahgal, Arjun; Descovich, Martina; Cho, Y.-B.; Chuang, Cynthia; Huang, Kim; Laperriere, Normand J.; Shrieve, Dennis C.; Larson, David A.

    2010-03-01

    Purpose: To investigate whether dose fall-off characteristics would be significantly different among intracranial radiosurgery modalities and the influence of these characteristics on fractionation schemes in terms of normal tissue sparing. Methods and Materials: An analytic model was developed to measure dose fall-off characteristics near the target independent of treatment modalities. Variations in the peripheral dose fall-off characteristics were then examined and compared for intracranial tumors treated with Gamma Knife, Cyberknife, or Novalis LINAC-based system. Equivalent uniform biologic effective dose (EUBED) for the normal brain tissue was calculated. Functional dependence of the normal brain EUBED on varying numbers of fractions (1 to 30) was studied for the three modalities. Results: The derived model fitted remarkably well for all the cases (R{sup 2} > 0.99). No statistically significant differences in the dose fall-off relationships were found between the three modalities. Based on the extent of variations in the dose fall-off curves, normal brain EUBED was found to decrease with increasing number of fractions for the targets, with alpha/beta ranging from 10 to 20. This decrease was most pronounced for hypofractionated treatments with fewer than 10 fractions. Additionally, EUBED was found to increase slightly with increasing number of fractions for targets with alpha/beta ranging from 2 to 5. Conclusion: Nearly identical dose fall-off characteristics were found for the Gamma Knife, Cyberknife, and Novalis systems. Based on EUBED calculations, normal brain sparing was found to favor hypofractionated treatments for fast-growing tumors with alpha/beta ranging from 10 to 20 and single fraction treatment for abnormal tissues with low alpha/beta values such as alpha/beta = 2.

  15. A deterministic electron, photon, proton and heavy ion transport suite for the study of the Jovian moon Europa

    NASA Astrophysics Data System (ADS)

    Badavi, Francis F.; Blattnig, Steve R.; Atwell, William; Nealy, John E.; Norman, Ryan B.

    2011-02-01

    A Langley research center (LaRC) developed deterministic suite of radiation transport codes describing the propagation of electron, photon, proton and heavy ion in condensed media is used to simulate the exposure from the spectral distribution of the aforementioned particles in the Jovian radiation environment. Based on the measurements by the Galileo probe (1995-2003) heavy ion counter (HIC), the choice of trapped heavy ions is limited to carbon, oxygen and sulfur (COS). The deterministic particle transport suite consists of a coupled electron photon algorithm (CEPTRN) and a coupled light heavy ion algorithm (HZETRN). The primary purpose for the development of the transport suite is to provide a means to the spacecraft design community to rapidly perform numerous repetitive calculations essential for electron, photon, proton and heavy ion exposure assessment in a complex space structure. In this paper, the reference radiation environment of the Galilean satellite Europa is used as a representative boundary condition to show the capabilities of the transport suite. While the transport suite can directly access the output electron and proton spectra of the Jovian environment as generated by the jet propulsion laboratory (JPL) Galileo interim radiation electron (GIRE) model of 2003; for the sake of relevance to the upcoming Europa Jupiter system mission (EJSM), the JPL provided Europa mission fluence spectrum, is used to produce the corresponding depth dose curve in silicon behind a default aluminum shield of 100 mils (˜0.7 g/cm2). The transport suite can also accept a geometry describing ray traced thickness file from a computer aided design (CAD) package and calculate the total ionizing dose (TID) at a specific target point within the interior of the vehicle. In that regard, using a low fidelity CAD model of the Galileo probe generated by the authors, the transport suite was verified versus Monte Carlo (MC) simulation for orbits JOI-J35 of the Galileo probe

  16. SU-E-T-514: Simultaneously Determination of Radiation Isocentricity of Gantry, Collimator and Couch Using a Commercial Three-Dimensional Dosimetry QA Apparatus

    SciTech Connect

    Yan, S; Song, H; Wu, Q

    2014-06-01

    Purpose: Radiation isocentricity is an important benchmark for a LINAC and is typically determined by 3 separate film star-shots. We developed a technique to simultaneously determine the radiation isocenter of gantry, collimator and couch with a commercial 3D QA apparatus. Methods: The ArcCHECK from SunNuclear was used on two LINACs. It was aligned with room lasers. For gantry rotation, collimator and couch were set to zero and gantry was placed to 0, 49, 213 and 311 degrees. Similarly, a set of collimator/couch angles were chosen with the other two axes at neutral positions. The measured dose matrices were analyzed by an in-house MATLAB program. For each shot, the central axis was determined by computing the FWHM of the diode arrays. The largest inscribed circle from these central axis lines was used to determine isocenter: the radius as the benchmark of isocentricity and the coordinates of the center as the discrepancy of radiation isocenter to the origin defined by lasers. To validate the method, the couch was shifted by ~5 mm in all three directions and measurements were repeated. Results: The radius of the largest inscribed circle for gantry, collimator and couch are (0.3, 0.5, 0.2) mm for one LINAC and (0.2, 0.3, 0.1) mm for the other, in agreement with the film star-shots at annual QA. The discrepancies of radiation isocenter are generally within 1 mm, except gantry rotation on one LINAC due to the drift of foot laser. The differences in positions detected are consistent with the intentional predefined shift. Conclusion: We have demonstrated a technique for the simultaneous measurement of gantry, collimator, and couch isocentricity with a set of carefully chosen irradiation parameters based on the specific construction geometry of the 3D detector ArcCheck. This can replace the standard film star-shots. The future work includes improving operation efficiency.

  17. Silicon/III-V laser with super-compact diffraction grating for WDM applications in electronic-photonic integrated circuits.

    PubMed

    Wang, Yadong; Wei, Yongqiang; Huang, Yingyan; Tu, Yongming; Ng, Doris; Lee, Cheewei; Zheng, Yunan; Liu, Boyang; Ho, Seng-Tiong

    2011-01-31

    We have demonstrated a heterogeneously integrated III-V-on-Silicon laser based on an ultra-large-angle super-compact grating (SCG). The SCG enables single-wavelength operation due to its high-spectral-resolution aberration-free design, enabling wavelength division multiplexing (WDM) applications in Electronic-Photonic Integrated Circuits (EPICs). The SCG based Si/III-V laser is realized by fabricating the SCG on silicon-on-insulator (SOI) substrate. Optical gain is provided by electrically pumped heterogeneous integrated III-V material on silicon. Single-wavelength lasing at 1550 nm with an output power of over 2 mW and a lasing threshold of around 150 mA were achieved.

  18. Flat-panel cone-beam CT on a mobile isocentric C-arm for image-guided brachytherapy

    NASA Astrophysics Data System (ADS)

    Jaffray, David A.; Siewerdsen, Jeffrey H.; Edmundson, Gregory K.; Wong, John W.; Martinez, Alvaro A.

    2002-05-01

    Flat-panel imager (FPI) based cone-beam computed tomography (CBCT) is a strong candidate technology for intraoperative imaging in image-guided procedures such as brachytherapy. The soft-tissue imaging performance and potential navigational utility have been investigated using a computer-controlled benchtop system. These early results have driven the development of an isocentric C-arm for intraoperative FPI-CBCT, capable of collecting 94 projections over 180 degrees in 110 seconds. The C-arm system employs a large-area FPI with 400 micron pixel pitch and Gd2O2S:Tb scintillator. Image acquisition, processing and reconstruction are orchestrated under a single Windows-based application. Reconstruction is performed by a modified Feldkamp algorithm implemented on a high-speed reconstruction engine. Non-idealities in the source and detector trajectories during orbital motion has been quantified and tested for stability. Cone-beam CT imaging performance was tested through both quantitative and qualitative methods. The system MTF was measured using a wire phantom and demonstrated frequency pass out to 0.6 mm-1. Voxel noise was measured at 2.7 percent in a uniform 12 cm diameter water bath. Anatomical phantoms were employed for qualitative evaluation of the imaging performance. Images of an anaesthetized rabbit demonstrated the capacity of the system to discern soft-tissue structures within a living subject while offering sub-millimeter spatial resolution. The dose delivered in each of the imaging procedures was estimated from in-air exposure measurements to be approximately 0.1 cGy. Imaging studies of an anthropomorphic prostate phantom were performed with and without radioactive seeds. Soft-tissue imaging performance and seed detection appear to satisfy the imaging and navigation requirements for image-guided brachytherapy. These investigations advance the development and evaluation of such technology for image-guided surgical procedures, including brachytherapy

  19. SU-F-T-647: Linac-Based Stereotactic Radiosurgery (SRS) in the Treatment of Trigeminal Neuralgia: Detailed Description of SRS Procedural Technique and Reported Clinical Outcomes

    SciTech Connect

    Pokhrel, D; Sood, S; Badkul, R; Jiang, H; Stepp, T; Camarata, P; Wang, F

    2016-06-15

    Purpose: SRS is an effective non-invasive alternative treatment modality with minimal-toxicity used to treat patients with medically/surgically refractory trigeminal neuralgia root(TNR) or those who may not tolerate surgical intervention. We present our linac-based SRS procedure for TNR treatment and simultaneously report our clinical outcomes. Methods: Twenty-eight TNR-patients treated with frame-based SRS at our institution (2009–2015) with a single-fraction point-dose of 60-80Gy to TNR were included in this IRB-approved study. Experienced neurosurgeon and radiation oncologist delineated the TNR on 1.0mm thin 3D-FIESTA-MRI that was co-registered with 0.7mm thin planning-CT. Treatment plans were generated in iPlan (BrainLAB) with a 4-mm diameter cone using 79 arcs with differential-weighting for Novalis-TX 6MV-SRS(1000MU/min) beam and optimized to minimize brainstem dose. Winston-Lutz test was performed before each treatment delivery with sub-millimeter isocenter accuracy. Quality assurance of frame placement was maintained by helmet-bobble-measurement before simulation-CT and before patient setup at treatment couch. OBI-CBCT scan was performed for patient setup verification without applying shifts. On clinical follow up, treatment response was assessed using Barrow Neurological Institute Pain Intensity Score(BNI-score:I–V). Results: 26/28 TNR-patients (16-males/10-females) who were treated with following single-fraction point-dose to isocenter: 80Gy(n=22),75Gy(n=1),70Gy(n=2) and 60Gy(n=1, re-treatment) were followed up. Median follow-up interval was 8.5-months (ranged:1–48.5months). Median age was 70-yr (ranged:43–93-yr). Right/left TNR ratio was 15/11. Delivered total # of average MUs was 19034±1204. Average beam-on-time: 19.0±1.3min. Brainstem max-dose and dose to 0.5cc were 13.3±2.4Gy (ranged:8.1–16.5Gy) and 3.6±0.4Gy (ranged:3.0–4.9Gy). On average, max-dose to optic-apparatus was ≤1.2Gy. Mean value of max-dose to eyes/lens was 0.26Gy/0.11Gy

  20. SU-E-T-567: A Three-Field Mono-Isocentric Inverse Treatment Planning Method for the Patients with Larger Breasts

    SciTech Connect

    Zhang, T; Marina, O; Chen, P; Teahan, M; Liu, Q; Benedetti, L

    2014-06-01

    Purpose: The purpose of this study is to develop a three-field monoisocentric inverse breast treatment planning technique without the use of half-beam block. Methods: Conventional three-field breast treatment with supraclavicular half-beam blocked requires two isocenters when the breast is too large to be contained within half-beam. The inferior border of the supraclavicular field and superior borders of the breast fields are matched on patient's skin with the light field. This method causes a large dose variation in the matching region due to daily setup uncertainties and requires a longer treatment setup time. We developed a three-field mono-isocentric planning method for the treatment of larger breasts. The three fields share the same isocenter located in the breast. Beam matching is achieved by rotating collimator, couch and gantry. Furthermore, we employed a mixed open-IMRT inverse optimization method to improve dose uniformity and coverage. Results: Perfect geometric beam matching was achieved by rotating couch, collimator and gantry together. Treatment setup time was significantly reduced without light-field matching during treatment deliveries. Inverse mixed open-IMRT optimization method achieved better dose uniformity and PTV coverage while keeping sufficient air flash to compensate setup and breast shape changes in daily treatments. Conclusion: By eliminating light field matching, the three-field mono-isocentric treatment method can significantly reduce setup time and uncertainty for large breast patients. Plan quality is further improved by inverse IMRT planning.

  1. SU-E-T-355: A Comparative Study of Robotic and Linac-Based Stereotactitc Body Radiation Therapy for Lumbar Spinal Tumors

    SciTech Connect

    Bossart, E; Monterroso, M; Couto, M; Ly, B; Mihaylov, I

    2014-06-01

    Purpose: Dosimetrically compare CyberKnife (CK) and linac-based (LB) stereotactic body radiotherapy (SBRT) plans for lumbar spine. Methods: Ten patient plans with lumbar spine tumors treated with CK were selected and retrospectively optimized using three techniques: CK, volumetric modulated arc (VMAT, three arcs), and 9-field-intensity modulated radiotherapy (IMRT). For the LB plans, the target volume was expanded by 1mm to accommodate additional uncertainty in patient positioning. All plans were optimized to a prescription dose of 27Gy in 3 fractions covering 90% of the PTV. If the dose constraints to the cauda equina (cauda) were not met, the prescription dose was lowered to 24Gy. Parameters evaluated included Paddick Conformity-Index (CI) and Gradient-Index (GI). A two-tailed paired t-test was used to establish statistically significant differences in cauda doses. Results: Target volumes for LB plans were on average 38% larger. In terms of the indices, the closer the index values to unity the steeper the dose falloff and the higher the dose conformity to the target. The results showed that LB plans were in general statistically superior to CK plans. The IMRT plan showed the best average gradient index of 2.995, with VMAT and CK GI values of 3.699 and 5.476, respectively. Similarly, the same trend occurs with the average CI results: 0.821, 0.814, and 0.758, corresponding to IMRT, VMAT, and CK. Notably, in one CK plan the target dose was reduced to 24Gy to meet cauda constraints. Additionally, there was a statistically significant dose difference for the cauda between the CK and LB plans. Conclusion: This study demonstrates that LB plans for lumbar spine SBRT can be as effective or even better than CK plans. Despite the expansion of the target volume, the LB plans did not demonstrate dosimetric inferiority. The LB plans Resultin 2-to-3 fold decrease of treatment time.

  2. Spectral broadening and electron-photon coupling in III-V infrared detectors of low dimensional quantum confined system

    NASA Astrophysics Data System (ADS)

    Joy, Soumitra R.; Mohammedy, Farseem M.

    2016-05-01

    Present work explores the mid-IR photodetection mechanism in III-V quantum confined system in twofold ways. Firstly, it models the extent of spectral linewidth broadening of photo-detector. Secondly, it investigates whether a strong perturbation of light can modulate the electronic bandstructure. Photo-absorption mechanism in the detector correlated to reduced carrier lifetime in ground state leading to homogeneous spectral widening is calculated. Besides, contribution of non-uniform size and composition of quantum dots towards spectral broadening is modeled in order to get the envelop of inhomogeneously broadened photocurrent spectrum. Our model generates photocurrent spectrum with 1.4 μm broadening centered at 3.5 μm at 77 K for a DWELL-IP, which agrees with the experimental result. The calculated photocurrent spectral width of 1.3 μm for GaAs/AlGaAs Quantum Well (QW) centered at 8.31 μm at 77 K also supports experimental data. In addition, our calculation reveals the emergence of a broad resonant peak in the spectrum of QW-IP in far infrared region (20-50 μm) as the photon volume density increases up to 0.1% of carrier density inside the active region. We introduce a hybrid density-of-states for strongly coupled electron-photon system to explain both mid and far IR peak.

  3. Isocentric Navigation of Percutaneous Endoscopic Transforaminal Discectomy at the L5/S1 Level in Difficult Puncture Cases: A Technical Note.

    PubMed

    Fan, Guoxin; Wang, Teng; Hu, Shuo; Guan, Xiaofei; Gu, Xin; He, Shisheng

    2017-05-01

    Accurate puncture during percutaneous transforaminal endoscopic discectomy at the L5/S1 level in cases with high iliac crest and narrow foramen were difficult, even though the difficulties of foraminoplasty could be overcome by advanced instruments like reamers. The report aimed to describe an isocentric navigation technique with a definite pathway in difficult puncture cases at the L5/S1 level. Technical note. Difficult punctures were defined as over 10 punctures of the needle before obtaining an ideal puncture location by senior surgeons with experience of over 500 percutaneous endoscopic transforaminal discectomy (PETD) cases. A total of 124 punctures were recorded in 11 difficult puncture cases at the L5/S1 level. A definite pathway was created by an isocentric navigation theory, which was based on a surface locator and an arch-guided device. The surface locator was used to rapidly and accurately identify the puncture target with the recognition of the surrounding rods under fluoroscopy. The arch-guided device can ensure that the puncture target always remains at the center of a virtual sphere. We recorded the puncture times, fluoroscopy exposure times, radiation exposure time, operative time, visual analog scale (VAS) score, Japanese Orthopeadic Association (JOA) score, and patient satisfaction. The average puncture times were significantly reduced to 1.27 with the arch-guided device compared with conventional puncture methods (P < 0.05). The average operative time was 90.09 ± 11.00 minutes and the fluoroscopy times were 53.36 ± 5.85. The radiation exposure time was 50.91 ± 5.20 seconds. VAS score of leg and back pain, as well as JOA score, were all significantly improved after surgery (P < 0.05). The excellent and good rate of satisfaction was 90.91%. No major complications, including cerebral fluid leakage, surgical infection, and postoperative nerve root injury, were recorded in this small sample. This was a small-sample study with a short follow-up. The

  4. Dosimetric comparison of Linac-based (BrainLAB®) and robotic radiosurgery (CyberKnife ®) stereotactic system plans for acoustic schwannoma.

    PubMed

    Dutta, Debnarayan; Balaji Subramanian, S; Murli, V; Sudahar, H; Gopalakrishna Kurup, P G; Potharaju, Mahadev

    2012-02-01

    A dosimetric comparison of linear accelerator (LA)-based (BrainLAB) and robotic radiosurgery (RS) (CyberKnife) systems for acoustic schwannoma (Acoustic neuroma, AN) was carried out. Seven patients with radiologically confirmed unilateral AN were planned with both an LA-based (BrainLAB) and robotic RS (CyberKnife) system using the same computed tomography (CT) dataset and contours. Gross tumour volume (GTV) was contoured on post-contrast magnetic resonance imaging (MRI) scan [planning target volume (PTV) margin 2 mm]. Planning and calculation were done with appropriate calculation algorithms. The prescribed isodose in both systems was considered adequate to cover at least 95% of the contoured target. Plan evaluations were done by examining the target coverage by the prescribed isodose line, and high- and low-dose volumes. Isodose plans and dose volume histograms generated by the two systems were compared. There was no statistically significant difference between the contoured volumes between the systems. Tumour volumes ranged from 380 to 3,100 mm(3). Dose prescription was 13-15 Gy in single fraction (median prescribed isodose 85%). There were no significant differences in conformity index (CI) (0.53 versus 0.58; P = 0.225), maximum brainstem dose (4.9 versus 4.7 Gy; P = 0.935), 2.5-Gy volume (39.9 versus 52.3 cc; P = 0.238) or 5-Gy volume (11.8 versus 16.8 cc; P = 0.129) between BrainLAB and CyberKnife system plans. There were statistically significant differences in organs at risk (OAR) doses, such as mean cochlear dose (6.9 versus 5.4 Gy; P = 0.001), mean mesial temporal dose (2.6 versus 1.7 Gy; P = 0.07) and high-dose (10 Gy) volume (3.2 versus 5.2 cc; P = 0.017). AN patients planned with the CyberKnife system had superior OAR (cochlea and mesial temporal lobe) sparing compared with those planned with the Linac-based system. Further evaluation of these findings in prospective studies with clinical correlation will provide actual clinical benefit from the

  5. MRI-guided stereotaxic targeting in pigs based on a stereotaxic localizer box fitted with an isocentric frame and use of SurgiPlan computer-planning software.

    PubMed

    Bjarkam, Carsten R; Cancian, Graziano; Glud, Andreas N; Ettrup, Kaare S; Jørgensen, Rasmus L; Sørensen, Jens-Christian

    2009-10-15

    We present a stereotaxic procedure enabling MRI-guided isocentric stereotaxy in pigs. The procedure is based on the Leksell stereotaxic arch principle, and a stereotaxic localizer box with an incorporated fiducial marking system (sideplates) defining a stereotaxic space similar to the clinical Leksell system. The obtained MRIs can be imported for 3D-reconstruction and coordinate calculation in the clinical stereotaxic software planning system (Leksell SurgiPlan, Elekta AB, Sweden). After MRI the sideplates are replaced by a modified Leksell arch accommodating clinical standard manipulators for isocentric placement of DBS-electrodes, neural tracers and therapeutics in the calculated target coordinates. The mechanical accuracy of the device was within 0.3-0.5 mm. Stereotaxic MRIs were imported to the stereotaxic software planning system with a mean error of 0.4-0.5 mm and a max error of 0.8-0.9 mm. Application accuracy measured on a phantom and on inserted skull markers in nine pigs was within 1 mm in all planes. The intracerebral application accuracy found after placement of 10 manganese trajectories within the full extent of the intracerebral stereotaxic space in two minipigs was equally randomly distributed and within 0.7+/-0.4; 0.5+/-0.4; and 0.7+/-0.3mm in the X, Y, and Z plane. Injection of neural tracers in the subgenual gyrus of three minipigs and placement of encapsulated gene-modified cells in four minipigs confirmed the accuracy and functionality of the described procedure. We conclude that the devised technique and instrumentation enable high-precision stereotaxic procedures in pigs that may benefit future large animal neuroscience research and outline the technical considerations for a similar stereotaxic methodology in other animals.

  6. Use of intraoperative isocentric C-arm 3D fluoroscopy for sextant percutaneous pedicle screw placement: case report and review of the literature.

    PubMed

    Acosta, Frank L; Thompson, Timothy L; Campbell, Stacey; Weinstein, Philip R; Ames, Christopher P

    2005-01-01

    Three-dimensional (3D) fluoroscopy-based image guidance system using an isocentric C-arm (Iso-C) fluoroscope was shown to be as effective as computed tomography-based systems in guiding the accurate percutaneous placement of lumbar pedicle screws in cadavers. To date, however, no description is available of the intraoperative use of 3D fluoroscopy to guide lumbar pedicle screw placement in an actual spinal fusion procedure. We report a case in which isocentric 3D fluoroscopic images, along with image-guidance software, were used to guide the placement of percutaneous pedicle screws for fusion in a patient with degenerative spondylolisthesis. Operating room of a large academic medical center during the placement of percutaneous pedicle screws in a patient with degenerative spondylolisthesis. A percutaneous dynamic reference array was attached to the L3 spinous process. A satisfactory image set was obtained and automatically registered. The L4 and L5 pedicles were localized, and pedicle holes were then cannulated, drilled and tapped. A screw was then inserted using the Sextant system for percutaneous pedicle screws. In this manner, bilateral pedicle screws were inserted into the L4-L5 pedicles. All steps of pedicle cannulation were performed under Iso-C 3D image guidance. A postoperative computed tomography scan showed accurate placement of all pedicle screws. The patient experienced an improvement in leg pain with no new neurologic deficits. The present case is the first case to demonstrate the intraoperative use of a 3D fluoroscopy-based image-guidance system for accurate navigation during lumbar pedicle screw placement.

  7. Monte Carlo electron-photon transport using GPUs as an accelerator: Results for a water-aluminum-water phantom

    SciTech Connect

    Su, L.; Du, X.; Liu, T.; Xu, X. G.

    2013-07-01

    An electron-photon coupled Monte Carlo code ARCHER - Accelerated Radiation-transport Computations in Heterogeneous Environments - is being developed at Rensselaer Polytechnic Institute as a software test bed for emerging heterogeneous high performance computers that utilize accelerators such as GPUs. In this paper, the preliminary results of code development and testing are presented. The electron transport in media was modeled using the class-II condensed history method. The electron energy considered ranges from a few hundred keV to 30 MeV. Moller scattering and bremsstrahlung processes above a preset energy were explicitly modeled. Energy loss below that threshold was accounted for using the Continuously Slowing Down Approximation (CSDA). Photon transport was dealt with using the delta tracking method. Photoelectric effect, Compton scattering and pair production were modeled. Voxelised geometry was supported. A serial ARHCHER-CPU was first written in C++. The code was then ported to the GPU platform using CUDA C. The hardware involved a desktop PC with an Intel Xeon X5660 CPU and six NVIDIA Tesla M2090 GPUs. ARHCHER was tested for a case of 20 MeV electron beam incident perpendicularly on a water-aluminum-water phantom. The depth and lateral dose profiles were found to agree with results obtained from well tested MC codes. Using six GPU cards, 6x10{sup 6} histories of electrons were simulated within 2 seconds. In comparison, the same case running the EGSnrc and MCNPX codes required 1645 seconds and 9213 seconds, respectively, on a CPU with a single core used. (authors)

  8. A Deterministic Electron, Photon, Proton and Heavy Ion Radiation Transport Suite for the Study of the Jovian System

    NASA Technical Reports Server (NTRS)

    Norman, Ryan B.; Badavi, Francis F.; Blattnig, Steve R.; Atwell, William

    2011-01-01

    A deterministic suite of radiation transport codes, developed at NASA Langley Research Center (LaRC), which describe the transport of electrons, photons, protons, and heavy ions in condensed media is used to simulate exposures from spectral distributions typical of electrons, protons and carbon-oxygen-sulfur (C-O-S) trapped heavy ions in the Jovian radiation environment. The particle transport suite consists of a coupled electron and photon deterministic transport algorithm (CEPTRN) and a coupled light particle and heavy ion deterministic transport algorithm (HZETRN). The primary purpose for the development of the transport suite is to provide a means for the spacecraft design community to rapidly perform numerous repetitive calculations essential for electron, proton and heavy ion radiation exposure assessments in complex space structures. In this paper, the radiation environment of the Galilean satellite Europa is used as a representative boundary condition to show the capabilities of the transport suite. While the transport suite can directly access the output electron spectra of the Jovian environment as generated by the Jet Propulsion Laboratory (JPL) Galileo Interim Radiation Electron (GIRE) model of 2003; for the sake of relevance to the upcoming Europa Jupiter System Mission (EJSM), the 105 days at Europa mission fluence energy spectra provided by JPL is used to produce the corresponding dose-depth curve in silicon behind an aluminum shield of 100 mils ( 0.7 g/sq cm). The transport suite can also accept ray-traced thickness files from a computer-aided design (CAD) package and calculate the total ionizing dose (TID) at a specific target point. In that regard, using a low-fidelity CAD model of the Galileo probe, the transport suite was verified by comparing with Monte Carlo (MC) simulations for orbits JOI--J35 of the Galileo extended mission (1996-2001). For the upcoming EJSM mission with a potential launch date of 2020, the transport suite is used to compute

  9. A Deterministic Electron, Photon, Proton and Heavy Ion Radiation Transport Suite for the Study of the Jovian System

    NASA Technical Reports Server (NTRS)

    Norman, Ryan B.; Badavi, Francis F.; Blattnig, Steve R.; Atwell, William

    2011-01-01

    A deterministic suite of radiation transport codes, developed at NASA Langley Research Center (LaRC), which describe the transport of electrons, photons, protons, and heavy ions in condensed media is used to simulate exposures from spectral distributions typical of electrons, protons and carbon-oxygen-sulfur (C-O-S) trapped heavy ions in the Jovian radiation environment. The particle transport suite consists of a coupled electron and photon deterministic transport algorithm (CEPTRN) and a coupled light particle and heavy ion deterministic transport algorithm (HZETRN). The primary purpose for the development of the transport suite is to provide a means for the spacecraft design community to rapidly perform numerous repetitive calculations essential for electron, proton and heavy ion radiation exposure assessments in complex space structures. In this paper, the radiation environment of the Galilean satellite Europa is used as a representative boundary condition to show the capabilities of the transport suite. While the transport suite can directly access the output electron spectra of the Jovian environment as generated by the Jet Propulsion Laboratory (JPL) Galileo Interim Radiation Electron (GIRE) model of 2003; for the sake of relevance to the upcoming Europa Jupiter System Mission (EJSM), the 105 days at Europa mission fluence energy spectra provided by JPL is used to produce the corresponding dose-depth curve in silicon behind an aluminum shield of 100 mils ( 0.7 g/sq cm). The transport suite can also accept ray-traced thickness files from a computer-aided design (CAD) package and calculate the total ionizing dose (TID) at a specific target point. In that regard, using a low-fidelity CAD model of the Galileo probe, the transport suite was verified by comparing with Monte Carlo (MC) simulations for orbits JOI--J35 of the Galileo extended mission (1996-2001). For the upcoming EJSM mission with a potential launch date of 2020, the transport suite is used to compute

  10. Comparison of Isocentric C-Arm 3-Dimensional Navigation and Conventional Fluoroscopy for Percutaneous Retrograde Screwing for Anterior Column Fracture of Acetabulum

    PubMed Central

    He, Jiliang; Tan, Guoqing; Zhou, Dongsheng; Sun, Liang; Li, Qinghu; Yang, Yongliang; Liu, Ping

    2016-01-01

    Abstract Percutaneous screw insertion for minimally displaced or reducible acetabular fracture using x-ray fluoroscopy and computer-assisted navigation system has been advocated by some authors. The purpose of this study was to compare intraoperative conditions and clinical results between isocentric C-arm 3-dimensional (Iso-C 3D) fluoroscopy and conventional fluoroscopy for percutaneous retrograde screwing of acetabular anterior column fracture. A prospective cohort study was conducted. A total of 22 patients were assigned to 2 different groups: 10 patients in the Iso-C 3D navigation group and 12 patients in the conventional group. The operative time, fluoroscopic time, time of screw insertion, blood loss, and accuracy were analyzed between the 2 groups. There were significant differences in operative time, screw insertion time, fluoroscopy time, and mean blood loss between the 2 groups. Totally 2 of 12 (16.7%) screws were misplaced in the conventional fluoroscopy group, and all 10 screws were in safe zones in the navigation group. Percutaneous screw fixation using the Iso-C 3D computer-assisted navigation system significantly reduced the intraoperative fluoroscopy time and blood loss in percutaneous screwing for acetabular anterior column fracture. The Iso-C 3D computer-assisted navigation system provided a reliable and effective method for percutaneous screw insertion in acetabular anterior column fractures compared to conventional fluoroscopy. PMID:26765448

  11. Dose Gradient Near Target-Normal Structure Interface for Nonisocentric CyberKnife and Isocentric Intensity-Modulated Body Radiotherapy for Prostate Cancer

    SciTech Connect

    Hossain, Sabbir; Xia Ping; Huang, Kim; Descovich, Martina; Chuang, Cynthia; Gottschalk, Alexander R.; Roach, Mack; Ma Lijun

    2010-09-01

    Purpose: The treatment planning quality between nonisocentric CyberKnife (CK) and isocentric intensity modulation treatment was studied for hypofractionated prostate body radiotherapy. In particular, the dose gradient across the target and the critical structures such as the rectum and bladder was characterized. Methods and Materials: In the present study, patients treated with CK underwent repeat planning for nine fixed-field intensity-modulated radiotherapy (IMRT) using identical contour sets and dose-volume constraints. To calculate the dose falloff, the clinical target volume contours were expanded 30 mm anteriorly and posteriorly and 50 mm uniformly in other directions for all patients in the CK and IMRT plans. Results: We found that all the plans satisfied the dose-volume constraints, with the CK plans showing significantly better conformity than the IMRT plans at a relative greater dose inhomogeneity. The rectal and bladder volumes receiving a low dose were also lower for CK than for IMRT. The average conformity index, the ratio of the prescription isodose volume and clinical target volume, was 1.18 {+-} 0.08 for the CK plans vs. 1.44 {+-} 0.11 for the IMRT plans. The average homogeneity index, the ratio of the maximal dose and the prescribed dose to the clinical target volume, was 1.45 {+-} 0.12 for the CK plans vs. 1.28 {+-} 0.06 for the IMRT plans. The average percentage of dose falloff was 2.9% {+-} 0.8%/mm for CK and 3.1% {+-} 1.0%/mm for IMRT in the anterior direction, 3.8% {+-} 1.6%/mm for CK and 3.2% {+-} 1.9%/mm for IMRT in the posterior direction, and 3.6% {+-} 0.4% for CK and 3.6% {+-} 0.4% for IMRT in all directions. Conclusion: Nonisocentric CK was as capable of producing equivalent fast dose falloff as high-number fixed-field IMRT delivery.

  12. Thermally controlled coupling of a rolled-up microtube integrated with a waveguide on a silicon electronic-photonic integrated circuit.

    PubMed

    Zhong, Qiuhang; Tian, Zhaobing; Veerasubramanian, Venkat; Dastjerdi, M Hadi Tavakoli; Mi, Zetian; Plant, David V

    2014-05-01

    We report on the first experimental demonstration of the thermal control of coupling strength between a rolled-up microtube and a waveguide on a silicon electronic-photonic integrated circuit. The microtubes are fabricated by selectively releasing a coherently strained GaAs/InGaAs heterostructure bilayer. The fabricated microtubes are then integrated with silicon waveguides using an abruptly tapered fiber probe. By tuning the gap between the microtube and the waveguide using localized heaters, the microtube-waveguide evanescent coupling is effectively controlled. With heating, the extinction ratio of a microtube whispering-gallery mode changes over an 18 dB range, while the resonant wavelength remains approximately unchanged. Utilizing this dynamic thermal tuning effect, we realize coupling modulation of the microtube integrated with the silicon waveguide at 2 kHz with a heater voltage swing of 0-6 V.

  13. ITS version 5.0 :the integrated TIGER series of coupled electron/Photon monte carlo transport codes with CAD geometry.

    SciTech Connect

    Franke, Brian Claude; Kensek, Ronald Patrick; Laub, Thomas William

    2005-09-01

    ITS is a powerful and user-friendly software package permitting state-of-the-art Monte Carlo solution of linear time-independent coupled electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. Our goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theorists alike with a method for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permits the more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 5.0, the latest version of ITS, contains (1) improvements to the ITS 3.0 continuous-energy codes, (2) multigroup codes with adjoint transport capabilities, (3) parallel implementations of all ITS codes, (4) a general purpose geometry engine for linking with CAD or other geometry formats, and (5) the Cholla facet geometry library. Moreover, the general user friendliness of the software has been enhanced through increased internal error checking and improved code portability.

  14. Volume CT with a flat-panel detector on a mobile, isocentric C-arm: pre-clinical investigation in guidance of minimally invasive surgery.

    PubMed

    Siewerdsen, J H; Moseley, D J; Burch, S; Bisland, S K; Bogaards, A; Wilson, B C; Jaffray, D A

    2005-01-01

    A mobile isocentric C-arm (Siemens PowerMobil) has been modified in our laboratory to include a large area flat-panel detector (in place of the x-ray image intensifier), providing multi-mode fluoroscopy and cone-beam computed tomography (CT) imaging capability. This platform represents a promising technology for minimally invasive, image-guided surgical procedures where precision in the placement of interventional tools with respect to bony and soft-tissue structures is critical. The image quality and performance in surgical guidance was investigated in pre-clinical evaluation in image-guided spinal surgery. The control, acquisition, and reconstruction system are described. The reproducibility of geometric calibration, essential to achieving high three-dimensional (3D) image quality, is tested over extended time scales (7 months) and across a broad range in C-arm angulation (up to 45 degrees), quantifying the effect of improper calibration on spatial resolution, soft-tissue visibility, and image artifacts. Phantom studies were performed to investigate the precision of 3D localization (viz., fiber optic probes within a vertebral body) and effect of lateral projection truncation (limited field of view) on soft-tissue detectability in image reconstructions. Pre-clinical investigation was undertaken in a specific spinal procedure (photodynamic therapy of spinal metastases) in five animal subjects (pigs). In each procedure, placement of fiber optic catheters in two vertebrae (L1 and L2) was guided by fluoroscopy and cone-beam CT. Experience across five procedures is reported, focusing on 3D image quality, the effects of respiratory motion, limited field of view, reconstruction filter, and imaging dose. Overall, the intraoperative cone-beam CT images were sufficient for guidance of needles and catheters with respect to bony anatomy and improved surgical performance and confidence through 3D visualization and verification of transpedicular trajectories and tool placement

  15. Validation of the MCNP6 electron-photon transport algorithm: multiple-scattering of 13- and 20-MeV electrons in thin foils

    NASA Astrophysics Data System (ADS)

    Dixon, David A.; Hughes, H. Grady

    2017-09-01

    This paper presents a validation test comparing angular distributions from an electron multiple-scattering experiment with those generated using the MCNP6 Monte Carlo code system. In this experiment, a 13- and 20-MeV electron pencil beam is deflected by thin foils with atomic numbers from 4 to 79. To determine the angular distribution, the fluence is measured down range of the scattering foil at various radii orthogonal to the beam line. The characteristic angle (the angle for which the max of the distribution is reduced by 1/e) is then determined from the angular distribution and compared with experiment. Multiple scattering foils tested herein include beryllium, carbon, aluminum, copper, and gold. For the default electron-photon transport settings, the calculated characteristic angle was statistically distinguishable from measurement and generally broader than the measured distributions. The average relative difference ranged from 5.8% to 12.2% over all of the foils, source energies, and physics settings tested. This validation illuminated a deficiency in the computation of the underlying angular distributions that is well understood. As a result, code enhancements were made to stabilize the angular distributions in the presence of very small substeps. However, the enhancement only marginally improved results indicating that additional algorithmic details should be studied.

  16. [Linac based radiosurgery; a technical report].

    PubMed

    Hayashi, H; Asaga, A; Sakudoh, M; Hoshino, S; Katsuta, S; Akine, Y

    1992-07-01

    A method for highly dose-localized irradiation using a linear accelerator (linac) for a brain tumor has been developed. The method requires a linac, a computed tomography (CT) system, a CT simulator, and a treatment planning system for radiotherapy, with which most major radiotherapy centers are equipped. To immobilize a patient during irradiation, a custom-made device made of synthetic material which became flexible with heating was used. With the CT system and the CT simulator the target was identified and geometrical data for positioning the tumor at a point to which x-ray beams were directed (an isocenter of the linac) were obtained. By rotating a treatment couch it was made possible for the x-ray source to rotate around the isocenter on multiple planes. Dose distribution obtained with this method was compared to that of the gamma unit and found comparable. Since the method requires no invasive procedure, it appears suitable for treatment, with fractionated irradiation, of malignant tumors.

  17. High-quality Linac-based Stereotactic Body Radiation Therapy with Flattening Filter Free Beams and Volumetric Modulated Arc Therapy for Low-Intermediate Risk Prostate Cancer. A Mono-institutional Experience with 90 Patients.

    PubMed

    D'Agostino, G; Franzese, C; De Rose, F; Franceschini, D; Comito, T; Villa, E; Alongi, F; Liardo, R; Tomatis, S; Navarria, P; Mancosu, P; Reggiori, G; Cozzi, L; Scorsetti, M

    2016-12-01

    The aim of this phase II study was to evaluate the efficacy and toxicity of stereotactic body radiotherapy in patients with low or intermediate risk prostate cancer. Biopsy-confirmed prostate cancer patients were enrolled, provided that they had the following characteristics: initial prostate-specific antigen (PSA) ≤ 20 ng/ml, Gleason Score < 7, International Prostate Symptom Score < 7. The treatment schedule was 35 Gy in five fractions, delivered with volumetric modulated arcs with flattening filter free beams. Toxicity was recorded according to CTCAE criteria v4.0. Biochemical failure was calculated according to the Phoenix definition. The Expanded Prostate Cancer Index Composite questionnaire was used to record health-related quality of life. Between December 2011 and March 2015, 90 patients were enrolled (53 low risk, 37 intermediate risk). The median age was 71 years (range 48-82). In total, 58 (64.5%) of the patients had Gleason Score=6, the remaining had Gleason Score=7.The median initial PSA was 6.9 ng/ml (range 2.7-17.0). Acute toxicity was mild, with 32.2 patients presenting grade 1 urinary toxicity and 32.2% of patients presenting grade 2 urinary toxicity, mainly represented by urgency, dysuria and stranguria. Rectal grade 1 toxicity was found in 15.5% of patients, whereas grade 2 toxicity was recorded in 6.6% of patients. Regarding late toxicity, grade 1 proctitis was recorded in 11.1% of patients and grade 1 urinary in 38.8%; only two events of grade 2 urinary toxicity were observed (transient urethral stenosis, resolved by a 24 h catheterisation). At a median follow-up of 27 months (6-62 months) only two intermediate risk patients experienced a biochemical failure. Health-related quality of life revealed a slight worsening in all the domains during treatment, with a return to baseline 3 months after treatment. Stereotactic body radiotherapy delivered using linac-based flattening filter free volumetric modulated arc radiotherapy in low and

  18. Estimation of daily interfractional larynx residual setup error after isocentric alignment for head and neck radiotherapy: Quality-assurance implications for target volume and organ-at-risk margination using daily CT-on-rails imaging

    PubMed Central

    Baron, Charles A.; Awan, Musaddiq J.; Mohamed, Abdallah S. R.; Akel, Imad; Rosenthal, David I.; Gunn, G. Brandon; Garden, Adam S.; Dyer, Brandon A.; Court, Laurence; Sevak, Parag R; Kocak-Uzel, Esengul; Fuller, Clifton D.

    2016-01-01

    Larynx may alternatively serve as a target or organ-at-risk (OAR) in head and neck cancer (HNC) image-guided radiotherapy (IGRT). The objective of this study was to estimate IGRT parameters required for larynx positional error independent of isocentric alignment and suggest population–based compensatory margins. Ten HNC patients receiving radiotherapy (RT) with daily CT-on-rails imaging were assessed. Seven landmark points were placed on each daily scan. Taking the most superior anterior point of the C5 vertebra as a reference isocenter for each scan, residual displacement vectors to the other 6 points were calculated post-isocentric alignment. Subsequently, using the first scan as a reference, the magnitude of vector differences for all 6 points for all scans over the course of treatment were calculated. Residual systematic and random error, and the necessary compensatory CTV-to-PTV and OAR-to-PRV margins were calculated, using both observational cohort data and a bootstrap-resampled population estimator. The grand mean displacements for all anatomical points was 5.07mm, with mean systematic error of 1.1mm and mean random setup error of 2.63mm, while bootstrapped POIs grand mean displacement was 5.09mm, with mean systematic error of 1.23mm and mean random setup error of 2.61mm. Required margin for CTV-PTV expansion was 4.6mm for all cohort points, while the bootstrap estimator of the equivalent margin was 4.9mm. The calculated OAR-to-PRV expansion for the observed residual set-up error was 2.7mm, and bootstrap estimated expansion of 2.9mm. We conclude that the interfractional larynx setup error is a significant source of RT set-up/delivery error in HNC both when the larynx is considered as a CTV or OAR. We estimate the need for a uniform expansion of 5mm to compensate for set up error if the larynx is a target or 3mm if the larynx is an OAR when using a non-laryngeal bony isocenter. PMID:25679151

  19. Enigmatic electrons, photons, and ``empty`` waves

    SciTech Connect

    MacGregor, M.H.

    1995-08-22

    A spectroscopic analysis is made of electrons and photons from the standpoint of physical realism. In this conceptual framework, moving particles are portrayed as localized entities which are surrounded by ``empty`` waves. A spectroscopic model for the electron Stands as a guide for a somewhat similar, but in essential respects radically different, model for the photon. This leads in turn to a model for the ``zeron``. the quantum of the empty wave. The properties of these quanta mandate new basis states, and hence an extension of our customary framework for dealing with them. The zeron wave field of a photon differs in one important respect from the standard formalism for an electromagnetic wave. The vacuum state emerges as more than just a passive bystander. Its polarization properties provide wave stabilization, particle probability distributions, and orbit quantization. Questions with regard to special relativity are discussed.

  20. Advances in Linac-Based Technology for Industrial Radiation Processing

    NASA Astrophysics Data System (ADS)

    McKeown, Joseph

    1997-04-01

    Experience with the Industrial Materials Processing Electron Linear Accelerator, IMPELA, over 30,000 hours of 50 kW operation is reported for three irradiators, two of which are in commercial service. Operations are sufficiently mature that research is now concentrated on split beams, photon conversion, dose monitoring, beam scanning, new shielding designs and QA controls. The efficacy of increasing the incident electron energy on bremsstrahlung converters to 7.5 MeV, as proposed by an IAEA committee, is examined experimentally on an IMPELA accelerator over the energy range 7 MeV to 11 MeV to evaluate conversion efficiency, activation of machine components, converter engineering and the activation of red meat. Above 8 MeV the radioactive isotopes ^38Cl and ^24Na, formed primarily by neutrons produced in a tantalum converter, were clearly identified in the meat, while above 10.5 MeV the radiation from ^13N becomes dominant. Implications for the practicality of processing other high density products are discussed.

  1. Development of collimator insert for linac based stereotactic irradiation.

    PubMed

    Singh, I R; Brindha, S; Ravindran, B P; John, S; Rajshekhar, V; Rangad, F V; Roul, R K

    1999-10-01

    The aim of this study is to develop collimator inserts of various sizes which are either not commercially available or are expensive to import. The dosimetry parameters such as tissue maximum ratio (TMR), off-axis ratio (OAR) and output factor of the developed collimator insert are compared with that of the commercial collimator insert (Radionics). In order to check the suitability of the collimator insert developed locally for clinical use and to standardize the method of development, a collimator insert of 15 mm identical to the one supplied by Radionics is developed with low-melting alloy (Cerrobend). Moreover for the clinical use of the developed collimator insert, certain acceptance tests are performed which include a collimator concentricity test, beam size check and radiation leakage test. The dose verification is carried out with a thermoluminescent dosimeter (7LiF rods) and an FBX chemical dosimeter in a human-head-shaped Perspex phantom filled with water. The variation between the calculated and measured dose is found to be within +2.4% for 7LiF rods and -2.0% for the FBX chemical dosimeter thus ensuring the suitability of the developed collimator insert for clinical use. This has encouraged us to standardize the method adapted to develop the collimator insert and to develop collimator inserts of different field sizes.

  2. FLUTE: A versatile linac-based THz source

    SciTech Connect

    Nasse, M. J.; Schuh, M.; Schwarz, M.; Naknaimueang, S.; Mathis, Y.-L.; Rossmanith, R.; Wesolowski, P.; Huttel, E.; Plech, A.; Schmelling, M.; Mueller, A.-S.

    2013-02-15

    A new compact versatile linear accelerator named FLUTE is currently being designed at the Karlsruhe Institute of Technology. This paper presents the status of this 42 MeV machine. It will be used to generate strong (several 100 MV/m) ultra-short ({approx}1 ps) THz pulses (up to {approx}4-25 THz) for photon science experiments, as well as to conduct a variety of accelerator studies. The latter range from comparing different coherent THz radiation generation schemes to compressing electron bunches and studying the electron beam stability. The bunch charge will cover a wide range ({approx}100 pC-3 nC). Later we plan to also produce ultra-short x-ray pulses from the electron bunches, which, for example, could then be combined for THz pump-x-ray probe experiments.

  3. FLUTE: a versatile linac-based THz source.

    PubMed

    Nasse, M J; Schuh, M; Naknaimueang, S; Schwarz, M; Plech, A; Mathis, Y-L; Rossmanith, R; Wesolowski, P; Huttel, E; Schmelling, M; Müller, A-S

    2013-02-01

    A new compact versatile linear accelerator named FLUTE is currently being designed at the Karlsruhe Institute of Technology. This paper presents the status of this 42 MeV machine. It will be used to generate strong (several 100 MV/m) ultra-short (~1 ps) THz pulses (up to ~4-25 THz) for photon science experiments, as well as to conduct a variety of accelerator studies. The latter range from comparing different coherent THz radiation generation schemes to compressing electron bunches and studying the electron beam stability. The bunch charge will cover a wide range (~100 pC-3 nC). Later we plan to also produce ultra-short x-ray pulses from the electron bunches, which, for example, could then be combined for THz pump-x-ray probe experiments.

  4. Linac-Based Photonuclear Applications at the Idaho Accelerator Center

    NASA Astrophysics Data System (ADS)

    Mamtimin, Mayir; Starovoitova, Valeriia N.; Harmon, Frank

    2014-02-01

    In this paper, current Idaho Accelerator Center (IAC) activities based on the exploitation of high energy bremsstrahlung photons generated by linear electron accelerators will be reviewed. These beams are used to induce photonuclear interactions for a wide variety of applications in materials science, activation analysis, medical research, and nuclear technology. Most of the exploited phenomena are governed by the familiar giant dipole resonance cross section in nuclei. By proper target and converter design, optimization of photon and photoneutron production can be achieved, allowing radiation fields produced with both photons and neutrons to be used for medical isotope production and for fission product transmutation. The latter provides a specific application example that supports long-term fission product waste management. Using high-energy, highpower electron accelerators, we can demonstrate transmutation of radio-toxic, long-lived fission products (LLFP) such as 99Tc and 129I into short lived species. The latest experimental and simulation results will be presented.

  5. Verification procedure for isocentric alignment of proton beams.

    PubMed

    Ciangaru, George; Yang, James N; Oliver, Patrick J; Bues, Martin; Zhu, Mengping; Nakagawa, Fumio; Chiba, Hitoshi; Nakamura, Shin; Yoshino, Hirofumi; Umezawa, Mosumi; Smith, Alfred R

    2007-10-24

    We present a technique--based on the Lutz, Winston, and Maleki test used in stereotactic linear accelerator radiosurgery--for verifying whether proton beams are being delivered within the required spatial coincidence with the gantry mechanical isocenter. Our procedure uses a proton beam that is collimated by a circular aperture at its central axis and is then intercepted by a small steel sphere rigidly supported by the patient couch. A laser tracker measurement system and a correction algorithm for couch position assures precise positioning of the steel sphere at the mechanical isocenter of the gantry. A film-based radiation dosimetry technique, chosen for the good spatial resolution it achieves, records the proton dose distribution for optical image analysis. The optical image obtained presents a circular high-dose region surrounding a lower-dose area corresponding to the proton beam absorption by the steel sphere, thereby providing a measure of the beam alignment with the mechanical isocenter. We found the self-developing Gafchromic EBT film (International Specialty Products, Wayne, NJ) and commercial Epson 10000 XL flatbed scanner (Epson America, Long Beach, CA) to be accurate and efficient tools. The positions of the gantry mechanical and proton beam isocenters, as recorded on film, were clearly identifiable within the scanning resolution used for routine alignment testing (0.17 mm per pixel). The mean displacement of the collimated proton beam from the gantry mechanical isocenter was 0.22 +/- 0.1 mm for the gantry positions tested, which was well within the maximum deviation of 0.50 mm accepted at the Proton Therapy Center in Houston.

  6. Electron, photons, and molecules: Storing energy from light

    SciTech Connect

    Miller, J.R.

    1996-09-01

    Molecular charge separation has important potential for photochemical energy storage. Its efficiency can be enhanced by principals which maximize the rates of the electron transfer steps which separate charge and minimize those which recombine high-energy charge pairs to lose stored energy. Dramatic scientific progress in understanding these principals has occurred since the founding of DOE and its predecessor agency ERDA. While additional knowledge in needed in broad areas of molecular electron transfer, some key areas of knowledge hold particular promise for the possibility of moving this area from science toward technology capable of contributing to the nation`s energy economy.

  7. MEMS-Electronic-Photonic Heterogeneous Integrated FMCW Ladar Source

    DTIC Science & Technology

    2015-12-18

    integrated   circuits ,  and  CMOS  ICs  in  a  seamless  manner,  and...M5.   At   each   moment   the   integrator  can  be  modeled  with  the  equivalent   circuit  on  the  right  side...Phase  2  –  Quarterly  Report     Figure  15:   Circuit  diagram  of  the   integrator .   In  order

  8. Electron-photon coupling in mesoscopic quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Cottet, A.; Kontos, T.; Douçot, B.

    2015-05-01

    Understanding the interaction between cavity photons and electronic nanocircuits is crucial for the development of mesoscopic quantum electrodynamics (QED). One has to combine ingredients from atomic cavity QED, such as orbital degrees of freedom, with tunneling physics and strong cavity field inhomogeneities, specific to superconducting circuit QED. It is therefore necessary to introduce a formalism which bridges between these two domains. We develop a general method based on a photonic pseudopotential to describe the electric coupling between electrons in a nanocircuit and cavity photons. In this picture, photons can induce simultaneously orbital energy shifts, tunneling, and local orbital transitions. We study in detail the elementary example of a single quantum dot with a single normal metal reservoir, coupled to a cavity. Photon-induced tunneling terms lead to a nonuniversal relation between the cavity frequency pull and the damping pull. Our formalism can also be applied to multiple quantum dot circuits, molecular circuits, quantum point contacts, metallic tunnel junctions, and superconducting nanostructures enclosing Andreev bound states or Majorana bound states, for instance.

  9. Wide Bandgap Semiconductor Nanowires for Electronic, Photonic and Sensing Devices

    DTIC Science & Technology

    2012-01-05

    variety of wide bandgap nanowires using GaN and ZnO and made functional devices from them for sensing,electronics and photonics.These included a very...showed highly stable operation.This effort grew out of the work on ZnO nanowires ,where we noticed severe segregation effects when we tried to grow...AND ADDRESSES U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS GaN, ZnO , nanowires S.Pearton

  10. Transition radiation and coherent electron-photon scattering

    SciTech Connect

    Moran, M.J.

    1985-04-01

    Relativistic electron irradiation of thin solid targets is known to generate collimated beams of x-ray photons in the forward direction by a number of different processes. A variety of mechanisms are discussed that share common characteristics in the angular and spectral distributions of the generated photon beams. Some simple physical explanations are offered for the characteristics shared by these processes. Some examples are then given based on experimental results attained at the LLNL electron-positron accelerator. (LEW)

  11. Two-arm electron/photon spectrometer collaboration

    SciTech Connect

    Hayano, R.S.; Sakurai, H. ); Akiba, Y.; Hamagaki, H.; Tanaka, Y. . Inst. for Nuclear Study); Chiba, J. ); En'yo, H. ); Sano, H. ); Sugitate, T. ); Hayashi, S.; Tanaka, M.; Tannenbaum, M.J. ); Roc

    1990-01-01

    The main focus of this working group was to design a detector system which is capable of measuring soft low-mass e{sup +}e{sup {minus}} pair (M{sub e+}e{sub {minus}}) production from {approximately}4 GeV/c{sup 2} down to a few hundred MeV/c{sup 2} in the central rapidity region, together with associated hadron charged multiplicity and transverse neutral energy of the event. The soft dilepton production in this mass range and direct photon production are expected to be a sensitive penetrating probe to study the properties of the high energy density matter (hot hadron gas, mixed phase, and QGP) created in the heavy-ion collisions at RHIC. The measurement of low-mass e{sup +}e{sup {minus}} pair production with low p{sub T}, is a nontrivial task due to the overwhelmingly large combinatorial background from {pi}{sup 0} and {eta} Dalitz decays. The key to the successful measurement of the low-mass continuum is to effectively reject Dalitz-decay pairs. This requires an identification of e{sup +}e{sup {minus}} pairs with relatively small ({theta} < 10{degree}) opening angles before they enter a magnetic volume. The detector system we studied during the workshop is described. It has two identical arms on both sides of the beam pipe (each covering {minus}0.2 < {eta} < 0.2, {minus}20{degree} < {phi} < 45{degree}), has a gas ring-imaging Cerenkov (RICH) counter on each arm. The RICH counters are placed close to the beam pipe, in a field-free region, and are used to identify electrons and to reject small-region e{sup +}e{sup {minus}} pairs.

  12. LDRD project 151362 : low energy electron-photon transport.

    SciTech Connect

    Kensek, Ronald Patrick; Hjalmarson, Harold Paul; Magyar, Rudolph J.; Bondi, Robert James; Crawford, Martin James

    2013-09-01

    At sufficiently high energies, the wavelengths of electrons and photons are short enough to only interact with one atom at time, leading to the popular %E2%80%9Cindependent-atom approximation%E2%80%9D. We attempted to incorporate atomic structure in the generation of cross sections (which embody the modeled physics) to improve transport at lower energies. We document our successes and failures. This was a three-year LDRD project. The core team consisted of a radiation-transport expert, a solid-state physicist, and two DFT experts.

  13. Comparative analyses of linac and Gamma Knife radiosurgery for trigeminal neuralgia treatments

    NASA Astrophysics Data System (ADS)

    Ma, L.; Kwok, Y.; Chin, L. S.; Yu, C.; Regine, W. F.

    2005-11-01

    Dedicated linac-based radiosurgery has been reported for trigeminal neuralgia treatments. In this study, we investigated the dose fall-off characteristics and setup error tolerance of linac-based radiosurgery as compared with standard Gamma Knife radiosurgery. In order to minimize the errors from different treatment planning calculations, consistent imaging registration, dose calculation and dose volume analysis methods were developed and implemented for both Gamma Knife and linac-based treatments. Intra-arc setup errors were incorporated into the treatment planning process of linac-based deliveries. The effects of intra-arc setup errors with increasing number of arcs were studied and benchmarked against Gamma Knife deliveries with and without plugging patterns. Our studies found equivalent dose fall-off properties between Gamma Knife and linac-based radiosurgery given a sufficient number of arcs (>7) and small intra-arc errors (<0.5 mm) were satisfied for linac-based deliveries. Increasing the number of arcs significantly decreased the variations in the dose fall-off curve at the low isodose region (e.g. from 40% to 10%) and also improved dose uniformity at the high isodose region (e.g. from 70% to 90%). As the number of arcs increased, the effects of intra-arc setup errors on the dose fall-off curves decreased. Increasing the number of arcs also reduced the integral dose to the distal normal brain tissues. In conclusion, linac-based radiosurgery produces equivalent dose fall-off characteristics to Gamma Knife radiosurgery with a high number of arcs. However, one must note the increased treatment time for a large number of arcs and isocentre accuracies.

  14. LUX - A recirculating linac-based ultrafast X-ray source

    SciTech Connect

    Corlett, J.N.; Barletta, W.A.; DeSantis, S.; Doolittle, L.; Fawley, W.M.; Green, M.A.; Heimann, P.; Leone, S.R.; Lidia, S.; Li, D.; Parmigiani, F.; Ratti, A.; Robinson, K.; Schoenlein, R.; Staples, J.; Wan, W.; Wells, R.; Wilcox, R.; Wolski, A.; Zholents, A.

    2003-08-01

    We describe the design of a proposed source of ultra-fast synchrotron radiation x-ray pulses based on a recirculating superconducting linac, with an integrated array of ultrafast laser systems. The source produces x-ray pulses with duration of 10-50 fs at a 10 kHz repetition rate, with tunability from EUV to hard x-ray regimes, and optimized for the study of ultra-fast dynamics. A high-brightness rf photocathode provides electron bunches. An injector linac accelerates the beam to the 100 MeV range, and is followed by four passes through a 700 MeV recirculating linac. Ultrafast hard x-ray pulses are obtained by a combination of electron bunch manipulation, transverse temporal correlation of the electrons, and x-ray pulse compression. EUV and soft x-ray pulses as short as 10 fs are generated in a harmonic-cascade free electron laser scheme.

  15. Conformity of LINAC-Based Stereotactic Radiosurgery Using Dynamic Conformal Arcs and Micro-Multileaf Collimator

    SciTech Connect

    Hazard, Lisa J. Wang, Brian; Skidmore, Thomas B.; Chern, Shyh-Shi; Salter, Bill J.; Jensen, Randy L.; Shrieve, Dennis C.

    2009-02-01

    Purpose: To assess the conformity of dynamic conformal arc linear accelerator-based stereotactic radiosurgery and to describe a standardized method of isodose surface (IDS) selection. Methods and Materials: In 174 targets, the conformity index (CI) at the prescription IDS used for treatment was calculated as CI = (PIV/PVTV)/(PVTV/TV), where TV is the target volume, PIV (prescription isodose volume) is the total volume encompassed by the prescription IDS, and PVTV is the TV encompassed by the IDS. In addition, a 'standardized' prescription IDS (sIDS) was chosen according to the following criteria: 95% of the TV was encompassed by the PIV and 99% of TV was covered by 95% of the prescription dose. The CIs at the sIDS were also calculated. Results: The median CI at the prescription IDS and sIDS was 1.63 and 1.47, respectively (p < 0.001). In 132 of 174 cases, the volume of normal tissue in the PIV was reduced by the prescription to the sIDS compared with the prescription IDS, in 20 cases it remained unchanged, and in 22 cases it was increased. Conclusion: The CIs obtained with linear accelerator-based stereotactic radiosurgery are comparable to those previously reported for gamma knife stereotactic radiosurgery. Using a uniform method to select the sIDS, adequate target coverage was usually achievable with prescription to an IDS greater than that chosen by the treating physician (prescription IDS), providing sparing of normal tissue. Thus, the sIDS might aid physicians in identifying a prescription IDS that balances coverage and conformity.

  16. LINAC based radiosurgery and radiotherapy for neurosurgical diseases: what have we learnt so far.

    PubMed

    Zamzuri, I; Badrisyah, I; Rahman, G I; Pal, H K; Muzaimi, M; Jafri, A M; War, M; Shafie, A M; Ruzman, N I Nik; Biswal, B M; Ahmad, Z

    2011-10-01

    Stereotactic radiosurgery uses a single fraction high dose radiation while stereotactic radiotherapy uses multifractionated lower dose focused radiation. Radiosurgery used rigid CRW head frame while stereotactic radiotherapy utilized GTC or HNL relocatable frames. Stereotactic planning and radiation involved Radionics X-plan and LINAC system. Since December 2001, we have treated 83 lesions from 77 patients using either radiosurgery or fractionated stereotactic radiotherapy. Eighty six percent (86%) of our treated lesions showed favourable outcomes with median follow-up of 32 months (0-7 years). Our lessons from LINAC precision radiation therapy uphold its value as a promising and effective tool in treating a range of nervous system pathologies.

  17. Gamma Knife and LINAC-Based Stereotactic Treatments of Intracranial Targets: Dosimetric and Radiobiological Considerations

    NASA Astrophysics Data System (ADS)

    Kendall, Ethan Lee

    The scientific community is interested in furthering the understanding of shock wave structures in water, given its implications in a wide range of applications; from researching how shock waves penetrate unwanted body tissues to studying how humans respond to blast waves. Shock wave research on water has existed for over five decades. Previous studies have investigated the shock response of water at pressures ranging from 1 to 70 GPa using flyer plate experiments. This report differs from previously published experiments in that the water was loaded to shock pressures ranging from 0.36 to 0.70 GPa. The experiment also utilized tap water rather than distilled water as the test sample. Flyer plate experiments were conducted in the Shock Physics Laboratory at Marquette University to determine the structure of shock waves within water. A 12.7 mm bore gas gun fired a projectile made of copper, PMMA, or aluminum at a stationary target filled with tap water. Graphite break pins in a circuit determined the initial projectile velocity prior to coming into contact with the target. A Piezoelectric timing pin (PZT pin) at the front surface of the water sample determined the arrival of the leading wave and a Photon Doppler Velocimeter (PDV) measured particle velocity from the rear surface of the water sample. The experimental results were compared to simulated data from a Eulerian Hydrocode called CTH [1]. The experimental results differed from the simulated results with deviations believed to be from experimental equipment malfunctions. The main hypothesis being that the PZT pin false triggered, resulting in measured lower than expected shock velocities. The simulated results were compared to published data from various authors and was within range.

  18. High Repetition Rate, LINAC-based Nuclear Resonance Fluorescence FY 2009 Final Report

    SciTech Connect

    Mathew Kinlaw; Scott Watson; James Johnson; Alan Hunt; Heather Seipel; Edward Reedy

    2009-10-01

    Nuclear Resonance Fluorescence (NRF), which is possible for nuclei with atomic numbers greater than helium (Z=2), occurs when a nuclear level is excited by resonant absorption of a photon and subsequently decays by reemission of a photon. The excited nuclear states can become readily populated, provided the incident photon’s energy is within the Doppler-broadened width of the energy level being excited. Utilizing continuous energy photon spectra, as is characteristic of a bremsstrahlung photon beam, as the inspection source, ensures that at least some fraction of the impinging beam will contribute to the population of the excited energy levels in the material of interest. Upon de-excitation, either to the ground state or to a lower-energy excited state, the emitted fluorescence photon’s energy will correspond to the energy difference between the excited state and the state to which it decays. As each isotope inherently contains unique nuclear energy levels, the NRF states for each isotope are also unique. By exploiting this phenomenon, NRF photon detection provides a well-defined signature for identifying the presence of individual nuclear species. This report summarizes the second year (Fiscal Year [FY] 2009) of a collaborative research effort between Idaho National Laboratory, Idaho State University’s Idaho Accelerator Center, and Pacific Northwest National Laboratory. This effort focused on continuing to assess and optimize NRF-based detection techniques utilizing a slightly modified, commercially available, pulsed medical electron accelerator.

  19. Evaluation of a commercial MRI Linac based Monte Carlo dose calculation algorithm with GEANT 4

    SciTech Connect

    Ahmad, Syed Bilal; Sarfehnia, Arman; Kim, Anthony; Sahgal, Arjun; Keller, Brian; Paudel, Moti Raj; Hissoiny, Sami

    2016-02-15

    Purpose: This paper provides a comparison between a fast, commercial, in-patient Monte Carlo dose calculation algorithm (GPUMCD) and GEANT4. It also evaluates the dosimetric impact of the application of an external 1.5 T magnetic field. Methods: A stand-alone version of the Elekta™ GPUMCD algorithm, to be used within the Monaco treatment planning system to model dose for the Elekta™ magnetic resonance imaging (MRI) Linac, was compared against GEANT4 (v10.1). This was done in the presence or absence of a 1.5 T static magnetic field directed orthogonally to the radiation beam axis. Phantoms with material compositions of water, ICRU lung, ICRU compact-bone, and titanium were used for this purpose. Beams with 2 MeV monoenergetic photons as well as a 7 MV histogrammed spectrum representing the MRI Linac spectrum were emitted from a point source using a nominal source-to-surface distance of 142.5 cm. Field sizes ranged from 1.5 × 1.5 to 10 × 10 cm{sup 2}. Dose scoring was performed using a 3D grid comprising 1 mm{sup 3} voxels. The production thresholds were equivalent for both codes. Results were analyzed based upon a voxel by voxel dose difference between the two codes and also using a volumetric gamma analysis. Results: Comparisons were drawn from central axis depth doses, cross beam profiles, and isodose contours. Both in the presence and absence of a 1.5 T static magnetic field the relative differences in doses scored along the beam central axis were less than 1% for the homogeneous water phantom and all results matched within a maximum of ±2% for heterogeneous phantoms. Volumetric gamma analysis indicated that more than 99% of the examined volume passed gamma criteria of 2%—2 mm (dose difference and distance to agreement, respectively). These criteria were chosen because the minimum primary statistical uncertainty in dose scoring voxels was 0.5%. The presence of the magnetic field affects the dose at the interface depending upon the density of the material on either sides of the interface. This effect varies with the field size. For example, at the water-lung interface a 33.94% increase in dose was observed (relative to the D{sub max}), by both GPUMCD and GEANT4 for the field size of 2 × 2 cm{sup 2} (compared to no B-field case), which increased to 47.83% for the field size of 5 × 5 cm{sup 2} in the presence of the magnetic field. Similarly, at the lung-water interface, the dose decreased by 19.21% (relative to D{sub max}) for a field size of 2 × 2 cm{sup 2} and by 30.01% for 5 × 5 cm{sup 2} field size. For more complex combinations of materials the dose deposition also becomes more complex. Conclusions: The GPUMCD algorithm showed good agreement against GEANT4 both in the presence and absence of a 1.5 T external magnetic field. The application of 1.5 T magnetic field significantly alters the dose at the interfaces by either increasing or decreasing the dose depending upon the density of the material on either side of the interfaces.

  20. Isocenter verification for linac-based stereotactic radiation therapy: review of principles and techniques.

    PubMed

    Rowshanfarzad, Pejman; Sabet, Mahsheed; O'Connor, Daryl J; Greer, Peter B

    2011-11-15

    There have been several manual, semi-automatic and fully-automatic methods proposed for verification of the position of mechanical isocenter as part of comprehensive quality assurance programs required for linear accelerator-based stereotactic radiosurgery/radiotherapy (SRS/SRT) treatments. In this paper, a systematic review has been carried out to discuss the present methods for isocenter verification and compare their characteristics, to help physicists in making a decision on selection of their quality assurance routine.

  1. Feasibility study for a recirculating linac-based facility for femtosecond dynamics

    SciTech Connect

    Corlett, J.N.; Barry, W.; Barletta, W.A.; Byrd, J.M.; DeSantis, S.; Doolittle, L.; Fawley, W.; Green, M.A.; Hartman, N.; Heimann, P.; Kairan, D.; Kujawski, E.; Li, D.; Lidia, S.; Luft, P.; McClure, R.; Parmigiani, F.; Petroff, Y.; Pirkl, W.; Placidi, M.; Reavill, D.; Reichel, I.; Rimmer, R.A.; Ratti, A.; Robinson, K.E.; Sannibale, F.; Schoenlein, R.; Staples, J.; Tanabe, J.; Truchlikova, D.; Wan, W.; Wang, S.; Wells, R.; Wolski, A.; Zholents, A.

    2002-12-21

    LBNL is pursuing design studies and the scientific program for a facility dedicated to the production of x-ray pulses with ultra-short time duration, for application in dynamical studies of processes in physics, biology, and chemistry. The proposed x-ray facility has the short x-ray pulse length ({approx}60 fs FWHM) necessary to study very fast dynamics, high flux (up to approximately 10E11 photons/sec/0.1 percentBW) to study weakly scattering systems, and tuneability over 1-12 keV photon energy. The hard x-ray photon production section of the machine accommodates seven 2-m long undulators. Design studies for longer wavelength sources, using high-gain harmonic generation, are in progress. The x-ray pulse repetition rate of 10 kHz is matched to studies of dynamical processes (initiated by ultra-short laser pulses) that typically have a long recovery time or are not generally cyclic or reversible and need time to allow relaxation, replacement, or flow of the sample. The technique for producing ultra-short x-ray pulses uses relatively long electron bunches to minimize high-peak-current collective effects, and the ultimate x-ray duration is achieved by a combination of bunch manipulation and optical compression. Synchronization of x-ray pulses to sample excitation signals is expected to be of order 50 - 100 fs. Techniques for making use of the recirculating geometry to provide beam-based signals from early passes through the machine are being studied.

  2. LUX — A Recirculating Linac-based Ultrafast X-ray Source

    NASA Astrophysics Data System (ADS)

    Corlett, J. N.; Barletta, W. A.; DeSantis, S.; Doolittle, L.; Fawley, W. M.; Green, M. A.; Heimann, P.; Leone, S. R.; Lidia, S.; Li, D.; Parmigiani, F.; Ratti, A.; Robinson, K.; Schoenlein, R.; Staples, J.; Wan, W.; Wells, R.; Wilcox, R.; Wolski, A.; Zholents, A.

    2004-05-01

    We describe the design of a proposed source of ultra-fast synchrotron radiation x-ray pulses based on a recirculating superconducting linac, with an integrated array of ultrafast laser systems. The source produces x-ray pulses with duration of 10-50 fs at a 10 kHz repetition rate, with tunability from EUV to hard x-ray regimes, and optimized for the study of ultra-fast dynamics. A high-brightness rf photocathode provides electron bunches. An injector linac accelerates the beam to the 100 MeV range, and is followed by four passes through a 700 MeV recirculating linac. Ultrafast hard x-ray pulses are obtained by a combination of electron bunch manipulation, transverse temporal correlation of the electrons, and x-ray pulse compression. EUV and soft x-ray pulses as short as 10 fs are generated in a harmonic-cascade free electron laser scheme. We describe the facility major systems and peformance.

  3. LUX - a recirculating linac-based facility for ultrafast X-ray science

    SciTech Connect

    Corlett, J.N.; Barletta, W.A.; DeSantis, S.; Doolittle, L.; Fawley, W.M.; Heimann, P.; Leone, S.; Lidia, S.; Li, D.; Penn, G.; Ratti, A.; Reinsch, M.; Schoenlein, R.; Staples, J.; Stover, G.; Virostek, S.; Wan, W.; Wells, R.; Wilcox, R.; Wolski, A.; Wurtele, J.; Zholents, A.

    2004-06-29

    We present recent developments in design concepts for LUX - a source of ultra-short synchrotron radiation pulses based on a recirculating superconducting linac. The source produces high-flux x-ray pulses with duration of 100 fs or less at a 10 kHz repetition rate, optimized for the study of ultra-fast dynamics across many fields of science [1]. Cascaded harmonic generation in free-electron lasers (FEL's) produces coherent radiation in the VUV-soft x-ray regime, and a specialized technique is used to compress spontaneous emission for ultra-short-pulse photon production in the 1-10 keV range. High-brightness electron bunches of 2-3 mm-mrad emittance at 1 nC charge in 30 ps duration are produced in an rf photocathode gun and compressed to 3 ps duration following an injector linac, and recirculated three times through a 1 GeV main linac. In each return path, independently tunable harmonic cascades are inserted to produce seeded FEL radiation in selected photon energy ranges from approximately 20 eV with a single stage of harmonic generation, to 1 keV with a four-stage cascade. The lattice is designed to minimize emittance growth from effects such as coherent synchrotron radiation (CSR), and resistive wall wakefields. Timing jitter between pump lasers and x-ray pulses is minimized by use of a stable optical master oscillator, distributing timing signals over actively stabilized fiber-optic, phase-locking all lasers to the master oscillator, and generating all rf signals from the master oscillator. We describe technical developments including techniques for minimizing power dissipation in a high repetition rate rf photocathode gun, beam dynamics in two injector configurations, independently tunable beamlines for VUV and soft x-ray production by cascaded harmonic generation, a fast kicker design, timing systems for providing synchronization between experimental pump lasers and the x-ray pulse, and beamline design for maintaining nm-scale density modulation.

  4. Optimal focusing for a linac-based hard x-ray source

    SciTech Connect

    Liu, C.; Krafft, G.; Talman, R.

    2011-03-28

    In spite of having a small average beam current limit, a linac can have features that make it attractive as an x-ray source: high energy, ultralow emittance and energy spread, and flexible beamline optics. Unlike a storage ring, in which an (undulator) radiation source is necessarily short and positioned at an electron beam waist, in a linac the undulator can be long and the electron beam can be adjusted to have a (virtual) waist far downstream toward the x-ray target. Using a planned CEBAF beamline as an example, this paper shows that a factor of 2000 in beam current can be overcome to produce a monochromatic hard x-ray source comparable with, or even exceeding, the performance of an x-ray line at a third generation storage ring. Optimal electron beam focusing conditions for x-ray flux density and brilliance are derived, and are verified by simulations using the SRW code.

  5. Dose-volume histogram quality assurance for linac-based treatment planning systems

    PubMed Central

    Gossman, Michael S.; Bank, Morris I.

    2010-01-01

    Dose–volume histograms provide key information to radiation oncologists when they assess the adequacy of a patient treatment plan in radiation therapy. It is important therefore that all clinically relevant data be accurate. In this article we present the first quality assurance routine involving a direct comparison of planning system results with the results obtained from independent hand calculations. Given a known three-dimensional (3-D) structure such as a parallelepiped, a simple beam arrangement, and known physics beam data, a time-efficient and reproducible method for verifying the accuracy of volumetric statistics (DVH) from a radiation therapy treatment planning system (TPS) can be employed rapidly, satisfying the QA requirements for (TPS) commissioning, upgrades, and annual checks. Using this method, the maximum disagreement was only 1.7% for 6 MV and 1.3% for 18 MV photon energies. The average accuracy was within 0.6% for 6 MV and 0.4% for 18 MV for all depth-dose results. A 2% disagreement was observed with the treatment planning system DVH from defined volume comparison to the known structure dimensions. PMID:21170183

  6. SU-E-T-536: LINAC-Based Single Isocenter Frameless SRT for Brain Metastases

    SciTech Connect

    Liu, B; Zhang, L; Rigor, N; Kim, J

    2015-06-15

    Purpose: Single-isocenter Stereotactic Radiotherapy of multiple brain metastases with Varian 21 IX LINAC, using Aktina Pinpoint system for patient setup. Methods: In 2014, five single-isocenter RapidArc SRT plans were delivered to five patients with 2 to 8 brain metastases using Varian 21 IX. Aktina Pinpoint system was used for setup and 2mm PTV margin were used. CBCT was acquired before and after the beam delivery. The prescription is 2100 cGy in 3 fractions. Eclipse planning system was used for treatment planning. Depending on the number of metastases and their locations, 1 to 5 coplanar or non coplanar arcs were used. Typically, 2 or 3 arcs are used. IMRT QAs were performed by comparing an A1SL ion chamber point dose measurement in solid water phantom to point dose of the plan; also, based on EPID measurement, 3D spatial dose was calculated using DosimetryCheck software package from MathResolutions Inc. The EPID system has an active area of 40cm by 30cm with 1024 by 768 photodiodes, which corresponds to a resolution of 0.4mm by 0.4mm pixel dimension. Results: for all the plans, at least 95% PTV coverage was achieved for full prescription dose, with plan normalization > 75%. RTOG conformity indices are less than 1.1 and Paddick gradient indices are less than 4.5. The distance from prescription IDL to 50% IDL increases as the number of metastases increases, and it ranges from 0.6mm to 0.8mm. Treatment time varies from 10mins to 30mins, depending on the number of arcs and if the arcs are coplanar. IMRT QA shows that the ion chamber measurement agree with the eclipse calculation within 3%, and 95% of the points passed Gamma, using 3% dose difference and 3mm DTA Conclusion: High quality single isocenter RapidArc SRT plan can be optimized and accurately delivered using Eclipse and Varian 21IX.

  7. LINAC- Based radiosurgery for melanoma, sarcoma and renal cell carcinoma brain metastases.

    PubMed

    Maranzano, Ernesto; Casale, Michelina; Rispoli, Rossella; Trippa, Fabio; Draghini, Lorena; Arcidiacono, Fabio; Carletti, Sandro; Anselmo, Paola

    2016-09-07

    To report response, overall survival (OS) and toxicity in patients with radioresistant brain metastases (BM) treated with radiosurgery (SRS). Patients with renal cell carcinoma, melanoma and sarcoma with one to four brain metastases received SRS without whole brain radiotherapy. 50 patients with 77 BM were treated. 46 (92%) patients with 71 BM were evaluable. Median follow-up was 67 months and median OS 11.8 months. At the time of analysis all patients had died. Brain control was conditioned by response to SRS (P<0.0001), while OS by histology (renal cell carcinoma versus melanoma and sarcoma) (P=0.04) and status of the tumour outside the brain (P=0.05). Treatment was well tolerated without more than grade 2 acute toxicity. Treatment of BM from radioresistant tumors with SRS assures good brain control and OS with low toxicity. Our data suggest a better prognosis associated to renal cell carcinoma histology.

  8. Evaluation of a commercial MRI Linac based Monte Carlo dose calculation algorithm with GEANT4.

    PubMed

    Ahmad, Syed Bilal; Sarfehnia, Arman; Paudel, Moti Raj; Kim, Anthony; Hissoiny, Sami; Sahgal, Arjun; Keller, Brian

    2016-02-01

    This paper provides a comparison between a fast, commercial, in-patient Monte Carlo dose calculation algorithm (GPUMCD) and geant4. It also evaluates the dosimetric impact of the application of an external 1.5 T magnetic field. A stand-alone version of the Elekta™ GPUMCD algorithm, to be used within the Monaco treatment planning system to model dose for the Elekta™ magnetic resonance imaging (MRI) Linac, was compared against GEANT4 (v10.1). This was done in the presence or absence of a 1.5 T static magnetic field directed orthogonally to the radiation beam axis. Phantoms with material compositions of water, ICRU lung, ICRU compact-bone, and titanium were used for this purpose. Beams with 2 MeV monoenergetic photons as well as a 7 MV histogrammed spectrum representing the MRI Linac spectrum were emitted from a point source using a nominal source-to-surface distance of 142.5 cm. Field sizes ranged from 1.5 × 1.5 to 10 × 10 cm(2). Dose scoring was performed using a 3D grid comprising 1 mm(3) voxels. The production thresholds were equivalent for both codes. Results were analyzed based upon a voxel by voxel dose difference between the two codes and also using a volumetric gamma analysis. Comparisons were drawn from central axis depth doses, cross beam profiles, and isodose contours. Both in the presence and absence of a 1.5 T static magnetic field the relative differences in doses scored along the beam central axis were less than 1% for the homogeneous water phantom and all results matched within a maximum of ±2% for heterogeneous phantoms. Volumetric gamma analysis indicated that more than 99% of the examined volume passed gamma criteria of 2%-2 mm (dose difference and distance to agreement, respectively). These criteria were chosen because the minimum primary statistical uncertainty in dose scoring voxels was 0.5%. The presence of the magnetic field affects the dose at the interface depending upon the density of the material on either sides of the interface. This effect varies with the field size. For example, at the water-lung interface a 33.94% increase in dose was observed (relative to the Dmax), by both GPUMCD and GEANT4 for the field size of 2 × 2 cm(2) (compared to no B-field case), which increased to 47.83% for the field size of 5 × 5 cm(2) in the presence of the magnetic field. Similarly, at the lung-water interface, the dose decreased by 19.21% (relative to Dmax) for a field size of 2 × 2 cm(2) and by 30.01% for 5 × 5 cm(2) field size. For more complex combinations of materials the dose deposition also becomes more complex. The GPUMCD algorithm showed good agreement against GEANT4 both in the presence and absence of a 1.5 T external magnetic field. The application of 1.5 T magnetic field significantly alters the dose at the interfaces by either increasing or decreasing the dose depending upon the density of the material on either side of the interfaces.

  9. Investigation of Linac-Based Image-Guided Hypofractionated Prostate Radiotherapy

    SciTech Connect

    Pawlicki, Todd . E-mail: tpaw@stanford.edu; Kim, Gwe-Ya; Hsu, Annie; Cotrutz, Cristian; Boyer, Arthur L.; Xing Lei; King, Christopher R.; Luxton, Gary

    2007-07-01

    A hypofractionation treatment protocol for prostate cancer was initiated in our department in December 2003. The treatment regimen consists of a total dose of 36.25 Gy delivered at 7.25 Gy per fraction over 10 days. We discuss the rationale for such a prostate hypofractionation protocol and the need for frequent prostate imaging during treatment. The CyberKnife (Accuray Inc., Sunnyvale, CA), a linear accelerator mounted on a robotic arm, is currently being used as the radiation delivery device for this protocol, due to its incorporation of near real-time kV imaging of the prostate via 3 gold fiducial seeds. Recently introduced conventional linac kV imaging with intensity modulated planning and delivery may add a new option for these hypofractionated treatments. The purpose of this work is to investigate the use of intensity modulated radiotherapy (IMRT) and the Varian Trilogy Accelerator with on-board kV imaging (Varian Medical Systems Inc., Palo Alto, CA) for treatment of our hypofractionated prostate patients. The dose-volume histograms and dose statistics of 2 patients previously treated on the CyberKnife were compared to 7-field IMRT plans. A process of acquiring images to observe intrafraction prostate motion was achieved in an average time of about 1 minute and 40 seconds, and IMRT beam delivery takes about 40 seconds per field. A complete 7-field IMRT plan can therefore be imaged and delivered in 10 to 17 minutes. The Varian Trilogy Accelerator with on-board imaging and IMRT is well suited for image-guided hypofractionated prostate treatments. During this study, we have also uncovered opportunities for improvement of the on-board imaging hardware/software implementation that would further enhance performance in this regard.

  10. EDITORIAL: Semiconductor nanotechnology: novel materials and devices for electronics, photonics and renewable energy applications Semiconductor nanotechnology: novel materials and devices for electronics, photonics and renewable energy applications

    NASA Astrophysics Data System (ADS)

    Goodnick, Stephen; Korkin, Anatoli; Krstic, Predrag; Mascher, Peter; Preston, John; Zaslavsky, Alex

    2010-04-01

    Electronic and photonic information technology and renewable energy alternatives, such as solar energy, fuel cells and batteries, have now reached an advanced stage in their development. Cost-effective improvements to current technological approaches have made great progress, but certain challenges remain. As feature sizes of the latest generations of electronic devices are approaching atomic dimensions, circuit speeds are now being limited by interconnect bottlenecks. This has prompted innovations such as the introduction of new materials into microelectronics manufacturing at an unprecedented rate and alternative technologies to silicon CMOS architectures. Despite the environmental impact of conventional fossil fuel consumption, the low cost of these energy sources has been a long-standing economic barrier to the development of alternative and more efficient renewable energy sources, fuel cells and batteries. In the face of mounting environmental concerns, interest in such alternative energy sources has grown. It is now widely accepted that nanotechnology offers potential solutions for securing future progress in information and energy technologies. The Canadian Semiconductor Technology Conference (CSTC) forum was established 25 years ago in Ottawa as an important symbol of the intrinsic strength of the Canadian semiconductor research and development community, and the Canadian semiconductor industry as a whole. In 2007, the 13th CSTC was held in Montreal, moving for the first time outside the national capital region. The first three meetings in the series of 'Nano and Giga Challenges in Electronics and Photonics'— NGCM2002 in Moscow, NGCM2004 in Krakow, and NGC2007 in Phoenix— were focused on interdisciplinary research from the fundamentals of materials science to the development of new system architectures. In 2009 NGC2009 and the 14th Canadian Semiconductor Technology Conference (CSTC2009) were held as a joint event, hosted by McMaster University (10-14 August, Hamilton, Ontario, Canada) and the scope was expanded to include renewable energy research and development. This special issue of Nanotechnology is devoted to a better understanding of the function and design of semiconductor devices that are relevant to information technology (both electronics and photonics based) and renewable energy applications. The papers contained in this special issue are selected from the NGC/CSTC2009 symposium. Among them is a report by Ray LaPierre from McMaster University and colleagues at the University of Waterloo in Canada on the ability to manipulate single spins in nanowire quantum bits. The paper also reports the development of a testbed of a few qubits for general quantum information processing tasks [1]. Lower cost and greater energy conversion efficiency compared with thin film devices have led to a high level of activity in nanowire research related to photovoltaic applications. This special issue also contains results from an impedance spectroscopy study of core-shell GaAs nanowires to throw light on the transport and recombination mechanisms relevant to solar cell research [2]. Information technology research and renewable energy sources are research areas of enormous public interest. This special issue addresses both theoretical and experimental achievements and provides a stimulating outlook for technological developments in these highly topical fields of research. References [1] Caram J, Sandoval C, Tirado M, Comedi D, Czaban J, Thompson D A and LaPierre R R 2101 Nanotechnology 21 134007 [2] Baugh J, Fung J S and LaPierre RR 2010 Nanotechnology 21 134018

  11. Robust Eye Center Localization through Face Alignment and Invariant Isocentric Patterns.

    PubMed

    Pang, Zhiyong; Wei, Chuansheng; Teng, Dongdong; Chen, Dihu; Tan, Hongzhou

    2015-01-01

    The localization of eye centers is a very useful cue for numerous applications like face recognition, facial expression recognition, and the early screening of neurological pathologies. Several methods relying on available light for accurate eye-center localization have been exploited. However, despite the considerable improvements that eye-center localization systems have undergone in recent years, only few of these developments deal with the challenges posed by the profile (non-frontal face). In this paper, we first use the explicit shape regression method to obtain the rough location of the eye centers. Because this method extracts global information from the human face, it is robust against any changes in the eye region. We exploit this robustness and utilize it as a constraint. To locate the eye centers accurately, we employ isophote curvature features, the accuracy of which has been demonstrated in a previous study. By applying these features, we obtain a series of eye-center locations which are candidates for the actual position of the eye-center. Among these locations, the estimated locations which minimize the reconstruction error between the two methods mentioned above are taken as the closest approximation for the eye centers locations. Therefore, we combine explicit shape regression and isophote curvature feature analysis to achieve robustness and accuracy, respectively. In practical experiments, we use BioID and FERET datasets to test our approach to obtaining an accurate eye-center location while retaining robustness against changes in scale and pose. In addition, we apply our method to non-frontal faces to test its robustness and accuracy, which are essential in gaze estimation but have seldom been mentioned in previous works. Through extensive experimentation, we show that the proposed method can achieve a significant improvement in accuracy and robustness over state-of-the-art techniques, with our method ranking second in terms of accuracy. According to our implementation on a PC with a Xeon 2.5Ghz CPU, the frame rate of the eye tracking process can achieve 38 Hz.

  12. Development and Evaluation of Multiple Isocentric Volumetric Modulated Arc Therapy Technique for Craniospinal Axis Radiotherapy Planning

    SciTech Connect

    Lee, Young K.; Brooks, Corrinne J.; Bedford, James L.; Warrington, Alan P.; Saran, Frank H.

    2012-02-01

    Purpose: To develop and compare a volumetric modulated arc therapy (VMAT) technique with conventional radiotherapy for craniospinal irradiation with respect to improved dose conformity and homogeneity in the planning target volume (PTV) and to reduced dose to organs at risk (OAR). Methods and Materials: Conventional craniospinal axis radiotherapy plans of 5 patients were acquired. The median (range) length of the PTV was 58.9 (48.1-83.7) cm. The 6-MV VMAT plans were inversely planned with one isocenter near the base of the brain and the minimum number of isocenters required for the specified lengths of spine. The plans were optimized with high weighting for PTV coverage and low weighting for OAR sparing. Conformity and heterogeneity indices, dose-volume histograms, mean doses, and non-PTV integral doses from the two plans (prescription dose 23.4 Gy in 13 fractions) were compared. Results: The median (range) conformity index of VMAT was 1.22 (1.09-1.45), compared with 1.69 (1.44-2.67) for conventional plans (p = 0.04). The median (range) heterogeneity index was also lower for VMAT compared with conventional plans: 1.04 (1.03-1.07) vs. 1.12 (1.09-1.19), respectively (p = 0.04). A significant reduction of mean and maximum doses was observed in the heart, thyroid, esophagus, optic nerves, and eyes with VMAT when compared with conventional plans. A decrease in body V{sub 10Gy} was observed, but for 4 of 5 patients non-PTV integral dose was increased with VMAT when compared with the conventional plans. Conclusions: A VMAT technique to treat the craniospinal axis significantly reduces OAR dose, potentially leading to lower late organ toxicity. However, this is achieved at the expense of increased low-dose volumes, which is inherent to the technique, carrying a potentially increased risk of secondary malignancies.

  13. Total-body irradiation on an isocentric linear accelerator: a radiation output compensation technique.

    PubMed

    Hugtenburg, R P; Turner, J R; Baggarley, S P; Pinchin, D A; Oien, N A; Atkinson, C H; Tremewan, R N

    1994-05-01

    A treatment technique for total-body irradiation (TBI) is proposed that combines arc therapy with dynamic output control to achieve high-grade dose uniformity. The patient lies on a low couch and receives exposure in the prone and supine positions from a modulated arcing beam. The technique has been validated using a personal computer to control the linear accelerator and we demonstrate that only minor alterations to current dynamic therapy systems would be required. We have examined the practical application of this treatment with emphasis on methods of conformal therapy where an optimized dose distribution is prepared from a matrix of caliper measurements taken from the patient. This technique provides a means for regular TBI treatment on a computer-controlled linear accelerator that is easy to set up, requires short exposure times and is comfortable for the patient.

  14. Robust Eye Center Localization through Face Alignment and Invariant Isocentric Patterns

    PubMed Central

    Teng, Dongdong; Chen, Dihu; Tan, Hongzhou

    2015-01-01

    The localization of eye centers is a very useful cue for numerous applications like face recognition, facial expression recognition, and the early screening of neurological pathologies. Several methods relying on available light for accurate eye-center localization have been exploited. However, despite the considerable improvements that eye-center localization systems have undergone in recent years, only few of these developments deal with the challenges posed by the profile (non-frontal face). In this paper, we first use the explicit shape regression method to obtain the rough location of the eye centers. Because this method extracts global information from the human face, it is robust against any changes in the eye region. We exploit this robustness and utilize it as a constraint. To locate the eye centers accurately, we employ isophote curvature features, the accuracy of which has been demonstrated in a previous study. By applying these features, we obtain a series of eye-center locations which are candidates for the actual position of the eye-center. Among these locations, the estimated locations which minimize the reconstruction error between the two methods mentioned above are taken as the closest approximation for the eye centers locations. Therefore, we combine explicit shape regression and isophote curvature feature analysis to achieve robustness and accuracy, respectively. In practical experiments, we use BioID and FERET datasets to test our approach to obtaining an accurate eye-center location while retaining robustness against changes in scale and pose. In addition, we apply our method to non-frontal faces to test its robustness and accuracy, which are essential in gaze estimation but have seldom been mentioned in previous works. Through extensive experimentation, we show that the proposed method can achieve a significant improvement in accuracy and robustness over state-of-the-art techniques, with our method ranking second in terms of accuracy. According to our implementation on a PC with a Xeon 2.5Ghz CPU, the frame rate of the eye tracking process can achieve 38 Hz. PMID:26426929

  15. Development and evaluation of multiple isocentric volumetric modulated arc therapy technique for craniospinal axis radiotherapy planning.

    PubMed

    Lee, Young K; Brooks, Corrinne J; Bedford, James L; Warrington, Alan P; Saran, Frank H

    2012-02-01

    To develop and compare a volumetric modulated arc therapy (VMAT) technique with conventional radiotherapy for craniospinal irradiation with respect to improved dose conformity and homogeneity in the planning target volume (PTV) and to reduced dose to organs at risk (OAR). Conventional craniospinal axis radiotherapy plans of 5 patients were acquired. The median (range) length of the PTV was 58.9 (48.1-83.7) cm. The 6-MV VMAT plans were inversely planned with one isocenter near the base of the brain and the minimum number of isocenters required for the specified lengths of spine. The plans were optimized with high weighting for PTV coverage and low weighting for OAR sparing. Conformity and heterogeneity indices, dose-volume histograms, mean doses, and non-PTV integral doses from the two plans (prescription dose 23.4 Gy in 13 fractions) were compared. The median (range) conformity index of VMAT was 1.22 (1.09-1.45), compared with 1.69 (1.44-2.67) for conventional plans (p = 0.04). The median (range) heterogeneity index was also lower for VMAT compared with conventional plans: 1.04 (1.03-1.07) vs. 1.12 (1.09-1.19), respectively (p = 0.04). A significant reduction of mean and maximum doses was observed in the heart, thyroid, esophagus, optic nerves, and eyes with VMAT when compared with conventional plans. A decrease in body V(10Gy) was observed, but for 4 of 5 patients non-PTV integral dose was increased with VMAT when compared with the conventional plans. A VMAT technique to treat the craniospinal axis significantly reduces OAR dose, potentially leading to lower late organ toxicity. However, this is achieved at the expense of increased low-dose volumes, which is inherent to the technique, carrying a potentially increased risk of secondary malignancies. Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.

  16. SU-E-J-239: IMRT Planning of Prostate Cancer for a MRI-Linac Based On MRI Only

    SciTech Connect

    Chen, X; Prior, P; Paulson, E; Lawton, C; Li, X

    2014-06-01

    Purpose: : To investigate dosimetric differences between MRI- and CT-based IMRT planning for prostate cancer, the impact of a magnetic field in a MRI-Linac, and to explore the feasibility of IMRT planning based on MRI alone. Methods: IMRT plans were generated based on CT and MRI images acquired on two representative prostate-cancer patients using clinical dose volume constraints. A research planning system (Monaco, Elekta), which employs a Monte Carlo dose engine and includes a perpendicular magnetic field of 1.5T from an MRI-Linac, was used. Bulk electron density assignments based on organ-specific values from ICRU 46 were used to convert MRI (T2) to pseudo CT. With the same beam configuration as in the original CT plan, 5 additional plans were generated based on CT or MRI, with or without optimization (i.e., just recalculation) and with or without the magnetic field. The plan quality in terms of commonly used dose volume (DV) parameters for all plans was compared. The statistical uncertainty on dose was < 1%. Results: For plans with the same contour set but without re-optimization, the DV parameters were different from those for the original CT plan, mostly less than 5% with a few exceptions. These differences were reduced to mostly less than 3% when the plans were re-optimized. For plans with contours from MRI, the differences in the DV parameters varied depending on the difference in the contours as compared to CT. For the optimized plans with contours from MR, the differences for PTV were less than 3%. Conclusion: The prostate IMRT plans based on MRI-only for a MR-Linac were practically similar as compared to the CT plan under the same beam and optimization configuration if the difference on the structure delineation is excluded, indicating the feasibility of using MRI-only for prostate IMRT.

  17. SU-E-T-305: Dosimetric Comparison of Cyberknife Versus Linac Based VMAT Stereotactic Treatment Planning for Localised Prostate Cancer

    SciTech Connect

    Senniandavar, V; Vikraman, S; KP, K; Rajesh, T; Sambasivaselli, R; Ramu, M; Maragathaveni, S; Dhivya, N; Tejinder, K

    2015-06-15

    Purpose: The purpose of this study was to compare dosimetric indices of Cyberknife versus Linac for localised prostate cancer Methods: In this study, twenty patients were taken from Cyberknife Multiplan TPS v 4.6.0. All these patients underwent hypo fractionated boost treatment for localised prostate cancer in Cyberknife with the prescription dose of 18Gy in 3 fractions. For each patient VMAT stereotactic plans were generated in Monaco TPS v 5.0 using Elekta beam modulator MLC machine for 6MV photon beam. The plans quality were evaluated by comparing dosimetry indices such that D95, D90, D5 for target volume and V100, V80, V50, V30 for critical organs. The p values were calculated for target and OAR to ascertain the significant differences. Results: For each case, D95 of target coverage was achieved with 100% prescription dose with p value of 0.9998. The p value for D90, D5 and V100 for linac and Cyberknife plans was 0.9938, 0.9918 and 0.9838 respectively. For rectum, rectum-PTV and bladder doses were significantly less in Cyberknife compared to linac plans. For rectum, rectum-PTV and bladder at V100 the p value is 0.2402, 0.002, and 0.1615 respectively. Other indices V80, V50 and V30 were comparable in both plans. Conclusion: This study demonstrated that both linac and Cyberknife plans were shown adequate target coverage, while in Cyberknife the treatment time is longer and more MUs to be delivered. However, better conformity, lesser doses to the critical organs and dose gradient outside target for localised prostate treatment were achieved in Cyberknife plans due to multiple non coplanar beam arrangements.

  18. Ultrafast harmonic rf kicker design and beam dynamics analysis for an energy recovery linac based electron circulator cooler ring

    DOE PAGES

    Huang, Yulu; Wang, Haipeng; Rimmer, Robert A.; ...

    2016-08-01

    An ultrafast kicker system is being developed for the energy recovery linac (ERL) based electron circulator cooler ring (CCR) in the proposed Jefferson Lab Electron Ion Collider (JLEIC, previously named MEIC). In the CCR, the injected electron bunches can be recirculated while performing ion cooling for 10–30 turns before the extraction, thus reducing the recirculation beam current in the ERL to 1/10–1/30 (150mA–50 mA) of the cooling beam current (up to 1.5 A). Assuming a bunch repetition rate of 476.3 MHz and a recirculating factor of 10 in the CCR, the kicker is required to operate at a pulse repetitionmore » rate of 47.63 MHz with pulse width of around 2 ns, so that only every 10th bunch in the CCR will experience a transverse kick while the rest of the bunches will not be disturbed. Such a kicker pulse can be synthesized by ten harmonic modes of the 47.63 MHz kicker pulse repetition frequency, using up to four quarter wavelength resonator (QWR) based deflecting cavities. In this paper, several methods to synthesize such a kicker waveform will be discussed and a comparison of their beam dynamics performance is made using ELEGANT. Four QWR cavities are envisaged with high transverse shunt impedance requiring less than 100 W of total rf power for a Flat-Top kick pulse. Multipole fields due to the asymmetry of this type of cavity are analyzed. The transverse emittance growth due to the sextupole component is simulated in ELEGANT. In conclusion, off-axis injection and extraction issues and beam optics using a multicavity kick-drift scheme will also be discussed.« less

  19. Development of mini linac-based positron source and an efficient positronium convertor for positively charged antihydrogen production

    NASA Astrophysics Data System (ADS)

    Muranaka, T.; Debu, P.; Dupré, P.; Liszkay, L.; Mansoulie, B.; Pérez, P.; Rey, J. M.; Ruiz, N.; Sacquin, Y.; Crivelli, P.; Gendotti, U.; Rubbia, A.

    2010-04-01

    We have installed in Saclay a facility for an intense positron source in November 2008. It is based on a compact 5.5 MeV electron linac connected to a reaction chamber with a tungsten target inside to produce positrons via pair production. The expected production rate for fast positrons is 5·1011 per second. The study of moderation of fast positrons and the construction of a slow positron trap are underway. In parallel, we have investigated an efficient positron-positronium convertor using porous silica materials. These studies are parts of a project to produce positively charged antihydrogen ions aiming to demonstrate the feasibility of a free fall antigravity measurement of neutral antihydrogen.

  20. SU-E-J-48: Imaging Origin-Radiation Isocenter Coincidence for Linac-Based SRS with Novalis Tx

    SciTech Connect

    Geraghty, C; Workie, D; Hasson, B

    2015-06-15

    Purpose To implement and evaluate an image-based Winston-Lutz (WL) test to measure the displacement between ExacTrac imaging origin and radiation isocenter on a Novalis Tx system using RIT V6.2 software analysis tools. Displacement between imaging and radiation isocenters was tracked over time. The method was applied for cone-based and MLC-based WL tests. Methods The Brainlab Winston-Lutz phantom was aligned to room lasers. The ExacTrac imaging system was then used to detect the Winston- Lutz phantom and obtain the displacement between the center of the phantom and the imaging origin. EPID images of the phantom were obtained at various gantry and couch angles and analyzed with RIT calculating the phantom center to radiation isocenter displacement. The RIT and Exactrac displacements were combined to calculate the displacement between imaging origin and radiation isocenter. Results were tracked over time. Results Mean displacements between ExacTrac origin and radiation isocenter were: VRT: −0.1mm ± 0.3mm, LNG: 0.5mm ± 0.2mm, LAT: 0.2mm ± 0.2mm (vector magnitude of 0.7 ± 0.2mm). Radiation isocenter was characterized by the mean of the standard deviations of the WL phantom displacements: σVRT: 0.2mm, σLNG: 0.4mm, σLAT: 0.6mm. The linac couch base was serviced to reduce couch walkout. This reduced σLAT to 0.2mm. These measurements established a new baseline of radiation isocenter-imaging origin coincidence. Conclusion The image-based WL test has ensured submillimeter localization accuracy using the ExacTrac imaging system. Standard deviations of ExacTrac-radiation isocenter displacements indicate that average agreement within 0.3mm is possible in each axis. This WL test is a departure from the tradiational WL in that imaging origin/radiation isocenter agreement is the end goal not lasers/radiation isocenter.

  1. SYNCHROTRON RADIATION, FREE ELECTRON LASER, APPLICATION OF NUCLEAR TECHNOLOGY, ETC.: Study on the characteristics of linac based THz light source

    NASA Astrophysics Data System (ADS)

    Zhu, Xiong-Wei; Wang, Shu-Hong; Chen, Sen-Yu

    2009-10-01

    There are many methods based on linac for THz radiation production. As one of the options for the Beijing Advanced Light, an ERL test facility is proposed for THz radiation. In this test facility, there are 4 kinds of methods to produce THz radiation: coherent synchrotron radiation (CSR), synchrotron radiation (SR), low gain FEL oscillator, and high gain SASE FEL. In this paper, we study the characteristics of the 4 kinds of THz light sources.

  2. Linac-based positron source and generation of a high density positronium cloud for the GBAR experiment

    NASA Astrophysics Data System (ADS)

    Liszkay, L.; Comini, P.; Corbel, C.; Debu, P.; Dupré, P.; Grandemange, P.; Pérez, P.; Rey, J.-M.; Ruiz, N.; Sacquin, Y.

    2013-06-01

    The aim of the recently approved GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment is to measure the acceleration of neutral antihydrogen atoms in the gravitational field of the Earth. The experimental scheme requires a high density positronium cloud as a target for antiprotons, provided by the Antiproton Decelerator (AD) - Extra Low Energy Antiproton Ring (ELENA) facility at CERN. We introduce briefly the experimental scheme and present the ongoing efforts at IRFU CEA Saclay to develop the positron source and the positron-positronium converter, which are key parts of the experiment. We have constructed a slow positron source in Saclay, based on a low energy (4.3 MeV) linear electron accelerator (linac). By using an electron target made of tungsten and a stack of thin W meshes as positron moderator, we reached a slow positron intensity that is comparable with that of 22Na-based sources using a solid neon moderator. The source feeds positrons into a high field (5 T) Penning-Malmberg trap. Intense positron pulses from the trap will be converted to slow ortho-positronium (o-Ps) by a converter structure. Mesoporous silica films appear to date to be the best candidates as converter material. We discuss our studies to find the optimal pore configuration for the positron-positronium converter.

  3. A new scheme to accumulate positrons in a Penning-Malmberg trap with a linac-based positron pulsed source

    NASA Astrophysics Data System (ADS)

    Dupré, P.

    2013-03-01

    The Gravitational Behaviour of Antimatter at Rest experiment (GBAR) is designed to perform a direct measurement of the weak equivalence principle on antimatter by measuring the acceleration of anti-hydrogen atoms in the gravitational field of the Earth. The experimental scheme requires a high density positronium (Ps) cloud as a target for antiprotons, provided by the Antiproton Decelerator (AD) - Extra Low Energy Antiproton Ring (ELENA) facility at CERN. The Ps target will be produced by a pulse of few 1010 positrons injected onto a positron-positronium converter. For this purpose, a slow positron source using an electron Linac has been constructed at Saclay. The present flux is comparable with that of 22Na-based sources using solid neon moderator. A new positron accumulation scheme with a Penning-Malmberg trap has been proposed taking advantage of the pulsed time structure of the beam. In the trap, the positrons are cooled by interaction with a dense electron plasma. The overall trapping efficiency has been estimated to be ˜70% by numerical simulations.

  4. Development of a Comprehensive Linac-based Quality Assurance Program for a Retrofitted Micro-MLC SRS System

    NASA Astrophysics Data System (ADS)

    Hancock, George

    In Stereotactic Radiosurgery, one of the most import factors that must be measured is the accuracy of the localization system, whether it be lasers or camera system; and the coincidence of the localized isocenter to the radiation isocenter. According to TG-142 the minimum deviation between the isocenter determined by the localization device and the radiation isocenter of the machine must be no more that 1 mm. In addition, the minimum deviation, also recommended by TG-142, between the radiation isocenter and the mechanical isocenter of the machine must be no more that 1mm. The purpose of this research was to develop a method that both of these parameters could be measured and add these tests to our patient specific QA, monthly QA, and annual QA procedures. A plastic phantom was constructed with holes drilled in each of the sides to meet at a common point in the middle of the phantom. This common intersection was then set as the isocenter for the treatment beams, and the coordinates of the point were sent to the camera system. Measurements were than taken with both the EPID and GafChromic film with the use of rigid tungsten rods in each hole to mark the position of the holes on the film and EPID. The films were then scanned and the field edges and isocenter positions were determined by taking the coordinates of a point that was halfway between the minimum and maximum points in all cases.

  5. SU-E-T-413: Dose Verification for Linac-Based SRS Commissioning and Patient Specific QA.

    PubMed

    Wu, J; Wu, H

    2012-06-01

    Stereotactic Radiosurgery (SRS) program commissioning is currently relied on Radiological Physics Center (RPC) Head Neck phantom with Thermo Luminescent Dosimeters (TLDs) for dose verification. However, due to the limited accessibility of RPC Head Neck phantom, ongoing QA or patient specific dose verification is not performed in most clinics. In this study, we proposed an SRS dose verification approach for both SRS commissioning and patient specific dose verification with widely available clinical instruments. SRS treatment plans were imposed onto a 14cm thick conventional solid water phantom (30cm × 30cm), with a PTW micro-chamber in the middle. Treatment couch angles were renormalized to 90 or 270 degrees for two reasons: 1) micro-chamber's axis was parallel to gantry rotation axis during all the arc beam delivery, which minimizes the angle dependence effect (axis tilt) of micro-chamber. 2) Any collision between the cone and conventional solid water phantom would be avoided and there would be minimum attenuation effect from the couch. The arc verification plan was then recalculated and compared to the measured absolute dose by PTW micro-chamber. An End-to-End test with a CyberKnife Head Neck phantom and GAFChromic EBT2 film was utilized as secondary dose delivery verification. Cones with all twelve different sizes in SRS commissioning were tested. For the cone size from 10mm to 30mm, the micro-chamber measurements agreed with the computer calculations within 3%. However, when the cone size was reduced to 5mm, micro-chamber measurement was 10% lower than planned dose, indicating underdose effect for small cone size. Additional measurements with Cyberknife head phantom confirmed the dose delivery accuracy was within 5%. A simple SRS dose verification method which only requires micro-chamber and conventional solid water phantom has been presented and verified. This approach will be valuable for SRS commissioning and ongoing SRS QA. © 2012 American Association of Physicists in Medicine.

  6. SU-E-T-54: A New Method for Optimizing Radiation Isocenter for Linac-Based SRS

    SciTech Connect

    Hancock, S; Hyer, D; Nixon, E

    2015-06-15

    Purpose: To develop a new method to minimize deviation of linac x-ray beams from the centroid of the volumetric radiation isocenter for all combinations of gantry and table angle. Methods: A set of ball-bearing (Winston-Lutz) images was used to determine the gantry radiation isocenter as the midrange of deviation values. Deviations in the cross-plane direction were minimized by calibration of MLC leaf position offset, and by adjusting beam position steering for each energy. Special attention was also paid to matching the absolute position of isocenter across all energies by adjusting position steering in the gun-target axis. Displacement of table axis from the gantry isocenter, and recommended table axis adjustment for contemporary Elekta linacs, was also determined. Eight images were used to characterize the volumetric isocenter for the full range of gantry and table rotations available. Tabulation of deviation for each beam was used to test compliance with isocenter tolerance. Results: Four contemporary Elekta linacs were evaluated and the radius in the gun-target axis of the radiation isocenter was 0.5 to 0.7 mm. After beam steering adjustment, the radius in the cross-plane direction was typically 0.2 to 0.4 mm. Position matching between energies can be reduced to 0.28 mm. Maximum total deviation was 0.68 to 1.07 mm, depending primarily on the effect of systematic table axis wobble with rotation. Conclusion: This new method effectively facilitates minimization of deviation between beam center and target position. The test, which requires a few minutes to perform, can be easily incorporated into a routine machine QA program. A tighter radiation isocenter for contemporary Elekta linacs would require reducing the effect of gantry arm flex and/or table axis wobble that are the two main components of deviation from the designated isocenter point.

  7. SU-E-T-245: Detection of the Photon Target Damage in Varian Linac Based On Periodical Quality Assurance Measurements

    SciTech Connect

    Gao, S; Balter, P; Wang, X; Sadagopan, R; Pollard, J

    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 identified 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.

  8. First results from electron-photon damage equivalence studies on a generic ethylene-propylene rubber

    SciTech Connect

    Buckalew, W.H.

    1986-04-01

    As part of a simulator adequacy assessment program, the relative effectiveness of electrons and photons to produce damage in a generic ethylene propylene rubber (EPR) has been investigated. The investigation was limited in extent in that a single EPR material, in three thickness, was exposed to Cobalt-60 photons and three electron beam energies. Basing material damage on changes in the EPR mechanical properties elongation and tensile strength, we observed that EPR damage was a smoothly varying function of absorbed energy and independent of irradiating particle type. EPR damage tracked equally well as a function of both incident particle energy and material front surface dose. Based on these preliminary data, we tentatively concluded that a correlation between particle, particle energy, and material damage (as measured by changes in material elongation and/or tensile strength) has been demonstrated. 14 figs.

  9. Integral functions of electron lateral distribution and their fluctuations in electron-photon cascades

    NASA Technical Reports Server (NTRS)

    Ivanenko, I. P.; Kanevsky, B. L.; Kirillov, A. A.; Linde, I. A.; Lyutov, Y. G.

    1985-01-01

    Monte Carlo simulated lateral distribution functions for electrons of EPC developing in lead, at superhigh energies (.1-1 PeV) for depths t or = 60 c.u. delta t=1t. c.u. are presented. The higher moment characteristics, i.e., variation, asymmetry, excess, are presented along with analytical solutions for the same characteristics at fixed observation level calculated to theory approximations A and B by using numerical inversion of the Laplace transformation. The conclusion is made of a complex, usually non-Gaussian shape of the function of the particle number distribution within a circle of given radius at fixed depth.

  10. An empirical method for deriving RBE values associated with electrons, photons and radionuclides.

    PubMed

    Bellamy, M; Puskin, J; Hertel, N; Eckerman, K

    2015-12-01

    There is substantial evidence to justify using relative biological effectiveness (RBE) values of >1 for low-energy electrons and photons. But, in the field of radiation protection, radiation associated with low linear energy transfer has been assigned a radiation weighting factor wR of 1. This value may be suitable for radiation protection but, for risk considerations, it is important to evaluate the potential elevated biological effectiveness of radiation to improve the quality of risk estimates. RBE values between 2 and 3 for tritium are implied by several experimental measurements. Additionally, elevated RBE values have been found for other similar low-energy radiation sources. In this work, RBE values are derived for electrons based upon the fractional deposition of absorbed dose of energies less than a few kiloelectron volts. Using this empirical method, RBE values were also derived for monoenergetic photons and 1070 radionuclides from ICRP Publication 107 for which photons and electrons are the primary emissions. Published by Oxford University Press 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

  11. Discrete Chromatic Aberrations Arising from Photoinduced Electron-Photon Interactions in Ultrafast Electron Microscopy.

    PubMed

    Plemmons, Dayne A; Flannigan, David J

    2016-05-26

    In femtosecond ultrafast electron microscopy (UEM) experiments, the initial excitation period is composed of spatiotemporal overlap of the temporally commensurate pump photon pulse and probe photoelectron packet. Generation of evanescent near-fields at the nanostructure specimens produces a dispersion relation that enables coupling of the photons (ℏω = 2.4 eV, for example) and freely propagating electrons (200 keV, for example) in the near-field. Typically, this manifests as discrete peaks occurring at integer multiples (n) of the photon energy in the low-loss/gain region of electron-energy spectra (i.e., at 200 keV ± nℏω eV). Here, we examine the UEM imaging resolution implications of the strong inelastic near-field interactions between the photons employed in optical excitation and the probe photoelectrons. We find that the additional photoinduced energy dispersion occurring when swift electrons pass through intense evanescent near-fields results in a discrete chromatic aberration that limits the spatial resolving power to several angstroms during the excitation period.

  12. Electrons, Photons, and Force: Quantitative Single-Molecule Measurements from Physics to Biology

    PubMed Central

    2011-01-01

    Single-molecule measurement techniques have illuminated unprecedented details of chemical behavior, including observations of the motion of a single molecule on a surface, and even the vibration of a single bond within a molecule. Such measurements are critical to our understanding of entities ranging from single atoms to the most complex protein assemblies. We provide an overview of the strikingly diverse classes of measurements that can be used to quantify single-molecule properties, including those of single macromolecules and single molecular assemblies, and discuss the quantitative insights they provide. Examples are drawn from across the single-molecule literature, ranging from ultrahigh vacuum scanning tunneling microscopy studies of adsorbate diffusion on surfaces to fluorescence studies of protein conformational changes in solution. PMID:21338175

  13. An Empirical Method for deriving RBE values associated with Electrons, Photons and Radionuclides

    DOE PAGES

    Bellamy, Michael B; Puskin, J.; Eckerman, Keith F.; ...

    2015-01-01

    There is substantial evidence to justify using relative biological effectiveness (RBE) values greater than one for low-energy electrons and photons. But, in the field of radiation protection, radiation associated with low linear energy transfer (LET) has been assigned a radiation weighting factor wR of one. This value may be suitable for radiation protection but, for risk considerations, it is important to evaluate the potential elevated biological effectiveness of radiation to improve the quality of risk estimates. RBE values between 2 and 3 for tritium are implied by several experimental measurements. Additionally, elevated RBE values have been found for other similarmore » low-energy radiation sources. In this work, RBE values are derived for electrons based upon the fractional deposition of absorbed dose of energies less than a few keV. Using this empirical method, RBE values were also derived for monoenergetic photons and 1070 radionuclides from ICRP Publication 107 for which photons and electrons are the primary emissions.« less

  14. Instrumentation and Beam Dynamics Study of Advanced Electron-Photon Facility in Indiana University

    SciTech Connect

    Luo, Tianhuan

    2011-08-01

    The Advanced eLectron-PHoton fAcility (ALPHA) is a compact electron accelerator under construction and being commissioned at the Indiana University Center for Exploration of Energy and Matter (CEEM). In this thesis, we have studied the refurbished Cooler Injector Synchrotron (CIS) RF cavity using both the transmission line model and SUPERFISH simulation. Both low power and high power RF measurements have been carried out to characterize the cavity. Considering the performance limit of ferrite, we have designed a new ferrite loaded, co-axial quarter wave like cavity with similar structure but a more suitable ferrite material. We have also designed a traveling wave stripline kicker for fast extraction by POISSON and Microwave Studio. The strips geometry is trimmed to maximize the uniformity of the kicking field and match the impedance of the power cables. The time response simulation shows the kicker is fast enough for machine operation. The pulsed power supply requirement has also been specified. For the beam diagnosis in the longitudinal direction, we use a wideband Wall Gap Monitor (WGM) served in CIS. With proper shielding and amplification to get good WGM signal, we have characterized the injected and extracted beam signal in single pass commissioning, and also verified the debunching effect of the ALPHA storage ring. A modulation-demodulation signal processing method is developed to measure the current and longitudinal profile of injected beam. By scanning the dipole strength in the injection line, we have reconstructed the tomography of the longitudinal phase space of the LINAC beam. In the accumulation mode, ALPHA will be operated under a low energy and high current condition, where intra beam scattering (IBS) becomes a dominant effect on the beam emittance. A self consistent simulation, including IBS effect, gas scattering and linear coupling, has been carried out to calculate the emittance of the stored beam.

  15. An Empirical Method for deriving RBE values associated with Electrons, Photons and Radionuclides

    SciTech Connect

    Bellamy, Michael B; Puskin, J.; Eckerman, Keith F.; Hertel, Nolan

    2015-01-01

    There is substantial evidence to justify using relative biological effectiveness (RBE) values greater than one for low-energy electrons and photons. But, in the field of radiation protection, radiation associated with low linear energy transfer (LET) has been assigned a radiation weighting factor wR of one. This value may be suitable for radiation protection but, for risk considerations, it is important to evaluate the potential elevated biological effectiveness of radiation to improve the quality of risk estimates. RBE values between 2 and 3 for tritium are implied by several experimental measurements. Additionally, elevated RBE values have been found for other similar low-energy radiation sources. In this work, RBE values are derived for electrons based upon the fractional deposition of absorbed dose of energies less than a few keV. Using this empirical method, RBE values were also derived for monoenergetic photons and 1070 radionuclides from ICRP Publication 107 for which photons and electrons are the primary emissions.

  16. Photon-photon and electron-photon colliders with energies below a TeV

    SciTech Connect

    Mayda M. Velasco et al.

    2001-11-29

    We investigate the potential for detecting and studying Higgs bosons in {gamma}{gamma} and e{gamma} collisions at future linear colliders with energies below a TeV. Our study incorporates realistic {gamma}{gamma}spectra based on available laser technology, and NLC and CLIC acceleration techniques. Results include detector simulations. We study the cases of: (a) a SM-like Higgs boson based on a devoted low energy machine with {radical}s{sub ee} {le} 200 GeV; (b) the heavy MSSM Higgs bosons; and (c) charged Higgs bosons in e{gamma} collisions.

  17. Electron-photon coincidence technique for the absolute calibration of VUV detectors

    NASA Technical Reports Server (NTRS)

    Mcadams, R.; Srivastava, S. K.

    1983-01-01

    A method is described whereby VUV photon detectors can be accurately calibrated. This method is illustrated by taking the 58.4-nm transition of He as an example. The technique consists of crossing a monoenergetic electron beam with a beam of He atoms. When inelastically scattered electrons which have excited the 2 1P state are detected in coincidence with the 58.4-nm photons emitted in the decay of the excited state, the interaction volume formed by the crossed beams constitutes a standard source of photons. By comparing the number of detected coincidences with the predicted number the calibration can be made. A total detector efficiency of 0.024 + or - 0.003 is obtained for a Galileo 4830 channeltron.

  18. Electron-photon coupling in semimetals in a high magnetic field

    SciTech Connect

    Mihaila, Bogdan; Albers, Robert C; Littlewood, Peter B

    2009-01-01

    We consider the effect of electron-phonon coupling in semimetals in high magnetic fields, with regard to elastic modes that can lead to a redistribution of carriers between pockets. We show that in a clean three dimensional system, at each Landau level crossing, this leads to a discontinuity in the magnetostriction, and a divergent contribution to the elastic modulus. We estimate the magnitude of this effect in the group V semimetal Bismuth.

  19. Simultaneous production of mixed electron--photon beam in a medical LINAC: A feasibility study.

    PubMed

    Khaledi, Navid; Arbabi, Azim; Sardari, Dariush; Mohammadi, Mohammad; Ameri, Ahmad

    2015-06-01

    The electron or photon beams might be used for treatment of tumors. Each beam has its own advantage and disadvantages. Combo beam can increase the advantages. No investigation has been performed for producing simultaneous mixed electron and photon beam. In current study a device has been added to the Medical Linac to produce a mixed photon-electron beam. Firstly a Varian 2300CD head was simulated by MCNP Monte Carlo Code. Two sets of perforated lead sheets with 1 and 2 mm thickness and 0.2, 0.3, and 0.5 cm punches then placed at the top of the applicator holder tray. This layer produces bremsstrahlung x-ray upon impinging fraction electrons on it. The remaining fraction of electrons passes through the holes. The simulation was performed for 10 × 10, 6 × 6, and 4 × 4 cm(2) field size. For 10 × 10 cm(2) field size, among the punched targets, the largest penumbra difference between the depth of 1 and 7 cm was 72%. This difference for photon and electron beams were 31% and 325% respectively. A maximum of 39% photon percentage was produced by 2 mm target with 0.2 cm holes diameter layer. The minimum surface dose value was 4% lesser than pure electron beam. For small fields, unlike the pure electron beam, the PDD, penumbra, and flatness variations were negligible. The advantages of mixing the electron and photon beam is reduction of pure electron's penumbra dependency with the depth, especially for small fields, also decreasing of dramatic changes of PDD curve with irradiation field size. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  20. Electrons, photons, and force: quantitative single-molecule measurements from physics to biology.

    PubMed

    Claridge, Shelley A; Schwartz, Jeffrey J; Weiss, Paul S

    2011-02-22

    Single-molecule measurement techniques have illuminated unprecedented details of chemical behavior, including observations of the motion of a single molecule on a surface, and even the vibration of a single bond within a molecule. Such measurements are critical to our understanding of entities ranging from single atoms to the most complex protein assemblies. We provide an overview of the strikingly diverse classes of measurements that can be used to quantify single-molecule properties, including those of single macromolecules and single molecular assemblies, and discuss the quantitative insights they provide. Examples are drawn from across the single-molecule literature, ranging from ultrahigh vacuum scanning tunneling microscopy studies of adsorbate diffusion on surfaces to fluorescence studies of protein conformational changes in solution.

  1. Photon-Photon and Electron-Photon Colliders with Energies Below a TeV

    SciTech Connect

    Hewett, JoAnne L

    2002-01-07

    We investigate the potential for detecting and studying Higgs bosons in {gamma}{gamma} and e{gamma} collisions at future linear colliders with energies below a TeV. Our study incorporates realistic {gamma}{gamma} spectra based on available laser technology, and NLC and CLIC acceleration techniques. Results include detector simulations. We study the cases of: (a) a SM-like Higgs boson based on a devoted low energy machine with {radical}(s{sub ee}) {le} 200 GeV; (b) the heavy MSSM Higgs bosons; and (c) charged Higgs bosons in e{gamma} collisions.

  2. Parallel Finite Element Electron-Photon Transport Analysis on 2-D Unstructured Mesh

    SciTech Connect

    Drumm, C.R.

    1999-01-01

    A computer code has been developed to solve the linear Boltzmann transport equation on an unstructured mesh of triangles, from a Pro/E model. An arbitriwy arrangement of distinct material regions is allowed. Energy dependence is handled by solving over an arbitrary number of discrete energy groups. Angular de- pendence is treated by Legendre-polynomial expansion of the particle cross sections and a discrete ordinates treatment of the particle fluence. The resulting linear system is solved in parallel with a preconditioned conjugate-gradients method. The solution method is unique, in that the space-angle dependence is solved si- multaneously, eliminating the need for the usual inner iterations. Electron cross sections are obtained from a Goudsrnit-Saunderson modifed version of the CEPXS code. A one-dimensional version of the code has also been develop@ for testing and development purposes.

  3. Comptonization of X-rays by low-temperature electrons. [photon wavelength redistribution in cosmic sources

    NASA Technical Reports Server (NTRS)

    Illarionov, A.; Kallman, T.; Mccray, R.; Ross, R.

    1979-01-01

    A method is described for calculating the spectrum that results from the Compton scattering of a monochromatic source of X-rays by low-temperature electrons, both for initial-value relaxation problems and for steady-state spatial diffusion problems. The method gives an exact solution of the inital-value problem for evolution of the spectrum in an infinite homogeneous medium if Klein-Nishina corrections to the Thomson cross section are neglected. This, together with approximate solutions for problems in which Klein-Nishina corrections are significant and/or spatial diffusion occurs, shows spectral structure near the original photon wavelength that may be used to infer physical conditions in cosmic X-ray sources. Explicit results, shown for examples of time relaxation in an infinite medium and spatial diffusion through a uniform sphere, are compared with results obtained by Monte Carlo calculations and by solving the appropriate Fokker-Planck equation.

  4. Determination of isocentric machine parameters for inclined treatment volumes: a single solution for angled transverse or coronal treatment planes.

    PubMed

    Bradley, F L

    2001-01-01

    The derivation of the trigonometric equations necessary to calculate gantry, floor and collimator settings for a treatment plane at an angle phi to the transverse plane of the patient has been described previously. The derivation of a second set of equations to facilitate treatment in a plane at an angle phi to the coronal plane has also been described previously. This work reinterprets the geometry of inclined volumes and shows that essentially only one set of equations is required to determine the settings for treatment planes at an angle phi to either the transverse or coronal planes of the patient.

  5. The feasibility of MR-image guided prostate biopsy using piezoceramic motors inside or near to the magnet isocentre.

    PubMed

    Elhawary, Haytham; Zivanovic, Aleksander; Rea, Marc; Davies, Brian; Besant, Collin; McRobbie, Donald; de Souza, Nandita; Young, Ian; Lampérth, Michael

    2006-01-01

    The excellent soft tissue contrast of Magnetic Resonance Imaging (MRI) has encouraged the development of MRI compatible systems capable of combining the advantages of robotic manipulators with high quality anatomical images. Continuing this development, a new five DOF prostate biopsy manipulator has been designed for use inside a closed 1.5T MRI scanner. Space constraints in the bore and the current trend to restrict field strength exposure for operators indicate that a master-slave configuration is ideal for controlling the robotic system from outside the bore. This system has been designed to work with piezoceramic motors and optical encoders placed inside or near the field of view of the scanner, using real time image guidance for targeting biopsies to specific lesions in the prostate. MRI tests have been performed to prove the feasibility of this concept and a one DOF proof-of-concept test rig implementing closed loop position control has been tested and is presented here. A first prototype of the slave manipulator has been designed and manufactured incorporating this new technology.

  6. Extreme hypofractionation for early prostate cancer: Biology meets technology.

    PubMed

    De Bari, Berardino; Arcangeli, Stefano; Ciardo, Delia; Mazzola, Rosario; Alongi, Filippo; Russi, Elvio G; Santoni, Riccardo; Magrini, Stefano M; Jereczek-Fossa, Barbara A

    2016-11-01

    The aim of this review is to present the available radiobiological, technical and clinical data about extreme hypofractionation in primary prostate cancer radiotherapy. The interest in this technique is based on the favourable radiobiological characteristics of prostate cancer and supported by advantageous logistic aspects deriving from short overall treatment time. The clinical validity of short-term treatment schedule is proven by a body of non-randomised studies, using both isocentric (LINAC-based) or non-isocentric (CyberKnife(®)-based) stereotactic body irradiation techniques. Twenty clinical studies, each enrolling more than 40 patients for a total of 1874 treated patients, were revised in terms of technological setting, toxicity, outcome and quality of life assessment. The implemented strategies for the tracking of the prostate and the sparing of the rectal wall have been investigated with particular attention. The urinary toxicity after prostate stereotactic body irradiation seems slightly more pronounced as compared to rectal adverse events, and this is more evident for late occurring events, but no worse as respect to conventional fractionation schemes. As far as the rate of severe acute toxicity is concerned, in all the available studies the treatment was globally well tolerated. While awaiting long-term data on efficacy and toxicity, the analysed studies suggest that the outcome profile of this approach, alongside the patient convenience and reduced costs, is promising. Forty-eight ongoing clinical trials are also presented as a preview of the expectation from the near future.

  7. Linac-based extracranial radiosurgery with Elekta volumetric modulated arc therapy and an anatomy-based treatment planning system: Feasibility and initial experience

    SciTech Connect

    Cilla, Savino; Deodato, Francesco; Macchia, Gabriella; Digesù, Cinzia; Ianiro, Anna; Viola, Pietro; Craus, Maurizio; Valentini, Vincenzo; Piermattei, Angelo; Morganti, Alessio G.

    2016-07-01

    We reported our initial experience in using Elekta volumetric modulated arc therapy (VMAT) and an anatomy-based treatment planning system (TPS) for single high-dose radiosurgery (SRS-VMAT) of liver metastases. This study included a cohort of 12 patients treated with a 26-Gy single fraction. Single-arc VMAT plans were generated with Ergo++ TPS. The prescription isodose surface (IDS) was selected to fulfill the 2 following criteria: 95% of planning target volume (PTV) reached 100% of the prescription dose and 99% of PTV reached a minimum of 90% of prescription dose. A 1-mm multileaf collimator (MLC) block margin was added around the PTV. For a comparison of dose distributions with literature data, several conformity indexes (conformity index [CI], conformation number [CN], and gradient index [GI]) were calculated. Treatment efficiency and pretreatment dosimetric verification were assessed. Early clinical data were also reported. Our results reported that target and organ-at-risk objectives were met for all patients. Mean and maximum doses to PTVs were on average 112.9% and 121.5% of prescribed dose, respectively. A very high degree of dose conformity was obtained, with CI, CN, and GI average values equal to 1.29, 0.80, and 3.63, respectively. The beam-on-time was on average 9.3 minutes, i.e., 0.36 min/Gy. The mean number of monitor units was 3162, i.e., 121.6 MU/Gy. Pretreatment verification (3%-3 mm) showed an optimal agreement with calculated values; mean γ value was 0.27 and 98.2% of measured points resulted with γ < 1. With a median follow-up of 16 months complete response was observed in 12/14 (86%) lesions; partial response was observed in 2/14 (14%) lesions. No radiation-induced liver disease (RILD) was observed in any patients as well no duodenal ulceration or esophagitis or gastric hemorrhage. In conclusion, this analysis demonstrated the feasibility and the appropriateness of high-dose single-fraction SRS-VMAT in liver metastases performed with Elekta VMAT and Ergo++ TPS. Preliminary clinical outcomes showed a high rate of local control and minimum incidence of acute toxicity.

  8. Linac-based on-board imaging feasibility and the dosimetric consequences of head roll in head-and-neck IMRT plans

    SciTech Connect

    Kim, Gwe-Ya; Pawlicki, Todd Le, Quynh-Thu; Luxton, Gary

    2008-04-01

    Kilovoltage imaging systems on linear accelerators are used for patient localization in many clinics. The purpose of this work is to assess on-board imaging (OBI) detection of systematic setup errors and in particular, the dosimetric consequences of undetected head roll in head-and-neck intensity modulated radiation therapy (IMRT) plans when using these systems. The system used in this study was the Trilogy linear accelerator and associated software (Varian Medical Systems, Palo Alto, CA). Accuracy of OBI localization was evaluated using an anthropomorphic head phantom. The head phantom is rigidly attached to a specially designed positioning device with 5 deg. of freedom, 3 translational and 2 rotational in the axial and coronal planes. Simulated setup errors were 3 deg. and 5 deg. rotations in the axial plane and displacements of 5 mm in the left-right, anterior-posterior, and superior-inferior directions. The coordinates set by the positioning device were compared with the coordinates obtained as measured by using the image matching tools of paired 2-dimensional (2D) orthogonal image matching, and 3D cone-beam computed tomography (CT) volume matching. In addition, 6 physician-approved IMRT plans of nasopharynx and tonsil carcinoma were recalculated to evaluate the impact of undetected 3 deg. and 5 deg. head roll. Application of cone-beam CT (CBCT) for patient localization was superior to 2D matching techniques for detecting rotational setup errors. The use of CBCT allowed the determination of translational errors to within 0.5 mm, whereas kV planar was within 1 to 2 mm. Head roll in the axial plane was not easily detected with orthogonal image sets. Compared to the IMRT plans with no head roll, dose-volume histogram analysis demonstrated an average increase in the maximal spinal cord dose of 3.1% and 6.4% for 3 deg. and 5 deg. angles of rotation, respectively. Dose to the contralateral parotid was unchanged with 3 deg. roll and increased by 2.7% with 5 deg. roll. The results of this study show that volumetric setup verification using CBCT can improve bony anatomy setup detection to millimeter accuracy, and is a reliable method to detect head roll. However, the magnitude of possible dose errors due to undetected head roll suggests that CBCT does not need to be performed on a daily basis but rather weekly or bi-weekly to ensure fidelity of the head position with the immobilization system.

  9. Frameless linac-based stereotactic radiosurgery (SRS) for brain metastases: analysis of patient repositioning using a mask fixation system and clinical outcomes.

    PubMed

    Minniti, Giuseppe; Scaringi, Claudia; Clarke, Enrico; Valeriani, Maurizio; Osti, Mattia; Enrici, Riccardo Maurizi

    2011-11-16

    To assess the accuracy of patient repositioning and clinical outcomes of frameless stereotactic radiosurgery (SRS) for brain metastases using a stereotactic mask fixation system. One hundred two patients treated consecutively with frameless SRS as primary treatment at University of Rome Sapienza Sant'Andrea Hospital between October 2008 and April 2010 and followed prospectively were involved in the study. A commercial stereotactic mask fixation system (BrainLab) was used for patient immobilization. A computerized tomography (CT) scan obtained immediately before SRS was used to evaluate the accuracy of patient repositioning in the mask by comparing the isocenter position to the isocenter position established in the planning CT. Deviations of isocenter coordinates in each direction and 3D displacement were calculated. Overall survival, brain control, and local control were estimated using the Kaplan-Meier method calculated from the time of SRS. The mean measured isocenter displacements were 0.12 mm (SD 0.35 mm) in the lateral direction, 0.2 mm (SD 0.4 mm) in the anteroposterior, and 0.4 mm (SD 0.6 mm) in craniocaudal direction. The maximum displacement of 2.1 mm was seen in craniocaudal direction. The mean 3D displacement was 0.5 mm (SD 0.7 mm), being maximum 2.9 mm. The median survival was 15.5 months, and 1-year and 2-year survival rates were 58% and 24%, respectively. Nine patients recurred locally after SRS, with 1-year and 2-year local control rates of 91% and 82%, respectively. Stable extracranial disease (P = 0.001) and KPS > 70 (P = 0.01) were independent predictors of survival. Frameless SRS is an effective treatment in the management of patients with brain metastases. The presented non-invasive mask-based fixation stereotactic system is associated with a high degree of patient repositioning accuracy; however, a careful evaluation is essential since occasional errors up to 3 mm may occur.

  10. Frameless linac-based stereotactic radiosurgery (SRS) for brain metastases: analysis of patient repositioning using a mask fixation system and clinical outcomes

    PubMed Central

    2011-01-01

    Purpose To assess the accuracy of patient repositioning and clinical outcomes of frameless stereotactic radiosurgery (SRS) for brain metastases using a stereotactic mask fixation system. Patients and Methods One hundred two patients treated consecutively with frameless SRS as primary treatment at University of Rome Sapienza Sant'Andrea Hospital between October 2008 and April 2010 and followed prospectively were involved in the study. A commercial stereotactic mask fixation system (BrainLab) was used for patient immobilization. A computerized tomography (CT) scan obtained immediately before SRS was used to evaluate the accuracy of patient repositioning in the mask by comparing the isocenter position to the isocenter position established in the planning CT. Deviations of isocenter coordinates in each direction and 3D displacement were calculated. Overall survival, brain control, and local control were estimated using the Kaplan-Meier method calculated from the time of SRS. Results The mean measured isocenter displacements were 0.12 mm (SD 0.35 mm) in the lateral direction, 0.2 mm (SD 0.4 mm) in the anteroposterior, and 0.4 mm (SD 0.6 mm) in craniocaudal direction. The maximum displacement of 2.1 mm was seen in craniocaudal direction. The mean 3D displacement was 0.5 mm (SD 0.7 mm), being maximum 2.9 mm. The median survival was 15.5 months, and 1-year and 2-year survival rates were 58% and 24%, respectively. Nine patients recurred locally after SRS, with 1-year and 2-year local control rates of 91% and 82%, respectively. Stable extracranial disease (P = 0.001) and KPS > 70 (P = 0.01) were independent predictors of survival. Conclusions Frameless SRS is an effective treatment in the management of patients with brain metastases. The presented non-invasive mask-based fixation stereotactic system is associated with a high degree of patient repositioning accuracy; however, a careful evaluation is essential since occasional errors up to 3 mm may occur. PMID:22085700

  11. Stereotactic linac-based radiosurgery in the treatment of cerebral arteriovenous malformations located deep, involving corpus callosum, motor cortex, or brainstem

    SciTech Connect

    Zabel-du Bois, Angelika . E-mail: A.Zabel@dkfz-heidelberg.de; Milker-Zabel, Stefanie; Huber, Peter; Schlegel, Wolfgang; Debus, Juergen

    2006-03-15

    Purpose: To evaluate patient outcome and obliteration rates after radiosurgery (RS) for cerebral arteriovenous malformations (AVM) located deep, in the motor cortex or brainstem and those involving corpus callosum. Methods and Materials: This analysis is based on 65 patients. AVM classification according to Spetzler-Martin was 13 patients Grade 2, 39 Grade 3, 12 Grade 4, and 1 Grade 5. Median RS-based AVM score was 1.69. Median single dose was 18 Gy. Mean treatment volume was 5.2 cc (range, 0.2-26.5 cc). Forty patients (62%) experienced intracranial hemorrhage before RS. Median follow-up was 3.0 years. Results: Actuarial complete obliteration rate (CO) was 50% and 65% after 3 and 5 years, respectively. CO was significantly higher in AVM <3 cm (p < 0.02) and after doses >18 Gy (p < 0.009). Annual bleeding risk after RS was 4.7%, 3.4%, and 2.7% after 1, 2, and 3 years, respectively. AVM >3 cm (p < 0.01), AVM volume >4 cc (p < 0.009), and AVM score >1.5 (p < 0.02) showed a significant higher bleeding risk. Neurologic dysfunction improved, completely dissolved, or remained stable in 94% of patients. Conclusions: Surgically inaccessible AVM can be successfully treated using RS with acceptable obliteration rates and low risk for late morbidity. The risk of intracranial hemorrhage is reduced after RS and depends on RS-based AVM score.

  12. Linac-based extracranial radiosurgery with Elekta volumetric modulated arc therapy and an anatomy-based treatment planning system: Feasibility and initial experience.

    PubMed

    Cilla, Savino; Deodato, Francesco; Macchia, Gabriella; Digesù, Cinzia; Ianiro, Anna; Viola, Pietro; Craus, Maurizio; Valentini, Vincenzo; Piermattei, Angelo; Morganti, Alessio G

    2016-01-01

    We reported our initial experience in using Elekta volumetric modulated arc therapy (VMAT) and an anatomy-based treatment planning system (TPS) for single high-dose radiosurgery (SRS-VMAT) of liver metastases. This study included a cohort of 12 patients treated with a 26-Gy single fraction. Single-arc VMAT plans were generated with Ergo++ TPS. The prescription isodose surface (IDS) was selected to fulfill the 2 following criteria: 95% of planning target volume (PTV) reached 100% of the prescription dose and 99% of PTV reached a minimum of 90% of prescription dose. A 1-mm multileaf collimator (MLC) block margin was added around the PTV. For a comparison of dose distributions with literature data, several conformity indexes (conformity index [CI], conformation number [CN], and gradient index [GI]) were calculated. Treatment efficiency and pretreatment dosimetric verification were assessed. Early clinical data were also reported. Our results reported that target and organ-at-risk objectives were met for all patients. Mean and maximum doses to PTVs were on average 112.9% and 121.5% of prescribed dose, respectively. A very high degree of dose conformity was obtained, with CI, CN, and GI average values equal to 1.29, 0.80, and 3.63, respectively. The beam-on-time was on average 9.3 minutes, i.e., 0.36min/Gy. The mean number of monitor units was 3162, i.e., 121.6MU/Gy. Pretreatment verification (3%-3mm) showed an optimal agreement with calculated values; mean γ value was 0.27 and 98.2% of measured points resulted with γ < 1. With a median follow-up of 16 months complete response was observed in 12/14 (86%) lesions; partial response was observed in 2/14 (14%) lesions. No radiation-induced liver disease (RILD) was observed in any patients as well no duodenal ulceration or esophagitis or gastric hemorrhage. In conclusion, this analysis demonstrated the feasibility and the appropriateness of high-dose single-fraction SRS-VMAT in liver metastases performed with Elekta VMAT and Ergo++ TPS. Preliminary clinical outcomes showed a high rate of local control and minimum incidence of acute toxicity.

  13. Linac based SBRT for prostate cancer in 5 fractions with VMAT and flattening filter free beams: preliminary report of a phase II study

    PubMed Central

    2013-01-01

    Background To evaluate the feasibility and early side effects of a short course hypo-fractionated SBRT programme with Volumetric Modulated Arc Therapy (VMAT) and Flattening Filter Free (FFF) beams. Methods A prospective phase I-II study, started on February 2012. Inclusion criteria were: age ≤ 80 years, WHO-PS ≤ 2, PSA ≤ 20 ng/ml, histologically proven prostate adenocarcinoma, T1-T2 stage, no distant metastases, no previous surgery other than TURP, no malignant tumours in the previous 5 years, IPSS 0–7. The schedule was 35 Gy in 5 alternative days. SBRT was delivered with RapidArc VMAT, with 10MV FFF photons. Toxicity assessment was performed according to CTCAE v4.0 scale. EPIC questionnaires assessed Quality-of-Life. Neo-adjuvant/concomitant hormonal-therapy was prescribed according to risk classification. SpaceOAR™ gel was optionally implanted to increase the separation space between the prostate and the rectal wall. Results Median follow-up was 11 months (range: 5–16); 40 patients were recruited in the protocol and treated. According to NCCN criteria, 26/40 patients were low-risk and 14/40 were intermediate risk. Median age was 70 years (56–80), median initial PSA was 6.25 ng/ml (0.50-13.43 ng/ml). Median Gleason score was 6 (6–7). All patients completed the treatment as programmed (median 11.8 days (9–22). Acute Toxicities were as follow: Rectum G0: 30/40 cases (75%); G1: 6/40 (15%); G2: 4/40 (10%). Genito-urinary: G0: 16/40 (40%); G1: 8/40 (20%); G2: 16/34 (40%). In two G2 urinary retention cases, intermittent catheter was needed. No acute G3 or greater toxicity was found. Median treatment time was 126 sec (120–136). SpaceOAR™ was implanted in 8 patients. PSA reduction from the pre-treatment value of the marker was documented in all patients. Conclusions Early findings suggest that SBRT with RapidArc and FFF beams for prostate cancer in 5 fractions is feasible and tolerated in acute setting. Longer follow-up is needed for assessment of late toxicity and outcome. PMID:23835141

  14. Linac based SBRT for prostate cancer in 5 fractions with VMAT and flattening filter free beams: preliminary report of a phase II study.

    PubMed

    Alongi, Filippo; Cozzi, Luca; Arcangeli, Stefano; Iftode, Cristina; Comito, Tiziana; Villa, Elisa; Lobefalo, Francesca; Navarria, Pierina; Reggiori, Giacomo; Mancosu, Pietro; Clerici, Elena; Fogliata, Antonella; Tomatis, Stefano; Taverna, Gianluigi; Graziotti, Pierpaolo; Scorsetti, Marta

    2013-07-08

    To evaluate the feasibility and early side effects of a short course hypo-fractionated SBRT programme with Volumetric Modulated Arc Therapy (VMAT) and Flattening Filter Free (FFF) beams. A prospective phase I-II study, started on February 2012. Inclusion criteria were: age ≤ 80 years, WHO-PS ≤ 2, PSA ≤ 20 ng/ml, histologically proven prostate adenocarcinoma, T1-T2 stage, no distant metastases, no previous surgery other than TURP, no malignant tumours in the previous 5 years, IPSS 0-7. The schedule was 35 Gy in 5 alternative days. SBRT was delivered with RapidArc VMAT, with 10MV FFF photons. Toxicity assessment was performed according to CTCAE v4.0 scale. EPIC questionnaires assessed Quality-of-Life. Neo-adjuvant/concomitant hormonal-therapy was prescribed according to risk classification. SpaceOAR™ gel was optionally implanted to increase the separation space between the prostate and the rectal wall. Median follow-up was 11 months (range: 5-16); 40 patients were recruited in the protocol and treated. According to NCCN criteria, 26/40 patients were low-risk and 14/40 were intermediate risk. Median age was 70 years (56-80), median initial PSA was 6.25 ng/ml (0.50-13.43 ng/ml). Median Gleason score was 6 (6-7). All patients completed the treatment as programmed (median 11.8 days (9-22). Acute Toxicities were as follow: Rectum G0: 30/40 cases (75%); G1: 6/40 (15%); G2: 4/40 (10%). Genito-urinary: G0: 16/40 (40%); G1: 8/40 (20%); G2: 16/34 (40%). In two G2 urinary retention cases, intermittent catheter was needed. No acute G3 or greater toxicity was found. Median treatment time was 126 sec (120-136). SpaceOAR™ was implanted in 8 patients. PSA reduction from the pre-treatment value of the marker was documented in all patients. Early findings suggest that SBRT with RapidArc and FFF beams for prostate cancer in 5 fractions is feasible and tolerated in acute setting. Longer follow-up is needed for assessment of late toxicity and outcome.

  15. Linac-based on-board imaging feasibility and the dosimetric consequences of head roll in head-and-neck IMRT plans.

    PubMed

    Kim, Gwe-Ya; Pawlicki, Todd; Le, Quynh-Thu; Luxton, Gary

    2008-01-01

    Kilovoltage imaging systems on linear accelerators are used for patient localization in many clinics. The purpose of this work is to assess on-board imaging (OBI) detection of systematic setup errors and in particular, the dosimetric consequences of undetected head roll in head-and-neck intensity modulated radiation therapy (IMRT) plans when using these systems. The system used in this study was the Trilogy linear accelerator and associated software (Varian Medical Systems, Palo Alto, CA). Accuracy of OBI localization was evaluated using an anthropomorphic head phantom. The head phantom is rigidly attached to a specially designed positioning device with 5 degrees of freedom, 3 translational and 2 rotational in the axial and coronal planes. Simulated setup errors were 3 degrees and 5 degrees rotations in the axial plane and displacements of 5 mm in the left-right, anterior-posterior, and superior-inferior directions. The coordinates set by the positioning device were compared with the coordinates obtained as measured by using the image matching tools of paired 2-dimensional (2D) orthogonal image matching, and 3D cone-beam computed tomography (CT) volume matching. In addition, 6 physician-approved IMRT plans of nasopharynx and tonsil carcinoma were recalculated to evaluate the impact of undetected 3 degrees and 5 degrees head roll. Application of cone-beam CT (CBCT) for patient localization was superior to 2D matching techniques for detecting rotational setup errors. The use of CBCT allowed the determination of translational errors to within 0.5 mm, whereas kV planar was within 1 to 2 mm. Head roll in the axial plane was not easily detected with orthogonal image sets. Compared to the IMRT plans with no head roll, dose-volume histogram analysis demonstrated an average increase in the maximal spinal cord dose of 3.1% and 6.4% for 3 degrees and 5 degrees angles of rotation, respectively. Dose to the contralateral parotid was unchanged with 3 degrees roll and increased by 2.7% with 5 degrees roll. The results of this study show that volumetric setup verification using CBCT can improve bony anatomy setup detection to millimeter accuracy, and is a reliable method to detect head roll. However, the magnitude of possible dose errors due to undetected head roll suggests that CBCT does not need to be performed on a daily basis but rather weekly or bi-weekly to ensure fidelity of the head position with the immobilization system.

  16. Frameless LINAC-based stereotactic radiation therapy to brain metastasis resection cavity without whole-brain radiation therapy: A systematic review.

    PubMed

    Kaidar-Person, Orit; Zagar, Timothy M; Ewend, Matthew; Tzuk-Shina, Tzahala; Marks, Lawrence B

    2016-01-01

    The aim of this systematic review was to summarize the findings from the published data of frameless stereotactic radiation therapy (RT) to the resection cavity delivered with nonrobotic linear accelerator in patients with brain metastases. The studies cited in this systematic review were identified through a search of the PubMed database, using the search terms: "stereotactic [Title/Abstract]" and "Brain [Title/Abstract]," and "Metas* [Title/Abstract]." The search was unlimited to language and publication year. A total of 9 studies were included in our review. Stereotactic RT to the resection cavity appears to provide excellent local control rates that are comparable to framed stereotactic RT. There are various factors that influence local control. Distant intracranial control rates are poor with the use of postoperative stereotactic RT compared with local treatment (surgery or stereotactic RT) plus whole-brain RT. Stereotactic RT to the resection cavity appears to provide good local control rates and poor distant intracranial control. Postoperative treatment should be discussed by a multidisciplinary team and tailored to each case individually. Published by Elsevier Inc.

  17. Monte Carlo simulation estimates of neutron doses to critical organs of a patient undergoing 18 MV x-ray LINAC-based radiotherapy

    SciTech Connect

    Barquero, R.; Edwards, T.M.; Iniguez, M. P.; Vega-Carrillo, H.R.

    2005-12-15

    Absorbed photoneutron dose to patients undergoing 18 MV x-ray therapy was studied using Monte Carlo simulations based on the MCNPX code. Two separate transport simulations were conducted, one for the photoneutron contribution and another for neutron capture gamma rays. The phantom model used was of a female patient receiving a four-field pelvic box treatment. Photoneutron doses were determinate to be higher for organs and tissues located inside the treatment field, especially those closest to the patient's skin. The maximum organ equivalent dose per x-ray treatment dose achieved within each treatment port was 719 {mu}Sv/Gy to the rectum (180 deg. field), 190 {mu}Sv/Gy to the intestine wall (0 deg. field), 51 {mu}Sv/Gy to the colon wall (90 deg. field), and 45 {mu}Sv/Gy to the skin (270 deg. field). The maximum neutron equivalent dose per x-ray treatment dose received by organs outside the treatment field was 65 {mu}Sv/Gy to the skin in the antero-posterior field. A mean value of 5{+-}2 {mu}Sv/Gy was obtained for organs distant from the treatment field. Distant organ neutron equivalent doses are all of the same order of magnitude and constitute a good estimate of deep organ neutron equivalent doses. Using the risk assessment method of the ICRP-60 report, the greatest likelihood of fatal secondary cancer for a 70 Gy dose is estimated to be 0.02% for the pelvic postero-anterior field, the rectum being the organ representing the maximum contribution of 0.011%.

  18. Differences in Clinical Results After LINAC-Based Single-Dose Radiosurgery Versus Fractionated Stereotactic Radiotherapy for Patients With Vestibular Schwannomas

    SciTech Connect

    Combs, Stephanie E.; Welzel, Thomas; Schulz-Ertner, Daniela; Huber, Peter E.; Debus, Juergen

    2010-01-15

    Purpose: To evaluate the outcomes of patients with vestibular schwannoma (VS) treated with fractionated stereotactic radiotherapy (FSRT) vs. those treated with stereotactic radiosurgery (SRS). Methods and Materials: This study is based on an analysis of 200 patients with 202 VSs treated with FSRT (n = 172) or SRS (n = 30). Patients with tumor progression and/or progression of clinical symptoms were selected for treatment. In 165 out of 202 VSs (82%), RT was performed as the primary treatment for VS, and for 37 VSs (18%), RT was conducted for tumor progression after neurosurgical intervention. For patients receiving FSRT, a median total dose of 57.6 Gy was prescribed, with a median fractionation of 5 x 1.8 Gy per week. For patients who underwent SRS, a median single dose of 13 Gy was prescribed to the 80% isodose. Results: FSRT and SRS were well tolerated. Median follow-up time was 75 months. Local control was not statistically different for both groups. The probability of maintaining the pretreatment hearing level after SRS with doses of <=13 Gy was comparable to that of FSRT. The radiation dose for the SRS group (<=13 Gy vs. >13 Gy) significantly influenced hearing preservation rates (p = 0.03). In the group of patients treated with SRS doses of <=13 Gy, cranial nerve toxicity was comparable to that of the FSRT group. Conclusions: FSRT and SRS are both safe and effective alternatives for the treatment of VS. Local control rates are comparable in both groups. SRS with doses of <=13 Gy is a safe alternative to FSRT. While FSRT can be applied safely for the treatment of VSs of all sizes, SRS should be reserved for smaller lesions.

  19. Integrated Tiger Series of electron/photon Monte Carlo transport codes: a user's guide for use on IBM mainframes

    SciTech Connect

    Kirk, B.L.

    1985-12-01

    The ITS (Integrated Tiger Series) Monte Carlo code package developed at Sandia National Laboratories and distributed as CCC-467/ITS by the Radiation Shielding Information Center (RSIC) at Oak Ridge National Laboratory (ORNL) consists of eight codes - the standard codes, TIGER, CYLTRAN, ACCEPT; the P-codes, TIGERP, CYLTRANP, ACCEPTP; and the M-codes ACCEPTM, CYLTRANM. The codes have been adapted to run on the IBM 3081, VAX 11/780, CDC-7600, and Cray 1 with the use of the update emulator UPEML. This manual should serve as a guide to a user running the codes on IBM computers having 370 architecture. The cases listed were tested on the IBM 3033, under the MVS operating system using the VS Fortran Level 1.3.1 compiler.

  20. Result of Monte-Carlo simulation of electron-photon cascades in lead and layers of lead-scintillator

    NASA Technical Reports Server (NTRS)

    Wasilewski, A.; Krys, E.

    1985-01-01

    Results of Monte-Carlo simulation of electromagnetic cascade development in lead and lead-scintillator sandwiches are analyzed. It is demonstrated that the structure function for core approximation is not applicable in the case in which the primary energy is higher than 100 GeV. The simulation data has shown that introducing an inhomogeneous chamber structure results in subsequent reduction of secondary particles.

  1. Detection of dark states in two-dimensional electronic photon-echo signals via ground-state coherence

    SciTech Connect

    Egorova, Dassia

    2015-06-07

    Several recent experiments report on possibility of dark-state detection by means of so called beating maps of two-dimensional photon-echo spectroscopy [Ostroumov et al., Science 340, 52 (2013); Bakulin et al., Ultrafast Phenomena XIX (Springer International Publishing, 2015)]. The main idea of this detection scheme is to use coherence induced upon the laser excitation as a very sensitive probe. In this study, we investigate the performance of ground-state coherence in the detection of dark electronic states. For this purpose, we simulate beating maps of several models where the excited-state coherence can be hardly detected and is assumed not to contribute to the beating maps. The models represent strongly coupled electron-nuclear dynamics involving avoided crossings and conical intersections. In all the models, the initially populated optically accessible excited state decays to a lower-lying dark state within few hundreds femtoseconds. We address the role of Raman modes and of interstate-coupling nature. Our findings suggest that the presence of low-frequency Raman active modes significantly increases the chances for detection of dark states populated via avoided crossings, whereas conical intersections represent a more challenging task.

  2. Detection of dark states in two-dimensional electronic photon-echo signals via ground-state coherence.

    PubMed

    Egorova, Dassia

    2015-06-07

    Several recent experiments report on possibility of dark-state detection by means of so called beating maps of two-dimensional photon-echo spectroscopy [Ostroumov et al., Science 340, 52 (2013); Bakulin et al., Ultrafast Phenomena XIX (Springer International Publishing, 2015)]. The main idea of this detection scheme is to use coherence induced upon the laser excitation as a very sensitive probe. In this study, we investigate the performance of ground-state coherence in the detection of dark electronic states. For this purpose, we simulate beating maps of several models where the excited-state coherence can be hardly detected and is assumed not to contribute to the beating maps. The models represent strongly coupled electron-nuclear dynamics involving avoided crossings and conical intersections. In all the models, the initially populated optically accessible excited state decays to a lower-lying dark state within few hundreds femtoseconds. We address the role of Raman modes and of interstate-coupling nature. Our findings suggest that the presence of low-frequency Raman active modes significantly increases the chances for detection of dark states populated via avoided crossings, whereas conical intersections represent a more challenging task.

  3. An R-matrix approach to electron-photon-molecule collisions: photoelectron angular distributions from aligned molecules

    NASA Astrophysics Data System (ADS)

    Harvey, Alex G.; Brambila, Danilo S.; Morales, Felipe; Smirnova, Olga

    2014-11-01

    We present a new extension of the UKRmol electron-molecule scattering code suite, which allows one to compute ab initio photoionization and photorecombination amplitudes for complex molecules, resolved both on the molecular alignment (orientation) and the emission angle and energy of the photoelectron. We illustrate our approach using CO2 as an example, and analyze the importance of multi-channel effects by performing our calculations at different, increasing levels of complexity. We benchmark our method by comparing the results of our calculations with experimental data and with theoretical calculations available in the literature.

  4. Dosimetric comparison of intensity modulated radiotherapy isocentric field plans and field in field (FIF) forward plans in the treatment of breast cancer.

    PubMed

    Al-Rahbi, Zakiya Salem; Al Mandhari, Zahid; Ravichandran, Ramamoorthy; Al-Kindi, Fatma; Davis, Cheriyathmanjiyil Anthony; Bhasi, Saju; Satyapal, Namrata; Rajan, Balakrishnan

    2013-01-01

    The present study is aimed at comparing the planning and delivery efficiency between three-dimensional conformal radiotherapy (3D-CRT), field-in-field, forward planned, intensity modulated radiotherapy (FIF-FP-IMRT), and inverse planned intensity modulated radiotherapy (IP-IMRT). Treatment plans of 20 patients with left-sided breast cancer, 10 post-mastectomy treated to a prescribed dose of 45 Gy to the chest wall in 20 fractions, and 10 post-breast-conserving surgery to a prescribed dose of 50 Gy to the whole breast in 25 fractions, with 3D-CRT were selected. The FiF-FP-IMRT plans were created by combining two open fields with three to four segments in two tangential beam directions. Eight different beam directions were chosen to create IP-IMRT plans and were inversely optimized. The homogeneity of dose to planning target volume (PTV) and the dose delivered to heart and contralateral breast were compared among the techniques in all the 20 patients. All the three radiotherapy techniques achieved comparable radiation dose delivery to PTV-95% of the prescribed dose covering > 95% of the breast PTV. The mean volume of PTV receiving 105% (V105) of the prescribed dose was 1.7% (range 0-6.8%) for IP-IMRT, 1.9% for FP-IMRT, and 3.7% for 3D-CRT. The homogeneity and conformity indices (HI and CI) were similar for 3D-CRT and FP-IMRT, whereas the IP-IMRT plans had better conformity index at the cost of less homogeneity. The 3D-CRT and FiF-FP-IMRT plans achieved similar sparing of critical organs. The low-dose volumes (V5Gy) in the heart and lungs were larger in IP-IMRT than in the other techniques. The value of the mean dose to the ipsilateral lung was higher for IP-IMRT than the values for with FiF-FP-IMRT and 3D-CRT. In the current study, the relative volume of contralateral breast receiving low doses (0.01, 0.6, 1, and 2Gy) was significantly lower for the FiF-FP-IMRT and 3D-CRT plans than for the IP-IMRT plan. Compared with 3D-CRT and IP-IMRT, FiF-FP-IMRT proved to be a simple and efficient planning technique for breast irradiation. It provided dosimetric advantages, significantly reducing the size of the hot spot and minimally improving the coverage of the target volume. In addition, it was felt that FiF-FP-IMRT required less planning time and easy field placements.

  5. Dosimetric comparison of intensity modulated radiotherapy isocentric field plans and field in field (FIF) forward plans in the treatment of breast cancer

    PubMed Central

    Al-Rahbi, Zakiya Salem; Al Mandhari, Zahid; Ravichandran, Ramamoorthy; Al-Kindi, Fatma; Davis, Cheriyathmanjiyil Anthony; Bhasi, Saju; Satyapal, Namrata; Rajan, Balakrishnan

    2013-01-01

    The present study is aimed at comparing the planning and delivery efficiency between three-dimensional conformal radiotherapy (3D-CRT), field-in-field, forward planned, intensity modulated radiotherapy (FIF-FP-IMRT), and inverse planned intensity modulated radiotherapy (IP-IMRT). Treatment plans of 20 patients with left-sided breast cancer, 10 post-mastectomy treated to a prescribed dose of 45 Gy to the chest wall in 20 fractions, and 10 post-breast-conserving surgery to a prescribed dose of 50 Gy to the whole breast in 25 fractions, with 3D-CRT were selected. The FiF-FP-IMRT plans were created by combining two open fields with three to four segments in two tangential beam directions. Eight different beam directions were chosen to create IP-IMRT plans and were inversely optimized. The homogeneity of dose to planning target volume (PTV) and the dose delivered to heart and contralateral breast were compared among the techniques in all the 20 patients. All the three radiotherapy techniques achieved comparable radiation dose delivery to PTV-95% of the prescribed dose covering > 95% of the breast PTV. The mean volume of PTV receiving 105% (V105) of the prescribed dose was 1.7% (range 0-6.8%) for IP-IMRT, 1.9% for FP-IMRT, and 3.7% for 3D-CRT. The homogeneity and conformity indices (HI and CI) were similar for 3D-CRT and FP-IMRT, whereas the IP-IMRT plans had better conformity index at the cost of less homogeneity. The 3D-CRT and FiF-FP-IMRT plans achieved similar sparing of critical organs. The low-dose volumes (V5Gy) in the heart and lungs were larger in IP-IMRT than in the other techniques. The value of the mean dose to the ipsilateral lung was higher for IP-IMRT than the values for with FiF-FP-IMRT and 3D-CRT. In the current study, the relative volume of contralateral breast receiving low doses (0.01, 0.6, 1, and 2Gy) was significantly lower for the FiF-FP-IMRT and 3D-CRT plans than for the IP-IMRT plan. Compared with 3D-CRT and IP-IMRT, FiF-FP-IMRT proved to be a simple and efficient planning technique for breast irradiation. It provided dosimetric advantages, significantly reducing the size of the hot spot and minimally improving the coverage of the target volume. In addition, it was felt that FiF-FP-IMRT required less planning time and easy field placements. PMID:23531607

  6. In-vivo dosimetry with Gafchromic films for multi-isocentric VMAT irradiation of total marrow lymph-nodes: a feasibility study.

    PubMed

    Mancosu, Pietro; Navarria, Pierina; Reggiori, Giacomo; Cozzi, Luca; Fogliata, Antonella; Gaudino, Anna; Lobefalo, Francesca; Paganini, Lucia; Palumbo, Valentina; Sarina, Barbara; Stravato, Antonella; Castagna, Luca; Tomatis, Stefano; Scorsetti, Marta

    2015-04-12

    Total marrow (lymph-nodes) irradiation (TMI-TMLI) by volumetric modulated arc therapy (VMAT) was shown to be feasible by dosimetric feasibility studies. It was demonstrated that several partially overlapping arcs with different isocenters are required to achieve the desired coverage of the hematopoietic or lymphoid tissues targets and to spare the neighbouring healthy tissues. The effect of isocenter shifts was investigated with the treatment planning system but an in- vivo verification of the procedure was not carried out. The objective of this study was the in-vivo verification of the consistency between the delivered and planned doses using bi-dimensional GafChromic EBT3 films. In a first phase a phantom study was carried out to quantify the uncertainties under controlled conditions. In a second phase three patients treated with TMLI were enrolled for in-vivo dosimetry. The dose prescription was 2Gy in single fraction. Ten arcs paired on 4-6 isocenters were used to cover the target. Cone Beam Computed Tomography (CBCT) was used to verify the patient positioning at each isocenter. GafChromic EBT3 films were placed below the patient on the top of a dedicated immobilization system specifically designed. The dose maps measured with the EBT3 films were compared with the corresponding calculations along the patient support couch. Gamma Agreement Index (GAI) with dose difference of 5% and distance to agreement of 5 mm was computed. In the phantom study, optimal target coverage and healthy tissue sparing was observed. GAI(5%,5 mm) was 99.4%. For the patient-specific measurements, GAI(5%,5 mm) was greater than 95% and GAI (5%,3 mm) > 90% for all patients. In vivo measurements demonstrated the delivered dose to be in good agreement with the planned one for the TMI-TMLI protocol where partially overlapping arcs with different isocenters are required.

  7. A pulsed electron-photon fluorescence diagnostic technique for temperature and specie concentration measurement at points in relatively dense, unseedded air flows

    NASA Technical Reports Server (NTRS)

    Muntz, E. P.; Kunc, J. A.; Erwin, D. A.

    1987-01-01

    An analysis is presented on the use of the fluorescence stimulated by combined pulsed electron and photon beams for the study of gas flows up to densities equivalent to an altitude of about 20 km (number density of about 3 x 10 to the 18th/cu cm). The electron beam acts as a pump, requiring no seed gas, to provide a localized concentration of ions or excited state neutrals that can be probed by saturation optical pulses. A short pulse (10ns) electron beam can be used by itself to provide effectively quench-free emission up to number densities of around 10 to the 18th/cm, but is is difficult to maintain satisfactory spatial resolution at this high density. The use of a nearly simultaneous strong optical pulse increases the flexibility of the diagnostic technique, permitting use at densities greater than 10 to the 18th/cu cm with good spatial resolution. The use of flash X-ray sources combined with optical probing also appears promising for densities above 10 to the 19th/cu cm.

  8. A pulsed electron-photon fluorescence diagnostic technique for temperature and specie concentration measurement at points in relatively dense, unseedded air flows

    NASA Technical Reports Server (NTRS)

    Muntz, E. P.; Kunc, J. A.; Erwin, D. A.

    1987-01-01

    An analysis is presented on the use of the fluorescence stimulated by combined pulsed electron and photon beams for the study of gas flows up to densities equivalent to an altitude of about 20 km (number density of about 3 x 10 to the 18th/cu cm). The electron beam acts as a pump, requiring no seed gas, to provide a localized concentration of ions or excited state neutrals that can be probed by saturation optical pulses. A short pulse (10ns) electron beam can be used by itself to provide effectively quench-free emission up to number densities of around 10 to the 18th/cm, but is is difficult to maintain satisfactory spatial resolution at this high density. The use of a nearly simultaneous strong optical pulse increases the flexibility of the diagnostic technique, permitting use at densities greater than 10 to the 18th/cu cm with good spatial resolution. The use of flash X-ray sources combined with optical probing also appears promising for densities above 10 to the 19th/cu cm.

  9. Boosting the tumor bed from deep-seated tumors in early-stage breast cancer: a planning study between electron, photon, and proton beams.

    PubMed

    Toscas, José I; Linero, Dolors; Rubio, Isabel; Hidalgo, Alberto; Arnalte, Raquel; Escudé, Lluís; Cozzi, Luca; Fogliata, Antonella; Miralbell, Raymond

    2010-08-01

    To assess the potential dosimetric advantages and drawbacks of photon beams (modulated or not), electron beams (EB), and protons as a boost for the tumor bed in deep-seated early-stage breast cancer. Planning CTs of 14 women with deep-seated tumors (i.e., > or =4 cm depth) were selected. The clinical target volume (CTV) was defined as the area of architectural distortion surrounded by surgical clips. The planning treatment volume (PTV) was the CTV plus 1cm margin. A dose of 16 Gy in 2 Gy fractions was prescribed. Organs at risk (OARs) were heart, lungs, breasts, and a 5-mm thick skin segment on the breast surface. Dose-volume metrics were defined to quantify the quality of concurrent treatment plans assessing target coverage and sparing of OAR. The following treatment techniques were assessed: photon beams with either static 3D-conformal, dynamic arc (DCA), static gantry intensity-modulated beams (IMRT), or RapidArc (RA); a single conformal EB; and intensity-modulated proton beams (IMPT). The goal for this planning effort was to cover 100% of the CTV with 95% of the prescribed dose and to minimize the volume inside the CTV receiving >107% of the dose. All techniques but DCA and EB achieved the planning objective for the CTV with an inhomogeneity ranging from 2% to 11%. RA showed the best conformity, EB the worst. Contra-lateral breast and lung were spared by all techniques with mean doses <0.5 Gy (zero for protons). The ipsi-lateral lung received a mean dose <10% of that prescribed with photon beams and <2% with IMPT, increasing to 17% with EB. The heart, in left-sided breast tumors, received also the highest dose with EB. The skin was best protected with RA with a mean dose of 5.4 Gy and V(15Gy)=2.4%. Boosting the tumor bed in early-stage breast cancer with optimized photon or proton beams may be preferred to EB especially for deep-seated targets. The marked OAR (i.e., ipsi-lateral breast, lung, heart, and skin surface) dose-sparing effect may allow for a potential long-term toxicity risk reduction and better cosmesis. DCA or RA may also be considered alternative treatment options for patients eligible for accelerated partial breast irradiation trials. Copyright 2010 Elsevier Ireland Ltd. All rights reserved.

  10. Determination of dose-build-up thickness for absorbed dose measurement in high energy electron-photon radiation at electron storage rings.

    PubMed

    Nair, Haridas G; Dev, Vipin; Nayak, M K; Thakkar, K K; Sarkar, P K; Sharma, D N

    2006-01-01

    Radiation field during accidental electron beam loss near electron storage rings comprises of high-energy electrons and bremsstrahlung photons. Due to high-energy nature of the radiation, the absorbed dose is expected to build up with depth of the body of an exposed worker and hence absorbed dose measurements in 30 cm water/tissue equivalent phantom is essential. Carrying out the measurements with in such phantoms is not practically feasible for routine applications and hence the use of an equivalent solid material around the dosemeters would be convenient. Monte Carlo calculations have been carried out in order to determine the dose-build-up thickness required in copper and lead, corresponding to the maximum absorbed within 30 cm depth of water in such radiation fields. Equivalent build-up thickness calculated for a case was verified by measurement using an ion chamber detector. The results are found to be in agreement within +/-20%.

  11. The lateral distributions of charged particles of energy greater than 0.3 E sub crit in electron-photon cascades in lead and air

    NASA Technical Reports Server (NTRS)

    Wasilewski, A.; Krys, E.

    1985-01-01

    In recent investigations, both theoretical and experimental, the agreement between cascade theory and experimental data is pointed out. The radial distributions obtained from the Monte Carlo simulation are compared ith the results of the analytical theory for all particles in cascades. The data on the mean radius of electron lateral distribution in air are compared with those in lead.

  12. Dynamics of multiple ionization of atoms and molecules by electron, photon, and ion impact—investigated by the COLTRIMS imaging method

    NASA Astrophysics Data System (ADS)

    Schmidt-Böcking, H.; Schmidt, L.; Weber, Th.; Mergel, V.; Jagutzki, O.; Czasch, A.; Hagmann, S.; Doerner, R.; Demkov, Y.; Jahnke, T.; Prior, M.; Cocke, C. L.; Osipov, T.; Landers, A.

    2004-10-01

    Fully differential cross-sections in momentum space for multiple ionization processes of atoms and molecules have been investigated by a multi-coincidence imaging technique, called COLTRIMS (cold target recoil ion momentum spectroscopy) (J. Phys. B 30 (1997) 2917; Nucl. Instrum. Methods B 108 (1996) 425; In: Ullrich, J., Shevelko, V.P. (Eds.), Many Particle Quantum Dynamics in Atomic Fragmentation, Series Atomic, Optical, and Plasma Physics, Vol. 35. Springer, Berlin, 2003; Phys. Rep. 330 (2000) 95). This technique is as powerful as the bubble chamber system in high-energy physics. It has opened a new observation window into the hidden world of many-particle dynamics: correlated many-particle dynamics in Coulombic systems can now be experimentally approached with unprecedented completeness and precision. The principle of the method, namely measuring the momentum of the emitted charged particles from an atomic or molecular fragmentation process, is as simple as determining the trajectory of a thrown stone. From knowing the position from where the stone was slung and where it hits the target, as well as measuring its time-of-flight, the trajectory of the stone and thus its initial velocity vector can be determined precisely. Furthermore, in order to achieve good precision we have to know whether the person, who throws the stone, was at rest in the frame of observation or with which relative velocity this person was moving. Thus, to obtain optimal momentum resolution for the exploding fragments one has to bring the fragmenting object to a complete rest in the frame of measurement before the reaction occurs, i.e. if the object is a gas atom or molecule one has to cool it down to sub-milli Kelvin temperatures.

  13. Measurement of thermal neutron cross-section and resonance integral for the 165Ho(n,γ) 166gHo reaction using electron linac-based neutron source

    NASA Astrophysics Data System (ADS)

    Nguyen, Van Do; Pham, Duc Khue; Kim, Tien Thanh; Kim, Guinyun; Lee, Manwoo; Kim, Kyung Sook; Kang, Heung-Sik; Cho, Moo-Hyun; Ko, In Soo; Namkung, Won

    2011-01-01

    The thermal neutron cross-section and the resonance integral of the 165Ho(n,γ) 166gHo reaction have been measured by the activation method using a 197Au(n,γ) 198Au monitor reaction as a single comparator. The high-purity natural Ho and Au foils with and without a cadmium shield case of 0.5 mm thickness were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the activated foils were measured with a calibrated p-type high-purity Ge detector. The correction factors for the γ-ray attenuation ( Fg), the thermal neutron self-shielding ( Gth), the resonance neutron self-shielding ( Gepi) effects, and the epithermal neutron spectrum shape factor ( α) were taken into account. The thermal neutron cross-section for the 165Ho(n,γ) 166gHo reaction has been determined to be 59.7 ± 2.5 barn, relative to the reference value of 98.65 ± 0.09 barn for the 197Au(n,γ) 198Au reaction. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral for the 165Ho(n,γ) 166gHo reaction is 671 ± 47 barn, which is determined relative to the reference value of 1550 ± 28 barn for the 197Au(n,γ) 198Au reaction. The present results are, in general, good agreement with most of the previously reported data within uncertainty limits.

  14. Monte Carlo study of Siemens PRIMUS photoneutron production.

    PubMed

    Pena, J; Franco, L; Gómez, F; Iglesias, A; Pardo, J; Pombar, M

    2005-12-21

    Neutron production in radiotherapy facilities has been studied from the early days of modern linacs. Detailed studies are now possible using photoneutron capabilities of general-purpose Monte Carlo codes at energies of interest in medical physics. The present work studies the effects of modelling different accelerator head and room geometries on the neutron fluence and spectra predicted via Monte Carlo. The results from the simulation of a 15 MV Siemens PRIMUS linac show an 80% increase in the fluence scored at the isocentre when, besides modelling the components necessary for electron/photon simulations, other massive accelerator head components are included. Neutron fluence dependence on inner treatment room volume is analysed showing that thermal neutrons have a 'gaseous' behaviour and then a 1/V dependence. Neutron fluence maps for three energy ranges, fast (E > 0.1 MeV), epithermal (1 eV < E < 0.1 MeV) and thermal (E < 1 eV), are also presented and the influence of the head components on them is discussed.

  15. Monte Carlo study of Siemens PRIMUS photoneutron production

    NASA Astrophysics Data System (ADS)

    Pena, J.; Franco, L.; Gómez, F.; Iglesias, A.; Pardo, J.; Pombar, M.

    2005-12-01

    Neutron production in radiotherapy facilities has been studied from the early days of modern linacs. Detailed studies are now possible using photoneutron capabilities of general-purpose Monte Carlo codes at energies of interest in medical physics. The present work studies the effects of modelling different accelerator head and room geometries on the neutron fluence and spectra predicted via Monte Carlo. The results from the simulation of a 15 MV Siemens PRIMUS linac show an 80% increase in the fluence scored at the isocentre when, besides modelling the components neccessary for electron/photon simulations, other massive accelerator head components are included. Neutron fluence dependence on inner treatment room volume is analysed showing that thermal neutrons have a 'gaseous' behaviour and then a 1/V dependence. Neutron fluence maps for three energy ranges, fast (E > 0.1 MeV), epithermal (1 eV < E < 0.1 MeV) and thermal (E < 1 eV), are also presented and the influence of the head components on them is discussed.

  16. Quality Assurance Results for a Commercial Radiosurgery System: A Communication.

    PubMed

    Ruschin, Mark; Lightstone, Alexander; Beachey, David; Wronski, Matt; Babic, Steven; Yeboah, Collins; Lee, Young; Soliman, Hany; Sahgal, Arjun

    2015-10-01

    The purpose of this communication is to inform the radiosurgery community of quality assurance (QA) results requiring attention in a commercial FDA-approved linac-based cone stereo-tactic radiosurgery (SRS) system. Standard published QA guidelines as per the American Association of Physics in Medicine (AAPM) were followed during the SRS system's commissioning process including end-to-end testing, cone concentricity testing, image transfer verification, and documentation. Several software and hardware deficiencies that were deemed risky were uncovered during the process and QA processes were put in place to mitigate these risks during clinical practice. In particular, the present work focuses on daily cone concentricity testing and commissioning-related findings associated with the software. Cone concentricity/alignment is measured daily using both optical light field inspection, as well as quantitative radiation field tests with the electronic portal imager. In 10 out of 36 clini-cal treatments, adjustments to the cone position had to be made to align the cone with the collimator axis to less than 0.5 mm and on two occasions the pre-adjustment measured offset was 1.0 mm. Software-related errors discovered during commissioning included incorrect transfer of the isocentre in DICOM coordinates, improper handling of non-axial image sets, and complex handling of beam data, especially for multi-target treatments. QA processes were established to mitigate the occurrence of the software errors. With proper QA processes, the reported SRS system complies with tolerances set out in established guidelines. Discussions with the vendor are ongoing to address some of the hardware issues related to cone alignment. © The Author(s) 2014.

  17. Noninvasive referencing of intraocular tumors for external beam radiation therapy using optical coherence tomography: A proof of concept

    SciTech Connect

    Rüegsegger, Michael B.; Steiner, Patrick; Kowal, Jens H.; Geiser, Dominik; Pica, Alessia; Aebersold, Daniel M.

    2014-08-15

    Purpose: External beam radiation therapy is currently considered the most common treatment modality for intraocular tumors. Localization of the tumor and efficient compensation of tumor misalignment with respect to the radiation beam are crucial. According to the state of the art procedure, localization of the target volume is indirectly performed by the invasive surgical implantation of radiopaque clips or is limited to positioning the head using stereoscopic radiographies. This work represents a proof-of-concept for direct and noninvasive tumor referencing based on anterior eye topography acquired using optical coherence tomography (OCT). Methods: A prototype of a head-mounted device has been developed for automatic monitoring of tumor position and orientation in the isocentric reference frame for LINAC based treatment of intraocular tumors. Noninvasive tumor referencing is performed with six degrees of freedom based on anterior eye topography acquired using OCT and registration of a statistical eye model. The proposed prototype was tested based on enucleated pig eyes and registration accuracy was measured by comparison of the resulting transformation with tilt and torsion angles manually induced using a custom-made test bench. Results: Validation based on 12 enucleated pig eyes revealed an overall average registration error of 0.26 ± 0.08° in 87 ± 0.7 ms for tilting and 0.52 ± 0.03° in 94 ± 1.4 ms for torsion. Furthermore, dependency of sampling density on mean registration error was quantitatively assessed. Conclusions: The tumor referencing method presented in combination with the statistical eye model introduced in the past has the potential to enable noninvasive treatment and may improve quality, efficacy, and flexibility of external beam radiotherapy of intraocular tumors.

  18. Terrestrial gamma ray flashes from electron avalanches in thunderstorms - the detailed structure and time evolution of electron, photon, optical and radio emission - results from a new simulation software package

    NASA Astrophysics Data System (ADS)

    Connell, P. H.

    2013-12-01

    To design the MXGS coded mask imager of the ASIM mission to the ISS, to detect and locate TGF gamma-rays, a first order software package was written at UV to simulate the vertical expansion of gamma-ray photons from 15-20 km altitudes up to 300-600 km orbital altitudes, to make some estimate of the probable TGF spectra and diffuse beam structure that might be observed by MXGS. A new software package includes the simulation of the Runaway Electron Avalanche (REA) origin of TGFs by electron ionization and Bremsstrahlung scattering and photon emission. It uses the standard KeV-MeV scattering physics of electron and photon interactions, close range Moller electron ionization, Binary-Electron-Bethe models of electron scattering, positron Bhabha scattering and annihilation, electron excitation and photon emission. It also uses a super particle spatial mesh system to control particle-momentum flux densities, electric field evolution and exponential avalanche growth and falloff. The package takes care of all high energy scattering physics, leaving the user free to concentrate on defining the three components of scattering medium, electric-magnetic field geometry, and free electron flux field geometry whose details are the main unknown in TGF research. Results will be presented from TGF simulations using realistic electric fields expected within and above storm clouds, and will include video displays showing the evolving ionization structure of electron trajectories, the time evolution of photon flux fields, electron-positron flux fields, their important circular feedback movement in the local earth magnetic field, local molecular ion densities, and the dielectric effect of induced local electric fields. The second aim of the package is as a step in creating open source software which could evolve into a standard research software package approved by the REA-TGF research community to correctly simulate all the relevant physical processes involved in the complex phenomenon of REA in thunderstorms. TGF photon expansion in stratosphere TGF photon expansion to orbital altitudes

  19. High energy photon reference for radiation protection: technical design of the LINAC beam and ionization chambers; and calculation of monoenergetic conversion coefficients

    NASA Astrophysics Data System (ADS)

    Dusciac, D.; Bordy, J.-M.; Daures, J.; Blideanu, V.

    2016-09-01

    In this work, we present the results of the first part of a research project aimed at offering a complete response to dosimeters providers and nuclear physicists' demands for high-energy (6 - 9 MeV) photon beams for radiation protection purposes. Classical facilities allowing the production of high-energy photonic radiation (proton accelerators, nuclear reactors) are very rare and need large investment for development and use. A novel solution is proposed, consisting in the use of a medical linear accelerator, allowing a significant decrease of all costs.Using Monte Carlo simulations (MCNP5 and PENELOPE codes), a specifically designed electron-photon conversion target allowing for obtaining a high energy photon beam (with an average energy weighted by fluence of about 6 MeV) has been built for radiation protection purposes. Due to the specific design of the target, this "realistic" radiation protection high-energy photon beam presents a uniform distribution of air kerma rate at a distance of 1 m, over a 30 × 30 cm2 surface. Two graphite cavity ionizing chambers for ionometric measurements have been built. For one of these chambers, the charge collection volume has been measured allowing for its use as a primary standard. The second ionizing chamber is used as a transfer standard; as such it has been calibrated in a 60Co beam, and in the high energy photon beam for radiation protection.The measurements with these ionizing chambers allowed for an evaluation of the air kerma rate in the LINAC based high-energy photon beam for radiation protection: the values cover a range between 36 mGy/h and 210 mGy/h, compatible with radiation protection purposes.Finally, using Monte Carlo simulations, conversion coefficients from air kerma to dose equivalent quantities have been calculated in the range between 10 keV and 22.4 MeV, for the spectral distribution of the fluence corresponding to the beam produced by the linear accelerator of the LNE-LNHB.

  20. Intensity Modulated Radiation Treatment of Prostate Cancer Guided by High Field MR Spectroscopic Imaging

    DTIC Science & Technology

    2006-05-01

    is to be reduced for dose escalation or for hypofractionated treatment22-24. III. KEY RESEARCH ACCOMPLISHMENTS • Refined the endorectal coil-based...Xing L, King C.R., Luxton G, Investigation of Linac- based Image-guided Hypofractionated Prostate Radiotherapy, Medical Dosimetry 31, 91-122, 2006...Pawlicki T., Kim G, Hsu A, Cortutz C, Boyer A, Xing L, King C.R., Luxton G, Investigation of Linac- based Image-guided Hypofractionated Prostate Radiotherapy

  1. In-vivo dosimetry for conformal arc therapy using several MOSFET in stereotactic radiosurgery computed by an inverse model

    NASA Astrophysics Data System (ADS)

    Sors, Aurélie; Cassol, Emmanuelle; Masquère, Mathieu; Latorzeff, Igor; Duthil, Pierre; Chauveau, Nicolas; Lotterie, Jean-Albert; Sabatier, Jean; Redon, Alain; Berry, Isabelle; Franceries, Xavier

    2016-09-01

    In-vivo dosimetry is still a challenge in stereotactic radiosurgery since most of treatments are delivered using rotational technique with small fields. A realistic and practical solution for these treatments delivered in conformal radiotherapy is proposed to control the absorbed dose at isocentre, using multiple surface MOSFET measurements over an arc. On the one hand, a forward method was developed to optimize the location of the detectors at the patient surface, taking into account arc length, prescribed isocentre dose, collimator and field size. On the other hand, an inverse method was used to compute the dose at isocentre for conformal arc therapy in stereotactic radiosurgery, using MOSFET measurements. Finally, the reconstructed dose at isocentre was compared to real measurement, obtained for several detectors positioned at a phantom surface. Results show that the inverse method gives good results with five MOSFET equi-spaced positioned within the arc beam course: deviation between prescribed and computed average total dose at isocentre was below 2% both for 30×30 mm2 and 18×18 mm2 field size

  2. SUPERCONDUCTING NON-SCALING FFAG GANTRY FOR CARBON-PROTON CANCER THERAPY

    SciTech Connect

    TRBOJEVIC,D.; GUPTA, R.; PARKER, B.; KEIL, E.; SESSLER, A.M.

    2007-06-25

    We report on improvements in the non-scaling Fixed Field Alternating Gradient (FFAG) gantry design. As we previously reported, a major challenge of the carbodproton cancer therapy facilities is isocentric gantry design. The weight of the isocentric gantry transport elements in the latest Heidelberg carbon/proton facility is 135 tons. In this report we detail improvements to the previous non-scaling gantry design. We estimate that this non-scaling FFAG gantry would be almost hundred times lighter than traditional heavy ion gantries. Very strong focusing with small dispersion permits passage of different energies of carbon beams through the gantry's fixed magnetic field.

  3. The use of enriched 6Li and 7Li Lif:Mg,Cu,P glass-rod thermoluminescent dosemeters for linear accelerator out-of-field radiation dose measurements.

    PubMed

    Takam, R; Bezak, E; Liu, G; Marcu, L

    2012-06-01

    (6)LiF:Mg,Cu,P and (7)LiF:Mg,Cu,P glass-rod thermoluminescent dosemeters (TLDs) were used for measurements of out-of-field photon and neutron doses produced by Varian iX linear accelerator. Both TLDs were calibrated using 18-MV X-ray beam to investigate their dose-response sensitivity and linearity. CR-39 etch-track detectors (Luxel+, Landauer) were employed to provide neutron dose data to calibrate (6)LiF:Mg,Cu,P TLDs at various distances from the isocentre. With cadmium filters employed, slow neutrons (<0.5 eV) were distinguished from fast neutrons. The average in-air photon dose equivalents per monitor unit (MU) ranged from 1.5±0.4 to 215.5±94.6 μSv at 100 and 15 cm from the isocentre, respectively. Based on the cross-calibration factors obtained with CR-39 etch-track detectors, the average in-air fast neutron dose equivalents per MU range from 10.6±3.8 to 59.1±49.9 μSv at 100 and 15 cm from the isocentre, respectively. Contribution of thermal neutrons to total neutron dose equivalent was small: 3.1±7.2 μSv per MU at 15 cm from the isocentre.

  4. An anthropomorphic phantom study of visualisation of surgical clips for partial breast irradiation (PBI) setup verification.

    PubMed

    Thomas, Carys W; Nichol, Alan M; Park, Julie E; Hui, Jason F; Giddings, Alison A; Grahame, Sheri; Otto, Karl

    2009-01-01

    Surgical clips were investigated for partial breast image-guided radiotherapy (IGRT). Small titanium clips were insufficiently well visualised. Medium tantalum clips were best for megavoltage IGRT and small tantalum clips were best for floor mounted kilovoltage IGRT (ExacTrac). Both small tantalum and medium titanium clips were suitable for isocentric kilovoltage IGRT.

  5. Evaluation of stereotactic body radiotherapy (SBRT) boost in the management of endometrial cancer.

    PubMed

    Demiral, S; Beyzadeoglu, M; Uysal, B; Oysul, K; Kahya, Y Elcim; Sager, O; Dincoglan, F; Gamsiz, H; Dirican, B; Surenkok, S

    2013-01-01

    The purpose of this study is to evaluate the use of linear accelerator (LINAC)-based stereotactic body radiotherapy (SBRT) boost with multileaf collimator technique after pelvic radiotherapy (RT) in patients with endometrial cancer. Consecutive patients with endometrial cancer treated using LINAC-based SBRT boost after pelvic RT were enrolled in the study. All patients had undergone surgery including total abdominal hysterectomy and bilateral salpingo-oophorectomy ± pelvic/paraortic lymphadenectomy before RT. Prescribed external pelvic RT dose was 45 Gray (Gy) in 1.8 Gy daily fractions. All patients were treated with SBRT boost after pelvic RT. The prescribed SBRT boost dose to the upper two thirds of the vagina including the vaginal vault was 18 Gy delivered in 3 fractions with 1-week intervals. Gastrointestinal and genitourinary toxicity was assessed using the Common Terminology Criteria for Adverse Events version 3 (CTCAE v3).Between April 2010 and May 2011, 18 patients with stage I-III endometrial cancer were treated with LINAC-based SBRT boost after pelvic RT. At a median follow-up of 24 (8-26) months with magnetic resonance imaging (MRI) and gynecological examination, local control rate of the study group was 100 % with negligible acute and late toxicity.LINAC-based SBRT boost to the vaginal cuff is a feasible gynecological cancer treatment modality with excellent local control and minimal toxicity that may replace traditional brachytherapy boost in the management of endometrial cancer.

  6. Overview of the Defense Programs Research and Technology Development Program for Fiscal Year 1993

    SciTech Connect

    Not Available

    1993-09-30

    This documents presents a programmatic overview and program element plan summaries for conceptual design and assessment; physics; computation and modeling; system engineering science and technology; electronics, photonics, sensors, and mechanical components; chemistry and materials; special nuclear materials, tritium, and explosives.

  7. Beta/gamma Monte Carlo transport in repetitive structures of satellite systems

    NASA Astrophysics Data System (ADS)

    Halbleib, J. A.

    An efficient electron-photon Monte Carlo model, taking advantage of approximate periodicity in repetitive satellite structures, is employed to benchmark a more approximate code and to study the shielding effect of a honeycomb-like structure.

  8. Photon-Electron Interaction and Condense Beams

    SciTech Connect

    Chattopadhyay, S.

    1998-11-01

    We discuss beams of charged particles and radiation from multiple perspectives. These include fundamental acceleration and radiation mechanisms, underlying electron-photon interaction, various classical and quantum phase-space concepts and fluctuational interpretations.

  9. SU-E-T-376: 3-D Commissioning for An Image-Guided Small Animal Micro- Irradiation Platform

    SciTech Connect

    Qian, X; Wuu, C; Admovics, J

    2014-06-01

    Purpose: A 3-D radiochromic plastic dosimeter has been used to cross-test the isocentricity of a high resolution image-guided small animal microirradiation platform. In this platform, the mouse stage rotating for cone beam CT imaging is perpendicular to the gantry rotation for sub-millimeter radiation delivery. A 3-D dosimeter can be used to verify both imaging and irradiation coordinates. Methods: A 3-D dosimeter and optical CT scanner were used in this study. In the platform, both mouse stage and gantry can rotate 360° with rotation axis perpendicular to each other. Isocentricity and coincidence of mouse stage and gantry rotations were evaluated using star patterns. A 3-D dosimeter was placed on mouse stage with center at platform isocenter approximately. For CBCT isocentricity, with gantry moved to 90°, the mouse stage rotated horizontally while the x-ray was delivered to the dosimeter at certain angles. For irradiation isocentricity, the gantry rotated 360° to deliver beams to the dosimeter at certain angles for star patterns. The uncertainties and agreement of both CBCT and irradiation isocenters can be determined from the star patterns. Both procedures were repeated 3 times using 3 dosimeters to determine short-term reproducibility. Finally, dosimeters were scanned using optical CT scanner to obtain the results. Results: The gantry isocentricity is 0.9 ± 0.1 mm and mouse stage rotation isocentricity is about 0.91 ± 0.11 mm. Agreement between the measured isocenters of irradiation and imaging coordinates was determined. The short-term reproducibility test yielded 0.5 ± 0.1 mm between the imaging isocenter and the irradiation isocenter, with a maximum displacement of 0.7 ± 0.1 mm. Conclusion: The 3-D dosimeter can be very useful in precise verification of targeting for a small animal irradiation research. In addition, a single 3-D dosimeter can provide information in both geometric and dosimetric uncertainty, which is crucial for translational studies.

  10. Dose verification of intensity-modulated arc therapy using an ERGO++ treatment planning system and Elekta internal multileaf collimators for prostate cancer treatment.

    PubMed

    Yoda, K; Nakagawa, K; Shiraishi, K; Okano, Y; Ohtomo, K; Pellegrini, R G

    2009-04-01

    Dose verification of intensity-modulated arc therapy using an ERGO++ treatment planning system and Elekta internal multileaf collimators is described. Prostate intensity-modulated arc therapy was planned using the arc modulation optimization algorithm inverse planning module of ERGO++. After transferring the plan to Elekta Synergy's controller (Elekta Ltd, Crawley, UK), the isocentre dose was measured and compared with a calculated dose using a pinpoint chamber and a water phantom in a cylindrical acrylic enclosure. Subsequently, an EDR2 film was placed inside a multilayer plastic phantom, and total dose distributions were measured in three axial planes as well as in the coronal and sagittal planes to compare the actual dose with the calculated dose. The dose discrepancy at the isocentre was 1.7%. The calculated gamma indices were less than 1 over 90% of the three axial planes, as well as in the coronal and sagittal planes, having a dose greater than 50% of the maximum target dose.

  11. Management of choroidal melanomas with linear accelerator-based stereotactic radiosurgery.

    PubMed

    Leung, S W; Hsiung, C Y; Chen, H C; Chen, H J; Lin, S A

    1999-02-01

    To discuss the technical aspect, dose prescription, clinical results, and biological responsiveness of linear accelerator-based stereotactic radiosurgery for choroidal melanoma. From March 1995 to December 1995, three choroidal melanoma patients were treated with Linac-based radiosurgery in our department. Two patients underwent one dose of radiosurgery with 18 and 20 Gy in single fraction, respectively. The third patient received two doses of radiosurgery with a total dose of 35 Gy. Follow-up time ranged from 19 to 25 months (median: 24 months). One patient had near-total regression, while the other two patients had partial response on the last MR images. Visual acuity was deteriorated in all patients. One patient developed a radiation-induced cataract in the treated eye. Linac-based radiosurgery is technically feasible for management of choroidal melanoma. Although visual acuity was not improved in these patients, they appreciated the preserving of the eyeball without affecting their general appearance.

  12. A calculator based program to optimize the simulation of breast irradiation.

    PubMed

    Lederer, E W; Schwendener, H

    1997-01-01

    The simulation of breast fields using an isocentric set-up technique can be a lengthy process involving the placement of the isocentre, the determination of the gantry angles, and the selection of the lung shields, which in our center is one of six standard blocks. We show that with a body contour taken through central axis, five measurements and a calculator program, it is possible to significantly decrease the amount of time required to simulate a breast patient. We have developed a program for an HP48GX handheld calculator to determine the gantry angles, the isocentre, the field width, the standard angled block, and the couch and collimator rotation. The calculations are based on measurements of the field length, the horizontal distance between midline and mid axillary line, and the vertical distances from the mid axillary line to the inferior and superior beam border and central axis at midline. We use spherical geometry to perform the calculations to reflect the true environment and do not make any assumptions about the average patient's shape. For the simulation process a jig was developed that is inserted into the tray holder of the simulator to show the optical and radiological shadow of the calculated shielding along the patient's midline for clinical assessment during simulation and on the simulation film. The jig also has a holder for an aluminum wedge to improve the image quality of the simulation film. We admit that the lung shield increases the dose to the contralateral breast because of increased scatter and transmission through the shield; however, the block decreases the volume of irradiated lung while keeping the beam edge along the midline of the patient. The technique has been in use for two years and has resulted in time savings of up to 30% per patient. It has proven to be an easy and accurate way of setting up isocentric treatments to the breast.

  13. Tangential fields. Improved reproducibility for breast-cancer treatment

    SciTech Connect

    Khan, F.M.; Lee, C.K.; Levitt, S.H.

    1983-10-01

    The authors describe an isocentric technique to set up tangential fields for breast-cancer therapy. The setup parameters (source-to-surface distance measured at the midline of the sternum, lateral shift of the treatment couch, and the gantry angle) are predetermined from a computed-tomographic image and a transverse contour which is obtained under treatment-like conditions. This procedure does not require breast immobilization and does not rely on skin marks on the breast.

  14. Comparison between In-house developed and Diamond commercial software for patient specific independent monitor unit calculation and verification with heterogeneity corrections.

    PubMed

    Kuppusamy, Vijayalakshmi; Nagarajan, Vivekanandan; Jeevanandam, Prakash; Murugan, Lavanya

    2016-02-01

    The study was aimed to compare two different monitor unit (MU) or dose verification software in volumetric modulated arc therapy (VMAT) using modified Clarkson's integration technique for 6 MV photons beams. In-house Excel Spreadsheet based monitor unit verification calculation (MUVC) program and PTW's DIAMOND secondary check software (SCS), version-6 were used as a secondary check to verify the monitor unit (MU) or dose calculated by treatment planning system (TPS). In this study 180 patients were grouped into 61 head and neck, 39 thorax and 80 pelvic sites. Verification plans are created using PTW OCTAVIUS-4D phantom and also measured using 729 detector chamber and array with isocentre as the suitable point of measurement for each field. In the analysis of 154 clinically approved VMAT plans with isocentre at a region above -350 HU, using heterogeneity corrections, In-house Spreadsheet based MUVC program and Diamond SCS showed good agreement TPS. The overall percentage average deviations for all sites were (-0.93% + 1.59%) and (1.37% + 2.72%) for In-house Excel Spreadsheet based MUVC program and Diamond SCS respectively. For 26 clinically approved VMAT plans with isocentre at a region below -350 HU showed higher variations for both In-house Spreadsheet based MUVC program and Diamond SCS. It can be concluded that for patient specific quality assurance (QA), the In-house Excel Spreadsheet based MUVC program and Diamond SCS can be used as a simple and fast accompanying to measurement based verification for plans with isocentre at a region above -350 HU. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  15. Dosimetric feasibility of magnetic resonance imaging-guided tri-cobalt 60 preoperative intensity modulated radiation therapy for soft tissue sarcomas of the extremity.

    PubMed

    Kishan, Amar U; Cao, Minsong; Mikaeilian, Argin G; Low, Daniel A; Kupelian, Patrick A; Steinberg, Michael L; Kamrava, Mitchell

    2015-01-01

    The purpose of this study was to investigate the dosimetric differences of delivering preoperative intensity modulated radiation therapy (IMRT) to patients with soft tissue sarcomas of the extremity (ESTS) with a teletherapy system equipped with 3 rotating (60)Co sources and a built-in magnetic resonance imaging and with standard linear accelerator (LINAC)-based IMRT. The primary study population consisted of 9 patients treated with preoperative radiation for ESTS between 2008 and 2014 with LINAC-based static field IMRT. LINAC plans were designed to deliver 50 Gy in 25 fractions to 95% of the planning target volume (PTV). Tri-(60)Co system IMRT plans were designed with ViewRay system software. Tri-(60)Co-based IMRT plans achieved equivalent target coverage and dosimetry for organs at risk (long bone, skin, and skin corridor) compared with LINAC-based IMRT plans. The maximum and minimum PTV doses, heterogeneity indices, and ratio of the dose to 50% of the volume were equivalent for both planning systems. One LINAC plan violated the maximum bone dose constraint, whereas none of the tri-(60)Co plans did. Using a tri-(60)Co system, we were able to achieve equivalent dosimetry to the PTV and organs at risk for patients with ESTS compared with LINAC-based IMRT plans. The tri-(60)Co system may be advantageous over current treatment platforms by allowing PTV reduction and by elimination of the additional radiation dose associated with daily image guidance, but this needs to be evaluated prospectively. Copyright © 2015 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

  16. Design Study of Linear Accelerator-Based Positron Re-Emission Microscopy

    NASA Astrophysics Data System (ADS)

    Ogawa, Hiroshi; Kinomura, Atsushi; Oshima, Nagayasu; Suzuki, Ryoichi; O'Rourke, Brian E.

    In order to shorten the acquisition time of positron re-emission microscopy (PRM), a linear accelerator (LINAC)-based PRM system has been studied. The beam focusing system was designed to obtain a high brightness positron beam on the PRM sample. The beam size at the sample was calculated to be 0.8mm (FWHM), and the positron intensity within the field of view of the PRM was more than one order of magnitude higher in comparison with the previous studies.

  17. Spallation neutron source and other high intensity froton sources

    SciTech Connect

    Weiren Chou

    2003-02-06

    This lecture is an introduction to the design of a spallation neutron source and other high intensity proton sources. It discusses two different approaches: linac-based and synchrotron-based. The requirements and design concepts of each approach are presented. The advantages and disadvantages are compared. A brief review of existing machines and those under construction and proposed is also given. An R&D program is included in an appendix.

  18. 140 GHz microwave FEL experiments using ELF-II

    SciTech Connect

    Throop, A.L.; Jong, R.A.; Atkinson, D.P.; Clark, J.C.; Felker, B.; Ferguson, S.W.; Makowski, M.A.; Nexsen, W.E.; Stallard, B.W.; Stever, R.D.; Turner, W.C.

    1989-09-01

    We describe the modeling, the experimental facility, and the initial operating results for ELF-II, an induction-linac based free-electron laser designed to produce up to 2 GW of peak power at 140 GHz. ELF-II is the initial configuration of an FEL system which will eventually produce up to 2 MW of average power at a frequency of 250 GHz, for use in plasma heating experiments in the Microwave Tokamak Experiment. 6 refs., 9 figs.

  19. Surface Roughness Impedance

    SciTech Connect

    Stupakov, Gennady

    2000-12-21

    The next generation of linac-based free electron lasers will use very short bunches with a large peak current. For such beams, the impedance caused by submicron imperfections in the vacuum beam tube may generate an additional energy spread within the bunch. A review of two mechanisms of the roughness impedance is given with the emphasis on the importance of the high-aspect ratio property of the real surface roughness.

  20. Volume Changes After Stereotactic LINAC Radiotherapy in Vestibular Schwannoma: Control Rate and Growth Patterns

    SciTech Connect

    Langenberg, Rick van de; Dohmen, Amy J.C.; Bondt, Bert J. de; Nelemans, Patty J.; Baumert, Brigitta G.; Stokroos, Robert J.

    2012-10-01

    Purpose: The purpose of this study was to evaluate the control rate of vestibular schwannomas (VS) after treatment with linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) or radiotherapy (SRT) by using a validated volumetric measuring tool. Volume-based studies on prognosis after LINAC-based SRS or SRT for VS are reported scarcely. In addition, growth patterns and risk factors predicting treatment failure were analyzed. Materials and Methods: Retrospectively, 37 VS patients treated with LINAC based SRS or SRT were analyzed. Baseline and follow-up magnetic resonance imaging scans were analyzed with volume measurements on contrast enhanced T1-weighted magnetic resonance imaging. Absence of intervention after radiotherapy was defined as 'no additional intervention group, ' absence of radiological growth was defined as 'radiological control group. ' Significant growth was defined as a volume change of 19.7% or more, as calculated in a previous study. Results: The cumulative 4-year probability of no additional intervention was 96.4% {+-} 0.03; the 4-year radiological control probability was 85.4% {+-} 0.1). The median follow-up was 40 months. Overall, shrinkage was seen in 65%, stable VS in 22%, and growth in 13%. In 54% of all patients, transient swelling was observed. No prognostic factors were found regarding VS growth. Previous treatment and SRS were associated with transient swelling significantly. Conclusions: Good control rates are reported for LINAC based SRS or SRT in VS, in which the lower rate of radiological growth control is attributed to the use of the more sensitive volume measurements. Transient swelling after radiosurgery is a common phenomenon and should not be mistaken for treatment failure. Previous treatment and SRS were significantly associated with transient swelling.

  1. A dedicated spectrometer for dissolution DNP NMR spectroscopy.

    PubMed

    Leggett, James; Hunter, Robert; Granwehr, Josef; Panek, Rafal; Perez-Linde, Angel J; Horsewill, Anthony J; McMaster, Jonathan; Smith, Graham; Köckenberger, Walter

    2010-06-14

    Using low temperature dynamic nuclear polarisation (DNP) in conjunction with dissolution makes it possible to generate highly polarised nuclear spin systems for liquid state applications of nuclear magnetic resonance spectroscopy. However, in its current implementation, which requires the transfer of the solute between two different magnets, the hyperpolarisation strategy is limited to spin systems with relatively long longitudinal relaxation time constants. Here we describe the design and construction of a dedicated spectrometer for DNP applications that is based on a magnet with two isocentres. DNP enhancement is carried out in the upper compartment of this magnet in a low temperature environment at 3.35 T, while a 9.4 T isocentre in the lower compartment is used for high resolution NMR spectroscopy. The close proximity (85 cm) of the two isocentres makes it possible to transfer the sample in the solid state with very little loss of spin polarisation. In first performance tests this novel experimental set-up proved to be superior to the strategy involving two separate magnets.

  2. Robust frameless stereotactic localization in extra-cranial radiotherapy

    SciTech Connect

    Riboldi, Marco; Baroni, Guido; Spadea, Maria Francesca; Bassanini, Fabio; Tagaste, Barbara; Garibaldi, Cristina; Orecchia, Roberto; Pedotti, Antonio

    2006-04-15

    In the field of extra-cranial radiotherapy, several inaccuracies can make the application of frameless stereotactic localization techniques error-prone. When optical tracking systems based on surface fiducials are used, inter- and intra-fractional uncertainties in marker three-dimensional (3D) detection may lead to inexact tumor position estimation, resulting in erroneous patient setup. This is due to the fact that external fiducials misdetection results in deformation effects that are poorly handled in a rigid-body approach. In this work, the performance of two frameless stereotactic localization algorithms for 3D tumor position reconstruction in extra-cranial radiotherapy has been specifically tested. Two strategies, unweighted versus weighted, for stereotactic tumor localization were examined by exploiting data coming from 46 patients treated for extra-cranial lesions. Measured isocenter displacements and rotations were combined to define isocentric procedures, featuring 6 degrees of freedom, for correcting patient alignment (isocentric positioning correction). The sensitivity of the algorithms to uncertainties in the 3D localization of fiducials was investigated by means of 184 numerical simulations. The performance of the implemented isocentric positioning correction was compared to conventional point-based registration. The isocentric positioning correction algorithm was tested on a clinical dataset of inter-fractional and intra-fractional setup errors, which was collected by means of an optical tracker on the same group of patients. The weighted strategy exhibited a lower sensitivity to fiducial localization errors in simulated misalignments than those of the unweighted strategy. Isocenter 3D displacements provided by the weighted strategy were consistently smaller than those featured by the unweighted strategy. The peak decrease in median and quartile values of isocenter 3D displacements were 1.4 and 2.7 mm, respectively. Concerning clinical data, the

  3. Automated treatment planning for a dedicated multi-source intra-cranial radiosurgery treatment unit accounting for overlapping structures and dose homogeneity

    SciTech Connect

    Ghobadi, Kimia; Ghaffari, Hamid R.; Aleman, Dionne M.; Jaffray, David A.; Ruschin, Mark

    2013-09-15

    Purpose: The purpose of this work is to advance the two-step approach for Gamma Knife{sup ®} Perfexion™ (PFX) optimization to account for dose homogeneity and overlap between the planning target volume (PTV) and organs-at-risk (OARs).Methods: In the first step, a geometry-based algorithm is used to quickly select isocentre locations while explicitly accounting for PTV-OARs overlaps. In this approach, the PTV is divided into subvolumes based on the PTV-OARs overlaps and the distance of voxels to the overlaps. Only a few isocentres are selected in the overlap volume, and a higher number of isocentres are carefully selected among voxels that are immediately close to the overlap volume. In the second step, a convex optimization is solved to find the optimal combination of collimator sizes and their radiation duration for each isocentre location.Results: This two-step approach is tested on seven clinical cases (comprising 11 targets) for which the authors assess coverage, OARs dose, and homogeneity index and relate these parameters to the overlap fraction for each case. In terms of coverage, the mean V{sub 99} for the gross target volume (GTV) was 99.8% while the V{sub 95} for the PTV averaged at 94.6%, thus satisfying the clinical objectives of 99% for GTV and 95% for PTV, respectively. The mean relative dose to the brainstem was 87.7% of the prescription dose (with maximum 108%), while on average, 11.3% of the PTV overlapped with the brainstem. The mean beam-on time per fraction per dose was 8.6 min with calibration dose rate of 3.5 Gy/min, and the computational time averaged at 205 min. Compared with previous work involving single-fraction radiosurgery, the resulting plans were more homogeneous with average homogeneity index of 1.18 compared to 1.47.Conclusions: PFX treatment plans with homogeneous dose distribution can be achieved by inverse planning using geometric isocentre selection and mathematical modeling and optimization techniques. The quality of the

  4. Automated treatment planning for a dedicated multi-source intra-cranial radiosurgery treatment unit accounting for overlapping structures and dose homogeneity.

    PubMed

    Ghobadi, Kimia; Ghaffari, Hamid R; Aleman, Dionne M; Jaffray, David A; Ruschin, Mark

    2013-09-01

    The purpose of this work is to advance the two-step approach for Gamma Knife(®) Perfexion™ (PFX) optimization to account for dose homogeneity and overlap between the planning target volume (PTV) and organs-at-risk (OARs). In the first step, a geometry-based algorithm is used to quickly select isocentre locations while explicitly accounting for PTV-OARs overlaps. In this approach, the PTV is divided into subvolumes based on the PTV-OARs overlaps and the distance of voxels to the overlaps. Only a few isocentres are selected in the overlap volume, and a higher number of isocentres are carefully selected among voxels that are immediately close to the overlap volume. In the second step, a convex optimization is solved to find the optimal combination of collimator sizes and their radiation duration for each isocentre location. This two-step approach is tested on seven clinical cases (comprising 11 targets) for which the authors assess coverage, OARs dose, and homogeneity index and relate these parameters to the overlap fraction for each case. In terms of coverage, the mean V99 for the gross target volume (GTV) was 99.8% while the V95 for the PTV averaged at 94.6%, thus satisfying the clinical objectives of 99% for GTV and 95% for PTV, respectively. The mean relative dose to the brainstem was 87.7% of the prescription dose (with maximum 108%), while on average, 11.3% of the PTV overlapped with the brainstem. The mean beam-on time per fraction per dose was 8.6 min with calibration dose rate of 3.5 Gy/min, and the computational time averaged at 205 min. Compared with previous work involving single-fraction radiosurgery, the resulting plans were more homogeneous with average homogeneity index of 1.18 compared to 1.47. PFX treatment plans with homogeneous dose distribution can be achieved by inverse planning using geometric isocentre selection and mathematical modeling and optimization techniques. The quality of the obtained treatment plans are clinically satisfactory

  5. A treatment planning comparison between modulated tri-cobalt-60 teletherapy and linear accelerator-based stereotactic body radiotherapy for central early-stage non-small cell lung cancer.

    PubMed

    Merna, Catherine; Rwigema, Jean-Claude M; Cao, Minsong; Wang, Pin-Chieh; Kishan, Amar U; Michailian, Argin; Lamb, James; Sheng, Ke; Agazaryan, Nzhde; Low, Daniel A; Kupelian, Patrick; Steinberg, Michael L; Lee, Percy

    2016-01-01

    We evaluated the feasibility of planning stereotactic body radiotherapy (SBRT) for large central early-stage non-small cell lung cancer with a tri-cobalt-60 (tri-(60)Co) system equipped with real-time magnetic resonance imaging (MRI) guidance, as compared to linear accelerator (LINAC)-based SBRT. In all, 20 patients with large central early-stage non-small cell lung cancer who were treated between 2010 and 2015 with LINAC-based SBRT were replanned using a tri-(60)Co system for a prescription dose of 50Gy in 4 fractions. Doses to organs at risk were evaluated based on established MD Anderson constraints for central lung SBRT. R100 values were calculated as the total tissue volume receiving 100% of the dose (V100) divided by the planning target volume and compared to assess dose conformity. Dosimetric comparisons between LINAC-based and tri-(60)Co SBRT plans were performed using Student׳s t-test and Wilcoxon Ranks test. Blinded reviews by radiation oncologists were performed to assess the suitability of both plans for clinical delivery. The mean planning target volume was 48.3cc (range: 12.1 to 139.4cc). Of the tri-(60)Co SBRT plans, a mean 97.4% of dosimetric parameters per patient met MD Anderson dose constraints, whereas a mean 98.8% of dosimetric parameters per patient were met with LINAC-based SBRT planning (p = 0.056). R100 values were similar between both plans (1.20 vs 1.21, p = 0.79). Upon blinded review by 4 radiation oncologists, an average of 90% of the tri-(60)Co SBRT plans were considered acceptable for clinical delivery compared with 100% of the corresponding LINAC-based SBRT plans (p = 0.17). SBRT planning using the tri-(60)Co system with built-in MRI is feasible and achieves clinically acceptable plans for most central lung patients, with similar target dose conformity and organ at risk dosimetry. The added benefit of real-time MRI-guided therapy may further optimize tumor targeting while improving normal tissue sparing, which warrants further

  6. Study of inelastic e-Cd and e-Zn collisions

    NASA Astrophysics Data System (ADS)

    Piwinski, Mariusz; Klosowski, Lukasz; Dziczek, Darek; Chwirot, Stanislaw

    2016-09-01

    Electron-photon coincidence experiments are well known for providing more detailed information about electron-atom collision than any other technique. The Electron Impact Coherence Parameters (EICP) values obtained in such studies deliver the most complete characterization of the inelastic collision and allow for a verification of proposed theoretical models. We present the results of Stokes and EICP parameters characterising electronic excitation of the lowest singlet P-state of cadmium and zinc atoms for various collision energies. The experiments were performed using electron-photon coincidence technique in the coherence analysis version. The obtained data are presented and compared with existing CCC and RDWA theoretical predictions.

  7. A PEDA approach for monolithic photonic BiCMOS technologies

    NASA Astrophysics Data System (ADS)

    Simon, Stefan; Winzer, Georg; Roßmann, Helmut; Kroh, Marcel; Zimmermann, Lars; Mausolf, Thomas

    2015-06-01

    The paper describes a novel approach to photonic electronic design automation (PEDA) based on the commercial design suite Laytools for circuit and physical layout design and simulation. The goal of this work is the integration of an electronic-photonic design flow into an existing electronic design automation (EDA) tool. Contrary to other solutions, with this approach, it is possible to minimize the required interfaces to other third party tools. In addition to existing electronic device models, photonic components are described with behavioral models. The mask layout has been extended to the needs of the electronic photonic integrated circuit (ePIC) designer and the verification flow was adapted to the photonic structures.

  8. Single-isocenter hybrid IMRT plans versus two-isocenter conventional plans and impact of intrafraction motion for the treatment of breast cancer with supraclavicular lymph nodes involvement.

    PubMed

    Amoush, Ahmad; Murray, Eric; Yu, Jennifer S; Xia, Ping

    2015-07-08

    The purpose of this study was to compare the single-isocenter, four-field hybrid IMRT with the two-isocenter techniques to treat the whole breast and supraclavicular fields and to investigate the intrafraction motions in both techniques in the superior direction. Fifteen breast cancer patients who underwent lumpectomy and adjuvant radiation to the whole breast and supraclavicular (SCV) fossa at our institution were selected for this study. Two planning techniques were compared for the treatment of the breast and SCV lymph nodes. The patients were divided into three subgroups according to the whole breast volume. For the two-isocenter technique, conventional wedged or field-within-a-field tangents (FIF) were used to match with the same anterior field for the SCV region. For the single-isocenter technique, four-field hybrid IMRT was used for the tangent fields matched with a half blocked anterior field for the SCV region. To simulate the intrafraction uncertainties in the longitudinal direction for both techniques, the treatment isocenters were shifted by 1 mm and 2 mm in the superior direction. The average breast clinical tumor volume (CTV) receiving 100% (V(100%)) of the prescription dose (50 Gy) was 99.3% ± 0.5% and 96.4% ± 1.2% for the for two-isocenter and single-isocenter plans (р < 0.05), respectively. The breast CTV receiving 95% of the prescription dose (V(95%)) was close to 100% in both techniques. The average breast CTV receiving 105% (V(105%)) of the prescription dose was 32.4% ± 19.3% and 23.8% ± 13.3% (р = 0.08). The percentage volume of the breast CTV receiving 110% of the dose was 0.4% ± 1.2% in the two-isocentric technique vs. 0.1% ± 0.2% in the single-isocentric technique. The average uniformity index was 0.91 ± 0.02 vs. 0.91 ± 0.01 in both techniques (p = 0.04), but had no clinical impact. The percentage volume of the contralateral breast receiving a dose of 1 Gy was less than 2.3% in small breast patients and insignificant for medium and

  9. Crossover from Incoherent to Coherent Phonon Scattering in Epitaxial Oxide Superlattices

    DTIC Science & Technology

    2013-12-08

    nature. Such phenomena are the consequence of the quantum -mechanical nature of particles such as electrons, photons and phonons. Despite widespread and...largely monochromatic optical and acoustic phonons using laser pump–probe techniques5 and superconducting tunnel junctions6, or, alternatively, the...structurally compatible perovskites with different acoustic impedance mismatches, tunable through chemical substitutions, makes perovskites an

  10. Improved geometry representations for Monte Carlo radiation transport.

    SciTech Connect

    Martin, Matthew Ryan

    2004-08-01

    ITS (Integrated Tiger Series) permits a state-of-the-art Monte Carlo solution of linear time-integrated coupled electron/photon radiation transport problems with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. ITS allows designers to predict product performance in radiation environments.

  11. The DAMPE experiment: first data from space

    NASA Astrophysics Data System (ADS)

    De Mitri, Ivan

    2017-03-01

    The DAMPE satellite has been successfully launched in orbit on December 2015. The science goals of the mission include the study of high energy cosmic ray electrons, photons, protons and nuclei in a wide energy range: 109 - 1014 eV. A report on the mission status will be presented, together with on-orbit detector performance and first data coming from space.

  12. Photonics in Processing (BRIEFING CHARTS)

    DTIC Science & Technology

    2007-03-06

    nm ena ble s PIGGYBANK ON CMOS INFRASTRUCTURE AND PROGRESS Seamless Photonics-Electronics Interface Slide 5 Signal Processing with Integrated ... Photonics “Application Specific Electronic-Photonic Integrated Circuit” (AS-EPIC) demonstration vehicle: Broadband RF Receiver (HF to Ku) using optical

  13. The EPRDATA Format: A Dialogue

    SciTech Connect

    Hughes, III, Henry Grady

    2015-08-18

    Recently the Los Alamos Nuclear Data Team has communicated certain issues of concern in relation to the new electron/photon/relaxation ACE data format as released in the eprdata12 library. In this document those issues are parsed, analyzed, and answered.

  14. Effective field theory for plasmas at all temperatures and densities

    NASA Astrophysics Data System (ADS)

    Braaten, Eric

    1993-05-01

    The solution of the plasmon problem and the subsequent development of an effective field-theory approach to ultrarelativistic plasmas are reviewed. The effective Lagrangians that summarize collective effects in ultrarelativistic quark-gluon and electron-photon plasmas are presented. A generalization that describes an electromagnetic plasma at all temperatures and densities is proposed.

  15. Investigation into the impact of couch sag on delivered dose.

    PubMed

    Arts, J K; Bailey, M J; Bannister, K; Lee, M; Holloway, L

    2006-09-01

    The effect of couch sag on treatment delivery accuracy has been investigated by modelling the variation of delivered dose from planned dose due to the difference between the treatment and simulation couches. The couch sag of the Siemens (Concord, USA) Primus linac was determined relative to the couch sag of the Siemens (Germany) Sensation 4 CT Scanner. A phantom planning study was then undertaken to evaluate the likely clinical impact of the couch sag through an evaluation of changes in dose distribution, dose volume histograms and monitor units. The couch sag was simulated by altering the angle of the CT gantry when obtaining image studysets. A second investigation into the effects of couch sag was undertaken using an existing patient CT studyset. For this investigation, the couch sag was simulated by appropriate rotation of the gantry and collimator angles. The effect of couch sag on calculated monitor units (MU) was found to be statistically insignificant. The small monitor unit changes observed were likely to result from differences in the average linear attenuation coefficient along the beam path to the isocentre. The major differences seen however were in the regions away from the central axis. The dose volume histograms showed that both the bladder and rectum were further spared with increasing tilt angle whilst the PTV dose was unchanged. The only issue at South West Sydney Cancer Services (SWSCS) in terms of patient position variation arises from the angle induced by the couch sag (or more precisely, the difference in couch sag angle between the CT and Linac couches). Due to the relatively uniform structures (of PTV, bladder and rectum), and the proximity of these critical structures to the isocentre, this angular rotation about the isocentre did not cause any major variations to the DVH, MU and isodoses for realistic levels of couch sag (i.e. less than 20mm).

  16. Quantitative analysis of errors in fractionated stereotactic radiotherapy.

    PubMed

    Choi, D R; Kim, D Y; Ahn, Y C; Huh, S J; Yeo, I J; Nam, D H; Lee, J I; Park, K; Kim, J H

    2001-01-01

    Fractionated stereotactic radiotherapy (FSRT) offers a technique to minimize the absorbed dose to normal tissues; therefore, quality assurance is essential for these procedures. In this study, quality assurance for FSRT of 58 cases, between August 1995 and August 1997 are described, and the errors for each step and overall accuracy were estimated. Some of the important items for FSRT procedures are: accuracy in CT localization, transferred image distortion, laser alignment, isocentric accuracy of linear accelerator, head frame movement, portal verification, and various human errors. A geometric phantom, that has known coordinates was used to estimate the accuracy of CT localization. A treatment planning computer was used for checking the transferred image distortion. The mechanical isocenter standard (MIS), rectilinear phantom pointer: (RLPP), and laser target localizer frame (LTLF) were used for laser alignment and target coordinates setting. Head-frame stability check was performed by a depth confirmation helmet (DCH). A film test was done to check isocentric accuracy and portal verification. All measured data for the 58 patients were recorded and analyzed for each item. 4-MV x-rays from a linear accelerator, were used for FSRT, along with homemade circular cones with diameters from 20 to 70 mm (interval: 5 mm). The accuracy in CT localization was 1.2+/-0.5 mm. The isocentric accuracy of the linear accelerator, including laser alignment, was 0.5+/-0.2 mm. The reproducibility of the head frame was 1.1+/-0.6 mm. The overall accuracy was 1.7+/-0.7 mm, excluding human errors.

  17. The effect of field modifier blocks on the fast photoneutron dose equivalent from two high-energy medical linear accelerators.

    PubMed

    Hashemi, Seyed Mehdi; Hashemi-Malayeri, Bijan; Raisali, Gholamreza; Shokrani, Parvaneh; Sharafi, Ali Akbar; Jafarizadeh, Mansour

    2008-01-01

    High-energy linear accelerators (linacs) have several advantages, including low skin doses and high dose rates at deep-seated tumours. But, at energies more than 8 MeV, photonuclear reactions produce neutron contamination around the therapeutic beam, which may induce secondary malignancies. In spite of improvements achieved in medical linac designs, many countries still use conventional (non-intensity-modulated radiotherapy) linacs. Hence, in these conventional machines, fitting the beam over the treatment volume may require using blocks. Therefore, the effect of these devices on neutron production of linacs needs to be studied. The aim of this study was to investigate the effect of field shaping blocks on photoneutron dose in the treatment plane for two high-energy medical linacs. Two medical linacs, a Saturn 43 (25 MeV) and an Elekta SL 75/25 (18 MeV), were studied. Polycarbonate (PC) films were used to measure the fluence of photoneutrons produced by these linacs. After electrochemical etching of the PC films, the neutron dose equivalent was calculated at the isocentre and 50 cm away from the isocentre. It was noted that by increasing the distance from the centre of the X-ray beam towards the periphery, the photoneutron dose equivalent decreases rapidly for both the open and blocked fields. Increasing the energy of the photons causes an increase in the amount of photoneutron dose equivalent. At 25 MeV photon energy, the lead blocks cause a meaningful increase in the dose equivalent of photoneutrons. In this research, a 30% increase was seen in neutron dose contribution to central axis dose at the isocentre of a 25 MeV irregular field shaped by lead blocks. It is concluded that lead blocks must be considered as a source of photoneutron production when treating irregular fields with high-energy photons.

  18. Photon and electron collimator effects on electron output and abutting segments in energy modulated electron therapy

    SciTech Connect

    Olofsson, Lennart; Karlsson, Magnus G.; Karlsson, Mikael

    2005-10-15

    In energy modulated electron therapy a large fraction of the segments will be arranged as abutting segments where inhomogeneities in segment matching regions must be kept as small as possible. Furthermore, the output variation between different segments should be minimized and must in all cases be well predicted. For electron therapy with add-on collimators, both the electron MLC (eMLC) and the photon MLC (xMLC) contribute to these effects when an xMLC tracking technique is utilized to reduce the x-ray induced leakage. Two add-on electron collimator geometries have been analyzed using Monte Carlo simulations: One isocentric eMLC geometry with an isocentric clearance of 35 cm and air or helium in the treatment head, and one conventional proximity geometry with a clearance of 5 cm and air in the treatment head. The electron fluence output for 22.5 MeV electrons is not significantly affected by the xMLC if the shielding margins are larger than 2-3 cm. For small field sizes and 9.6 MeV electrons, the isocentric design with helium in the treatment head or shielding margins larger than 3 cm is needed to avoid a reduced electron output. Dose inhomogeneity in the matching region of electron segments is, in general, small when collimator positions are adjusted to account for divergence in the field. The effect of xMLC tracking on the electron output can be made negligible while still obtaining a substantially reduced x-ray leakage contribution. Collimator scattering effects do not interfere significantly when abutting beam techniques are properly applied.

  19. Effect of Treatment Modality on the Hypothalamic–Pituitary Function of Patients Treated with Radiation Therapy for Pituitary Adenomas: Hypothalamic Dose and Endocrine Outcomes

    PubMed Central

    Elson, Andrew; Bovi, Joseph; Kaur, Kawaljeet; Maas, Diana; Sinson, Grant; Schultz, Chris

    2014-01-01

    Background: Both fractionated external beam radiotherapy and single fraction radiosurgery for pituitary adenomas are associated with the risk of hypothalamic–pituitary (HP) axis dysfunction. Objective: To analyze the effect of treatment modality (Linac, TomoTherapy, or gamma knife) on hypothalamic dose and correlate these with HP-axis deficits after radiotherapy. Methods: Radiation plans of patients treated post-operatively for pituitary adenomas using Linac-based 3D-conformal radiotherapy (CRT) (n = 11), TomoTherapy-based intensity modulated radiation therapy (IMRT) (n = 10), or gamma knife stereotactic radiosurgery (n = 12) were retrospectively reviewed. Dose to the hypothalamus was analyzed and post-radiotherapy hormone function including growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, prolactin, and gonadotropins (follicle stimulating hormone/luteinizing hormone) were assessed. Results: Post-radiation, 13 of 27 (48%) patients eligible for analysis developed at least one new hormone deficit, of which 8 of 11 (72%) occurred in the Linac group, 4 of 8 (50%) occurred in the TomoTherapy group, and 1 of 8 (12.5%) occurred in the gamma knife group. Compared with fractionated techniques, gamma knife showed improved hypothalamic sparing for DMax Hypo and V12Gy. For fractionated modalities, TomoTherapy showed improved dosimetric characteristics over Linac-based treatment with hypothalamic DMean (44.8 vs. 26.8 Gy p = 0.02), DMax (49.8 vs. 39.1 Gy p = 0.04), and V12Gy (100 vs. 76% p = 0.004). Conclusion: Maximal dosimetric avoidance of the hypothalamus was achieved using gamma knife-based radiosurgery followed by TomoTherapy-based IMRT, and Linac-based 3D conformal radiation therapy, respectively. PMID:24782984

  20. Hippocampal-Sparing Whole-Brain Radiotherapy: A 'How-To' Technique Using Helical Tomotherapy and Linear Accelerator-Based Intensity-Modulated Radiotherapy

    SciTech Connect

    Gondi, Vinai; Tolakanahalli, Ranjini; Mehta, Minesh P.; Tewatia, Dinesh; Rowley, Howard; Kuo, John S.; Khuntia, Deepak; Tome, Wolfgang A.

    2010-11-15

    Purpose: Sparing the hippocampus during cranial irradiation poses important technical challenges with respect to contouring and treatment planning. Herein we report our preliminary experience with whole-brain radiotherapy using hippocampal sparing for patients with brain metastases. Methods and Materials: Five anonymous patients previously treated with whole-brain radiotherapy with hippocampal sparing were reviewed. The hippocampus was contoured, and hippocampal avoidance regions were created using a 5-mm volumetric expansion around the hippocampus. Helical tomotherapy and linear accelerator (LINAC)-based intensity-modulated radiotherapy (IMRT) treatment plans were generated for a prescription dose of 30 Gy in 10 fractions. Results: On average, the hippocampal avoidance volume was 3.3 cm{sup 3}, occupying 2.1% of the whole-brain planned target volume. Helical tomotherapy spared the hippocampus, with a median dose of 5.5 Gy and maximum dose of 12.8 Gy. LINAC-based IMRT spared the hippocampus, with a median dose of 7.8 Gy and maximum dose of 15.3 Gy. On a per-fraction basis, mean dose to the hippocampus (normalized to 2-Gy fractions) was reduced by 87% to 0.49 Gy{sub 2} using helical tomotherapy and by 81% to 0.73 Gy{sub 2} using LINAC-based IMRT. Target coverage and homogeneity was acceptable with both IMRT modalities, with differences largely attributed to more rapid dose fall-off with helical tomotherapy. Conclusion: Modern IMRT techniques allow for sparing of the hippocampus with acceptable target coverage and homogeneity. Based on compelling preclinical evidence, a Phase II cooperative group trial has been developed to test the postulated neurocognitive benefit.

  1. Results of a Conservative Dose Plan Linear Accelerator-Based Stereotactic Radiosurgery for Pediatric Intracranial Arteriovenous Malformations.

    PubMed

    Rajshekhar, Vedantam; Moorthy, Ranjith K; Jeyaseelan, Visalakshi; John, Subhashini; Rangad, Faith; Viswanathan, P N; Ravindran, Paul; Singh, Rabiraja

    2016-11-01

    To evaluate the obliteration rate and clinical outcome following linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) for intracranial arteriovenous malformation (AVM) in pediatric patients (age ≤18 years). Factors associated with the obliteration rate and neurologic complications were studied retrospectively in pediatric patients who underwent LINAC-based SRS for AVM between June 1995 and May 2014. The study cohort comprised 36 males and 33 females, with a median age at the time of SRS of 14 years (range, 7-18 years). The mean AVM volume was 8.5 ± 8.7 cc (range, 0.6-41.8 cc). The median marginal dose of radiation delivered was 15 Gy (range, 9-20 Gy). Magnetic resonance imaging (MRI) demonstrated complete obliteration of the AVM in 44 of the 69 patients (63.8%), at a mean follow up of 27.5 months (range, 12-90 months). On subgroup analysis, 41 of the 53 AVMs of ≤14 cc in volume (77.3%) were obliterated. AVMs with a modified AVM radiosurgery score <1 had significantly shorter obliteration times from the time of SRS (P = .006). On multivariate analysis, the mean marginal dose of radiation delivered to the AVM was the sole significant predictor of obliteration (odds ratio, 1.6; 95% confidence interval, 1 to 2.4). A modest median marginal dose of 15 Gy (16 Gy in the obliterated AVM group vs. 12 Gy in the nonobliterated group) resulted in an obliteration rate of 66.7% after LINAC-based SRS for intracranial AVM, with low rate. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Evaluation of linear accelerator-based stereotactic radiosurgery in the management of glomus jugulare tumors.

    PubMed

    Sager, Omer; Beyzadeoglu, Murat; Dincoglan, Ferrat; Gamsiz, Hakan; Demiral, Selcuk; Uysal, Bora; Oysul, Kaan; Dirican, Bahar; Sirin, Sait

    2014-01-01

    Although mostly benign and slow-growing, glomus jugulare tumors have a high propensity for local invasion of adjacent vascular structures, lower cranial nerves and the inner ear, which may result in substantial morbidity and even mortality. Treatment strategies for glomus jugulare tumors include surgery, preoperative embolization followed by surgical resection, conventionally fractionated external beam radiotherapy, radiosurgery in the form of stereotactic radiosurgery or fractionated stereotactic radiation therapy, and combinations of these modalities. In the present study, we evaluate the use of linear accelerator (LINAC)-based stereotactic radiosurgery in the management of glomus jugulare tumors and report our 15-year single center experience. Between May 1998 and May 2013, 21 patients (15 females, 6 males) with glomus jugulare tumors were treated using LINAC-based stereotactic radiosurgery at the Department of Radiation Oncology, Gulhane Military Medical Academy. The indication for stereotactic radiosurgery was the presence of residual or recurrent tumor after surgery for 5 patients, whereas 16 patients having growing tumors with symptoms received stereotactic radiosurgery as the primary treatment. Median follow-up was 49 months (range, 3-98). Median age was 55 years (range, 24-77). Of the 21 lesions treated, 13 (61.9%) were left-sided and 8 (38.1%) were right-sided. Median dose was 15 Gy (range, 10-20) prescribed to the 85%-100% isodose line encompassing the target volume. Local control defined as either tumor shrinkage or the absence of tumor growth on periodical follow-up neuroimaging was 100%. LINAC-based stereotactic radiosurgery offers a safe and efficacious management strategy for glomus jugulare tumors by providing excellent tumor growth control with few complications.

  3. ELECTRON BEAM ION SOURCE PREINJECTOR PROJECT (EBIS) CONCEPTUAL DESIGN REPORT.

    SciTech Connect

    ALESSI, J.; BARTON, D.; BEEBE, E.; GASSNER, D.; ET AL.

    2005-02-28

    This report describes a new heavy ion pre-injector for the Relativistic Heavy Ion Collider (RHIC) based on a high charge state Electron Beam Ion Source (EBIS), a Radio Frequency Quadrupole (RFQ) accelerator, and a short Linac. The highly successful development of an EBIS at BNL now makes it possible to replace the present pre-injector that is based on an electrostatic Tandem with a reliable, low maintenance Linac-based pre-injector. Linac-based pre-injectors are presently used at most accelerator and collider facilities with the exception of RHIC, where the required gold beam intensities could only be met with a Tandem until the recent EBIS development. EBIS produces high charge state ions directly, eliminating the need for the two stripping foils presently used with the Tandem. Unstable stripping efficiencies of these foils are a significant source of luminosity degradation in RHIC. The high reliability and flexibility of the new Linac-based pre-injector will lead to increased integrated luminosity at RHIC and is an essential component for the long-term success of the RHIC facility. This new pre-injector, based on an EBIS, also has the potential for significant future intensity increases and can produce heavy ion beams of all species including uranium beams and, as part of a future upgrade, might also be used to produce polarized {sup 3}He beams. These capabilities will be critical to the future luminosity upgrades and electron-ion collisions in RHIC. The new RFQ and Linac that are used to accelerate beams from the EBIS to an energy sufficient for injection into the Booster are both very similar to existing devices already in operation at other facilities. Injection into the Booster will occur at the same location as the existing injection from the Tandem.

  4. Varying MLC end projection size: an effect of the double-focused Siemens multileaf collimator.

    PubMed

    Buckle, A H

    2006-04-21

    Siemens linacs use multileaf collimators (MLCs) that move in an arc such that the flat faces of the leaf ends are always in the same plane as the radiation focus. An effect of this is that the magnification of the leaf end projection at the isocentric plane normal to the collimator rotation axis varies with the drive position of the leaves. This effect is quantified theoretically and empirically verified. A method is introduced for assessing the importance of the effect for a particular MLC pattern. The significance of the effect is discussed.

  5. Pilot study on interfractional and intrafractional movements using surface infrared markers and EPID for patients with rectal cancer treated in the prone position

    PubMed Central

    Eom, K-Y; Kim, K; Chang, J H; Koo, T R; Park, J I; Park, Y-G; Ye, S-J; Ha, S W

    2015-01-01

    Objective: To evaluate interfractional and intrafractional movement of patients with rectal cancer during radiotherapy with electronic portal imaging device (EPID) and surface infrared (IR) markers. Methods: 20 patients undergoing radiotherapy for rectal cancer with body mass index ranging from 18.5 to 30 were enrolled. Patients were placed in the prone position on a couch with a leg pillow. Three IR markers were put on the surface of each patient and traced by two stereo cameras during radiotherapy on a twice-weekly basis. Interfractional isocentre movement was obtained with EPID images on a weekly basis. Movement of the IR markers was analysed in correlation with the isocentre movement obtained from the EPID images. Results: The maximum right-to-left (R-L) movement of the laterally located markers in the horizontal isocentre plane was correlated with isocentre translocation with statistical significance (p = 0.018 and 0.015, respectively). Movement of the surface markers was cyclical. For centrally located markers, the 95% confidence intervals for the average amplitude in the R-L, cranial-to-caudal (C-C) and anterior-to-posterior (A-P) directions were 0.86, 2.25 and 3.48 mm, respectively. In 10 patients, intrafractional movement exceeding 5 mm in at least one direction was observed. Time-dependent systematic movement of surface markers during treatment, which consisted of continuous movement towards the cranial direction and a sail back motion in the A-P direction, was also observed. Conclusion: Intrafractional movement of surface markers has both cyclic components and time-dependent systematic components. Marker deviations exceeding 5 mm were mainly seen in the A-P direction. Pre- or post-treatment EPID images may not provide adequate information regarding intrafractional movement because of systematic movement in the A-P direction during radiotherapy. Advances in knowledge: This work uncovered a sail back motion of patients in the A-P direction during

  6. Intra-Operative Dosimetry in Prostate Brachytherapy

    DTIC Science & Technology

    2007-11-01

    additional cost to the existing clinical installation. 1 Introduction With an approximate annual incidence of 220,000 new cases and 33,000 deaths...isocentric C-arm, at negligible additional cost to the existing clinical installation. Furthermore, the proposed system is the first of its kind that...PC050042, DoD PC050170 and NIH 2R44CA099374. optimal solution has a near-zero cost when the pose error is low , and is actu- ally zero without pose error

  7. Radiotherapy in the UK

    SciTech Connect

    Ramsay, S.

    1993-10-09

    What is wrong with radiation treatment in the UK Is it bad practice or merely bad publicity Between 1982 and 1991, 1,000 patients receiving isocentric radiation therapy at the North Staffordshire Royal Infirmary received a substantial underdose of radiation; the clinical report on this incident was published last week. The operator had been using a correction factor for tumor-to-skin distance, unaware that this factor had already been applied by the computer system. Although the report pointed out that it is not surprising that the clinicians were not alerted to the undertreatment, is also noted that there were no resources at the hospital to audit the outcome of radiotherapy.

  8. Physical considerations in the treatment of advanced carcinomas of the larynx and pyriform sinuses using 10 MV x rays

    SciTech Connect

    Doppke, K.; Novack, D.; Wang, C.C.

    1980-09-01

    A technique for treating patients who have advanced tumors of the larynx and pyriform sinus was developed using isocentric anterior and posterior opposed fields with 10 MV x rays. This technique can be used to deliver a tumor dose of 45 Gray to the primary site and regional nodes and approximately 40 Gray to the spinal cord. The method eliminates problems of multi-field junctures and lowers the daily spinal cord dose when compared to the standard parallel opposed lateral portals and anterior neck fields.

  9. Superconductivity in Medicine

    NASA Astrophysics Data System (ADS)

    Alonso, Jose R.; Antaya, Timothy A.

    2012-01-01

    Superconductivity is playing an increasingly important role in advanced medical technologies. Compact superconducting cyclotrons are emerging as powerful tools for external beam therapy with protons and carbon ions, and offer advantages of cost and size reduction in isotope production as well. Superconducting magnets in isocentric gantries reduce their size and weight to practical proportions. In diagnostic imaging, superconducting magnets have been crucial for the successful clinical implementation of magnetic resonance imaging. This article introduces each of those areas and describes the role which superconductivity is playing in them.

  10. A Parameter Optimization for a National SASE FEL Facility

    SciTech Connect

    Yavas, O.; Yigit, S.

    2007-04-23

    The parameter optimization for a national SASE FEL facility was studied. Turkish State Planing Organization (DPT) gave financial support as an inter-universities project to begin technical design studies and test facility of National Accelerator Complex starting from 2006. In addition to a particle factory, the complex will contain a linac based free electron laser, positron ring based synchrotron radiation facilities and a proton accelerator. In this paper, we have given some results of main parameters of SASE FEL facility based on 130 MeV linac, application potential in basic and applied research.

  11. The 4th Generation Light Source at Jefferson Lab

    SciTech Connect

    Stephen Benson; George Biallas; James Boyce; Donald Bullard; James Coleman; David Douglas; H. Dylla; Richard Evans; Pavel Evtushenko; Albert Grippo; Christopher Gould; Joseph Gubeli; David Hardy; Carlos Hernandez-Garcia; Kevin Jordan; John Klopf; Steven Moore; George Neil; Thomas Powers; Joseph Preble; Daniel Sexton; Michelle D. Shinn; Christopher Tennant; Richard Walker; Shukui Zhang; Gwyn Williams

    2007-04-25

    A number of "Grand Challenges" in Science have recently been identified in reports from The National Academy of Sciences, and the U.S. Dept. of Energy, Basic Energy Sciences. Many of these require a new generation of linac-based light source to study dynamical and non-linear phenomena in nanoscale samples. In this paper we present a summary of the properties of such light sources, comparing them with existing sources, and then describing in more detail a specific source at Jefferson Lab. Importantly, the JLab light source has developed some novel technology which is a critical enabler for other new light sources.

  12. Comparison of Lattice Options for the NLC Main Linac (LCC-0024)

    SciTech Connect

    Nosochkov, Y.

    2004-03-23

    The goal of this study was to select an optimal lattice for the NLC main linac, based on the analysis and comparison of several lattice options. In this study, we examined the FODO and doublet optics, combinations of 2 vs. 3 accelerator structures per girder, three options for the phase advance per cell and various configurations for the BNS autophasing energy spread. In the lattice analysis, we compared the calculations of emittance growth and misalignment tolerances due to ground motion, as well as magnet parameters.

  13. Observation of self-amplified spontaneous emission and exponential growth at 530 nm

    PubMed

    Milton; Gluskin; Biedron; Dejus; Den Hartog PK; Galayda; Kim; Lewellen; Moog; Sajaev; Sereno; Travish; Vinokurov; Arnold; Benson; Berg; Biggs; Borland; Carwardine; Chae; Decker; Deriy; Erdmann; Friedsam; Gold; Grelick

    2000-07-31

    Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator.

  14. A review on photoneutrons characteristics in radiation therapy with high-energy photon beams.

    PubMed

    Naseri, Alireza; Mesbahi, Asghar

    2010-09-22

    In radiation therapy with high-energy photon beams (E > 10 MeV) neutrons are generated mainly in linacs head thorough (γ,n) interactions of photons with nuclei of high atomic number materials that constitute the linac head and the beam collimation system. These neutrons affect the shielding requirements in radiation therapy rooms and also increase the out-of-field radiation dose of patients undergoing radiation therapy with high-energy photon beams. In the current review, the authors describe the factors influencing the neutron production for different medical linacs based on the performed measurements and Monte Carlo studies in the literature.

  15. A review on photoneutrons characteristics in radiation therapy with high-energy photon beams

    PubMed Central

    Naseri, Alireza; Mesbahi, Asghar

    2010-01-01

    In radiation therapy with high-energy photon beams (E > 10 MeV) neutrons are generated mainly in linacs head thorough (γ,n) interactions of photons with nuclei of high atomic number materials that constitute the linac head and the beam collimation system. These neutrons affect the shielding requirements in radiation therapy rooms and also increase the out-of-field radiation dose of patients undergoing radiation therapy with high-energy photon beams. In the current review, the authors describe the factors influencing the neutron production for different medical linacs based on the performed measurements and Monte Carlo studies in the literature. PMID:24376940

  16. A treatment planning comparison between modulated tri-cobalt-60 teletherapy and linear accelerator–based stereotactic body radiotherapy for central early-stage non−small cell lung cancer

    SciTech Connect

    Merna, Catherine; Rwigema, Jean-Claude M.; Cao, Minsong; Wang, Pin-Chieh; Kishan, Amar U.; Michailian, Argin; Lamb, James; Sheng, Ke; Agazaryan, Nzhde; Low, Daniel A.; Kupelian, Patrick; Steinberg, Michael L.; Lee, Percy

    2016-04-01

    We evaluated the feasibility of planning stereotactic body radiotherapy (SBRT) for large central early-stage non−small cell lung cancer with a tri-cobalt-60 (tri-{sup 60}Co) system equipped with real-time magnetic resonance imaging (MRI) guidance, as compared to linear accelerator (LINAC)–based SBRT. In all, 20 patients with large central early-stage non−small cell lung cancer who were treated between 2010 and 2015 with LINAC-based SBRT were replanned using a tri-{sup 60}Co system for a prescription dose of 50 Gy in 4 fractions. Doses to organs at risk were evaluated based on established MD Anderson constraints for central lung SBRT. R{sub 100} values were calculated as the total tissue volume receiving 100% of the dose (V{sub 100}) divided by the planning target volume and compared to assess dose conformity. Dosimetric comparisons between LINAC-based and tri-{sup 60}Co SBRT plans were performed using Student's t-test and Wilcoxon Ranks test. Blinded reviews by radiation oncologists were performed to assess the suitability of both plans for clinical delivery. The mean planning target volume was 48.3 cc (range: 12.1 to 139.4 cc). Of the tri-{sup 60}Co SBRT plans, a mean 97.4% of dosimetric parameters per patient met MD Anderson dose constraints, whereas a mean 98.8% of dosimetric parameters per patient were met with LINAC-based SBRT planning (p = 0.056). R{sub 100} values were similar between both plans (1.20 vs 1.21, p = 0.79). Upon blinded review by 4 radiation oncologists, an average of 90% of the tri-{sup 60}Co SBRT plans were considered acceptable for clinical delivery compared with 100% of the corresponding LINAC-based SBRT plans (p = 0.17). SBRT planning using the tri-{sup 60}Co system with built-in MRI is feasible and achieves clinically acceptable plans for most central lung patients, with similar target dose conformity and organ at risk dosimetry. The added benefit of real-time MRI-guided therapy may further optimize tumor targeting while improving

  17. Development of 325 MHz single spoke resonators at Fermilab

    SciTech Connect

    Apollinari, G.; Gonin, I.V.; Khabiboulline, T.N.; Lanfranco, G.; Mukherjee, A.; Ozelis, J.; Ristori, L.; Sergatskov, D.; Wagner, R.; Webber, R.; /Fermilab

    2008-08-01

    The High Intensity Neutrino Source (HINS) project represents the current effort at Fermilab to produce an 8-GeV proton linac based on 400 independently phased superconducting cavities. Eighteen ?=0.21 single spoke resonators, operating at 325 MHz, comprise the first stage of the linac cold section. In this paper we present the current status of the production and testing of the first two prototype cavities. This includes descriptions of the fabrication, frequency tuning, chemical polishing, high pressure rinse, and high-gradient cold tests.

  18. Simultaneous optimization of the cavity heat load and trip rates in linacs using a genetic algorithm

    DOE PAGES

    Terzić, Balša; Hofler, Alicia S.; Reeves, Cody J.; ...

    2014-10-15

    In this paper, a genetic algorithm-based optimization is used to simultaneously minimize two competing objectives guiding the operation of the Jefferson Lab's Continuous Electron Beam Accelerator Facility linacs: cavity heat load and radio frequency cavity trip rates. The results represent a significant improvement to the standard linac energy management tool and thereby could lead to a more efficient Continuous Electron Beam Accelerator Facility configuration. This study also serves as a proof of principle of how a genetic algorithm can be used for optimizing other linac-based machines.

  19. Symposium on electron linear accelerators in honor of Richard B. Neal's 80th birthday: Proceedings

    SciTech Connect

    Siemann, R.H.

    1998-07-01

    The papers presented at the conference are: (1) the construction of SLAC and the role of R.B. Neal; (2) symposium speech; (3) lessons learned from the SLC; (4) alternate approaches to future electron-positron linear colliders; (5) the NLC technical program; (6) advanced electron linacs; (7) medical uses of linear accelerators; (8) linac-based, intense, coherent X-ray source using self-amplified spontaneous emission. Selected papers have been indexed separately for inclusion in the Energy Science and Technology Database.

  20. Failure mode and effects analysis and fault tree analysis of surface image guided cranial radiosurgery.

    PubMed

    Manger, Ryan P; Paxton, Adam B; Pawlicki, Todd; Kim, Gwe-Ya

    2015-05-01

    Surface image guided, Linac-based radiosurgery (SIG-RS) is a modern approach for delivering radiosurgery that utilizes optical stereoscopic imaging to monitor the surface of the patient during treatment in lieu of using a head frame for patient immobilization. Considering the novelty of the SIG-RS approach and the severity of errors associated with delivery of large doses per fraction, a risk assessment should be conducted to identify potential hazards, determine their causes, and formulate mitigation strategies. The purpose of this work is to investigate SIG-RS using the combined application of failure modes and effects analysis (FMEA) and fault tree analysis (FTA), report on the effort required to complete the analysis, and evaluate the use of FTA in conjunction with FMEA. A multidisciplinary team was assembled to conduct the FMEA on the SIG-RS process. A process map detailing the steps of the SIG-RS was created to guide the FMEA. Failure modes were determined for each step in the SIG-RS process, and risk priority numbers (RPNs) were estimated for each failure mode to facilitate risk stratification. The failure modes were ranked by RPN, and FTA was used to determine the root factors contributing to the riskiest failure modes. Using the FTA, mitigation strategies were formulated to address the root factors and reduce the risk of the process. The RPNs were re-estimated based on the mitigation strategies to determine the margin of risk reduction. The FMEA and FTAs for the top two failure modes required an effort of 36 person-hours (30 person-hours for the FMEA and 6 person-hours for two FTAs). The SIG-RS process consisted of 13 major subprocesses and 91 steps, which amounted to 167 failure modes. Of the 91 steps, 16 were directly related to surface imaging. Twenty-five failure modes resulted in a RPN of 100 or greater. Only one of these top 25 failure modes was specific to surface imaging. The riskiest surface imaging failure mode had an overall RPN-rank of eighth

  1. Traumatic Fracture of Thin Pedicles Secondary to Extradural Meningeal Cyst

    PubMed Central

    Yanni, Daniel S.; Mammis, Antonios; Thaker, Nikhil G.; Goldstein, Ira M.

    2011-01-01

    Spinal dural meningoceles and diverticula are meningeal cysts that have a myriad of clinical presentations and sequelae, secondary to local mass effect. Our objective is to report a technical case report, illustrating a traumatic spinal injury with multiple pedicle fractures, secondary to atrophic lumbar pedicles as well as the diagnostic workup and surgical management of this problem. Posterior lumbar decompression, resection of the meningeal cyst, ligation of the cyst ostium, instrumentation, and fusion were performed with the assistance of intraoperative isocentric fluoroscopy. The cyst's point of communication was successfully located with intraoperative fluoroscopy and the lesion was successfully excised. We suggest that patients with traumatic spinal injuries, having evidence of pre-existing anomalous bony architecture, undergo advanced imaging studies, to rule out intraspinal pathology. The positive clinical and radiographic results support the removal and closure of the pre-existing meningeal cyst at the time of treatment of traumatic spinal injury. Intraoperative isocentric fluoroscopy is a helpful tool in the operative management of these lesions. PMID:22022654

  2. Effects of bone- and air-tissue inhomogeneities on the dose distributions of the Leksell Gamma Knife calculated with PENELOPE.

    PubMed

    Al-Dweri, Feras M O; Rojas, E Leticia; Lallena, Antonio M

    2005-12-07

    Monte Carlo simulation with PENELOPE (version 2003) is applied to calculate Leksell Gamma Knife dose distributions for heterogeneous phantoms. The usual spherical water phantom is modified with a spherical bone shell simulating the skull and an air-filled cube simulating the frontal or maxillary sinuses. Different simulations of the 201 source configuration of the Gamma Knife have been carried out with a simplified model of the geometry of the source channel of the Gamma Knife recently tested for both single source and multisource configurations. The dose distributions determined for heterogeneous phantoms including the bone- and/or air-tissue interfaces show non-negligible differences with respect to those calculated for a homogeneous one, mainly when the Gamma Knife isocentre approaches the separation surfaces. Our findings confirm an important underdosage (approximately 10%) nearby the air-tissue interface, in accordance with previous results obtained with the PENELOPE code with a procedure different from ours. On the other hand, the presence of the spherical shell simulating the skull produces a few per cent underdosage at the isocentre wherever it is situated.

  3. Resampling: An optimization method for inverse planning in robotic radiosurgery

    SciTech Connect

    Schweikard, Achim; Schlaefer, Alexander; Adler, John R. Jr.

    2006-11-15

    By design, the range of beam directions in conventional radiosurgery are constrained to an isocentric array. However, the recent introduction of robotic radiosurgery dramatically increases the flexibility of targeting, and as a consequence, beams need be neither coplanar nor isocentric. Such a nonisocentric design permits a large number of distinct beam directions to be used in one single treatment. These major technical differences provide an opportunity to improve upon the well-established principles for treatment planning used with GammaKnife or LINAC radiosurgery. With this objective in mind, our group has developed over the past decade an inverse planning tool for robotic radiosurgery. This system first computes a set of beam directions, and then during an optimization step, weights each individual beam. Optimization begins with a feasibility query, the answer to which is derived through linear programming. This approach offers the advantage of completeness and avoids local optima. Final beam selection is based on heuristics. In this report we present and evaluate a new strategy for utilizing the advantages of linear programming to improve beam selection. Starting from an initial solution, a heuristically determined set of beams is added to the optimization problem, while beams with zero weight are removed. This process is repeated to sample a set of beams much larger compared with typical optimization. Experimental results indicate that the planning approach efficiently finds acceptable plans and that resampling can further improve its efficiency.

  4. Resampling: an optimization method for inverse planning in robotic radiosurgery.

    PubMed

    Schweikard, Achim; Schlaefer, Alexander; Adler, John R

    2006-11-01

    By design, the range of beam directions in conventional radiosurgery are constrained to an isocentric array. However, the recent introduction of robotic radiosurgery dramatically increases the flexibility of targeting, and as a consequence, beams need be neither coplanar nor isocentric. Such a nonisocentric design permits a large number of distinct beam directions to be used in one single treatment. These major technical differences provide an opportunity to improve upon the well-established principles for treatment planning used with GammaKnife or LINAC radiosurgery. With this objective in mind, our group has developed over the past decade an inverse planning tool for robotic radiosurgery. This system first computes a set of beam directions, and then during an optimization step, weights each individual beam. Optimization begins with a feasibility query, the answer to which is derived through linear programming. This approach offers the advantage of completeness and avoids local optima. Final beam selection is based on heuristics. In this report we present and evaluate a new strategy for utilizing the advantages of linear programming to improve beam selection. Starting from an initial solution, a heuristically determined set of beams is added to the optimization problem, while beams with zero weight are removed. This process is repeated to sample a set of beams much larger compared with typical optimization. Experimental results indicate that the planning approach efficiently finds acceptable plans and that resampling can further improve its efficiency.

  5. Dosimetric characteristics of the Elekta Beam Modulator.

    PubMed

    Patel, I; Glendinning, A G; Kirby, M C

    2005-12-07

    The dosimetric characteristics of a production pilot multi-leaf collimator (Elekta Beam Modulator, Elekta Oncology Systems, Crawley, UK) having a 4 mm leaf width (at isocentre) have been investigated. Characteristics explored included leaf bank set-up, penumbra width (80-20%) as a function of leaf position, leaf positioning reproducibility, interleaf leakage and leaf transmission. The penumbra values for leaf ends were measured to be between 4.2 and 4.8 mm for various large rectangular fields studied using Kodak X-omat V film at isocentre (1.5 cm deep). Similar films were taken with a standard 1 cm width multi-leaf collimator (MLC) and the penumbra for leaf ends was found to range from 4.3 to 5.2 mm. Other results showed that the rounded leaf tip provided tight control of the penumbra across the leaves' full range of travel. The positioning of the leaves was within a 0.5 mm range when approaching from the same direction. The maximum interleaf leakage was found to be 1.7% and the average leaf transmission less than 1.0%. No major differences were observed in leakage and transmission with changing gantry angle.

  6. The optimization of intensity modulated radiotherapy in cases where the planning target volume extends into the build-up region.

    PubMed

    Nguyen, T B; Hoole, A C F; Burnet, N G; Thomas, S J

    2009-04-21

    A common clinical problem in IMRT, especially when treating head and neck cases, is that the clinical target volume (CTV) stops short of the skin surface, whilst the margin for geometric uncertainties may take the planning target volume (PTV) to the skin surface or beyond. In these cases, optimization leads to over-dosing of the skin, unless the planner resorts to procedural tricks to avoid this, such as the use of pretend bolus or reduction of the PTV followed by adding 'flash' after optimization. This paper describes a method of avoiding the need for these tricks by using a multiple-isocentre CTV-based objective function. This enables plans to be produced that will give good coverage of the CTV for all the geometrical uncertainties that would have been covered by the PTV without causing the problem of over-dosing the skin. Eight isocentre shifts, equally distributed on the surface of a sphere with a radius equal to the CTV-PTV margin, are shown to be adequate for the optimization process. The resulting fluence maps are much simpler than those resulting from PTV optimization and will therefore be simpler to deliver. The method also permits better sparing of organs at risk such as the spinal cord.

  7. The optimization of intensity modulated radiotherapy in cases where the planning target volume extends into the build-up region

    NASA Astrophysics Data System (ADS)

    Nguyen, T. B.; Hoole, A. C. F.; Burnet, N. G.; Thomas, S. J.

    2009-04-01

    A common clinical problem in IMRT, especially when treating head and neck cases, is that the clinical target volume (CTV) stops short of the skin surface, whilst the margin for geometric uncertainties may take the planning target volume (PTV) to the skin surface or beyond. In these cases, optimization leads to over-dosing of the skin, unless the planner resorts to procedural tricks to avoid this, such as the use of pretend bolus or reduction of the PTV followed by adding 'flash' after optimization. This paper describes a method of avoiding the need for these tricks by using a multiple-isocentre CTV-based objective function. This enables plans to be produced that will give good coverage of the CTV for all the geometrical uncertainties that would have been covered by the PTV without causing the problem of over-dosing the skin. Eight isocentre shifts, equally distributed on the surface of a sphere with a radius equal to the CTV-PTV margin, are shown to be adequate for the optimization process. The resulting fluence maps are much simpler than those resulting from PTV optimization and will therefore be simpler to deliver. The method also permits better sparing of organs at risk such as the spinal cord.

  8. Temporal compartmental dosing effects for robotic prostate stereotactic body radiotherapy

    NASA Astrophysics Data System (ADS)

    Shiao, Stephen L.; Sahgal, Arjun; Hu, Weigang; Jabbari, Siavash; Chuang, Cynthia; Descovich, Martina; Hsu, I.-Chow; Gottschalk, Alexander R.; Roach, Mack, III; Ma, Lijun

    2011-12-01

    The rate of dose accumulation within a given area of a target volume tends to vary significantly for non-isocentric delivery systems such as Cyberknife stereotactic body radiotherapy. In this study, we investigated whether intra-target temporal dose distributions produce significant variations in the biological equivalent dose. For the study, time courses of ten patients were reconstructed and calculation of a biologically equivalent uniform dose (EUD) was performed using a formula derived from the linear quadratic model (α/β = 3 for prostate cancer cells). The calculated EUD values obtained for the actual patient treatments were then compared with theoretical EUD values for delivering the same physical dose distribution except that the whole target being irradiated continuously (e.g. large-field ‘dose-bathing’ type of delivery). For all the case, the EUDs for the actual treatment delivery were found to correlate strongly with the EUDs for the large-field delivery: a linear correlation coefficient of R2 = 0.98 was obtained and the average EUD for the actual Cyberknife delivery was somewhat higher (5.0 ± 4.7%) than that for the large-field delivery. However, no statistical significance was detected between the two types of delivery (p = 0.21). We concluded that non-isocentric small-field Cyberknife delivery produced consistent biological dosing that tracked well with the constant-dose-rate, large-field-type delivery for prostate stereotactic body radiotherapy.

  9. Effects of bone- and air-tissue inhomogeneities on the dose distributions of the Leksell Gamma Knife® calculated with PENELOPE

    NASA Astrophysics Data System (ADS)

    Al-Dweri, Feras M. O.; Rojas, E. Leticia; Lallena, Antonio M.

    2005-12-01

    Monte Carlo simulation with PENELOPE (version 2003) is applied to calculate Leksell Gamma Knife® dose distributions for heterogeneous phantoms. The usual spherical water phantom is modified with a spherical bone shell simulating the skull and an air-filled cube simulating the frontal or maxillary sinuses. Different simulations of the 201 source configuration of the Gamma Knife have been carried out with a simplified model of the geometry of the source channel of the Gamma Knife recently tested for both single source and multisource configurations. The dose distributions determined for heterogeneous phantoms including the bone- and/or air-tissue interfaces show non-negligible differences with respect to those calculated for a homogeneous one, mainly when the Gamma Knife isocentre approaches the separation surfaces. Our findings confirm an important underdosage (~10%) nearby the air-tissue interface, in accordance with previous results obtained with the PENELOPE code with a procedure different from ours. On the other hand, the presence of the spherical shell simulating the skull produces a few per cent underdosage at the isocentre wherever it is situated.

  10. An Injector Test Facility for the LCLS

    SciTech Connect

    Colby, E.,; /SLAC

    2007-03-14

    SLAC is in the privileged position of being the site for the world's first 4th generation light source as well as having a premier accelerator research staff and facilities. Operation of the world's first x-ray free electron laser (FEL) facility will require innovations in electron injectors to provide electron beams of unprecedented quality. Upgrades to provide ever shorter wavelength x-ray beams of increasing intensity will require significant advances in the state-of-the-art. The BESAC 20-Year Facilities Roadmap identifies the electron gun as ''the critical enabling technology to advance linac-based light sources'' and recognizes that the sources for next-generation light sources are ''the highest-leveraged technology'', and that ''BES should strongly support and coordinate research and development in this unique and critical technology''.[1] This white paper presents an R&D plan and a description of a facility for developing the knowledge and technology required to successfully achieve these upgrades, and to coordinate efforts on short-pulse source development for linac-based light sources.

  11. Perineural spread of cutaneous malignancy to the brain: a review of the literature and five patients treated with stereotactic radiotherapy.

    PubMed

    Fowler, B Zach; Crocker, Ian R; Johnstone, Peter A S

    2005-05-15

    The retrospective analysis was performed to investigate the role of stereotactic radiotherapy (SRT) techniques for patients with intracranial perineural spread (PNS) of a primary cutaneous malignancy. Five patients were identified who received SRT from 1993 to 2003 for cutaneous malignancies with intracranial PNS to the cavernous sinus (n = 3) or Meckel's cave (n = 2). Patients were treated with GammaKnife stereotactic radiosurgery (n = 2), linear accelerator (linac)-based fractionated SRT (n = 2), or linac-based stereotactic radiosurgery (n = 1). The median overall survival (OS) periods from diagnoses of cutaneous malignancy and intracranial PNS were 63.0 months (range, 22.0-102.2 months) and 25.5 months (range, 22.0-55.2 months), respectively. The median OS from SRT was 24.2 months (range, 19.5-53.2 months). One patient was alive and without evidence of disease at 53 months of follow-up. The median durations of local and regional control from SRT were 19.5 months (range, 1.5-53.2 months) and 7.0 months (range, 1.5-53.2 months), respectively. Previous reports generally have recommended that patients with intracranial PNS receive palliative external-beam radiotherapy. Results from the current study suggest that some of these patients may have prolonged survival, or even may be cured. Judicious use of SRT should be considered in their management.

  12. Optimized Effective Potential for Quantum Electrodynamical Time-Dependent Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Pellegrini, Camilla; Flick, Johannes; Tokatly, Ilya V.; Appel, Heiko; Rubio, Angel

    2015-08-01

    We propose an orbital exchange-correlation functional for applying time-dependent density functional theory to many-electron systems coupled to cavity photons. The time nonlocal equation for the electron-photon optimized effective potential (OEP) is derived. In the static limit our OEP energy functional reduces to the Lamb shift of the ground state energy. We test the new approximation in the Rabi model. It is shown that the OEP (i) reproduces quantitatively the exact ground-state energy from the weak to the deep strong coupling regime and (ii) accurately captures the dynamics entering the ultrastrong coupling regime. The present formalism opens the path to a first-principles description of correlated electron-photon systems, bridging the gap between electronic structure methods and quantum optics for real material applications.

  13. Strongly enhanced effects of Lorentz symmetry violation in entangled Yb+ ions

    NASA Astrophysics Data System (ADS)

    Dzuba, V. A.; Flambaum, V. V.; Safronova, M. S.; Porsev, S. G.; Pruttivarasin, T.; Hohensee, M. A.; Häffner, H.

    2016-05-01

    A number of theories aiming at unifying gravity with other fundamental interactions, including field theory, suggest the violation of Lorentz symmetry. Whereas the energy scale of such strongly Lorentz-symmetry-violating physics is much higher than that attainable at present by particle accelerators, Lorentz violation may nevertheless be detectable via precision measurements at low energies. Here, we carry out a systematic theoretical investigation to identify which atom shows the greatest promise for detecting a Lorentz symmetry violation in the electron-photon sector. We found that the ytterbium ion (Yb+) is an ideal system with high sensitivity, as well as excellent experimental controllability. By applying quantum-information-inspired technology to Yb+, we expect tests of local Lorentz invariance (LLI) violating physics in the electron-photon sector to reach levels of 10-23--five orders of magnitude more sensitive than the current best bounds.

  14. Highly sensitive visible-blind extreme ultraviolet Ni/4H-SiC Schottky photodiodes with large detection area.

    PubMed

    Hu, Jun; Xin, Xiaobin; Zhao, Jian H; Yan, Feng; Guan, Bing; Seely, John; Kjornrattanawanich, Benjawan

    2006-06-01

    Ni/4H-SiC Schottky photodiodes of 5 mm x 5 mm area have been fabricated and characterized. The photodiodes show less than 0.1 pA dark current at -4 V and an ideality factor of 1.06. A quantum efficiency (QE) between 3 and 400 nm has been calibrated and compared with Si photodiodes optimized for extreme ultraviolet (EUV) detection. In the EUV region, the QE of SiC detectors increases from 0.14 electrons/photon at 120 nm to 30 electrons/photon at 3 nm. The mean energy of electron-hole pair generation of 4H-SiC estimated from the spectral QE is found to be 7.9 eV.

  15. Stabilizing Semiconductor Devices With Hydrogen

    NASA Technical Reports Server (NTRS)

    Overhauser, Albert W.; Maserjian, Joseph

    1989-01-01

    Damage by radiation healed rapidly. Feature provides continuous, rapid recovery of devices from degradation caused by hot electrons, photons, and ionizing radiation. Several candidate sites for palladium film catalysts, inserted during manufacture as integral parts of devices. Paladium films made by evaporation, sputtering, or chemical-vapor deposition. If additional storage required, thick layer of palladium plated on inside of package surrounding device. Hydrogen stored by exposing palladium to hydrogen gas just before package sealed hermetically.

  16. Single-chip microprocessor that communicates directly using light.

    PubMed

    Sun, Chen; Wade, Mark T; Lee, Yunsup; Orcutt, Jason S; Alloatti, Luca; Georgas, Michael S; Waterman, Andrew S; Shainline, Jeffrey M; Avizienis, Rimas R; Lin, Sen; Moss, Benjamin R; Kumar, Rajesh; Pavanello, Fabio; Atabaki, Amir H; Cook, Henry M; Ou, Albert J; Leu, Jonathan C; Chen, Yu-Hsin; Asanović, Krste; Ram, Rajeev J; Popović, Miloš A; Stojanović, Vladimir M

    2015-12-24

    Data transport across short electrical wires is limited by both bandwidth and power density, which creates a performance bottleneck for semiconductor microchips in modern computer systems--from mobile phones to large-scale data centres. These limitations can be overcome by using optical communications based on chip-scale electronic-photonic systems enabled by silicon-based nanophotonic devices. However, combining electronics and photonics on the same chip has proved challenging, owing to microchip manufacturing conflicts between electronics and photonics. Consequently, current electronic-photonic chips are limited to niche manufacturing processes and include only a few optical devices alongside simple circuits. Here we report an electronic-photonic system on a single chip integrating over 70 million transistors and 850 photonic components that work together to provide logic, memory, and interconnect functions. This system is a realization of a microprocessor that uses on-chip photonic devices to directly communicate with other chips using light. To integrate electronics and photonics at the scale of a microprocessor chip, we adopt a 'zero-change' approach to the integration of photonics. Instead of developing a custom process to enable the fabrication of photonics, which would complicate or eliminate the possibility of integration with state-of-the-art transistors at large scale and at high yield, we design optical devices using a standard microelectronics foundry process that is used for modern microprocessors. This demonstration could represent the beginning of an era of chip-scale electronic-photonic systems with the potential to transform computing system architectures, enabling more powerful computers, from network infrastructure to data centres and supercomputers.

  17. Automated Monte Carlo biasing for photon-generated electrons near surfaces.

    SciTech Connect

    Franke, Brian Claude; Crawford, Martin James; Kensek, Ronald Patrick

    2009-09-01

    This report describes efforts to automate the biasing of coupled electron-photon Monte Carlo particle transport calculations. The approach was based on weight-windows biasing. Weight-window settings were determined using adjoint-flux Monte Carlo calculations. A variety of algorithms were investigated for adaptivity of the Monte Carlo tallies. Tree data structures were used to investigate spatial partitioning. Functional-expansion tallies were used to investigate higher-order spatial representations.

  18. Coincidence measurements of electron-impact coherence parameters for e-He scattering in the full range of scattering angles

    SciTech Connect

    Klosowski, Lukasz; Piwinski, Mariusz; Dziczek, Dariusz; Pleskacz, Katarzyna; Chwirot, Stanislaw

    2009-12-15

    Electron impact coherence parameters for inelastic e-He scattering have been measured for the excitation to the 2 {sup 1}P{sub 1} state at collision energy of 100 eV. The experiment was conducted using angular correlation electron-photon coincidence technique with a magnetic angle changer allowing measurements in full range of scattering angles. The results are compared with other experimental data and theoretical predictions available for this collisional system.

  19. Elastically Decoupling Dark Matter.

    PubMed

    Kuflik, Eric; Perelstein, Maxim; Lorier, Nicolas Rey-Le; Tsai, Yu-Dai

    2016-06-03

    We present a novel dark matter candidate, an elastically decoupling relic, which is a cold thermal relic whose present abundance is determined by the cross section of its elastic scattering on standard model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross section with electrons, photons and/or neutrinos in the 10^{-3}-1  fb range.

  20. Prototypes of Self-Powered Radiation Detectors Employing Intrinsic High-Energy Current (HEC) (POSTPRINT)

    DTIC Science & Technology

    2016-01-01

    most efficient when the incident x - rays interact with high- Z materials by photoelectric absorption , resulting in photo- electrons, Auger electrons...effect of direct energy conversion of x - rays via selfpowered Auger- and photocurrent, potentially suitable to practical radiation detection and...plane-parallel 60-120 kVp x - ray beams. For the experimental design and verification, the authors performed coupled electron-photon radiation transport

  1. Single-chip microprocessor that communicates directly using light

    NASA Astrophysics Data System (ADS)

    Sun, Chen; Wade, Mark T.; Lee, Yunsup; Orcutt, Jason S.; Alloatti, Luca; Georgas, Michael S.; Waterman, Andrew S.; Shainline, Jeffrey M.; Avizienis, Rimas R.; Lin, Sen; Moss, Benjamin R.; Kumar, Rajesh; Pavanello, Fabio; Atabaki, Amir H.; Cook, Henry M.; Ou, Albert J.; Leu, Jonathan C.; Chen, Yu-Hsin; Asanović, Krste; Ram, Rajeev J.; Popović, Miloš A.; Stojanović, Vladimir M.

    2015-12-01

    Data transport across short electrical wires is limited by both bandwidth and power density, which creates a performance bottleneck for semiconductor microchips in modern computer systems—from mobile phones to large-scale data centres. These limitations can be overcome by using optical communications based on chip-scale electronic-photonic systems enabled by silicon-based nanophotonic devices8. However, combining electronics and photonics on the same chip has proved challenging, owing to microchip manufacturing conflicts between electronics and photonics. Consequently, current electronic-photonic chips are limited to niche manufacturing processes and include only a few optical devices alongside simple circuits. Here we report an electronic-photonic system on a single chip integrating over 70 million transistors and 850 photonic components that work together to provide logic, memory, and interconnect functions. This system is a realization of a microprocessor that uses on-chip photonic devices to directly communicate with other chips using light. To integrate electronics and photonics at the scale of a microprocessor chip, we adopt a ‘zero-change’ approach to the integration of photonics. Instead of developing a custom process to enable the fabrication of photonics, which would complicate or eliminate the possibility of integration with state-of-the-art transistors at large scale and at high yield, we design optical devices using a standard microelectronics foundry process that is used for modern microprocessors. This demonstration could represent the beginning of an era of chip-scale electronic-photonic systems with the potential to transform computing system architectures, enabling more powerful computers, from network infrastructure to data centres and supercomputers.

  2. Electromagnetic Radiation in the Atmosphere Generated by Excess Negative Charge in a Nuclear-Electromagnetic Cascade

    NASA Astrophysics Data System (ADS)

    Malyshevsky, V. S.; Fomin, G. V.

    2017-01-01

    On the basis of the analytical model "PARMA" (PHITS-based Analytical Radiation Model in the Atmosphere), developed to model particle fluxes of secondary cosmic radiation in the Earth's atmosphere, we have calculated the characteristics of radio waves emitted by excess negative charge in an electromagnetic cascade. The results may be of use in an analysis of experimental data on radio emission of electron-photon showers in the atmosphere.

  3. Interpretation of the radioactive background observed in the OSO-7 gamma-ray monitor

    NASA Technical Reports Server (NTRS)

    Dyer, C. S.; Dunphy, P.; Forest, D. J.; Chupp, E. L.

    1975-01-01

    Application of a spallation activation calculation to the OSO-7 gamma-ray monitor background shows that major line features and about 30% of the continuum can be understood as activation of the central detector crystal by trapped protons. Weaker line features arise from activation of materials unshielded by the anticoincidence cup, while the remaining continuum and annihilation line would seem to come largely from electron-photon cascades originating in the spacecraft.

  4. Study of photonuclear muon interactions at Baksan underground scintillation telescope

    NASA Technical Reports Server (NTRS)

    Bakatanov, V. N.; Chudakov, A. E.; Dadykin, V. L.; Novoseltsev, Y. F.; Achkasov, V. M.; Semenov, A. M.; Stenkin, Y. V.

    1985-01-01

    The method of pion-muon-electron decays recording was used to distinguish between purely electron-photon and hadronic cascades, induced by high energy muons underground. At energy approx. 1 Tev a ratio of the number of hadronic to electromagnetic cascades was found equal 0.11 + or - .03 in agreement with expectation. But, at an energy approx. 4 Tev a sharp increase of this ratio was indicated though not statistically sound (0.52 + or - .13).

  5. Nonlinear Material Response to Very Rapid Energy Deposition

    DTIC Science & Technology

    1990-03-23

    including optical windows, geophysical solids, polymers , composites, etc.) to intense impulsive loading is central to many Air Force pro- grams and...picture of dielectric breakdown at dc to optical frequencies has dramatically changed in the last five years due to the work of Fischetti, DiMaria, Cartier ...and co-workers at IBM and our group at Washington State University. Cartier et al.6 were able to measure the electron-photon scattering rates in

  6. Alignment of multiradiation isocenters for megavoltage photon beam.

    PubMed

    Zhang, Yin; Ding, Kai; Cowan, Garth; Tryggestad, Erik; Armour, Elwood; Wang, Ken Kang-Hsin

    2015-11-08

    The accurate measurement of the linear accelerator (linac) radiation isocenter is critical, especially for stereotactic treatment. Traditional quality assurance (QA) procedure focuses on the measurement of single radiation isocenter, usually of 6 megavoltage (MV) photon beams. Single radiation isocenter is also commonly assumed in treatment planning systems (TPS). Due to different flattening filters and bending magnet and steering parameters, the radiation isocenter of one energy mode can deviate from another if no special effort was devoted. We present the first experience of the multiradiation isocenters alignment on an Elekta linac, as well as its corresponding QA procedure and clinical impact. An 8 mm ball-bearing (BB) phantom was placed at the 6 MV radiation isocenter using an Elekta isocenter search algorithm, based on portal images. The 3D radiation isocenter shifts of other photon energy modes relative to the 6 MV were determined. Beam profile scanning for different field sizes was used as an independent method to determine the 2D multiradiation isocenters alignment. To quantify the impact of radiation isocenter offset on targeting accuracy, the 10 MV radiation isocenter was manually offset from that for 6 MV by adjusting the bending magnet current. Because our table isocenter was mechanically aligned to the 6 MV radiation isocenter, the deviation of the table isocentric rotation from the "shifted" 10 MV radiation isocenter after bending magnet adjustment was assessed. Winston-Lutz test was also performed to confirm the overall radiation isocenter positioning accuracy for all photon energies. The portal image method showed the radiation isocenter of the 10 MV flattening filter-free mode deviated from others before beam parameter adjustment. After the adjustment, the deviation was greatly improved from 0.96 to 0.35 mm relative to the 6 MV radiation isocenter. The same finding was confirmed by the profile-scanning method. The maximum deviation of the table

  7. Dynamic dosimetry and edema detection in prostate brachytherapy: a complete system

    NASA Astrophysics Data System (ADS)

    Jain, A.; Deguet, A.; Iordachita, I.; Chintalapani, G.; Blevins, J.; Le, Y.; Armour, E.; Burdette, C.; Song, D.; Fichtinger, G.

    2008-03-01

    Purpose: Brachytherapy (radioactive seed insertion) has emerged as one of the most effective treatment options for patients with prostate cancer, with the added benefit of a convenient outpatient procedure. The main limitation in contemporary brachytherapy is faulty seed placement, predominantly due to the presence of intra-operative edema (tissue expansion). Though currently not available, the capability to intra-operatively monitor the seed distribution, can make a significant improvement in cancer control. We present such a system here. Methods: Intra-operative measurement of edema in prostate brachytherapy requires localization of inserted radioactive seeds relative to the prostate. Seeds were reconstructed using a typical non-isocentric C-arm, and exported to a commercial brachytherapy delivery system. Technical obstacles for 3D reconstruction on a non-isocentric C-arm include pose-dependent C-arm calibration; distortion correction; pose estimation of C-arm images; seed reconstruction; and C-arm to TRUS registration. Results: In precision-machined hard phantoms with 40-100 seeds and soft tissue phantoms with 45-87 seeds, we correctly reconstructed the seed implant shape with an average 3D precision of 0.35 mm and 0.24 mm, respectively. In a DoD Phase-1 clinical trial on 6 patients with 48-82 planned seeds, we achieved intra-operative monitoring of seed distribution and dosimetry, correcting for dose inhomogeneities by inserting an average of 4.17 (1-9) additional seeds. Additionally, in each patient, the system automatically detected intra-operative seed migration induced due to edema (mean 3.84 mm, STD 2.13 mm, Max 16.19 mm). Conclusions: The proposed system is the first of a kind that makes intra-operative detection of edema (and subsequent re-optimization) possible on any typical non-isocentric C-arm, at negligible additional cost to the existing clinical installation. It achieves a significantly more homogeneous seed distribution, and has the potential to

  8. A study of Winston-Lutz test on two different electronic portal imaging devices and with low energy imaging.

    PubMed

    Ravindran, Paul B

    2016-09-01

    Stereotactic radiosurgery requires sub-millimetre accuracy in patient positioning and target localization. Therefore, verification of the linear accelerator (linac) isocentre and the laser alignment to the isocentre is performed in some clinics prior to the treatment using the Winston-Lutz (W-L) test with films and more recently with images obtained using the electronic portal imaging devices (EPID). The W-L test is performed by acquiring EPID images of a radio-opaque ball of 6 mm diameter (the W-L phantom) placed at the isocentre of the linac at various gantry and table angles, with a predefined small square or circular radiation beam. In this study, the W-L test was performed on two linacs having EPIDs of different size and resolution, viz, a TrueBeam™ linac with aS1000 EPID of size 40 × 30 cm(2) with 1024 × 768 pixel resolution and an EDGE™ linac having an EPID of size 43 × 43 cm(2) with pixel resolution of 1280 × 1280. In order to determine the displacement of the radio-opaque ball centre from the radiation beam centre of the W-L test, an in-house MATLAB™ image processing code was developed using morphological operations. The displacement in radiation beam centre at each gantry and couch position was obtained by determining the distance between the radiation field centre and the radio-opaque ball centre for every image. Since the MATLAB code was based on image processing that was dependent on the image contrast and resolution, the W-L test was also compared for images obtained with different beam energies. The W-L tests were performed for 6 and 8 MV beams on the TrueBeam™ linac and for 2.5 and 6 MV beams on the EDGE™ linac with a higher resolution EPID. It was observed that the images obtained with the EPID of higher resolution resulted in same accuracy in the determination of the displacement between the centres of the radio-opaque ball and the radiation beam, and significant difference was not observed with images acquired with

  9. ELECTRON BEAM ION SOURCE PREINJECTOR PROJECT (EBIS) CONCEPTUAL DESIGN REPORT.

    SciTech Connect

    ALESSI, J.; BARTON, D.; BEEBE, E.; GASSNER, D.; GRANDINETTI, R.; HSEUH, H.; JAVIDFAR, A.; KPONOU, A.; LAMBIASE, R.; LESSARD, E.; LOCKEY, R.; LODESTRO, V.; MAPES, M.; MIRABELLA, D.; NEHRING, T.; OERTER, B.; PENDZICK, A.; PIKIN, A.; RAPARIA, D.; RITTER, J.; ROSER, T.; RUSSO, T.; SNYDSTRUP, L.; WILINSKI, M.; ZALTSMAN, A.; ZHANG, S.

    2005-09-01

    This report describes a new heavy ion pre-injector for the Relativistic Heavy Ion Collider (RHIC) based on a high charge state Electron Beam Ion Source (EBIS), a Radio Frequency Quadrupole (RFQ) accelerator, and a short Linear accelerator (Linac). The highly successful development of an EBIS at Brookhaven National Laboratory (BNL) now makes it possible to replace the present pre-injector that is based on an electrostatic Tandem with a reliable, low maintenance Linac-based pre-injector. Linac-based preinjectors are presently used at most accelerator and collider facilities with the exception of RHIC, where the required gold beam intensities could only be met with a Tandem until the recent EBIS development. EBIS produces high charge state ions directly, eliminating the need for the two stripping foils presently used with the Tandem. Unstable stripping efficiencies of these foils are a significant source of luminosity degradation in RHIC. The high reliability and flexibility of the new Linac-based pre-injector will lead to increased integrated luminosity at RHIC and is an essential component for the long-term success of the RHIC facility. This new pre-injector, based on an EBIS, also has the potential for significant future intensity increases and can produce heavy ion beams of all species including uranium beams and, as part of a future upgrade, might also be used to produce polarized {sup 3}He beams. These capabilities will be critical to the future luminosity upgrades and electron-ion collisions in RHIC. The proposed pre-injector system would also provide for a major enhancement in capability for the NASA Space Radiation Laboratory (NSRL), which utilizes heavy-ion beams from the RHIC complex. EBIS would allow for the acceleration of all important ion species for the NASA radiobiology program, such as, helium, argon, and neon which are unavailable with the present Tandem injector. In addition, the new system would allow for very rapid switching of ion species for

  10. Helical tomotherapy as a means of delivering accelerated partial breast irradiation.

    PubMed

    Hui, Susanta K; Das, Rupak K; Kapatoes, Jeff; Oliviera, Gustavo; Becker, Stuart; Odau, Heath; Fenwick, John D; Patel, Rakesh; Kuske, Robert; Mehta, Minesh; Paliwal, Bhudatt; Mackie, Thomas R; Fowler, Jack F; Welsh, James S

    2004-12-01

    A novel treatment approach utilizing helical tomotherapy for partial breast irradiation for patients with early-stage breast cancer is described. This technique may serve as an alternative to high dose-rate (HDR) interstitial brachytherapy and standard linac-based approaches. Through helical tomotherapy, highly conformal irradiation of target volumes and avoidance of normal sensitive structures can be achieved. Unlike HDR brachytherapy, it is noninvasive. Unlike other linac-based techniques, it provides image-guided adaptive radiotherapy along with intensity modulation. A treatment planning CT scan was obtained as usual on a post-lumpectomy patient undergoing HDR interstitial breast brachytherapy. The patient underwent catheter placement for HDR treatment and was positioned prone on a specially designed position-supporting mattress during CT. The planning target volume (PTV) was defined as the lumpectomy bed plus a 20 mm margin. The prescription dose was 34 Gy (10 fx of 3.4 Gy) in both the CT based HDR and on the tomotherapy plan. Cumulative dose-volume histograms (DVHs) were generated and analyzed for the target, lung, heart, skin, pectoralis muscle, and chest wall for both HDR brachytherapy and helical tomotherapy. Dosimetric coverage of the target with helical tomotherapy was conformal and homogeneous. "Hot spots" (> or =150% isodose line) were present around implanted dwell positions in brachytherapy plan whereas no isodose lines higher than 109% were present in the helical tomotherapy plan. Similar dose coverage was achieved for lung, pectoralis muscle, heart, chest wall and breast skin with the two methods. We also compared our results to that obtained using conventional linac-based three dimensional (3D) conformal accelerated partial breast irradiation. Dose homogeneity is excellent with 3D conformal irradiation, and lung, heart and chest wall dose is less than for either HDR brachytherapy or helical tomotherapy but skin and pectoral muscle doses were higher

  11. Three-dimensional Intraoperative Imaging Modalities in Orthopaedic Surgery: A Narrative Review.

    PubMed

    Qureshi, Sheeraz; Lu, Young; McAnany, Steven; Baird, Evan

    2014-12-01

    Intraoperative imaging and navigation systems have revolutionized orthopaedic surgery for the spine, joints, and orthopaedic trauma. Imaging modalities such as the isocentric C-arm, O-arm imaging, and intraoperative MRI or navigation systems allow the visualization of surgical instruments and implants relative to a three-dimensional CT image or MRI. Studies show that these technologies lower the rates of implant misplacement and inadequate fracture reduction, thereby improving surgical outcomes and reducing reoperation rates. An additional benefit is reduced radiation exposure compared with that for conventional fluoroscopy. Concerns surrounding adoption of these technologies include cost and increased operating times, but improvements in design and protocol may improve the integration of these imaging modalities into the operating room.

  12. The direct measurement using an imaging plate for coincidence of radiation centre and laser position in external radiation therapy.

    PubMed

    Terunuma, Toshiyuki; Sakae, Takeji; Nohtomi, Akihiro; Tsunashima, Yoshikazu

    2003-02-21

    A new method of quality assurance has been studied to measure coincidence of the radiation centre and a patient-setup laser position on a transverse plane to the beam at the isocentre. This measurement is achieved by using an imaging plate (IP). When radiation is applied to an IP, the energy is stored as trapped electrons. The number of electrons is decreased by local laser exposure. As a result, the radiation field produced by external beam irradiation is recorded as 'positive' information and the position of the patient-setup laser is recorded as 'negative' on an IP. The advantages of this method are the direct measurement, short time and high resolution. These are required for daily and monthly quality checks. We confirmed the advantage of this method by an experiment using a proton beam.

  13. Sensor-based hip control with hybrid neuroprosthesis for walking in paraplegia.

    PubMed

    To, Curtis S; Kobetic, Rudi; Bulea, Thomas C; Audu, Musa L; Schnellenberger, John R; Pinault, Gilles; Triolo, Ronald J

    2014-01-01

    The objectives of this study were to test whether a hybrid neuroprosthesis (HNP) with an exoskeletal variable-constraint hip mechanism (VCHM) combined with a functional neuromuscular stimulation (FNS) controller can maintain upright posture with less upper-limb support and improve gait speed as compared with walking with either an isocentric reciprocating gait orthosis (IRGO) or FNS only. The results show that walking with the HNP significantly reduced forward lean in FNS-only walking and the maximum upper-limb forces by 42% and 19% as compared with the IRGO and FNS-only gait, respectively. Walking speed increased significantly with VCHM as compared with 1:1 reciprocal coupling and by 15% when using the sensor-based FNS controller as compared with HNP with fixed baseline stimulation without the controller active.

  14. The South African National Accelerator Centre: particle therapy and isotope production programmes

    NASA Astrophysics Data System (ADS)

    Jones, D. T. L.; Mills, S. J.

    1998-06-01

    The National Accelerator Centre (NAC) provides facilities for basic and applied research, radioisotope production and particle therapy. To date, 851 patients have been treated on the 66 MeV p+Be isocentric neutron therapy unit while 191 patients have been treated (mainly for intracranial conditions) on the 200 MeV horizontal proton beam facility. A variety of radioisotopes such as 67Ga, 81Rb/ 81Kr, 111In, 123I, and 201Tl are produced on a regular weekly basis, and more than 1000 consignments of radiopharmaceuticals prepared from these radioisotopes are supplied to more than 30 hospitals and private practices throughout South Africa each year. Some non-medical radioisotopes are also produced.

  15. Activation processes in a medical linear accelerator and spatial distribution of activation products.

    PubMed

    Fischer, Helmut W; Tabot, Ben E; Poppe, Björn

    2006-12-21

    Activation products have been identified by in situ gamma spectroscopy at the isocentre of a medical linear accelerator shortly after termination of a high energy photon beam irradiation with 15 x 15 cm field size. Spectra have been recorded either with an open or with a closed collimator. Whilst some activation products disappear from the spectrum with closed collimator or exhibit reduced count rates, others remain with identical intensity. The former isotopes are neutron-deficient and mostly decay by positron emission or electron capture; the latter have neutron excess and decay by beta(-) emission. This new finding is consistent with the assumption that photons in the primary beam produce activation products by (gamma, n) reactions in the treatment head and subsequently the neutrons created in these processes undergo (n, gamma) reactions creating activation products in a much larger area. These findings are expected to be generally applicable to all medical high energy linear accelerators.

  16. Two new DOSXYZnrc sources for 4D Monte Carlo simulations of continuously variable beam configurations, with applications to RapidArc, VMAT, TomoTherapy and CyberKnife

    NASA Astrophysics Data System (ADS)

    Lobo, Julio; Antoniu Popescu, I.

    2010-08-01

    We present two new Monte Carlo sources for the DOSXYZnrc code, which can be used to compute dose distributions due to continuously variable beam configurations. These sources support a continuously rotating gantry and collimator, dynamic multileaf collimator (MLC) motion, variable monitor unit (MU) rate, couch rotation and translation in any direction, arbitrary isocentre motion with respect to the patient and variable source-to-axis distance (SAD). These features make them applicable to Monte Carlo simulations for RapidArc™, Elekta VMAT, TomoTherapy™ and CyberKnife™. Unique to these sources is the synchronization between the motion in the DOSXYZnrc geometry and the motion within the linac head, represented by a shared library (either a BEAMnrc accelerator with dynamic component modules, or an external library). The simulations are achieved in single runs, with no intermediate phase space files.

  17. Design of Injector Systems for LUX

    SciTech Connect

    Lidia, Steven M.

    2004-07-01

    The LUX concept [1] for a superconducting recirculating linac based ultrafast x-ray facility features a unique high-brightness electron beam injector. The design of the injector complex that meets the baseline requirements for LUX is presented. A dual-rf gun injector provides both high-brightness electron beams to drive the cascaded, seeded harmonic generation VUV-soft x-ray FELs as well as the ultra- low-vertical emittance (''flat'') beams that radiate in hard x-ray spontaneous emission synchrotron beamlines. Details of the injector complex design and performance characteristics are presented. Contributions by the thermal emittance and optical pulse shaping to the beam emission at the photocathode and to the beam dynamics throughout the injector are presented. Techniques that seek to optimize the injector performance, as well as constraints that prevent straightforward optimization, are discussed.

  18. Phase Space Tomography Using the Cornell ERL DC Gun

    SciTech Connect

    Bazarov, Ivan; Dunham, Bruce; Li, Yulin; Liu, XianGhong; Hannon, Fay

    2008-07-01

    The brightness and quality of electron beams in linac-based light sources are ultimately limited by the properties of the beam in the injector. It is thus important to have knowledge of the phase space distribution in addition to the rms emittance to provide an insight into high beam brightness formation mechanisms. A tomography technique has been used to reconstruct the transverse phase space of the electron beam delivered from the Cornell University ERL DC gun. The tomography diagnostic utilised three solenoid magnets directly after the DC gun and a view-screen. The injector was operated at 250keV in the emittance dominated regime, and the results showed good agreement to the phase space measured using a slit-screen method and that generated from simulation with the particle tracking code ASTRA. Comparison of various reconstruction methods is provided.

  19. Compact x-ray lasers in the laboratory

    SciTech Connect

    Barletta, W.A.

    1988-10-03

    Compact x-ray lasers in the laboratory can be produced with ultrahigh gradient rf linacs based on recent advances in linac technology by an SLAC-LLNL-LBL collaboration and on the development of bright, high current electron sources by BNL and LANL. The GeV electron beams generated with such accelerators can be converted to soft x rays in the range of 2--10 nm by passage through short period, high field strength wigglers. Alternatively, the beam can pump a low density dielectric to produce x rays via recombination. Such linear light sources can produce trains of picosecond (or shorter) pulses of extremely high spectral brilliance suitable for flash holography of biological specimens in vivo and for studies of fast chemical reactions. 15 refs., 7 figs., 3 tabs.

  20. A high-compression electron gun for C6+ production: concept, simulations and mechanical design

    NASA Astrophysics Data System (ADS)

    Mertzig, Robert; Breitenfeldt, M.; Mathot, S.; Pitters, J.; Shornikov, A.; Wenander, F.

    2017-07-01

    In this paper we report on simulations and the mechanical design of a high-compression electron gun for an Electron Beam Ion Source (EBIS) dedicated for production of high intensity and high repetition rate pulses of bare carbon ions for injection into linac-based hadron therapy facilities. The gun is presently under construction at CERN to be retrofitted into the TwinEBIS test bench for experimental studies. We describe the design constraints, show results of numeric simulations and report on the mechanical design featuring several novel ideas. The reported design makes use of combined-function units with reduced number of mechanical joints that were carefully controlled and tuned during the manufacturing phase. The simulations addressed a wide range of topics including the influence of thermal effects, focusing optics, symmetry-breaking misalignments and injection into a full 5 T field.

  1. Linear accelerator radiosurgery for arteriovenous malformations: Updated literature review.

    PubMed

    Yahya, S; Heyes, G; Nightingale, P; Lamin, S; Chavda, S; Geh, I; Spooner, D; Cruickshank, G; Sanghera, P

    2017-04-01

    Arteriovenous malformations (AVMs) are the leading causing of intra-cerebral haemorrhage. Stereotactic radiosurgery (SRS) is an established treatment for arteriovenous malformations (AVM) and commonly delivered using Gamma Knife within dedicated radiosurgery units. Linear accelerator (LINAC) SRS is increasingly available however debate remains over whether it offers an equivalent outcome. The aim of this project is to evaluate the outcomes using LINAC SRS for AVMs used within a UK neurosciences unit and review the literature to aid decision making across various SRS platforms. Results have shown comparability across platforms and strongly supports that an adapted LINAC based SRS facility within a dynamic regional neuro-oncology department delivers similar outcomes (in terms of obliteration and toxicity) to any other dedicated radio-surgical platform. Locally available facilities can facilitate discussion between options however throughput will inevitably be lower than centrally based dedicated national radiosurgery units.

  2. Observation of pulsed x-ray trains produced by laser-electron Compton scatterings

    SciTech Connect

    Sakaue, Kazuyuki; Washio, Masakazu; Araki, Sakae; Fukuda, Masafumi; Higashi, Yasuo; Honda, Yosuke; Omori, Tsunehiko; Taniguchi, Takashi; Terunuma, Nobuhiro; Urakawa, Junji; Sasao, Noboru

    2009-12-15

    X-ray generation based on laser-electron Compton scattering is one attractive method to achieve a compact laboratory-sized high-brightness x-ray source. We have designed, built, and tested such a source; it combines a 50 MeV multibunch electron linac with a mode-locked 1064 nm laser stored and amplified in a Fabry-Perot optical cavity. We directly observed trains of pulsed x rays using a microchannel plate detector; the resultant yield was found to be 1.2x10{sup 5} Hz in good agreement with prediction. We believe that the result has demonstrated good feasibility of linac-based compact x-ray sources via laser-electron Compton scatterings.

  3. A high-gradient high-duty-factor Rf photo-cathode electron gun

    SciTech Connect

    Rimmer, Robert A.; Hartman, Neal; Lidia, Steven M.; Wang, Shaoheng

    2002-05-22

    We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure.

  4. A high-gradient high-duty-factor RF photo-cathode electron gun

    SciTech Connect

    Robert Rimmer; N. Hartman; S. Lidia; S.H. Wang

    2002-08-01

    We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure.

  5. The high Beta cryo-modules and the associated cryogenic system for the HIE-ISOLDE upgrade at CERN

    SciTech Connect

    Delruelle, N.; Leclercq, Y.; Pirotte, O.; Ramos, D.; Tibaron, P.; Vandoni, G.; Williams, L.

    2014-01-29

    The major upgrade of the energy and intensity of the existing ISOLDE and REX-ISOLDE radioactive ion beam facilities at CERN requires the replacement of most of the existing ISOLDE post-acceleration equipment by a superconducting linac based on quarter-wave resonators housed together with superconducting solenoids in a series of four high-β and two low-β cryo-modules. As well as providing optimum conditions for physics, the cryo-modules need to function under stringent vacuum and cryogenic conditions. We present the detail design and expected cryogenic performance of the high- β cryo-module together with the cryogenic supply and distribution system destined to service the complete superconducting linac.

  6. T-REX Design Considerations for Detection of Concealed 238U

    SciTech Connect

    Pruet, J; McNabb, D P

    2006-02-07

    Here they outline considerations that might inform choices for the design of a laser/linac-based light source used to detect {sup 238}U via excitation of the resonance at 680.11 keV in this isotope. They assume that the principal concern is speed of interrogation and not, e.g., how much radiological dose is imparted during a scan. It is found that if the photon detectors used in the system have an energy resolution better than or comparable to that of the interrogation beam, then to a first approximation the light source should be designed to have the highest possible specific fluence (photons per unit energy per unit time). there is also a weak dependence of scan time on the number of photons emitted per pulse of the light source. A simple formula describing the tradeoff between specific fluence and number of photons per pulse is presented.

  7. Pulsed Photofission Delayed Gamma Ray Detection for Nuclear Material Identification

    SciTech Connect

    John Kavouras; Xianfei Wen; Daren R. Norman; Dante R. Nakazawa; Haori Yang

    2012-11-01

    Innovative systems with increased sensitivity and resolution are in great demand to detect diversion and to prevent misuse in support of nuclear materials management for the U.S. fuel cycle. Nuclear fission is the most important multiplicative process involved in non-destructive active interrogation. This process produces the most easily recognizable signature for nuclear materials. High-energy gamma rays can also excite a nucleus and cause fission through a process known as photofission. After photofission reactions, delayed signals are easily distinguishable from the interrogating radiation. Linac-based, advanced inspection techniques utilizing the fission signals after photofission have been extensively studied for homeland security applications. Previous research also showed that a unique delayed gamma ray energy spectrum exists for each fissionable isotope. Isotopic composition measurement methods based on delayed gamma ray spectroscopy will be the primary focus of this work.

  8. High-gradient high-duty-factor Rf photo-cathode electron gun

    NASA Astrophysics Data System (ADS)

    Rimmer, R. A.; Hartman, N.; Lidia, S. M.; Wang, S.

    2002-05-01

    We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure.

  9. Design of RF chopper system for improving beam quality in FEL injector with thermionic gun

    NASA Astrophysics Data System (ADS)

    Chen, Q.; Qin, B.; Tan, P.; Hu, T.; Pei, Y.; Zhang, F.

    2014-08-01

    For a linac-based Free Electron Laser (FEL), good beam quality largely contributes to the success of the final radiation. An imperfection confronted with the HUST THz-FEL facility is the long beam tail that emerges in the electron gun and exists through the whole beam line. This paper proposes to deploy a chopper system after the electron gun to truncate the beam tails before they enter into the linac. Physical dimensions of the chopper cavity are discussed in detail and we have developed and derived new analytical expressions applying to all frequencies for the optimal design. Also, technical issues of the cavity are considered. Beam dynamic simulation is performed to examine the truncation effect and the results show that more than 78% of the beam tail can be removed effectively, while preserving the emittance and energy spread in acceptable level.

  10. Compact X-ray lasers in the laboratory

    NASA Astrophysics Data System (ADS)

    Barletta, William A.

    1988-10-01

    Compact X-ray lasers in the laboratory can be produced with ultrahigh gradient RF linacs based on recent advances in linac technology by an SLAC-LLNL-LBL collaboration and on the development of bright, high current electron sources by BNL and LANL. The GeV electron beams generated with such accelerators can be converted to soft X-rays in the range of 2 to 10 nm by passage through short period, high field strength wigglers. Alternatively, the beam can pump a low density dielectric to produce X-rays via recombination. Such linear light sources can produce trains of picosecond (or shorter) pulses of extremely high spectral brilliance suitable for flash holography of biological specimens in vivo and for studies of fast chemical reactions.

  11. Important aspects of linac beams for food irradiation

    NASA Astrophysics Data System (ADS)

    McKeown, J.; Jones, R. T.

    1987-04-01

    Linac based irradiators will require careful design before they can be routinely adopted for the radiation processing of food. The transverse emittance and energy spread from simple injectors provide a significant challenge to the design of a beam delivery system which must handle high power especially in photon mode. Any nonuniform current distribution at the plane of the product is further complicated by large dose variations near the air/product interface, even with simple geometries. The paper describes the use of methods developed at AECL to control and monitor linac behaviour as well as electron interactions at the product surface. It also reports on activation cross-section measurements and particularly on neutron yields from composite targets, designed to monitor the energy of accelerators used in food applications.

  12. Single shot transverse emittance measurement from OTR screens in a drift transport section

    NASA Astrophysics Data System (ADS)

    Thomas, C.; Delerue, N.; Bartolini, R.

    2011-07-01

    Single shot transverse emittance measurement is essential to assess the beam quality and performance of new generation light sources such as linac based X-ray Free Electron Lasers (FELs) or laser plasma wakefield accelerators (LPWA). To this end, we have developed a single shot transverse emittance measurement using at least 3 screens inserted in the beam at the same time, measuring the beam size at different positions in a drift space in one single shot. In this paper, we firstly present the theoretical aspects to perform the measurement. We secondly show experimental results obtained at Diamond for a 3 GeV electron beam in the transfer line from the Booster to the Storage Ring, using this thin OTR screens method. Finally, we discuss the results showing the strength of the measurement in comparison with more standard and established emittance measurement, like the quadrupole scan method.

  13. New HOM coupler design for high current SRF cavity

    SciTech Connect

    Xu, W.; Ben-Zvi, I.; Belomestnykh, S.; Hahn, H.; Johnson, E.

    2011-03-28

    Damping higher order modes (HOMs) significantly to avoid beam instability is a challenge for the high current Energy Recovery Linac-based eRHIC at BNL. To avoid the overheating effect and high tuning sensitivity, current, a new band-stop HOM coupler is being designed at BNL. The new HOM coupler has a bandwidth of tens of MHz to reject the fundamental mode, which will avoid overheating due to fundamental frequency shifting because of cooling down. In addition, the S21 parameter of the band-pass filter is nearly flat from first higher order mode to 5 times the fundamental frequency. The simulation results showed that the new couplers effectively damp HOMs for the eRHIC cavity with enlarged beam tube diameter and 2 120{sup o} HOM couplers at each side of cavity. This paper presents the design of HOM coupler, HOM damping capacity for eRHIC cavity and prototype test results.

  14. MIXI: Mobile Intelligent X-Ray Inspection System

    NASA Astrophysics Data System (ADS)

    Arodzero, Anatoli; Boucher, Salime; Kutsaev, Sergey V.; Ziskin, Vitaliy

    2017-07-01

    A novel, low-dose Mobile Intelligent X-ray Inspection (MIXI) concept is being developed at RadiaBeam Technologies. The MIXI concept relies on a linac-based, adaptive, ramped energy source of short X-ray packets of pulses, a new type of fast X-ray detector, rapid processing of detector signals for intelligent control of the linac, and advanced radiography image processing. The key parameters for this system include: better than 3 mm line pair resolution; penetration greater than 320 mm of steel equivalent; scan speed with 100% image sampling rate of up to 15 km/h; and material discrimination over a range of thicknesses up to 200 mm of steel equivalent. Its minimal radiation dose, size and weight allow MIXI to be placed on a lightweight truck chassis.

  15. Ultrafast Science Opportunities with Electron Microscopy

    SciTech Connect

    Durr, Hermann

    2016-04-28

    X-rays and electrons are two of the most fundamental probes of matter. When the Linac Coherent Light Source (LCLS), the world’s first x-ray free electron laser, began operation in 2009, it transformed ultrafast science with the ability to generate laser-like x-ray pulses from the manipulation of relativistic electron beams. This document describes a similar future transformation. In Transmission Electron Microscopy, ultrafast relativistic (MeV energy) electron pulses can achieve unsurpassed spatial and temporal resolution. Ultrafast temporal resolution will be the next frontier in electron microscopy and can ideally complement ultrafast x-ray science done with free electron lasers. This document describes the Grand Challenge science opportunities in chemistry, material science, physics and biology that arise from an MeV ultrafast electron diffraction & microscopy facility, especially when coupled with linac-based intense THz and X-ray pump capabilities.

  16. Liquid sample delivery techniques for serial femtosecond crystallography

    PubMed Central

    Weierstall, Uwe

    2014-01-01

    X-ray free-electron lasers overcome the problem of radiation damage in protein crystallography and allow structure determination from micro- and nanocrystals at room temperature. To ensure that consecutive X-ray pulses do not probe previously exposed crystals, the sample needs to be replaced with the X-ray repetition rate, which ranges from 120 Hz at warm linac-based free-electron lasers to 1 MHz at superconducting linacs. Liquid injectors are therefore an essential part of a serial femtosecond crystallography experiment at an X-ray free-electron laser. Here, we compare different techniques of injecting microcrystals in solution into the pulsed X-ray beam in vacuum. Sample waste due to mismatch of the liquid flow rate to the X-ray repetition rate can be addressed through various techniques. PMID:24914163

  17. Beam dynamics in super-conducting linear accelerator: Problems and solutions

    NASA Astrophysics Data System (ADS)

    Senichev, Yu.; Bogdanov, A.; Maier, R.; Vasyukhin, N.

    2006-03-01

    The linac based on SC cavities has special features. Due to specific requirements the SC cavity is desirable to have a constant geometry of the accelerating cells with limited family number of cavities. All cavities are divided into modules, and each module is housed into one cryostat. First of all, such geometry of cavity leads to a non-synchronism. Secondly, the inter-cryostat drift space parametrically perturbs the longitudinal motion. In this article, we study the non-linear resonant effects due to the inter-cryostat drift space, using the separatrix formalism for a super-conducting linear accelerator [Yu. Senichev, A. Bogdanov, R. Maier, Phys. Rev. ST AB 6 (2003) 124001]. Methods to avoid or to compensate the resonant effect are also presented. We consider 3D beam dynamics together with space charge effects. The final lattice meets to all physical requirements.

  18. SU-E-T-632: A Dosimetric Comparison of the 3D-CRT Planning of Chest Wall in Post-Mastectomy Breast Cancer Patients, with and Without Breast Board Setup

    SciTech Connect

    Muzaffar, Ambreen; Masood, Asif; Ullah, Haseeb; Mehmood, Kashif; Qasim, Uzma; Afridi, M. Ali; Khan, Salim; Hameed, Abdul

    2014-06-15

    Purpose: Breast boards are used in breast radiation which increases normal lung and heart doses, when supraclavicular field is included. Therefore, in this study through dose volume histogram (DVHs), lung and heart doses comparison was done between two different setups i.e. with and without breast board, for the treatment of left chest wall and supraclavicular fossa in postmastectomy left breast cancer. Methods: In this study, CT-Simulation scans of ten breast cancer patients were done with and without breast board, at Shifa International Hospitals Islamabad, to investigate the differences between the two different setups of the irradiation of left chest wall in terms of lung and heart doses. For immobilization, support under the neck, shoulders and arms was used. Precise PLAN 2.15 treatment planning system (TPS) was used for 3D-CRT planning. The total prescribed dose for both the plans was 5000 cGy/25 fractions. The chest wall was treated with a pair of tangential photon fields and the upper supraclavicular nodal regions were treated with an anterior photon field. A mono-isocentric technique was used to match the tangential fields with the anterior field at the isocentre. The dose volume histogram was used to compare the doses of heart and ipsilateral lung. Results: Both the plans of each patient were generated and compared. DVH results showed that for the same PTV dose coverage, plans without breast board resulted in a reduction of lung and heart doses compared with the plans with breast board. There was significant reductions in V20, V<25 and mean doses for lung and V<9 and mean doses for heart. Conclusion: In comparison of both the plans, setup without breast board significantly reduced the dose-volume of the ipsilateral lung and heart in left chest wall patients. Waived registration request has been submitted.

  19. Pencil beam scanning dosimetry for large animal irradiation

    PubMed Central

    Lin, Liyong; Solberg, Timothy D.; Carabe, Alexandro; Mcdonough, James E.; Diffenderfer, Eric; Sanzari, Jenine K.; Kennedy, Ann R.; Cengel, Keith

    2014-01-01

    The space radiation environment imposes increased dangers of exposure to ionizing radiation, particularly during a solar particle event. These events consist primarily of low-energy protons that produce a highly inhomogeneous depth–dose distribution. Here we describe a novel technique that uses pencil beam scanning at extended source-to-surface distances and range shifter (RS) to provide robust but easily modifiable delivery of simulated solar particle event radiation to large animals. Thorough characterization of spot profiles as a function of energy, distance and RS position is critical to accurate treatment planning. At 105 MeV, the spot sigma is 234 mm at 4800 mm from the isocentre when the RS is installed at the nozzle. With the energy increased to 220 MeV, the spot sigma is 66 mm. At a distance of 1200 mm from the isocentre, the Gaussian sigma is 68 mm and 23 mm at 105 MeV and 220 MeV, respectively, when the RS is located on the nozzle. At lower energies, the spot sigma exhibits large differences as a function of distance and RS position. Scan areas of 1400 mm (superior–inferior) by 940 mm (anterior–posterior) and 580 mm by 320 mm are achieved at the extended distances of 4800 mm and 1200 mm, respectively, with dose inhomogeneity <2%. To treat large animals with a more sophisticated dose distribution, spot size can be reduced by placing the RS closer than 70 mm to the surface of the animals, producing spot sigmas below 6 mm. PMID:24855043

  20. Pencil beam scanning dosimetry for large animal irradiation.

    PubMed

    Lin, Liyong; Solberg, Timothy D; Carabe, Alexandro; Mcdonough, James E; Diffenderfer, Eric; Sanzari, Jenine K; Kennedy, Ann R; Cengel, Keith

    2014-09-01

    The space radiation environment imposes increased dangers of exposure to ionizing radiation, particularly during a solar particle event. These events consist primarily of low-energy protons that produce a highly inhomogeneous depth-dose distribution. Here we describe a novel technique that uses pencil beam scanning at extended source-to-surface distances and range shifter (RS) to provide robust but easily modifiable delivery of simulated solar particle event radiation to large animals. Thorough characterization of spot profiles as a function of energy, distance and RS position is critical to accurate treatment planning. At 105 MeV, the spot sigma is 234 mm at 4800 mm from the isocentre when the RS is installed at the nozzle. With the energy increased to 220 MeV, the spot sigma is 66 mm. At a distance of 1200 mm from the isocentre, the Gaussian sigma is 68 mm and 23 mm at 105 MeV and 220 MeV, respectively, when the RS is located on the nozzle. At lower energies, the spot sigma exhibits large differences as a function of distance and RS position. Scan areas of 1400 mm (superior-inferior) by 940 mm (anterior-posterior) and 580 mm by 320 mm are achieved at the extended distances of 4800 mm and 1200 mm, respectively, with dose inhomogeneity <2%. To treat large animals with a more sophisticated dose distribution, spot size can be reduced by placing the RS closer than 70 mm to the surface of the animals, producing spot sigmas below 6 mm. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  1. The influence of new medial linkage orthosis on walking and independence in spinal cord injury patients: a pilot study

    PubMed Central

    Bani, Monireh Ahmadi; Arazpour, Mokhtar; Farahmand, Farzam; Mousavi, Mohammad Ebrahim; Samadian, Mohammad; Kashani, Reza Vahab; Hutchins, Stephen William

    2016-01-01

    In an effort to overcome the disadvantages of reciprocating gait orthoses (RGOs) and medial linkage orthoses (MLOs), a new design of MLO was developed. Therefore the aim of this study was comparison effect of a new reciprocating MLO and traditional isocentric RGO on gait parameters and functional independence (orthosis donning and doffing time) in spinal cord injury (SCI) subjects to provide more evidence of its efficacy. Four people with motor incomplete SCI participated in this study. Each participant was fitted with an MLO and isocentric reciprocating gait orthosis (IRGO) to enable a comparison of walking speed, cadence and endurance to be performed. There were no statistically significant differences demonstrated in temporal–spatial parameters between the orthotic walking conditions in this study, but walking with the MLO improved the stride length and speed of walking by 28.57 and 40.9% compared with walking with an IRGO as a control condition. Hip flexion occurred predominantly during single-support phases, with negligible motion during double-support phases. The first and second Subjects had hip kinematic pattern more near normal when they walked with medial linkage reciprocal gait orthosis (MLRGO) in comparison with IRGO. There was significant difference between donning and doffing in two conditions (P=0.046) but there was not significant difference between two conditions in standing and sitting although these two conditions improved by new MLO. The new MLO provided a quicker and more independent gait compared with IRGO, in addition the new MLO made it easier for subjects to get from sitting to standing and from standing to sitting. PMID:28053735

  2. SU-E-T-501: Initial Orthovoltage Beam Profile Analysis of a Small Brass MLC

    SciTech Connect

    Loughery, B; Snyder, M

    2015-06-15

    Purpose To create brass leaves for an orthovoltage MLC and take initial beam profile measurements. Methods The low-energy MLC was designed in previous work. Brass was chosen for its self-lubrication and low cost. Stock brass rectangles (30cm × 1.0cm × 0.5cm) were ordered with pre-cut gear rack along the topmost long edges. Leaf designs were translated into G-code, then cut with a Tormach CNC-1100 mill. Intense bowing was observed in the beam direction, which required straightening via an in-house jig. Straightened leaves were placed into MLC assembly and mounted to a 320 kVp orthovoltage tube. EDR2 film was irradiated in four situations: MLC open so one edge was isocentric, and MLC open more than isocentric, completely closed MLC, and an open field shot with the MLC removed. The first two scans tested penumbra for our rectangular edges due to unfocused design. The final two scans tested transmission and interleaf leakage. All four experiments were set to 120 kVp and 10 mA for two minutes. Results Transmission and interleaf leakage were found to be zero. Interleaf leakage is faintly visible on film, but undetected by our film scanner despite high spatial resolution. Penumbra at isocenter was found to be 0.72mm, which matched the penumbras of true field edges. Penumbra off-isocenter was 1.1mm. Mechanically, leaves are moving smoothly once straightened. Conclusion Beam profiles through our brass MLC are acceptable. Leaves attenuate and move as designed. Looking forward, we intend to animate our MLC to deliver more complicated treatment plans.

  3. A modular approach to intensity-modulated arc therapy optimization with noncoplanar trajectories

    NASA Astrophysics Data System (ADS)

    Papp, Dávid; Bortfeld, Thomas; Unkelbach, Jan

    2015-07-01

    Utilizing noncoplanar beam angles in volumetric modulated arc therapy (VMAT) has the potential to combine the benefits of arc therapy, such as short treatment times, with the benefits of noncoplanar intensity modulated radiotherapy (IMRT) plans, such as improved organ sparing. Recently, vendors introduced treatment machines that allow for simultaneous couch and gantry motion during beam delivery to make noncoplanar VMAT treatments possible. Our aim is to provide a reliable optimization method for noncoplanar isocentric arc therapy plan optimization. The proposed solution is modular in the sense that it can incorporate different existing beam angle selection and coplanar arc therapy optimization methods. Treatment planning is performed in three steps. First, a number of promising noncoplanar beam directions are selected using an iterative beam selection heuristic; these beams serve as anchor points of the arc therapy trajectory. In the second step, continuous gantry/couch angle trajectories are optimized using a simple combinatorial optimization model to define a beam trajectory that efficiently visits each of the anchor points. Treatment time is controlled by limiting the time the beam needs to trace the prescribed trajectory. In the third and final step, an optimal arc therapy plan is found along the prescribed beam trajectory. In principle any existing arc therapy optimization method could be incorporated into this step; for this work we use a sliding window VMAT algorithm. The approach is demonstrated using two particularly challenging cases. The first one is a lung SBRT patient whose planning goals could not be satisfied with fewer than nine noncoplanar IMRT fields when the patient was treated in the clinic. The second one is a brain tumor patient, where the target volume overlaps with the optic nerves and the chiasm and it is directly adjacent to the brainstem. Both cases illustrate that the large number of angles utilized by isocentric noncoplanar VMAT plans

  4. SU-E-T-432: A Rapid and Comprehensive Procedure for Daily Proton QA

    SciTech Connect

    Zhao, T; Sun, B; Grantham, K; Knutson, N; Santanam, L; Goddu, S; Klein, E

    2014-06-01

    Purpose: The objective is to develop a rapid and comprehensive daily QA procedure implemented at the S. Lee Kling Proton Therapy Center at Barnes-Jewish Hospital. Methods: A scribed phantom with imbedded fiducials is used for checking lasers accuracy followed by couch isocentricity and for X-ray imaging congruence with isocenter. A Daily QA3 device (Sun Nuclear, FL) was used to check output, range and profiles. Five chambers in the central region possess various build-ups. After converting the thickness of the inherent build-ups into water equivalent thickness (WET) for proton, range of any beam can be checked with additional build-up on the Daily QA3 device. In our procedure, 3 beams from 3 bands (large, small and deep) with nominal range of 20 cm are checked daily. 17cm plastic water with WET of 16.92cm are used as additional build-up so that four chambers sit on the SOBP plateau at various depths and one sit on the distal fall off. Reading from the five chambers are fitted to an error function that has been parameterized to match the SOBP with the same nominal range. Shifting of the error function to maximize the correlation between measurements and the error function is deemed as the range shift from the nominal value. Results: We have found couch isocentricity maintained over 180 degrees. Imaging system exhibits accuracy in regard to imaging and mechanical isocenters. Ranges are within 1mm accuracy from measurements in water tank, and sensitive to change of sub-millimeter. Data acquired since the start of operation show outputs, profiles and range stay within 1% or 1mm from baselines. The whole procedure takes about 40 minutes. Conclusion: Taking advantage of the design of Daily QA3 device turns the device originally designed for photon and electron into a comprehensive and rapid tool for proton daily QA.

  5. A robust measurement point for dose verification in delivery quality assurance for a robotic radiosurgery system.

    PubMed

    Kurosu, Keita; Sumida, Iori; Shiomi, Hiroya; Mizuno, Hirokazu; Yamaguchi, Hiroko; Okubo, Hirofumi; Tamari, Keisuke; Seo, Yuji; Suzuki, Osamu; Ota, Seiichi; Inoue, Shinichi; Ogawa, Kazuhiko

    2017-05-01

    In this CyberKnife® dose verification study, we investigated the effectiveness of the novel potential error (PE) concept when applied to the determination of a robust measurement point for targeting errors. PE was calculated by dividing the differences between the maximum increases and decreases in dose distributions by the original distribution after obtaining the former by shifting the source-to-axis and off-axis distances of each beam by ±1.0 mm. Thus, PE values and measurement point dose heterogeneity were analyzed in 48 patients who underwent CyberKnife radiotherapy. Sixteen patients who received isocentric dose delivery were set as the control group, whereas 32 who received non-isocentric dose delivery were divided into two groups of smaller PE (SPE) and larger PE (LPE) by using their median PE value. The mean dose differences (± standard deviations) were 1.0 ± 0.9%, 0.5 ± 1.4% and 4.1 ± 2.8% in the control, SPE and LPE groups, respectively. We observed significant correlations of the dose difference with the PE value (r = 0.582, P < 0.001) and dose heterogeneity (r = 0.471, P < 0.001). We concluded that when determining a robust measurement point for CyberKnife point dose verification, PE evaluation was more effective than the conventional dose heterogeneity-based method that introduced optimal measurement point dose heterogeneity of <10% across the detector. © The Author 2016. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  6. Involved field radiation for Hodgkin's lymphoma: The actual dose to breasts in close proximity

    SciTech Connect

    Dabaja, Bouthaina; Wang Zhonglo; Stovall, Marilyn; Baker, Jamie S.; Smith, Susan A.; Khan, Meena; Ballas, Leslie; Salehpour, Mohammad R.

    2012-01-01

    To decrease the risk of late toxicities in Hodgkin's lymphoma (HL) patients treated with radiation therapy (RT) (HL), involved field radiation therapy (IFRT) has largely replaced the extended fields. To determine the out-of-field dose delivered from a typical IFRT to surrounding critical structures, we measured the dose at various points in an anthropomorphic phantom. The phantom is divided into 1-inch-thick slices with the ability to insert TLDs at 3-cm intervals grid spacing. Two treatment fields were designed, and a total of 45 TLDs were placed (equally spaced) at the margin of the each of the 2 radiation fields. After performing a computed tomography simulation, 2 treatment plans targeting the mediastinum, a typical treatment field in patients with early stage HL, were generated. A total dose of 3060 cGy was delivered to the gross tumor volume for each field consecutively. The highest measured dose detected at 1 cm from the field edge in the planning target volume was 496 cGy, equivalent to 16% of the isocentric dose. The dose dropped significantly with increasing distance from the field edge. It ranged from 1.1-3.9% of the isocentric dose at a distance of 3.2-4 cm to <1.6% at a distance of >6 cm. Although the computer treatment planning system (CTPS) frequently underestimated the dose delivered, the difference in dose between measured and generated by CTPS was <2.5% in 90 positions measured. The collateral dose of radiation to breasts from IFRT is minimal. The out-of-field dose, although mildly underestimated by CTPS, becomes insignificant at >3 cm from the field edge of the radiation field.

  7. The relative biological effectiveness of out-of-field dose

    NASA Astrophysics Data System (ADS)

    Balderson, Michael; Koger, Brandon; Kirkby, Charles

    2016-01-01

    Purpose: using simulations and models derived from existing literature, this work investigates relative biological effectiveness (RBE) for out-of-field radiation and attempts to quantify the relative magnitudes of different contributing phenomena (spectral, bystander, and low dose hypersensitivity effects). Specific attention is paid to external beam radiotherapy treatments for prostate cancer. Materials and methods: using different biological models that account for spectral, bystander, and low dose hypersensitivity effects, the RBE was calculated for different points moving radially out from isocentre for a typical single arc VMAT prostate case. The RBE was found by taking the ratio of the equivalent dose with the physical dose. Equivalent doses were calculated by determining what physical dose would be necessary to produce the same overall biological effect as that predicted using the different biological models. Results: spectral effects changed the RBE out-of-field less than 2%, whereas response models incorporating low dose hypersensitivity and bystander effects resulted in a much more profound change of the RBE for out-of-field doses. The bystander effect had the largest RBE for points located just outside the edge of the primary radiation beam in the cranial caudal (z-direction) compared to low dose hypersensitivity and spectral effects. In the coplanar direction, bystander effect played the largest role in enhancing the RBE for points up to 8.75 cm from isocentre. Conclusions: spectral, bystander, and low dose hypersensitivity effects can all increase the RBE for out-of-field radiation doses. In most cases, bystander effects seem to play the largest role followed by low dose hypersensitivity. Spectral effects were unlikely to be of any clinical significance. Bystander, low dose hypersensitivity, and spectral effect increased the RBE much more in the cranial caudal direction (z-direction) compared with the coplanar directions.

  8. Peripheral photon and neutron doses from prostate cancer external beam irradiation.

    PubMed

    Bezak, Eva; Takam, Rundgham; Marcu, Loredana G

    2015-12-01

    Peripheral photon and neutron doses from external beam radiotherapy (EBRT) are associated with increased risk of carcinogenesis in the out-of-field organs; thus, dose estimations of secondary radiation are imperative. Peripheral photon and neutron doses from EBRT of prostate carcinoma were measured in Rando phantom. (6)LiF:Mg,Cu,P and (7)LiF:Mg,Cu,P glass-rod thermoluminescence dosemeters (TLDs) were inserted in slices of a Rando phantom followed by exposure to 80 Gy with 18-MV photon four-field 3D-CRT technique. The TLDs were calibrated using 6- and 18-MV X-ray beam. Neutron dose equivalents measured with CR-39 etch-track detectors were used to derive readout-to-neutron dose conversion factor for (6)LiF:Mg,Cu,P TLDs. Average neutron dose equivalents per 1 Gy of isocentre dose were 3.8±0.9 mSv Gy(-1) for thyroid and 7.0±5.4 mSv Gy(-1) for colon. For photons, the average dose equivalents per 1 Gy of isocentre dose were 0.2±0.1 mSv Gy(-1) for thyroid and 8.1±9.7 mSv Gy(-1) for colon. Paired (6)LiF:Mg,Cu,P and (7)LiF:Mg,Cu,P TLDs can be used to measure photon and neutron doses simultaneously. Organs in close proximity to target received larger doses from photons than those from neutrons whereas distally located organs received higher neutron versus photon dose.

  9. The influence of new medial linkage orthosis on walking and independence in spinal cord injury patients: a pilot study.

    PubMed

    Bani, Monireh Ahmadi; Arazpour, Mokhtar; Farahmand, Farzam; Mousavi, Mohammad Ebrahim; Samadian, Mohammad; Kashani, Reza Vahab; Hutchins, Stephen William

    2016-01-01

    In an effort to overcome the disadvantages of reciprocating gait orthoses (RGOs) and medial linkage orthoses (MLOs), a new design of MLO was developed. Therefore the aim of this study was comparison effect of a new reciprocating MLO and traditional isocentric RGO on gait parameters and functional independence (orthosis donning and doffing time) in spinal cord injury (SCI) subjects to provide more evidence of its efficacy. Four people with motor incomplete SCI participated in this study. Each participant was fitted with an MLO and isocentric reciprocating gait orthosis (IRGO) to enable a comparison of walking speed, cadence and endurance to be performed. There were no statistically significant differences demonstrated in temporal-spatial parameters between the orthotic walking conditions in this study, but walking with the MLO improved the stride length and speed of walking by 28.57 and 40.9% compared with walking with an IRGO as a control condition. Hip flexion occurred predominantly during single-support phases, with negligible motion during double-support phases. The first and second Subjects had hip kinematic pattern more near normal when they walked with medial linkage reciprocal gait orthosis (MLRGO) in comparison with IRGO. There was significant difference between donning and doffing in two conditions (P=0.046) but there was not significant difference between two conditions in standing and sitting although these two conditions improved by new MLO. The new MLO provided a quicker and more independent gait compared with IRGO, in addition the new MLO made it easier for subjects to get from sitting to standing and from standing to sitting.

  10. Validation and clinical implementation of commercial secondary check software with heterogeneity corrections.

    PubMed

    Kuppusamy, Vijayalakshmi; Nagarajan, Vivekanandan; Murugan, Lavanya

    2016-01-01

    To validate and implement PTW diamond secondary check software (SCS) in a routine clinical use. The secondary independent monitor unit or dose calculation verifications have led to a significant increase in the workflow associated with QA treatments. Modelling, validation and commissioning are necessary steps thereby making it a useful tool for QA. PTW Diamond SCS is capable of calculating VMAT fields, based on modified Clarkson integration, accounting for multi-leaf collimators (MLC) transmission and measured collimator scatter factors. Validation for heterogeneity corrections is made using circular phantom with inserts of various density materials. 150 VMAT plans were compared using (i) plans calculated in homogeneous cylindrical phantom and (ii) VMAT plans calculated with heterogeneity corrections using electron density values for each organ. Diamond SCS calculated dose for homogeneous cylindrical phantom resulted in average deviation of (0.1 ± 2.14%) with Eclipse TPS calculated dose and (-2.0 ± 1.66%) with absolute measured dose. PTW's OCTAVIUS-4D phantom with 729 ion chamber detector array measurements agreed well with Eclipse TPS calculated dose showing an average deviation of (-1.69 ± 1.56%). Diamond SCS dose calculations were performed with heterogeneity corrections for 124 VMAT plans with isocentre at a region above -350 HU. The overall MU variations between Diamond SCS and TPS Acuros-XB algorithms were within ±5%. Hence, the Diamond SCS can be used as an additional tool along with phantom measurements for patient specific quality assurance of VMAT plans with heterogeneity corrections having isocentre at a region above -350 HU.

  11. Clinical implementation and rapid commissioning of an EPID based in-vivo dosimetry system

    NASA Astrophysics Data System (ADS)

    Hanson, Ian M.; Hansen, Vibeke N.; Olaciregui-Ruiz, Igor; van Herk, Marcel

    2014-10-01

    Using an Electronic Portal Imaging Device (EPID) to perform in-vivo dosimetry is one of the most effective and efficient methods of verifying the safe delivery of complex radiotherapy treatments. Previous work has detailed the development of an EPID based in-vivo dosimetry system that was subsequently used to replace pre-treatment dose verification of IMRT and VMAT plans. Here we show that this system can be readily implemented on a commercial megavoltage imaging platform without modification to EPID hardware and without impacting standard imaging procedures. The accuracy and practicality of the EPID in-vivo dosimetry system was confirmed through a comparison with traditional TLD in-vivo measurements performed on five prostate patients. The commissioning time required for the EPID in-vivo dosimetry system was initially prohibitive at approximately 10 h per linac. Here we present a method of calculating linac specific EPID dosimetry correction factors that allow a single energy specific commissioning model to be applied to EPID data from multiple linacs. Using this method reduced the required per linac commissioning time to approximately 30 min. The validity of this commissioning method has been tested by analysing in-vivo dosimetry results of 1220 patients acquired on seven linacs over a period of 5 years. The average deviation between EPID based isocentre dose and expected isocentre dose for these patients was (-0.7  ±  3.2)%. EPID based in-vivo dosimetry is now the primary in-vivo dosimetry tool used at our centre and has replaced nearly all pre-treatment dose verification of IMRT treatments.

  12. Comparison of the extent of hippocampal sparing according to the tilt of a patient's head during WBRT using linear accelerator-based IMRT and VMAT.

    PubMed

    Moon, Sun Young; Yoon, Myonggeun; Chung, Mijoo; Chung, Weon Kuu; Kim, Dong Wook

    2016-05-01

    In this paper, we report the results of our investigation into whole brain radiotherapy (WBRT) using linear accelerator-based intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in lung cancer patients with a high risk of metastasis to the brain. Specifically, we assessed the absorbed dose and the rate of adverse effects for several organs at risk (OAR), including the hippocampus, according to the tilt of a patient's head. We arbitrarily selected five cases where measurements were made with the patients' heads tilted forward and five cases without such tilt. We set the entire brain as the planning target volume (PTV), and the hippocampi, the lenses, the eyes, and the cochleae as the main OAR, and formulated new plans for IMRT (coplanar, non-coplanar) and VMAT (coplanar, non-coplanar). Using the dose-volume histogram (DVH), we calculated and compared the effective uniform dose (EUD), normal tissue complication probability (NTCP) of the OAR and the mean and the maximum doses of hippocampus. As a result, if the patient tilted the head forward when receiving the Linac-based treatment, for the same treatment effect in the PTV, we confirmed that a lower dose entered the OAR, such as the hippocampus, eye, lens, and cochlea. Moreover, the damage to the hippocampus was expected to be the least when receiving coplanar VMAT with the head tilted forward. Accordingly, if patients tilt their heads forward when undergoing Linac-based WBRT, we anticipate that a smaller dose would be transmitted to the OAR, resulting in better quality of life following treatment. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  13. Ultrafast X-ray Science at the Sub-Picosecond Pulse Source

    SciTech Connect

    Gaffney, Kelly J.; /SLAC, SSRL

    2005-09-30

    The ultrafast, high brightness x-ray free electron laser (XFEL) sources of the future have the potential to revolutionize the study of time dependent phenomena in the natural sciences. These linear accelerator (linac) sources will generate femtosecond (fs) x-ray pulses with peak flux comparable to conventional lasers, and far exceeding all other x-ray sources. The Stanford Linear Accelerator Center (SLAC) has pioneered the development of linac science and technology for decades, and since 2000 SLAC and the Stanford Synchrotron Radiation Laboratory (SSRL) have focused on the development of linac based ultrafast electron and x-ray sources. This development effort has led to the creation of a new x-ray source, called the Sub-Picosecond Pulse Source (SPPS), which became operational in 2003 [1]. The SPPS represents the first step toward the world's first hard x-ray free electron laser (XFEL), the Linac Coherent Light Source (LCLS), due to begin operation at SLAC in 2009. The SPPS relies on the same linac-based acceleration and electron bunch compression schemes that will be used at the LCLS to generate ultrashort, ultrahigh peak brightness electron bunches [2]. This involves creating an energy chirp on the electron bunch during acceleration and subsequent compression of the bunch in a series of energy-dispersive magnetic chicanes to create 80 fs electron pulses. The SPPS has provided an excellent opportunity to demonstrate the viability of these electron bunch compression schemes and to pursue goals relevant to the utilization and validation of XFEL light sources.

  14. Is it sufficient to repeat LINEAR accelerator stereotactic radiosurgery in choroidal melanoma?

    PubMed

    Furdova, A; Horkovicova, K; Justusova, P; Sramka, M

    One day session LINAC based stereotactic radiosurgery (SRS) at LINAC accelerator is a method of "conservative" attitude to treat the intraocular malignant uveal melanoma. We used model Clinac 600 C/D Varian (system Aria, planning system Corvus version 6.2 verification IMRT OmniPro) with 6 MeV X by rigid immobilization of the eye to the Leibinger frame. The stereotactic treatment planning after fusion of CT and MRI was optimized according to the critical structures (lens, optic nerve, also lens and optic nerve at the contralateral side, chiasm). The first plan was compared and the best plan was applied for therapy at C LINAC accelerator. The planned therapeutic dose was 35.0 Gy by 99 % of DVH (dose volume histogram). In our clinical study in the group of 125 patients with posterior uveal melanoma treated with SRS, in 2 patients (1.6 %) was repeated SRS indicated. Patient age of the whole group ranged from 25 to 81 years with a median of 54 TD was 35.0 Gy. In 2 patients after 5 year interval after stereotactic radiosurgery for uveal melanoma stage T1, the tumor volume increased to 50 % of the primary tumor volume and repeated SRS was necessary. To find out the changes in melanoma characteristics after SRS in long term interval after irradiation is necessary to follow up the patient by an ophthalmologist regularly. One step LINAC based stereotactic radiosurgery with a single dose 35.0 Gy is one of treatment options to treat T1 to T3 stage posterior uveal melanoma and to preserve the eye globe. In some cases it is possible to repeat the SRS after more than 5 year interval (Fig. 8, Ref. 23).

  15. WE-B-19A-01: SRT II: Uncertainties in SRT

    SciTech Connect

    Dieterich, S; Schlesinger, D; Geneser, S

    2014-06-15

    SRS delivery has undergone major technical changes in the last decade, transitioning from predominantly frame-based treatment delivery to imageguided, frameless SRS. It is important for medical physicists working in SRS to understand the magnitude and sources of uncertainty involved in delivering SRS treatments for a multitude of technologies (Gamma Knife, CyberKnife, linac-based SRS and protons). Sources of SRS planning and delivery uncertainty include dose calculation, dose fusion, and intra- and inter-fraction motion. Dose calculations for small fields are particularly difficult because of the lack of electronic equilibrium and greater effect of inhomogeneities within and near the PTV. Going frameless introduces greater setup uncertainties that allows for potentially increased intra- and interfraction motion, The increased use of multiple imaging modalities to determine the tumor volume, necessitates (deformable) image and contour fusion, and the resulting uncertainties introduced in the image registration process further contribute to overall treatment planning uncertainties. Each of these uncertainties must be quantified and their impact on treatment delivery accuracy understood. If necessary, the uncertainties may then be accounted for during treatment planning either through techniques to make the uncertainty explicit, or by the appropriate addition of PTV margins. Further complicating matters, the statistics of 1-5 fraction SRS treatments differ from traditional margin recipes relying on Poisson statistics. In this session, we will discuss uncertainties introduced during each step of the SRS treatment planning and delivery process and present margin recipes to appropriately account for such uncertainties. Learning Objectives: To understand the major contributors to the total delivery uncertainty in SRS for Gamma Knife, CyberKnife, and linac-based SRS. Learn the various uncertainties introduced by image fusion, deformable image registration, and contouring

  16. Practical implications for the quality assurance of modulated radiation therapy techniques using point detector arrays.

    PubMed

    Kantz, Steffi; Troeller McDermott, Almut; Söhn, Matthias; Reinhardt, Sabine; Belka, Claus; Parodi, Katia; Reiner, Michael

    2017-08-30

    Linac parameters potentially influencing the delivery quality of IMRT and VMAT plans are investigated with respect to threshold ranges, consequently to be considered in a linac based quality assurance procedure. Three commercially available 2D arrays are used to further investigate the influence of the measurement device. Using three commercially available 2D arrays (Mx: MatriXX(evolution) , Oc: Octavius(1500) , Mc: MapCHECK2), simple static measurements, measurements for MLC characterization and dynamic interplay of gantry movement, MLC movement and variable dose rate were performed. The results were evaluated with respect to each single array as well as among each other. Simple static measurements showed different array responses to dose, dose rate and profile homogeneity and revealed instabilities in dose delivery and profile shape during linac ramp up. Using the sweeping gap test, all arrays were able to detect small leaf misalignments down to ±0.1 mm, but this test also demonstrated up to 15% dose deviation due to profile instabilities and fast accelerating leaves during linac ramp up. Tests including gantry rotation showed different stability of gantry mounts for each array. Including gantry movement and dose rate variability, differences compared to static delivery were smaller compared to dose differences when simultaneously controling interplay of gantry movement, leaf movement and dose rate variability. Linac based QA is feasible with the tested commercially available 2D arrays. Limitations of each array and the linac ramp up characteristics should be carefully considered during individual plan generation and regularly checked in linac QA. Especially the dose and dose profile during linac ramp up should be checked regularly, as well as MLC positioning accuracy using a sweeping gap test. Additionally, dynamic interplay tests including various gantry rotation speeds and angles, various leaf speeds and various dose rates should be included. © 2017 The

  17. Monolithic silicon photonics in a sub-100nm SOI CMOS microprocessor foundry: progress from devices to systems

    NASA Astrophysics Data System (ADS)

    Popović, Miloš A.; Wade, Mark T.; Orcutt, Jason S.; Shainline, Jeffrey M.; Sun, Chen; Georgas, Michael; Moss, Benjamin; Kumar, Rajesh; Alloatti, Luca; Pavanello, Fabio; Chen, Yu-Hsin; Nammari, Kareem; Notaros, Jelena; Atabaki, Amir; Leu, Jonathan; Stojanović, Vladimir; Ram, Rajeev J.

    2015-02-01

    We review recent progress of an effort led by the Stojanović (UC Berkeley), Ram (MIT) and Popović (CU Boulder) research groups to enable the design of photonic devices, and complete on-chip electro-optic systems and interfaces, directly in standard microelectronics CMOS processes in a microprocessor foundry, with no in-foundry process modifications. This approach allows tight and large-scale monolithic integration of silicon photonics with state-of-the-art (sub-100nm-node) microelectronics, here a 45nm SOI CMOS process. It enables natural scale-up to manufacturing, and rapid advances in device design due to process repeatability. The initial driver application was addressing the processor-to-memory communication energy bottleneck. Device results include 5Gbps modulators based on an interleaved junction that take advantage of the high resolution of the sub-100nm CMOS process. We demonstrate operation at 5fJ/bit with 1.5dB insertion loss and 8dB extinction ratio. We also demonstrate the first infrared detectors in a zero-change CMOS process, using absorption in transistor source/drain SiGe stressors. Subsystems described include the first monolithically integrated electronic-photonic transmitter on chip (modulator+driver) with 20-70fJ/bit wall plug energy/bit (2-3.5Gbps), to our knowledge the lowest transmitter energy demonstrated to date. We also demonstrate native-process infrared receivers at 220fJ/bit (5Gbps). These are encouraging signs for the prospects of monolithic electronics-photonics integration. Beyond processor-to-memory interconnects, our approach to photonics as a "More-than- Moore" technology inside advanced CMOS promises to enable VLSI electronic-photonic chip platforms tailored to a vast array of emerging applications, from optical and acoustic sensing, high-speed signal processing, RF and optical metrology and clocks, through to analog computation and quantum technology.

  18. Devices and systems-on-chip for photonic communication links in a microprocessor

    NASA Astrophysics Data System (ADS)

    Wade, Mark T.

    For the first time, high-performance photonic devices and electronic-photonic systems-on-chip are monolithically integrated in an advanced CMOS microelectronics fabrication process. This includes a silicon optical resonator termed the "spoked-ring" cavity that meets the constraints of thin-SOI microelectronics CMOS processes and enables energy efficient modulators and thermally tunable filters. For low-loss fiber-to-chip optical coupling, a phased-array antenna concept is demonstrated, and the 45 nm CMOS microelectronics process is shown to support a near ideal implementation of the device using the crystalline silicon and polysilicon material layers that comprise the active region and gate, respectively, of the native MOSFET transistors. The active devices and vertical grating couplers are implemented in large-scale electronic-photonic systems-on-chip to demonstrate a wavelength stabilized, microring-based chip-to-chip communications link and an 11-channel wavelength division multiplexed (WDM) transmitter. The link is shown to be robust against thermal environmental variations which is critical for operation in realistic systems. The chip-to-chip link is then used to demonstrate a CPU-to-memory communication link, the first demonstration of its kind. The first microprocessor with photonic I/O is demonstrated as part of this work, with substantial implications for computer architecture. Advanced photonic device technology demonstrations, including photonic crystals, a quantum-correlated photon-pair source, an active photonic device platform in a 32 nm SOI node, and a 180 nm bulk silicon process, are presented to show the wide range of applications that monolithic integration could support in the future of photonics. These results taken together show that monolithic integration directly into CMOS microelectronics processes does allow high performance photonics, and is a viable approach to build large-scale electronic-photonic systems with a realistic path to

  19. Chemical vapor deposition of thin crystals of layered semiconductor SnS2 for fast photodetection application.

    PubMed

    Su, Guoxiong; Hadjiev, Viktor G; Loya, Phillip E; Zhang, Jing; Lei, Sidong; Maharjan, Surendra; Dong, Pei; M Ajayan, Pulickel; Lou, Jun; Peng, Haibing

    2015-01-14

    Layered two-dimensional (2D) semiconductors, such as MoS(2) and SnS(2), have been receiving intensive attention due to their technological importance for the next-generation electronic/photonic applications. We report a novel approach to the controlled synthesis of thin crystal arrays of SnS(2) at predefined locations on chip by chemical vapor deposition with seed engineering and have demonstrated their application as fast photodetectors with photocurrent response time ∼ 5 μs. This opens a pathway for the large-scale production of layered 2D semiconductor devices, important for applications in integrated nanoelectronic/photonic systems.

  20. Single photon delayed feedback: a way to stabilize intrinsic quantum cavity electrodynamics.

    PubMed

    Carmele, Alexander; Kabuss, Julia; Schulze, Franz; Reitzenstein, Stephan; Knorr, Andreas

    2013-01-04

    We propose a scheme to control cavity quantum electrodynamics in the single photon limit by delayed feedback. In our approach a single emitter-cavity system, operating in the weak coupling limit, can be driven into the strong coupling-type regime by an external mirror: The external loop produces Rabi oscillations directly connected to the electron-photon coupling strength. As an expansion of typical cavity quantum electrodynamics, we treat the quantum correlation of external and internal light modes dynamically and demonstrate a possible way to implement a fully quantum mechanical time-delayed feedback. Our theoretical approach proposes a way to experimentally feedback control quantum correlations in the single photon limit.

  1. Two-electron photoionization of ground-state lithium

    SciTech Connect

    Kheifets, A. S.; Fursa, D. V.; Bray, I.

    2009-12-15

    We apply the convergent close-coupling (CCC) formalism to single-photon two-electron ionization of the lithium atom in its ground state. We treat this reaction as single-electron photon absorption followed by inelastic scattering of the photoelectron on a heliumlike Li{sup +} ion. The latter scattering process can be described accurately within the CCC formalism. We obtain integrated cross sections of single photoionization leading to the ground and various excited states of the Li{sup +} ion as well as double photoionization extending continuously from the threshold to the asymptotic limit of infinite photon energy. Comparison with available experimental and theoretical data validates the CCC model.

  2. π 0 and η Photoproduction on the Deuteron at ELPH, Tohoku University

    NASA Astrophysics Data System (ADS)

    Ishikawa, T.; Fujimura, H.; Fukasawa, H.; Hashimoto, R.; He, Q.; Honda, Y.; Iwata, T.; Kaida, S.; Kasagi, J.; Kawano, A.; Kuwasaki, S.; Maeda, K.; Masumoto, S.; Miyabe, M.; Miyahara, F.; Mochizuki, K.; Muramatsu, N.; Nakamura, A.; Nawa, K.; Ogushi, S.; Okada, Y.; Onodera, Y.; Ozawa, K.; Sakamoto, Y.; Sato, M.; Shimizu, H.; Sugai, H.; Suzuki, K.; Tajima, Y.; Takahashi, S.; Taniguchi, Y.; Tsuchikawa, Y.; Yamazaki, H.; Yamazaki, R.; Yoshida, H. Y.

    2013-08-01

    Baryon spectroscopy is important to understand Quantum Chromodynamics at low energies. In this purpose, a series of π 0 and η photoproduction experiments was carried out with an electro-magnetic calorimeter FOREST at Research Center for Electron Photon Science, Tohoku University. The incident tagged bremsstrahlung photon energy ranges from 550 to 1,150 MeV. The differential and total cross sections obtained for π 0 and η photoproduction processes on the proton are consistent with the SAID and MAID calculations. The analysis of π 0 and η photoproduction on the neutron is underway.

  3. Experimental Search for a Heavy Electron

    DOE R&D Accomplishments Database

    Boley, C. D.; Elias, J. E.; Friedman, J. I.; Hartmann, G. C.; Kendall, H. W.; Kirk, P.N.; Sogard, M. R.; Van Speybroeck, L. P.; de Pagter, J. K.

    1967-09-01

    A search for a heavy electron of the type considered by Low and Blackmon has been made by studying the inelastic scattering of 5 BeV electrons from hydrogen. The search was made over a range of values of the mass of the heavy electron from 100 t0 1300 MeV. No evidence for such a particle was observed. Upper limits on the production cross sections were determined and employed to deducelimits on the values of the electron-photon-heavy electron coupling constant in Low and Blackmon=s theory.

  4. First-principles electron dynamics control simulation of diamond under femtosecond laser pulse train irradiation.

    PubMed

    Wang, Cong; Jiang, Lan; Wang, Feng; Li, Xin; Yuan, Yanping; Xiao, Hai; Tsai, Hai-Lung; Lu, Yongfeng

    2012-07-11

    A real-time and real-space time-dependent density functional is applied to simulate the nonlinear electron-photon interactions during shaped femtosecond laser pulse train ablation of diamond. Effects of the key pulse train parameters such as the pulse separation, spatial/temporal pulse energy distribution and pulse number per train on the electron excitation and energy absorption are discussed. The calculations show that photon-electron interactions and transient localized electron dynamics can be controlled including photon absorption, electron excitation, electron density, and free electron distribution by the ultrafast laser pulse train.

  5. STAR Upgrade Plan for the Coming Decade

    NASA Astrophysics Data System (ADS)

    Huang, Huan Zhong

    2013-05-01

    The STAR Collaboration will complete the Heavy Flavor Tracker (HFT) and the Muon Telescope Detector (MTD) upgrades by 2014. STAR has also embarked on an upgrade plan to extend the capabilities for measuring jets, electron/photon and leading particles in the forward rapidity region in the coming decade. Planned detector upgrades include tracking detectors for charged particles, electro-magnetic and hadronic calorimeters and particle identification detector in the forward direction. We will present physics motivations, status of detector R&D and design considerations for the forward measurements focusing on p + p/p + A and polarized p + p collisions.

  6. η n Scattering Length from the γ d to pη n Reaction at Eγ ˜ 0.9 GeV

    NASA Astrophysics Data System (ADS)

    Ishikawa, Takatsugu; Fujioka, Hiroyuki; Honda, Yuki; Hotta, Tomoaki; Inoue, Yosuke; Itahashi, Kenta; Kanda, Hiroki; Kawai, Hideyuki; Maeda, Kazushige; Miyabe, Manabu; Miyata, Seiya; Matsumura, Yuji; Muramatsu, Norihito; Ohnishi, Hiroaki; Ozawa, Kyoichiro; Sasagawa, Mizuki; Shimizu, Hajime; Shiraishi, Ken'ichiro; Tabata, Makoto; Tokiyasu, Atsushi O.; Tsuchikawa, Yusuke

    We plan to conduct a new experiment for the γ d to pη n reaction using the FOREST detector at the Research Center for Electron Photon Science, Tohoku University, Japan. The main objective is to determine the low-energy η -neutron scattering parameters. The photon beam with energies around 930 MeV can give the recoilless condition of η mesons by detecting the protons at 0°. The effects of the the η -neutron final-state interaction must be enhanced due to the small relative momentum between an η meson and a residual neutron. In this contribution, the planned FOREST experiment is presented.

  7. Experiment Pamir-3. Coplanar emission of high energy gamma-quanta at interaction of hadrons with nuclei of air atoms at energies above 10 to the 7th power GeV

    NASA Technical Reports Server (NTRS)

    Asatiani, T. L.; Genina, L. E.; Zatsepin, G. T.

    1985-01-01

    A systematic analysis of large gamma families, detected in X-ray emulsion chambers, cases of multicore halos have been observed, and among them five events in which the halo is divided into three of four separate cores with their alignment observed in the target diagram (coplanarity of axes of corresponding electron photon cascades). The halo alignment (tendency to the straight line) leads to the aximuthal asymmetry (thrust). The analysis of lateral and momentum distributions of particles in these families shows that they also have thrust that correlates with the direction of the halo core alignment.

  8. EAS High Energy Muon Component around the Knee: Simultaneous Surface and Underground Measurements at Baksan

    NASA Astrophysics Data System (ADS)

    Borisovich Petkov, V.; Boliev, M.M.; Karpov, S.N.; Radchenkov, A.V.; Volchenko, V.I.; Yanin, A.F.; A.N.; Zaichenko, A.N.

    2003-07-01

    A complex of installations of the Baksan Neutrino Observatory INR RAS consisting of Baksan Underground Scintillation telescope (BUST) and shower array "Andyrchy" located above the first measure simultaneously high energy muon (Eµ ≥ 230 GeV) and electron-photon components of EAS. Shower size spectrum has been measured in the range 7 · 105 - 2 · 107 and the knee is found to be at Ne = 1.8 · 106 . The dependence of the average number of high energy muons in EAS on Ne points out a heavier composition after the knee.

  9. Diamonds for beam instrumentation

    SciTech Connect

    Griesmayer, Erich

    2013-04-19

    Diamond is perhaps the most versatile, efficient and radiation tolerant material available for use in beam detectors with a correspondingly wide range of applications in beam instrumentation. Numerous practical applications have demonstrated and exploited the sensitivity of diamond to charged particles, photons and neutrons. In this paper, a brief description of a generic diamond detector is given and the interaction of the CVD diamond detector material with protons, electrons, photons and neutrons is presented. Latest results of the interaction of sCVD diamond with 14 MeV mono-energetic neutrons are shown.

  10. Nanowire formation is preceded by nanotube growth in templated electrodeposition of cobalt hybrid nanostructures

    NASA Astrophysics Data System (ADS)

    Dryden, Daniel M.; Vidu, Ruxandra; Stroeve, Pieter

    2016-11-01

    Cobalt fluted nanowires, novel nanostructures with a diameter of 200 nm consisting of a solid nanowire base and a thin, nanotubular flute shape, were grown in track-etched polycarbonate membranes via templated electrodeposition. The structures were characterized electrochemically via cyclic voltammetry, chronoamperometry, and charge stripping, and structurally via scanning electron microscopy, transmission electron microscopy, and focused ion beam cross-sectioning. Electrochemical and structural analysis reveals details of their deposition kinetics, structure, and morphology, and indicate possible mechanisms for their formation and control. These unique structures provide inspiration for an array of possible applications in electronics, photonics, and other fields.

  11. ITS Version 3.0: Powerful, user-friendly software for radiation modelling

    SciTech Connect

    Kensek, R.P.; Halbleib, J.A.; Valdez, G.D.

    1993-12-31

    ITS (the Integrated Tiger Series) is a powerful, but user-friendly, software package permitting state-of-the-art modelling of electron and/or photon radiation effects. The programs provide Monte Carlo solution of linear time-independent coupled electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields. The ITS system combines operational simplicity and physical accuracy in order to provide experimentalist and theorists alike with a method for the routine but rigorous solution of sophisticated radiation transport problems.

  12. Application Of Cathode-Ray Tube Technology To The Clinical Evaluation Of Visual Functions

    NASA Astrophysics Data System (ADS)

    Vernier, Francoise; Charlier, Jacques; Nguyen, Duc D.

    1988-02-01

    Cathode-ray tubes (CRTs) have many applications in the clinical evaluation of visual functions. They have been used to test visual acuity, contrast sensitivity, visual fields, and early development of vision in preverbal children. Because CRTs provide considerable flexibility for the definition of spatial and temporal components of the stimulus, their use provides an attractive solution to many visual stimulation problems. However, there are some limitations due to the scanning of the picture frame by the electron beam and also to the electron-photon conversion process. The spatial, photometric, spectral, and temporal characteristics of a specifically designed monochromatic television system are evaluated with reference to the physiological requirements of visual tests.

  13. Ultrafast and nanoscale diodes

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Lau, Y. Y.

    2016-10-01

    Charge carrier transport across interfaces of dissimilar materials (including vacuum) is the essence of all electronic devices. Ultrafast charge transport across a nanometre length scale is of fundamental importance in the miniaturization of vacuum and plasma electronics. With the combination of recent advances in electronics, photonics and nanotechnology, these miniature devices may integrate with solid-state platforms, achieving superior performance. This paper reviews recent modelling efforts on quantum tunnelling, ultrafast electron emission and transport, and electrical contact resistance. Unsolved problems and challenges in these areas are addressed.

  14. Efficient Surface Enhanced Raman Scattering substrates from femtosecond laser based fabrication

    NASA Astrophysics Data System (ADS)

    Parmar, Vinod; Kanaujia, Pawan K.; Bommali, Ravi Kumar; Vijaya Prakash, G.

    2017-10-01

    A fast and simple femtosecond laser based methodology for efficient Surface Enhanced Raman Scattering (SERS) substrate fabrication has been proposed. Both nano scaffold silicon (black silicon) and gold nanoparticles (Au-NP) are fabricated by femtosecond laser based technique for mass production. Nano rough silicon scaffold enables large electromagnetic fields for the localized surface plasmons from decorated metallic nanoparticles. Thus giant enhancement (approximately in the order of 104) of Raman signal arises from the mixed effects of electron-photon-phonon coupling, even at nanomolar concentrations of test organic species (Rhodamine 6G). Proposed process demonstrates the low-cost and label-less application ability from these large-area SERS substrates.

  15. Silicon PIN diode based electron-gamma coincidence detector system for Noble Gases monitoring.

    PubMed

    Khrustalev, K; Popov, V Yu; Popov, Yu S

    2017-08-01

    We present a new second generation SiPIN based electron-photon coincidence detector system developed by Lares Ltd. for use in the Noble Gas measurement systems of the International Monitoring System and the On-site Inspection verification regimes of the Comprehensive Nuclear-Test Ban Treaty (CTBT). The SiPIN provide superior energy resolution for electrons. Our work describes the improvements made in the second generation detector cells and the potential use of such detector systems for other applications such as In-Situ Kr-85 measurements for non-proliferation purposes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. A step toward next-generation nanoimprint lithography: extending productivity and applicability

    NASA Astrophysics Data System (ADS)

    Ok, Jong G.; Shin, Young Jae; Park, Hui Joon; Guo, L. Jay

    2015-11-01

    Because of its unique principle based on mechanical deformation, nanoimprint lithography (NIL) has been playing an important role for nanopatterning and nanofabrication beyond the limit of conventional optical lithography. Many diverse fields involving electronics, photonics, and energy engineering have all shown significant increase in utilization of nanopattern structures, particularly in large areas and at submicron scales. To meet this demand, expanding the realm of NIL toward more scalable and versatile patterning technology is in high demand. In this feature article, we give an overview of how NIL can extend productivity and applicability by addressing three key issues: continuous NIL for more scalable nanopatterning, large-area mold fabrications, and novel resist engineering.

  17. Report from the ZEUS Collaboration at HERA

    SciTech Connect

    Abramowicz, H.

    1994-12-01

    This is a short overview of the results obtained by the ZEUS Collaboration with data collected during HERA`s first year and corresponding to an integrated luminosity of 25 nb{sup {minus}1}. Included are the measurement of the total, partial, and {rho} photoproduction cross sections, a study of high mass diffractive photoproduction, new results from hard photoproduction where a clear signal of a direct photon contribution has been established, the measurement of the photon structure function F{sub 2}, and first results on diffractive dissociation of the virtual photon in the deep inelastic electron photon scattering. Limits on leptoquarks and excited electrons are also presented.

  18. Surface state photoelectrons in topological insulators: Green's function approach.

    PubMed

    Schmeltzer, D; Saxena, A

    2015-12-09

    We compute the photoemission intensity and polarization for the surface states in topological insulators. Due to the chirality and linear energy dispersion the effective electron-photon coupling is normalized by the tunneling amplitude (τ) into the vacuum. We investigate a chiral Dirac Hamiltonian for different cases: helical, Zeeman and warping, allowing us to study spin textures. Using the Green's function formalism we obtain exact results for the emitted photoelectrons to second order in the laser field. The number of emitted photoelectrons is sensitive to the laser coherent state intensity whereas the photoelectron polarization is sensitive to the surface topology of electronic states and incoming photon polarization.

  19. Many particle spectroscopy of atoms, molecules, clusters and surfaces: international conference MPS-2016

    NASA Astrophysics Data System (ADS)

    Grum-Grzhimailo, Alexei N.; Popov, Yuri V.; Gryzlova, Elena V.; Solov'yov, Andrey V.

    2017-07-01

    The conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces (MPS-2016) brought together near to a hundred scientists in the field of electronic, photonic, atomic and molecular collisions, and spectroscopy from around the world. We deliver an Editorial of a topical issue presenting original research results from some of the participants on both experimental and theoretical studies involving many particle spectroscopy of atoms, molecules, clusters and surfaces. Contribution to the Topical Issue "Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces", edited by A.N. Grum-Grzhimailo, E.V. Gryzlova, Yu.V. Popov, and A.V. Solov'yov.

  20. Project objectives and progress at the Research Laboratory of Electronics

    SciTech Connect

    Allen, J.

    1983-01-01

    Molecule microscopy, semiconductor surface studies, atomic resonance and scattering, reaction dynamics at semiconductor surfaces, X-ray diffuse scattering, phase transitions in chemisorbed systems, optics and quantum electronics, photonics, optical spectroscopy of disordered materials and X-ray scattering from surfaces, infrared nonlinear optics, quantum optics and electronics, microwave and millimeter wave techniques, microwave and quantum magnetics, radio astronomy, electromagnetic wave theory and remote sensing, electronic properties of amorphous silicon dioxide, photon correlation spectroscopy and applications, submicron structures fabrication, plasma dynamics, optical propagation and communication, digital signal processing, speech communication, linguistics, cognitive information processing, custom integrated circuits, communications biophysics, and physiology, are discussed.

  1. Testing technology

    SciTech Connect

    Not Available

    1993-10-01

    This bulletin from Sandia National Laboratories presents current research highlights in testing technology. Ion microscopy offers new nondestructive testing technique that detects high resolution invisible defects. An inexpensive thin-film gauge checks detonators on centrifuge. Laser trackers ride the range and track helicopters at low-level flights that could not be detected by radar. Radiation transport software predicts electron/photon effects via cascade simulation. Acoustic research in noise abatement will lead to quieter travelling for Bay Area Rapid Transport (BART) commuters.

  2. Kohn-Sham approach to quantum electrodynamical density-functional theory: Exact time-dependent effective potentials in real space.

    PubMed

    Flick, Johannes; Ruggenthaler, Michael; Appel, Heiko; Rubio, Angel

    2015-12-15

    The density-functional approach to quantum electrodynamics extends traditional density-functional theory and opens the possibility to describe electron-photon interactions in terms of effective Kohn-Sham potentials. In this work, we numerically construct the exact electron-photon Kohn-Sham potentials for a prototype system that consists of a trapped electron coupled to a quantized electromagnetic mode in an optical high-Q cavity. Although the effective current that acts on the photons is known explicitly, the exact effective potential that describes the forces exerted by the photons on the electrons is obtained from a fixed-point inversion scheme. This procedure allows us to uncover important beyond-mean-field features of the effective potential that mark the breakdown of classical light-matter interactions. We observe peak and step structures in the effective potentials, which can be attributed solely to the quantum nature of light; i.e., they are real-space signatures of the photons. Our findings show how the ubiquitous dipole interaction with a classical electromagnetic field has to be modified in real space to take the quantum nature of the electromagnetic field fully into account.

  3. Gauge-invariant dynamical quantities of QED with decomposed gauge potentials

    SciTech Connect

    Zhou Baohua; Huang Yongchang

    2011-09-15

    We discover an inner structure of the QED system; i.e., by decomposing the gauge potential into two orthogonal components, we obtain a new expansion of the Lagrangian for the electron-photon system, from which, we realize the orthogonal decomposition of the canonical momentum conjugate to the gauge potential with the canonical momentum's two components conjugate to the gauge potential's two components, respectively. Using the new expansion of Lagrangian and by the general method of field theory, we naturally derive the gauge invariant separation of the angular momentum of the electron-photon system from Noether theorem, which is the rational one and has the simplest form in mathematics, compared with the other four versions of the angular momentum separation available in literature. We show that it is only the longitudinal component of the gauge potential that is contained in the orbital angular momentum of the electron, as Chen et al. have said. A similar gauge invariant separation of the momentum is given. The decomposed canonical Hamiltonian is derived, from which we construct the gauge invariant energy operator of the electron moving in the external field generated by a proton [Phys. Rev. A 82, 012107 (2010)], where we show that the form of the kinetic energy containing the longitudinal part of the gauge potential is due to the intrinsic requirement of the gauge invariance. Our method provides a new perspective to look on the nucleon spin crisis and indicates that this problem can be solved strictly and systematically.

  4. Thermal entanglement between π-electrons in silicene and photons; occurrence of phase transitions

    NASA Astrophysics Data System (ADS)

    Rastgoo, S.; Golshan, M. M.

    2017-03-01

    In this article, the thermal entanglement between π-electronic states in a monolayer silicene sheet and a single mode quantized electromagnetic field is investigated. We assume that the system is in thermal equilibrium with the environment at a temperature T, so that the whole system is described by the Boltzmann distribution. Using the states of total Hamiltonian, the thermal density matrix and, consequently, its partially transposed one is computed, giving rise to the determination of negativity. Our analytical calculations, along with representative figures, show that the system is separable at zero temperature, exhibits a maximum, at a specific temperature, and asymptotically vanishes. Along these lines we also report the effects of electron-photon coupling, as well as the silicene buckling, on the entanglement. Specifically, we demonstrate that the maximal value of entanglement is larger for stronger electron-photon coupling, while it decreases for larger buckling effect. Moreover, we show that the gap in the total energy spectrum remains intact for any value of the buckling parameter. There is, however, one state whose energy changes sign, at a specific buckling, indicating a change of phase.

  5. Benchmark study of TRIPOLI-4 through experiment and MCNP codes

    SciTech Connect

    Michel, M.; Coulon, R.; Normand, S.; Huot, N.; Petit, O.

    2011-07-01

    Reliability on simulation results is essential in nuclear physics. Although MCNP5 and MCNPX are the world widely used 3D Monte Carlo radiation transport codes, alternative Monte Carlo simulation tools exist to simulate neutral and charged particles' interactions with matter. Therefore, benchmark are required in order to validate these simulation codes. For instance, TRIPOLI-4.7, developed at the French Alternative Energies and Atomic Energy Commission for neutron and photon transport, now also provides the user with a full feature electron-photon electromagnetic shower. Whereas the reliability of TRIPOLI-4.7 for neutron and photon transport has been validated yet, the new development regarding electron-photon matter interaction needs additional validation benchmarks. We will thus demonstrate how accurately TRIPOLI-4's 'deposited spectrum' tally can simulate gamma spectrometry problems, compared to MCNP's 'F8' tally. The experimental setup is based on an HPGe detector measuring the decay spectrum of an {sup 152}Eu source. These results are then compared with those given by MCNPX 2.6d and TRIPOLI-4 codes. This paper deals with both the experimental aspect and simulation. We will demonstrate that TRIPOLI-4 is a potential alternative to both MCNPX and MCNP5 for gamma-electron interaction simulation. (authors)

  6. Correlated Light-Matter Interactions in Cavity QED

    NASA Astrophysics Data System (ADS)

    Flick, Johannes; Pellegrini, Camilla; Ruggenthaler, Michael; Appel, Heiko; Tokatly, Ilya; Rubio, Angel

    2015-03-01

    In the last decade, time-dependent density functional theory (TDDFT) has been successfully applied to a large variety of problems, such as calculations of absorption spectra, excitation energies, or dynamics in strong laser fields. Recently, we have generalized TDDFT to also describe electron-photon systems (QED-TDDFT). Here, matter and light are treated on an equal quantized footing. In this work, we present the first numerical calculations in the framework of QED-TDDFT. We show exact solutions for fully quantized prototype systems consisting of atoms or molecules placed in optical high-Q cavities and coupled to quantized electromagnetic modes. We focus on the electron-photon exchange-correlation (xc) contribution by calculating exact Kohn-Sham potentials using fixed-point inversions and present the performance of the first approximated xc-potential based on an optimized effective potential (OEP) approach. Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, and Fritz-Haber-Institut der MPG, Berlin

  7. Study of intersubband transitions in GaN-ZnGeN2 coupled quantum wells

    NASA Astrophysics Data System (ADS)

    Han, Lu; Lieberman, Colin; Zhao, Hongping

    2017-03-01

    In this work, we design and analyze a closely lattice-matched wide bandgap GaN-ZnGeN2 coupled quantum well (QW) structure targeting for near-infrared (IR) (λ ≤ 3 um) intersubband transition for quantum cascade laser applications. The coupled quantum well structure comprised two GaN wells separated by a thin ZnGeN2 barrier layer. The QW active region is surrounded by thick ZnGeN2 layers as barriers. The computations of the electron-phonon and electron-photon scattering rates are carried out by employing the Fermi's golden rule for transitions. The calculation takes into consideration the conservation of energy and momentum in scattering processes. The coupled QW structure is optimized through tuning the confined subband energy levels in the conduction band to achieve (1) electron-LO phonon resonant scattering when the energy separation between the first and second conduction subband levels matches the phonon energy of GaN (92 meV); and (2) dominant electron-photon transition in near-IR between the third and second conduction subband levels.

  8. A deterministic electrons and protons transport suite for the study of the Jovian system

    NASA Astrophysics Data System (ADS)

    Badavi, Francis; Nealy, John; Norman, Ryan

    Langley Research Center (LaRC) developed deterministic suite of transport codes for describing the transport of electrons, photons and protons in condensed media is used to simulate the effects and exposures from spectral distributions typical of electrons and protons trapped in planetary magnetic fields. The suite is made of a coupled electrons/ photons deterministic transport procedure (CEPTRN) and a light/heavy ions deterministic transport procedure (HZETRN). The primary purpose for the development of the transport suite is to provide a means for rapidly forming numerous repetitive calculations essential for electrons/protons radiation exposure assessments of complex space structures. Several favorable comparisons have been made with statistically oriented Monte Carlo calculations for typical space environment spectra which have indicated that the transport accuracy has not been compromised at the expense of computational speed. For this presentation the radiation environments of the Galilean satellites Io, Europa, Ganymede and Callisto are used as representative boundary conditions to show the capabilities of the transport suite. The Jovian radiation environment is simulated using the Jet Propulsion Lab. (JPL) GIRE model of 2003. For a limited number of candidate shielding materials, the GIRE produced electrons/protons environments are used as boundary condition to the CEPTRN and HZETRN transport suite to evaluate the particle flux and dose due to electrons and protons at various distances from the planet as a function of latitude, longitude, and altitude.

  9. Laser-Induced Linear-Field Particle Acceleration in Free Space

    DOE PAGES

    Wong, Liang Jie; Hong, Kyung -Han; Carbajo, Sergio; ...

    2017-09-11

    Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computationalmore » experiment. The formalism includes exact treatment of Maxwell’s equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the feld amplitude. For example, 30keV electrons (2.5% energy spread) are accelerated to 61MeV (0.5% spread) and to 205MeV (0.25% spread) using 250 mJ and 2.5J lasers respectively. Furthermore, these findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.« less

  10. Laser-Induced Linear-Field Particle Acceleration in Free Space.

    PubMed

    Wong, Liang Jie; Hong, Kyung-Han; Carbajo, Sergio; Fallahi, Arya; Piot, Philippe; Soljačić, Marin; Joannopoulos, John D; Kärtner, Franz X; Kaminer, Ido

    2017-09-11

    Linear-field particle acceleration in free space (which is distinct from geometries like the linac that requires components in the vicinity of the particle) has been studied for over 20 years, and its ability to eventually produce high-quality, high energy multi-particle bunches has remained a subject of great interest. Arguments can certainly be made that linear-field particle acceleration in free space is very doubtful given that first-order electron-photon interactions are forbidden in free space. Nevertheless, we chose to develop an accurate and truly predictive theoretical formalism to explore this remote possibility when intense, few-cycle electromagnetic pulses are used in a computational experiment. The formalism includes exact treatment of Maxwell's equations and exact treatment of the interaction among the multiple individual particles at near and far field. Several surprising results emerge. We find that electrons interacting with intense laser pulses in free space are capable of gaining substantial amounts of energy that scale linearly with the field amplitude. For example, 30 keV electrons (2.5% energy spread) are accelerated to 61 MeV (0.5% spread) and to 205 MeV (0.25% spread) using 250 mJ and 2.5 J lasers respectively. These findings carry important implications for our understanding of ultrafast electron-photon interactions in strong fields.

  11. Charge separation and photovoltaic conversion in polymer composites with internal donor/acceptor heterojunctions

    SciTech Connect

    Yu, G.; Heeger, A.J.

    1995-10-01

    The photosensitivity of semiconducting polymers can be enhanced by blending donor and acceptor polymers to optimize photoinduced charge separation. We describe a novel phase-separated polymer blend (composite) made with poly[2-methoxy-5-(2{prime}-ethyl-hexyloxy)-1,4-phenylene vinylene], MEH-PPV, as donor and cyano-PPV, CN-PPV, as acceptor. The photoluminescence and electroluminescence of both component polymers are quenched in the blend, indicative of rapid and efficient separation of photogenerated electron-hole pairs with electrons on the acceptor and holes on the donor. Diodes made with such a composite semiconducting polymer as the photosensitive medium show promising photovoltaic characteristics with carrier collection efficiency of 5% electrons/photon and energy conversion efficiency of 0.9%, {similar_to}20 times larger than in diodes made with pure MEH-PPV and {similar_to}100 times larger than in diodes made with CN-PPV. The photosensitivity and the quantum yield increase with reverse bias voltage, to 0.3 A/W and 80% electrons/photon respectively at {minus}10 V, comparable to results obtained from photodiodes made with inorganic semiconductors. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  12. Quantum state transfer between valley and photon qubits

    NASA Astrophysics Data System (ADS)

    Yang, Ming-Jay; Peng, Han-Ying; Na, Neil; Wu, Yu-Shu

    2017-02-01

    The electron-photon interaction in two-dimensional materials obeys the rule of "electron valley-photon polarization" correspondence. At the quantum level, such correspondence can be utilized to entangle valleys and polarizations and attain the transfer of quantum states (or information) between valley and photon qubits. Our paper presents a theoretical study of the interaction between the two types of qubits and the resultant quantum state transfer. A generic setup is introduced, which involves optical cavities enhancing the electron-photon interaction as well as facilitating both the entanglement and unentanglement between valleys and polarizations required by the transfer. The quantum system considered consists of electrons, optically excited trions, and cavity photons, with photons moving in and out of the system. A wave equation based analysis is performed, and analytical expressions are derived for the two important figures of merits that characterize the transfer, namely, yield and fidelity, allowing for the investigation of their dependences on various qubit and cavity parameters. A numerical study of the yield and fidelity has also been carried out. Overall, this paper shows promising characteristics in the valley-photon state transfer, with the conclusion that the valley-polarization correspondence can be exploited to achieve the transfer with good yield and high fidelity.

  13. Characterization of 2 MeV, 4 MeV, 6 MeV and 18 MeV buildup caps for use with a 0.6 cubic centimeter thimble ionization chamber

    SciTech Connect

    Salyer, R.L.; VanDenburg, J.W.; Prinja, A.K.; Kirby, T.; Busch, R.; Hong-Nian Jow

    1996-07-01

    The purpose of this research is to characterize existing 2 MeV, 4 MeV and 6 MeV buildup caps, and to determine if a buildup cap can be made for the 0.6 cm{sup 3} thimble ionization chamber that will accurately measure exposures in a high-energy photon radiation field. Two different radiation transport codes were used to computationally characterize existing 2 MeV, 4 MeV, and 6 MeV buildup caps for a 0.6 cm{sup 3} active volume thimble ionization chamber: ITS, The Integrated TIGER Series of Coupled Electron-Photon Monte Carlo Transport Codes; and CEPXS/ONEDANT, A One-Dimensional Coupled Electron-Photon Discrete Ordinates Code Package. These codes were also used to determine the design characteristics of a buildup cap for use in the 18 MeV photon beam produced by the 14 TW pulsed power HERMES-III electron accelerator. The maximum range of the secondary electron, the depth at which maximum dose occurs, and the point where dose and collision kerma are equal have been determined to establish the validity of electronic equilibrium. The ionization chamber with the appropriate buildup cap was then subjected to a 4 MeV and a 6 MeV bremmstrahlung radiation spectrum to determine the detector response.

  14. Geometrical accuracy of the Novalis stereotactic radiosurgery system for trigeminal neuralgia.

    PubMed

    Rahimian, Javad; Chen, Joseph C; Rao, Ajay A; Girvigian, Michael R; Miller, Michael J; Greathouse, Hugh E

    2004-11-01

    Stringent geometrical accuracy and precision are required in the stereotactic radiosurgical treatment of patients. Accurate targeting is especially important when treating a patient in a single fraction of a very high radiation dose (90 Gy) to a small target such as that used in the treatment of trigeminal neuralgia (3 to 4-mm diameter). The purpose of this study was to determine the inaccuracies in each step of the procedure including imaging, fusion, treatment planning, and finally the treatment. The authors implemented a detailed quality-assurance program. Overall geometrical accuracy of the Novalis stereotactic system was evaluated using a Radionics Geometric Phantom Chamber. The phantom has several magnetic resonance (MR) and computerized tomography (CT) imaging-friendly objects of various shapes and sizes. Axial 1-mm-thick MR and CT images of the phantom were acquired using a T1-weighted three-dimensional spoiled gradient recalled pulse sequence and the CT scanning protocols used clinically in patients. The absolute errors due to MR image distortion, CT scan resolution, and the image fusion inaccuracies were measured knowing the exact physical dimensions of the objects in the phantom. The isocentric accuracy of the Novalis gantry and the patient support system was measured using the Winston-Lutz test. Because inaccuracies are cumulative, to calculate the system's overall spatial accuracy, the root mean square (RMS) of all the errors was calculated. To validate the accuracy of the technique, a 1.5-mm-diameter spherical marker taped on top of a radiochromic film was fixed parallel to the x-z plane of the stereotactic coordinate system inside the phantom. The marker was defined as a target on the CT images, and seven noncoplanar circular arcs were used to treat the target on the film. The calculated system RMS value was then correlated with the position of the target and the highest density on the radiochromic film. The mean spatial errors due to image fusion

  15. Quantitative evaluation of patient setup uncertainty of stereotactic radiotherapy with the frameless 6D ExacTrac system using statistical modeling.

    PubMed

    Keeling, Vance; Hossain, Sabbir; Jin, Hosang; Algan, Ozer; Ahmad, Salahuddin; Ali, Imad

    2016-05-08

    The purpose of this study is to evaluate patient setup accuracy and quantify indi-vidual and cumulative positioning uncertainties associated with different hardware and software components of the stereotactic radiotherapy (SRS/SRT) with the frameless 6D ExacTrac system. A statistical model is used to evaluate positioning uncertainties of the different components of SRS/SRT treatment with the Brainlab 6D ExacTrac system using the positioning shifts of 35 patients having cranial lesions. All these patients are immobilized with rigid head-and-neck masks, simu-lated with Brainlab localizer and planned with iPlan treatment planning system. Stereoscopic X-ray images (XC) are acquired and registered to corresponding digitally reconstructed radiographs using bony-anatomy matching to calculate 6D translational and rotational shifts. When the shifts are within tolerance (0.7 mm and 1°), treatment is initiated. Otherwise corrections are applied and additional X-rays (XV) are acquired to verify that patient position is within tolerance. The uncertain-ties from the mask, localizer, IR -frame, X-ray imaging, MV, and kV isocentricity are quantified individually. Mask uncertainty (translational: lateral, longitudinal, vertical; rotational: pitch, roll, yaw) is the largest and varies with patients in the range (-2.07-3.71 mm, -5.82-5.62 mm, -5.84-3.61 mm; -2.10-2.40°, -2.23-2.60°, and -2.7-3.00°) obtained from mean of XC shifts for each patient. Setup uncer-tainty in IR positioning (0.88, 2.12, 1.40 mm, and 0.64°, 0.83°, 0.96°) is extracted from standard deviation of XC. Systematic uncertainties of the frame (0.18, 0.25, -1.27mm, -0.32°, 0.18°, and 0.47°) and localizer (-0.03, -0.01, 0.03mm, and -0.03°, 0.00°, -0.01°) are extracted from means of all XV setups and mean of all XC distributions, respectively. Uncertainties in isocentricity of the MV radiotherapy machine are (0.27, 0.24, 0.34 mm) and kV imager (0.15, -0.4, 0.21 mm). A statisti-cal model is developed to

  16. Quantitative evaluation of patient setup uncertainty of stereotactic radiotherapy with the frameless 6D ExacTrac system using statistical modeling.

    PubMed

    Keeling, Vance; Hossain, Sabbir; Jin, Hosang; Algan, Ozer; Ahmad, Salahuddin; Ali, Imad

    2016-05-01

    The purpose of this study is to evaluate patient setup accuracy and quantify individual and cumulative positioning uncertainties associated with different hardware and software components of the stereotactic radiotherapy (SRS/SRT) with the frameless 6D ExacTrac system. A statistical model is used to evaluate positioning uncertainties of the different components of SRS/SRT treatment with the Brainlab 6D ExacTrac system using the positioning shifts of 35 patients having cranial lesions. All these patients are immobilized with rigid head-and-neck masks, simulated with Brainlab localizer and planned with iPlan treatment planning system. Stereoscopic X-ray images (XC) are acquired and registered to corresponding digitally reconstructed radiographs using bony-anatomy matching to calculate 6D translational and rotational shifts. When the shifts are within tolerance (0.7 mm and 1°), treatment is initiated. Otherwise corrections are applied and additional X-rays (XV) are acquired to verify that patient position is within tolerance. The uncertainties from the mask, localizer, IR -frame, X-ray imaging, MV, and kV isocentricity are quantified individually. Mask uncertainty (translational: lateral, longitudinal, vertical; rotational: pitch, roll, yaw) is the largest and varies with patients in the range (-2.07-3.71mm,-5.82-5.62mm,-5.84-3.61mm;-2.10-2.40∘,-2.23-2.60∘,and-2.7-3.00∘) obtained from mean of XC shifts for each patient. Setup uncertainty in IR positioning (0.88, 2.12, 1.40 mm, and 0.64°, 0.83°, 0.96°) is extracted from standard deviation of XC. Systematic uncertainties of the frame (0.18, 0.25, -1.27mm, -0.32∘, 0.18°, and 0.47°) and localizer (-0.03, -0.01, 0.03 mm, and -0.03∘, 0.00°, -0.01∘) are extracted from means of all XV setups and mean of all XC distributions, respectively. Uncertainties in isocentricity of the MV radiotherapy machine are (0.27, 0.24, 0.34 mm) and kV imager (0.15, -0.4, 0.21 mm). A statistical model is developed to evaluate

  17. [Patient positioning using in-room kV CT for image-guided radiotherapy (IGRT) of prostate cancer].

    PubMed

    Kliton, Jorgo; Agoston, Péter; Major, Tibor; Polgár, Csaba

    2012-09-01

    The purpose of the study was to evaluate accuracy of patients' set up verified by kV CT-on-rails system and compare automatic and manual image registration of planning and verification kVCT-s. Between January 2001 and March 2011, at ten patients with prostate cancer the clinical target volumes (CTVs) for prostate (CTV-PROS), and prostate plus caudal 1 cm of seminal vesicles (CTV-PVS) with or without pelvic lymph node region were contoured on the treatment planning CT, according to risk category of the patient. Planning target volumes (PTVs) were created with 1 cm margin extended around the CTVs in each direction. The isocentre was marked on the skin with three radiopaque markers. After the set up, treatment couch with the patient was turned by 180 degree and images were acquired of the region of the isocentre with a kV helical CT-on-rails system (treatment CT). An image registration software was used to co-register planning and treatment CT images. Automatic CT image co-registration was followed by manual co-registration taking into account the CTV-PROS contour and soft tissue informations. Deviations of the isocentres in lateral (LAT), longitudinal (LONG) and vertical (VERT) directions were recorded after each image co-registration. Corresponding data were compared using the t-probe. Systematic (S) and random (s) errors of the set up were calculated. Adequate PTV to CTV margins were calculated by van Herk's formula (2.5xS + 0,7xs). Overall 252 deviations were analysed on fourty-two CT series of 10 patients. The mean errors of the set up with automatic and manual image co-registrations were 0.19 cm and 0.07 cm (p=0.001) in LAT, 0.05 cm and 0.03 cm (p=0.07) in LONG and 0.16 cm and 0.22 cm (p=0.16) in VERT directions, respectively. The systematic errors of the set up for automatic and manual image registrations were 0.22 cm and 0.26 cm in LAT, 0.17 cm and 0.18 cm in LONG, 0.25 cm and 0.26 cm in VERT directions, respectively. The random errors of the set up for

  18. SU-E-T-229: Craniospinal Radiotherapy Planning with VMAT, Two First Years Experience

    SciTech Connect

    Lliso, F; Carmona, V; Gimeno, J; Candela-Juan, C; Bautista, J; Richart, J; Perez-Calatayud, J

    2015-06-15

    Purpose: To describe how we moved to VMAT in the craniospinal radiotherapy planning process, the actual procedure details, and the results for the patients treated. Methods: Twelve patients underwent craniospinal irradiation with the new procedure, based on the paper by Lee et al. (IJROBP 82, 2012), with some additional modifications. Patients were treated in supine position in Varian Clinac iX linacs with 6 MV RapidArc; prescription doses ranged from 23.4 to 40 Gy (13 to 20 fractions); depending on the PTV length, 2 or 3 isocenters were used, all coordinates being equal except the longitudinal one, setting a few centimeter-long overlapping region; 2 arcs (RA) sharing isocentre for the cranial region, RA1 encompassing cranium and superior spinal region, and RA2 intended to improve conformity, only for cranium; for spine, 1 or 2 isocenters were employed; optimization was performed with Eclipse (V 13.0) using AAA algorithm, establishing sets of optimization parameters to give high conformity while sparing OAR. In pediatric patients, homogeneous irradiation of the vertebrae was also required.Conformity (CI) and heterogeneity (HI) indices (same as Lee et al.), and mean and maximum doses for OAR were calculated. Several pre-treatment verification methods were used: Octavius4D (PTW) for each isocentre, point dose at the junction region, Portal Dosimetry (when possible), and independent MU verification software (Diamond, PTW). Results: CI median value was 1.02 (0.99–1.07) and HI, 1.07 (1.06–1.09); a great reduction was observed for CI and OAR mean doses with respect to Lee et al. data; median maximum eye lens dose was 7.3 Gy (4.0–12.0); mean LungV20Gy was 1.9%; in children, vertebrae were homogeneously irradiated (D95%=20.8 Gy, Dmean= 23.2 Gy).All pre-treatment verifications were found within our action levels except for Portal Dosimetry. Conclusion: A RapidArc planning process for craniospinal axis irradiation has been implemented with significant advantages on

  19. Portal dosimetry for VMAT using integrated images obtained during treatment.

    PubMed

    Bedford, James L; Hanson, Ian M; Hansen, Vibeke Nordmark

    2014-02-01

    Portal dosimetry provides an accurate and convenient means of verifying dose delivered to the patient. A simple method for carrying out portal dosimetry for volumetric modulated arc therapy (VMAT) is described, together with phantom measurements demonstrating the validity of the approach. Portal images were predicted by projecting dose in the isocentric plane through to the portal image plane, with exponential attenuation and convolution with a double-Gaussian scatter function. Appropriate parameters for the projection were selected by fitting the calculation model to portal images measured on an iViewGT portal imager (Elekta AB, Stockholm, Sweden) for a variety of phantom thicknesses and field sizes. This model was then used to predict the portal image resulting from each control point of a VMAT arc. Finally, all these control point images were summed to predict the overall integrated portal image for the whole arc. The calculated and measured integrated portal images were compared for three lung and three esophagus plans delivered to a thorax phantom, and three prostate plans delivered to a homogeneous phantom, using a gamma index for 3% and 3 mm. A 0.6 cm(3) ionization chamber was used to verify the planned isocentric dose. The sensitivity of this method to errors in monitor units, field shaping, gantry angle, and phantom position was also evaluated by means of computer simulations. The calculation model for portal dose prediction was able to accurately compute the portal images due to simple square fields delivered to solid water phantoms. The integrated images of VMAT treatments delivered to phantoms were also correctly predicted by the method. The proportion of the images with a gamma index of less than unity was 93.7% ± 3.0% (1SD) and the difference between isocenter dose calculated by the planning system and measured by the ionization chamber was 0.8% ± 1.0%. The method was highly sensitive to errors in monitor units and field shape, but less sensitive to

  20. Radiological aspects of gamma knife radiosurgery for arteriovenous malformations and other non-tumoural disorders of the brain.

    PubMed

    Guo, W Y

    1993-01-01

    The aims of the thesis were to investigate stereotaxic procedures in radiosurgery for cerebral arteriovenous malformations (AVMs) and radiation effects of single session high-dose irradiation delivered by gamma knife on the human brain. Investigation of gamma knife radiosurgery in 1,464 patients constitutes the data base of this thesis. High quality stereotaxic angiography is the gold standard targeting imaging in radiosurgery for cerebral AVMs, particularly for small AVMs or residual AVMs after other treatments. For medium and large size AVMs, stereotaxic MR techniques can improve targeting precision and decrease irradiation volume as compared to stereotaxic angiography in selected cases provided that proper pulse sequences are used. Combined treatments, where embolization precedes radiosurgery, can improve amenability of the treatment for large AVMs. This is on condition that the partially embolized nidi are well delineated and the volume of the residual nidi has been decreased to a level where an optimum irradiation can be safely prescribed. Radiologically, adverse radiation effects (ARE) of gamma knife radiosurgery for cerebral AVMs are observed in 16% (131/816) of the patients. The ARE are observed as a focal low attenuation on CT or as a focal high signal on MR image without enhancement in 47% (61/131), and as a peripheral or homogeneous enhancing lesion in 48% (63/131). MR imaging is more sensitive than CT in detecting the ARE. 91% of the ARE are observed within 18 months after radiosurgery and 89% are seen to regress within 18 months. Clinically, symptomatic ARE are only observed in 6% (51/816) and only in half of them, i.e. 3%, are the symptoms permanent. The risk of ARE in radiosurgery for venous angiomas is higher as compared to AVMs. Other mechanisms have probably been employed. In gamma capsulotomy, the necrotic lesions and reaction volumes created by using multiple isocentres of 4 mm collimators are less predictable as compared to that by single

  1. Locoregional Treatment for Breast Carcinoma After Hodgkin's Lymphoma: The Breast Conservation Option

    SciTech Connect

    Haberer, Sophie; Belin, Lisa; Le Scodan, Romuald; Kirova, Youlia M.; Savignoni, Alexia; Stevens, Denise; Moisson, Patricia; Decaudin, Didier; Pierga, Jean-Yves; Reyal, Fabien; Campana, Francois; Fourquet, Alain; Bollet, Marc A.

    2012-02-01

    Purpose: To report clinical and pathologic characteristics and outcome of breast cancer (BC) after irradiation for Hodgkin's lymphoma (HL) in women treated at the Institut Curie, with a special focus on the breast-conserving option. Methods and Materials: Medical records of 72 women who developed either ductal carcinoma in situ or Stage I-III invasive carcinoma of the breast after HL between 1978 and 2009 were retrospectively reviewed. Results: Median age at HL diagnosis was 23 years (range, 14-53 years). Median total dose received by the mediastinum was 40 Gy, mostly by a mantle-field technique. Breast cancers occurred after a median interval of 21 years (range, 5-40 years). Ductal invasive carcinoma and ductal carcinoma in situ represented, respectively, 51 cases (71%) and 14 cases (19%). Invasive BCs consisted of 47 cT0-2 tumors (82%), 5 cN1-3 tumors (9%), and 20 Grade 3 tumors (35%). Locoregional treatment for BCs consisted of mastectomy with (3) or without (36) radiotherapy in 39 patients and lumpectomy with (30) or without (2) adjuvant radiotherapy in 32 patients. The isocentric lateral decubitus radiation technique was used in 17 patients after breast-conserving surgery (57%). With a median follow-up of 7 years, 5-year overall survival rate and locoregional control rate were, respectively, 74.5% (95% confidence interval [CI], 64-88%) and 82% (95% CI, 72-93%) for invasive carcinoma and 100% (95% CI, 100 -100%) and 92% (95% CI, 79-100%) for in situ carcinoma. In patients with invasive tumors, the 5-year distant disease-free survival rate was 79% (95% CI, 69-91%), and 13 patients died of progressive BC. Contralateral BC was diagnosed in 10 patients (14%). Conclusions: Breast-conserving treatment can be an option for BCs that occur after HL, despite prior thoracic irradiation. It should consist of lumpectomy and adjuvant breast radiotherapy with use of adequate techniques, such as the lateral decubitus isocentric position, to protect the underlying heart and

  2. SU-E-T-226: Junction Free Craniospinal Irradiation in Linear Accelerator Using Volumetric Modulated Arc Therapy : A Novel Technique Using Dose Tapering

    SciTech Connect

    Sarkar, B; Roy, S; Paul, S; Munshi, A; Roy, Shilpi; Jassal, K; Ganesh, T; Mohanti, BK

    2014-06-01

    Purpose: Spatially separated fields are required for craniospinal irradiation due to field size limitation in linear accelerator. Field junction shits are conventionally done to avoid hot or cold spots. Our study was aimed to demonstrate the feasibility of junction free irradiation plan of craniospinal irradiation (CSI) for Meduloblastoma cases treated in linear accelerator using Volumetric modulated arc therapy (VMAT) technique. Methods: VMAT was planned using multiple isocenters in Monaco V 3.3.0 and delivered in Elekta Synergy linear accelerator. A full arc brain and 40° posterior arc spine fields were planned using two isocentre for short (<1.3 meter height ) and 3 isocentres for taller patients. Unrestricted jaw movement was used in superior-inferior direction. Prescribed dose to PTV was achieved by partial contribution from adjacent beams. A very low dose gradient was generated to taper the isodoses over a long length (>10 cm) at the conventional field junction. Results: In this primary study five patients were planned and three patients were delivered using this novel technique. As the dose contribution from the adjacent beams were varied (gradient) to create a complete dose distribution, therefore there is no specific junction exists in the plan. The junction were extended from 10–14 cm depending on treatment plan. Dose gradient were 9.6±2.3% per cm for brain and 7.9±1.7 % per cm for spine field respectively. Dose delivery error due to positional inaccuracy was calculated for brain and spine field for ±1mm, ±2mm, ±3mm and ±5 mm were 1%–0.8%, 2%–1.6%, 2.8%–2.4% and 4.3%–4% respectively. Conclusion: Dose tapering in junction free CSI do not require a junction shift. Therefore daily imaging for all the field is also not essential. Due to inverse planning dose to organ at risk like thyroid kidney, heart and testis can be reduced significantly. VMAT gives a quicker delivery than Step and shoot or dynamic IMRT.

  3. SU-E-T-80: Comparison of Fluence-Based RapidArc QAs Using EPID and MapCHECK 2

    SciTech Connect

    Jin, H; Jesseph, F; Ahmad, S

    2014-06-01

    Purpose: To compare the Varian aS-1000 EPID imager to the isocentrically mounted MapCHECK 2 diode array for RapidArc QAs as a function of photon beam energy. Methods: A Varian TrueBeam STx with an aS-1000 digital imaging panel was used to acquire RapidArc QA images for 13 patient plans; each plan QA was performed at 6, 8, 10 and 15MV energies. The Portal Dose Image Prediction algorithm in the Varian Eclipse treatment planning system (TPS) was used to create the comparison image for the EPID acquisition. A Sun Nuclear MapCHECK 2 diode array on an isocentric mounting fixture with 5 cm water-equivalent buildup was also used for the RapidArc QAs. A composite dose plane was taken from the Eclipse TPS for comparison to the MapCHECK 2 measurements. A gamma test was implemented in the Sun Nuclear Patient software with 10% threshold and absolute comparison for both QA methods. The two-tailed paired t-test was employed to analyze the statistical significance between two methods at the 95% confidence level. Results: The average gamma passing rates were greater than 95% at 3%/3mm using both methods for all four energies. The average passing rates were within 2.5% and 1.1% of each other when analyzed at 2%/2mm and 3%/3mm conditions, respectively. The EPID passing rates were somewhat better than the MapCHECK 2 when analyzed at 1%/1mm condition; this difference decreased with increasing energy (9.1% at 6MV to 2.7% at 15MV). The differences were not statistically significant for all criteria and energies (p-value ã 0.05). Conclusion: EPID-based RapidArc QA results are comparable to MapCHECK 2 when using 3%/3mm criteria at all four energies. EPID-based QA shows potential for being the superior device under strict gamma criteria.

  4. Dosimetry and mechanical accuracy of the first rotating gamma system installed in North America.

    PubMed

    Kubo, Hideo D; Araki, Fujio

    2002-11-01

    The purpose of this paper is to present the dosimetry and mechanical accuracy of the first rotating gamma system (RGS) installed in North America for stereotactic radiosurgery. The data were obtained during the installation, acceptance test procedure, and commissioning of the unit. The RGS unit installed at UC Davis Cancer Center (RGSu) has modifications on the source and collimator bodies from the earlier version of the Chinese RGS (RGSc). The differences between these two RGSs are presented. The absolute dose at the focal point was measured in a 16-cm-diam acrylic phantom using a small volume chamber, which was calibrated at the University of Wisconsin Accredited Dosimetry Calibration Laboratory (UW-ADCL). The dose in acrylic was then converted to a dose in water. A collimator output factor from each of the four different collimator sizes ranging from 4, 8, 14, and 18 mm was measured with (1) a smaller volume chamber and (2) approximately 3.0 mm x 3.0 mm x 1.0 mm TLD chips in the same acrylic phantom. The Gafchromic films were used for the dose profile, collimator output factor, and mechanical/radiation field isocentricity measurements. The TLD chips were processed in-house whereas Gafchromic films were processed both at the UW-ADCL and in-house. The timer error, timer accuracy, and timer linearity were also determined. The dose profiles were found to be similar between RGSc and RGSu. The 4 mm collimator output factor of the RGSu was approximately 0.6, similar to that from RGSc, in comparison to 0.8 in the report for a Leksell Model U Gamma-Knife. The mechanical/radiation field isocentricity for RGSc and RGSu is found to be similar and is within 0.3 mm in both X and Y directions. In the Z direction, the beam center of the RGSu is shifted toward the sources by 0.75 mm from the mechanical isocenter whereas no data are available for RGSc. Little dosimetric difference is found between RGSu and RGSc. It is reported that RGSc has the same dosimetric and mechanical

  5. The use of compensators to optimise the three dimensional dose distribution in radiotherapy of the intact breast.

    PubMed

    Carruthers, L J; Redpath, A T; Kunkler, I H

    1999-03-01

    Dose heterogeneity in tangential breast irradiation has been shown to be as high as 20% and may lead to problems in local control and cosmesis. In this study, dose heterogeneity in three dimensions (3D) in the breast irradiated with wedged tangential beams is assessed and the improvement which can be made by the use of individualised two dimensional (2D) compensators is established. The compensation required is calculated in two ways: (I) by an iterative technique giving a uniform dose on a plane through the isocentre normal to the central axis of each beam, and (II) by inverse planning using an optimisation technique based on simulated annealing. A total of 17 patients with histologically proven T0-3, N0, N1, M0 breast cancer undergoing breast irradiation following wide local excision, were CT scanned using contiguous 1 cm slices from approximately 2 cm superior to 2 cm inferior of the irradiated volume. The dose distributions are determined using a 3D algorithm that calculates primary and scatter dose separately using a differential scatter air ratio method and corrects both for the presence of heterogeneities. The iterative technique achieves a dose variation of better than 0.5% on the plane through the isocentre with compensation on both beams. Compensation for the lateral beam only is calculated using the optimisation technique in order to minimise the scatter dose to the contralateral breast. The optimisation algorithm minimises the dose variance over the target and sets upper dose limits for the lung and the remainder of the irradiated volume. For the group of patients the average dose heterogeneity in 3D using wedges is 12% (range 8-17%), which reduces to 8% (5-16%) using compensation on a plane and to 5% (4-7%) using the optimisation technique. Inverse planning is normally used for complex radiotherapy techniques but when applied to tangential breast irradiation, can reduce the dose heterogeneity through the breast as a whole to as little as 4%, with

  6. SU-E-J-139: One Institution’s Experience with Surface Imaging in Proton Therapy

    SciTech Connect

    Zhao, L; Singh, H; Zheng, Y

    2015-06-15

    Purpose: X-ray system is commonly used for IGRT in proton therapy, however image acquisition not only increases treatment time but also adds imaging dose. We studied a 3D surface camera system (AlignRT) performance for proton therapy. Methods: System accuracy was evaluated with rigid phantom under two different camera location configurations. For initial clinical applications, post mastectomy chest wall and partial breast treatments were studied. X-ray alignment was used as our ground truth. Our studies included: 1) comparison of daily patient setup shifts between X-ray alignment and SI calculation; 2) interfractional breast surface position variation when aligning to bony landmark on X-ray; 3) absolute positioning using planning CT DICOM data; 4) shifts for multi-isocenter treatment plan; 5) couch isocentric rotation accuracy. Results: Camera locations affected the system performance. After camera relocation, the accuracy of the system for the rigid phantom was within 1 mm (fixed couch), and 1.5 mm (isocentric rotation). For intrafractional patient positioning, X-ray and AlignRT shifts were highly correlated (r=0.99), with the largest difference (mean ± SD) in the longitudinal direction (2.14 ± 1.02 mm). For interfractional breast surface variation and absolute positioning, there were still larger disagreements between the two modalities due to different focus on anatomical landmarks, and 95% of the data lie within 5mm with some outliers at 7 mm–9 mm. For multi-isocenter shifts, the difference was 1 ± 0.56 mm over an 11 cm shift in longitudinal direction. For couch rotation study, the differences was 1.36 ± 1.0 mm in vertical direction, 3.04 ± 2.11 mm in longitudinal direction, and 2.10 ± 1.66 mm in lateral direction, with all rotation differences < 1.5 degree. Conclusion: Surface imaging is promising for intrafractional treatment application in proton therapy to reduce X-ray frequency. However the interfractional discrepancy between the X-ray and SI

  7. SU-E-J-213: Imaging and Treatment Isocenter Verification of a Gantry Mounted Proton Therapy System

    SciTech Connect

    Price, S; Goddu, S; Rankine, L; Klein, E

    2014-06-01

    Purpose: The Mevion proton therapy machine is the first to feature a gantry mounted sychro-cyclotron. In addition, the system utilizes a 6D motion couch and kV imaging for precise proton therapy. To quantify coincidence between these systems, isocentricity tests were performed based on kV imaging alignment using radiochromic film. Methods: The 100 ton gantry and 6D robotic couch can rotate 190° around isocenter to provide necessary beam angles for treatment. The kV sources and detector panels are deployed as needed to acquire orthogonal portals. Gantry and couch mechanical isocenter were tested using star-shots and radiochromic-film (RCF). Using kV imaging, the star-shot phantom was aligned to an embedded fiducial and the isocenter was marked on RCF with a pinprick. The couch and gantry stars were performed by irradiating films at every 45° and 30°, respectively. A proton beam with a range and modulation-width of 18 cm was used. A Winston-Lutz test was also performed at the same gantry and couch rotations using a custom jig holding RCF and a tungsten ball placed at isocenter. A 2 cm diameter circular aperture was used for the irradiation. Results: The couch star-shot indicated a minimum tangent circle of 0.6 mm, with a 0.9 mm offset from the manually marked isocenter. The gantry star-shot showed a 0.6 mm minimum tangent circle with a 0.5 mm offset from the pinprick. The Winston Lutz test performed for gantry rotation showed a maximum deviation from center of 0.5 mm. Conclusion: Based on star-shots and Winston-Lutz tests, the proton gantry and 6D couch isocentricity are within 1 mm. In this study, we have shown that the methods commonly utilized for Linac characterization can be applied to proton therapy. This revolutionary proton therapy system possesses excellent agreement between the mechanical and radiation isocenter, providing highly precise treatment.

  8. SU-E-T-648: Quality Assurance Using the RADPOS System for 4D Radiotherapy with CyberKnife

    SciTech Connect

    Marants, R; Vandervoort, E; Cygler, J E

    2015-06-15

    Purpose: The CyberKnife robotic radiosurgery system uses Synchrony respiratory motion compensation, which requires independent performance verification. In this work, the RADPOS 4D dosimetry system’s motion measurements are compared with internal fiducial position measurements. In addition, RADPOS measurements are compared with Synchrony’s predictive correlation model, which is based on internal fiducial and external LED marker position measurements. Methods: A treatment plan was created for a lung insert containing fiducials, RADPOS detector, and Solid Water tumor phantom. Two Quasar Respiratory Motion Phantoms (Q1 and Q2) and two RADPOS detectors (R1 and R2) were used: Q1 simulated lung motion with a lung insert moving in the superior/inferior direction, while Q2 simulated chest motion with a chest platform moving in the anterior/posterior direction. Before treatment, R1 was secured inside of the tumor phantom within Q1, while LED markers and R2 were positioned on the chest platform of Q2. Two treatment delivery cases were studied: isocentric plan (I) and non-isocentric patient plan (P). Four motion cases were studied: no motion (0), sinusoidal and in-phase (1), sinusoidal and out-of-phase (2), patient waveform and out-of-phase (3). A coordinate alignment algorithm was implemented, allowing RADPOS and model position data to be compared within the fiducial coordinate system. Results: The standard deviation of the differences between RADPOS and fiducial position measurements was below 0.6 mm for all experimental cases. The standard deviation of the differences between RADPOS and model position data was 1.0, 1.5, and 1.6 mm along the primary direction of motion for case I1, I2, and P3, respectively. Conclusion: Our work demonstrates that RADPOS is a useful tool for independent quality assurance of CyberKnife treatment with Synchrony respiratory compensation. RADPOS and fiducial position measurement closely match, and RADPOS confirms the effectiveness of Cyber

  9. SU-E-T-539: Maximum Energy of Helium and Carbon Ions Clinically Needed for Spine, Lung, Prostate and Pancreas Cancer

    SciTech Connect

    Pompos, A; Choy, H; Jia, X; Jiang, S; Timmerman, R

    2015-06-15

    Purpose: Maximum available kinetic energy of accelerated heavy ions is a critical parameter to consider during the establishment of a heavy ion therapy center. It dictates the maximum range in tissue and determines the size and cost of ion gantry. We have started planning our heavy ion therapy center and we report on the needed ion range. Methods: We analyzed 50 of random SBRT-spine, SBRT- lung, prostate and pancreatic cancer patients from our photon clinic. In the isocentric axial CT cut we recorded the maximum water equivalent depth (WED4Field) of PTV’s most distal edge in four cardinal directions and also in a beam direction that required the largest penetration, WEDGantry. These depths were then used to calculate the percentage of our patients we would be able to treat as a function of available maximum carbon and helium beam energy. Based on the Anterior-Posterior WED for lung patients and the maximum available ion energy we estimated the largest possible non-coplanar beam entry angle φ (deviation from vertical) in the isocentric vertical sagittal plane. Results: We found that if 430MeV/u C-12, equivalently 220MeV/u He-4, beams are available, more than 96% (98%) of all patients can be treated without any gantry restrictions (in cardinals angles only) respectively. If the energy is reduced to 400MeV/u C-12, equivalently 205MeV/u He-4, the above fractions reduce to 80% (87%) for prostate and 88% (97%) for other sites. This 7% energy decrease translates to almost 5% gantry size and cost decrease for both ions. These energy limits in combination with the WED in the AP direction for lung patients resulted in average non-coplanar angles of φ430MeV/u = 68°±8° and φ400MeV/u = 65°±10° if nozzle clearance permits them. Conclusion: We found that the two worldwide most common maximum carbon beam energies will treat above 80% of all our patients.

  10. Design of a modulated orthovoltage stereotactic radiosurgery system.

    PubMed

    Fagerstrom, Jessica M; Bender, Edward T; Lawless, Michael J; Culberson, Wesley S

    2017-07-01

    To achieve stereotactic radiosurgery (SRS) dose distributions with sharp gradients using orthovoltage energy fluence modulation with inverse planning optimization techniques. A pencil beam model was used to calculate dose distributions from an orthovoltage unit at 250 kVp. Kernels for the model were derived using Monte Carlo methods. A Genetic Algorithm search heuristic was used to optimize the spatial distribution of added tungsten filtration to achieve dose distributions with sharp dose gradients. Optimizations were performed for depths of 2.5, 5.0, and 7.5 cm, with cone sizes of 5, 6, 8, and 10 mm. In addition to the beam profiles, 4π isocentric irradiation geometries were modeled to examine dose at 0.07 mm depth, a representative skin depth, for the low energy beams. Profiles from 4π irradiations of a constant target volume, assuming maximally conformal coverage, were compared. Finally, dose deposition in bone compared to tissue in this energy range was examined. Based on the results of the optimization, circularly symmetric tungsten filters were designed to modulate the orthovoltage beam across the apertures of SRS cone collimators. For each depth and cone size combination examined, the beam flatness and 80-20% and 90-10% penumbrae were calculated for both standard, open cone-collimated beams as well as for optimized, filtered beams. For all configurations tested, the modulated beam profiles had decreased penumbra widths and flatness statistics at depth. Profiles for the optimized, filtered orthovoltage beams also offered decreases in these metrics compared to measured linear accelerator cone-based SRS profiles. The dose at 0.07 mm depth in the 4π isocentric irradiation geometries was higher for the modulated beams compared to unmodulated beams; however, the modulated dose at 0.07 mm depth remained <0.025% of the central, maximum dose. The 4π profiles irradiating a constant target volume showed improved statistics for the modulated, filtered

  11. Radiotoxicity in robotic radiosurgery: proposing a new quality index for optimizing the treatment planning of brain metastases.

    PubMed

    Hellerbach, Alexandra; Luyken, Klaus; Hoevels, Mauritius; Gierich, Andreas; Rueß, Daniel; Baus, Wolfgang W; Kocher, Martin; Ruge, Maximilian I; Treuer, Harald

    2017-08-17

    As irradiated brain volume at 12 Gy (V12) is a predictor for radionecrosis, the purpose of the study was to develop a model for Cyberknife (CK) plans that is able to predict the lowest achievable V12 at a given tumor size and prescription dose (PD), and to suggest a new quality index regarding V12 for optimizing the treatment planning of brain metastases. In our model V12 was approximated as a spherical shell around the tumor volume. The radial distance between tumor surface and the 12 Gy isodose line was calculated using an approximation of the mean dose gradient in that area. Assuming a radially symmetrical irradiation from the upper half space, the dose distribution is given by the superposition of single fields. The dose profiles of a single field were derived by the measured off-center ratios (OCR) of the CK system. Using the calculated gradients of the sum dose profiles, minimal-V12 was estimated for different tumor sizes. The model calculation was tested using a phantom dataset and retrospectively applied on clinical cases. Our model allows the prediction of a best-case scenario for V12 at a given tumor size and PD which was confirmed by the results of the isocentric phantom plans. The results of the non-isocentric phantom plans showed that an optimization of coverage caused an increase in V12. This was in accordance with the results of the retrospective analysis. V12 s of the clinical cases were on average twice that of the predicted model calculation. A good agreement was achieved for plans with an optimal conformity index (nCI). Re-planning of cases with high V12 showed that lower values could be reached by selecting smaller collimators and by allowing a larger number of total MU and more MU per beam. V12 is a main parameter for assessing plan quality in terms of radiotoxicity. The index f12 defined as the ratio of V12 from the actual plan with the evaluated V12 from our model describes the conformity of an optimally possible V12 and thus can be used

  12. Portal dosimetry for VMAT using integrated images obtained during treatment

    SciTech Connect

    Bedford, James L. Hanson, Ian M.; Hansen, Vibeke Nordmark

    2014-02-15

    Purpose: Portal dosimetry provides an accurate and convenient means of verifying dose delivered to the patient. A simple method for carrying out portal dosimetry for volumetric modulated arc therapy (VMAT) is described, together with phantom measurements demonstrating the validity of the approach. Methods: Portal images were predicted by projecting dose in the isocentric plane through to the portal image plane, with exponential attenuation and convolution with a double-Gaussian scatter function. Appropriate parameters for the projection were selected by fitting the calculation model to portal images measured on an iViewGT portal imager (Elekta AB, Stockholm, Sweden) for a variety of phantom thicknesses and field sizes. This model was then used to predict the portal image resulting from each control point of a VMAT arc. Finally, all these control point images were summed to predict the overall integrated portal image for the whole arc. The calculated and measured integrated portal images were compared for three lung and three esophagus plans delivered to a thorax phantom, and three prostate plans delivered to a homogeneous phantom, using a gamma index for 3% and 3 mm. A 0.6 cm{sup 3} ionization chamber was used to verify the planned isocentric dose. The sensitivity of this method to errors in monitor units, field shaping, gantry angle, and phantom position was also evaluated by means of computer simulations. Results: The calculation model for portal dose prediction was able to accurately compute the portal images due to simple square fields delivered to solid water phantoms. The integrated images of VMAT treatments delivered to phantoms were also correctly predicted by the method. The proportion of the images with a gamma index of less than unity was 93.7% ± 3.0% (1SD) and the difference between isocenter dose calculated by the planning system and measured by the ionization chamber was 0.8% ± 1.0%. The method was highly sensitive to errors in monitor units and

  13. Portal dosimetry for VMAT using integrated images obtained during treatment

    SciTech Connect

    Bedford, James L. Hanson, Ian M.; Hansen, Vibeke Nordmark

    2014-02-15

    Purpose: Portal dosimetry provides an accurate and convenient means of verifying dose delivered to the patient. A simple method for carrying out portal dosimetry for volumetric modulated arc therapy (VMAT) is described, together with phantom measurements demonstrating the validity of the approach. Methods: Portal images were predicted by projecting dose in the isocentric plane through to the portal image plane, with exponential attenuation and convolution with a double-Gaussian scatter function. Appropriate parameters for the projection were selected by fitting the calculation model to portal images measured on an iViewGT portal imager (Elekta AB, Stockholm, Sweden) for a variety of phantom thicknesses and field sizes. This model was then used to predict the portal image resulting from each control point of a VMAT arc. Finally, all these control point images were summed to predict the overall integrated portal image for the whole arc. The calculated and measured integrated portal images were compared for three lung and three esophagus plans delivered to a thorax phantom, and three prostate plans delivered to a homogeneous phantom, using a gamma index for 3% and 3 mm. A 0.6 cm{sup 3} ionization chamber was used to verify the planned isocentric dose. The sensitivity of this method to errors in monitor units, field shaping, gantry angle, and phantom position was also evaluated by means of computer simulations. Results: The calculation model for portal dose prediction was able to accurately compute the portal images due to simple square fields delivered to solid water phantoms. The integrated images of VMAT treatments delivered to phantoms were also correctly predicted by the method. The proportion of the images with a gamma index of less than unity was 93.7% ± 3.0% (1SD) and the difference between isocenter dose calculated by the planning system and measured by the ionization chamber was 0.8% ± 1.0%. The method was highly sensitive to errors in monitor units and

  14. Dosimetric Study of Automatic Brain Metastases Planning in Comparison with Conventional Multi-Isocenter Dynamic Conformal Arc Therapy and Gamma Knife Radiosurgery for Multiple Brain Metastases

    PubMed Central

    Kaneda, Naoki; Hagiwara, Masahiro; Ishiguchi, Tuneo

    2016-01-01

    Objective The efficacy of stereotactic radiosurgery (SRS) using Gamma Knife (GK) (Elekta, Tokyo) is well known. Recently, Automatic Brain Metastases Planning (ABMP) Element (BrainLAB, Tokyo) for a LINAC-based radiation system was commercially released. It covers multiple off-isocenter targets simultaneously inside a multi-leaf collimator field and enables SRS / stereotactic radiotherapy (SRT) with a single group of LINAC-based dynamic conformal multi-arcs (DCA) for multiple brain metastases. In this study, dose planning of ABMP (ABMP-single isocenter DCA (ABMP-SIDCA)) for SRS of small multiple brain metastases was evaluated in comparison with those of conventional multi-isocenter DCA (MIDCA-SRS) (iPlan, BrainLAB, Tokyo) and GK-SRS (GKRS). Methods Simulation planning was performed with ABMP-SIDCA and GKRS in the two cases of multiple small brain metastases (nine tumors in both), which had been originally treated with iPlan-MIDCA. First, a dosimetric comparison was done between ABMP-SIDCA and iPlan-MIDCA in the same setting of planning target volume (PTV) margin and D95 (dose covering 95% of PTV volume). Second, dosimetry of GKRS with a margin dose of 20 Gy was compared with that of ABMP-SIDCA in the setting of PTV margin of 0, 1 mm, and 2 mm, and D95=100% dose (20 Gy). Results First, the maximum dose of PTV and minimum dose of gross tumor volume (GTV) were significantly greater in ABMP-SIDCA than in iPlan-MIDCA. Conformity index (CI, 1/Paddick’s CI) and gradient index (GI, V (half of prescription dose) / V (prescription dose)) in ABMP-SIDCA were comparable with those of iPlan-MIDCA. Second, PIV (prescription isodose volume) of GKRS was consistent with that of 1 mm margin - ABMP-SIDCA plan in Case 1 and that of no-margin ABMP-SIDCA plan in Case 2. Considering the dose gradient, the mean of V (half of prescription dose) of ABMP-SIDCA was not broad, comparable to GKRS, in either Case 1 or 2. Conclusions The conformity and dose gradient with ABMP-SIDCA were as good

  15. Helical Tomotherapy-Based STAT RT: Dosimetric Evaluation for Clinical Implementation of a Rapid Radiation Palliation Program

    SciTech Connect

    McIntosh, Alyson; Dunlap, Neal; Sheng, Ke; Geezey, Constance; Turner, Benton; Blackhall, Leslie; Weiss, Geoffrey; Lappinen, Eric; Larner, James M.; Read, Paul W.

    2010-01-01

    Helical tomotherapy-based STAT radiation therapy (RT) uses an efficient software algorithm for rapid intensity-modulated treatment planning, enabling conformal radiation treatment plans to be generated on megavoltage computed tomography (MVCT) scans for CT simulation, treatment planning, and treatment delivery in one session. We compared helical tomotherapy-based STAT RT dosimetry with standard linac-based 3D conformal plans and standard helical tomotherapy-based intensity-modulated radiation therapy (IMRT) dosimetry for palliative treatments of whole brain, a central obstructive lung mass, multilevel spine disease, and a hip metastasis. Specifically, we compared the conformality, homogeneity, and dose with regional organs at risk (OARs) for each plan as an initial step in the clinical implementation of a STAT RT rapid radiation palliation program. Hypothetical planning target volumes (PTVs) were contoured on an anthropomorphic phantom in the lung, spine, brain, and hip. Treatment plans were created using three planning techniques: 3D conformal on Pinnacle{sup 3}, helical tomotherapy, and helical tomotherapy-based STAT RT. Plan homogeneity, conformality, and dose to OARs were analyzed and compared. STAT RT and tomotherapy improved conformality indices for spine and lung plans (CI spine = 1.21, 1.17; CI lung = 1.20, 1.07, respectively) in comparison with standard palliative anteroposterior/posteroanterior (AP/PA) treatment plans (CI spine = 7.01, CI lung = 7.30), with better sparing of heart, esophagus, and spinal cord. For palliative whole-brain radiotherapy, STAT RT and tomotherapy reduced maximum and mean doses to the orbits and lens (maximum/mean lens dose: STAT RT = 2.94/2.65 Gy, tomotherapy = 3.13/2.80 Gy, Lateral opposed fields = 7.02/3.65 Gy), with an increased dose to the scalp (mean scalp dose: STAT RT = 16.19 Gy, tomotherapy = 15.61 Gy, lateral opposed fields = 14.01 Gy). For bony metastatic hip lesions, conformality with both tomotherapy techniques (CI

  16. Dosimetric Study of Automatic Brain Metastases Planning in Comparison with Conventional Multi-Isocenter Dynamic Conformal Arc Therapy and Gamma Knife Radiosurgery for Multiple Brain Metastases.

    PubMed

    Mori, Yoshimasa; Kaneda, Naoki; Hagiwara, Masahiro; Ishiguchi, Tuneo

    2016-11-15

    The efficacy of stereotactic radiosurgery (SRS) using Gamma Knife (GK) (Elekta, Tokyo) is well known. Recently, Automatic Brain Metastases Planning (ABMP) Element (BrainLAB, Tokyo) for a LINAC-based radiation system was commercially released. It covers multiple off-isocenter targets simultaneously inside a multi-leaf collimator field and enables SRS / stereotactic radiotherapy (SRT) with a single group of LINAC-based dynamic conformal multi-arcs (DCA) for multiple brain metastases. In this study, dose planning of ABMP (ABMP-single isocenter DCA (ABMP-SIDCA)) for SRS of small multiple brain metastases was evaluated in comparison with those of conventional multi-isocenter DCA (MIDCA-SRS) (iPlan, BrainLAB, Tokyo) and GK-SRS (GKRS). Simulation planning was performed with ABMP-SIDCA and GKRS in the two cases of multiple small brain metastases (nine tumors in both), which had been originally treated with iPlan-MIDCA. First, a dosimetric comparison was done between ABMP-SIDCA and iPlan-MIDCA in the same setting of planning target volume (PTV) margin and D95 (dose covering 95% of PTV volume). Second, dosimetry of GKRS with a margin dose of 20 Gy was compared with that of ABMP-SIDCA in the setting of PTV margin of 0, 1 mm, and 2 mm, and D95=100% dose (20 Gy). First, the maximum dose of PTV and minimum dose of gross tumor volume (GTV) were significantly greater in ABMP-SIDCA than in iPlan-MIDCA. Conformity index (CI, 1/Paddick's CI) and gradient index (GI, V (half of prescription dose) / V (prescription dose)) in ABMP-SIDCA were comparable with those of iPlan-MIDCA. Second, PIV (prescription isodose volume) of GKRS was consistent with that of 1 mm margin - ABMP-SIDCA plan in Case 1 and that of no-margin ABMP-SIDCA plan in Case 2. Considering the dose gradient, the mean of V (half of prescription dose) of ABMP-SIDCA was not broad, comparable to GKRS, in either Case 1 or 2. The conformity and dose gradient with ABMP-SIDCA were as good as those of conventional MIDCA for each

  17. Optimal technique of linear accelerator-based stereotactic radiosurgery for tumors adjacent to brainstem.

    PubMed

    Chang, Chiou-Shiung; Hwang, Jing-Min; Tai, Po-An; Chang, You-Kang; Wang, Yu-Nong; Shih, Rompin; Chuang, Keh-Shih

    2016-01-01

    Stereotactic radiosurgery (SRS) is a well-established technique that is replacing whole-brain irradiation in the treatment of intracranial lesions, which leads to better preservation of brain functions, and therefore a better quality of life for the patient. There are several available forms of linear accelerator (LINAC)-based SRS, and the goal of the present study is to identify which of these techniques is best (as evaluated by dosimetric outcomes statistically) when the target is located adjacent to brainstem. We collected the records of 17 patients with lesions close to the brainstem who had previously been treated with single-fraction radiosurgery. In all, 5 different lesion catalogs were collected, and the patients were divided into 2 distance groups-1 consisting of 7 patients with a target-to-brainstem distance of less than 0.5cm, and the other of 10 patients with a target-to-brainstem distance of ≥ 0.5 and < 1cm. Comparison was then made among the following 3 types of LINAC-based radiosurgery: dynamic conformal arcs (DCA), intensity-modulated radiosurgery (IMRS), and volumetric modulated arc radiotherapy (VMAT). All techniques included multiple noncoplanar beams or arcs with or without intensity-modulated delivery. The volume of gross tumor volume (GTV) ranged from 0.2cm(3) to 21.9cm(3). Regarding the dose homogeneity index (HIICRU) and conformity index (CIICRU) were without significant difference between techniques statistically. However, the average CIICRU = 1.09 ± 0.56 achieved by VMAT was the best of the 3 techniques. Moreover, notable improvement in gradient index (GI) was observed when VMAT was used (0.74 ± 0.13), and this result was significantly better than those achieved by the 2 other techniques (p < 0.05). For V4Gy of brainstem, both VMAT (2.5%) and IMRS (2.7%) were significantly lower than DCA (4.9%), both at the p < 0.05 level. Regarding V2Gy of normal brain, VMAT plans had attained 6.4 ± 5%; this was significantly better (p < 0.05) than

  18. Transient enlargement of contrast uptake on MRI after linear accelerator (linac) stereotactic radiosurgery for brain metastases.

    PubMed

    Huber, P E; Hawighorst, H; Fuss, M; van Kaick, G; Wannenmacher, M F; Debus, J

    2001-04-01

    With the increasing number of patients successfully treated with stereotactic radiosurgery for brain metastases, decision making after therapy based on follow-up imaging findings becomes more and more important. Magnetic resonance imaging (MRI) is the most sensitive means for follow-up studies. The objective of this study was to investigate the treatment outcome of our radiosurgery program and to describe the response of brain metastases to contrast-enhanced MRI after linear accelerator (linac) stereotactic radiosurgery and identify factors to distinguish among local control and local failure. Using serial MRI, we followed the course of 87 brain metastases in 48 consecutive patients treated between September 1996 and November 1997 with linac-based radiosurgery with 15-MV photons. Treatment planning was performed on an MR data cube. For spherical metastases, radiosurgery was delivered using a 9 noncoplanar arc technique with circular-shaped collimators. For irregularly shaped targets, radiosurgery was delivered using a manually driven multi-leaf collimator with a leaf width of 1.5 mm projected to the isocenter. Median radiosurgery dose was 20 Gy prescribed to the 80% isodose. Together with whole brain radiotherapy (20 x 2 Gy, 5/w), a median radiosurgical dose of 15 Gy was delivered. Median follow-up was 8 (range 2--36) months. Factors influencing local control and survival rates were analyzed with respect to MRI response, and Kaplan-Meier curves were calculated. Actuarial local tumor control was 91% at one and two years. Patient survival at one and two years was 30% and 18%. Median survival was 9 months. During follow-up in 70 (81%) of the 87 treated metastases, the contrast-enhancing volumes on T1W images were stable or disappeared partly or completely. A transient enlargement of contrast-enhancing volumes was observed in 11 (12%) of the 87 lesions treated, while a progressive enlargement due to local treatment failure was observed in 6 (7%) of the 87 treated

  19. A pencil beam dose calculation model for CyberKnife system.

    PubMed

    Liang, Bin; Li, Yongbao; Liu, Bo; Zhou, Fugen; Xu, Shouping; Wu, Qiuwen

    2016-10-01

    CyberKnife system is initially equipped with fixed circular cones for stereotactic radiosurgery. Two dose calculation algorithms, Ray-Tracing and Monte Carlo, are available in the supplied treatment planning system. A multileaf collimator system was recently introduced in the latest generation of system, capable of arbitrarily shaped treatment field. The purpose of this study is to develop a model based dose calculation algorithm to better handle the lateral scatter in an irregularly shaped small field for the CyberKnife system. A pencil beam dose calculation algorithm widely used in linac based treatment planning system was modified. The kernel parameters and intensity profile were systematically determined by fitting to the commissioning data. The model was tuned using only a subset of measured data (4 out of 12 cones) and applied to all fixed circular cones for evaluation. The root mean square (RMS) of the difference between the measured and calculated tissue-phantom-ratios (TPRs) and off-center-ratio (OCR) was compared. Three cone size correction techniques were developed to better fit the OCRs at the penumbra region, which are further evaluated by the output factors (OFs). The pencil beam model was further validated against measurement data on the variable dodecagon-shaped Iris collimators and a half-beam blocked field. Comparison with Ray-Tracing and Monte Carlo methods was also performed on a lung SBRT case. The RMS between the measured and calculated TPRs is 0.7% averaged for all cones, with the descending region at 0.5%. The RMSs of OCR at infield and outfield regions are both at 0.5%. The distance to agreement (DTA) at the OCR penumbra region is 0.2 mm. All three cone size correction models achieve the same improvement in OCR agreement, with the effective source shift model (SSM) preferred, due to their ability to predict more accurately the OF variations with the source to axis distance (SAD). In noncircular field validation, the pencil beam calculated

  20. Linear accelerator radiosurgery for vestibular schwannomas: Results of medium-term follow-up.

    PubMed

    Ellenbogen, Jonathan R; Waqar, Mueez; Kinshuck, Andrew J; Jenkinson, Michael D; Lesser, Tristram H J; Husband, David; Javadpour, Mohsen

    2015-01-01

    To examine tumour control, via volume changes, and the complications of linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) treatment of vestibular schwannomas (VSs) on medium-term follow-up. Between September 2003 and November 2009 fifty consecutive patients with VSs treated with SRS using a marginal dose of 12.5 Gy utilizing a LINAC equipped with a micro-multileaf collimator were identified. Evaluation included serial magnetic resonance imaging (MRI), and neurological and hearing examinations. The median tumour volume at treatment was 2.4 (range: 0.24-10.59) cm3. The intracranial diameter of the tumours ranged between 7.7 and 28.7 (median: 15.8) mm. Follow-up MRI was available for analysis on 49 patients. The median radiological follow-up period was 5.8 (range: 1.4-9.2) years. The median tumour volume at last follow-up was 1.1 (range: 0.03-5.3) cm3. VS decreased in size in 45 (90%) patients, with a median reduction in tumour volume of 1.46 (range: 0.06-9.29) cm3 or a median tumour size reduction of 59% of the baseline (range: 6-90%) in these patients. VS remained stable in 2 patients and increased in size in 2 patients. Only 1 patient (2%) required additional intervention (surgery). 15 patients had useful hearing pre-treatment; 10 post-treatment pure-tone audiograms of these patients were available. 5 (50%) patients still had useful hearing post treatment. Non-auditory adverse radiation effects included new (House-Brackmann grade II) or worsened facial nerve palsy (House-Brackmann grade II to grade V) in 2 (4%) patients and trigeminal sensory disturbance in 2 (4%) patients. At medium term, the vast majority of VSs treated with LINAC-based SRS exhibit tumour shrinkage. The slightly higher rate of facial nerve palsy compared with Gamma Knife surgery (GKS) results may be related to the learning curve. Other complications were similar to reported GKS results for VSs of comparable sizes.

  1. Electron and nuclear dynamics in many-electron atoms, molecules and chlorophyll-protein complexes: a review.

    PubMed

    Shuvalov, Vladimir A

    2007-06-01

    It has been shown [V.A. Shuvalov, Quantum dynamics of electrons in many-electron atoms of biologically important compounds, Biochemistry (Mosc.) 68 (2003) 1333-1354; V.A. Shuvalov, Quantum dynamics of electrons in atoms of biologically important molecules, Uspekhi biologicheskoi khimii, (Pushchino) 44 (2004) 79-108] that the orbit angular momentum L of each electron in many-electron atoms is L=mVr=nPlanck's and similar to L for one-electron atom suggested by N. Bohr. It has been found that for an atom with N electrons the total electron energy equation E=-(Z(eff))(2)e(4)m/(2n(2)Planck's(2)N) is more appropriate for energy calculation than standard quantum mechanical expressions. It means that the value of L of each electron is independent of the presence of other electrons in an atom and correlates well to the properties of virtual photons emitted by the nucleus and creating a trap for electrons. The energies for elements of the 1st up to the 5th rows and their ions (total amount 240) of Mendeleev' Periodical table were calculated consistent with the experimental data (deviations in average were 5 x 10(-3)). The obtained equations can be used for electron dynamics calculations in molecules. For H(2) and H(2)(+) the interference of electron-photon orbits between the atoms determines the distances between the nuclei which are in agreement with the experimental values. The formation of resonance electron-photon orbit in molecules with the conjugated bonds, including chlorophyll-like molecules, appears to form a resonance trap for an electron with E values close to experimental data. Two mechanisms were suggested for non-barrier primary charge separation in reaction centers (RCs) of photosynthetic bacteria and green plants by using the idea of electron-photon orbit interference between the two molecules. Both mechanisms are connected to formation of the exciplexes of chlorophyll-like molecules. The first one includes some nuclear motion before exciplex formation, the

  2. Device setting modifications for 3D flatpanel imaging in skull base surgery.

    PubMed

    Hassepass, Frederike; Maier, Wolfgang; Aschendorff, Antje; Bulla, Stefan; Vach, Werner; Laszig, Roland; Grauvogel, Tanja D

    2012-09-01

    To evaluate the image quality and clinical implementation after setting modification of a three-dimensional isocentric C-arm fluoroscopic image intensifier system combined with a digital flatpanel detector as a new tool for sinus and petrous bone surgery. Image acquisition was performed using two cadaveric heads. Experimental design was oriented to the clinically sensible intraoperative setup. Different tube currents and orbital movements of the C-arm system were evaluated for image quality by three otolaryngological surgeons using predetermined landmarks. Modification of the X-ray intensity did not attain statistically significant values compared to the X-ray-intensity predetermined by producer (12.0-18.5 mA, p > 0.05) for either sinus or for petrous bone scans. Elliptical orbital movement resulted in significantly superior image quality than data sets acquired by circular orbital movement (3.194 vs. 2.809, p < 0.0001). New C-arm systems with 3D-capabiltity offer a promising tool for intraoperative near real-time image guidance. Image quality of the skull base can be improved significantly with optimized system settings.

  3. Clinical introduction of a commercial treatment chair to facilitate thorax irradiation.

    PubMed

    Klein, E E; Wasserman, T; Ermer, B

    1995-01-01

    There are occasions when patients can benefit significantly from being treated upright. This technique is beneficial in the treatment of Hodgkin's disease when the mediastinum is involved. The main benefit is the lung volume spared resulting from narrowing of a bulky mediastinum. We purchased a commercial treatment chair to facilitate upright treatment. Clinical implementation required rigorous testing, documentation of procedures, and acknowledgment of and corresponding solutions to limitations. The purchased chair is designed to couple with the spine bar of the treatment couch, allowing patient positioning via pendant functions. The chair has no obstruction as immobilization is afforded by arm, shoulder, and knee supports, which allows isocentric treatments. An additional hydraulic mount is used for simulation. We have treated five patients thus far, including Hodgkin's disease patients with and without mediastinal involvement, and one lung cancer patient with a large lower lobe lesion. All patients have benefited by having a greater volume of lung spared (as much as 60% additional blocking) when upright simulation films are compared with supine and prone films. Immobilization has been adequate as confirmed by daily light field projections and portal films. We are routinely evaluating Hodgkin's disease patients for upright treatment. Patients treated in the chair have benefited in terms of lung volume spared without loss of immobilization. A patient with a large lower lobe lung lesion has also benefited as the tumor "dropped," thus affording lung sparing via blocking.

  4. Design and evaluation of a grid reciprocation scheme for use in digital breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Patel, Tushita; Sporkin, Helen; Peppard, Heather; Williams, Mark B.

    2016-03-01

    This work describes a methodology for efficient removal of scatter radiation during digital breast tomosynthesis (DBT). The goal of this approach is to enable grid image obscuration without a large increase in radiation dose by minimizing misalignment of the grid focal point (GFP) and x-ray focal spot (XFS) during grid reciprocation. Hardware for the motion scheme was built and tested on the dual modality breast tomosynthesis (DMT) scanner, which combines DBT and molecular breast tomosynthesis (MBT) on a single gantry. The DMT scanner uses fully isocentric rotation of tube and x-ray detector for maintaining a fixed tube-detector alignment during DBT imaging. A cellular focused copper prototype grid with 80 cm focal length, 3.85 mm height, 0.1 mm thick lamellae, and 1.1 mm hole pitch was tested. Primary transmission of the grid at 28 kV tube voltage was on average 74% with the grid stationary and aligned for maximum transmission. It fell to 72% during grid reciprocation by the proposed method. Residual grid line artifacts (GLAs) in projection views and reconstructed DBT images are characterized and methods for reducing the visibility of GLAs in the reconstructed volume through projection image flat-field correction and spatial frequency-based filtering of the DBT slices are described and evaluated. The software correction methods reduce the visibility of these artifacts in the reconstructed volume, making them imperceptible both in the reconstructed DBT images and their Fourier transforms.

  5. Treatment experience with 15 MeV fast neutrons in the oral cavity and oropharynx

    SciTech Connect

    Herskovic, A.; Cox, E.B.; Fender, F.; Schell, M.; Henshaw, W.; Rogers, C.; Ornitz, R.

    1984-05-15

    All 86 patients with squamous cell carcinoma of the oral cavity and oropharynx treated with fast neutrons at the Mid-Atlantic Neutron Therapy facility at the Naval Research Laboratory (MANTA) from its inception in 1976 until closing in 1979, are reported. Patients generally had advanced disease or have failed or were failing conventional treatment prior to being treated at MANTA. The fixed horizontal beam parameters were suboptimal. Patients were treated by either neutrons alone or various combinations of neutrons and photons. In patients with T3 or T4 primary carcinomas treated with less than 2100 neutron rad, only 37% (3/11) had a complete response at the primary compared to 57% (24/42) treated to a higher dose. However, there was a significant evidence of radiation related complication. The latter was expected in a phase I/II trial of a new modality such as fast neutrons. Isocentric hospital based cyclotrons should offer some hope of improvement in the future.

  6. Clinical Applications of Geometrical Field Matching in Radiotherapy Based on a New Analytical Solution

    SciTech Connect

    Hernandez, Victor; Arenas, Meritxell; Pons, Ferran; Sempau, Josep

    2011-07-01

    A new analytical formalism has been published recently that provides all the parameters necessary for geometrical field matching in radiotherapy. The present work applies the general expressions for craniospinal irradiation, breast irradiation with a supraclavicular half-field, and breast irradiation with a supraclavicular full-field. We also explore the formalism as a tool to analyze and compare different techniques. Field matching is achieved by imposing both parallelism and coincidence between the side planes of adjacent fields. The rotation angles and either the field aperture for a certain isocenter position or the isocenter coordinates for a given field aperture are supplied. All of the already known exact solutions are reproduced. New expressions for the field aperture and for the isocenter coordinates, which were not previously available, are also computed. If tangential fields at a fixed source-to-skin distance are used together with a supraclavicular full-field, different apertures for each tangential field are required to achieve a correct match. If an isocentric technique for the tangential fields or a supraclavicular half-field is used, this complication is avoided. The breast technique with the supraclavicular half-field is recommended, because it presents several advantages with respect to the supraclavicular full-field. This formalism provides a useful tool in cases where matching of adjacent fields is necessary.

  7. An improved Monte Carlo (MC) dose simulation for charged particle cancer therapy

    SciTech Connect

    Ying, C. K.; Kamil, W. A.; Shuaib, I. L.; Matsufuji, Naruhiro

    2014-02-12

    Heavy-particle therapy such as carbon ion therapy are more popular nowadays because of the nature characteristics of charged particle and almost no side effect to patients. An effective treatment is achieved with high precision of dose calculation, in this research work, Geant4 based Monte Carlo simulation method has been used to calculate the radiation transport and dose distribution. The simulation have the same setting with the treatment room in Heavy Ion Medical Accelerator, HIMAC. The carbon ion beam at the isocentric gantry nozzle for the therapeutic energy of 290 MeV/u was simulated, experimental work was carried out in National Institute of Radiological Sciences, NIRS, Chiba, Japan by using the HIMAC to confirm the accuracy and qualities dose distribution by MC methods. The Geant4 based simulated dose distribution were verified with measurements for Bragg peak and spread out Bragg peak (SOBP) respectively. The verification of results shows that the Bragg peak depth-dose and SOBP distributions in simulation has good agreement with measurements. In overall, the study showed that Geant4 based can be fully applied in the heavy-ion therapy field for simulation, further works need to be carry on to refine and improve the Geant4 MC simulations.

  8. NOTE: Optimization of megavoltage CT scan registration settings for brain cancer treatments on tomotherapy

    NASA Astrophysics Data System (ADS)

    Woodford, Curtis; Yartsev, Slav; Van Dyk, Jake

    2007-04-01

    This study aims to determine the settings that provide the optimal clinical accuracy and consistency for the registration of megavoltage CT (MVCT) with planning kilovoltage CT image sets on the Hi-ART tomotherapy system. The systematic offset between the MVCT and the planning kVCT was determined by registration of multiple MVCT scans of a head phantom aligned with the planning isocentre. Residual error vector lengths and components were used to quantify the alignment quality for the phantom shifted by 5 mm in different directions obtained by all 27 possible combinations of MVCT inter-slice spacing, registration techniques and resolution. MVCT scans with normal slices are superior to coarse slices for registration of shifts in the superior-inferior, lateral and anterior-posterior directions. Decreasing the scan length has no detrimental effect on registration accuracy as long as the scan lengths are larger than 24 mm. In the case of bone technique and fine resolution, normal and fine MVCT scan slice spacing options give similar accuracy, so normal mode is preferable due to shorter procedure and less delivered dose required for patient set-up. A superior-inferior field length of 24-30 mm, normal slice spacing, bone technique, and fine resolution is the optimum set of registration settings for MVCT scans of a Rando head phantom acquired with the Hi-ART tomotherapy system, provided the registration shifts are less than 5 mm.

  9. Geant4 studies of the CNAO facility system for hadrontherapy treatment of uveal melanomas

    NASA Astrophysics Data System (ADS)

    Rimoldi, A.; Piersimoni, P.; Pirola, M.; Riccardi, C.

    2014-06-01

    The Italian National Centre of Hadrontherapy for Cancer Treatment (CNAO -Centro Nazionale di Adroterapia Oncologica) in Pavia, Italy, has started the treatment of selected cancers with the first patients in late 2011. In the coming months at CNAO plans are to activate a new dedicated treatment line for irradiation of uveal melanomas using the available active beam scan. The beam characteristics and the experimental setup should be tuned in order to reach the necessary precision required for such treatments. Collaboration between CNAO foundation, University of Pavia and INFN has started in 2011 to study the feasibility of these specialised treatments by implementing a MC simulation of the transport beam line and comparing the obtained simulation results with measurements at CNAO. The goal is to optimise an eye-dedicated transport beam line and to find the best conditions for ocular melanoma irradiations. This paper describes the Geant4 toolkit simulation of the CNAO setup as well as a modelised human eye with a tumour inside. The Geant4 application could be also used to test possible treatment planning systems. Simulation results illustrate the possibility to adapt the CNAO standard transport beam line by optimising the position of the isocentre and the addition of some passive elements to better shape the beam for this dedicated study.

  10. Comprehensive quality assurance for stereotactic radiosurgery treatments.

    PubMed

    Ramaseshan, R; Heydarian, M

    2003-07-21

    We have used a commercially available high precision Lucy phantom to perform comprehensive quality assurance for stereotactic radiosurgery treatments. The quantitative evaluation of system uncertainties included imaging, planning and treatment delivery systems. The quality assurance tests showed that the well-defined targets were identified to within +/-1 mm in all the imaging modalities. The pre-known target volumes were reproduced within 2 cm3 in both MR and CT. The planned target was delivered within 2% of the prescribed dose and to within 2 mm accuracy. The inaccuracy in the isocentre position at the Linac was less than 1.2 mm. The maximum error observed in the depth helmet was 0.5 mm and the overall uncertainty was within 0.23 mm. We have also established a quality assurance program based on the study and proposed the tolerance and the frequency of the tests required to be carried out. The tests were carried out using a Radionics planning system and delivered on a Varian Clinac 2100 linear accelerator machine. These tests also established a base line for future comparisons.

  11. Investigation of X-ray focal spot alignment using a jig of novel design.

    PubMed

    Yuen, Lockie; McLucas, Cameron

    2017-06-01

    The X-ray focal spot and the centre of the flattening filter should be placed as close as possible to the central axis (CAX) on a linear accelerator (linac) to produce a radially symmetric beam. The aim of this study is to devise a method to easily optimise the focal spot position of Varian linac photon beams generated with a flattening filter. A simple and robust jig was designed and built to be inserted into the largest electron applicator. Accessory and jaw position interlocks were overridden to enable photon beam operation. The jig was made from aluminium and consists of a plate permanently fixed inside a low melting point alloy (LMPA) insert frame and a block machined to suspend an ion chamber below the plate, such that the axis of the chamber is at the linac isocentre. The jig was used to optimise the position of the X-ray beam focal spot with respect to the device central axis (CAX). This was achieved by minimising the percentage change in ionisation chamber signal between collimator rotations from 90° to 270° as position steering was changed. As part of the investigation, in-plane (radial) and cross-plane (transverse) profiles obtained from water phantom scans were used to quantify how large the percentage ionisation change can be before profiles are distorted in the region of the CAX.

  12. Estimation of organs doses and radiation-induced secondary cancer risk from scattered photons for conventional radiation therapy of nasopharynx: a Monte Carlo study.

    PubMed

    Mesbahi, Asghar; Seyednejad, Farshad; Gasemi-Jangjoo, Amir

    2010-06-01

    We used Monte Carlo modeling to calculate the organs doses due to out-of field photons during radiation therapy of the nasopharynx. A medical internal radiation dose (MIRD)-based mathematical phantom resembling an adult man was modeled by MCNP4C MC code. Three validated models of a cobalt-60 machine, a 6-MV photon beam of a Varian 2300 C/D linac, and a 9-MV photon beam of a Neptun linac were used to simulate the isocentric irradiation of a mathematical phantom with two lateral fields of the nasopharynx. The organspecific dose, effective dose, and cancer risk estimates were obtained. The effective doses for out-of-field radiation were 320, 295, and 248 mSv for the (60)Co beam, 6-MV beam, and 9-MV beam devices, respectively, for a 70-Gy tumor dose. The fatal cancer risks of 1.6%, 1.5%, and 1.2% were estimated for a 70-Gy tumor dose of (60)Co and the 6- and 9-MV photon beams, respectively. Our results regarding the effective dose and cancer risk are in agreement with previously published experimental results on conventional radiation therapy. Further investigation on patients' out-of-field dose to provide more knowledge on various radiotherapy techniques is suggested.

  13. Evaluation of mechanical and geometric accuracy of two different image guidance systems in radiotherapy.

    PubMed

    Kanakavelu, Nithya; Ravindran, Anand Mambakam; Samuel, Emmanvelrajan James Jebaseelan

    2016-01-01

    To assess the mechanical and the geometric accuracy of two different clinically used image guidance systems in radiotherapy for a period of 6 months. With the image guidance procedures being routine in the clinical radiotherapy department, the quality assurance tests for these systems become essential. The mechanical and geometric accuracy of these systems are crucial since it directly affects patient treatment set-up and delivery. We have assessed the mechanical and the geometric accuracy of two different image guidance systems (MV and kV based), being used clinically for a period of 6 months. The quality assurance tests such as imager positioning/repositioning, imaging and treatment beam isocentre coincidence, imager mechanical alignment, image scaling, geometric accuracy of cone beam computed tomography system, automatic image registration and offset calculation accuracy were assessed in this period. It was found that both systems were mechanically and geometrically accurate within ±2 mm in this period. The quality assurance tests for MV based image guidance system were simple compared to kV based systems. We recommend performing periodic quality assurance tests to verify the integrity of both image guidance systems.

  14. Field size dependent mapping of medical linear accelerator radiation leakage

    NASA Astrophysics Data System (ADS)

    Vũ Bezin, Jérémi; Veres, Attila; Lefkopoulos, Dimitri; Chavaudra, Jean; Deutsch, Eric; de Vathaire, Florent; Diallo, Ibrahima

    2015-03-01

    The purpose of this study was to investigate the suitability of a graphics library based model for the assessment of linear accelerator radiation leakage. Transmission through the shielding elements was evaluated using the build-up factor corrected exponential attenuation law and the contribution from the electron guide was estimated using the approximation of a linear isotropic radioactive source. Model parameters were estimated by a fitting series of thermoluminescent dosimeter leakage measurements, achieved up to 100 cm from the beam central axis along three directions. The distribution of leakage data at the patient plane reflected the architecture of the shielding elements. Thus, the maximum leakage dose was found under the collimator when only one jaw shielded the primary beam and was about 0.08% of the dose at isocentre. Overall, we observe that the main contributor to leakage dose according to our model was the electron beam guide. Concerning the discrepancies between the measurements used to calibrate the model and the calculations from the model, the average difference was about 7%. Finally, graphics library modelling is a readily and suitable way to estimate leakage dose distribution on a personal computer. Such data could be useful for dosimetric evaluations in late effect studies.

  15. Tolerance doses of cutaneous and mucosal tissues in ring-necked parakeets (Psittacula krameri) for external beam megavoltage radiation.

    PubMed

    Barron, Heather W; Roberts, Royce E; Latimer, Kenneth S; Hernandez-Divers, Stephen; Northrup, Nicole C

    2009-03-01

    Currently used dosages for external-beam megavoltage radiation therapy in birds have been extrapolated from mammalian patients and often appear to provide inadequate doses of radiation for effective tumor control. To determine the tolerance doses of cutaneous and mucosal tissues of normal birds in order to provide more effective radiation treatment for tumors that have been shown to be radiation responsive in other species, ingluvial mucosa and the skin over the ingluvies of 9 ring-necked parakeets (Psittacula krameri) were irradiated in 4-Gy fractions to a total dose of either 48, 60, or 72 Gy using an isocentric cobalt-60 teletherapy unit. Minimal radiation-induced epidermal changes were present in the high-dose group histologically. Neither dose-related acute nor chronic radiation effects could be detected in any group grossly in cutaneous or mucosal tissue over a 9-month period. Radiation doses of 72 Gy in 4-Gy fractions were well tolerated in the small number of ring-necked parakeets in this initial tolerance dose study.

  16. Poster — Thur Eve — 30: 4D VMAT dose calculation methodology to investigate the interplay effect: experimental validation using TrueBeam Developer Mode and Gafchromic film

    SciTech Connect

    Teke, T; Milette, MP; Huang, V; Thomas, SD

    2014-08-15

    The interplay effect between the tumor motion and the radiation beam modulation during a VMAT treatment delivery alters the delivered dose distribution from the planned one. This work present and validate a method to accurately calculate the dose distribution in 4D taking into account the tumor motion, the field modulation and the treatment starting phase. A QUASAR™ respiratory motion phantom was 4D scanned with motion amplitude of 3 cm and with a 3 second period. A static scan was also acquired with the lung insert and the tumor contained in it centered. A VMAT plan with a 6XFFF beam was created on the averaged CT and delivered on a Varian TrueBeam and the trajectory log file was saved. From the trajectory log file 10 VMAT plans (one for each breathing phase) and a developer mode XML file were created. For the 10 VMAT plans, the tumor motion was modeled by moving the isocentre on the static scan, the plans were re-calculated and summed in the treatment planning system. In the developer mode, the tumor motion was simulated by moving the couch dynamically during the treatment. Gafchromic films were placed in the QUASAR phantom static and irradiated using the developer mode. Different treatment starting phase were investigated (no phase shift, maximum inhalation and maximum exhalation). Calculated and measured isodose lines and profiles are in very good agreement. For each starting phase, the dose distribution exhibit significant differences but are accurately calculated with the methodology presented in this work.

  17. Spontaneous haemorrhage into metastatic brain tumours after stereotactic radiosurgery using a linear accelerator

    PubMed Central

    Suzuki, H; Toyoda, S; Muramatsu, M; Shimizu, T; Kojima, T; Taki, W

    2003-01-01

    Objective: To determine the incidence and clinical characteristics of spontaneous haemorrhage into metastatic brain tumours after radiosurgery. Methods: Intratumour haemorrhage rate, clinical features, and treatment were evaluated in 54 patients with 131 brain metastases of varying origin who were treated using linear accelerator radiosurgery. The marginal dose was maintained constant at 20 or 25 Gy, irrespective of tumour size. Results: Haemorrhage was identified in 7.4% of the metastases (five tumours in four patients) before radiosurgery and in 18.5% (10 tumours in 10 patients) after radiosurgery. In three cases, haemorrhage into the tumour after radiosurgery was symptomatic. Half the haemorrhages occurred within one month of radiosurgery. The changes in tumour size observed at the time of haemorrhage were an increase in one tumour, no change in five, and a decrease in four. Haemorrhage into a tumour after radiosurgery was more likely to occur in female patients, in tumours with a larger volume on pretreatment neuroimaging, and in tumours treated with a larger number of isocentres or a higher maximum dose. Haemorrhagic features in the patients or their tumours on presurgical assessment were not disposing factors to haemorrhage after radiosurgery. Conclusions: When larger brain metastases are aggressively treated by radiosurgery, better local control may be attained but there may also be a higher risk of haemorrhage soon after the treatment. PMID:12810777

  18. Development and Clinical Implementation of a Universal Bolus to Maintain Spot Size During Delivery of Base of Skull Pencil Beam Scanning Proton Therapy

    SciTech Connect

    Both, Stefan; Shen, Jiajian; Kirk, Maura; Lin, Liyong; Tang, Shikui; Alonso-Basanta, Michelle; Lustig, Robert; Lin, Haibo; Deville, Curtiland; Hill-Kayser, Christine; Tochner, Zelig; McDonough, James

    2014-09-01

    Purpose: To report on a universal bolus (UB) designed to replace the range shifter (RS); the UB allows the treatment of shallow tumors while keeping the pencil beam scanning (PBS) spot size small. Methods and Materials: Ten patients with brain cancers treated from 2010 to 2011 were planned using the PBS technique with bolus and the RS. In-air spot sizes of the pencil beam were measured and compared for 4 conditions (open field, with RS, and with UB at 2- and 8-cm air gap) in isocentric geometry. The UB was applied in our clinic to treat brain tumors, and the plans with UB were compared with the plans with RS. Results: A UB of 5.5 cm water equivalent thickness was found to meet the needs of the majority of patients. By using the UB, the PBS spot sizes are similar with the open beam (P>.1). The heterogeneity index was found to be approximately 10% lower for the UB plans than for the RS plans. The coverage for plans with UB is more conformal than for plans with RS; the largest increase in sparing is usually for peripheral organs at risk. Conclusions: The integrity of the physical properties of the PBS beam can be maintained using a UB that allows for highly conformal PBS treatment design, even in a simple geometry of the fixed beam line when noncoplanar beams are used.

  19. The efficiency of orthotic interventions on energy consumption in paraplegic patients: a literature review.

    PubMed

    Arazpour, M; Samadian, M; Bahramizadeh, M; Joghtaei, M; Maleki, M; Ahmadi Bani, M; Hutchins, S W

    2015-01-20

    Study design:This is a systematic literature review.Objectives:Different types of orthoses have been developed to enable and facilitate ambulation in individuals with paraplegia. However, their effect on energy consumption while ambulating is not clear. The objective of this review was to compare the energy expenditure required to walk with these devices.Methods:Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method, and based on selected keywords and their composition according to the Population Intervention Comparison Outcome (PICO) method, a search was performed in Science Direct, Google Scholar, Scopus, Web of Knowledge and PubMed databases. The searches were restricted to papers published in the English language and were conducted during February 2014; the last access to the database was on 25 February 2014. A total of 24 articles were chosen for final evaluation.Results:Hybrid orthoses reduce energy consumption compared with mechanical orthoses when used for walking by paraplegic patients. The isocentric reciprocating gait orthosis has been shown to be more effective than other reciprocating orthoses in reducing energy consumption. Energy consumption when walking with powered orthoses (PO) and hybrid orthoses was also reduced compared with when walking with conventional orthoses.Conclusions:The hybrid orthoses and PO could be effective alternatives in rehabilitation for spinal cord injury patients to help improve the energy consumption.Spinal Cord advance online publication, 20 January 2015; doi:10.1038/sc.2014.227.

  20. Treatment planning and delivery of involved field radiotherapy in advanced Hodgkin's disease: results from a questionnaire-based audit for the UK Stanford V regimen vs ABVD clinical trial quality assurance programme (ISRCTN 64141244).

    PubMed

    Diez, P; Hoskin, P J; Aird, E G A

    2007-10-01

    This questionnaire forms the basis of the quality assurance (QA) programme for the UK randomized Phase III study of the Stanford V regimen versus ABVD for treatment of advanced Hodgkin's disease to assess differences between participating centres in treatment planning and delivery of involved-field radiotherapy for Hodgkin's lymphoma The questionnaire, which was circulated amongst 42 participating centres, consisted of seven sections: target volume definition and dose prescription; critical structures; patient positioning and irradiation techniques; planning; dose calculation; verification; and future developments The results are based on 25 responses. One-third plan using CT alone, one-third use solely the simulator and the rest individualize, depending on disease site. Eleven centres determine a dose distribution for each patient. Technique depends on disease site and whether CT or simulator planning is employed. Most departments apply isocentric techniques and use immobilization and customized shielding. In vivo dosimetry is performed in 7 centres and treatment verification occurs in 24 hospitals. In conclusion, the planning and delivery of treatment for lymphoma patients varies across the country. Conventional planning is still widespread but most centres are moving to CT-based planning and virtual simulation with extended use of immobilization, customized shielding and compensation.

  1. Recent progress of a superconducting rotating-gantry for carbon-ion radiotherapy

    NASA Astrophysics Data System (ADS)

    Iwata, Y.; Fujimoto, T.; Matsuba, S.; Fujita, T.; Sato, S.; Furukawa, T.; Hara, Y.; Mizushima, K.; Saraya, Y.; Tansho, R.; Saotome, N.; Shirai, T.; Noda, K.

    2017-09-01

    A superconducting rotating-gantry for carbon-ion radiotherapy was developed. This isocentric rotating gantry can transport carbon ions having the maximum kinetic energy of E = 430 MeV/u to an isocenter with irradiation angles of over ±180°, and is further capable of performing three-dimensional raster-scanning irradiation. By using combined-function superconducting magnets, we could design a compact rotating gantry for carbon-ion radiotherapy. Construction of the gantry structure began since early 2014, and the installation of the entire gantry system to the Heavy Ion Medical Accelerator in Chiba (HIMAC) complex was completed by the end of September, 2015. Beam tuning subsequently began since October, 2015, and carbon ions, as accelerated by the HIMAC upper synchrotron, having kinetic energies of between E = 430-48 MeV/u were successfully transported with the rotating gantry to the isocenter. The size and shape of the beam spots at the isocenter is being tuned over various combinations of the beam energies and the gantry angle. We will present the recent progress as well as the current status of the superconducting rotating-gantry.

  2. Characterization of electron contamination in megavoltage photon beams

    SciTech Connect

    Medina, Antonio Lopez; Teijeiro, Antonio; Garcia, Juan; Esperon, Jorge; Terron, J. Antonio; Ruiz, Diego P.; Carrion, Maria C.

    2005-05-01

    The purpose of the present study is to characterize electron contamination in photon beams in different clinical situations. Variations with field size, beam modifier (tray, shaping block) and source-surface distance (SSD) were studied. Percentage depth dose measurements with and without a purging magnet and replacing the air by helium were performed to identify the two electron sources that are clearly differentiated: air and treatment head. Previous analytical methods were used to fit the measured data, exploring the validity of these models. Electrons generated in the treatment head are more energetic and more important for larger field sizes, shorter SSD, and greater depths. This difference is much more noticeable for the 18 MV beam than for the 6 MV beam. If a tray is used as beam modifier, electron contamination increases, but the energy of these electrons is similar to that of electrons coming from the treatment head. Electron contamination could be fitted to a modified exponential curve. For machine modeling in a treatment planning system, setting SSD at 90 cm for input data could reduce errors for most isocentric treatments, because they will be delivered for SSD ranging from 80 to 100 cm. For very small field sizes, air-generated electrons must be considered independently, because of their different energetic spectrum and dosimetric influence.

  3. A technology platform for translational research on laser driven particle accelerators for radiotherapy

    NASA Astrophysics Data System (ADS)

    Enghardt, W.; Bussmann, M.; Cowan, T.; Fiedler, F.; Kaluza, M.; Pawelke, J.; Schramm, U.; Sauerbrey, R.; Tünnermann, A.; Baumann, M.

    2011-05-01

    It is widely accepted that proton or light ion beams may have a high potential for improving cancer cure by means of radiation therapy. However, at present the large dimensions of electromagnetic accelerators prevent particle therapy from being clinically introduced on a broad scale. Therefore, several technological approaches among them laser driven particle acceleration are under investigation. Parallel to the development of suitable high intensity lasers, research is necessary to transfer laser accelerated particle beams to radiotherapy, since the relevant parameters of laser driven particle beams dramatically differ from those of beams delivered by conventional accelerators: The duty cycle is low, whereas the number of particles and thus the dose rate per pulse are high. Laser accelerated particle beams show a broad energy spectrum and substantial intensity fluctuations from pulse to pulse. These properties may influence the biological efficiency and they require completely new techniques of beam delivery and quality assurance. For this translational research a new facility is currently constructed on the campus of the university hospital Dresden. It will be connected to the department of radiooncology and host a petawatt laser system delivering an experimental proton beam and a conventional therapeutic proton cyclotron. The cyclotron beam will be delivered on the one hand to an isocentric gantry for patient treatments and on the other hand to an experimental irradiation site. This way the conventional accelerator will deliver a reference beam for all steps of developing the laser based technology towards clinical applicability.

  4. Compact multileaf collimator for conformal and intensity modulated fast neutron therapy: Electromechanical design and validation

    SciTech Connect

    Farr, J. B.; Maughan, R. L.; Yudelev, M.; Blosser, E.; Brandon, J.; Horste, T.; Forman, J. D.

    2006-09-15

    The electromechanical properties of a 120-leaf, high-resolution, computer-controlled, fast neutron multileaf collimator (MLC) are presented. The MLC replaces an aging, manually operated multirod collimator. The MLC leaves project 5 mm in the isocentric plane perpendicular to the beam axis. A taper is included on the leaves matching beam divergence along one axis. The 5-mm leaf projection width is chosen to give high-resolution conformality across the entire field. The maximum field size provided is 30x30 cm{sup 2}. To reduce the interleaf transmission a 0.254-mm blocking step is included. End-leaf steps totaling 0.762 mm are also provided allowing opposing leaves to close off within the primary radiation beam. The neutron MLC also includes individual 45 deg. and 60 deg. automated universal tungsten wedges. The automated high-resolution neutron collimation provides an increase in patient throughput capacity, enables a new modality, intensity modulated neutron therapy, and limits occupational radiation exposure by providing remote operation from a shielded console area.

  5. Measurement of inter and intra fraction organ motion in radiotherapy using cone beam CT projection images

    NASA Astrophysics Data System (ADS)

    Marchant, T. E.; Amer, A. M.; Moore, C. J.

    2008-02-01

    A method is presented for extraction of intra and inter fraction motion of seeds/markers within the patient from cone beam CT (CBCT) projection images. The position of the marker is determined on each projection image and fitted to a function describing the projection of a fixed point onto the imaging panel at different gantry angles. The fitted parameters provide the mean marker position with respect to the isocentre. Differences between the theoretical function and the actual projected marker positions are used to estimate the range of intra fraction motion and the principal motion axis in the transverse plane. The method was validated using CBCT projection images of a static marker at known locations and of a marker moving with known amplitude. The mean difference between actual and measured motion range was less than 1 mm in all directions, although errors of up to 5 mm were observed when large amplitude motion was present in an orthogonal direction. In these cases it was possible to calculate the range of motion magnitudes consistent with the observed marker trajectory. The method was shown to be feasible using clinical CBCT projections of a pancreas cancer patient.

  6. Numerical study of remote detection outside the magnet with travelling wave Magnetic Resonance Imaging at 3T

    NASA Astrophysics Data System (ADS)

    López, M.; Vázquez, F.; Solís-Nájera, S.; Rodriguez, A. O.

    2015-01-01

    The use of the travelling wave approach for high magnetic field magnetic resonance imaging has been used recently with very promising results. This approach offer images one with greater field-of-view and a reasonable signal-to-noise ratio using a circular waveguide. This scheme has been proved to be successful at 7 T and 9.4 T with whole-body imager. Images have also been acquired with clinical magnetic resonance imaging systems whose resonant frequencies were 64 MHz and 128 MHz. These results motivated the use of remote detection of the magnetic resonance signal using a parallel-plate waveguide together with 3 T clinical scanners, to acquired human leg images. The cut-off frequency of this waveguide is zero for the principal mode, allowing us to overcome the barrier of transmitting waves at lower frequency than 300 MHz or 7 T for protons. These motivated the study of remote detection outside the actual magnet. We performed electromagnetic field simulations of a parallel-plate waveguide and a phantom. The signal transmission was done at 128 MHz and using a circular surface coil located almost 200 cm away for the magnet isocentre. Numerical simulations demonstrated that the magnetic field of the principal mode propagate inside a waveguide outside the magnet. Numerical results were compared with previous experimental-acquired image data under similar conditions.

  7. Design of a superconducting rotating gantry for heavy-ion therapy

    NASA Astrophysics Data System (ADS)

    Iwata, Y.; Noda, K.; Shirai, T.; Murakami, T.; Furukawa, T.; Mori, S.; Fujita, T.; Itano, A.; Shouda, K.; Mizushima, K.; Fujimoto, T.; Ogitsu, T.; Obana, T.; Amemiya, N.; Orikasa, T.; Takami, S.; Takayama, S.; Watanabe, I.

    2012-04-01

    A superconducting rotating gantry for heavy-ion therapy is being designed. This isocentric rotating gantry can transport heavy ions with the maximum energy of 430MeV/u to an isocenter with irradiation angles of over 0-360 degrees, and is further capable of performing three-dimensional raster-scanning irradiation. The combined-function superconducting magnets will be employed for the rotating gantry. The superconducting magnets with optimized beam optics allow a compact gantry design with a large scan size at the isocenter; the length and the radius of the gantry will be approximately 13 and 5.5 m, respectively, which are comparable to those for the existing proton gantries. Furthermore, the maximum scan size at the isocenter is calculated to be as large as approximately 200 mm square for heavy-ion beams at the maximum energy of 430MeV/u. Based on the design of the beam optics, specifications of the superconducting magnets were determined. The superconducting magnets and magnetic-field distributions are designed using a three-dimensional field solver. With the calculated magnetic fields, beam-tracking simulations were performed to verify the design of the superconducting magnets, and concurrently to evaluate the field quality. With calculated beam profiles at the isocenter, we found that the positions of beam spots as well as their size and shape could be well reproduced as designed, proving validity of our design.

  8. Evaluation of spatial-encoding-related geometric distortion in magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Hong, Cheol Pyo; Lee, Dong Hoon; Lee, Man Woo; Woo, Youngkeun

    2012-12-01

    This study demonstrated the characteristics of spatial encoding-related geometric distortion in magnetic resonance imaging (MRI) by using a phantom with known physical dimensions to detect geometric distortion in MR scans. The amount of distortion was calculated as the difference between the physical coordinates of control points in the phantom and those of the corresponding points in the distorted MR image of the phantom. The phase and the frequency encoding directions were swapped to acquire a phantom image for movement of a patient table 120 mm to the right and left, allowing comprehensive distortion mapping over the isocentric plane and the entire field of view (FOV) along the spatial encoding. The geometric distortion of phase encoding directions over the entire FOV was small compared to the distortion of frequency encoding directions. The maximum absolute deviations were 28.00 mm and 20.00 mm along the frequency and the phase encoding directions over the entire FOV, respectively. The mean absolute deviations along the frequency and the phase encoding directions were 2.85 mm and 1.97 mm, respectively. Although geometric distortion along the phase encoding axis near the isocenter was small, the distortion increased slightly toward the peripheral regions. The distortion of the phase encoding direction in the peripheral region can be severely affected by the imaging gradient's nonlinearity.

  9. Development of a superconducting rotating-gantry for heavy-ion therapy

    NASA Astrophysics Data System (ADS)

    Iwata, Y.; Noda, K.; Murakami, T.; Shirai, T.; Furukawa, T.; Fujita, T.; Mori, S.; Mizushima, K.; Shouda, K.; Fujimoto, T.; Ogitsu, T.; Obana, T.; Amemiya, N.; Orikasa, T.; Takami, S.; Takayama, S.

    2013-12-01

    An isocentric superconducting rotating-gantry for heavy-ion therapy is being developed. This rotating gantry can transport heavy ions having 430 MeV/u to an isocenter with irradiation angles of over ±180°, and is further capable of performing fast raster-scanning irradiation. For the magnets, combined-function superconducting-magnets are to be employed. All of the superconducting magnets have been designed, and their magnetic-field distributions were calculated by using a 3D electromagnetic-field solver. With the calculated magnetic-fields, beam-tracking simulations were performed to evaluate the field quality of the superconducting magnets. Beam profiles as well as phase-space distributions at the isocenter, as calculated by simulations, agreed well with those of linear beam-optics calculations, proving validity of the final design for the magnets. Three superconducting magnets were manufactured, and are being tested. In this paper, results of tracking simulations as well as test results for the superconducting magnets are presented.

  10. Impact of patient rotational errors on target and critical structure dose in IMRT: A 3D simulation study

    NASA Astrophysics Data System (ADS)

    Arumugam, S.; Xing, A.; Vial, P.; Scotti, A.; Stirton, R.; Goozee, G.; Holloway, Lois

    2013-06-01

    The impact of 3D rotational errors in patient positioning on dose delivered target volumes and critical structures in IMRT was studied. Patient rotational errors ranging from -30 to +30 was introduced to IMRT treatment plans of pelvis, head and neck and brain treatment sites and the impact of rotational error on DVH metrics was assessed. The magnitude of impact of rotational error on the error in dose delivered to the target volume and critical structures depends on the location of the structures from plan isocentre. In studied plans, a maximum percentage difference of up to -9.8(1s=13.4) % in D95 to PTV was observed for head and neck treatments. Similarly, in Brain treatments a maximum difference of up to 24.0(1s=33.0) % in maximum dose of Optic chiasm was observed. The results suggest that failure to correct patient's rotational error results in under-dosage to target volumes and over-dosage to the critical structures in some specific treatment scenarios.

  11. Design and evaluation of a grid reciprocation scheme for use in digital breast tomosynthesis.

    PubMed

    Patel, Tushita; Sporkin, Helen; Peppard, Heather; Williams, Mark B

    2016-02-27

    This work describes a methodology for efficient removal of scatter radiation during digital breast tomosynthesis (DBT). The goal of this approach is to enable grid image obscuration without a large increase in radiation dose by minimizing misalignment of the grid focal point (GFP) and x-ray focal spot (XFS) during grid reciprocation. Hardware for the motion scheme was built and tested on the dual modality breast tomosynthesis (DMT) scanner, which combines DBT and molecular breast tomosynthesis (MBT) on a single gantry. The DMT scanner uses fully isocentric rotation of tube and x-ray detector for maintaining a fixed tube-detector alignment during DBT imaging. A cellular focused copper prototype grid with 80 cm focal length, 3.85 mm height, 0.1 mm thick lamellae, and 1.1 mm hole pitch was tested. Primary transmission of the grid at 28 kV tube voltage was on average 74% with the grid stationary and aligned for maximum transmission. It fell to 72% during grid reciprocation by the proposed method. Residual grid line artifacts (GLAs) in projection views and reconstructed DBT images are characterized and methods for reducing the visibility of GLAs in the reconstructed volume through projection image flat-field correction and spatial frequency-based filtering of the DBT slices are described and evaluated. The software correction methods reduce the visibility of these artifacts in the reconstructed volume, making them imperceptible both in the reconstructed DBT images and their Fourier transforms.

  12. Characterization of electron contamination in megavoltage photon beams.

    PubMed

    Lopez Medina, Antonio; Teijeiro, Antonio; Garcia, Juan; Esperon, Jorge; Terron, J Antonio; Ruiz, Diego P; Carrion, Maria C

    2005-05-01

    The purpose of the present study is to characterize electron contamination in photon beams in different clinical situations. Variations with field size, beam modifier (tray, shaping block) and source-surface distance (SSD) were studied. Percentage depth dose measurements with and without a purging magnet and replacing the air by helium were performed to identify the two electron sources that are clearly differentiated: air and treatment head. Previous analytical methods were used to fit the measured data, exploring the validity of these models. Electrons generated in the treatment head are more energetic and more important for larger field sizes, shorter SSD, and greater depths. This difference is much more noticeable for the 18 MV beam than for the 6 MV beam. If a tray is used as beam modifier, electron contamination increases, but the energy of these electrons is similar to that of electrons coming from the treatment head. Electron contamination could be fitted to a modified exponential curve. For machine modeling in a treatment planning system, setting SSD at 90 cm for input data could reduce errors for most isocentric treatments, because they will be delivered for SSD ranging from 80 to 100 cm. For very small field sizes, air-generated electrons must be considered independently, because of their different energetic spectrum and dosimetric influence.

  13. A small animal image guided irradiation system study using 3D dosimeters

    NASA Astrophysics Data System (ADS)

    Qian, Xin; Admovics, John; Wuu, Cheng-Shie

    2015-01-01

    In a high resolution image-guided small animal irradiation platform, a cone beam computed tomography (CBCT) is integrated with an irradiation unit for precise targeting. Precise quality assurance is essential for both imaging and irradiation components. The conventional commissioning techniques with films face major challenges due to alignment uncertainty and labour intensive film preparation and scanning. In addition, due to the novel design of this platform the mouse stage rotation for CBCT imaging is perpendicular to the gantry rotation for irradiation. Because these two rotations are associated with different mechanical systems, discrepancy between rotation isocenters exists. In order to deliver x-ray precisely, it is essential to verify coincidence of the imaging and the irradiation isocenters. A 3D PRESAGE dosimeter can provide an excellent tool for checking dosimetry and verifying coincidence of irradiation and imaging coordinates in one system. Dosimetric measurements were performed to obtain beam profiles and percent depth dose (PDD). Isocentricity and coincidence of the mouse stage and gantry rotations were evaluated with starshots acquired using PRESAGE dosimeters. A single PRESAGE dosimeter can provide 3 -D information in both geometric and dosimetric uncertainty, which is crucial for translational studies.

  14. A permanent MRI magnet for magic angle imaging having its field parallel to the poles

    NASA Astrophysics Data System (ADS)

    McGinley, John V. M.; Ristic, Mihailo; Young, Ian R.

    2016-10-01

    A novel design of open permanent magnet is presented, in which the magnetic field is oriented parallel to the planes of its poles. The paper describes the methods whereby such a magnet can be designed with a field homogeneity suitable for Magnetic Resonance Imaging (MRI). Its primary purpose is to take advantage of the Magic Angle effect in MRI of human extremities, particularly the knee joint, by being capable of rotating the direction of the main magnetic field B0 about two orthogonal axes around a stationary subject and achieve all possible angulations. The magnet comprises a parallel pair of identical profiled arrays of permanent magnets backed by a flat steel yoke such that access in lateral directions is practical. The paper describes the detailed optimization procedure from a target 150 mm DSV to the achievement of a measured uniform field over a 130 mm DSV. Actual performance data of the manufactured magnet, including shimming and a sample image, is presented. The overall magnet system mounting mechanism is presented, including two orthogonal axes of rotation of the magnet about its isocentre.

  15. A permanent MRI magnet for magic angle imaging having its field parallel to the poles.

    PubMed

    McGinley, John V M; Ristic, Mihailo; Young, Ian R

    2016-10-01

    A novel design of open permanent magnet is presented, in which the magnetic field is oriented parallel to the planes of its poles. The paper describes the methods whereby such a magnet can be designed with a field homogeneity suitable for Magnetic Resonance Imaging (MRI). Its primary purpose is to take advantage of the Magic Angle effect in MRI of human extremities, particularly the knee joint, by being capable of rotating the direction of the main magnetic field B0 about two orthogonal axes around a stationary subject and achieve all possible angulations. The magnet comprises a parallel pair of identical profiled arrays of permanent magnets backed by a flat steel yoke such that access in lateral directions is practical. The paper describes the detailed optimization procedure from a target 150mm DSV to the achievement of a measured uniform field over a 130mm DSV. Actual performance data of the manufactured magnet, including shimming and a sample image, is presented. The overall magnet system mounting mechanism is presented, including two orthogonal axes of rotation of the magnet about its isocentre.

  16. Routine operation of the University of Washington fast neutron therapy facility and plans for improvements

    SciTech Connect

    Risler, R.; Emery, R.; Laramore, G. E.

    1999-06-10

    The fast neutron therapy facility in Seattle is based on a cyclotron, which produces a 50.5 MeV proton beam. Neutrons are produced in a beryllium target installed in an isocentric gantry equipped with a multi-leaf collimator. The system has been in routine operation for 14 years and over 1800 patients have been treated. Downtime has been minimal, over the past 10 years less than 1.5% of the scheduled daily treatment sessions could not be delivered for equipment related reasons. Fast neutron therapy has been shown to be highly effective for the treatment of salivary gland tumors, sarcomas of bone and soft tissues and for certain prostate cancers. In addition there are situations such as non-small cell lung cancer, where results are promising, but success is limited by normal tissue complications. A relatively small selective increase in the tumor dose might lead to a significant clinical improvement in these situations. The use of a boron neutron capture (BNC) boost, utilizing the moderated slow neutrons naturally present in the tissue during fast neutron therapy, may be beneficial for such patients. Experimental work to adapt the facility for such a modified treatment modality is presently ongoing.

  17. Routine operation of the University of Washington fast neutron therapy facility and plans for improvements

    NASA Astrophysics Data System (ADS)

    Risler, R.; Emery, R.; Laramore, G. E.

    1999-06-01

    The fast neutron therapy facility in Seattle is based on a cyclotron, which produces a 50.5 MeV proton beam. Neutrons are produced in a beryllium target installed in an isocentric gantry equipped with a multi-leaf collimator. The system has been in routine operation for 14 years and over 1800 patients have been treated. Downtime has been minimal, over the past 10 years less than 1.5% of the scheduled daily treatment sessions could not be delivered for equipment related reasons. Fast neutron therapy has been shown to be highly effective for the treatment of salivary gland tumors, sarcomas of bone and soft tissues and for certain prostate cancers. In addition there are situations such as non-small cell lung cancer, where results are promising, but success is limited by normal tissue complications. A relatively small selective increase in the tumor dose might lead to a significant clinical improvement in these situations. The use of a boron neutron capture (BNC) boost, utilizing the moderated slow neutrons naturally present in the tissue during fast neutron therapy, may be beneficial for such patients. Experimental work to adapt the facility for such a modified treatment modality is presently ongoing.

  18. Monte Carlo optimization of total body irradiation in a phantom and patient geometry

    NASA Astrophysics Data System (ADS)

    Chakarova, R.; Müntzing, K.; Krantz, M.; Hedin, E.; Hertzman, S.

    2013-04-01

    The objective of this work is to apply a Monte Carlo (MC) accelerator model, validated by experimental data at isocentre distances, to a large-field total body irradiation (TBI) technique and to develop a strategy for individual patient treatment on the basis of MC dose distributions. Calculations are carried out using BEAMnrc/DOSXYZnrc code packages for a 15 MV Varian accelerator. Acceptable agreement is obtained between MC data and measurements in a large water phantom behind a spoiler at source-skin distances (SSD) = 460 cm as well as in a CIRS® thorax phantom. Dose distributions in patients are studied when simulating bilateral beam delivery at a distance of 480 cm to the patient central sagittal plane. A procedure for individual improvement of the dose uniformity is suggested including the design of compensators in a conventional treatment planning system (TPS) and a subsequent update of the dose distribution. It is demonstrated that the dose uniformity for the simple TBI technique can be considerably improved. The optimization strategy developed is straightforward and suitable for clinics where the TPS available is deficient to calculate 3D dose distributions at extended SSD.

  19. Effect of MLC tracking latency on conformal volumetric modulated arc therapy (VMAT) plans in 4D stereotactic lung treatment

    PubMed Central

    Bedford, James L.; Fast, Martin F.; Nill, Simeon; McDonald, Fiona M.A.; Ahmed, Merina; Hansen, Vibeke N.; Oelfke, Uwe

    2015-01-01

    Background and purpose The latency of a multileaf collimator (MLC) tracking system used to overcome respiratory motion causes misalignment of the treatment beam with respect to the gross tumour volume, which may result in reduced target coverage. This study investigates the magnitude of this effect. Material and methods Simulated superior–inferior breathing motion was used to construct histograms of isocentre offset with respect to the gross tumour volume (GTV) for a variety of tracking latencies. Dose distributions for conformal volumetric modulated arc therapy (VMAT) arcs were then calculated at a range of offsets and summed according to these displacement histograms. The results were verified by delivering the plans to a Delta4 phantom on a motion platform. Results In the absence of an internal target margin, a tracking latency of 150 ms reduces the GTV D95% by approximately 2%. With a margin of 2 mm, the same drop in dose occurs for a tracking latency of 450 ms. Lung V13Gy is unaffected by a range of latencies. These results are supported by the phantom measurements. Conclusions Assuming that internal motion can be modelled by a rigid translation of the patient, MLC tracking of conformal VMAT can be effectively accomplished in the absence of an internal target margin for substantial breathing motion (4 s period and 20 mm peak–peak amplitude) so long as the system latency is less than 150 ms. PMID:26277856

  20. Dose distribution for dental cone beam CT and its implication for defining a dose index

    PubMed Central

    Pauwels, R; Theodorakou, C; Walker, A; Bosmans, H; Jacobs, R; Horner, K; Bogaerts, R

    2012-01-01

    Objectives To characterize the dose distribution for a range of cone beam CT (CBCT) units, investigating different field of view sizes, central and off-axis geometries, full or partial rotations of the X-ray tube and different clinically applied beam qualities. The implications of the dose distributions on the definition and practicality of a CBCT dose index were assessed. Methods Dose measurements on CBCT devices were performed by scanning cylindrical head-size water and polymethyl methacrylate phantoms, using thermoluminescent dosemeters, a small-volume ion chamber and radiochromic films. Results It was found that the dose distribution can be asymmetrical for dental CBCT exposures throughout a homogeneous phantom, owing to an asymmetrical positioning of the isocentre and/or partial rotation of the X-ray source. Furthermore, the scatter tail along the z-axis was found to have a distinct shape, generally resulting in a strong drop (90%) in absorbed dose outside the primary beam. Conclusions There is no optimal dose index available owing to the complicated exposure geometry of CBCT and the practical aspects of quality control measurements. Practical validation of different possible dose indices is needed, as well as the definition of conversion factors to patient dose. PMID:22752320

  1. An improved Monte Carlo (MC) dose simulation for charged particle cancer therapy

    NASA Astrophysics Data System (ADS)

    Ying, C. K.; Kamil, W. A.; Shuaib, I. L.; Matsufuji, Naruhiro

    2014-02-01

    Heavy-particle therapy such as carbon ion therapy are more popular nowadays because of the nature characteristics of charged particle and almost no side effect to patients. An effective treatment is achieved with high precision of dose calculation, in this research work, Geant4 based Monte Carlo simulation method has been used to calculate the radiation transport and dose distribution. The simulation have the same setting with the treatment room in Heavy Ion Medical Accelerator, HIMAC. The carbon ion beam at the isocentric gantry nozzle for the therapeutic energy of 290 MeV/u was simulated, experimental work was carried out in National Institute of Radiological Sciences, NIRS, Chiba, Japan by using the HIMAC to confirm the accuracy and qualities dose distribution by MC methods. The Geant4 based simulated dose distribution were verified with measurements for Bragg peak and spread out Bragg peak (SOBP) respectively. The verification of results shows that the Bragg peak depth-dose and SOBP distributions in simulation has good agreement with measurements. In overall, the study showed that Geant4 based can be fully applied in the heavy-ion therapy field for simulation, further works need to be carry on to refine and improve the Geant4 MC simulations.

  2. A haptic unit designed for magnetic-resonance-guided biopsy.

    PubMed

    Tse, Z T H; Elhawary, H; Rea, M; Young, I; Davis, B L; Lamperth, M

    2009-02-01

    The magnetic fields present in the magnetic resonance (MR) environment impose severe constraints on any mechatronic device present in its midst, requiring alternative actuators, sensors, and materials to those conventionally used in traditional system engineering. In addition the spatial constraints of closed-bore scanners require a physical separation between the radiologist and the imaged region of the patient. This configuration produces a loss of the sense of touch from the target anatomy for the clinician, which often provides useful information. To recover the force feedback from the tissue, an MR-compatible haptic unit, designed to be integrated with a five-degrees-of-freedom mechatronic system for MR-guided prostate biopsy, has been developed which incorporates position control and force feedback to the operator. The haptic unit is designed to be located inside the scanner isocentre with the master console in the control room. MR compatibility of the device has been demonstrated, showing a negligible degradation of the signal-to-noise ratio and virtually no geometric distortion. By combining information from the position encoder and force sensor, tissue stiffness measurement along the needle trajectory is demonstrated in a lamb liver to aid diagnosis of suspected cancerous tissue.

  3. Aperture modulated arc therapy

    NASA Astrophysics Data System (ADS)

    Crooks, S. M.; Wu, Xiaodong; Takita, C.; Watzich, M.; Xing, Lei

    2003-05-01

    We show that it is possible to translate an intensity modulated radiation therapy (IMRT) treatment plan and deliver it as a single arc. This technique is referred to in this paper as aperture modulation arc therapy (AMAT). During this arc, the MLC leaves do not conform to the projection of the target PTV and the machine output of the accelerator has a constant value. Dose was calculated using the CORVUS 4.0 IMRT system, which uses a pencil beam dose algorithm, and treatments were delivered using a Varian 2100C/D Clinac. Results are presented for a head and neck and a prostate case, showing the equivalence of the IMRT and the translated AMAT delivery. For a prostate AMAT delivery, coronal plane film dose for the IMRT and AMAT deliveries agreed within 7.19 +/- 6.62%. For a meningioma the coronal plane dose distributions were similar to a value of 4.6 +/- 6.62%. Dose to the isocentre was measured as being within 2% of the planned value in both cases.

  4. Radiotherapy of stage IEA primary breast lymphoma: case report.

    PubMed

    Juretić, Antonio; Zivković, Mirko; Samija, Mirko; Bagović, Davorin; Purisić, Anka; Viculin, Tomislav; Bistrović, Matija; Stanec, Mladen; Juzbasić, Stjepan; Lesar, Miro; Tomek, Rudolf

    2002-10-01

    A 47-year-old woman was referred for the treatment to our Hospital because of a palpable nodule in the upper medial quadrant of her right breast. After tumor excision, pathohistological examination showed a follicular center cell lymphoma grade 2, B-cell type (CD20+, bc16+, CD10+, bcl2+). The final diagnosis was stage IEA primary extranodal non-Hodgkin s breast lymphoma. The involved breast was irradiated isocentrically with two opposite 6-megavolt (MeV) photon beams delivered from the linear accelerator (tangential fields) using asymmetric collimator opening. Radiation volume, inclinations of the medial and lateral field, and the part of the underlying chest wall and lung parenchyma were determined during the radiotherapy simulation process. The total irradiation dose was 44 Gy delivered in single daily doses of 2 Grays (Gy). After breast photon irradiation, a boost to the tumor bed was performed by a direct 12 MeV electron beam, with a total dose of 6 Gy delivered over three days. Since primary non-Hodgkin lymphoma of the breast is rather rare, there has been no uniform approach to its treatment. The advantage of applying the asymmetric collimator jaw opening in breast radiotherapy is the instant reduction of the dose at margin fields, resulting in both the protection of neighboring lung parenchyma and the good coverage of planned target volume.

  5. Measurement of neutron ambient dose equivalent in carbon-ion radiotherapy with an active scanned delivery system.

    PubMed

    Yonai, S; Furukawa, T; Inaniwa, T

    2014-10-01

    In ion beam radiotherapy, secondary neutrons contribute to an undesired dose outside the target volume, and consequently the increase of secondary cancer risk is a growing concern. In this study, neutron ambient dose equivalents in carbon-ion radiotherapy (CIRT) with an active beam delivery system were measured with a rem meter, WENDI-II, at National Institute of Radiological Sciences. When the same irradiation target was assumed, the measured neutron dose with an active beam was at most ∼15 % of that with a passive beam. This percentage became smaller as larger distances from the iso-centre. Also, when using an active beam delivery system, the neutron dose per treatment dose in CIRT was comparable with that in proton radiotherapy. Finally, it was experimentally demonstrated that the use of an active scanned beam in CIRT can greatly reduce the secondary neutron dose. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  6. Evaluation of the peripheral dose to uterus in breast carcinoma radiotherapy.

    PubMed

    Martín Rincón, C; Jerez Sainz, I; Modolell Farré, I; España López, M L; López Franco, P; Muñiz, J L; Romero, A M; Rodríguez, R

    2002-01-01

    The absorbed dose outside of the direct fields of radiotherapy treatment (or peripheral dose, PD) is responsible for radiation exposure of the fetus in pregnant women. Because the radiological protection of the unborn child is of particular concern in the early period of the pregnancy, the aim of this study is to estimate the PD in order to assess the absorbed dose in the uterus in a pregnant patient irradiated for breast carcinoma therapy. The treatment was simulated on an Alderson-Rando anthropomorphic phantom, and the radiation dose to the fetus was measured using an ionisation chamber and thermoluminescence dosemeters. Two similar treatments plans with and without wedges were delivered, using a 6 MV photon beam with two isocentric opposite tangential fields with a total dose of 50 Gy, in accordance with common established procedures. Average field parameters for more than 300 patients were studied. Measurements showed the fetal dose to be slightly lower than 50 mGy, a level at which the risk to the fetus is uncertain, although several authors consider this value as the dose threshold for deterministic effects. The planning system (PS) underestimated PD values and no significant influence was found with the use of wedge filters.

  7. Do All Patients of Breast Carcinoma Need 3-Dimensional CT-Based Planning? A Dosimetric Study Comparing Different Breast Sizes

    SciTech Connect

    Munshi, Anusheel Pai, Rajeshri H.; Phurailatpam, Reena; Budrukkar, Ashwini; Jalali, Rakesh; Sarin, Rajiv; Deshpande, D.D.; Shrivastava, Shyam K.; Dinshaw, Ketayun A.

    2009-07-01

    Evaluation of dose distribution in a single plane (i.e., 2-dimensional [2D] planning) is simple and less resource-intensive than CT-based 3-dimensional radiotherapy (3DCRT) planning or intensity modulated radiotherapy (IMRT). The aim of the study was to determine if 2D planning could be an appropriate treatment in a subgroup of breast cancer patients based on their breast size. Twenty consecutive patients who underwent breast conservation were planned for radiotherapy. The patients were grouped in 3 different categories based on their respective chest wall separation (CWS) and the thickness of breast, as 'small,' 'medium,' and 'large.' Two more contours were taken at locations 5 cm superior and 5 cm inferior to the isocenter plane. Maximum dose recorded at specified points was compared in superior/inferior slices as compared to the central slice. The mean difference for small breast size was 1.93 (standard deviation [SD] = 1.08). For medium breas size, the mean difference was 2.98 (SD = 2.40). For the large breasts, the mean difference was 4.28 (SD = 2.69). Based on our dosimetric study, breast planning only on the single isocentric contour is an appropriate technique for patients with small breasts. However, for large- and medium-size breasts, CT-based planning and 3D planning have a definite role. These results can be especially useful for rationalizing treatment in busy oncology centers.

  8. Clinical implementation of a digital tomosynthesis-based seed reconstruction algorithm for intraoperative postimplant dose evaluation in low dose rate prostate brachytherapy

    SciTech Connect

    Brunet-Benkhoucha, Malik; Verhaegen, Frank; Lassalle, Stephanie; Beliveau-Nadeau, Dominic; Reniers, Brigitte; Donath, David; Taussky, Daniel; Carrier, Jean-Francois

    2009-11-15

    Purpose: The low dose rate brachytherapy procedure would benefit from an intraoperative postimplant dosimetry verification technique to identify possible suboptimal dose coverage and suggest a potential reimplantation. The main objective of this project is to develop an efficient, operator-free, intraoperative seed detection technique using the imaging modalities available in a low dose rate brachytherapy treatment room. Methods: This intraoperative detection allows a complete dosimetry calculation that can be performed right after an I-125 prostate seed implantation, while the patient is still under anesthesia. To accomplish this, a digital tomosynthesis-based algorithm was developed. This automatic filtered reconstruction of the 3D volume requires seven projections acquired over a total angle of 60 deg. with an isocentric imaging system. Results: A phantom study was performed to validate the technique that was used in a retrospective clinical study involving 23 patients. In the patient study, the automatic tomosynthesis-based reconstruction yielded seed detection rates of 96.7% and 2.6% false positives. The seed localization error obtained with a phantom study is 0.4{+-}0.4 mm. The average time needed for reconstruction is below 1 min. The reconstruction algorithm also provides the seed orientation with an uncertainty of 10 deg. {+-}8 deg. The seed detection algorithm presented here is reliable and was efficiently used in the clinic. Conclusions: When combined with an appropriate coregistration technique to identify the organs in the seed coordinate system, this algorithm will offer new possibilities for a next generation of clinical brachytherapy systems.

  9. A method for online verification of adapted fields using an independent dose monitor

    SciTech Connect

    Chang Jina; Norrlinger, Bernhard D.; Heaton, Robert K.; Jaffray, David A.; Cho, Young-Bin; Islam, Mohammad K.; Mahon, Robert

    2013-07-15

    Purpose: Clinical implementation of online adaptive radiotherapy requires generation of modified fields and a method of dosimetric verification in a short time. We present a method of treatment field modification to account for patient setup error, and an online method of verification using an independent monitoring system.Methods: The fields are modified by translating each multileaf collimator (MLC) defined aperture in the direction of the patient setup error, and magnifying to account for distance variation to the marked isocentre. A modified version of a previously reported online beam monitoring system, the integral quality monitoring (IQM) system, was investigated for validation of adapted fields. The system consists of a large area ion-chamber with a spatial gradient in electrode separation to provide a spatially sensitive signal for each beam segment, mounted below the MLC, and a calculation algorithm to predict the signal. IMRT plans of ten prostate patients have been modified in response to six randomly chosen setup errors in three orthogonal directions.Results: A total of approximately 49 beams for the modified fields were verified by the IQM system, of which 97% of measured IQM signal agree with the predicted value to within 2%.Conclusions: The modified IQM system was found to be suitable for online verification of adapted treatment fields.

  10. Ionization chamber radial response deconvolution in megavoltage photon beam

    NASA Astrophysics Data System (ADS)

    Kulmala, A.; Tenhunen, M.

    2017-09-01

    The aim of this paper is to study a radial response model as a method, to correct output factor results gathered with ionization chambers of different size and shape in cone collimated RT fields. An enhanced version of a non-parametric super-resolution deconvolution method able to model a radial response function of a small cylinder symmetric ionization chamber is described and demonstrated. The radial response of four ionization chambers with different geometry and radius are estimated using 6 MV photon beam in water at the isocentre plane. Finally the validity of the estimates is tested by applying the response functions to the output factor measurements of 4–20 mm conical collimators. The enhanced method is demonstrated by obtaining the response function characteristics with a spatial uncertainty smaller than 0.1 mm when the distance from chamber axis is larger than 0.5 mm. In all studied ionization chambers, a significant local response maximum is found close to the air cavity boundary. The agreement between the output factor results of different chambers is promising, the largest difference (max—min) in output factor is 4% obtained for the smallest 4 mm cone size.

  11. Radiosurgical third ventriculostomy: Technical note

    PubMed Central

    Gutiérrez-Aceves, Guillermo Axayacalt; Moreno-Jiménez, Sergio; Celis, Miguel Ángel; Hernández-Bojórquez, Mariana

    2012-01-01

    Background: We describe a minimally invasive technique to perform a radiosurgical third ventriculostomy in a patient with mild obstructive hydrocephalus secondary to malignant pathology. Methods: A 42 years old woman with diagnosis of clear cells renal carcinoma and with right nefrectomy performed last year. Cranial Magnetic Resonance Imaging showed two brain metastasis: one right temporal, and other in the pons with Sylvian aqueduct partial obliteration and mild ventricular enlargement. The patient received radiosurgical treatment for brain metastasis; after this procedure a new target was defined on the floor of the third ventricle, in the midpoint between the mamillary bodies and the infundibular recess where we delivered 100 Gy delivered by an isocentric multiple noncoplanar arcs technique, with a 6 MV Novalis® dedicated LINAC. A series of 21 arcs was arranged with a radiation field generated by a 4 mm circular collimator. Results: One week pos-irradiation in the head CT we did not find significant changes in the metastatic lesions; however the VSI diminished 4%, despite of persistent aqueduct obliteration. At three months we perform 3.0 T MRI where we confirmed the presence of the third ventriculostomy (2.63 mm diameter). Conclusion: This report demonstrates, for the first time, the ability of a dedicated LINAC to perform a precise third ventriculostomy without associate morbility in short term. PMID:23226607

  12. Compact multileaf collimator for conformal and intensity modulated fast neutron therapy: electromechanical design and validation.

    PubMed

    Farr, J B; Maughan, R L; Yudelev, M; Blosser, E; Brandon, J; Horste, T; Forman, J D

    2006-09-01

    The electromechanical properties of a 120-leaf, high-resolution, computer-controlled, fast neutron multileaf collimator (MLC) are presented. The MLC replaces an aging, manually operated multirod collimator. The MLC leaves project 5 mm in the isocentric plane perpendicular to the beam axis. A taper is included on the leaves matching beam divergence along one axis. The 5-mm leaf projection width is chosen to give high-resolution conformality across the entire field. The maximum field size provided is 30 x 30 cm2. To reduce the interleaf transmission a 0.254-mm blocking step is included. End-leaf steps totaling 0.762 mm are also provided allowing opposing leaves to close off within the primary radiation beam. The neutron MLC also includes individual 45 degrees and 60 degrees automated universal tungsten wedges. The automated high-resolution neutron collimation provides an increase in patient throughput capacity, enables a new modality, intensity modulated neutron therapy, and limits occupational radiation exposure by providing remote operation from a shielded console area.

  13. Influence of the electron energy and number of beams on the absorbed dose distributions in radiotherapy of deep seated targets.

    PubMed

    Garnica-Garza, H M

    2014-12-01

    With the advent of compact laser-based electron accelerators, there has been some renewed interest on the use of such charged particles for radiotherapy purposes. Traditionally, electrons have been used for the treatment of fairly superficial lesions located at depths of no more than 4cm inside the patient, but lately it has been proposed that by using very high energy electrons, i.e. those with an energy in the order of 200-250MeV it should be possible to safely reach deeper targets. In this paper, we used a realistic patient model coupled with detailed Monte Carlo simulations of the electron transport in such a patient model to examine the characteristics of the resultant absorbed dose distributions as a function of both the electron beam energy as well as the number of beams for a particular type of treatment, namely, a prostate radiotherapy treatment. Each treatment is modeled as consisting of nine, five or three beam ports isocentrically distributed around the patient. An optimization algorithm is then applied to obtain the beam weights in each treatment plan. It is shown that for this particularly challenging case, both excellent target coverage and critical structure sparing can be obtained for energies in the order of 150MeV and for as few as three treatment ports, while significantly reducing the total energy absorbed by the patient with respect to a conventional megavoltage x-ray treatment.

  14. An ion-optical design study of a carbon-ion rotating gantry with a superconducting final bending magnet

    NASA Astrophysics Data System (ADS)

    Bokor, J.; Pavlovič, M.

    2016-03-01

    Ion-optical designs of an isocentric ion gantry with a compact curved superconducting final bending magnet are presented. The gantry is designed for transporting carbon-therapy beams with nominal kinetic energy of 400 MeV/u, which corresponds to the penetration range of C6+ beam in water of about 28 cm. In contrast to other existing designs, we present a ;hybrid; beam transport system containing a single superconducting element - the last bending magnet. All other elements are based on conventional warm technology. Ion-optical properties of such a hybrid system are investigated in case of transporting non-symmetric (i.e. different emittance patterns in the horizontal and vertical plane) beams. Different conditions for transporting the non-symmetric beams are analyzed aiming at finding the optimal, i.e. the most compact, gantry version. The final gantry layout is presented including a 2D parallel scanning. The ion-optical and scanning properties of the final gantry design are described, discussed and illustrated by computer simulations performed by WinAGILE.

  15. A 3D superposition pencil beam dose calculation algorithm for a 60Co therapy unit and its verification by MC simulation

    NASA Astrophysics Data System (ADS)

    Koncek, O.; Krivonoska, J.

    2014-11-01

    The MCNP Monte Carlo code was used to simulate the collimating system of the 60Co therapy unit to calculate the primary and scattered photon fluences as well as the electron contamination incident to the isocentric plane as the functions of the irradiation field size. Furthermore, a Monte Carlo simulation for the polyenergetic Pencil Beam Kernels (PBKs) generation was performed using the calculated photon and electron spectra. The PBK was analytically fitted to speed up the dose calculation using the convolution technique in the homogeneous media. The quality of the PBK fit was verified by comparing the calculated and simulated 60Co broad beam profiles and depth dose curves in a homogeneous water medium. The inhomogeneity correction coefficients were derived from the PBK simulation of an inhomogeneous slab phantom consisting of various materials. The inhomogeneity calculation model is based on the changes in the PBK radial displacement and on the change of the forward and backward electron scattering. The inhomogeneity correction is derived from the electron density values gained from a complete 3D CT array and considers different electron densities through which the pencil beam is propagated as well as the electron density values located between the interaction point and the point of dose deposition. Important aspects and details of the algorithm implementation are also described in this study.

  16. Short communication: assessment of environmental disturbances to the static magnetic field in magnetic resonance installations.

    PubMed

    Schmidt, M A

    2006-05-01

    The static magnetic field of MRI scanners can be affected by environmental factors. Magnetic resonance spectroscopy and functional imaging with single-shot echo-planar imaging (EPI) are particularly vulnerable to the movement of lifts, vehicles, trains and other large metallic masses in the vicinity. This work investigates the sensitivity of two different imaging techniques to assess disturbances of the static magnetic field: (i) phase changes in gradient-echo images of a uniform test object; and (ii) image displacement along the phase encoding direction in single-shot EPI images. For the latter a hexane sample was used, and the separation between CH2 and CH3 signals was taken as a reference. Both techniques were evaluated in a site known to be free of any significant environmental disturbances and validated by inducing a magnetic field disturbance. Both techniques provide valuable information in acceptance tests, allowing MRI users to evaluate and manage the environmental conditions surrounding a scanner. The single-shot EPI technique was found to be highly sensitive, being expected to detect magnetic field fluctuations down to 0.005 parts per million (ppm). The phase images method was found to be less sensitive (0.02 ppm) but is more easily available. The single-shot EPI technique was used in acceptance tests and environmental disturbances to the magnetic field of the order of 0.04 ppm were measured at the isocentre on two separate occasions.

  17. Analytical description of dose profile behaviour in Gamma Knife radiosurgery

    NASA Astrophysics Data System (ADS)

    Fenner, J.; Gwilliam, M.; Mehrem, R.; Bird, A.; Walton, L.

    2008-04-01

    Stereotactic Gamma Knife radiosurgery utilizes ionizing beams from 60Co sources and relies on a combination of collimator sizes, weighting, etc to generate a high-dose region that is conformal with a designated target volume. Dose computation is typically performed by computer, but in this paper, single collimator dose profile behaviour is modelled analytically and then extended to accommodate multiple collimators of different weights with co-located isocentres. The dose profile from a single helmet is derived from a top-hat beam profile approximation and an idealized symmetric distribution of sources is used to represent the 201 sources within a collimating helmet. The results from the analysis are validated by an independent numerical model and also compared with those obtained by other groups using numerical and experimental methods. With respect to multiple collimators, the relationship between the size (full width half maximum) of the irradiated volume and relative collimator weighting is also examined using the simple analytical model. The simplicity of the mathematics clarifies the relationship between beam profile, dose profile and multiple collimator behaviour, and provides data that compare favourably with published literature.

  18. Dosimetrical evaluation of Leksell Gamma Knife 4C radiosurgery unit

    NASA Astrophysics Data System (ADS)

    Sajeev, Thomas; Mustafa, Mohamed M.; Supe, Sanjay S.

    2011-01-01

    A number of experiments was performed using standard protocols, in order to evaluate the dosimetric accuracy of Leksell Gamma Knife 4C unit. Verification of the beam alignment has been performed for all collimators using solid plastic head phantom and Gafchromic™ type MD-55 films. The study showed a good agreement of Leksell Gammaplan calculated dose profiles with experimentally determined profiles in all three axes. Isocentric accuracy is verified using a specially machined cylindrical aluminium film holder tool made with very narrow geometric tolerances aligned between trunnions of 4 mm collimator. Considering all uncertainties in all three dimensions, the estimated accuracy of the unit was 0.1 mm. Dose rate at the centre point of the unit has been determined according to the IAEA, TRS-398 protocol, using Unidose-E (PTW-Freiburg, Germany) with a 0.125 cc ion chamber, over a period of 6 years. The study showed that the Leksell Gamma Knife 4C unit is excellent radiosurgical equipment with high accuracy and precision, which makes it possible to deliver larger doses of radiation, within the limits defined by national and international guidelines, applicable for stereotactic radiosurgery procedures.

  19. Application of Histogram Analysis in Radiation Therapy (HART) in Intensity Modulation Radiation Therapy (IMRT) Treatments

    NASA Astrophysics Data System (ADS)

    Pyakuryal, Anil

    2009-03-01

    A carcinoma is a malignant cancer that emerges from epithelial cells in structures through out the body.It invades the critical organs, could metastasize or spread to lymph nodes.IMRT is an advanced mode of radiation therapy treatment for cancer. It delivers more conformal doses to malignant tumors sparing the critical organs by modulating the intensity of radiation beam.An automated software, HART (S. Jang et al.,2008,Med Phys 35,p.2812) was used for efficient analysis of dose volume histograms (DVH) for multiple targets and critical organs in four IMRT treatment plans for each patient. IMRT data for ten head and neck cancer patients were exported as AAPM/RTOG format files from a commercial treatment planning system at Northwestern Memorial Hospital (NMH).HART extracted DVH statistics were used to evaluate plan indices and to analyze dose tolerance of critical structures at prescription dose (PD) for each patient. Mean plan indices (n=10) were found to be in good agreement with published results for Linac based plans. The least irradiated volume at tolerance dose (TD50) was observed for brainstem and the highest volume for larynx in SIB treatment techniques. Thus HART, an open source platform, has extensive clinical implications in IMRT treatments.

  20. Initial studies of Bremsstrahlung energy deposition in small-bore superconducting undulator structures in linac environments

    SciTech Connect

    Cremer, T.; Tatchyn, R.

    1995-12-31

    One of the more promising technologies for developing minimal-length insertion devices for linac-driven, single-pass Free Electron Lasers (FELs) operating in the x-ray range is based on the use of superconducting (SC) materials. In recent FEL simulations, for example, a bifilar helical SC device with a 2 cm period and 1.8 T field was found to require a 30 m saturation length for operation at 1.5{Angstrom} on a 15 GeV linac, more than 40% shorter than an alternative hybrid/permanent magnet (hybrid/PM) undulator. AT the same time, however, SC technology is known to present characteristic difficulties for insertion device design, both in engineering detail and in operation. Perhaps the most critical problem, as observed, e.g., by Madey and co-workers in their initial FEL experiments, was the frequent quenching induced by scattered electrons upstream of their (bifilar) device. Postulating that this quenching was precipitated by directly-scattered or bremsstrahlung-induced particle energy deposited into the SC material or into material contiguous with it, the importance of numerical and experimental characterizations of this phenomenon for linac-based, user-facility SC undulator design becomes evident. In this paper we discuss selected prior experimental results and report on initial EGS4 code studies of scattered and bremsstrahlung induced particle energy deposition into SC structures with geometries comparable to a small-bore bifilar helical undulator.

  1. SU-C-303-01: Activation-Induced Cytidine Deaminase Confers Cancer Resistance to Radiation Therapy

    SciTech Connect

    Yi, S; La Count, S; Liu, J; Bai, X; Lu, L

    2015-06-15

    Purpose: To study the role of activation-induced cytidine deaminase (AID) in malignant cell resistance to radiation therapy. Methods: We first developed several small devices that could be used to adopt radiation beams from clinical high dose rate brachy therapy (HDR) or linac-based megavoltage machines to perform pre-clinical cell and mouse experiments. Then we used these devices to deliver radiation to AID-positive and AID-silenced cancer cells or tumors formed by these cells in mice. Cells and mice bearing tumors received the same dose under the same experimental conditions. For cells, we observed the apoptosis and the cell survival rate over time. For mice bearing tumors, we measured and recorded the tumor sizes every other day for 4 weeks. Results: For cell experiments, we found that the AID-positive cells underwent much less apoptosis compared with AID-silenced cells upon radiation. And for mouse experiments, we found that AID-positive tumors grew significantly faster than the AID-silenced tumors despite of receiving the same doses of radiation. Conclusion: Our study suggests that AID may confer cancer resistance to radiation therapy, and AID may be a significant biomarker predicting cancer resistance to radiation therapy for certain cancer types.

  2. Longitudinal Profile Diagnostic Scheme with Subfemtosecond Resolution for High-Brightness Electron Beams

    SciTech Connect

    Andonian, G.; Hemsing, E.; Xiang, D.; Musumeci, P.; Murokh, A.; Tochitsky, S.; Rosenzweig, J.B.; /UCLA

    2012-05-03

    High-resolution measurement of the longitudinal profile of a relativistic electron beam is of utmost importance for linac based free-electron lasers and other advanced accelerator facilities that employ ultrashort bunches. In this paper, we investigate a novel scheme to measure ultrashort bunches (subpicosecond) with exceptional temporal resolution (hundreds of attoseconds) and dynamic range. The scheme employs two orthogonally oriented deflecting sections. The first imparts a short-wavelength (fast temporal resolution) horizontal angular modulation on the beam, while the second imparts a long-wavelength (slow) angular kick in the vertical dimension. Both modulations are observable on a standard downstream screen in the form of a streaked sinusoidal beam structure. We demonstrate, using scaled variables in a quasi-1D approximation, an expression for the temporal resolution of the scheme and apply it to a proof-of-concept experiment at the UCLA Neptune high-brightness injector facility. The scheme is also investigated for application at the SLAC NLCTA facility, where we show that the subfemtosecond resolution is sufficient to resolve the temporal structure of the beam used in the echo-enabled free-electron laser. We employ beam simulations to verify the effect for typical Neptune and NLCTA parameter sets and demonstrate the feasibility of the concept.

  3. Tests of photocathodes for high repetition rate x-ray FELs at the APEX facility at LBNL

    NASA Astrophysics Data System (ADS)

    Sannibale, Fernando; Filippetto, Daniele; Qian, Houjun; Papadopoulos, Christos F.; Wells, Russell; Kramasz, Toby; Padmore, Howard; Feng, Jun; Nasiatka, James; Huang, Ruixuan; Zolotorev, Max; Staples, John W.

    2015-05-01

    After the formidable results of X-ray 4th generation light sources based on free electron lasers around the world, a new revolutionary step is undergoing to extend the FEL performance from the present few hundred Hz to MHz-class repetition rates. In such facilities, temporally equi-spaced pulses will allow for a wide range of previously non-accessible experiments. The Advanced Photo-injector EXperiment (APEX) at the Lawrence Berkeley National Laboratory (LBNL), is devoted to test the capability of a novel scheme electron source, the VHF-Gun, to generate the required electron beam brightness at MHz repetition rates. In linac-based FELs, the ultimate performance in terms of brightness is defined at the injector, and in particular, cathodes play a major role in the game. Part of the APEX program consists in testing high quantum efficiency photocathodes capable to operate at the conditions required by such challenging machines. Results and status of these tests at LBNL are presented.

  4. The optimization of a DC injector for the Energy Recovery Linac upgrade to APS

    SciTech Connect

    Sun, Yin-e; Shang, Hairong; Borland, Michael; Li, Yuelin; Harkay, Katherine; /ANL, APS

    2008-10-01

    An energy recovery linac based light source is a potential revolutionary upgrade to the Advanced Photon Source (APS) at Argonne National Laboratory. The concept relies on several key research areas, one of which is the generation of ultra-low emittance, high-average-current electron beams. In this paper, we present our investigation of a dc-gun-based system for ultra-low emittance bunches in the 20 pC range. A parallel multi-objective numerical optimization is performed in multi-parameter space. Parameters varied include experimentally feasible drive-laser shapes, the DC gun voltage, the thermal energy of the emitted photo-electrons and other electric or magnetic field strengths, RF cavity phase etc. Our goal is to deliver a {approx}10 MeV, 20 pC bunch at the entrance of the linac with an emittance of 0.1 {micro}m or lower, rms bunch length of 2 {approx} 3 ps, and energy spread no larger than 140 keV. We present the machine parameters needed to generate such an injector beam, albeit without a merger.

  5. A proposed VUV oscillator-based FEL upgrade at Jefferson Lab

    SciTech Connect

    Benson, S. V.; Douglas, D. R.; Evtushenko, P.; Hannon, F. E.; Hernandez-Garcia, C.; Klopf, J. M.; Legg, R. A.; Neil, G. R.; Shinn, M. D.; Tennant, C. D.; Zhang, S.; Williams, G. P.

    2011-09-20

    Advances in superconducting linac technology offer the possibility of an upgrade of the Jefferson Lab Free Electron Laser (JLab FEL) facility to an oscillator-based VUV-FEL that would produce 6 x 10{sup 12} coherent 100 eV photons per pulse at multi-MHz repetition rates in the fundamental. At present JLab operates a pair of oscillator-based continuous-wave Free Electron Lasers (FELs) as a linac-based next generation light source in the IR and UV, with sub-picosecond pulses up to 75 MHz. Harmonics upwards of 10 eV are produced and the fully coherent nature of the source results in peak and average brightness values that are several orders of magnitude higher than storage rings. The accelerator uses an energy recovered linac design for efficiency of operation. New style superconducting linac cryomodules with higher gradient, combined with a new injector and beam transport system allow the development of the FEL to higher photon energies.

  6. Commissioning of mini-multi-leaf-collimator (MMLC) for stereotactic radiosurgery and radiotherapy.

    PubMed

    Mardirossian, George; Urie, Marcia; Fitzgerald, Thomas J; Mayr, Nina; Montebello, Joseph; Lo, Yuan-Chynan

    2003-01-01

    Commissioning of a Radionics miniature multi-leaf collimator (MMLC) for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) is reported. With single isocenter and multi static fields, the MMLC can provide better conformity of dose distributions to the target and/or irregularly shaped target volumes than standard arc (circular) field beams with multiple isocenters. Advantages offered by the MMLC over traditional LINAC based SRS and SRT includes greatly improved dose homogeneity to the target, reduced patient positioning time and reduced treatment time. In this work, the MMLC is attached to a Varian 2300 C/D with Varian 80-leaf multi-leaf collimator. The MMLC has 62 leaves, each measured to a width of 3.53 mm at isocenter, with fields range from 1x1 cm to less than 10 × 12 cm. Beam parameters required by the Radionics treatment planning system (XPlan version 2) for evaluating the dose include tissue maximum ratio (TMR), scatter factors (SF), off-axis ratios (OAR), output factors, penumbra function (P) and transmission factors (TF) are performed in this work. Beam data are acquired with a small stereotactic diode, standard ion chambers and radiographic films. Measured profiles of dose distribution are compared to those calculated by the software and absolute dosimetry is performed.

  7. Electron Bunch Shape Measurements Using Electro-optical Spectral Decoding

    NASA Astrophysics Data System (ADS)

    Borysenko, A.; Hiller, N.; Müller, A.-S.; Steffen, B.; Peier, P.; Ivanisenko, Y.; Ischebeck, R.; Schlott, V.

    Longitudinal diagnostics of the electron bunch shapes play a crucial role in the operation of linac-based light sources. Electro-optical techniques allow us to measure the longitudinal electron bunch profiles non-destructively on a shot-by-shot basis. Here we present results from measurements of electron bunches with a length of 200-900 fs rms at the Swiss FEL Injector Test Facility. All the measurements were done using an Yb-doped fibre laser system (with a central wavelength of a 1050 nm) and a GaP crystal. The technique of electro-optical spectral decoding (EOSD) was applied and showed great capabilities to measure bunch shapes down to around 370 fs rms. Measurements were performed for different electron energies to study the expected distortions of the measured bunch profile due to the energy-dependent widening of the electric field, which plays a role for low beam energies below and around 40 MeV. The studies provide valuable input for the design of the EOSD monitors for the compact linear accelerator FLUTE that is currently under commissioning at the Karslruhe Institute of Technology (KIT).

  8. Development of 5-sector, 360o compression magnet for electron Linac

    NASA Astrophysics Data System (ADS)

    Dhavale, A. S.; Acharya, S.; Sharma, V.

    2017-07-01

    A 30 MeV RF electron linac based neutron source will be set up by APPD, BARC at IGCAR, Kalpakkam. This facility will include neutron activation of sodium by photo neutrons for FBR shielding studies and Neutron Time of Flight (n-TOF) facility for various research applications. In n-TOF facility, 10 ns, 10 A electron beam having 40% energy spread (18-30 MeV) will be generated by S-band linac. A compression magnet will compress 10 ns, 10 A electron pulse to 1 ns, 100 A. It will be a 360o, 5-sector, zero gradient magnet having rectangular yoke of dimensions 3.2 m × 2.7 m × 0.4 m and weight ~ 24 Ton. The pulse compression ratio of 10:1 will be achieved at a magnetic field of 0.1 T. A scale down model of the magnet is designed, fabricated and tested. This magnet produces 0.1 T field at 4200 A-turns. It can compress the 6 MeV electron pulse with 3:1 ratio. The present paper describes the compression magnet design, simulation results, fabrication details and the experimental results.

  9. Neutron time-of-flight spectroscopy measurement using a waveform digitizer

    NASA Astrophysics Data System (ADS)

    Liu, Long-Xiang; Wang, Hong-Wei; Ma, Yu-Gang; Cao, Xi-Guang; Cai, Xiang-Zhou; Chen, Jin-Gen; Zhang, Gui-Lin; Han, Jian-Long; Zhang, Guo-Qiang; Hu, Ji-Feng; Wang, Xiao-He

    2016-05-01

    The photoneutron source (PNS, phase 1), an electron linear accelerator (linac)-based pulsed neutron facility that uses the time-of-flight (TOF) technique, was constructed for the acquisition of nuclear data from the Thorium Molten Salt Reactor (TMSR) at the Shanghai Institute of Applied Physics (SINAP). The neutron detector signal used for TOF calculation, with information on the pulse arrival time, pulse shape, and pulse height, was recorded by using a waveform digitizer (WFD). By using the pulse height and pulse-shape discrimination (PSD) analysis to identify neutrons and γ-rays, the neutron TOF spectrum was obtained by employing a simple electronic design, and a new WFD-based DAQ system was developed and tested in this commissioning experiment. The DAQ system developed is characterized by a very high efficiency with respect to millisecond neutron TOF spectroscopy. Supported by Strategic Priority Research Program of the Chinese Academy of Science(TMSR) (XDA02010100), National Natural Science Foundation of China(NSFC)(11475245,No.11305239), Shanghai Key Laboratory of Particle Physics and Cosmology (11DZ2260700)

  10. Preliminary study of EEHG-based superradiant undulator radiation at the HLS-II storage ring

    NASA Astrophysics Data System (ADS)

    Gao, Wei-Wei; Li, He-Ting; Wang, Lin

    2017-07-01

    We investigate storage ring-based Echo-Enabled Harmonic Generation (EEHG) superradiant undulator radiation as a possible scheme to obtain shorter wavelengths at the HLS-II (Hefei Light Source-II) storage ring. In this paper we give the designation of the storage ring based EEHG up to the 26th harmonic, where 31 nm vacuum ultraviolet light is radiated from an 800 nm seeded laser. The novelty of our design is that both the two dispersion sections of EEHG are realized by the storage ring’s own magnet structure. In particular, the whole ring is used as the first dispersion section, and two modulators of the traditional EEHG can be done with the same undulator. These two dispersion sections are realized by changing the superperiod of the present lattice structure, and more precisely by changing the focusing strengths of the present structure. Since no additional magnets and chicanes are used, the beam circulates around the storage ring repeatedly, and thus this storage ring-based EEHG can have a higher repetition rate than a linac-based EEHG. Supported by National Natural Science Foundation of China (11305170)

  11. Beam tuning

    SciTech Connect

    Pardo, R.C.; Zinkann, G.P.

    1995-08-01

    A program for configuring the linac, based on previously run configurations for any desired beam was used during the past year. This program uses only a small number of empirical tunes to scale resonator fields to properly accelerate a beam with a different charge-to-mass (q/A) ratio from the original tune configuration. The program worked very well for the PII linac section where we can easily match a new beam`s arrival phase and velocity to the tuned value. It was also fairly successful for the Booster and ATLAS sections of the linac, but not as successful as for the PII linac. Most of the problems are associated with setting the beam arrival time correctly for each major linac section. This problem is being addressed with the development of the capacitive pickup beam phase monitor discussed above. During the next year we expect to improve our ability to quickly configure the linac for new beams and reduce the time required for linac tuning. Already the time required for linac tuning as a percentage of research hours has decreased from 22% in FY 1993 to 15% in the first quarter of FY 1995.

  12. Analysis of High Order Modes in 1.3 GHZ CW SRF Electron Linac for a Light Source

    SciTech Connect

    Sukhanov, A.; Vostrikov, A.; Yakovlev, V.

    2013-01-01

    Design of a Light Source (LS) based on the continuous wave superconducting RF (CW SRF) electron linac is currently underway. This facility will provide soft coherent X-ray radiation for a braod spectrum of basic research applications. Quality of the X-ray laser radiation is affected by the electron beam parameters such as the stability of the transverse beam position and longitudinal and transverse beam emittances. High order modes (HOMs) excited in the SRF structures by a passing beam may deteriorate the beam quality and affect the beam stability. Deposition of HOM energy in the walls of SRF cavities adds to the heat load of he cryogenic system and leads to the increased cost of building and operation of the linac. In this paper we evaluate effects of HOMs in an LS CW SRF linac based on Tesla-type 9-cell 1.3 GHz cavities. We analyze non-coherent losses and resonance excitation of HOMs. We estimate heat load due to the very high frequency HOMs. We study influence of the HOMs on the transverse beam dynamics.

  13. A THz spectrometer combining the free electron laser FLARE with 33 T magnetic fields

    NASA Astrophysics Data System (ADS)

    Ozerov, M.; Bernáth, B.; Kamenskyi, D.; Redlich, B.; van der Meer, A. F. G.; Christianen, P. C. M.; Engelkamp, H.; Maan, J. C.

    2017-02-01

    The free electron laser Free electron Laser for Advanced spectroscopy and high Resolution Experiments (FLARE) at the FELIX Laboratory generates powerful radiation in the frequency range of 0.3-3 THz. This light, in combination with 33 T Bitter magnets at the High Field Magnet Laboratory, provides the unique opportunity to perform THz magneto spectroscopy with light intensities many orders of magnitude higher than provided by conventional sources. The performance of the THz spectrometer is measured via high-field electron spin resonance (ESR) in the paramagnetic benchmark system 2,2-diphenyl-1-picrylhydrazyl (DPPH). The narrow ESR linewidth of DPPH allows us to resolve a fine structure with 3 GHz spacing, demonstrating a considerable coherence of the individual THz micropulses of FLARE. The spectral resolution Δ ν / ν is better than 0.1%, which is an order of magnitude higher than typical values for a rf-linac based free electron laser. The observed coherence of the high power THz micropulses is a prerequisite for resonant control of matter, such as THz electron spin echo spectroscopy.

  14. Reirradiation Tolerance of the Human Brain

    SciTech Connect

    Mayer, Ramona; Sminia, Peter

    2008-04-01

    Purpose: To give an overview of current available clinical data on reirradiation of glioma with respect to the tolerance dose of normal brain tissue. Methods and Materials: Clinical brain reirradiation studies from January 1996 to December 2006 were considered on radiation-induced late adverse effects-i.e., brain tissue necrosis. The studies were analyzed by using the linear quadratic model to derive information on the cumulative biologic effective tolerance dose and equivalent doses in 2-Gy fractions for the healthy human brain. Results: The cumulative dose in conventional reirradiation series (of 81.6-101.9 Gy) were generally lower than in fractionated stereotactic radiotherapy (FSRT) ( 90-133.9 Gy.) or LINAC-based stereotactic radiosurgery series (of 111.6-137.2 Gy). No correlation between the time interval between the initial and reirradiation course and the incidence of radionecrosis was noted. The analysis showed the prescribed to increase with decreasing treatment volume, which is allowed by modern conformal radiation techniques. Conclusion: Radiation-induced normal brain tissue necrosis is found to occur at >100 Gy. The applied reirradiation dose and increases with a change in irradiation technique from conventional to radiosurgery re-treatment, without increasing the probability of normal brain necrosis. Taken together, modern conformal treatment