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Sample records for dosimetric mapping dosmap

  1. Dosimetric mapping inside biorack (7-IML-1)

    NASA Technical Reports Server (NTRS)

    Reitz, G.

    1992-01-01

    This experiment documents the radiation environment inside Biorack and compares it to theoretical predictions. Other experiments inside Biorack need this information to determine whether changes to samples are caused by radiation or microgravity. Dosimetric stacks, each with 20 to 100 sheets of plastic detector foils (cellulose nitrate, Lexan, and CR39) and nuclear emulsions of different radiation sensitivity are packed together with Thermoluminescence dosimeters (TLD) inside Type 1 containers. Crew members place two stacks in the 37 C incubator and four in the 36 C incubator, two of which are placed on the 1 g centrifuge. Two stacks are located in a stowage position at ambient temperature. After the mission, the plastic detectors are etched and the nuclear emulsions are developed similar to photographic emulsions. The traces resulting from the interaction of heavy ions with matter can then be evaluated under the microscope. The number, charge, and energy of the particles will be determined. From the TLD readings, the absorbed dose of the low LET components will be received.

  2. ISS Radiation Measurements using the Dosimetric Mapping Experiment

    NASA Astrophysics Data System (ADS)

    Reitz, G.; Beaujean, R.; Dachev, T.; Deme, S.; Luszik-Bhadra, M.; Heinrich, W.; Olko, P.; Scherkenbach, M.

    The experiment SDosimetric MappingT was flown as part of the Human Research Facility (HRF), NASASs first science payload on the ISS. The experiment consists of five nuclear track detector packages (NTDPs) (thermoluminescence dosimeters (TLD) and plastic nuclear track detectors), two DOSimetry TELescopes (DOSTEL) using two passive implanted planar silicon detectors per instrument, four Mobile Dosimetry Units (MDUs) using one passive implanted planar silicon detector per unit with an Control and Interface Unit (CIU) and an onboard TLD system consisting of a small weight TLD Reader and twelve TLD-bulbs, which have been reused after each mea- surement. Detectors are spread over the whole US-Lab. Data were transferred during the mission via the HRF Laptop to the ground. Dose rates of the ionizing part of the radiation field measured with TLD-bulbs at different locations vary between 123μGy/d and 226 μG/d. The dose rate received by the active devices fits excellent to the TLD measurements and is significantly lower compared to measurements on the STS missions to MIR. The measurements on the ISS yielded a mean dose equivalent of 504 μSv/day applying a radiation quality factor of 2.6 based on the recommendations of ICRP Report No. 60 and determined from the measured LET spectra of the DOSTEL instrument. The mean dose rate was with 194 μGy/d significantly lower compared to DOSTEL measurements on the STS missions. DOSTEL measurements were also obtained during the Solar Particle Event (SPE) on April 15, 2001. The presentation includes beside first results, some data on calibration work and an intercomparison between the different detector systems.

  3. Space radiation measurements on-board ISS--the DOSMAP experiment.

    PubMed

    Reitz, G; Beaujean, R; Benton, E; Burmeister, S; Dachev, Ts; Deme, S; Luszik-Bhadra, M; Olko, P

    2005-01-01

    The experiment 'Dosimetric Mapping' conducted as part of the science program of NASA's Human Research Facility (HRF) between March and August 2001 was designed to measure integrated total absorbed doses (ionising radiation and neutrons), heavy ion fluxes and its energy, mass and linear energy transfer (LET) spectra, time-dependent count rates of charged particles and their corresponding dose rates at different locations inside the US Lab at the International Space Station. Owing to the variety of particles and energies, a dosimetry package consisting of thermoluminescence dosemeter (TLD) chips and nuclear track detectors with and without converters (NTDPs), a silicon dosimetry telescope (DOSTEL), four mobile silicon detector units (MDUs) and a TLD reader unit (PILLE) with 12 TLD bulbs as dosemeters was used. Dose rates of the ionising part of the radiation field measured with TLD bulbs applying the PILLE readout system at different locations varied between 153 and 231 microGy d(-1). The dose rate received by the active devices fits excellent to the TLD measurements and is significantly lower compared with measurements for the Shuttle (STS) to MIR missions. The comparison of the absorbed doses from passive and active devices showed an agreement within +/- 10%. The DOSTEL measurements in the HRF location yielded a mean dose equivalent rate of 535 microSv d(-1). DOSTEL measurements were also obtained during the Solar Particle Event on 15 April 2001. PMID:16604663

  4. High spatial resolution dosimetric response maps for radiotherapy ionization chambers measured using kilovoltage synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Butler, D. J.; Stevenson, A. W.; Wright, T. E.; Harty, P. D.; Lehmann, J.; Livingstone, J.; Crosbie, J. C.

    2015-11-01

    Small circular beams of synchrotron radiation (0.1 mm and 0.4 mm in diameter) were used to irradiate ionization chambers of the types commonly used in radiotherapy. By scanning the chamber through the beam and measuring the ionization current, a spatial map of the dosimetric response of the chamber was recorded. The technique is able to distinguish contributions to the large-field ionization current from the chamber walls, central electrode and chamber stem. Scans were recorded for the NE 2571 Farmer chamber, the PTW 30013, IBA FC65-G Farmer-type chambers, the NE 2611A and IBA CC13 thimble chambers, the PTW 31006 and 31014 pinpoint chambers, the PTW Roos and Advanced Markus plane-parallel chambers, and the PTW 23342 thin-window soft x-ray chamber. In all cases, large contributions to the response arise from areas where the incident beam grazes the cavity surfaces. Quantitative as well as qualitative information about the relative chamber response was extracted from the maps, including the relative contribution of the central electrode. Line scans using monochromatic beams show the effect of the photon energy on the chamber response. For Farmer-type chambers, a simple Monte Carlo model was in good agreement with the measured response.

  5. High spatial resolution dosimetric response maps for radiotherapy ionization chambers measured using kilovoltage synchrotron radiation.

    PubMed

    Butler, D J; Stevenson, A W; Wright, T E; Harty, P D; Lehmann, J; Livingstone, J; Crosbie, J C

    2015-11-21

    Small circular beams of synchrotron radiation (0.1 mm and 0.4 mm in diameter) were used to irradiate ionization chambers of the types commonly used in radiotherapy. By scanning the chamber through the beam and measuring the ionization current, a spatial map of the dosimetric response of the chamber was recorded. The technique is able to distinguish contributions to the large-field ionization current from the chamber walls, central electrode and chamber stem. Scans were recorded for the NE 2571 Farmer chamber, the PTW 30013, IBA FC65-G Farmer-type chambers, the NE 2611A and IBA CC13 thimble chambers, the PTW 31006 and 31014 pinpoint chambers, the PTW Roos and Advanced Markus plane-parallel chambers, and the PTW 23342 thin-window soft x-ray chamber. In all cases, large contributions to the response arise from areas where the incident beam grazes the cavity surfaces. Quantitative as well as qualitative information about the relative chamber response was extracted from the maps, including the relative contribution of the central electrode. Line scans using monochromatic beams show the effect of the photon energy on the chamber response. For Farmer-type chambers, a simple Monte Carlo model was in good agreement with the measured response. PMID:26510214

  6. Direct dose mapping versus energy/mass transfer mapping for 4D dose accumulation: fundamental differences and dosimetric consequences

    NASA Astrophysics Data System (ADS)

    Li, Haisen S.; Zhong, Hualiang; Kim, Jinkoo; Glide-Hurst, Carri; Gulam, Misbah; Nurushev, Teamour S.; Chetty, Indrin J.

    2014-01-01

    The direct dose mapping (DDM) and energy/mass transfer (EMT) mapping are two essential algorithms for accumulating the dose from different anatomic phases to the reference phase when there is organ motion or tumor/tissue deformation during the delivery of radiation therapy. DDM is based on interpolation of the dose values from one dose grid to another and thus lacks rigor in defining the dose when there are multiple dose values mapped to one dose voxel in the reference phase due to tissue/tumor deformation. On the other hand, EMT counts the total energy and mass transferred to each voxel in the reference phase and calculates the dose by dividing the energy by mass. Therefore it is based on fundamentally sound physics principles. In this study, we implemented the two algorithms and integrated them within the Eclipse treatment planning system. We then compared the clinical dosimetric difference between the two algorithms for ten lung cancer patients receiving stereotactic radiosurgery treatment, by accumulating the delivered dose to the end-of-exhale (EE) phase. Specifically, the respiratory period was divided into ten phases and the dose to each phase was calculated and mapped to the EE phase and then accumulated. The displacement vector field generated by Demons-based registration of the source and reference images was used to transfer the dose and energy. The DDM and EMT algorithms produced noticeably different cumulative dose in the regions with sharp mass density variations and/or high dose gradients. For the planning target volume (PTV) and internal target volume (ITV) minimum dose, the difference was up to 11% and 4% respectively. This suggests that DDM might not be adequate for obtaining an accurate dose distribution of the cumulative plan, instead, EMT should be considered.

  7. SU-E-J-151: Dosimetric Evaluation of DIR Mapped Contours for Image Guided Adaptive Radiotherapy with 4D Cone-Beam CT

    SciTech Connect

    Balik, S; Weiss, E; Williamson, J; Hugo, G; Jan, N; Zhang, L; Roman, N; Christensen, G

    2014-06-01

    Purpose: To estimate dosimetric errors resulting from using contours deformably mapped from planning CT to 4D cone beam CT (CBCT) images for image-guided adaptive radiotherapy of locally advanced non-small cell lung cancer (NSCLC). Methods: Ten locally advanced non-small cell lung cancer (NSCLC) patients underwent one planning 4D fan-beam CT (4DFBCT) and weekly 4DCBCT scans. Multiple physicians delineated the gross tumor volume (GTV) and normal structures in planning CT images and only GTV in CBCT images. Manual contours were mapped from planning CT to CBCTs using small deformation, inverse consistent linear elastic (SICLE) algorithm for two scans in each patient. Two physicians reviewed and rated the DIR-mapped (auto) and manual GTV contours as clinically acceptable (CA), clinically acceptable after minor modification (CAMM) and unacceptable (CU). Mapped normal structures were visually inspected and corrected if necessary, and used to override tissue density for dose calculation. CTV (6mm expansion of GTV) and PTV (5mm expansion of CTV) were created. VMAT plans were generated using the DIR-mapped contours to deliver 66 Gy in 33 fractions with 95% and 100% coverage (V66) to PTV and CTV, respectively. Plan evaluation for V66 was based on manual PTV and CTV contours. Results: Mean PTV V66 was 84% (range 75% – 95%) and mean CTV V66 was 97% (range 93% – 100%) for CAMM scored plans (12 plans); and was 90% (range 80% – 95%) and 99% (range 95% – 100%) for CA scored plans (7 plans). The difference in V66 between CAMM and CA was significant for PTV (p = 0.03) and approached significance for CTV (p = 0.07). Conclusion: The quality of DIR-mapped contours directly impacted the plan quality for 4DCBCT-based adaptation. Larger safety margins may be needed when planning with auto contours for IGART with 4DCBCT images. Reseach was supported by NIH P01CA116602.

  8. Dosimetric audit in brachytherapy

    PubMed Central

    Bradley, D A; Nisbet, A

    2014-01-01

    Dosimetric audit is required for the improvement of patient safety in radiotherapy and to aid optimization of treatment. The reassurance that treatment is being delivered in line with accepted standards, that delivered doses are as prescribed and that quality improvement is enabled is as essential for brachytherapy as it is for the more commonly audited external beam radiotherapy. Dose measurement in brachytherapy is challenging owing to steep dose gradients and small scales, especially in the context of an audit. Several different approaches have been taken for audit measurement to date: thimble and well-type ionization chambers, thermoluminescent detectors, optically stimulated luminescence detectors, radiochromic film and alanine. In this work, we review all of the dosimetric brachytherapy audits that have been conducted in recent years, look at current audits in progress and propose required directions for brachytherapy dosimetric audit in the future. The concern over accurate source strength measurement may be essentially resolved with modern equipment and calibration methods, but brachytherapy is a rapidly developing field and dosimetric audit must keep pace. PMID:24807068

  9. Dosimetric adaptive IMRT driven by fiducial points

    SciTech Connect

    Crijns, Wouter; Van Herck, Hans; Defraene, Gilles; Van den Bergh, Laura; Haustermans, Karin; Slagmolen, Pieter; Maes, Frederik; Van den Heuvel, Frank

    2014-06-15

    Purpose: Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy have become standard treatments but are more sensitive to anatomical variations than 3D conformal techniques. To correct for inter- and intrafraction anatomical variations, fast and easy to implement methods are needed. Here, the authors propose a full dosimetric IMRT correction that finds a compromise in-between basic repositioning (the current clinical practice) and full replanning. It simplifies replanning by avoiding a recontouring step and a full dose calculation. It surpasses repositioning by updating the preoptimized fluence and monitor units (MU) using a limited number of fiducial points and a pretreatment (CB)CT. To adapt the fluence the fiducial points were projected in the beam's eye view (BEV). To adapt the MUs, point dose calculation towards the same fiducial points were performed. The proposed method is intrinsically fast and robust, and simple to understand for operators, because of the use of only four fiducial points and the beam data based point dose calculations. Methods: To perform our dosimetric adaptation, two fluence corrections in the BEV are combined with two MU correction steps along the beam's path. (1) A transformation of the fluence map such that it is realigned with the current target geometry. (2) A correction for an unintended scaling of the penumbra margin when the treatment beams scale to the current target size. (3) A correction for the target depth relative to the body contour and (4) a correction for the target distance to the source. The impact of the correction strategy and its individual components was evaluated by simulations on a virtual prostate phantom. This heterogeneous reference phantom was systematically subjected to population based prostate transformations to simulate interfraction variations. Additionally, a patient example illustrated the clinical practice. The correction strategy was evaluated using both dosimetric (CTV mean

  10. Mapping.

    ERIC Educational Resources Information Center

    Kinney, Douglas M.; McIntosh, Willard L.

    1979-01-01

    The area of geological mapping in the United States in 1978 increased greatly over that reported in 1977; state geological maps were added for California, Idaho, Nevada, and Alaska last year. (Author/BB)

  11. 3.2 Dosimetric Concepts

    NASA Astrophysics Data System (ADS)

    Kramer, H.-M.

    This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Section '3.2 Dosimetric Concepts' of the Chapter '3 Dosimetry in Diagnostic Radiology and Radiotherapy' with the contents:

  12. Developing and improving a scanning system for dosimetric applications

    SciTech Connect

    Perez, P.; Galvan, V.; Castellanoa, G.; Valente, M.

    2010-08-04

    Radiotherapy is nowadays one of the most used techniques for the treatment of different pathologies, particularly cancer diseases. The accuracy regarding the application of these treatments, which are planned according to patient information, depends mainly on the dosimetric measurements of absorbed dose within irradiated tissues. The present work is devoted to the study, design and construction of an original device capable of performing visible light transmission measurements in order to analyze Fricke gel dosimeters. Furthermore, a suitable bi-dimensional positioning system along with a dedicated control system and image processing software has been adapted to the dosimetric device in order to perform 2D dose mapping. The obtained results confirm the feasibility of the proposed method, therefore suggesting its potentiality for clinical applications.

  13. Dosimetric Characteristics for Brachytherapy Sources

    SciTech Connect

    DeWerd, Larry A.; Davis, Stephen D.

    2011-05-05

    Brachytherapy sources are characterized by the dosimetric parameters in a protocol such as the American Association of Physicists in Medicine Task Group 43. The air-kerma strength is measured and traceable to a primary standard. Then the parameters such as dose-rate constant, radial dose function, and anisotropy function are measured and related back to the primary standard. This is normally accomplished with thermoluminescent dosimeters (TLDs). Since radial dose function and anisotropy function are relative parameters, some of the dosimetric corrections are negligible. For the dose-rate constant, parameters such as the energy dependence compared with a calibration beam such as {sup 60}Co need to be accounted for. A description of the primary standard measurements and TLD measurements will be discussed.

  14. Dosimetric Characteristics for Brachytherapy Sources

    NASA Astrophysics Data System (ADS)

    DeWerd, Larry A.; Davis, Stephen D.

    2011-05-01

    Brachytherapy sources are characterized by the dosimetric parameters in a protocol such as the American Association of Physicists in Medicine Task Group 43. The air-kerma strength is measured and traceable to a primary standard. Then the parameters such as dose-rate constant, radial dose function, and anisotropy function are measured and related back to the primary standard. This is normally accomplished with thermoluminescent dosimeters (TLDs). Since radial dose function and anisotropy function are relative parameters, some of the dosimetric corrections are negligible. For the dose-rate constant, parameters such as the energy dependence compared with a calibration beam such as 60Co need to be accounted for. A description of the primary standard measurements and TLD measurements will be discussed.

  15. Dosimetric methodology of the ICRP

    SciTech Connect

    Eckerman, K.F.

    1994-12-31

    Establishment of guidance for the protection of workers and members of the public from radiation exposures necessitates estimation of the radiation dose to tissues of the body at risk. The dosimetric methodology formulated by the International Commission on Radiological Protection (ICRP) is intended to be responsive to this need. While developed for radiation protection, elements of the methodology are often applied in addressing other radiation issues; e.g., risk assessment. This chapter provides an overview of the methodology, discusses its recent extension to age-dependent considerations, and illustrates specific aspects of the methodology through a number of numerical examples.

  16. Dosimetric Predictors of Laryngeal Edema

    SciTech Connect

    Sanguineti, Giuseppe . E-mail: gisangui@utmb.edu; Adapala, Prashanth; Endres, Eugene J. C; Brack, Collin; Fiorino, Claudio; Sormani, Maria Pia; Parker, Brent

    2007-07-01

    Purpose: To investigate dosimetric predictors of laryngeal edema after radiotherapy (RT). Methods and Materials: A total of 66 patients were selected who had squamous cell carcinoma of the head and neck with grossly uninvolved larynx at the time of RT, no prior major surgical operation except for neck dissection and tonsillectomy, treatment planning data available for analysis, and at least one fiberoptic examination of the larynx within 2 years from RT performed by a single observer. Both the biologically equivalent mean dose at 2 Gy per fraction and the cumulative biologic dose-volume histogram of the larynx were extracted for each patient. Laryngeal edema was prospectively scored after treatment. Time to endpoint, moderate or worse laryngeal edema (Radiation Therapy Oncology Group Grade 2+), was calculated with log rank test from the date of treatment end. Results: At a median follow-up of 17.1 months (range, 0.4- 50.0 months), the risk of Grade 2+ edema was 58.9% {+-} 7%. Mean dose to the larynx, V30, V40, V50, V60, and V70 were significantly correlated with Grade 2+ edema at univariate analysis. At multivariate analysis, mean laryngeal dose (continuum, hazard ratio, 1.11; 95% confidence interval, 1.06-1.15; p < 0.001), and positive neck stage at RT (N0-x vs. N +, hazard ratio, 3.66; 95% confidence interval, 1.40-9.58; p = 0.008) were the only independent predictors. Further stratification showed that, to minimize the risk of Grade 2+ edema, the mean dose to the larynx has to be kept {<=}43.5 Gy at 2 Gy per fraction. Conclusion: Laryngeal edema is strictly correlated with various dosimetric parameters; mean dose to the larynx should be kept {<=}43.5 Gy.

  17. Practical simplifications for radioimmunotherapy dosimetric models

    SciTech Connect

    Shen, S.; DeNardo, G.L.; O`Donnell, R.T.; Yuan, A.; DeNardo, D.A.; Macey, D.J.; DeNardo, S.J.

    1999-01-01

    Radiation dosimetry is potentially useful for assessment and prediction of efficacy and toxicity for radionuclide therapy. The usefulness of these dose estimates relies on the establishment of a dose-response model using accurate pharmacokinetic data and a radiation dosimetric model. Due to the complexity in radiation dose estimation, many practical simplifications have been introduced in the dosimetric modeling for clinical trials of radioimmunotherapy. Although research efforts are generally needed to improve the simplifications used at each stage of model development, practical simplifications are often possible for specific applications without significant consequences to the dose-response model. In the development of dosimetric methods for radioimmunotherapy, practical simplifications in the dosimetric models were introduced. This study evaluated the magnitude of uncertainty associated with practical simplifications for: (1) organ mass of the MIRD phantom; (2) radiation contribution from target alone; (3) interpolation of S value; (4) macroscopic tumor uniformity; and (5) fit of tumor pharmacokinetic data.

  18. Dosimetric Characteristics of a Two-Dimensional Diode Array Detector Irradiated with Passively Scattered Proton Beams

    PubMed Central

    Liengsawangwong, Praimakorn; Sahoo, Nanayan; Ding, Xiaoning; Lii, MingFwu; Gillin, Michale T.; Zhu, Xiaorong Ronald

    2015-01-01

    Purpose: To evaluate the dosimetric characteristics of a two-dimensional (2D) diode array detector irradiated with passively scattered proton beams. Materials and Methods: A diode array detector, MapCHECK (Model 1175, Sun Nuclear, Melbourne, FL, USA) was characterized in passive-scattered proton beams. The relative sensitivity of the diodes and absolute dose calibration were determined using a 250 MeV beam. The pristine Bragg curves (PBCs) measured by MapCHECK diodes were compared with those of an ion chamber using a range shift method. The water-equivalent thickness (WET) of the diode array detector’s intrinsic buildup also was determined. The inverse square dependence, linearity, and other proton dosimetric quantities measured by MapCHECK were also compared with those of the ion chambers. The change in the absolute dose response of the MapCHECK as a function of accumulated radiation dose was used as an indicator of radiation damage to the diodes. 2D dose distribution with and without the compensator were measured and compared with the treatment planning system (TPS) calculations. Results: The WET of the MapCHECK diode’s buildup was determined to be 1.7 cm. The MapCHECK-measured PBC were virtually identical to those measured by a parallel-plate ion chamber for 160, 180, and 250 MeV proton beams. The inverse square results of the MapCHECK were within ±0.4% of the ion chamber results. The linearity of MapCHECK results was within 1% of those from the ion chamber as measured in the range between 10 and 300 MU. All other dosimetric quantities were within 1.3% of the ion chamber results. The 2D dose distributions for non-clinical fields without compensator and the patient treatment fields with the compensator were consistent with the TPS results. The absolute dose response of the MapCHECK was changed by 7.4% after an accumulated dose increased by 170 Gy. Conclusions: The MapCHECK is a convenient and useful tool for 2D dose distribution measurements using passively

  19. Hot pixel generation in active pixel sensors: dosimetric and micro-dosimetric response

    NASA Technical Reports Server (NTRS)

    Scheick, Leif; Novak, Frank

    2003-01-01

    The dosimetric response of an active pixel sensor is analyzed. heavy ions are seen to damage the pixel in much the same way as gamma radiation. The probability of a hot pixel is seen to exhibit behavior that is not typical with other microdose effects.

  20. A high sensitive phosphor for dosimetric applications

    NASA Astrophysics Data System (ADS)

    Kore, Bhushan P.; Dhoble, N. S.; Lochab, S. P.; Dhoble, S. J.

    2015-06-01

    In this study a novel TL phosphor CaMg3(SO4)4:Dy3+ was prepared by acid distillation method. The TL response of this phosphor towards γ-rays and carbon ion beam was tested. Good dosimetric glow curve was observed which is stable against both the type of radiations. The CaMg3(SO4)4:Dy3+ phosphor doped with 0.2 mol% of Dy3+, irradiated with γ-ray shows nearly equal sensitivity to that of commercially available CaSO4:Dy TLD phosphor whereas 3.5 times more sensitivity than CaSO4:Dy, when irradiated with carbon ion beam. The change in glow peak intensities and glow peak temperature with variation in irradiation species and energy of ion beam is discussed here. The effect of these on trapping parameters is also illustrated.

  1. Dosimetric investigations on Mars-96 mission

    NASA Astrophysics Data System (ADS)

    Semkova, J.; Dachev, Ts.; Matviichuk, Yu.; Koleva, R.; Tomov, B.; Baynov, P.; Petrov, V.; Nguyen, V.; Siegrist, M.; Chene, J.

    1994-10-01

    The dosimetric experiments Dose-M and Liulin as part of the more complex French-German-Bulgarian-Russian experiments for the investigation of the radiation environment for Mars-96 mission are described. The experiments will be realized with dosemeter-radiometer instruments, measuring absorbed dose in semiconductor detectors and the particle flux. Two detectors will be mounted on board the Mars-96 orbiter. Another detector will be on the guiderope of the Mars-96 Aerostate station. The scientific aims of Dose-M and Liulin experiments are: Analysis of the absorbed dose and the flux on the path and around Mars behind different shielding. Study of the shielding characteristics of the Martian atmosphere from galactic and solar cosmic rays including solar proton events. Together with the French gamma-spectrometer and the German neutron detectors the investigation of the radiation environment on the surface of Mars and in the atmosphere up to 4000 m altitude will be conducted.

  2. Dosimetric Consequences of Intrafraction Prostate Motion

    SciTech Connect

    Li, Haisen S. Chetty, Indrin J.; Enke, Charles A.; Foster, Ryan D.; Willoughby, Twyla R.; Kupellian, Patrick A.; Solberg, Timothy D.

    2008-07-01

    Purpose: To analyze characteristics of intrafraction prostate motion, monitored using the Calypso system, and investigate dosimetric consequences of the motion for different clinical target volume (CTV) to planning target volume (PTV) margins. Methods and Materials: Motion characteristics were analyzed for 1,267 tracking sessions and 35 patients. Using prostate-PTV margins of 0, 1, 2, 3, and 5 mm, dose metrics for the prostate gland, bladder, and rectum were evaluated for scenarios including patient population, individual patients showing the greatest motion during the course of treatment, and the individual session with the largest overall movement. Composite dose distributions incorporating motion blurring were calculated by convolving static intensity-modulated radiotherapy plans with corresponding motion probability functions. Results: For prostate-PTV margins of 2 mm or greater, intrafraction motion did not compromise prostate dose coverage for either the patient population or individual patients. For the patient showing the largest overall movement, the prostate equivalent uniform dose was reduced by only 17.4 cGy (0.23%), and the minimum prostate dose remained greater than 95% of the nominal dose. For margins less than 2 mm, the prostate dose-volume histogram in the same patient was slightly compromised, and the equivalent uniform dose was reduced by 38.5 cGy (0.51%). Sparing of the bladder and rectum was improved substantially by reducing margins. Conclusions: Although significant motion can be observed during individual fractions, the dosimetric consequences are insignificant during a typical course of radiotherapy (30-40 fractions) with CTV-PTV margins of 2 mm or greater provided that the Calypso system is applied for pretreatment localization. Further reduction of the margin is possible if intrafraction realignment is performed.

  3. Dosimetric measurements of an n-butyl cyanoacrylate embolization material for arteriovenous malformations

    SciTech Connect

    Labby, Zacariah E.; Chaudhary, Neeraj; Gemmete, Joseph J.; Pandey, Aditya S.; Roberts, Donald A.

    2015-04-15

    Purpose: The therapeutic regimen for cranial arteriovenous malformations often involves both stereotactic radiosurgery and endovascular embolization. Embolization agents may contain tantalum or other contrast agents to assist the neurointerventionalists, leading to concerns regarding the dosimetric effects of these agents. This study investigated dosimetric properties of n-butyl cyanoacrylate (n-BCA) plus lipiodol with and without tantalum powder. Methods: The embolization agents were provided cured from the manufacturer with and without added tantalum. Attenuation measurements were made for the samples and compared to the attenuation of a solid water substitute using a 6 MV photon beam. Effective linear attenuation coefficients (ELAC) were derived from attenuation measurements made using a portal imager and derived sample thickness maps projected in an identical geometry. Probable dosimetric errors for calculations in which the embolized regions are overridden with the properties of water were calculated using the ELAC values. Interface effects were investigated using a parallel plate ion chamber placed at set distances below fixed samples. Finally, Hounsfield units (HU) were measured using a stereotactic radiosurgery CT protocol, and more appropriate HU values were derived from the ELAC results and the CT scanner’s HU calibration curve. Results: The ELAC was 0.0516 ± 0.0063 cm{sup −1} and 0.0580 ± 0.0091 cm{sup −1} for n-BCA without and with tantalum, respectively, compared to 0.0487 ± 0.0009 cm{sup −1} for the water substitute. Dose calculations with the embolized region set to be water equivalent in the treatment planning system would result in errors of −0.29% and −0.93% per cm thickness of n-BCA without and with tantalum, respectively. Interface effects compared to water were small in magnitude and limited in distance for both embolization materials. CT values at 120 kVp were 2082 and 2358 HU for n-BCA without and with tantalum, respectively

  4. Statistical process control for IMRT dosimetric verification

    SciTech Connect

    Breen, Stephen L.; Moseley, Douglas J.; Zhang, Beibei; Sharpe, Michael B.

    2008-10-15

    Patient-specific measurements are typically used to validate the dosimetry of intensity-modulated radiotherapy (IMRT). To evaluate the dosimetric performance over time of our IMRT process, we have used statistical process control (SPC) concepts to analyze the measurements from 330 head and neck (H and N) treatment plans. The objectives of the present work are to: (i) Review the dosimetric measurements of a large series of consecutive head and neck treatment plans to better understand appropriate dosimetric tolerances; (ii) analyze the results with SPC to develop action levels for measured discrepancies; (iii) develop estimates for the number of measurements that are required to describe IMRT dosimetry in the clinical setting; and (iv) evaluate with SPC a new beam model in our planning system. H and N IMRT cases were planned with the PINNACLE{sup 3} treatment planning system versions 6.2b or 7.6c (Philips Medical Systems, Madison, WI) and treated on Varian (Palo Alto, CA) or Elekta (Crawley, UK) linacs. As part of regular quality assurance, plans were recalculated on a 20-cm-diam cylindrical phantom, and ion chamber measurements were made in high-dose volumes (the PTV with highest dose) and in low-dose volumes (spinal cord organ-at-risk, OR). Differences between the planned and measured doses were recorded as a percentage of the planned dose. Differences were stable over time. Measurements with PINNACLE{sup 3} 6.2b and Varian linacs showed a mean difference of 0.6% for PTVs (n=149, range, -4.3% to 6.6%), while OR measurements showed a larger systematic discrepancy (mean 4.5%, range -4.5% to 16.3%) that was due to well-known limitations of the MLC model in the earlier version of the planning system. Measurements with PINNACLE{sup 3} 7.6c and Varian linacs demonstrated a mean difference of 0.2% for PTVs (n=160, range, -3.0%, to 5.0%) and -1.0% for ORs (range -5.8% to 4.4%). The capability index (ratio of specification range to range of the data) was 1.3 for the PTV

  5. Statistical process control for IMRT dosimetric verification.

    PubMed

    Breen, Stephen L; Moseley, Douglas J; Zhang, Beibei; Sharpe, Michael B

    2008-10-01

    Patient-specific measurements are typically used to validate the dosimetry of intensity-modulated radiotherapy (IMRT). To evaluate the dosimetric performance over time of our IMRT process, we have used statistical process control (SPC) concepts to analyze the measurements from 330 head and neck (H&N) treatment plans. The objectives of the present work are to: (i) Review the dosimetric measurements of a large series of consecutive head and neck treatment plans to better understand appropriate dosimetric tolerances; (ii) analyze the results with SPC to develop action levels for measured discrepancies; (iii) develop estimates for the number of measurements that are required to describe IMRT dosimetry in the clinical setting; and (iv) evaluate with SPC a new beam model in our planning system. H&N IMRT cases were planned with the PINNACLE treatment planning system versions 6.2b or 7.6c (Philips Medical Systems, Madison, WI) and treated on Varian (Palo Alto, CA) or Elekta (Crawley, UK) linacs. As part of regular quality assurance, plans were recalculated on a 20-cm-diam cylindrical phantom, and ion chamber measurements were made in high-dose volumes (the PTV with highest dose) and in low-dose volumes (spinal cord organ-at-risk, OR). Differences between the planned and measured doses were recorded as a percentage of the planned dose. Differences were stable over time. Measurements with PINNACLE3 6.2b and Varian linacs showed a mean difference of 0.6% for PTVs (n=149, range, -4.3% to 6.6%), while OR measurements showed a larger systematic discrepancy (mean 4.5%, range -4.5% to 16.3%) that was due to well-known limitations of the MLC model in the earlier version of the planning system. Measurements with PINNACLE3 7.6c and Varian linacs demonstrated a mean difference of 0.2% for PTVs (n=160, range, -3.0%, to 5.0%) and -1.0% for ORs (range -5.8% to 4.4%). The capability index (ratio of specification range to range of the data) was 1.3 for the PTV data, indicating that almost

  6. Dosimetric evaluation of brain scanning agents

    SciTech Connect

    Eckerman, K.F.; Cristy, M.; Warner, G.G.

    1981-06-01

    Conventional radiopharmaceuticals used for scanning the brain are excluded from normal brain tissue by the presence of an intact blood-brain-barrier (BBB). The current generation of radiopharmaceuticals being developed is capable of crossing the intact BBB thus providing direct measurement of brain function. The dosimetry of the first generation agents is complicated by the presence of the BBB which prevents the agent from achieving uniform distribution as generally assumed in dosimetric evaluation. The second generation radiopharmaceuticals while crossing the BBB are also nonuniformly distributed in the brain. Tabulations of specific absorbed fraction data for photon emitters uniformly distributed in the gray and in the white matter regions of the brain are presented and compared to values for a uniform distribution throughout the brain. Estimates of the specific absorbed fraction for the lens of the eye and the pituitary gland are also presented. Dose values per unit cumulated activity (S-factors) are developed based on the specific absorbed fraction data. The significance of the positron component to the dose to the regions of the brain is indicated for second generation scanning agents containing carbon-11, nitrogen-13, oxygen-15, and fluorine-18.

  7. A high sensitive phosphor for dosimetric applications

    SciTech Connect

    Kore, Bhushan P. Dhoble, S. J.; Dhoble, N. S.; Lochab, S. P.

    2015-06-24

    In this study a novel TL phosphor CaMg{sub 3}(SO{sub 4}){sub 4}:Dy{sup 3+} was prepared by acid distillation method. The TL response of this phosphor towards γ-rays and carbon ion beam was tested. Good dosimetric glow curve was observed which is stable against both the type of radiations. The CaMg{sub 3}(SO{sub 4}){sub 4}:Dy{sup 3+} phosphor doped with 0.2 mol% of Dy{sup 3+}, irradiated with γ-ray shows nearly equal sensitivity to that of commercially available CaSO{sub 4}:Dy TLD phosphor whereas 3.5 times more sensitivity than CaSO{sub 4}:Dy, when irradiated with carbon ion beam. The change in glow peak intensities and glow peak temperature with variation in irradiation species and energy of ion beam is discussed here. The effect of these on trapping parameters is also illustrated.

  8. Experiment "Seeds" on Biokosmos 9. Dosimetric part.

    PubMed

    Baican, B; Schopper, E; Wendnagel, T h; Schott, J U; Heilman, C

    1992-01-01

    The aim of the experiment "Seeds" on the Sowjetic satellite Biokosmos 9 was the observation of mutagenic effects caused at special loci of seeds of Arabidopsis thaliana and assigned to particles of the Cosmic radiation. Two types of exposure units were flown: A low-shielding unit Type I, mounted at the surface of the satellite (1.4 g/cm2 shielding) and, for comparison, an identical item inside (16 g/cm2 shielding), using nuclear emulsion as track detectors. A Type II unit, flown inside (18g/cm2 shielding) was mounted with AgCl track detectors. The layout will be briefly described. A first set of dosimetric data from the physical evaluation of the experiment will be presented. The subdivision into charge- and LET-groups shows a rather high contribution of the intermediate LET-group (350-1000 MeV/cm) due to medium heavy particles (Z = 6-10) and to enders of light (p, alpha) particles. PMID:11537029

  9. Phantom size in brachytherapy source dosimetric studies.

    PubMed

    Pérez-Calatayud, J; Granero, D; Ballester, F

    2004-07-01

    An important point to consider in a brachytherapy dosimetry study is the phantom size involved in calculations or experimental measurements. As pointed out by Williamson [Med. Phys. 18, 776-786 (1991)] this topic has a relevant influence on final dosimetric results. Presently, one-dimensional (1-D) algorithms and newly-developed 3-D correction algorithms are based on physics data that are obtained under full scatter conditions, i.e., assumed infinite phantom size. One can then assume that reference dose distributions in source dosimetry for photon brachytherapy should use an unbounded phantom size rather than phantom-like dimensions. Our aim in this paper is to study the effect of phantom size on brachytherapy for radionuclide 137Cs, 192Ir, 125I and 103Pd, mainly used for clinical purposes. Using the GEANT4 Monte Carlo code, we can ascertain effects on derived dosimetry parameters and functions to establish a distance dependent difference due to the absence of full scatter conditions. We have found that for 137Cs and 192Ir, a spherical phantom with a 40 cm radius is the equivalent of an unbounded phantom up to a distance of 20 cm from the source, as this size ensures full scatter conditions at this distance. For 125I and 103Pd, the required radius for the spherical phantom in order to ensure full scatter conditions at 10 cm from the source is R = 15 cm. A simple expression based on fits of the dose distributions for various phantom sizes has been developed for 137Cs and 192Ir in order to compare the dose rate distributions published for different phantom sizes. Using these relations it is possible to obtain radial dose functions for unbounded medium from bounded phantom ones. PMID:15305460

  10. Dosimetric properties of new europium doped KBr phosphors

    NASA Astrophysics Data System (ADS)

    Bernal, R.; Tostado-García, W.; Alday-Samaniego, K. R.; Cruz-Vázquez, C.; Barboza-Flores, M.

    2003-03-01

    In this work, dosimetric properties of new sintered europium-doped KBr phosphors subjected to beta irradiation are investigated. The obtained results show that these phosphors exhibit promising thermoluminescence properties that made them a viable alternative to substitute the conventional alkali halides crystals of similar composition for dosimetric purposes, considering as important advantages the simplicity and economy of the fabrication. The thermoluminescence response shows a linear dose dependence up to order of some Grays, which is higher than the linearity presented by the crystals of similar composition. Also, the thermoluminiscence fading is stabilized faster than that of the crystals do.

  11. Electromagnetic and Thermal Dosimetric Techniques in Humans and its Application

    NASA Astrophysics Data System (ADS)

    Hirata, Akimasa; Fujiwara, Osamu

    There has been increasing public concern about the adverse health effects of human exposure to radio frequency fields. Radio frequency fields are also used for medical application. This paper reviews electromagnetic and thermal computational dosimetric techniques, which has been developed by the authors. The feature of the thermal dosimetric method is that body core temperature can be computed reasonably unlike conventional method. This scheme is particularly useful for intense localized or whole-body electromagnetic wave exposure. Computational examples are shown to verify the effectiveness of the proposal.

  12. Dosimetric accuracy of Kodak EDR2 film for IMRT verifications.

    PubMed

    Childress, Nathan L; Salehpour, Mohammad; Dong, Lei; Bloch, Charles; White, R Allen; Rosen, Isaac I

    2005-02-01

    Patient-specific intensity-modulated radiotherapy (IMRT) verifications require an accurate two-dimensional dosimeter that is not labor-intensive. We assessed the precision and reproducibility of film calibrations over time, measured the elemental composition of the film, measured the intermittency effect, and measured the dosimetric accuracy and reproducibility of calibrated Kodak EDR2 film for single-beam verifications in a solid water phantom and for full-plan verifications in a Rexolite phantom. Repeated measurements of the film sensitometric curve in a single experiment yielded overall uncertainties in dose of 2.1% local and 0.8% relative to 300 cGy. 547 film calibrations over an 18-month period, exposed to a range of doses from 0 to a maximum of 240 MU or 360 MU and using 6 MV or 18 MV energies, had optical density (OD) standard deviations that were 7%-15% of their average values. This indicates that daily film calibrations are essential when EDR2 film is used to obtain absolute dose results. An elemental analysis of EDR2 film revealed that it contains 60% as much silver and 20% as much bromine as Kodak XV2 film. EDR2 film also has an unusual 1.69:1 silver:halide molar ratio, compared with the XV2 film's 1.02:1 ratio, which may affect its chemical reactions. To test EDR2's intermittency effect, the OD generated by a single 300 MU exposure was compared to the ODs generated by exposing the film 1 MU, 2 MU, and 4 MU at a time to a total of 300 MU. An ion chamber recorded the relative dose of all intermittency measurements to account for machine output variations. Using small MU bursts to expose the film resulted in delivery times of 4 to 14 minutes and lowered the film's OD by approximately 2% for both 6 and 18 MV beams. This effect may result in EDR2 film underestimating absolute doses for patient verifications that require long delivery times. After using a calibration to convert EDR2 film's OD to dose values, film measurements agreed within 2% relative

  13. Incorporating breath holding and image guidance in the adjuvant gastric cancer radiotherapy: a dosimetric study

    PubMed Central

    2012-01-01

    Background The respiratory related target motion and setup error will lead to a large margin in the gastric radiotherapy. The purpose of this study is to investigate the dosimetric benefit and the possibility of incorporating the breath-hold (BH) technique with online image-guided radiotherapy in the adjuvant gastric cancer radiotherapy. Methods Setup errors and target motions of 22 post-operative gastric cancer patients with surgical clips were analyzed. Clips movement was recorded using the digital fluoroscopics and the probability distribution functions (pdf) of the target motions were created for both the free breathing (FB) and BH treatment. For dosimetric comparisons, two intensity-modulated radiotherapy (IMRT) treatment plans, i.e. the free breathing treatment plan (IMRTFB) and the image-guided BH treatment plan (IMRTIGBH) using the same beam parameters were performed among 6 randomly selected patients. Different margins for FB and BH plans were derived. The plan dose map was convoluted with various pdfs of the setup errors and the target motions. Target coverage and dose to organs at risk were compared and the dose-escalation probability was assessed. Results The mean setup errors were 1.2 mm in the superior-inferior (SI), 0.0 mm in the left-right (LR), and 1.4 mm in the anterior-posterior (AP) directions. The mean target motion for the free breathing (vs. BH) was 11.1 mm (vs. 2.2 mm), 1.9 mm (vs. 1.1 mm), and 5.5 mm (vs. 1.7 mm) in the SI, LR, and AP direction, respectively. The target coverage was comparable for all the original plans. IMRTIGBH showed lower dose to the liver compared with IMRTFB (p = 0.01) but no significant difference in the kidneys. Convolved IMRTIGBH showed better sparing in kidneys (p < 0.01) and similar in liver (p = 0.08). Conclusions Combining BH technique with online image guided IMRT can minimize the organ motion and improve the setup accuracy. The dosimetric comparison showed the dose could be

  14. Impact of cutout off axis on electron beam dosimetric parameters.

    PubMed

    Arunkumar, T; Supe, S S; Ravikumar, M; Sathiyan, S; Ganesh, K M

    2012-04-01

    Dosimetric changes caused by the positional uncertainty of centering a small electron cutout to the machine central axis (CAX) of the linear accelerator (linac) were investigated. Six circular cutouts with 4 cm diameter were made with their centres shifted off by 0, 2, 4, 6, 8 and 10 mm from the machine CAX. The 6 x 6 cm(2) electron applicator was used for the measurement. The percentage depth doses (PDDs) were measured at the Machine CAX and also with respect to cutout centre for 6, 9, 12, 16 and 20 MeV electron beams. The in-line and cross-line profiles were measured at the depth of maximum dose (R100). The relative output factor (ROF) was measured at the reference depth. All the measurements were made at nominal source to surface distance (100 cm SSD) as well as at extended SSDs (100, 102, 106 and 110 cm). When the cutout centre was shifted away from the machine CAX for low energy beams the depth of 100% dose (R(100)), the depth of 90% dose (R(90)) and the depth of 80% dose (R(80)) had no significant change. For higher energies (>9 MeV) there was a reduction in these dosimetric parameters. The isodose coverage of the in-line and cross-line profile was reduced when the cutout centre was shifted away from the machine CAX. At extended SSDs the dosimetric changes are only because of geometric divergence of the beam and not by the positional uncertainty of the cutout. It is important for the radiation oncologist, dosimetrist, therapist and physicist to note such dosimetric changes while using the electron beam to the patients. PMID:22335408

  15. Proton Radiotherapy for Liver Tumors: Dosimetric Advantages Over Photon Plans

    SciTech Connect

    Wang Xiaochun Krishnan, Sunil; Zhang Xiaodong; Dong Lei; Briere, Tina; Crane, Christopher H.; Martel, Mary; Gillin, Michael; Mohan, Radhe; Beddar, Sam

    2008-01-01

    The purpose of the study is to dosimetrically investigate the advantages of proton radiotherapy over photon radiotherapy for liver tumors. The proton plan and the photon plan were designed using commercial treatment planning systems. The treatment target dose conformity and heterogeneity and dose-volume analyses of normal structures were compared between proton and photon radiotherapy for 9 patients with liver tumors. Proton radiotherapy delivered a more conformal target dose with slightly less homogeneity when compared with photon radiotherapy. Protons significantly reduced the fractional volume of liver receiving dose greater or equal to 30 Gy (V{sub 30}) and the mean liver dose. The stomach and duodenal V{sub 45} were significantly lower with the use of proton radiotherapy. The V{sub 40} and V{sub 50} of the heart and the maximum spinal cord dose were also significantly lower with the use of proton radiotherapy. Protons were better able to spare one kidney completely and deliver less dose to one (generally the left) kidney than photons. The mean dose to the total body and most critical structures was significantly decreased using protons when compared to corresponding photon plans. In conclusion, our study suggests the dosimetric benefits of proton radiotherapy over photon radiotherapy. These dosimetric advantages of proton plans may permit further dose escalation with lower risk of complications.

  16. Dosimetric Effects of Setup Uncertainties on Breast Treatment Delivery

    SciTech Connect

    Harron, Elizabeth Christine McCallum, Hazel Mhairi; Lambert, Elizabeth Lyn; Lee, Daniela; Lambert, Geoffrey David

    2008-01-01

    This study aimed to assess the dosimetric impact of setup errors during the delivery of radiotherapy to the breast, and use this information to make recommendations on intervention tolerances for portal imaging of breast treatments. Translational and rotational setup errors were simulated for 10 recent breast patients using an Oncentra MasterPlan treatment planning system. The effect of these errors on the breast and tumor bed target volumes receiving 95% and 107% of the prescribed dose were assessed. For the majority of patients, shifts of up to 10 mm or a 4 deg. patient rotation about the cranio-caudal axis had no significant effect on the dose distribution. Changes in dosimetry were more likely if the reference plan contained large hot or cold spots. For a typical patient, it is estimated that a shift of 5 mm in any one direction, or a 2 deg. patient rotation would not cause more than a 5% change in the target volume receiving between 95% and 107% of the prescribed dose. If combinations of errors occur, greater dosimetric changes would be expected. It is concluded that individual patient shifts of up to 5 mm or rotations about the cranio-caudal axis of 2 deg. or less are unlikely to affect dose-volume histogram parameters by an amount judged as clinically significant. Setup errors exceeding these values may cause large dosimetric changes for some patients, particularly those with larger hot or cold regions in the dose distribution, and intervention is therefore recommended.

  17. SU-E-J-52: Dosimetric Benefit of Adaptive Re-Planning in Lung Cancer Stereotactic Body Radiotherapy (SBRT)

    SciTech Connect

    Jia, J; Tian, Z; Gu, X; Yan, H; Jiang, S; Jia, X

    2014-06-01

    Purpose: To investigate the dosimetric benefit of adaptive re-planning for lung stereotactic body radiotherapy(SBRT). Methods: Five lung cancer patients with SBRT treatment were retrospectively investigated. Our in-house supercomputing online re-planning environment (SCORE) was used to realize the re-planning process. First a deformable image registration was carried out to transfer contours from treatment planning CT to each treatment CBCT. Then an automatic re-planning using original plan DVH guided fluence-map optimization is performed to get a new plan for the up-to-date patient geometry. We compared the re-optimized plan to the original plan projected on the up-to-date patient geometry in critical dosimetric parameters, such as PTV coverage, spinal cord maximum and volumetric constraint dose, esophagus maximum and volumetric constraint dose. Results: The average volume of PTV covered by prescription dose for all patients was improved by 7.56% after the adaptive re-planning. The volume of the spinal cord receiving 14.5Gy and 23Gy (V14.5, V23) decreased by 1.48% and 0.68%, respectively. For the esophagus, the volume receiving 19.5Gy (V19.5) reduced by 1.37%. Meanwhile, the maximum dose dropped off by 2.87% for spinal cord and 4.80% for esophagus. Conclusion: Our experimental results demonstrate that adaptive re-planning for lung SBRT has the potential to minimize the dosimetric effect of inter-fraction deformation and thus improve target coverage while reducing the risk of toxicity to nearby normal tissues.

  18. Correlation between dosimetric effect and intrafraction motion during prostate treatments delivered with helical tomotherapy

    NASA Astrophysics Data System (ADS)

    Langen, Katja M.; Lu, Weiguo; Ngwa, Wilfred; Willoughby, Twyla R.; Chauhan, Bhavin; Meeks, Sanford L.; Kupelian, Patrick A.; Olivera, Gustavo

    2008-12-01

    The dosimetric impact of intrafraction prostate motion was investigated for helical tomotherapy treatments. Measured motion tracks were used to calculate the dosimetric impact on delivered target dose distributions. A dynamic dose calculation engine was developed to facilitate this evaluation. It was found that the D95% (minimum dose to 95% of the volume) changes in the prostate were well correlated with D95% changes in the PTV. This means that the dosimetric impact of intrafraction motion is not restricted to the periphery of the target. The amount of motion was not well correlated with the dosimetric impact (measured in target D95% changes) of motion. The relationship between motion and its dosimetric impact is complex and depends on the timing and direction of the movement. These findings have implications for motion management techniques. It appears that the use of target margins is not an effective strategy to protect the prostate from the effects of observed intrafraction motion. The complex relationship between motion and its dosimetric effect renders simple threshold-based intervention schemes inefficient. Monitoring of actual prostate motion would allow the documentation of the dosimetric impact and implementation of corrective action if needed. However, when motion management techniques are evaluated, it should be kept in mind that the dosimetric impact of observed prostate motion is small for the majority of fractions.

  19. Dosimetric Verification of IMRT Treatment Plans Using an Electronic Portal Imaging Device

    SciTech Connect

    Kruszyna, Marta

    2010-01-05

    This paper presents the procedures and results of dosimetric verification using an Electronic Portal Imaging Device as a tool for pre-treatment dosimetry in IMRT technique at the Greater Poland Cancer Centre in Poznan, Poland. The evaluation of dosimetric verification for various organ, during a 2 year period is given.

  20. Dosimetric Verification of IMRT Treatment Plans Using an Electronic Portal Imaging Device

    NASA Astrophysics Data System (ADS)

    Kruszyna, Marta

    2010-01-01

    This paper presents the procedures and results of dosimetric verification using an Electronic Portal Imaging Device as a tool for pre-treatment dosimetry in IMRT technique at the Greater Poland Cancer Centre in Poznan, Poland. The ewaluation of dosimetric verification for various organ, during a 2 year period is given.

  1. Dosimetric effects of source-offset in intravascular brachytherapy.

    PubMed

    Chibani, Omar; Li, X Allen

    2002-04-01

    In intravascular brachytherapy (IVBT), radioactive sources can be displaced (offset) laterally from the center of the lumen and/or longitudinally from the desired location due to the cardiac motion and/or the absence of a source-centering device. The purpose of this work is to study the dosimetric impact of such a source offset. Dose effects of both lateral and longitudinal source offsets with or without the presence of a calcified plaque or a metallic stent are calculated for the three most commonly used sources (32P, 90Sr/90Y, and 192Ir). The MCNP Monte Carlo code is used in the calculation. Static and random source offsets are considered. The major results include that (a) dose can be changed significantly (by a factor of up to 4) due to a static lateral source offset; (b) this dose variation is reduced if the lateral source offset is considered as random moving within the vessel (the dose at the 2 mm reference radial distance is increased by 5-15% for the three sources in the case of the 2D random offset studied); (c) the presence of a calcified plaque and/or a metallic stent worsens the dosimetric effects; (d) the longitudinal random source offset results in a reduction (15-18%) in the effective treatment length; (e) the dose effects of source offsets for the beta source are higher than those for the gamma source. The data presented in this paper may be used for IVBT treatment planning or for dosimetric analysis of treatment outcome. The dose change due to the source offset should be considered in dose prescription. The reduction of effective treatment length should be taken into account in selection of a proper source length to ensure an adequate coverage of the treatment target. PMID:11991124

  2. Dosimetric investigation of high dose rate, gated IMRT

    SciTech Connect

    Lin, Teh; Chen Yan; Hossain, Murshed; Li, Jinsheng; Ma, C.-M.

    2008-11-15

    Increasing the dose rate offers time saving for IMRT delivery but the dosimetric accuracy is a concern, especially in the case of treating a moving target. The objective of this work is to determine the effect of dose rate associated with organ motion and gated treatment using step-and-shoot IMRT delivery. Both measurements and analytical simulation on clinical plans are performed to study the dosimetric differences between high dose rate and low dose rate gated IMRT step-and-shoot delivery. Various sites of IMRT plans for liver, lung, pancreas, and breast cancers were delivered to a custom-made motorized phantom, which simulated sinusoidal movement. Repeated measurements were taken for gated and nongated delivery with different gating settings and three dose rates, 100, 500, and 1000 MU/min using ion chambers and extended dose range films. For the study of the residual motion effect for individual segment dose and composite dose of IMRT plans, our measurements with 30%-60% phase gating and without gating for various dose rates were compared. A small but clinically acceptable difference in delivered dose was observed between 1000, 500, and 100 MU/min at 30%-60% phase gating. A simulation is presented, which can be used for predicting dose profiles for patient cases in the presence of motion and gating to confirm that IMRT step-and-shoot delivery with gating for 1000 MU/min are not much different from 500 MU/min. Based on the authors sample plan analyses, our preliminary results suggest that using 1000 MU/Min dose rate is dosimetrically accurate and efficient for IMRT treatment delivery with gating. Nonetheless, for the concern of patient care and safety, a patient specific QA should be performed as usual for IMRT plans for high dose rate deliveries.

  3. CURRENT STATUS OF INDIVIDUAL DOSIMETRIC MONITORING IN UKRAINE.

    PubMed

    Chumak, V; Deniachenko, N; Makarovska, O; Mihailescu, L-C; Prykhodko, A; Voloskyi, V; Vanhavere, F

    2016-09-01

    About 50 000 workers are being occupationally exposed to radiation in Ukraine. Individual dosimetric monitoring (IDM) is provided by 77 dosimetry services and laboratories of very different scale with a number of monitored workers ranging from several persons to ∼9000. In the present work, the current status of personal dosimetry in Ukraine was studied. The First National Intercomparison (FNI) of the IDM labs was accompanied by a survey of the laboratory operation in terms of coverage, types of dosimetry provided, instrumentation and methodologies used, metrological support, data recording, etc. Totally, 34 laboratories responded to the FNI call, and 18 services with 19 different personal dosimetry systems took part in the intercomparison exercise providing 24 dosimeters each for blind irradiation to photons of 6 different qualities (ISO N-series X-rays, S-Cs and S-Co sources) in a dose range of 5-60 mSv. Performance of the dosimetry labs was evaluated according to ISO 14146 criteria of matching trumpet curves with H0 = 0.2 mSv. The test revealed that 8 of the 19 systems meet ISO 14146 criteria in full, 5 other labs show marginal performance and 6 laboratories demonstrated catastrophic quality of dosimetric results. Altogether, 18 participating labs provide dosimetric monitoring to 37 477 workers (about three-fourths of all occupationally exposed workers), usually on monthly (nuclear industry) or quarterly (rest of applications) basis. Of this number, 20 664 persons (55 %) receive completely adequate individual monitoring, and the number of personnel receiving IDM of inadequate quality counts 3054 persons. PMID:26979804

  4. NOTE: Dosimetric characterization of a new miniature multileaf collimator

    NASA Astrophysics Data System (ADS)

    Hartmann, G. H.; Föhlisch, F.

    2002-06-01

    The dosimetrical characteristics of a new miniature multileaf collimator (ModuLeaf MLC, MRC Systems GmbH, Heidelberg, Germany) attached to the accessory holder of a Siemens accelerator with 6 MV x-rays (PRIMUS, Siemens OCS, Concord, California, USA) have been investigated. In particular, those parameters which are important for the accuracy of the treatment such as output factors, penumbra, field edge precision and transmission/leakage were determined. These data can now be used to implement specific dose calculation procedures for this miniature multileaf collimator in treatment planning systems.

  5. Dosimetric characteristics of LKB:Cu,P solid TL detector

    NASA Astrophysics Data System (ADS)

    Hashim, S.; Alajerami, Y. S. M.; Ghoshal, S. K.; Saleh, M. A.; Saripan, M. I.; Kadir, A. B. A.; Bradley, D. A.; Alzimami, K.

    2014-11-01

    The dosimetric characteristics of newly developed borate glass dosimeter modified with lithium and potassium carbonate (LKB) and co-doped with CuO and NH4H2PO4 are reported. Broad peaks in the absence of any sharp peak confirms the amorphous nature of the prepared glass. A simple glow curve of Cu doped sample is observed with a single prominent peak (Tm) at 220 °C. The TL intensity response shows an enhancement of ~100 times due to the addition of CuO (0.1 mol%) to LKB compound. A further enhancement of the intensity by a factor of 3 from the addition of 0.25 mol% NH4H2PO4 as a co-dopant impurity is attributed to the creation of extra electron traps with consequent increase in energy transfer of radiation recombination centers. The TL yield performance of LKB:Cu,P with Zeff ≈8.92 is approximately seventeen times less sensitive compared to LiF:Mg,Ti (TLD-100). The proposed dosimeter shows good linearity up to 103 Gy, minimal fading and photon energy independence. These attractive features offered by our dosimeter is expected to pave the way towards dosimetric applications.

  6. Biologic data, models, and dosimetric methods for internal emitters

    SciTech Connect

    Weber, D.A.

    1990-01-01

    The absorbed radiation dose from internal emitters has been and will remain a pivotal factor in assessing risk and therapeutic utility in selecting radiopharmaceuticals for diagnosis and treatment. Although direct measurements of absorbed dose and dose distributions in vivo have been and will continue to be made in limited situations, the measurement of the biodistribution and clearance of radiopharmaceuticals in human subjects and the use of this data is likely to remain the primary means to approach the calculation and estimation of absorbed dose from internal emitters over the next decade. Since several approximations are used in these schema to calculate dose, attention must be given to inspecting and improving the application of this dosimetric method as better techniques are developed to assay body activity and as more experience is gained in applying these schema to calculating absorbed dose. Discussion of the need for considering small scale dosimetry to calculate absorbed dose at the cellular level will be presented in this paper. Other topics include dose estimates for internal emitters, biologic data mathematical models and dosimetric methods employed. 44 refs.

  7. Dosimetric Algorithm to Reproduce Isodose Curves Obtained from a LINAC

    PubMed Central

    Estrada Espinosa, Julio Cesar; Martínez Ovalle, Segundo Agustín; Pereira Benavides, Cinthia Kotzian

    2014-01-01

    In this work isodose curves are obtained by the use of a new dosimetric algorithm using numerical data from percentage depth dose (PDD) and the maximum absorbed dose profile, calculated by Monte Carlo in a 18 MV LINAC. The software allows reproducing the absorbed dose percentage in the whole irradiated volume quickly and with a good approximation. To validate results an 18 MV LINAC with a whole geometry and a water phantom were constructed. On this construction, the distinct simulations were processed by the MCNPX code and then obtained the PDD and profiles for the whole depths of the radiation beam. The results data were used by the code to produce the dose percentages in any point of the irradiated volume. The absorbed dose for any voxel's size was also reproduced at any point of the irradiated volume, even when the voxels are considered to be of a pixel's size. The dosimetric algorithm is able to reproduce the absorbed dose induced by a radiation beam over a water phantom, considering PDD and profiles, whose maximum percent value is in the build-up region. Calculation time for the algorithm is only a few seconds, compared with the days taken when it is carried out by Monte Carlo. PMID:25045398

  8. Dosimetric algorithm to reproduce isodose curves obtained from a LINAC.

    PubMed

    Estrada Espinosa, Julio Cesar; Martínez Ovalle, Segundo Agustín; Pereira Benavides, Cinthia Kotzian

    2014-01-01

    In this work isodose curves are obtained by the use of a new dosimetric algorithm using numerical data from percentage depth dose (PDD) and the maximum absorbed dose profile, calculated by Monte Carlo in a 18 MV LINAC. The software allows reproducing the absorbed dose percentage in the whole irradiated volume quickly and with a good approximation. To validate results an 18 MV LINAC with a whole geometry and a water phantom were constructed. On this construction, the distinct simulations were processed by the MCNPX code and then obtained the PDD and profiles for the whole depths of the radiation beam. The results data were used by the code to produce the dose percentages in any point of the irradiated volume. The absorbed dose for any voxel's size was also reproduced at any point of the irradiated volume, even when the voxels are considered to be of a pixel's size. The dosimetric algorithm is able to reproduce the absorbed dose induced by a radiation beam over a water phantom, considering PDD and profiles, whose maximum percent value is in the build-up region. Calculation time for the algorithm is only a few seconds, compared with the days taken when it is carried out by Monte Carlo. PMID:25045398

  9. Evaluation of fluence-based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG).

    PubMed

    Kumaraswamy, Lalith K; Xu, Zhengzheng; Bailey, Daniel W; Schmitt, Jonathan D; Podgorsak, Matthew B

    2016-01-01

    The Eclipse treatment planning system uses a single dosimetric leaf gap (DLG) value to retract all multileaf collimator leaf positions during dose calculation to model the rounded leaf ends. This study evaluates the dosimetric impact of the 2D variation of DLG on clinical treatment plans based on their degree of fluence modulation. In-house software was developed to retrospectively apply the 2D variation of DLG to 61 clinically treated VMAT plans, as well as to several test plans. The level of modulation of the VMAT cases were determined by calculating their modulation complexity score (MCS). Dose measurements were done using the MapCHECK device at a depth of 5.0 cm for plans with and without the 2D DLG correction. Measurements were compared against predicted dose planes from the TPS using absolute 3%/3 mm and 2%/2 mm gamma criteria for test plans and for VMAT cases, respectively. The gamma pass rate for the 2 mm, 4 mm, and 6 mm sweep test plans increased by 23.2%, 28.7%, and 26.0%, respectively, when the measurements were corrected with 2D variation of DLG. The clinical anal VMAT cases, which had very high MLC modulation, showed the most improvement. The majority of the improvement occurred for doses created by the 1.0 cm width leaves for both the test plans and the VMAT cases. The gamma pass rates for the highly modulated head and neck (H&N) cases, moderately modulated prostate and esophageal cases, and minimally modulated brain cases improved only slightly when corrected with 2D variation of DLG. This is because these cases did not employ the 1.0 cm width leaves for dose calculation and delivery. These data suggest that, at the very least, the TPS plans with highly modulated fluences created by the 1.0 cm fields require 2D DLG correction. Incorporating the 2D variation of DLG for the highly modulated clinical treatment plans improves their planar dose gamma pass rates, especially for fields employing the outer 1.0 cm width MLC leaves. This is because there are

  10. Contura Multi-Lumen Balloon Breast Brachytherapy Catheter: Comparative Dosimetric Findings of a Phase 4 Trial

    SciTech Connect

    Arthur, Douglas W.; Vicini, Frank A.; Julian, Thomas B.; Cuttino, Laurie W.; Mukhopadhyay, Nitai D.

    2013-06-01

    Purpose: Final dosimetric findings of a completed, multi-institutional phase 4 registry trial using the Contura Multi-Lumen Balloon (MLB) breast brachytherapy catheter to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer are presented. Methods and Materials: Three dosimetric plans with identical target coverage were generated for each patient for comparison: multilumen multidwell (MLMD); central-lumen multidwell (CLMD); and central-lumen single-dwell (CLSD) loading of the Contura catheter. For this study, a successful treatment plan achieved ideal dosimetric goals and included the following: ≥95% of the prescribed dose (PD) covering ≥95% of the target volume (TV); maximum skin dose ≤125% of the PD; maximum rib dose ≤145% of the PD; and V150 ≤50 cc and V200 ≤10 cc. Results: Between January 2008 and February 2011, 23 institutions participated. A total of 318 patients were available for dosimetric review. Using the Contura MLB, all dosimetric criteria were met in 78.93% of cases planned with MLMD versus 55.38% with the CLMD versus 37.66% with the CLSD (P≤.0001). Evaluating all patients with the full range of skin to balloon distance represented, median maximum skin dose was reduced by 12% and median maximum rib dose by 13.9% when using MLMD-based dosimetric plans compared to CLSD. The dosimetric benefit of MLMD was further demonstrated in the subgroup of patients where skin thickness was <5 mm, where MLMD use allowed a 38% reduction in median maximum skin dose over CLSD. For patients with rib distance <5 mm, the median maximum rib dose reduction was 27%. Conclusions: Use of the Contura MLB catheter produced statistically significant improvements in dosimetric capabilities between CLSD and CLMD treatments. This device approach demonstrates the ability not only to overcome the barriers of limited skin thickness and close rib proximity, but to consistently achieve a higher standard of dosimetric planning goals.

  11. Dosimetric Effect of Online Image-Guided Anatomical Interventions for Postprostatectomy Cancer Patients

    SciTech Connect

    Diot, Quentin; Olsen, Christine; Kavanagh, Brian; Raben, David; Miften, Moyed

    2011-02-01

    Purpose: To assess daily variations in delivered doses in postprostatectomy patients, using kilovoltage cone-beam CT (CBCT) datasets acquired before and after interventions to correct for observed distortions in volume/shape of rectum and bladder. Methods and Materials: Seventeen consecutive patients treated with intensity-modulated radiotherapy to the prostate bed were studied. For patients with large anatomical variations, quantified by either a rectal wall displacement of >5 mm or bladder volume change of >50% on the CBCT compared with the planning CT, an intervention was performed to adjust the rectum and/or bladder filling. Cumulative doses over the pre- and post-intervention fractions were calculated by tracking the position of the planning CT voxels on different CBCTs using a deformable surface-mapping algorithm. Dose and displacements vectors were projected on two-dimensional maps, the minimal dose received by the highest 95% of the planing target volume (PTV D95) and the highest 10% of the rectum volume (D10) as well as the bladder volume receiving >2 Gy (V2) were evaluated. Results: Of 544 fractions, 96 required intervention. Median (range) number of interventions per patient was 5 (2-12). Compared with the planning values, the mean (SD) pre- vs. postintervention value for PTV D95 was -2% (2%) vs. -1% (2%) (p < 0.12), for rectum D10 was -1% (4%) vs. +1% (4%) (p < 0.24), and for bladder V2 was +6% vs. +20% (p < 0.84). Conclusions: Interventions to reduce treatment volume deformations due to bladder and rectum fillings are not necessary when patients receive daily accurate CBCT localization, and the frequency of those potential interventions is low. However, for hypofractionated treatments, the relative frequency can significantly increase, and interventions can become more dosimetrically beneficial.

  12. Poster — Thur Eve — 58: Dosimetric validation of electronic compensation for radiotherapy treatment planning

    SciTech Connect

    Gräfe, James; Khan, Rao; Meyer, Tyler

    2014-08-15

    In this study we investigate the deliverability of dosimetric plans generated by the irregular surface compensator (ISCOMP) algorithm for 6 MV photon beams in Eclipse (Varian Medical System, CA). In contrast to physical tissue compensation, the electronic ISCOMP uses MLCs to dynamically modulate the fluence of a photon beam in order to deliver a uniform dose at a user defined plane in tissue. This method can be used to shield critical organs that are located within the treatment portal or improve dose uniformity by tissue compensation in inhomogeneous regions. Three site specific plans and a set of test fields were evaluated using the γ-metric of 3%/ 3 mm on Varian EPID, MapCHECK, and Gafchromic EBT3 film with a clinical tolerance of >95% passing rates. Point dose measurements with an NRCC calibrated ionization chamber were also performed to verify the absolute dose delivered. In all cases the MapCHECK measured plans met the gamma criteria. The mean passing rate for the six EBT3 film field measurements was 96.2%, with only two fields at 93.4 and 94.0% passing rates. The EPID plans passed for fields encompassing the central ∼10 × 10 cm{sup 2} region of the detector; however for larger fields and greater off-axis distances discrepancies were observed and attributed to the profile corrections and modeling of backscatter in the portal dose calculation. The magnitude of the average percentage difference for 21 ion chamber point dose measurements and 17 different fields was 1.4 ± 0.9%, and the maximum percentage difference was −3.3%. These measurements qualify the algorithm for routine clinical use subject to the same pre-treatment patient specific QA as IMRT.

  13. Analysis of superficial fluorescence patterns in nonmelanoma skin cancer during photodynamic therapy by a dosimetric model

    NASA Astrophysics Data System (ADS)

    Salas-García, I.; Fanjul-Vélez, F.; Arce-Diego, J. L.

    2016-03-01

    In this work the superficial fluorescence patterns in different nonmelanoma skin cancers and their photodynamic treatment response are analysed by a fluorescence based dosimetric model. Results show differences of even more than 50% in the fluorescence patterns as photodynamic therapy progresses depending on the malignant tissue type. They demonstrate the great relevance of the biological media as an additional dosimetric factor and contribute to the development of a future customized therapy with the assistance of dosimetric tools to interpret the fluorescence images obtained during the treatment monitoring and the differential photodiagnosis.

  14. EFFECTIVE DOSIMETRIC HALF LIFE OF CESIUM 137 SOIL CONTAMINATION

    SciTech Connect

    Jannik, T; P Fledderman, P; Michael Paller, M

    2008-01-09

    In the early 1960s, an area of privately-owned swamp adjacent to the US Department of Energy's Savannah River Site (SRS), known as Creek Plantation, was contaminated by site operations. Studies conducted in 1974 estimated that approximately 925 GBq of {sup 137}Cs was deposited in the swamp. Subsequently, a series of surveys--composed of 52 monitoring locations--was initiated to characterize and trend the contaminated environment. The annual, potential, maximum doses to a hypothetical hunter were estimated by conservatively using the maximum {sup 137}Cs concentrations measured in the soil. The purpose of this report is to calculate an 'effective dosimetric' half-life for {sup 137}Cs in soil (based on the maximum concentrations) and compare it to the effective environmental half-life (based on the geometric mean concentrations).

  15. Thermoluminescence dosimetric properties and effective atomic numbers of window glass

    NASA Astrophysics Data System (ADS)

    Bootjomchai, Cherdsak; Laopaiboon, Raewat

    2014-03-01

    This work presents the main thermoluminescence (TL) dosimetric characteristics of commercial Thai transparent window glass. The amorphous structure of window glass was investigated by XRD. The glow curve revealed a peak (Tm) at 235 °C. The thermoluminescence response of window glass was studied after irradiation with photons in the absorb dose range of 0-14.05 mGy, which is of interest for the personal protection level of dosimetry. A linear response was obtained after both the first irradiation and the second irradiation. The minimum detectable dose of window glass was 0.15 mGy. The effective atomic number of window glass as a function of photon energy was calculated. The obtained results for the effective atomic number showed that it is very close to that of human biological tissues (Zeff = 6.7-8.4 at studied energy).

  16. Potential ocular damage from microwave exposure during electrosurgery: dosimetric survey

    SciTech Connect

    Paz, J.D.; Milliken, R.; Ingram, W.T.; Frank, A.; Atkin, A.

    1987-07-01

    A dosimetric survey of microwave radiation emitted by electrosurgical units used in operating rooms indicated that surgeons expose themselves to levels that may be hazardous, and that ocular exposures are especially high: 20 cm from the active lead, electric field strength at the eye/forehead position was 9.0 X 10(6) V2/M2 for the monopolar unit; and magnetic field strength at this position reached a magnitude of 3.5 A2/M2. These electric and magnetic fields exceeded the TLVs of the American National Standards Institute. The authors concluded that the high levels of microwave radiation generated by electrosurgery devices should receive immediate attention to assess health effects associated with such exposures.

  17. Dosimetric Analysis of Respiratory-Gated Radiotherapy for Hepatocellular Carcinoma

    SciTech Connect

    Xi Mian; Zhang Li; Liu Mengzhong; Deng Xiaowu; Huang Xiaoyan; Liu Hui

    2011-07-01

    The purpose of this study was to define individualized internal target volume (ITV) for hepatocellular carcinoma (HCC) using 4D computed tomography (4DCT), and to determine the geometric and dosimetric benefits of respiratory gating. Gross tumor volumes (GTVs) were contoured on 10 respiratory phases of 4DCT images for 12 patients with HCC. Three treatment plans were prepared using different planning target volumes (PTVs): (1) PTV{sub 3D}, derived from a single helical clinical target volume (CTV) plus conventional margins; (2) PTV{sub 10phases}, derived from ITV{sub 10phases}, which encompassed all 10 CTVs plus an isotropic margin of 0.8 cm; (3) PTV{sub gating}, derived from ITV{sub gating}, which encompassed three CTVs within gating-window at end-expiration plus an isotropic margin of 0.8 cm. The PTV{sub 3D} was the largest volume for all patients. The ITV-based plans and gating plans spared more normal tissues than 3D plans, especially the liver. Without increasing normal tissue complication probability of the 3D plans, the ITV-based plans allowed for increasing the calculated dose from 50.8 Gy to 54.7 Gy on average, and the gating plans could further escalate the dose to 58.5 Gy. Compared with ITV-based plans, the dosimetric gains with gating plan strongly correlated with GTV mobility in the craniocaudal direction. The ITV-based plans can ensure target coverage with less irradiation of normal tissues compared with 3D plans. Respiratory-gated radiotherapy can further reduce the target volumes to spare more surrounding tissues and allow dose escalation, especially for patients with tumor mobility >1 cm.

  18. A revised dosimetric model of the head and brain

    SciTech Connect

    Bolch, W.E.; Poston, J.W. Sr.

    1995-05-01

    The use of PET and SPECT radiopharmaceuticals in brain imaging has greatly expanded over the past several years. Many of these agents localize within particular subregions of the brain, thus allowing for detailed physiologic and metabolic imaging. Dosimetric models to support these advances in nuclear medicine have been lacking. For example, the brain within the phantom of MIRD Pamphlet No. 5 Revised is modeled simply as a single ellipsoid of tissue with no differentiation of its internal structures. To address this need, the MIRD Committee established a Task Group in 1992 to construct a revised dosimetric model of the brain to include the following subregions: the cerebral cortex, the white matter, the cerebellum, the thalamus, the caudate nucleus, the lentiform nucleus (putamen and globus pallidus), the cerebral spinal fluid (within the subarachnoid space of the brain), the lateral ventricles, and the third ventricle. Estimates of both electron and photon absorbed fractions (AF) were subsequently calculated using the EGS4 radiation transport code. For most of the internal brain structures, electron AFs are shown to fall fellow unity for all regions within the energy range of {approximately}200 keV to 4 MeV. For example, AFs for the caudate nucleus as both a source and target region and estimated as 0.98, 0.84, 0.39 for 200-keV, 1-MeV, and 4-MeV electron sources, respectively. Corresponding AFs within the white matter as a source and target region are estimated as 1.0, 0.95, and 0.79 for these same electron energies. Revised S values were subsequently calculated for a variety of beta-particle and positron emitters used in brain imaging.

  19. SU-E-T-134: Dosimetric Implications From Organ Segmentation

    SciTech Connect

    Wu, Z; Turian, J; Chu, J

    2014-06-01

    Purpose: To evaluate the dosimetric implications resulting from organ segmentation performed by different clinical experts Methods: Twelve patients received SBRT treatment to thoracic region within the past year were selected for this study. Three physicians contoured a set of organs following RTOG guideline. DVHs of all contours were generated from the approved plans used for treatment, and were compared to those produced during planning. Most OARs were evaluated on their max dose, some, such as heart and chest wall, were also evaluated on metrics such as max dose to 4cc of volume, or 30Gy volume dose. Results: In general, there is a greater dosimetric difference between the RTOG contour sets and clinical contour sets than among the three RTOG contour sets themselves for each patient. For example, there was no difference in esophagus max dose between the RTOG contour sets for ten patients. However, they showed an average of 2.3% higher max dose than the clinical contour set, with a standard deviation of 6.6%. The proximal bronchial tree (PBT) showed a similar behavior. The average difference of PBT max dose for seven patients is 0% between the three RTOG contour sets, with standard deviation of 1%. They showed an average of 16.1% higher max dose than the clinical contour set, with a standard deviation of 126%. Conclusion: This study shows that using RTOG contouring standards improves segmentation consistency between different physicians; most of the contours examined showed less than 1% dose difference. When RTOG contour sets were compared to the clinical contour set, the differences are much more significant. Thus it is important to standardize contouring guidelines in radiation therapy treatment planning. This will reduce uncertainties in clinical outcome analysis and research studies.

  20. Dosimetric Comparison of Craniospinal Irradiation Using Different Tomotherapy Techniques.

    PubMed

    Zhang, X; Penagaricano, J; Han, E Y; Morrill, S; Hardee, M; Liang, X; Gupta, S K; Corry, P M; Ratanatharathom, V

    2015-08-01

    The objective of this study is to compare the new and conventional tomotherapy treatment techniques and to evaluate dosimetric differences between them. A dosimetric analysis was performed by comparing planning target volume (PTV) median dose, 95% of PTV dose coverage, Paddick conformity index (CI), homogeneity index (HI), whole-body integral dose, and OAR median doses. The beam on time (BOT) and the effect of different jaw sizes and pitch values was studied. The study results indicated that the PTV dose coverage for all the techniques was comparable. Treatment plans using dynamic jaw reduced OAR doses to structures located at the treatment field edge compared to fixed jaw plans. The HT-3DCRT plans resulted in higher OAR doses to kidney, liver, and lung compared to the other techniques, and TD-IMRT provided the best dose sparing to liver compared to other techniques. Whole-body integral dose differences were found to be insignificant among the techniques. BOT was found to be higher for fixed jaw treatment plan compared to dynamic jaw plan and comparable between all treatment techniques with 5-cm dynamic jaw. In studying effect of jaw size, better OAR sparing and HI were found for 2.5-cm jaw but at the expense of doubling of BOT as compared to 5-cm jaw. There was no significant improvement found in OAR sparing when the pitch value was increased. Increasing the pitch from 0.2 to 0.43, the CI was improved, HI improved only for 5-cm jaw size, and BOT decreased to approximately half of its original time. PMID:25398680

  1. Dosimetric Effects of Magnetic Resonance Imaging-assisted Radiotherapy Planning: Dose Optimization for Target Volumes at High Risk and Analytic Radiobiological Dose Evaluation.

    PubMed

    Park, Ji-Yeon; Suh, Tae Suk; Lee, Jeong-Woo; Ahn, Kook-Jin; Park, Hae-Jin; Choe, Bo-Young; Hong, Semie

    2015-10-01

    Based on the assumption that apparent diffusion coefficients (ADCs) define high-risk clinical target volume (aCTVHR) in high-grade glioma in a cellularity-dependent manner, the dosimetric effects of aCTVHR-targeted dose optimization were evaluated in two intensity-modulated radiation therapy (IMRT) plans. Diffusion-weighted magnetic resonance (MR) images and ADC maps were analyzed qualitatively and quantitatively to determine aCTVHR in a high-grade glioma with high cellularity. After confirming tumor malignancy using the average and minimum ADCs and ADC ratios, the aCTVHR with double- or triple-restricted water diffusion was defined on computed tomography images through image registration. Doses to the aCTVHR and CTV defined on T1-weighted MR images were optimized using a simultaneous integrated boost technique. The dosimetric benefits for CTVs and organs at risk (OARs) were compared using dose volume histograms and various biophysical indices in an ADC map-based IMRT (IMRTADC) plan and a conventional IMRT (IMRTconv) plan. The IMRTADC plan improved dose conformity up to 15 times, compared to the IMRTconv plan. It reduced the equivalent uniform doses in the visual system and brain stem by more than 10% and 16%, respectively. The ADC-based target differentiation and dose optimization may facilitate conformal dose distribution to the aCTVHR and OAR sparing in an IMRT plan. PMID:26425053

  2. IPIP: A new approach to inverse planning for HDR brachytherapy by directly optimizing dosimetric indices

    SciTech Connect

    Siauw, Timmy; Cunha, Adam; Atamtuerk, Alper; Hsu, I-Chow; Pouliot, Jean; Goldberg, Ken

    2011-07-15

    Purpose: Many planning methods for high dose rate (HDR) brachytherapy require an iterative approach. A set of computational parameters are hypothesized that will give a dose plan that meets dosimetric criteria. A dose plan is computed using these parameters, and if any dosimetric criteria are not met, the process is iterated until a suitable dose plan is found. In this way, the dose distribution is controlled by abstract parameters. The purpose of this study is to develop a new approach for HDR brachytherapy by directly optimizing the dose distribution based on dosimetric criteria. Methods: The authors developed inverse planning by integer program (IPIP), an optimization model for computing HDR brachytherapy dose plans and a fast heuristic for it. They used their heuristic to compute dose plans for 20 anonymized prostate cancer image data sets from patients previously treated at their clinic database. Dosimetry was evaluated and compared to dosimetric criteria. Results: Dose plans computed from IPIP satisfied all given dosimetric criteria for the target and healthy tissue after a single iteration. The average target coverage was 95%. The average computation time for IPIP was 30.1 s on an Intel(R) Core{sup TM}2 Duo CPU 1.67 GHz processor with 3 Gib RAM. Conclusions: IPIP is an HDR brachytherapy planning system that directly incorporates dosimetric criteria. The authors have demonstrated that IPIP has clinically acceptable performance for the prostate cases and dosimetric criteria used in this study, in both dosimetry and runtime. Further study is required to determine if IPIP performs well for a more general group of patients and dosimetric criteria, including other cancer sites such as GYN.

  3. Dosimetric feasibility study for an extracorporeal BNCT application on liver metastases at the TRIGA Mainz.

    PubMed

    Blaickner, M; Kratz, J V; Minouchehr, S; Otto, G; Schmidberger, H; Schütz, C; Vogtländer, L; Wortmann, B; Hampel, G

    2012-01-01

    This study investigates the dosimetric feasibility of Boron Neutron Capture Therapy (BNCT) of explanted livers in the thermal column of the research reactor in Mainz. The Monte Carlo code MCNP5 is used to calculate the biologically weighted dose for different ratios of the (10)B-concentration in tumour to normal liver tissue. The simulation results show that dosimetric goals are only partially met. To guarantee effective BNCT treatment the organ has to be better shielded from all gamma radiation. PMID:21872481

  4. Active Mapping.

    ERIC Educational Resources Information Center

    Day, Dennis

    1994-01-01

    Explains a social studies lesson for third graders that uses KidPix, a computer software graphics program to help students make maps and map keys. Advantages to using the computer versus hand drawing maps are discussed, and an example of map requirements for the lesson is included. (LRW)

  5. Concept Mapping.

    ERIC Educational Resources Information Center

    Callison, Daniel

    2001-01-01

    Explains concept mapping as a heuristic device that is helpful in visualizing the relationships between and among ideas. Highlights include how to begin a map; brainstorming; map applications, including document or information summaries and writing composition; and mind mapping to strengthen note-taking. (LRW)

  6. Contour Mapping

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In the early 1990s, the Ohio State University Center for Mapping, a NASA Center for the Commercial Development of Space (CCDS), developed a system for mobile mapping called the GPSVan. While driving, the users can map an area from the sophisticated mapping van equipped with satellite signal receivers, video cameras and computer systems for collecting and storing mapping data. George J. Igel and Company and the Ohio State University Center for Mapping advanced the technology for use in determining the contours of a construction site. The new system reduces the time required for mapping and staking, and can monitor the amount of soil moved.

  7. Error Analysis of non-TLD HDR Brachytherapy Dosimetric Techniques

    NASA Astrophysics Data System (ADS)

    Amoush, Ahmad

    The American Association of Physicists in Medicine Task Group Report43 (AAPM-TG43) and its updated version TG-43U1 rely on the LiF TLD detector to determine the experimental absolute dose rate for brachytherapy. The recommended uncertainty estimates associated with TLD experimental dosimetry include 5% for statistical errors (Type A) and 7% for systematic errors (Type B). TG-43U1 protocol does not include recommendation for other experimental dosimetric techniques to calculate the absolute dose for brachytherapy. This research used two independent experimental methods and Monte Carlo simulations to investigate and analyze uncertainties and errors associated with absolute dosimetry of HDR brachytherapy for a Tandem applicator. An A16 MicroChamber* and one dose MOSFET detectors† were selected to meet the TG-43U1 recommendations for experimental dosimetry. Statistical and systematic uncertainty analyses associated with each experimental technique were analyzed quantitatively using MCNPX 2.6‡ to evaluate source positional error, Tandem positional error, the source spectrum, phantom size effect, reproducibility, temperature and pressure effects, volume averaging, stem and wall effects, and Tandem effect. Absolute dose calculations for clinical use are based on Treatment Planning System (TPS) with no corrections for the above uncertainties. Absolute dose and uncertainties along the transverse plane were predicted for the A16 microchamber. The generated overall uncertainties are 22%, 17%, 15%, 15%, 16%, 17%, and 19% at 1cm, 2cm, 3cm, 4cm, and 5cm, respectively. Predicting the dose beyond 5cm is complicated due to low signal-to-noise ratio, cable effect, and stem effect for the A16 microchamber. Since dose beyond 5cm adds no clinical information, it has been ignored in this study. The absolute dose was predicted for the MOSFET detector from 1cm to 7cm along the transverse plane. The generated overall uncertainties are 23%, 11%, 8%, 7%, 7%, 9%, and 8% at 1cm, 2cm, 3cm

  8. Silicon strip detector for a novel 2D dosimetric method for radiotherapy treatment verification

    NASA Astrophysics Data System (ADS)

    Bocci, A.; Cortés-Giraldo, M. A.; Gallardo, M. I.; Espino, J. M.; Arráns, R.; Alvarez, M. A. G.; Abou-Haïdar, Z.; Quesada, J. M.; Pérez Vega-Leal, A.; Pérez Nieto, F. J.

    2012-05-01

    The aim of this work is to characterize a silicon strip detector and its associated data acquisition system, based on discrete electronics, to obtain in a near future absorbed dose maps in axial planes for complex radiotherapy treatments, using a novel technique. The experimental setup is based on two phantom prototypes: the first one is a polyethylene slab phantom used to characterize the detector in terms of linearity, percent depth dose, reproducibility, uniformity and penumbra. The second one is a cylindrical phantom, specifically designed and built to recreate conditions close to those normally found in clinical environments, for treatment planning assessment. This system has been used to study the dosimetric response of the detector, in the axial plane of the phantom, as a function of its angle with respect to the irradiation beam. A software has been developed to operate the rotation of this phantom and to acquire signals from the silicon strip detector. As an innovation, the detector was positioned inside the cylindrical phantom parallel to the beam axis. Irradiation experiments were carried out with a Siemens PRIMUS linac operating in the 6 MV photon mode at the Virgen Macarena Hospital. Monte Carlo simulations were performed using Geant4 toolkit and results were compared to Treatment Planning System (TPS) calculations for the absorbed dose-to-water case. Geant4 simulations were used to estimate the sensitivity of the detector in different experimental configurations, in relation to the absorbed dose in each strip. A final calibration of the detector in this clinical setup was obtained by comparing experimental data with TPS calculations.

  9. Dosimetric characterization of two radium sources for retrospective dosimetry studies

    SciTech Connect

    Candela-Juan, C.; Karlsson, M.; Lundell, M.; Ballester, F.; Tedgren, Å. Carlsson

    2015-05-15

    Purpose: During the first part of the 20th century, {sup 226}Ra was the most used radionuclide for brachytherapy. Retrospective accurate dosimetry, coupled with patient follow up, is important for advancing knowledge on long-term radiation effects. The purpose of this work was to dosimetrically characterize two {sup 226}Ra sources, commonly used in Sweden during the first half of the 20th century, for retrospective dose–effect studies. Methods: An 8 mg {sup 226}Ra tube and a 10 mg {sup 226}Ra needle, used at Radiumhemmet (Karolinska University Hospital, Stockholm, Sweden), from 1925 to the 1960s, were modeled in two independent Monte Carlo (MC) radiation transport codes: GEANT4 and MCNP5. Absorbed dose and collision kerma around the two sources were obtained, from which the TG-43 parameters were derived for the secular equilibrium state. Furthermore, results from this dosimetric formalism were compared with results from a MC simulation with a superficial mould constituted by five needles inside a glass casing, placed over a water phantom, trying to mimic a typical clinical setup. Calculated absorbed doses using the TG-43 formalism were also compared with previously reported measurements and calculations based on the Sievert integral. Finally, the dose rate at large distances from a {sup 226}Ra point-like-source placed in the center of 1 m radius water sphere was calculated with GEANT4. Results: TG-43 parameters [including g{sub L}(r), F(r, θ), Λ, and s{sub K}] have been uploaded in spreadsheets as additional material, and the fitting parameters of a mathematical curve that provides the dose rate between 10 and 60 cm from the source have been provided. Results from TG-43 formalism are consistent within the treatment volume with those of a MC simulation of a typical clinical scenario. Comparisons with reported measurements made with thermoluminescent dosimeters show differences up to 13% along the transverse axis of the radium needle. It has been estimated that

  10. SU-E-J-200: A Dosimetric Analysis of 3D Versus 4D Image-Based Dose Calculation for Stereotactic Body Radiation Therapy in Lung Tumors

    SciTech Connect

    Ma, M; Rouabhi, O; Flynn, R; Xia, J; Bayouth, J

    2014-06-01

    Purpose: To evaluate the dosimetric difference between 3D and 4Dweighted dose calculation using patient specific respiratory trace and deformable image registration for stereotactic body radiation therapy in lung tumors. Methods: Two dose calculation techniques, 3D and 4D-weighed dose calculation, were used for dosimetric comparison for 9 lung cancer patients. The magnitude of the tumor motion varied from 3 mm to 23 mm. Breath-hold exhale CT was used for 3D dose calculation with ITV generated from the motion observed from 4D-CT. For 4D-weighted calculation, dose of each binned CT image from the ten breathing amplitudes was first recomputed using the same planning parameters as those used in the 3D calculation. The dose distribution of each binned CT was mapped to the breath-hold CT using deformable image registration. The 4D-weighted dose was computed by summing the deformed doses with the temporal probabilities calculated from their corresponding respiratory traces. Dosimetric evaluation criteria includes lung V20, mean lung dose, and mean tumor dose. Results: Comparing with 3D calculation, lung V20, mean lung dose, and mean tumor dose using 4D-weighted dose calculation were changed by −0.67% ± 2.13%, −4.11% ± 6.94% (−0.36 Gy ± 0.87 Gy), −1.16% ± 1.36%(−0.73 Gy ± 0.85 Gy) accordingly. Conclusion: This work demonstrates that conventional 3D dose calculation method may overestimate the lung V20, MLD, and MTD. The absolute difference between 3D and 4D-weighted dose calculation in lung tumor may not be clinically significant. This research is supported by Siemens Medical Solutions USA, Inc and Iowa Center for Research By Undergraduates.

  11. 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.

  12. Optically stimulated luminescence: Searching for new dosimetric materials

    NASA Astrophysics Data System (ADS)

    Yoshimura, E. M.; Yukihara, E. G.

    2006-09-01

    Optically stimulated luminescence (OSL) is increasingly being used as a dosimetric technique in various fields such as medical, environmental and space dosimetry, and sediment and archaeological dating. Nevertheless few compounds are suitable as OSL materials. In this work, a survey was made of various insulators, searching for candidates for new OSL dosimeters. Natural and synthetic crystals and glasses from numerous sources are included. Luminescence was stimulated with blue LEDs (470 nm) and with IR laser (830 nm) provided by an automatic reader. Irradiation was performed with a 90Sr/ 90Y beta source, and the emitted light was measured with a photomultiplier tube, protected with suitable optical filters. Thermoluminescence (TL) of the samples was also measured, with the same equipment, to evaluate the thermal and optical stability of the defects related to OSL and TL. Among the various investigated materials, Al 2O 3:Cr, Mg, Fe, MgAl 2O 4 spinels, Mg 2SiO 4:Tb, and natural fluorite show potential as OSL dosimeters. Some materials, as barium aluminoborate glasses, although showing intense OSL signals, present a high fading at room temperature. In that situation the OSL signal is related to low temperature TL peaks that also fade at room temperature. None of the investigated materials was specially prepared to be used as an OSL dosimeter, which means that work can be done, mainly in the impurity nature and content, in order to improve OSL signals and to overcome some of the shortcomings that were noticed.

  13. A comprehensive approach to age-dependent dosimetric modeling

    SciTech Connect

    Leggett, R.W.; Cristy, M.; Eckerman, K.F.

    1986-01-01

    In the absence of age-specific biokinetic models, current retention models of the International Commission on Radiological Protection (ICRP) frequently are used as a point of departure for evaluation of exposures to the general population. These models were designed and intended for estimation of long-term integrated doses to the adult worker. Their format and empirical basis preclude incorporation of much valuable physiological information and physiologically reasonable assumptions that could be used in characterizing the age-specific behavior of radioelements in humans. In this paper we discuss a comprehensive approach to age-dependent dosimetric modeling in which consideration is given not only to changes with age in masses and relative geometries of body organs and tissues but also to best available physiological and radiobiological information relating to the age-specific biobehavior of radionuclides. This approach is useful in obtaining more accurate estimates of long-term dose commitments as a function of age at intake, but it may be particularly valuable in establishing more accurate estimates of dose rate as a function of age. Age-specific dose rates are needed for a proper analysis of the potential effects on estimates or risk of elevated dose rates per unit intake in certain stages of life, elevated response per unit dose received during some stages of life, and age-specific non-radiogenic competing risks.

  14. Active pixel as dosimetric device for interventional radiology

    NASA Astrophysics Data System (ADS)

    Servoli, L.; Baldaccini, F.; Biasini, M.; Checcucci, B.; Chiocchini, S.; Cicioni, R.; Conti, E.; Di Lorenzo, R.; Dipilato, A. C.; Esposito, A.; Fanó, L.; Paolucci, M.; Passeri, D.; Pentiricci, A.; Placidi, P.

    2013-08-01

    Interventional Radiology (IR) is a subspecialty of radiology comprehensive of all minimally invasive diagnostic and therapeutic procedures performed using radiological devices to obtain image guidance. The interventional procedures are potentially harmful for interventional radiologists and medical staff due to the X-ray diffusion by the patient's body. The characteristic energy range of the diffused photons spans few tens of keV. In this work we will present a proposal for a new X-ray sensing element in the energy range of interest for IR procedures. The sensing element will then be assembled in a dosimeter prototype, capable of real-time measurement, packaged in a small form-factor, with wireless communication and no external power supply to be used for individual operators dosimetry for IR procedures. For the sensor, which is the heart of the system, we considered three different Active Pixel Sensors (APS). They have shown a good capability as single X-ray photon detectors, up to several tens keV photon energy. Two dosimetric quantities have been considered, the number of detected photons and the measured energy deposition. Both observables have a linear dependence with the dose, as measured by commercial dosimeters. The uncertainties in the measurement are dominated by statistic and can be pushed at ˜5% for all the sensors under test.

  15. Dosimetric implications of new compounds for neutron capture therapy (NCT)

    SciTech Connect

    Fairchild, R.G.

    1982-01-01

    Systemic application of radiolabeled or cytotoxic agents should allow targeting of primary and metastatic neoplasms on a cellular level. In fact, drug uptake in non-target cell pools often exceeds toxic levels before sufficient amounts are delivered to tumor. In addition, at the large concentration of molecules necessary for therapy, effects of saturation are often found. Application of NCT can circumvent problems associated with high uptake in competing non-target cell pools, as the /sup 10/B(n,..cap alpha..)/sup 7/Li reaction is activated only within the radiation field. A comparison with other modes of particle therapy indicated that NCT provides significant advantages. It is however, difficult to obtain vehicles for boron transport which demonstrate both the tumor specificity and concentration requisite for NCT. A number of biomolecules have been investigated which show both the necessary concentration and specificity. These include chlorpromazine, thiouracil, porphyrins, amino acids, and nucleosides. However, these analogs have yet to be made available for NCT. Dosimetric implications of binding sites are considered, as well as alternate neutron sources. (ERB)

  16. Dosimetric implications of age related glandular changes in screening mammography

    NASA Astrophysics Data System (ADS)

    Beckett, J. R.; Kotre, C. J.

    2000-03-01

    The UK National Health Service Breast Screening Programme is currently organized to routinely screen women between the ages of 50 and 64, with screening for older women available on request. The lower end of this age range closely matches the median age for the menopause (51 years), during which significant changes in the composition of the breast are known to occur. In order to quantify the dosimetric effect of these changes, radiographic factors and compressed breast thickness data for a cohort of 1258 women aged between 35 and 79 undergoing breast screening mammography have been used to derive estimates of breast glandularity and mean glandular dose (MGD), and examine their variation with age. The variation of mean radiographic exposure factors with age is also investigated. The presence of a significant number of age trial women within the cohort allowed an extended age range to be studied. Estimates of MGD including corrections for breast glandularity based on compressed breast thickness only, compressed breast thickness and age and for each individual woman are compared with the MGD based on the conventional assumption of a 50:50 adipose/glandular composition. It has been found that the use of the conventional 50:50 assumption leads to overestimates of MGD of up to 13% over the age range considered. By using compressed breast thickness to estimate breast glandularity, this error range can be reduced to 8%, whilst age and compressed breast thickness based glandularity estimates result in an error range of 1%.

  17. Dosimetric Study of a Low-Dose-Rate Brachytherapy Source

    NASA Astrophysics Data System (ADS)

    Rodríguez-Villafuerte, M.; Arzamendi, S.; Díaz-Perches, R.

    Carcinoma of the cervix is the most common malignancy - in terms of both incidence and mortality - in Mexican women. Low dose rate (LDR) intracavitary brachytherapy is normally prescribed for the treatment of this disease to the vast majority of patients attending public hospitals in our country. However, most treatment planning systems being used in these hospitals still rely on Sievert integral dose calculations. Moreover, experimental verification of dose distributions are hardly ever done. In this work we present a dosimetric characterisation of the Amersham CDCS-J 137Cs source, an LDR brachytherapy source commonly used in Mexican hospitals. To this end a Monte Carlo simulation was developed, that includes a realistic description of the internal structure of the source embedded in a scattering medium. The Monte Carlo results were compared to experimental measurements of dose distributions. A lucite phantom with the same geometric characteristics as the one used in the simulation was built. Dose measurements were performed using thermoluminescent dosimeters together with commercial RadioChromic dye film. A comparison between our Monte Carlo simulation, the experimental data, and results reported in the literature is presented.

  18. Dosimetric characteristics of a MOSFET dosimeter for clinical electron beams.

    PubMed

    Manigandan, D; Bharanidharan, G; Aruna, P; Devan, K; Elangovan, D; Patil, Vikram; Tamilarasan, R; Vasanthan, S; Ganesan, S

    2009-09-01

    The fundamental dosimetric characteristics of commercially available metal oxide semiconductor field effect transistor (MOSFET) detectors were studied for clinical electron beam irradiations. MOSFET showed excellent linearity against doses measured using an ion chamber in the dose range of 20-630cGy. MOSFET reproducibility is better at high doses compared to low doses. The output factors measured with the MOSFET were within +/-3% when compared with those measured with a parallel plate chamber. From 4 to 12MeV, MOSFETs showed a large angular dependence in the tilt directions and less in the axial directions. MOSFETs do not show any dose-rate dependence between 100 and 600MU/min. However, MOSFETs have shown under-response when the dose per pulse of the beam is decreased. No measurable effect in MOSFET response was observed in the temperature range of 23-40 degrees C. The energy dependence of a MOSFET dosimeter was within +/-3.0% for 6-18MeV electron beams and 5.5% for 4MeV ones. This study shows that MOSFET detectors are suitable for dosimetry of electron beams in the energy range of 4-18MeV. PMID:19128995

  19. Toward optimizing patient-specific IMRT QA techniques in the accurate detection of dosimetrically acceptable and unacceptable patient plans

    SciTech Connect

    McKenzie, Elizabeth M.; Balter, Peter A.; Stingo, Francesco C.; Jones, Jimmy; Followill, David S.; Kry, Stephen F.

    2014-12-15

    was no significant difference in the performance of any device between gamma criteria of 2%/2 mm, 3%/3 mm, and 5%/3 mm. Finally, optimal cutoffs (e.g., percent of pixels passing gamma) were determined for each device and while clinical practice commonly uses a threshold of 90% of pixels passing for most cases, these results showed variability in the optimal cutoff among devices. Conclusions: IMRT QA devices have differences in their ability to accurately detect dosimetrically acceptable and unacceptable plans. Field-by-field analysis with a MapCheck device and use of the MapCheck with a MapPhan phantom while delivering at planned rotational gantry angles resulted in a significantly poorer ability to accurately sort acceptable and unacceptable plans compared with the other techniques examined. Patient-specific IMRT QA techniques in general should be thoroughly evaluated for their ability to correctly differentiate acceptable and unacceptable plans. Additionally, optimal agreement thresholds should be identified and used as common clinical thresholds typically worked very poorly to identify unacceptable plans.

  20. Spatial Variation of Dosimetric Leaf Gap and Its Impact on Absolute Dose Delivery in Radiation Therapy

    NASA Astrophysics Data System (ADS)

    Kumaraswamy, Lalith

    During dose calculation, the Eclipse Treatment Planning system (TPS) retracts the MLC leaf positions by half of the dosimetric leaf gap (DLG) value (measured at central axis) for all leaf positions in a dynamic MLC plan to accurately model the rounded leaf ends. The aim of this study is to map the variation of DLG along the travel path of each MLC leaf pair and quantify how this variation impacts delivered dose. 6 MV DLG values were measured for all MLC leaf pairs in increments of 1.0 cm (from the line intersecting the CAX and perpendicular to MLC motion) to 13.0 cm off axis distance at depth of dose maximum. The measurements were performed on two Varian LINACs, both employing the Millennium 120-leaf MLC. The measurements were performed at several locations in the beam with both a Sun Nuclear MapCHECK device and a PTW pinpoint ion chamber. The measured DLGs for the middle 40 MLC leaf pairs (each 0.5 cm width) at positions along a line through the CAX and perpendicular to MLC leaf travel direction were very similar, varying maximally by only 0.2 mm. The outer 20 MLC leaf pairs (each 1.0 cm width) have much lower DLG values, about 0.3 to 0.5 mm lower than the central MLC leaf pair, at their respective central line position. Overall, the mean and the maximum variation between the 0.5 cm width leaves and the 1.0 cm width leaf pairs is 0.32 mm and 0.65 mm, respectively. The spatial variation in DLG is caused by the variation of intraleaf transmission through MLC leaves. Fluences centered on the CAX would not be affected since DLG does not vary; but any fluences residing significantly off-axis with narrow sweeping leaves may exhibit significant dose differences. This is due to the fact that there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value utilized by the TPS for dose calculation. Since there are large differences in DLG between the 0.5 cm width leaf pairs and 1.0 cm width leaf pairs, there is a need

  1. Spatial variation of dosimetric leaf gap and its impact on dose delivery

    SciTech Connect

    Kumaraswamy, Lalith K.; Schmitt, Jonathan D.; Bailey, Daniel W.; Xu, Zheng Zheng; Podgorsak, Matthew B.

    2014-11-01

    Purpose: During dose calculation, the Eclipse treatment planning system (TPS) retracts the multileaf collimator (MLC) leaf positions by half of the dosimetric leaf gap (DLG) value (measured at central axis) for all leaf positions in a dynamic MLC plan to accurately model the rounded leaf ends. The aim of this study is to map the variation of DLG along the travel path of each MLC leaf pair and quantify how this variation impacts delivered dose. Methods: 6 MV DLG values were measured for all MLC leaf pairs in increments of 1.0 cm (from the line intersecting the CAX and perpendicular to MLC motion) to 13.0 cm off axis distance at dmax. The measurements were performed on two Varian linear accelerators, both employing the Millennium 120-leaf MLCs. The measurements were performed at several locations in the beam with both a Sun Nuclear MapCHECK device and a PTW pinpoint ion chamber. Results: The measured DLGs for the middle 40 MLC leaf pairs (each 0.5 cm width) at positions along a line through the CAX and perpendicular to MLC leaf travel direction were very similar, varying maximally by only 0.2 mm. The outer 20 MLC leaf pairs (each 1.0 cm width) have much lower DLG values, about 0.3–0.5 mm lower than the central MLC leaf pair, at their respective central line position. Overall, the mean and the maximum variation between the 0.5 cm width leaves and the 1.0 cm width leaf pairs are 0.32 and 0.65 mm, respectively. Conclusions: The spatial variation in DLG is caused by the variation of intraleaf transmission through MLC leaves. Fluences centered on the CAX would not be affected since DLG does not vary; but any fluences residing significantly off axis with narrow sweeping leaves may exhibit significant dose differences. This is due to the fact that there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value utilized by the TPS for dose calculation. Since there are large differences in DLG between the 0.5 cm width

  2. RICH MAPS

    EPA Science Inventory

    Michael Goodchild recently gave eight reasons why traditional maps are limited as communication devices, and how interactive internet mapping can overcome these limitations. In the past, many authorities in cartography, from Jenks to Bertin, have emphasized the importance of sim...

  3. Kentucky map

    NASA Astrophysics Data System (ADS)

    A wall-sized geological map of Kentucky, the product of 18 years of work, has just been released. Produced by the U.S. Geological Survey (USGS) in cooperation with the Kentucky Geological Survey (KGS) at the University of Kentucky, the map is unique, according to state geologist Donald Haney, because it is the first and only state map ever produced in detailed form from geologic quadrangle maps already available from the KGS.At a scale of 1:250,000, the map shows the surface distribution of various types of rock throughout the state, as well as geologic structure, faults, and surface coal beds. Numerous geologic sections, stratigraphic diagrams, correlation charts, and structure sections accompany the map. Compiled by R. C. McDowell and S. L. Moore of the USGS and by G. J . Grabowski of the KGS, the map was made by photoreducing and generalizing the detailed geologic quadrangle maps.

  4. Map adventures

    USGS Publications Warehouse

    1994-01-01

    Map Adventures, with seven accompanying lessons, is appropriate for grades K-3. Students will learn basic concepts for visualizing objects from different perspectives and how to understand /and use maps.

  5. Clinical implementation of dynamic intensity-modulated radiotherapy: Dosimetric aspects and initial experience

    PubMed Central

    Sivakumar, S. S.; Krishnamurthy, K.; Davis, C. A.; Ravichandran, R.; Kannadhasan, S.; Biunkumar, J. P.; El Ghamrawy, Kamal

    2008-01-01

    This paper describes the initial experience of quality assurance (QA) tests performed on the millennium multi-leaf collimator (mMLC) for clinical implementation of intensity-modulated radiotherapy (IMRT) using sliding window technique. The various QA tests verified the mechanical and dosimetric stability of the mMLC of linear accelerator when operated in dynamic mode (dMLC). The mechanical QA tests also verified the positional accuracy and kinetic properties of the dMLC. The stability of dMLC was analyzed qualitatively and quantitatively using radiographic film and Omnipro IMRT software. The output stability, variation in output for different sweeping gap widths, and dosimetric leaf separation were measured. Dose delivery with IMRT was verified against the dose computed by the treatment planning system (TPS). Monitor units (MUs) calculated by the planning system for the IMRT were cross-checked with independent commercial dose management software. Visual inspection and qualitative analysis showed that the leaf positioning accuracy was well within the acceptable limits. Dosimetric QA tests confirmed the dosimetric stability of the mMLC in dynamic mode. The verification of MUs using commercial software confirmed the reliability of the IMRT planning system for dose computation. The dosimetric measurements validated the fractional dose delivery. PMID:19893693

  6. SU-E-J-228: MRI-Based Planning: Dosimetric Feasibility of Dose Painting for ADCDefined Intra-Prostatic Tumor

    SciTech Connect

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

    2015-06-15

    Purpose: Apparent diffusion coefficient (ADC) map may help to delineate the gross tumor volume (GTV) in prostate gland. Dose painting with external beam radiotherapy for GTV might increase the local tumor control. The purpose of this study is to explore the maximum boosting dose on GTV using VMAT without sacrificing sparing of organs at risk (OARs) in MRI based planning. Methods: VMAT plans for 5 prostate patients were generated following the commonly used dose volume (DV) criteria based on structures contoured on T2 weighted MRI with bulk electron density assignment using electron densities derived from ICRU46. GTV for each patient was manually delineated based on ADC maps and fused to T2-weighted image set for planning study. A research planning system with Monte Carlo dose engine (Monaco, Elekta) was used to generate the VMAT plans with boosting dose on GTV gradually increased from 85Gy to 100Gy. DV parameters, including V(boosting-dose) (volume covered by boosting dose) for GTV, V75.6Gy for PTV, V45Gy, V70Gy, V72Gy and D1cc (Maximum dose to 1cc volume) for rectum and bladder, were used to measure plan quality. Results: All cases achieve at least 99.0% coverage of V(boosting-dose) on GTV and 95% coverage of V75.6Gy to the PTV. All the DV criteria, V45Gy≤50% and V70Gy≤15% for bladder and rectum, D1cc ≤77Gy (Rectum) and ≤80Gy (Bladder), V72Gy≤5% (rectum and bladder) were maintained when boosting GTV to 95Gy for all cases studied. Except for two patients, all the criteria were also met when the boosting dose goes to 100Gy. Conclusion: It is dosimetrically feasible safe to boost the dose to at least 95Gy to ADC defined GTV in prostate cancer using MRI guided VMAT delivery. Conclusion: It is dosimetrically feasible safe to boost the dose to at least 95Gy to ADC defined GTV in prostate cancer using MRI guided VMAT delivery. This research is partially supported by Elekta Inc.

  7. A computational method for estimating the dosimetric effect of intra-fraction motion on step-and-shoot IMRT and compensator plans.

    PubMed

    Waghorn, Ben J; Shah, Amish P; Ngwa, Wilfred; Meeks, Sanford L; Moore, Joseph A; Siebers, Jeffrey V; Langen, Katja M

    2010-07-21

    Intra-fraction organ motion during intensity-modulated radiation therapy (IMRT) treatment can cause differences between the planned and the delivered dose distribution. To investigate the extent of these dosimetric changes, a computational model was developed and validated. The computational method allows for calculation of the rigid motion perturbed three-dimensional dose distribution in the CT volume and therefore a dose volume histogram-based assessment of the dosimetric impact of intra-fraction motion on a rigidly moving body. The method was developed and validated for both step-and-shoot IMRT and solid compensator IMRT treatment plans. For each segment (or beam), fluence maps were exported from the treatment planning system. Fluence maps were shifted according to the target position deduced from a motion track. These shifted, motion-encoded fluence maps were then re-imported into the treatment planning system and were used to calculate the motion-encoded dose distribution. To validate the accuracy of the motion-encoded dose distribution the treatment plan was delivered to a moving cylindrical phantom using a programmed four-dimensional motion phantom. Extended dose response (EDR-2) film was used to measure a planar dose distribution for comparison with the calculated motion-encoded distribution using a gamma index analysis (3% dose difference, 3 mm distance-to-agreement). A series of motion tracks incorporating both inter-beam step-function shifts and continuous sinusoidal motion were tested. The method was shown to accurately predict the film's dose distribution for all of the tested motion tracks, both for the step-and-shoot IMRT and compensator plans. The average gamma analysis pass rate for the measured dose distribution with respect to the calculated motion-encoded distribution was 98.3 +/- 0.7%. For static delivery the average film-to-calculation pass rate was 98.7 +/- 0.2%. In summary, a computational technique has been developed to calculate the

  8. Dosimetric comparison of linear accelerator-based stereotactic radiosurgery systems

    PubMed Central

    Sharma, S. D.; Kumar, Sudhir; Dagaonkar, S. S.; Bisht, Geetika; Dayanand, S.; Devi, Reena; Deshpande, S. S.; Chaudhary, S.; Bhatt, B. C.; Kannan, S.

    2007-01-01

    Stereotactic radiosurgery (SRS) is a special radiotherapy technique used to irradiate intracranial lesions by 3-D arrangements of narrow photon beams eliminating the needs of invasive surgery. Three different tertiary collimators, namely BrainLab and Radionics circular cones and BrainLab micro multileaf collimator (mMLC), are used for linear accelerator-based SRS systems (X-Knife). Output factor (St), tissue maximum ratio (TMR) and off axis ratio (OAR) of these three SRS systems were measured using CC01 (Scanditronix/ Welhofer) and Pinpoint (PTW) cylindrical and Markus plane parallel ionization chambers as well as TLD and radiochromic film. Measurement results of CC01 and Pinpoint chambers were very close to each other which indicate that further reduction in volume and physical dimensions of cylindrical ionization chamber is not necessary for SRS/SRT dosimetry. Output factors of BrainLab and Radionics SRS cones were very close to each other while output factors of equivalent diameter mMLC field were different from SRS circular cones. TMR of the three SRS systems compared were very close to one another. OAR of Radionics cone and BrainLab mMLC were very close to each other, within 2%. However, OARs of BrainLab cone were found comparable to OARs of Radionics cone and BrainLab mMLC within maximum variation of 4%. In addition, user-measured similar data of other three mMLC X-Knives were compared with the mMLC X-Knife data measured in this work and found comparable. The concept of switching over to mMLC-based SRS/SRT is thus validated from dosimetric characteristics as well. PMID:21217914

  9. A revised dosimetric model of the adult head and brain

    SciTech Connect

    Bouchet, L.G.; Bolch, W.E.; Weber, D.A.

    1996-06-01

    During the last decade, new radiopharmaceutical have been introduced for brain imaging. The marked differences of these tracers in tissue specificity within the brain and their increasing use for diagnostic studies support the need for a more anthropomorphic model of the human brain and head. Brain and head models developed in the past have been only simplistic representations of this anatomic region. For example, the brain within the phantom of MIRD Pamphlet No. 5 Revised is modeled simply as a single ellipsoid of tissue With no differentiation of its internal structures. To address this need, the MIRD Committee established a Task Group in 1992 to construct a more detailed brain model to include the cerebral cortex, the white matter, the cerebellum, the thalamus, the caudate nucleus, the lentiform nucleus, the cerebral spinal fluid, the lateral ventricles, and the third ventricle. This brain model has been included within a slightly modified version of the head model developed by Poston et al. in 1984. This model has been incorporated into the radiation transport code EGS4 so as to calculate photon and electron absorbed fractions in the energy range 10 keV to 4 MeV for each of thirteen sources in the brain. Furthermore, explicit positron transport have been considered, separating the contribution by the positron itself and its associated annihilations photons. No differences are found between the electron and positron absorbed fractions; however, for initial energies of positrons greater than {approximately}0.5 MeV, significant differences are found between absorbed fractions from explicit transport of annihilation photons and those from an assumed uniform distribution of 0.511-MeV photons. Subsequently, S values were calculated for a variety of beta-particle and positron emitters brain imaging agents. Moreover, pediatric head and brain dosimetric models are currently being developed based on this adult head model.

  10. Radioembolization of Hepatic Lesions from a Radiobiology and Dosimetric Perspective

    PubMed Central

    Cremonesi, Marta; Chiesa, Carlo; Strigari, Lidia; Ferrari, Mahila; Botta, Francesca; Guerriero, Francesco; De Cicco, Concetta; Bonomo, Guido; Orsi, Franco; Bodei, Lisa; Di Dia, Amalia; Grana, Chiara Maria; Orecchia, Roberto

    2014-01-01

    Radioembolization (RE) of liver cancer with 90Y-microspheres has been applied in the last two decades with notable responses and acceptable toxicity. Two types of microspheres are available, glass and resin, the main difference being the activity/sphere. Generally, administered activities are established by empirical methods and differ for the two types. Treatment planning based on dosimetry is a prerogative of few centers, but has notably gained interest, with evidence of predictive power of dosimetry on toxicity, lesion response, and overall survival (OS). Radiobiological correlations between absorbed doses and toxicity to organs at risk, and tumor response, have been obtained in many clinical studies. Dosimetry methods have evolved from the macroscopic approach at the organ level to voxel analysis, providing absorbed dose spatial distributions and dose–volume histograms (DVH). The well-known effects of the external beam radiation therapy (EBRT), such as the volume effect, underlying disease influence, cumulative damage in parallel organs, and different tolerability of re-treatment, have been observed also in RE, identifying in EBRT a foremost reference to compare with. The radiobiological models – normal tissue complication probability and tumor control probability – and/or the style (DVH concepts) used in EBRT are introduced in RE. Moreover, attention has been paid to the intrinsic different activity distribution of resin and glass spheres at the microscopic scale, with dosimetric and radiobiological consequences. Dedicated studies and mathematical models have developed this issue and explain some clinical evidences, e.g., the shift of dose to higher toxicity thresholds using glass as compared to resin spheres. This paper offers a comprehensive review of the literature incident to dosimetry and radiobiological issues in RE, with the aim to summarize the results and to identify the most useful methods and information that should accompany future studies

  11. Dosimetric Analysis of Radiation-induced Gastric Bleeding

    SciTech Connect

    Feng, Mary; Normolle, Daniel; Pan, Charlie C.; Dawson, Laura A.; Amarnath, Sudha; Ensminger, William D.; Lawrence, Theodore S.; Ten Haken, Randall K.

    2012-09-01

    Purpose: Radiation-induced gastric bleeding has been poorly understood. In this study, we described dosimetric predictors for gastric bleeding after fractionated radiation therapy. Methods and Materials: The records of 139 sequential patients treated with 3-dimensional conformal radiation therapy (3D-CRT) for intrahepatic malignancies were reviewed. Median follow-up was 7.4 months. The parameters of a Lyman normal tissue complication probability (NTCP) model for the occurrence of {>=}grade 3 gastric bleed, adjusted for cirrhosis, were fitted to the data. The principle of maximum likelihood was used to estimate parameters for NTCP models. Results: Sixteen of 116 evaluable patients (14%) developed gastric bleeds at a median time of 4.0 months (mean, 6.5 months; range, 2.1-28.3 months) following completion of RT. The median and mean maximum doses to the stomach were 61 and 63 Gy (range, 46-86 Gy), respectively, after biocorrection of each part of the 3D dose distributions to equivalent 2-Gy daily fractions. The Lyman NTCP model with parameters adjusted for cirrhosis predicted gastric bleed. Best-fit Lyman NTCP model parameters were n=0.10 and m=0.21 and with TD{sub 50} (normal) = 56 Gy and TD{sub 50} (cirrhosis) = 22 Gy. The low n value is consistent with the importance of maximum dose; a lower TD{sub 50} value for the cirrhosis patients points out their greater sensitivity. Conclusions: This study demonstrates that the Lyman NTCP model has utility for predicting gastric bleeding and that the presence of cirrhosis greatly increases this risk. These findings should facilitate the design of future clinical trials involving high-dose upper abdominal radiation.

  12. Dosimetric Analysis of Radiation-Induced Gastric Bleeding

    PubMed Central

    Feng, Mary; Normolle, Daniel; Pan, Charlie C.; Dawson, Laura A.; Amarnath, Sudha; Ensminger, William D.; Lawrence, Theodore S.; Ten Haken, Randall K.

    2012-01-01

    Purpose Radiation-induced gastric bleeding has been poorly understood. In this study, we describe dosimetric predictors for gastric bleeding after fractionated radiotherapy and compare several predictive models. Materials & Methods The records of 139 sequential patients treated with 3-dimensional conformal radiotherapy (3D-CRT) for intrahepatic malignancies between January 1999 and April 2002 were reviewed. Median follow-up was 7.4 months. Logistic regression and Lyman normal tissue complication probability (NTCP) models for the occurrence of ≥ grade 3 gastric bleed were fit to the data. The principle of maximum likelihood was used to estimate parameters for all models. Results Sixteen of 116 evaluable patients (14%) developed gastric bleeds, at a median time of 4.0 months (mean 6.5 months, range 2.1–28.3 months) following completion of RT. The median and mean of the maximum doses to the stomach were 61 and 63 Gy (range 46 Gy–86 Gy), respectively, after bio-correction to equivalent 2 Gy daily fractions. The Lyman NTCP model with parameters adjusted for cirrhosis was most predictive of gastric bleed (AUROC=0.92). Best fit Lyman NTCP model parameters were n =0.10, and m =0.21, with TD50(normal) =56 Gy and TD50(cirrhosis) = 22 Gy. The low n value is consistent with the importance of maximum dose; a lower TD50 value for the cirrhosis patients points out their greater sensitivity. Conclusion This study demonstrates that the Lyman NTCP model has utility for predicting gastric bleeding, and that the presence of cirrhosis greatly increases this risk. These findings should facilitate the design of future clinical trials involving high-dose upper abdominal radiation. PMID:22541965

  13. Determination of mass attenuation coefficient of low-Z dosimetric materials

    NASA Astrophysics Data System (ADS)

    El-Khayatt, A. M.; Ali, A. M.; Singh, Vishwanath P.; Badiger, N. M.

    2014-12-01

    The mass attenuation coefficients of some low-Z dosimetric materials with potential applications in dosimetry, medical and radiation protection have been investigated using the Monte Carlo simulation code Monte Carlo N-Particle (MCNP). Appreciable variations are noted for the mass attenuation coefficient by changing the photon energy. The MCNP-simulated parameters are compared with the experimental data wherever possible and theoretical values through the WinXcom program. The simulated results obtained by MCNP generally agree well with the experiment and WinXcom predictions for various low-Z dosimetric and tissue substitute materials. In addition, the mass attenuation coefficients around the k-edges for low-Z dosimetric materials estimated from the MCNP code agree very well with WinXcom prediction. Finally, the results indicate that this simulation process can be followed to determine the interaction parameters of gamma rays in such low-Z materials for which there are no satisfactory experimental values available.

  14. NOTE: Monte Carlo dosimetric study of the BEBIG Co-60 HDR source

    NASA Astrophysics Data System (ADS)

    Ballester, F.; Granero, D.; Pérez-Calatayud, J.; Casal, E.; Agramunt, S.; Cases, R.

    2005-11-01

    Although not as widespread as Ir-192, Co-60 is also available on afterloading equipment devoted to high dose rate brachytherapy, mainly addressed to the treatment of gynaecological lesions. The purpose of this study is to obtain the dosimetric parameters of the Co-60 source used by the BEBIG MultiSource remote afterloader (BEBIG GmbH, Germany) for which there are no dosimetric data available in the literature. The Monte Carlo code GEANT4 has been used to obtain the TG43 parameters and the 2D dose rate table in Cartesian coordinates of the BEBIG Co-60 HDR source. The dose rate constant, radial dose function and anisotropy function have been calculated and are presented in a tabular form as well as a detailed 2D dose rate table in Cartesian coordinates. These dosimetric datasets can be used as input data and to validate the treatment planning system calculations.

  15. Monte Carlo dosimetric study of the BEBIG Co-60 HDR source.

    PubMed

    Ballester, F; Granero, D; Pérez-Calatayud, J; Casal, E; Agramunt, S; Cases, R

    2005-11-01

    Although not as widespread as Ir-192, Co-60 is also available on afterloading equipment devoted to high dose rate brachytherapy, mainly addressed to the treatment of gynaecological lesions. The purpose of this study is to obtain the dosimetric parameters of the Co-60 source used by the BEBIG MultiSource remote afterloader (BEBIG GmbH, Germany) for which there are no dosimetric data available in the literature. The Monte Carlo code GEANT4 has been used to obtain the TG43 parameters and the 2D dose rate table in Cartesian coordinates of the BEBIG Co-60 HDR source. The dose rate constant, radial dose function and anisotropy function have been calculated and are presented in a tabular form as well as a detailed 2D dose rate table in Cartesian coordinates. These dosimetric datasets can be used as input data and to validate the treatment planning system calculations. PMID:16237230

  16. A new fully integrated X-ray irradiator system for dosimetric research.

    PubMed

    Richter, D; Mittelstraß, D; Kreutzer, S; Pintaske, R; Dornich, K; Fuchs, M

    2016-06-01

    A fully housed X-ray irradiator was developed for use within lexsyg or Magnettech desktop equipment. The importance of hardening of the low energy photon radiation is discussed, its performance and feasibility is empirically shown and sustained by basic numerical simulations. Results of the latter for various materials are given for different X-ray source settings in order to provide estimates on the required setup for the irradiation of different geometries and materials. A Si-photodiode provides real-time monitoring of the X-ray-irradiator designed for use in dosimetric dating and other dosimetric application where irradiation of small samples or dosemeters is required. PMID:27041090

  17. Mapping Van

    NASA Technical Reports Server (NTRS)

    1994-01-01

    A NASA Center for the Commercial Development of Space (CCDS) - developed system for satellite mapping has been commercialized for the first time. Global Visions, Inc. maps an area while driving along a road in a sophisticated mapping van equipped with satellite signal receivers, video cameras and computer systems for collecting and storing mapping data. Data is fed into a computerized geographic information system (GIS). The resulting amps can be used for tax assessment purposes, emergency dispatch vehicles and fleet delivery companies as well as other applications.

  18. Benchmarking Dosimetric Quality Assessment of Prostate Intensity-Modulated Radiotherapy

    SciTech Connect

    Senthi, Sashendra; Gill, Suki S.; Haworth, Annette; Kron, Tomas; Cramb, Jim; Rolfo, Aldo; Thomas, Jessica; Duchesne, Gillian M.; Hamilton, Christopher H.; Joon, Daryl Lim; Bowden, Patrick; Foroudi, Farshad

    2012-02-01

    Purpose: To benchmark the dosimetric quality assessment of prostate intensity-modulated radiotherapy and determine whether the quality is influenced by disease or treatment factors. Patients and Methods: We retrospectively analyzed the data from 155 consecutive men treated radically for prostate cancer using intensity-modulated radiotherapy to 78 Gy between January 2007 and March 2009 across six radiotherapy treatment centers. The plan quality was determined by the measures of coverage, homogeneity, and conformity. Tumor coverage was measured using the planning target volume (PTV) receiving 95% and 100% of the prescribed dose (V{sub 95%} and V{sub 100%}, respectively) and the clinical target volume (CTV) receiving 95% and 100% of the prescribed dose. Homogeneity was measured using the sigma index of the PTV and CTV. Conformity was measured using the lesion coverage factor, healthy tissue conformity index, and the conformity number. Multivariate regression models were created to determine the relationship between these and T stage, risk status, androgen deprivation therapy use, treatment center, planning system, and treatment date. Results: The largest discriminatory measurements of coverage, homogeneity, and conformity were the PTV V{sub 95%}, PTV sigma index, and conformity number. The mean PTV V{sub 95%} was 92.5% (95% confidence interval, 91.3-93.7%). The mean PTV sigma index was 2.10 Gy (95% confidence interval, 1.90-2.20). The mean conformity number was 0.78 (95% confidence interval, 0.76-0.79). The treatment center independently influenced the coverage, homogeneity, and conformity (all p < .0001). The planning system independently influenced homogeneity (p = .038) and conformity (p = .021). The treatment date independently influenced the PTV V{sub 95%} only, with it being better at the start (p = .013). Risk status, T stage, and the use of androgen deprivation therapy did not influence any aspect of plan quality. Conclusion: Our study has benchmarked measures

  19. Dosimetric measurements of Onyx embolization material for stereotactic radiosurgery

    SciTech Connect

    Roberts, Donald A.; Balter, James M.; Chaudhary, Neeraj; Gemmete, Joseph J.; Pandey, Aditya S.

    2012-11-15

    Purpose: Arteriovenous malformations are often treated with a combination of embolization and stereotactic radiosurgery. Concern has been expressed in the past regarding the dosimetric properties of materials used in embolization and the effects that the introduction of these materials into the brain may have on the quality of the radiosurgery plan. To quantify these effects, the authors have taken large volumes of Onyx 34 and Onyx 18 (ethylene-vinyl alcohol copolymer doped with tantalum) and measured the attenuation and interface effects of these embolization materials. Methods: The manufacturer provided large cured volumes ({approx}28 cc) of both Onyx materials. These samples were 8.5 cm in diameter with a nominal thickness of 5 mm. The samples were placed on a block tray above a stack of solid water with an Attix chamber at a depth of 5 cm within the stack. The Attix chamber was used to measure the attenuation. These measurements were made for both 6 and 16 MV beams. Placing the sample directly on the solid water stack and varying the thickness of solid water between the sample and the Attix chamber measured the interface effects. The computed tomography (CT) numbers for bulk material were measured in a phantom using a wide bore CT scanner. Results: The transmission through the Onyx materials relative to solid water was approximately 98% and 97% for 16 and 6 MV beams, respectively. The interface effect shows an enhancement of approximately 2% and 1% downstream for 16 and 6 MV beams. CT numbers of approximately 2600-3000 were measured for both materials, which corresponded to an apparent relative electron density (RED) {rho}{sub e}{sup w} to water of approximately 2.7-2.9 if calculated from the commissioning data of the CT scanner. Conclusions: We performed direct measurements of attenuation and interface effects of Onyx 34 and Onyx 18 embolization materials with large samples. The introduction of embolization materials affects the dose distribution of a MV

  20. Predicting Pneumonitis Risk: A Dosimetric Alternative to Mean Lung Dose

    SciTech Connect

    Tucker, Susan L.; Mohan, Radhe; Liengsawangwong, Raweewan; Martel, Mary K.; Liao Zhongxing

    2013-02-01

    Purpose: To determine whether the association between mean lung dose (MLD) and risk of severe (grade {>=}3) radiation pneumonitis (RP) depends on the dose distribution pattern to normal lung among patients receiving 3-dimensional conformal radiation therapy for non-small-cell lung cancer. Methods and Materials: Three cohorts treated with different beam arrangements were identified. One cohort (2-field boost [2FB]) received 2 parallel-opposed (anteroposterior-posteroanterior) fields per fraction initially, followed by a sequential boost delivered using 2 oblique beams. The other 2 cohorts received 3 or 4 straight fields (3FS and 4FS, respectively), ie, all fields were irradiated every day. The incidence of severe RP was plotted against MLD in each cohort, and data were analyzed using the Lyman-Kutcher-Burman (LKB) model. Results: The incidence of grade {>=}3 RP rose more steeply as a function of MLD in the 2FB cohort (N=120) than in the 4FS cohort (N=138), with an intermediate slope for the 3FS group (N=99). The estimated volume parameter from the LKB model was n=0.41 (95% confidence interval, 0.15-1.0) and led to a significant improvement in fit (P=.05) compared to a fit with volume parameter fixed at n=1 (the MLD model). Unlike the MLD model, the LKB model with n=0.41 provided a consistent description of the risk of severe RP in all three cohorts (2FB, 3FS, 4FS) simultaneously. Conclusions: When predicting risk of grade {>=}3 RP, the mean lung dose does not adequately take into account the effects of high doses. Instead, the effective dose, computed from the LKB model using volume parameter n=0.41, may provide a better dosimetric parameter for predicting RP risk. If confirmed, these findings support the conclusion that for the same MLD, high doses to small lung volumes ('a lot to a little') are worse than low doses to large volumes ('a little to a lot').

  1. Dosimetric characteristics of a new unit for electronic skin brachytherapy

    PubMed Central

    Garcia-Martinez, Teresa; Chan, Jan-Pieter; Perez-Calatayud, Jose

    2014-01-01

    Purpose Brachytherapy with radioactive high dose rate (HDR) 192Ir source is applied to small skin cancer lesions, using surface applicators, i.e. Leipzig or Valencia type. New developments in the field of radiotherapy for skin cancer include electronic brachytherapy. This technique involves the placement of an HDR X-ray source close to the skin, therefore combining the benefits of brachytherapy with the reduced shielding requirements and targeted energy of low energy X-rays. Recently, the Esteya® Electronic Brachytherapy System (Esteya EBS, Elekta AB-Nucletron, Stockholm, Sweden) has been developed specifically for HDR brachytherapy treatment of surface lesions. The system provides radionuclide free HDR brachytherapy by means of a small 69.5 kV X-ray source. The purpose of this study is to obtain the dosimetric characterization required for clinical implementation, providing the detailed methodology to perform the commissioning. Material and methods Flatness, symmetry and penumbra, percentage of depth dose (PDD), kV stability, HVL, output, spectrum, linearity, and leakage have been evaluated for a set of applicators (from 10 mm to 30 mm in diameter). Results Flatness and symmetry resulted better than 5% with around 1 mm of penumbra. The depth dose gradient is about 7%/mm. A kV value of 68.4 ± 1.0 kV (k = 1) was obtained, in good agreement with manufacturer data (69.5 kV). HVL was 1.85 mm Al. Dose rate for a typical 6 Gy to 7 Gy prescription resulted about 3.3 Gy/min and the leakage value was < 100 µGy/min. Conclusions The new Esteya® Electronic Brachytherapy System presents excellent flatness and penumbra as with the Valencia applicator case, combined with an improved PDD, allowing treatment of lesions of up to a depth of 5 mm in combination with reduced treatment duration. The Esteya unit allows HDR brachytherapy superficial treatment within a minimally shielded environment due its low energy. PMID:24790622

  2. Undersea Mapping.

    ERIC Educational Resources Information Center

    DiSpezio, Michael A.

    1991-01-01

    Presented is a cooperative learning activity in which students assume different roles in an effort to produce a relief map of the ocean floor. Materials, procedures, definitions, student roles, and questions are discussed. A reproducible map for the activity is provided. (CW)

  3. Question Mapping

    ERIC Educational Resources Information Center

    Martin, Josh

    2012-01-01

    After accepting the principal position at Farmersville (TX) Junior High, the author decided to increase instructional rigor through question mapping because of the success he saw using this instructional practice at his prior campus. Teachers are the number one influence on student achievement (Marzano, 2003), so question mapping provides a…

  4. Map Adventures.

    ERIC Educational Resources Information Center

    Geological Survey (Dept. of Interior), Reston, VA.

    This curriculum packet about maps, with seven accompanying lessons, is appropriate for students in grades K-3. Students learn basic concepts for visualizing objects from different perspectives and how to understand and use maps. Lessons in the packet center on a story about a little girl, Nikki, who rides in a hot-air balloon that gives her, and…

  5. Evaluation of the applicability of pinpoint ion chambers for SRS dosimetric quality assurance

    NASA Astrophysics Data System (ADS)

    Baek, Jong Geun; Jang, Hyun Soo; Kim, Eng Chan; Lee, Yong Hee; Oh, Young Kee; Kim, Sung Kyu

    2015-06-01

    The aim of the present study was to evaluate the applicability of a Pinpoint ion chamber for the measurement of the absolute dose for dosimetric quality assurance (QA) under the same conditions as are used for actual stereotactic radiosurgery (SRS). A PTW 31014 Pinpoint chamber with a active volume of 0.015 cm3 was used to measure the absolute doses of small beams. The PTW 60003 natural diamond detector was used as a reference dosimeter. A custom-made cylindrical acrylic phantom (15 cm diameter, 15 cm long) was produced to obtain measurements, and a noncoplanar arc plan was devised to deliver a prescription dose (15-25 Gy) to 80% of the maximum dose to the target in a single fraction by using the BrainLAB planning system. All irradiations were performed by using a Varian Clinac IX 6 MV equipped with a micro-multileaf-collimators (m3) designed by BrainLAB. The acceptability criterion used was a dose difference of less than 3%. The diameter of the target volume was considered the standard parameter in the present study and was used to divide the cases into two groups, that is, a ≤ 10 mm target diameter group (10 cases) and a > 10 mm target diameter group (13 cases). For the Pinpoint chamber and target diameters of ≤ 10 mm, dosimetric uncertainties of > 3% were seen in 4 of the 10 cases, and differences ranged widely from 0.7% to 4.85%. On the other hand, for the Pinpoint chamber and target diameters of > 10 mm all dose differences were less than 1.6%, and the mean discrepancy was 0.81%. A highly significant, but moderate, correlation between dosimetric uncertainties and all target diameters was observed for the Pinpoint chamber (R2 = 0.483, p 0.001). This result indicates that Pinpoint chambers exhibit a field-size dependency when used for SRS dosimetric QA. Based on the results of the present study, we conclude that the use of a Pinpoint chamber for verification of SRS dosimetric QA is unsuitable for all field sizes, but that it can be used to verify the

  6. Patient feature based dosimetric Pareto front prediction in esophageal cancer radiotherapy

    SciTech Connect

    Wang, Jiazhou; Zhao, Kuaike; Peng, Jiayuan; Xie, Jiang; Chen, Junchao; Zhang, Zhen; Hu, Weigang; Jin, Xiance; Studenski, Matthew

    2015-02-15

    Purpose: To investigate the feasibility of the dosimetric Pareto front (PF) prediction based on patient’s anatomic and dosimetric parameters for esophageal cancer patients. Methods: Eighty esophagus patients in the authors’ institution were enrolled in this study. A total of 2928 intensity-modulated radiotherapy plans were obtained and used to generate PF for each patient. On average, each patient had 36.6 plans. The anatomic and dosimetric features were extracted from these plans. The mean lung dose (MLD), mean heart dose (MHD), spinal cord max dose, and PTV homogeneity index were recorded for each plan. Principal component analysis was used to extract overlap volume histogram (OVH) features between PTV and other organs at risk. The full dataset was separated into two parts; a training dataset and a validation dataset. The prediction outcomes were the MHD and MLD. The spearman’s rank correlation coefficient was used to evaluate the correlation between the anatomical features and dosimetric features. The stepwise multiple regression method was used to fit the PF. The cross validation method was used to evaluate the model. Results: With 1000 repetitions, the mean prediction error of the MHD was 469 cGy. The most correlated factor was the first principal components of the OVH between heart and PTV and the overlap between heart and PTV in Z-axis. The mean prediction error of the MLD was 284 cGy. The most correlated factors were the first principal components of the OVH between heart and PTV and the overlap between lung and PTV in Z-axis. Conclusions: It is feasible to use patients’ anatomic and dosimetric features to generate a predicted Pareto front. Additional samples and further studies are required improve the prediction model.

  7. Dosimetric effects of endorectal balloons on intensity-modulated radiation therapy plans for prostate cancer

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Sung; Chung, Jin-Beom; Kim, In-Ah; Eom, Keun-Yong

    2013-10-01

    We used an endorectal balloon (ERB) for prostate immobilization during intensity-modulated radiotherapy (IMRT) for prostate cancer treatment. To investigate the dosimetric effects of ERB-filling materials, we changed the ERB Hounsfield unit (HU) from 0 to 1000 HU in 200-HU intervals to simulate the various ERB fillings; 0 HU simulated a water-filled ERB, and 1000 HU simulated the densest material-filled ERB. Dosimetric data (coverage, homogeneity, conformity, maximal dose, and typical volume dose) for the tumor and the organs at risk (OARs) were evaluated in prostate IMRT treatment plans with 6-MV and 15-MV beams. The tumor coverage appeared to differ by approximately 1%, except for the clinical target volume (CTV) V100% and the planning target volume (PTV) V100%. The largest difference for the various ERB fillings was observed in the PTV V100%. In spite of increasing HU, the prostate IMRT plans at both energies had relatively low dosimetric effects on the PTV and the CTV. However, the maximal and the typical volume doses (D25%, D30%, and D50%) to the rectal wall and the bladder increased with increasing HU. For an air-filled ERB, the maximal doses to the rectal wall and the monitor units were lower than the corresponding values for the water-filled and the densest material-filled ERBs. An air-filled ERB spared the rectal wall because of its dosimetric effect. Thus, we conclude that the use of an air-filled ERB provides a dosimetric benefit to the rectal wall without a loss of target coverage and is an effective option for prostate IMRT treatment.

  8. Study of the Phototransference in GR-200 Dosimetric Material and its Convenience for Dose Re-estimation

    SciTech Connect

    Baly, L.; Otazo, M. R.; Molina, D.; Pernas, R.

    2006-09-08

    A study of the phototransference of charges from deep to dosimetric traps in GR-200 material is presented and its convenience for dose re-estimation in the dose range between 2 and 100mSv is also analyzed. The recovering coefficient (RC) defined as the ratio between the phototransferred thermoluminescence (PTTL) and the original thermoluminescence (TL) of the dosimetric trap was used to evaluate the ratio of phototransferred charges from deep traps and the original charges in the dosimetric traps. The results show the convenience of this method for dose re-estimation for this material in the selected range of doses.

  9. Surface and superficial dose dosimetric verification for postmastectomy radiotherapy

    SciTech Connect

    Shiau, An-Cheng; Chiu, Min-Chi; Chen, Tung-Ho; Chiou, Jeng-Fong; Shueng, Pei-Wei; Chen, Shang-Wen; Chen, Wei-Li; Kuan, Wei-Peng

    2012-01-01

    In patients given postmastectomy radiotherapy (PMRT), the chest wall is a very thin layer of soft tissue with a low-density lung tissue behind. Chest wall treated in this situation with a high-energy photon beam presents a high dosimetric uncertainty region for both calculation and measurement. The purpose of this study was to measure and to evaluate the surface and superficial doses for patients requiring PMRT with different treatment techniques. An elliptic cylinder cork and superflab boluses were used to simulate the lung and the chest wall, respectively. Sets of computed tomography (CT) images with different chest wall thicknesses were acquired for the study phantom. Hypothetical clinical target volumes (CTVs) were outlined and modified to fit a margin of 1-3 mm, depending on the chest wall thickness, away from the surface for the sets of CT images. The planning target volume (PTV) was initially created by expanding an isotropic 3-mm margin from the CTV, and then a margin of 3 mm was shrunk from the phantom surface to avoid artifact-driven results in the beam-let intensity. Treatment techniques using a pair of tangential wedged fields (TWFs) and 4-field intensity-modulated radiation therapy (IMRT) were designed with a prescribed fraction dose (D{sub p}) of 180 cGy. Superficial dose profiles around the phantom circumference at depths of 0, 1, 2, 3, and 5 mm were obtained for each treatment technique using radiochromic external beam therapy (EBT) films. EBT film exhibits good characteristics for dose measurements in the buildup region. Underdoses at the median and lateral regions of the TWF plans were shown. The dose profiles at shallow depths for the TWF plans show a dose buildup about 3 mm at the median and lateral tangential incident regions with a surface dose of about 52% of D{sub p}. The dose was gradually increased toward the most obliquely tangential angle with a maximum dose of about 118% of D{sub p.} Dose profiles were more uniform in the PTV region for

  10. Semantic Mapping.

    ERIC Educational Resources Information Center

    Johnson, Dale D.; And Others

    1986-01-01

    Describes semantic mapping, an effective strategy for vocabulary instruction that involves the categorical structuring of information in graphic form and requires students to relate new words to their own experience and prior knowledge. (HOD)

  11. Mapping Biodiversity.

    ERIC Educational Resources Information Center

    World Wildlife Fund, Washington, DC.

    This document features a lesson plan that examines how maps help scientists protect biodiversity and how plants and animals are adapted to specific ecoregions by comparing biome, ecoregion, and habitat. Samples of instruction and assessment are included. (KHR)

  12. Map Separates

    USGS Publications Warehouse

    U.S. Geological Survey

    2001-01-01

    U.S. Geological Survey (USGS) topographic maps are printed using up to six colors (black, blue, green, red, brown, and purple). To prepare your own maps or artwork based on maps, you can order separate black-and-white film positives or negatives for any color printed on a USGS topographic map, or for one or more of the groups of related features printed in the same color on the map (such as drainage and drainage names from the blue plate.) In this document, examples are shown with appropriate ink color to illustrate the various separates. When purchased, separates are black-and-white film negatives or positives. After you receive a film separate or composite from the USGS, you can crop, enlarge or reduce, and edit to add or remove details to suit your special needs. For example, you can adapt the separates for making regional and local planning maps or for doing many kinds of studies or promotions by using the features you select and then printing them in colors of your choice.

  13. Venus mapping

    NASA Technical Reports Server (NTRS)

    Batson, R. M.; Morgan, H. F.; Sucharski, Robert

    1991-01-01

    Semicontrolled image mosaics of Venus, based on Magellan data, are being compiled at 1:50,000,000, 1:10,000,000, 1:5,000,000, and 1:1,000,000 scales to support the Magellan Radar Investigator (RADIG) team. The mosaics are semicontrolled in the sense that data gaps were not filled and significant cosmetic inconsistencies exist. Contours are based on preliminary radar altimetry data that is subjected to revision and improvement. Final maps to support geologic mapping and other scientific investigations, to be compiled as the dataset becomes complete, will be sponsored by the Planetary Geology and Geophysics Program and/or the Venus Data Analysis Program. All maps, both semicontrolled and final, will be published as I-maps by the United States Geological Survey. All of the mapping is based on existing knowledge of the spacecraft orbit; photogrammetric triangulation, a traditional basis for geodetic control on planets where framing cameras were used, is not feasible with the radar images of Venus, although an eventual shift of coordinate system to a revised spin-axis location is anticipated. This is expected to be small enough that it will affect only large-scale maps.

  14. ADVANCES IN EXPERIMENTAL EXPOSURE METHODS AND DOSIMETRIC TECHNIQUES USED IN RADIO-FREQUENCY RADIATION BIOLOGICAL EFFECTS STUDIES

    EPA Science Inventory

    The various techniques and methodologies used for exposure and dosimetric assessment in radio-frequency (RF) biological effects studies are reviewed. Techniques are compared and the advantages and disadvantages of each are discussed. Significant progress has been made during the ...

  15. Dosimetric effects of rotational offsets in stereotactic body radiation therapy (SBRT) for lung cancer

    SciTech Connect

    Yang, Yun; Catalano, Suzanne; Kelsey, Chris R.; Yoo, David S.; Yin, Fang-Fang; Cai, Jing

    2014-04-01

    To quantitatively evaluate dosimetric effects of rotational offsets in stereotactic body radiation therapy (SBRT) for lung cancer. Overall, 11 lung SBRT patients (8 female and 3 male; mean age: 75.0 years) with medially located tumors were included. Treatment plans with simulated rotational offsets of 1°, 3°, and 5° in roll, yaw, and pitch were generated and compared with the original plans. Both clockwise and counterclockwise rotations were investigated. The following dosimetric metrics were quantitatively evaluated: planning target volume coverage (PTV V{sub 100%}), max PTV dose (PTV D{sub max}), percentage prescription dose to 0.35 cc of cord (cord D{sub 0.35} {sub cc}), percentage prescription dose to 0.35 cc and 5 cc of esophagus (esophagus D{sub 0.35} {sub cc} and D{sub 5} {sub cc}), and volume of the lungs receiving at least 20 Gy (lung V{sub 20}). Statistical significance was tested using Wilcoxon signed rank test at the significance level of 0.05. Overall, small differences were found in all dosimetric matrices at all rotational offsets: 95.6% of differences were < 1% or < 1 Gy. Of all rotational offsets, largest change in PTV V{sub 100%}, PTV D{sub max}, cord D{sub 0.35} {sub cc}, esophagus D{sub 0.35} {sub cc}, esophagus D{sub 5} {sub cc}, and lung V{sub 20} was − 8.36%, − 6.06%, 11.96%, 8.66%, 6.02%, and − 0.69%, respectively. No significant correlation was found between any dosimetric change and tumor-to-cord/esophagus distances (R{sup 2} range: 0 to 0.44). Larger dosimetric changes and intersubject variations were observed at larger rotational offsets. Small dosimetric differences were found owing to rotational offsets up to 5° in lung SBRT for medially located tumors. Larger intersubject variations were observed at larger rotational offsets.

  16. Will weight loss cause significant dosimetric changes of target volumes and organs at risk in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy?

    SciTech Connect

    Chen, Chuanben; Fei, Zhaodong; Chen, Lisha; Bai, Penggang; Lin, Xiang; Pan, Jianji

    2014-04-01

    This study aimed to quantify dosimetric effects of weight loss for nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiation therapy (IMRT). Overall, 25 patients with NPC treated with IMRT were enrolled. We simulated weight loss during IMRT on the computer. Weight loss model was based on the planning computed tomography (CT) images. The original external contour of head and neck was labeled plan 0, and its volume was regarded as pretreatment normal weight. We shrank the external contour with different margins (2, 3, and 5 mm) and generated new external contours of head and neck. The volumes of reconstructed external contours were regarded as weight during radiotherapy. After recontouring outlines, the initial treatment plan was mapped to the redefined CT scans with the same beam configurations, yielding new plans. The computer model represented a theoretical proportional weight loss of 3.4% to 13.7% during the course of IMRT. The dose delivered to the planning target volume (PTV) of primary gross tumor volume and clinical target volume significantly increased by 1.9% to 2.9% and 1.8% to 2.9% because of weight loss, respectively. The dose to the PTV of gross tumor volume of lymph nodes fluctuated from −2.0% to 1.0%. The dose to the brain stem and the spinal cord was increased (p < 0.001), whereas the dose to the parotid gland was decreased (p < 0.001). Weight loss may lead to significant dosimetric change during IMRT. Repeated scanning and replanning for patients with NPC with an obvious weight loss may be necessary.

  17. Dosimetric properties and stability of thermoluminescent foils made from LiF:Mg,Cu,P or CaSO4:Dy during long-term use

    NASA Astrophysics Data System (ADS)

    Kłosowski, M.; Liszka, M.; Kopeć, R.; Bilski, P.; Kędzierska, D.

    2014-11-01

    A few dosimetric systems based on thermoluminescence [TL] foils were developed in recent years (Nariyama et al. 2006, Radiat. Prot. Dosim. 120, 213-218; Olko et al. 2006 Radiat. Prot. Dosim. 118, 213-218) (Czopyk et al. 2008, Radiat. Meas., 43, 977-980; Kłosowski et al. 2010, Radiat. Meas., 45, 719-721; Kopeć et al. 2013, Radiat.Meas., 56, 380-383). Major application of these systems is mapping of 2D dose distribution for medical treatment plan verification, similarly to photochromic or radiochromic films. The advantage of TL foils compared to other films is their re-usability. In this work we present dosimetric properties as dose linearity and fadding of the foils made from LiF:Mg,Cu,P or CaSO4:Dy phosphors and high temperature polymers. Both types of the foils have good linearity in the range 1-20 Gy for LiF:Mg,Cu,P and 0.1-2 Gy for CaSO4:Dy. Their long term fading does not exceed 3.7% and 9% respectively. We additionally investigated effects of sensitivity loss and emission spectra for both types of the foils. One shortcoming of TL foils is that every heat process may have negative influence on their properties, causing changes of their sensitivity. Register signal of the foils after 15 readouts may be reduced by 16% of the initial. We consider that the main reason of these changes is oxidation of organic contamination on the surface and degradation of a polymer which is one of the components of the foils. Effect of sensitivity decreasing may be slowed down by proper use and cleaning detectors by solvent.

  18. Dosimetric characterization of a {sup 131}Cs brachytherapy source by thermoluminescence dosimetry in liquid water

    SciTech Connect

    Tailor, Ramesh; Ibbott, Geoffrey; Lampe, Stephanie; Bivens Warren, Whitney; Tolani, Naresh

    2008-12-15

    Dosimetry measurements of a {sup 131}Cs brachytherapy source have been performed in liquid water employing thermoluminescence dosimeters. A search of the literature reveals that this is the first time a complete set of dosimetric parameters for a brachytherapy ''seed'' source has been measured in liquid water. This method avoids the medium correction uncertainties introduced by the use of water-equivalent plastic phantoms. To assure confidence in the results, four different sources were employed for each parameter measured, and measurements were performed multiple times. The measured dosimetric parameters presented here are based on the AAPM Task Group 43 formalism. The dose-rate constant measured in liquid water was (1.063{+-}0.023) cGy h{sup -1} U{sup -1} and was based on the air-kerma strength standard for this source established by the National Institute of Standards and Technology. Measured values for the 2D anisotropy function and the radial dose function are presented.

  19. Dosimetric properties of high energy current (HEC) detector in keV x-ray beams

    NASA Astrophysics Data System (ADS)

    Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

    2015-04-01

    We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications.

  20. Parametric mapping

    NASA Astrophysics Data System (ADS)

    Branch, Allan C.

    1998-01-01

    Parametric mapping (PM) lies midway between older and proven artificial landmark based guidance systems and yet to be realized vision based guidance systems. It is a simple yet effective natural landmark recognition system offering freedom from the need for enhancements to the environment. Development of PM systems can be inexpensive and rapid and they are starting to appear in commercial and industrial applications. Together with a description of the structural framework developed to generically describe robot mobility, this paper illustrates clearly the parts of any mobile robot navigation and guidance system and their interrelationships. Among other things, the importance of the richness of the reference map, and not necessarily the sensor map, is introduced, the benefits of dynamic path planners to alleviate the need for separate object avoidance, and the independence of the PM system to the type of sensor input is shown.

  1. A dosimetric study on the Ir-192 high dose rate flexisource.

    PubMed

    Granero, D; Pérez-Calatayud, J; Casal, E; Ballester, F; Venselaar, J

    2006-12-01

    In this work, the dose rate distribution of a new Ir-192 high dose rate source (Flexisource used in the afterloading Flexitron system, Isodose Control, Veenendaal, The Netherlands) is studied by means of Monte Carlo techniques using the GEANT4 code. The dosimetric parameters of the Task Group No. 43 Report (TG43) formalism and two-dimensional rectangular look-up tables have been obtained. PMID:17278809

  2. A dosimetric study on the Ir-192 high dose rate Flexisource

    SciTech Connect

    Granero, D.; Perez-Calatayud, J.; Casal, E.; Ballester, F.; Venselaar, J.

    2006-12-15

    In this work, the dose rate distribution of a new Ir-192 high dose rate source (Flexisource used in the afterloading Flexitron system, Isodose Control, Veenendaal, The Netherlands) is studied by means of Monte Carlo techniques using the GEANT4 code. The dosimetric parameters of the Task Group No. 43 Report (TG43) formalism and two-dimensional rectangular look-up tables have been obtained.

  3. X-Ray Attenuation and Absorption for Materials of Dosimetric Interest

    National Institute of Standards and Technology Data Gateway

    SRD 126 X-Ray Attenuation and Absorption for Materials of Dosimetric Interest (Web, free access)   Tables and graphs of the photon mass attenuation coefficient and the mass energy-absorption coefficient are presented for all of the elements Z = 1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x-ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV.

  4. Investigating the dosimetric and tumor control consequences of prostate seed loss and migration

    SciTech Connect

    Knaup, Courtney; Mavroidis, Panayiotis; Esquivel, Carlos; Stathakis, Sotirios; Swanson, Gregory; Baltas, Dimos; Papanikolaou, Nikos

    2012-06-15

    Purpose: Low dose-rate brachytherapy is commonly used to treat prostate cancer. However, once implanted, the seeds are vulnerable to loss and movement. The goal of this work is to investigate the dosimetric and radiobiological effects of the types of seed loss and migration commonly seen in prostate brachytherapy. Methods: Five patients were used in this study. For each patient three treatment plans were created using Iodine-125, Palladium-103, and Cesium-131 seeds. The three seeds that were closest to the urethra were identified and modeled as the seeds lost through the urethra. The three seeds closest to the exterior of prostatic capsule were identified and modeled as those lost from the prostate periphery. The seed locations and organ contours were exported from Prowess and used by in-house software to perform the dosimetric and radiobiological evaluation. Seed loss was simulated by simultaneously removing 1, 2, or 3 seeds near the urethra 0, 2, or 4 days after the implant or removing seeds near the exterior of the prostate 14, 21, or 28 days after the implant. Results: Loss of one, two or three seeds through the urethra results in a D{sub 90} reduction of 2%, 5%, and 7% loss, respectively. Due to delayed loss of peripheral seeds, the dosimetric effects are less severe than for loss through the urethra. However, while the dose reduction is modest for multiple lost seeds, the reduction in tumor control probability was minimal. Conclusions: The goal of this work was to investigate the dosimetric and radiobiological effects of the types of seed loss and migration commonly seen in prostate brachytherapy. The results presented show that loss of multiple seeds can cause a substantial reduction of D{sub 90} coverage. However, for the patients in this study the dose reduction was not seen to reduce tumor control probability.

  5. Respiratory Organ Motion and Dosimetric Impact on Breast and Nodal Irradiation

    SciTech Connect

    Qi, X. Sharon; White, Julia; Rabinovitch, Rachel; Merrell, Kenneth; Sood, Amit; Bauer, Anderson; Wilson, J. Frank; Miften, Moyed; Li, X. Allen

    2010-10-01

    Purpose: To examine the respiratory motion for target and normal structures during whole breast and nodal irradiation and the resulting dosimetric impact. Methods and Materials: Four-dimensional CT data sets of 18 patients with early-stage breast cancer were analyzed retrospectively. A three-dimensional conformal dosimetric plan designed to irradiate the breast was generated on the basis of CT images at 20% respiratory phase (reference phase). The reference plans were copied to other respiratory phases at 0% (end of inspiration) and 50% (end of expiration) to simulate the effects of breathing motion on whole breast irradiation. Dose-volume histograms, equivalent uniform dose, and normal tissue complication probability were evaluated and compared. Results: Organ motion of up to 8.8 mm was observed during free breathing. A large lung centroid movement was typically associated with a large shift of other organs. The variation of planning target volume coverage during a free breathing cycle is generally within 1%-5% (17 of 18 patients) compared with the reference plan. However, up to 28% of V{sub 45} variation for the internal mammary nodes was observed. Interphase mean dose variations of 2.2%, 1.2%, and 1.4% were observed for planning target volume, ipsilateral lung, and heart, respectively. Dose variations for the axillary nodes and brachial plexus were minimal. Conclusions: The doses delivered to the target and normal structures are different from the planned dose based on the reference phase. During normal breathing, the dosimetric impact of respiratory motion is clinically insignificant with the exception of internal mammary nodes. However, noticeable degradation in dosimetric plan quality may be expected for the patients with large respiratory motion.

  6. [In-phantom dosimetric measurements as quality control for brachytherapy: System check and constancy check].

    PubMed

    Kollefrath, Michael; Bruggmoser, Gregor; Nanko, Norbert; Gainey, Mark

    2015-06-01

    In brachytherapy dosimetric measurements are difficult due to the inherent dose-inhomogenieties. Typically in routine clincal practice only the nominal dose rate is determined for computer controlled afterloading systems. The region of interest lies close to the source when measuring the spatial dose distribution. In this region small errors in the postioning of the detector, and its finite size, lead to large measurement uncertainties that exacerbate the routine dosimetric control of the system in the clinic. The size of the measurement chamber, its energy dependence, and the directional dependence of the measurement apparatus are the factors which have a significant influence on dosimetry. Although ionisation chambers are relatively large, they are employed since similar chambers are commonly found on clincal brachytherapy units. The dose is determined using DIN 6800 [11] since DIN 6809-2 [12], which deals with dosimetry in brachytherapy, is antiquated and is currently in the process of revision. Further information regarding dosimetry for brachytherapy can be found in textbooks [1] and [2]. The measurements for this work were performed with a HDR (High-Dose-Rate) (192)Ir source, type mHDR V2, and a Microselectron Afterloader V2 both from Nucletron/Elekta. In this work two dosimetric procedures are presented which, despite the aforemention difficulties, should assist in performing checks of the proper operation of the system. The first is a system check that measures the dose distribution along a line and is to be performed when first bringing the afterloader into operation, or after significant changes to the system. The other is a dosimetric constancy check, which with little effort can be performed monhtly or weekly. It simultaneously verifies the positioning of the source at two positions, the functionality of the system clock and the automatic re-calculation of the source activity. PMID:25791738

  7. Dosimetric monitoring in Ukraine--present status and path to the future.

    PubMed

    Chumak, V; Boguslavskaya, A

    2007-01-01

    Despite wide use of nuclear energy and radiation sources in industry and medicine, there is no centralised dose accounting system in Ukraine; existing dosimetry services operate obsolete manual thermoluminescence dosemeter (TLD) readers and do not meet modern proficiency standards. Currently, dosimetric monitoring is required for approximately 42,000 occupationally exposed workers, including 9100 in medicine, 17,000 employees of nuclear power plants and approximately 16,000 workers dealing with other sources of occupational exposure. This article presents the plan of elaboration of the United System for monitoring and registration of individual doses which has the aim of harmonisation of individual monitoring in Ukraine through securing methodical unity; scientific and methodological guidance of individual dosimetric control; procurement of common technical policy regarding nomenclature and operation of instrumentation; implementation of quality assurance programmes; development and support of information infrastructure, in particular operation of the national registry of individual doses; training and certification of personnel engaged in the system of individual dosimetric monitoring. PMID:16987910

  8. Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array.

    PubMed

    Yoganathan, S A; Das, K J Maria; Raj, D Gowtham; Kumar, Shaleen

    2015-01-01

    The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams. PMID:26170552

  9. Medical linear accelerator mounted mini-beam collimator: design, fabrication and dosimetric characterization.

    PubMed

    Cranmer-Sargison, G; Crewson, C; Davis, W M; Sidhu, N P; Kundapur, V

    2015-09-01

    The goal of this work was to design, build and experimentally characterize a linear accelerator mounted mini-beam collimator for use at a nominal 6 MV beam energy. Monte Carlo simulation was used in the design and dosimetric characterization of a compact mini-beam collimator assembly mounted to a medical linear accelerator. After fabrication, experimental mini-beam dose profiles and central axis relative output were measured and the results used to validate the simulation data. The simulation data was then used to establish traceability back to an established dosimetric code of practice. The Monte Carlo simulation work revealed that changes in collimator blade width have a greater influence on the valley-to-peak dose ratio than do changes in blade height. There was good agreement between the modeled and measured profile data, with the exception of small differences on either side of the central peak dose. These differences were found to be systematic across all depths and result from limitations associated with the collimator fabrication. Experimental mini-beam relative output and simulation data agreed to better than ± 2.0%, which is well within the level of uncertainty required for dosimetric traceability of non-standard field geometries. A mini-beam collimator has now been designed, built and experimentally characterized for use with a commercial linear accelerator operated at a nominal 6 MV beam energy. PMID:26305166

  10. Dosimetric characterization of a bi-directional micromultileaf collimator for stereotactic applications.

    PubMed

    Bucciolini, M; Russo, S; Banci Buonamici, F; Pini, S; Silli, P

    2002-07-01

    A 6 MV photon beam from Linac SL75-5 has been collimated with a new micromultileaf device that is able to shape the field in the two orthogonal directions with four banks of leaves. This is the first clinical installation of the collimator and in this paper the dosimetric characterization of the system is reported. The dosimetric parameters required by the treatment planning system used for the dose calculation in the patient are: tissue maximum ratios, output factors, transmission and leakage of the leaves, penumbra values. Ionization chambers, silicon diode, radiographic films, and LiF thermoluminescent dosimeters have been employed for measurements of absolute dose and beam dosimetric data. Measurements with different dosimeters supply results in reasonable agreement among them and consistent with data available in literature for other models of micromultileaf collimator; that permits the use of the measured parameters for clinical applications. The discrepancies between results obtained with the different detectors (around 2%) for the analyzed parameters can be considered an indication of the accuracy that can be reached by current stereotactic dosimetry. PMID:12148726

  11. Patient-specific dosimetric endpoints based treatment plan quality control in radiotherapy

    NASA Astrophysics Data System (ADS)

    Song, Ting; Staub, David; Chen, Mingli; Lu, Weiguo; Tian, Zhen; Jia, Xun; Li, Yongbao; Zhou, Linghong; Jiang, Steve B.; Gu, Xuejun

    2015-11-01

    In intensity modulated radiotherapy (IMRT), the optimal plan for each patient is specific due to unique patient anatomy. To achieve such a plan, patient-specific dosimetric goals reflecting each patient’s unique anatomy should be defined and adopted in the treatment planning procedure for plan quality control. This study is to develop such a personalized treatment plan quality control tool by predicting patient-specific dosimetric endpoints (DEs). The incorporation of patient specific DEs is realized by a multi-OAR geometry-dosimetry model, capable of predicting optimal DEs based on the individual patient’s geometry. The overall quality of a treatment plan is then judged with a numerical treatment plan quality indicator and characterized as optimal or suboptimal. Taking advantage of clinically available prostate volumetric modulated arc therapy (VMAT) treatment plans, we built and evaluated our proposed plan quality control tool. Using our developed tool, six of twenty evaluated plans were identified as sub-optimal plans. After plan re-optimization, these suboptimal plans achieved better OAR dose sparing without sacrificing the PTV coverage, and the dosimetric endpoints of the re-optimized plans agreed well with the model predicted values, which validate the predictability of the proposed tool. In conclusion, the developed tool is able to accurately predict optimally achievable DEs of multiple OARs, identify suboptimal plans, and guide plan optimization. It is a useful tool for achieving patient-specific treatment plan quality control.

  12. Monte Carlo dosimetric study of the medium dose rate CSM40 source.

    PubMed

    Vijande, J; Granero, D; Perez-Calatayud, J; Ballester, F

    2013-12-01

    The (137)Cs medium dose rate (MDR) CSM40 source model (Eckert & Ziegler BEBIG, Germany) is in clinical use but no dosimetric dataset has been published. This study aims to obtain dosimetric data for the CSM40 source for its use in clinical practice as required by the American Association of Physicists in Medicine (AAPM) and the European Society for Radiotherapy and Oncology (ESTRO). Penelope2008 and Geant4 Monte Carlo codes were used to characterize this source dosimetrically. It was located in an unbounded water phantom with composition and mass density as recommended by AAPM and ESTRO. Due to the low photon energies of (137)Cs, absorbed dose was approximated by collisional kerma. Additional simulations were performed to obtain the air-kerma strength, sK. Mass-energy absorption coefficients in water and air were consistently derived and used to calculate collisional kerma. Results performed with both radiation transport codes showed agreement typically within 0.05%. Dose rate constant, radial dose function and anisotropy function are provided for the CSM40 and compared with published data for other commercially available (137)Cs sources. An uncertainty analysis has been performed. The data provided by this study can be used as input data and verification in the treatment planning systems. PMID:24121444

  13. Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources

    PubMed Central

    Ghorbani, Mahdi; Davenport, David

    2016-01-01

    Abstract Aim The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Background Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. Materials and methods MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Results Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Conclusions Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems. PMID:27247558

  14. Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array

    PubMed Central

    Yoganathan, S. A.; Das, K. J. Maria; Raj, D. Gowtham; Kumar, Shaleen

    2015-01-01

    The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams. PMID:26170552

  15. Memphis Maps.

    ERIC Educational Resources Information Center

    Hyland, Stanley; Cox, David; Martin, Cindy

    1998-01-01

    The Memphis Maps program, a collaborative effort of Memphis (Tennessee) educational institutions, public agencies, a bank, and community programs, trains local students in Geographic Information Systems technology and provides the community with valuable demographic and assessment information. The program is described, and factors contributing to…

  16. Dosimetric Consequences of Interobserver Variability in Delineating the Organs at Risk in Gynecologic Interstitial Brachytherapy

    SciTech Connect

    Damato, Antonio L.; Bair, Ryan J.; Cormack, Robert A.; Kovacs, Arpad; Lee, Larissa J.; Lewis, John H.; Viswanathan, Akila N.

    2014-07-01

    Purpose: To investigate the dosimetric variability associated with interobserver organ-at-risk delineation differences on computed tomography in patients undergoing gynecologic interstitial brachytherapy. Methods and Materials: The rectum, bladder, and sigmoid of 14 patients treated with gynecologic interstitial brachytherapy were retrospectively contoured by 13 physicians. Geometric variability was calculated using κ statistics, conformity index (CI{sub gen}), and coefficient of variation (CV) of volumes contoured across physicians. Dosimetric variability of the single-fraction D{sub 0.1cc} and D{sub 2cc} was assessed through CV across physicians, and the standard deviation of the total EQD2 (equivalent dose in 2 Gy per fraction) brachytherapy dose (SD{sup TOT}) was calculated. Results: The population mean ± 1 standard deviation of κ, CI{sub gen}, and volume CV were, respectively: 0.77 ± 0.06, 0.70 ± 0.08, and 20% ± 6% for bladder; 0.74 ± 06, 0.67 ± 0.08, and 20% ± 5% for rectum; and 0.33 ± 0.20, 0.26 ± 0.17, and 82% ± 42% for sigmoid. Dosimetric variability was as follows: for bladder, CV = 31% ± 19% (SD{sup TOT} = 72 ± 64 Gy) for D{sub 0.1cc} and CV = 16% ± 10% (SD{sup TOT} = 9 ± 6 Gy) for D{sub 2cc}; for rectum, CV = 11% ± 5% (SD{sup TOT} = 16 ± 17 Gy) for D{sub 0.1cc} and CV = 7% ± 2% (SD{sup TOT} = 4 ± 3 Gy) for D{sub 2cc}; for sigmoid, CV = 39% ± 28% (SD{sup TOT} = 12 ± 18 Gy) for D{sub 0.1cc} and CV = 34% ± 19% (SD{sup TOT} = 4 ± 4 Gy) for D{sub 2cc.} Conclusions: Delineation of bladder and rectum by 13 physicians demonstrated substantial geometric agreement and resulted in good dosimetric agreement for all dose-volume histogram parameters except bladder D{sub 0.1cc.} Small delineation differences in high-dose regions by the posterior bladder wall may explain these results. The delineation of sigmoid showed fair geometric agreement. The higher dosimetric variability for sigmoid compared with rectum and bladder did not correlate with

  17. Dosimetric Comparison of Helical Tomotherapy and Dynamic Conformal Arc Therapy in Stereotactic Radiosurgery for Vestibular Schwannomas

    SciTech Connect

    Lee, Tsair-Fwu; Chao, Pei-Ju; Wang, Chang-Yu; Lan, Jen-Hong; Huang, Yu-Je; Hsu, Hsuan-Chih; Sung, Chieh-Cheng; Su, Te-Jen; Lian, Shi-Long; Fang, Fu-Min

    2011-04-01

    The dosimetric results of stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) performed using dynamic conformal arc therapy (DCAT) with the Novalis system and helical TomoTherapy (HT) were compared using plan quality indices. The HT plans were created for 10 consecutive patients with VS previously treated with SRS using the Novalis system. The dosimetric indices used to compare the techniques included the conformity index (CI) and homogeneity index (HI) for the planned target volume (PTV), the comprehensive quality index (CQI) for nine organs at risk (OARs), gradient score index (GSI) for the dose drop-off outside the PTV, and plan quality index (PQI), which was verified using the plan quality discerning power (PQDP) to incorporate 3 plan indices, to evaluate the rival plans. The PTV ranged from 0.27-19.99 cm{sup 3} (median 3.39 cm{sup 3}), with minimum required PTV prescribed doses of 10-16 Gy (median 12 Gy). Both systems satisfied the minimum required PTV prescription doses. HT conformed better to the PTV (CI: 1.51 {+-} 0.23 vs. 1.94 {+-} 0.34; p < 0.01), but had a worse drop-off outside the PTV (GSI: 40.3 {+-} 10.9 vs. 64.9 {+-} 13.6; p < 0.01) compared with DCAT. No significant difference in PTV homogeneity was observed (HI: 1.08 {+-} 0.03 vs. 1.09 {+-} 0.02; p = 0.20). HT had a significantly lower maximum dose in 4 OARs and significant lower mean dose in 1 OAR; by contrast, DCAT had a significantly lower maximum dose in 1 OAR and significant lower mean dose in 2 OARs, with the CQI of the 9 OARs = 0.92 {+-} 0.45. Plan analysis using PQI (HT 0.37 {+-} 0.12 vs. DCAT 0.65 {+-} 0.08; p < 0.01), and verified using the PQDP, confirmed the dosimetric advantage of HT. However, the HT system had a longer beam-on time (33.2 {+-} 7.4 vs. 4.6 {+-} 0.9 min; p < 0.01) and consumed more monitor units (16772 {+-} 3803 vs. 1776 {+-} 356.3; p < 0.01). HT had a better dose conformity and similar dose homogeneity but worse dose gradient than DCAT. Plan analysis

  18. Dosimetric comparison of helical tomotherapy and dynamic conformal arc therapy in stereotactic radiosurgery for vestibular schwannomas.

    PubMed

    Lee, Tsair-Fwu; Chao, Pei-Ju; Wang, Chang-Yu; Lan, Jen-Hong; Huang, Yu-Je; Hsu, Hsuan-Chih; Sung, Chieh-Cheng; Su, Te-Jen; Lian, Shi-Long; Fang, Fu-Min

    2011-01-01

    The dosimetric results of stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) performed using dynamic conformal arc therapy (DCAT) with the Novalis system and helical TomoTherapy (HT) were compared using plan quality indices. The HT plans were created for 10 consecutive patients with VS previously treated with SRS using the Novalis system. The dosimetric indices used to compare the techniques included the conformity index (CI) and homogeneity index (HI) for the planned target volume (PTV), the comprehensive quality index (CQI) for nine organs at risk (OARs), gradient score index (GSI) for the dose drop-off outside the PTV, and plan quality index (PQI), which was verified using the plan quality discerning power (PQDP) to incorporate 3 plan indices, to evaluate the rival plans. The PTV ranged from 0.27-19.99 cm(3) (median 3.39 cm(3)), with minimum required PTV prescribed doses of 10-16 Gy (median 12 Gy). Both systems satisfied the minimum required PTV prescription doses. HT conformed better to the PTV (CI: 1.51 ± 0.23 vs. 1.94 ± 0.34; p < 0.01), but had a worse drop-off outside the PTV (GSI: 40.3 ± 10.9 vs. 64.9 ± 13.6; p < 0.01) compared with DCAT. No significant difference in PTV homogeneity was observed (HI: 1.08 ± 0.03 vs. 1.09 ± 0.02; p = 0.20). HT had a significantly lower maximum dose in 4 OARs and significant lower mean dose in 1 OAR; by contrast, DCAT had a significantly lower maximum dose in 1 OAR and significant lower mean dose in 2 OARs, with the CQI of the 9 OARs = 0.92 ± 0.45. Plan analysis using PQI (HT 0.37 ± 0.12 vs. DCAT 0.65 ± 0.08; p < 0.01), and verified using the PQDP, confirmed the dosimetric advantage of HT. However, the HT system had a longer beam-on time (33.2 ± 7.4 vs. 4.6 ± 0.9 min; p < 0.01) and consumed more monitor units (16772 ± 3803 vs. 1776 ± 356.3; p < 0.01). HT had a better dose conformity and similar dose homogeneity but worse dose gradient than DCAT. Plan analysis confirmed the dosimetric advantage of HT

  19. TU-D-9A-01: TG176: Dosimetric Effects of Couch Tops and Immobilization Devices

    SciTech Connect

    Olch, A

    2014-06-15

    The dosimetric impact from devices external to the patient is a complex combination of increased skin dose, reduced tumor dose, and altered dose distribution. Although small monitor unit or dose corrections are routinely made for blocking trays, ion chamber correction factors, or tissue inhomogeneities, the dose perturbation of the treatment couch top or immobilization devices are often overlooked. These devices also increase surface dose, an effect which is also often ignored or underestimated. These concerns have grown recently due to the increased use of monolithic carbon fiber couch tops which are optimal for imaging for patient position verification but cause attenuation and increased surface dose compared to the ‘tennis racket’ style couch top they often replace. Also, arc delivery techniques have replaced stationary gantry techniques which cause a greater fraction of the dose to be delivered from posterior angles. A host of immobilization devices are available and used to increase patient positioning reproducibility, and these also have attenuation and skin dose implications which are often ignored. This report of Task Group 176 serves to present a survey of published data that illustrates the magnitude of the dosimetric effects of a wide range of devices external to the patient. The report also provides methods for modeling couch tops in treatment planning systems so the physicist can accurately compute the dosimetric effects for indexed patient treatments. Both photon and proton beams are considered. A discussion on avoidance of high density structures during beam planning is also provided. An important aspect of this report are the recommendations we make to clinical physicists, treatment planning system vendors, and device vendors on how to make measurements of skin dose and attenuation, how to report these values, and for the vendors, an appeal is made to work together to provide accurate couch top models in planning systems. Learning Objectives

  20. Correlation between gamma index passing rate and clinical dosimetric difference for pre-treatment 2D and 3D volumetric modulated arc therapy dosimetric verification

    PubMed Central

    Jin, X; Yan, H; Han, C; Zhou, Y; Yi, J

    2015-01-01

    Objective: To investigate comparatively the percentage gamma passing rate (%GP) of two-dimensional (2D) and three-dimensional (3D) pre-treatment volumetric modulated arc therapy (VMAT) dosimetric verification and their correlation and sensitivity with percentage dosimetric errors (%DE). Methods: %GP of 2D and 3D pre-treatment VMAT quality assurance (QA) with different acceptance criteria was obtained by ArcCHECK® (Sun Nuclear Corporation, Melbourne, FL) for 20 patients with nasopharyngeal cancer (NPC) and 20 patients with oesophageal cancer. %DE were calculated from planned dose–volume histogram (DVH) and patients' predicted DVH calculated by 3DVH® software (Sun Nuclear Corporation). Correlation and sensitivity between %GP and %DE were investigated using Pearson's correlation coefficient (r) and receiver operating characteristics (ROCs). Results: Relatively higher %DE on some DVH-based metrics were observed for both patients with NPC and oesophageal cancer. Except for 2%/2 mm criterion, the average %GPs for all patients undergoing VMAT were acceptable with average rates of 97.11% ± 1.54% and 97.39% ± 1.37% for 2D and 3D 3%/3 mm criteria, respectively. The number of correlations for 3D was higher than that for 2D (21 vs 8). However, the general correlation was still poor for all the analysed metrics (9 out of 26 for 3D 3%/3 mm criterion). The average area under the curve (AUC) of ROCs was 0.66 ± 0.12 and 0.71 ± 0.21 for 2D and 3D evaluations, respectively. Conclusions: There is a lack of correlation between %GP and %DE for both 2D and 3D pre-treatment VMAT dosimetric evaluation. DVH-based dose metrics evaluation obtained from 3DVH will provide more useful analysis. Advances in knowledge: Correlation and sensitivity of %GP with %DE for VMAT QA were studied for the first time. PMID:25494412

  1. Dosimetric comparison between two MLC systems commonly used for stereotactic radiosurgery and radiotherapy: a Monte Carlo and experimental study.

    PubMed

    Asnaashari, K; Chow, James C L; Heydarian, Mostafa

    2013-06-01

    In this work dosimetric parameters of two multi-leaf collimator (MLC) systems, namely the beam modulator (BM), which is the MLC commercial name for Elekta "Synergy S" linear accelerator and Radionics micro-MLC (MMLC), are compared using measurements and Monte Carlo simulations. Dosimetric parameters, such as percentage depth doses (PDDs), in-plane and cross-plane dose profiles, and penumbras for different depths and field sizes of the 6 MV photon beams were measured using ionization chamber and a water tank. The collimator leakages were measured using radiographic films. MMLC and BM were modeled using the EGSnrc-based BEAMnrc Monte Carlo code and above dosimetric parameters were calculated. The energy fluence spectra for the two MLCs were also determined using the BEAMnrc and BEAMDP. Dosimetric parameters of the two MLCs were similar, except for penumbras. Leaf-side and leaf-end 80-20% dose penumbras at 10 cm depth for a 10×10 cm(2) field size were 4.8 and 5.1mm for MMLC and 5.3 mm and 6.3 mm for BM, respectively. Both Radionics MMLC and Elekta BM can be used effectively based on their dosimetric characteristics for stereotactic radiosurgery and radiotherapy, although the former showed slightly sharper dose penumbra especially in the leaf-end direction. PMID:22658764

  2. SU-E-J-119: Head-And-Neck Digital Phantoms for Geometric and Dosimetric Uncertainty Evaluation of CT-CBCT Deformable Image Registration

    SciTech Connect

    Shen, Z; Koyfman, S; Xia, P; Bzdusek, K

    2015-06-15

    Purpose: To evaluate geometric and dosimetric uncertainties of CT-CBCT deformable image registration (DIR) algorithms using digital phantoms generated from real patients. Methods: We selected ten H&N cancer patients with adaptive IMRT. For each patient, a planning CT (CT1), a replanning CT (CT2), and a pretreatment CBCT (CBCT1) were used as the basis for digital phantom creation. Manually adjusted meshes were created for selected ROIs (e.g. PTVs, brainstem, spinal cord, mandible, and parotids) on CT1 and CT2. The mesh vertices were input into a thin-plate spline algorithm to generate a reference displacement vector field (DVF). The reference DVF was applied to CBCT1 to create a simulated mid-treatment CBCT (CBCT2). The CT-CBCT digital phantom consisted of CT1 and CBCT2, which were linked by the reference DVF. Three DIR algorithms (Demons, B-Spline, and intensity-based) were applied to these ten digital phantoms. The images, ROIs, and volumetric doses were mapped from CT1 to CBCT2 using the DVFs computed by these three DIRs and compared to those mapped using the reference DVF. Results: The average Dice coefficients for selected ROIs were from 0.83 to 0.94 for Demons, from 0.82 to 0.95 for B-Spline, and from 0.67 to 0.89 for intensity-based DIR. The average Hausdorff distances for selected ROIs were from 2.4 to 6.2 mm for Demons, from 1.8 to 5.9 mm for B-Spline, and from 2.8 to 11.2 mm for intensity-based DIR. The average absolute dose errors for selected ROIs were from 0.7 to 2.1 Gy for Demons, from 0.7 to 2.9 Gy for B- Spline, and from 1.3 to 4.5 Gy for intensity-based DIR. Conclusion: Using clinically realistic CT-CBCT digital phantoms, Demons and B-Spline were shown to have similar geometric and dosimetric uncertainties while intensity-based DIR had the worst uncertainties. CT-CBCT DIR has the potential to provide accurate CBCT-based dose verification for H&N adaptive radiotherapy. Z Shen: None; K Bzdusek: an employee of Philips Healthcare; S Koyfman: None; P Xia

  3. SU-E-J-94: Geometric and Dosimetric Evaluation of Deformation Image Registration Algorithms Using Virtual Phantoms Generated From Patients with Lung Cancer

    SciTech Connect

    Shen, Z; Greskovich, J; Xia, P; Bzdusek, K

    2015-06-15

    Purpose: To generate virtual phantoms with clinically relevant deformation and use them to objectively evaluate geometric and dosimetric uncertainties of deformable image registration (DIR) algorithms. Methods: Ten lung cancer patients undergoing adaptive 3DCRT planning were selected. For each patient, a pair of planning CT (pCT) and replanning CT (rCT) were used as the basis for virtual phantom generation. Manually adjusted meshes were created for selected ROIs (e.g. PTV, lungs, spinal cord, esophagus, and heart) on pCT and rCT. The mesh vertices were input into a thin-plate spline algorithm to generate a reference displacement vector field (DVF). The reference DVF was used to deform pCT to generate a simulated replanning CT (srCT) that was closely matched to rCT. Three DIR algorithms (Demons, B-Spline, and intensity-based) were applied to these ten virtual phantoms. The images, ROIs, and doses were mapped from pCT to srCT using the DVFs computed by these three DIRs and compared to those mapped using the reference DVF. Results: The average Dice coefficients for selected ROIs were from 0.85 to 0.96 for Demons, from 0.86 to 0.97 for intensity-based, and from 0.76 to 0.95 for B-Spline. The average Hausdorff distances for selected ROIs were from 2.2 to 5.4 mm for Demons, from 2.3 to 6.8 mm for intensity-based, and from 2.4 to 11.4 mm for B-Spline. The average absolute dose errors for selected ROIs were from 0.2 to 0.6 Gy for Demons, from 0.1 to 0.5 Gy for intensity-based, and from 0.5 to 1.5 Gy for B-Spline. Conclusion: Virtual phantoms were modeled after patients with lung cancer and were clinically relevant for adaptive radiotherapy treatment replanning. Virtual phantoms with known DVFs serve as references and can provide a fair comparison when evaluating different DIRs. Demons and intensity-based DIRs were shown to have smaller geometric and dosimetric uncertainties than B-Spline. Z Shen: None; K Bzdusek: an employee of Philips Healthcare; J Greskovich: None; P Xia

  4. Initial dosimetric experience with mega voltage computed tomography detectors and estimation of pre and post-repair dosimetric parameters of a first Helical Hi-Art II tomotherapy machine in India.

    PubMed

    Kinhikar, Rajesh A; Master, Zubin; Dhote, Dipak S; Deshpande, Deepak D

    2009-04-01

    A Helical Tomotherapy (HT) Hi-Art II (TomoTherapy, Inc., Madison, WI, USA) has been one of the important innovations to help deliver IMRT with image guidance. On-board, mega voltage computed tomography (MVCT) detectors are used for imaging and dosimetric purpose. The two objectives of this study are: (i) To estimate the dosimetric and general capability (TomoImage registration, reconstruction, contrast and spatial resolution, artifacts-free image and dose in TomoImage) of on-board MVCT detectors. (ii) To measure the dosimetric parameters (output and energy) following major repair. The MVCT detectors also estimated the rotational output constancy well. During this study, dosimetric tests were repeated after replacing MVCT detectors and the target. fixed-gantry/fixed-couch measurements were measured daily to investigate; the system stability. Thermoluminescense dosimeter (TLD) was used during both the measurements subsequently. The MVCT image quality with old and new detectors was comparable and hence acceptable clinically. The spatial resolution was optimal and the dose during TomoImage was 2 cGy (well within the manufacturer tolerance of 4 cGy). The results of lateral beam profiles showed an excellent agreement between the two normalized plots. The output from the rotational procedure revealed 99.7% while the energy was consistent over a period of twelve months. The Hi-Art II system has maintained its calibration to within +/- 2% and energy to within +/- 1.5% over the initial twelve-month period. Based on the periodic measurements for rotational output and consistency in the lateral beam profile shape, the on-board detector proved to be a viable dosimetric quality assurance tool for IMRT with Tomotherapy. Tomotherapy was stable from the dosimetric point of view during the twelve-month period. PMID:20098540

  5. Dosimetric comparison of four target alignment methods for prostate cancer radiotherapy

    SciTech Connect

    O'Daniel, Jennifer C.; Dong Lei . E-mail: ldong@mdanderson.org; Zhang Lifei; Crevoisier, Renaud de; Wang He; Lee, Andrew K.; Cheung, Rex; Tucker, Susan L.; Kudchadker, Rajat J.; Bonnen, Mark D.; Cox, James D.; Mohan, Radhe; Kuban, Deborah A.

    2006-11-01

    Purpose: The aim of this study was to compare the dosimetric consequences of 4 treatment delivery techniques for prostate cancer patients treated with intensity-modulated radiotherapy (IMRT). Methods and Materials: During an 8-week course of radiotherapy, 10 patients underwent computed tomography (CT) scans 3 times per week (243 total) before daily treatment with a CT-linear accelerator. Treatment delivery was simulated by realigning a fixed-margin treatment plan on each CT scan and calculating doses. The alignment methods were those based on the following: skin marks, bony registration, ultrasonography (United States), and in-room CT. For the last two methods, prostate was the alignment target. The dosimetric effects of these alignment methods on the prostate, seminal vesicles, rectum, and bladder were compared. The average daily minimum dose to 0.1 cm{sup 3} was used as the metric for target coverage. Results: Skin and bone alignments provided acceptable prostate coverage for only 70% of patients, US alignment for 90%, and CT alignment for 100%. CT-based alignment of the prostate provided seminal vesicle (SV) coverage of {>=}69 Gy for all patients; US and bone alignments provided SV coverage of {>=}60 Gy. This SV coverage may be acceptable for early-stage cancer (equivalent SV dose = 55.8 Gy at 1.8 Gy per fraction), but unacceptable for late-stage cancer (SV dose = 75.6 Gy). At 75.6 Gy, the acceptable rate for SV coverage was 40% for skin and bone alignments, 70% for US, and 80% for CT. Conclusions: Direct target alignment methods (US and CT) provided better target coverage. CT-guided alignment provided the best and most consistent dosimetric coverage. A larger planning target volume margin is needed for SV coverage when the alignment target is the prostate.

  6. Dosimetric optimization of a conical breast brachytherapy applicator for improved skin dose sparing

    SciTech Connect

    Yang Yun; Rivard, Mark J.

    2010-11-15

    Purpose: Both the AccuBoost D-shaped and round applicators have been dosimetrically characterized and clinically used to treat patients with breast cancer. While the round applicators provide conformal dose coverage, under certain clinical circumstances the breast skin dose may be higher than preferred. The purpose of this study was to modify the round applicators to minimize skin dose while not substantially affecting dose uniformity within the target volume and reducing the treatment time. Methods: In order to irradiate the intended volume while sparing critical structures such as the skin, the current round applicator design has been augmented through the addition of an internal truncated cone (i.e., frustum) shield. Monte Carlo methods and clinical constraints were used to design the optimal cone applicator. With the cone applicator now defined as the entire assembly including the surrounding tungsten-alloy shell holding the HDR {sup 192}Ir source catheter, the applicator height was reduced to diminish the treatment time while minimizing skin dose. Monte Carlo simulation results were validated using both radiochromic film and ionization chamber measurements based on established techniques. Results: The optimal cone applicators diminished the maximum skin dose by 15%-32% (based on the applicator diameter and breast separation) with the tumor dose reduced by less than 3% for a constant exposure time. Furthermore, reduction in applicator height diminished the treatment time by up to 30%. Radiochromic film and ionization chamber dosimetric results in phantom agreed with Monte Carlo simulation results typically within 3%. Larger differences were outside the treatment volume in low dose regions or associated with differences between the measurement and Monte Carlo simulation environments. Conclusions: A new radiotherapy treatment device was developed and dosimetrically characterized. This set of applicators significantly reduces the skin dose and treatment time while

  7. Dosimetric Impact of Intrafractional Patient Motion in Pediatric Brain Tumor Patients

    SciTech Connect

    Beltran, Chris Trussell, John; Merchant, Thomas E.

    2010-04-01

    The purpose of this study was to determine the dosimetric consequences of intrafractional patient motion on the clinical target volume (CTV), spinal cord, and optic nerves for non-sedated pediatric brain tumor patients. The patients were immobilized for treatment using a customized thermoplastic full-face mask and bite-block attached to an array of reflectors. The array was optically tracked by infra-red cameras at a frequency of 10 Hz. Patients were localized based on skin/mask marks and weekly films were taken to ensure proper setup. Before each noncoplanar field was delivered, the deviation from baseline of the array was recorded. The systematic error (SE) and random error (RE) were calculated. Direct simulation of the intrafractional motion was used to quantify the dosimetric changes to the targets and critical structures. Nine patients utilizing the optical tracking system were evaluated. The patient cohort had a mean of 31 {+-} 1.5 treatment fractions; motion data were acquired for a mean of 26 {+-} 6.2 fractions. The mean age was 15.6 {+-} 4.1 years. The SE and RE were 0.4 and 1.1 mm in the posterior-anterior, 0.5 and 1.0 mm in left-right, and 0.6 and 1.3 mm in superior-inferior directions, respectively. The dosimetric effects of the motion on the CTV were negligible; however, the dose to the critical structures was increased. Patient motion during treatment does affect the dose to critical structures, therefore, planning risk volumes are needed to properly assess the dose to normal tissues. Because the motion did not affect the dose to the CTV, the 3-mm PTV margin used is sufficient to account for intrafractional motion, given the patient is properly localized at the start of treatment.

  8. SU-E-T-123: Dosimetric Comparison Between Portrait and Landscape Orientations in Radiochromic Film Dosimetry

    SciTech Connect

    Kakinohana, Y; Toita, T; Kasuya, G; Ariga, T; Heianna, J; Murayama, S

    2014-06-01

    Purpose: To compare the dosimetric properties of radiochromic films with different orientation. Methods: A sheet of EBT3 film was cut into eight pieces with the following sizes: 15×15 cm2 (one piece), 5x15 cm{sup 2} (two) and 4×5 cm{sup 2} (five). A set of two EBT3 sheets was used at each dose level. Two sets were used changing the delivered doses (1 and 2 Gy). The 5×15 cm{sup 2} pieces were rotated by 90 degrees in relation to each other, such that one had landscape orientation and the other had portrait orientation. All 5×15 cm2 pieces were irradiated with their long side aligned with the x-axis of the radiation field. The 15×15 cm{sup 2} pieces were irradiated rotated at 90 degrees to each other. Five pieces, (a total of ten from two sheets) were used to obtain a calibration curve. The irradiated films were scanned using an Epson ES-2200 scanner and were analyzed using ImageJ software. In this study, no correction was applied for the nonuniform scanner signal that is evident in the direction of the scanner lamp. Each film piece was scanned both in portrait and landscape orientations. Dosimetric comparisons of the beam profiles were made in terms of the film orientations (portrait and landscape) and scanner bed directions (perpendicular and parallel to the scanner movement). Results: In general, portrait orientation exhibited higher noise than landscape and was adversely affected to a great extent by the nonuniformity in the direction of the scanner lamp. A significant difference in the measured field widths between the perpendicular and parallel directions was found for both orientations. Conclusion: Without correction for the nonuniform scanner signal in the direction of the scanner lamp, a landscape orientation is preferable. A more detailed investigation is planned to evaluate quantitatively the effect of orientation on the dosimetric properties of a film.

  9. Dosimetric characterizations of GZP6 60Co high dose rate brachytherapy sources: application of superimposition method

    PubMed Central

    Bahreyni Toossi, Mohammad Taghi; Ghorbani, Mahdi; Mowlavi, Ali Asghar; Meigooni, Ali Soleimani

    2012-01-01

    Background Dosimetric characteristics of a high dose rate (HDR) GZP6 Co-60 brachytherapy source have been evaluated following American Association of Physicists in MedicineTask Group 43U1 (AAPM TG-43U1) recommendations for their clinical applications. Materials and methods MCNP-4C and MCNPX Monte Carlo codes were utilized to calculate dose rate constant, two dimensional (2D) dose distribution, radial dose function and 2D anisotropy function of the source. These parameters of this source are compared with the available data for Ralstron 60Co and microSelectron192Ir sources. Besides, a superimposition method was developed to extend the obtained results for the GZP6 source No. 3 to other GZP6 sources. Results The simulated value for dose rate constant for GZP6 source was 1.104±0.03 cGyh-1U-1. The graphical and tabulated radial dose function and 2D anisotropy function of this source are presented here. The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source. While dose rate constant for the two 60Co sources are similar to that for the microSelectron192Ir source, there are differences between radial dose function and anisotropy functions. Radial dose function of the 192Ir source is less steep than both 60Co source models. In addition, the 60Co sources are showing more isotropic dose distribution than the 192Ir source. Conclusions The superimposition method is applicable to produce dose distributions for other source arrangements from the dose distribution of a single source. The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS. PMID:23077455

  10. Mechanical and dosimetric quality control for computer controlled radiotherapy treatment equipment.

    PubMed

    Thompson, A V; Lam, K L; Balter, J M; McShan, D L; Martel, M K; Weaver, T A; Fraass, B A; Ten Haken, R K

    1995-05-01

    Modern computer controlled radiotherapy treatment equipment offers the possibility of delivering complex, multiple field treatments with minimal operator intervention, thus making multiple field conformal therapy practical. Conventional quality control programs are inadequate for this new technology, so new quality control procedures are needed. A reasonably fast, sensitive, and complete daily quality control program has been developed in our clinic that includes nearly automated mechanical as well as dosimetric tests. Automated delivery of these quality control fields is performed by the control system of the MM50 racetrack microtron, directed by the CCRS sequence processor [D. L. McShan and B. A. Fraass, Proceedings of the XIth International Conference on the use of computers in Radiation Therapy, 20-24 March 1994, Manchester, U.K. (North Western Medical Physics Department, Manchester, U.K., 1994), pp. 210-211], which controls the treatment process. The mechanical tests involve multiple irradiations of a single film to check the accuracy and reproducibility of the computer controlled setup of gantry and collimator angles, table orientation, collimator jaws, and multileaf collimator shape. The dosimetric tests, which involve multiple irradiations of an array of ionization chambers in a commercial dose detector (Keithly model 90100 Tracker System) rigidly attached to the head of the treatment gantry, check the output and symmetry of the treatment unit as a function of gantry and collimator angle and other parameters. For each of the dosimetric tests, readings from the five ionization chambers are automatically read out, stored, and analyzed by the computer, along with the geometric parameters of the treatment unit for that beam.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7643792

  11. Craniospinal Irradiation Techniques: A Dosimetric Comparison of Proton Beams With Standard and Advanced Photon Radiotherapy

    SciTech Connect

    Yoon, Myonggeun; Shin, Dong Ho; Kim, Jinsung; Kim, Jong Won; Kim, Dae Woong; Park, Sung Yong; Lee, Se Byeong; Kim, Joo Young; Park, Hyeon-Jin; Park, Byung Kiu; Shin, Sang Hoon

    2011-11-01

    Purpose: To evaluate the dosimetric benefits of advanced radiotherapy techniques for craniospinal irradiation in cancer in children. Methods and Materials: Craniospinal irradiation (CSI) using three-dimensional conformal radiotherapy (3D-CRT), tomotherapy (TOMO), and proton beam treatment (PBT) in the scattering mode was planned for each of 10 patients at our institution. Dosimetric benefits and organ-specific radiation-induced cancer risks were based on comparisons of dose-volume histograms (DVHs) and on the application of organ equivalent doses (OEDs), respectively. Results: When we analyzed the organ-at-risk volumes that received 30%, 60%, and 90% of the prescribed dose (PD), we found that PBT was superior to TOMO and 3D-CRT. On average, the doses delivered by PBT to the esophagus, stomach, liver, lung, pancreas, and kidney were 19.4 Gy, 0.6 Gy, 0.3 Gy, 2.5 Gy, 0.2 Gy, and 2.2 Gy for the PD of 36 Gy, respectively, which were significantly lower than the doses delivered by TOMO (22.9 Gy, 4.5 Gy, 6.1 Gy, 4.0 Gy, 13.3 Gy, and 4.9 Gy, respectively) and 3D-CRT (34.6 Gy, 3.6 Gy, 8.0 Gy, 4.6 Gy, 22.9 Gy, and 4.3 Gy, respectively). Although the average doses delivered by PBT to the chest and abdomen were significantly lower than those of 3D-CRT or TOMO, these differences were reduced in the head-and-neck region. OED calculations showed that the risk of secondary cancers in organs such as the stomach, lungs, thyroid, and pancreas was much higher when 3D-CRT or TOMO was used than when PBT was used. Conclusions: Compared with photon techniques, PBT showed improvements in most dosimetric parameters for CSI patients, with lower OEDs to organs at risk.

  12. Dosimetric effects of an air cavity for the SAVI partial breast irradiation applicator

    SciTech Connect

    Richardson, Susan L.; Pino, Ramiro

    2010-08-15

    Purpose: To investigate the dosimetric effect of the air inside the SAVI partial breast irradiation device. Methods: The authors have investigated how the air inside the SAVI partial breast irradiation device changes the delivered dose from the homogeneously calculated dose. Measurements were made with the device filled with air and water to allow comparison to a homogenous dose calculation done by the treatment planning system. Measurements were made with an ion chamber, TLDs, and film. Monte Carlo (MC) simulations of the experiment were done using the EGSnrc suite. The MC model was validated by comparing the water-filled calculations to those from a commercial treatment planning system. Results: The magnitude of the dosimetric effect depends on the size of the cavity, the arrangement of sources, and the relative dwell times. For a simple case using only the central catheter of the largest device, MC results indicate that the dose at the prescription point 1 cm away from the air-water boundary is about 9% higher than the homogeneous calculation. Independent measurements in a water phantom with a similar air cavity gave comparable results. MC simulation of a realistic multidwell position plan showed discrepancies of about 5% on average at the prescription point for the largest device. Conclusions: The dosimetric effect of the air cavity is in the range of 3%-9%. Unless a heterogeneous dose calculation algorithm is used, users should be aware of the possibility of small treatment planning dose errors for this device and make modifications to the treatment delivery, if necessary.

  13. Dosimetric comparison of volumetric modulated arc therapy with robotic stereotactic radiation therapy in hepatocellular carcinoma

    PubMed Central

    Paik, Eun Kyung; Choi, Chul Won; Jang, Won Il; Lee, Sung Hyun; Choi, Sang Hyoun; Kim, Kum Bae; Lee, Dong Han

    2015-01-01

    Purpose To compare volumetric modulated arc therapy of RapidArc with robotic stereotactic body radiation therapy (SBRT) of CyberKnife in the planning and delivery of SBRT for hepatocellular carcinoma (HCC) treatment by analyzing dosimetric parameters. Materials and Methods Two radiation treatment plans were generated for 29 HCC patients, one using Eclipse for the RapidArc plan and the other using Multiplan for the CyberKnife plan. The prescription dose was 60 Gy in 3 fractions. The dosimetric parameters of planning target volume (PTV) coverage and normal tissue sparing in the RapidArc and the CyberKnife plans were analyzed. Results The conformity index was 1.05 ± 0.02 for the CyberKnife plan, and 1.13 ± 0.10 for the RapidArc plan. The homogeneity index was 1.23 ± 0.01 for the CyberKnife plan, and 1.10 ± 0.03 for the RapidArc plan. For the normal liver, there were significant differences between the two plans in the low-dose regions of V1 and V3. The normalized volumes of V60 for the normal liver in the RapidArc plan were drastically increased when the mean dose of the PTVs in RapidArc plan is equivalent to the mean dose of the PTVs in the CyberKnife plan. Conclusion CyberKnife plans show greater dose conformity, especially in small-sized tumors, while RapidArc plans show good dosimetric distribution of low dose sparing in the normal liver and body. PMID:26484307

  14. Evaluation of a Proposed Biodegradable 188Re Source for Brachytherapy Application: A Review of Dosimetric Parameters.

    PubMed

    Khorshidi, Abdollah; Ahmadinejad, Marjan; Hamed Hosseini, S

    2015-07-01

    This study aimed to evaluate dosimetric characteristics based on Monte Carlo (MC) simulations for a proposed beta emitter bioglass 188Re seed for internal radiotherapy applications. The bioactive glass seed has been developed using the sol-gel technique. The simulations were performed for the seed using MC radiation transport code to investigate the dosimetric factors recommended by the AAPM Task Group 60 (TG-60). Dose distributions due to the beta and photon radiation were predicted at different radial distances surrounding the source. The dose rate in water at the reference point was calculated to be 7.43 ± 0.5 cGy/h/μCi. The dosimetric factors consisting of the reference point dose rate, D(r0,θ0), the radial dose function, g(r), the 2-dimensional anisotropy function, F(r,θ), the 1-dimensional anisotropy function, φan(r), and the R90 quantity were estimated and compared with several available beta-emitting sources. The element 188Re incorporated in bioactive glasses produced by the sol-gel technique provides a suitable solution for producing new materials for seed implants applied to brachytherapy applications in prostate and liver cancers treatment. Dose distribution of 188Re seed was greater isotropic than other commercially attainable encapsulated seeds, since it has no end weld to attenuate radiation. The beta radiation-emitting 188Re source provides high doses of local radiation to the tumor tissue and the short range of the beta particles limit damage to the adjacent normal tissue. PMID:26181543

  15. Dosimetric impact of intrafractional patient motion in pediatric brain tumor patients.

    PubMed

    Beltran, Chris; Trussell, John; Merchant, Thomas E

    2010-01-01

    The purpose of this study was to determine the dosimetric consequences of intrafractional patient motion on the clinical target volume (CTV), spinal cord, and optic nerves for non-sedated pediatric brain tumor patients. The patients were immobilized for treatment using a customized thermoplastic full-face mask and bite-block attached to an array of reflectors. The array was optically tracked by infra-red cameras at a frequency of 10 Hz. Patients were localized based on skin/mask marks and weekly films were taken to ensure proper setup. Before each noncoplanar field was delivered, the deviation from baseline of the array was recorded. The systematic error (SE) and random error (RE) were calculated. Direct simulation of the intrafractional motion was used to quantify the dosimetric changes to the targets and critical structures. Nine patients utilizing the optical tracking system were evaluated. The patient cohort had a mean of 31 +/- 1.5 treatment fractions; motion data were acquired for a mean of 26 +/- 6.2 fractions. The mean age was 15.6 +/- 4.1 years. The SE and RE were 0.4 and 1.1 mm in the posterior-anterior, 0.5 and 1.0 mm in left-right, and 0.6 and 1.3 mm in superior-inferior directions, respectively. The dosimetric effects of the motion on the CTV were negligible; however, the dose to the critical structures was increased. Patient motion during treatment does affect the dose to critical structures, therefore, planning risk volumes are needed to properly assess the dose to normal tissues. Because the motion did not affect the dose to the CTV, the 3-mm PTV margin used is sufficient to account for intrafractional motion, given the patient is properly localized at the start of treatment. PMID:19931014

  16. Monte Carlo dosimetric study of best industries and Alpha Omega Ir-192 brachytherapy seeds.

    PubMed

    Ballester, F; Granero, D; Pérez-Calatayud, J; Casal, E; Puchades, V

    2004-12-01

    Ir-192 seeds are widely used in the USA for low dose rate interstitial brachytherapy. There are two commercially available models: those manufactured by Best Industries filtered with stainless steel, and those manufactured by Alpha-Omega seeds filtered with Pt. Newly developed 3D correction algorithms for brachytherapy are based on dosimetry data obtained on unbounded phantom size, allowing corrections for heterogeneities and actual tissue boundaries. Published dosimetric datasets for both seeds have been obtained under bounded conditions. The aim of the present study is to obtain dosimetric datasets for these seeds under full scatter conditions. The Monte Carlo GEANT4 code has been used to estimate air-kerma strength and dose rate in water around the Ir-192 seeds. Functions and parameters following the TG43 formalism are obtained and presented in tabular forms: the dose rate constant, the radial dose function, and the anisotropy function. Tables for the anisotropy factor have been obtained in order to apply punctual approximation. Differences between dose rate distributions for both seeds show that specific dataset must be used for each type of seed in clinical dosimetry. The data in the present study improve on published data in the following aspects: (i) dosimetric data were obtained under full scatter conditions, which affect dose values at distances greater than 4-5 cm from the source; (ii) the dose rate tables are given at greater distances from the source; and (iii) the spatial resolution in high dose gradient areas, such as those near the longitudinal source axis, has been improved. PMID:15651612

  17. Monte Carlo dosimetric study of Best Industries and Alpha Omega Ir-192 brachytherapy seeds

    SciTech Connect

    Ballester, F.; Granero, D.; Perez-Calatayud, J.; Casal, E.; Puchades, V.

    2004-12-01

    Ir-192 seeds are widely used in the USA for low dose rate interstitial brachytherapy. There are two commercially available models: those manufactured by Best Industries filtered with stainless steel, and those manufactured by Alpha-Omega seeds filtered with Pt. Newly developed 3D correction algorithms for brachytherapy are based on dosimetry data obtained on unbounded phantom size, allowing corrections for heterogeneities and actual tissue boundaries. Published dosimetric datasets for both seeds have been obtained under bounded conditions. The aim of the present study is to obtain dosimetric datasets for these seeds under full scatter conditions. The Monte Carlo GEANT4 code has been used to estimate air-kerma strength and dose rate in water around the Ir-192 seeds. Functions and parameters following the TG43 formalism are obtained and presented in tabular forms: the dose rate constant, the radial dose function, and the anisotropy function. Tables for the anisotropy factor have been obtained in order to apply punctual approximation. Differences between dose rate distributions for both seeds show that specific dataset must be used for each type of seed in clinical dosimetry. The data in the present study improve on published data in the following aspects: (i) dosimetric data were obtained under full scatter conditions, which affect dose values at distances greater than 4-5 cm from the source; (ii) the dose rate tables are given at greater distances from the source; and (iii) the spatial resolution in high dose gradient areas, such as those near the longitudinal source axis, has been improved.

  18. Dosimetric and mechanical characteristics of a commercial dynamic {mu}MLC used in SRS

    SciTech Connect

    Galal, Mohamed M.; Keogh, Sinead; Khalil, Sultan

    2011-07-15

    Purpose: The aim of this work is to carry out mechanical and dosimetric assessments on a commercial dynamic micromulti leaf collimator system to be used for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). Mechanical parameters such as leaf position accuracy with different gantry angles and leaf position reproducibility were measured. Also dosimetric measurements of the interleaf leakage, intraleaf transmission, penumbra width, and light field alignment were carried out. Furthermore, measurements of output factors (S{sub cp}) and in-air factors (S{sub c}) for the {mu}MLC system will be reported. Methods: EBT2 films were used to assess the leaf position error with gantry angle and after stress test, penumbra width and light field alignment. Leaf leakage was quantified using both EBT2 film and a pinpoint ion chamber. With regard to output factors, the pinpoint chamber was placed in a water phantom at 10 cm depth and 100 cm SSD. For in-air output factor measurements, 0.2 cm of brass was placed above the photon diode as build-up. Results: Measurements of mechanical parameters gave values of 0.05 cm (SD 0.035) for the average leaf position accuracy for different gantry angles and after stress test. Dosimetric measurements, yielded values of 0.22 {+-} 0.01 and 0.24 {+-} 0.01 cm, respectively, for side and head leaf penumbras. Also, average leaf abutting, leakage and transmission were found to be 0.65, 0.91, and 0.20%, respectively. Conclusions: (a) The add-on {mu}MLC system in combination with our LINAC has been commissioned to be used for clinical purposes and showed good agreement with published results for different {mu}MLC types. (b) This work has lead to the recommendation that leaves should be recalibrated after ten static beams or after each dynamic arc.

  19. Dosimetric Evaluation of Automatic Segmentation for Adaptive IMRT for Head-and-Neck Cancer

    SciTech Connect

    Tsuji, Stuart Y.; Hwang, Andrew; Weinberg, Vivian; Yom, Sue S.; Quivey, Jeanne M.; Xia Ping

    2010-07-01

    Purpose: Adaptive planning to accommodate anatomic changes during treatment requires repeat segmentation. This study uses dosimetric endpoints to assess automatically deformed contours. Methods and Materials: Sixteen patients with head-and-neck cancer had adaptive plans because of anatomic change during radiotherapy. Contours from the initial planning computed tomography (CT) were deformed to the mid-treatment CT using an intensity-based free-form registration algorithm then compared with the manually drawn contours for the same CT using the Dice similarity coefficient and an overlap index. The automatic contours were used to create new adaptive plans. The original and automatic adaptive plans were compared based on dosimetric outcomes of the manual contours and on plan conformality. Results: Volumes from the manual and automatic segmentation were similar; only the gross tumor volume (GTV) was significantly different. Automatic plans achieved lower mean coverage for the GTV: V95: 98.6 {+-} 1.9% vs. 89.9 {+-} 10.1% (p = 0.004) and clinical target volume: V95: 98.4 {+-} 0.8% vs. 89.8 {+-} 6.2% (p < 0.001) and a higher mean maximum dose to 1 cm{sup 3} of the spinal cord 39.9 {+-} 3.7 Gy vs. 42.8 {+-} 5.4 Gy (p = 0.034), but no difference for the remaining structures. Conclusions: Automatic segmentation is not robust enough to substitute for physician-drawn volumes, particularly for the GTV. However, it generates normal structure contours of sufficient accuracy when assessed by dosimetric end points.

  20. Dosimetric effects caused by couch tops and immobilization devices: Report of AAPM Task Group 176

    SciTech Connect

    Olch, Arthur J.; Gerig, Lee; Li, Heng; Mihaylov, Ivaylo; Morgan, Andrew

    2014-06-15

    The dosimetric impact from devices external to the patient is a complex combination of increased skin dose, reduced tumor dose, and altered dose distribution. Although small monitor unit or dose corrections are routinely made for blocking trays, ion chamber correction factors, e.g., accounting for temperature and pressure, or tissue inhomogeneities, the dose perturbation of the treatment couch top or immobilization devices is often overlooked. These devices also increase skin dose, an effect which is also often ignored or underestimated. These concerns have grown recently due to the increased use of monolithic carbon fiber couch tops which are optimal for imaging for patient position verification but cause attenuation and increased skin dose compared to the “tennis racket” style couch top they often replace. Also, arc delivery techniques have replaced stationary gantry techniques which cause a greater fraction of the dose to be delivered from posterior angles. A host of immobilization devices are available and used to increase patient positioning reproducibility, and these also have attenuation and skin dose implications which are often ignored. This report of Task Group 176 serves to present a survey of published data that illustrates the magnitude of the dosimetric effects of a wide range of devices external to the patient. The report also provides methods for modeling couch tops in treatment planning systems so the physicist can accurately compute the dosimetric effects for indexed patient treatments. Both photon and proton beams are considered. A discussion on avoidance of high density structures during beam planning is also provided. An important aspect of this report are the recommendations the authors make to clinical physicists, treatment planning system vendors, and device vendors on how to make measurements of surface dose and attenuation and how to report these values. For the vendors, an appeal is made to work together to provide accurate couch top

  1. The spectral applications of Beer-Lambert law for some biological and dosimetric materials

    NASA Astrophysics Data System (ADS)

    Içelli, Orhan; Yalçin, Zeynel; Karakaya, Vatan; Ilgaz, Işıl P.

    2014-08-01

    The aim of this study is to conduct quantitative and qualitative analysis of biological and dosimetric materials which contain organic and inorganic materials and to make the determination by using the spectral theorem Beer-Lambert law. Beer-Lambert law is a system of linear equations for the spectral theory. It is possible to solve linear equations with a non-zero coefficient matrix determinant forming linear equations. Characteristic matrix of the linear equation with zero determinant is called point spectrum at the spectral theory.

  2. Measurement of dosimetric parameters for the Alpha-Omega high-dose-rate Iridium-192 source

    SciTech Connect

    Muller-Runkel, R. . E-mail: renate.muller@ssfhs.org

    2005-09-30

    Thermoluminescent (TLD) measurements of dose-rate constant, anisotropy function, and radial dose function are reported for the Alpha-Omega high dose rate (HDR) Iridium-192 ({sup 192}Ir) source, which has been available since 1998 for use in the MicroSelectron HDR afterloader manufactured by the Nucletron Corporation. Measurement results are compared with published or available Monte Carlo calculations for both sources. They are found in good agreement, and, within experimental accuracy, no difference is seen in the dosimetric parameters of both sources.

  3. The revised International Commission on Radiological Protection (ICRP) dosimetric model for the human respiratory tract

    SciTech Connect

    Bair, W.J.

    1992-05-01

    A task group has revised the dosimetric model of the respiratory tract used to calculate annual limits on intake of radionuclides. The revised model can be used to project respiratory tract doses for workers and members of the public from airborne radionuclides and to assess past exposures. Doses calculated for specific extrathoracic and thoracic tissues can be adjusted to account for differences in radiosensitivity and summed to yield two values of dose for the respiratory tract that are applicable to the ICRP tissue weighted dosimetry system.

  4. EPR dosimetric properties of 2-methylalanine pellet for radiation processing application

    NASA Astrophysics Data System (ADS)

    Soliman, Y. S.; Ali, Laila I.; Moustafa, H.; Tadros, Soad M.

    2014-09-01

    The dosimetric characteristics of γ-radiation induced free radicals in 2-methylalanine (2MA) pellet dosimeter are investigated using electron paramagnetic resonance (EPR) in the high-dose range of 1-100 kGy. The EPR spectrum of γ-irradiated 2MA exhibits an isotropic EPR signal with seven lines. The dosimeter response is humidity independent in the range of 33-76% relative humidity. The manufactured dosimeter is typically adipose tissue equivalent in the energy level of 0.1-15 MeV. The overall uncertainty (2σ) of the dosimeter is less than 6.9%.

  5. Study of dosimetric water equivalency of PRESAGE® for megavoltage and kilovoltage x-ray beams

    NASA Astrophysics Data System (ADS)

    Gorjiara, Tina; Hill, Robin; Kim, Jung-Ha; Kuncic, Zdenka; Adamovics, John; Baldock, Clive

    2010-11-01

    PRESAGE is a dosimeter that is suitable for 3D dosimetry. To be used as an ideal dosimeter, however, it should present radiologically water equivalent properties. In this work, we have investigated the radiological properties of three different PRESAGE® formulations. The radiological water equivalence was assessed by comparing the photon cross sections and radiation dosimetry properties of the three different PRESAGE® formulations with the corresponding values for water. Relative depth doses were calculated using Monte Carlo methods for 75, 125, 180 and 280 kVp and 6 MV x-ray beams. Based on the results of this study, the PRESAGE® formulations with lower halogen content are more dosimetrically water equivalent.

  6. Permanent prostate brachytherapy: Dosimetric results and analysis of a learning curve with a dynamic dose-feedback technique

    SciTech Connect

    Acher, Peter . E-mail: peter.acher@gstt.nhs.uk; Popert, Rick; Nichol, Janette; Potters, Louis; Morris, Stephen; Beaney, Ronald

    2006-07-01

    Purpose: A permanent prostate brachytherapy (PPB) program utilizing intraoperative inverse-planned dynamic dose-feedback was initiated without prior firsthand experience of alternative techniques. The purpose of this study is to assess the dosimetric learning curve associated with this approach. Methods and Materials: A total of 77 patients underwent PPB implants as monotherapy for localized prostate cancer to a prescription dose of 145 Gy with loose 125I seeds between December 2003 and June 2004. Intraoperative and postoperative dosimetric values, total implanted radioactivity, and operating room (OR) times were compared by sequential case number for all cases. Results: The median intraoperative dosimetric values were: D90 (the minimum dose to 90% of the prostate) = 170 Gy (range, 135-203 Gy), V100 (the volume of the prostate that receives 100% of the prescription dose) = 96% (range, 86-100), V150 = 66% (range, 34-86). Median postoperative dosimetric values were as follows: D90 = 168 Gy (range, 132-197 Gy), V100 = 95% (range, 86-99), V150 = 74% (range, 51-84). Median implanted activity was 0.79 mCi per cubic centimeter of prostate (range, 0.541-1.13). There was no significant correlation by case number on any postoperative dosimetric parameter studied. Door-to-door OR time was reduced from median 138 to 97.5 min per case at the end of the series with a correlation coefficient of -0.76 for the initial 28 cases. Conclusion: Satisfactory dosimetric parameters can be achieved from the outset without a learning curve effect in an appropriately trained environment. The learning curve for dynamic dose-feedback PPB in a clinic naive to other techniques is apparent in terms of OR time.

  7. Dosimetric impacts of applicator displacements and applicator reconstruction-uncertainties on 3D image-guided brachytherapy for cervical cancer

    PubMed Central

    Schindel, Joshua; Zhang, Winson; Bhatia, Sudershan K.; Sun, Wenqing

    2013-01-01

    Purpose To quantify the dosimetric impact of applicator displacements and applicator reconstruction-uncertainties through simulated planning studies of virtual applicator shifts. Material and methods Twenty randomly selected high-dose-rate (HDR) titanium tandem-and-ovoid (T&O) plans were retrospectively studied. MRI-guided, conformal brachytherapy (MRIG-CBT) plans were retrospectively generated. To simulate T&O displacement, the whole T&O set was virtually shifted on treatment planning system in the cranial (+) and the caudal (–) direction after each dose calculation. Each shifted plan was compared to an unshifted plan. To simulate T&O reconstruction-uncertainties, each tandem and ovoid was separately shifted along its axis before performing the dose calculation. After the dose calculation, the calculated isodose lines and T&O were moved back to unshifted T&O position. Shifted and shifted-back plan were compared. Results Regarding the dosimetric impact of the simulated T&O displacements, rectal D2cc values were observed as being the most sensitive to change due to T&O displacement among all dosimetric metrics regardless of point A (p < 0.013) or MRIG-CBT plans (p < 0.0277). To avoid more than 10% change, ± 1.5 mm T&O displacements were accommodated for both point A and MRIG-CBT plans. The dosimetric impact of T&O displacements on sigmoid (p < 0.0005), bladder (p < 0.0001), HR-CTV (p < 0.0036), and point A (p < 0.0015) were significantly larger in the MRIG-CBT plans than point A plans. Regarding the dosimetric impact of T&O reconstruction-uncertainties, less than ± 3.0 mm reconstruction-uncertainties were also required in order to avoid more than 10% dosimetric change in either the point A or MRIG-CBT plans. Conclusions The dosimetric impact of simulated T&O displacements was significantly larger in the MRIG-CBT plans than in the point A plans. Either ± 3 mm T&O displacement or a ± 4.5 mm T&O reconstruction-uncertainty could cause greater than 10% dosimetric

  8. Dosimetric properties of dysprosium doped calcium magnesium borate glass subjected to Co-60 gamma ray

    NASA Astrophysics Data System (ADS)

    Omar, R. S.; Wagiran, H.; Saeed, M. A.

    2016-01-01

    Thermoluminescence (TL) dosimetric properties of dysprosium doped calcium magnesium borate (CMB:Dy) glass are presented. This study is deemed to understand the application of calcium as the modifier in magnesium borate glass with the presence of dysprosium as the activator to be performed as TL dosimeter (TLD). The study provides fundamental knowledge of a glass system that may lead to perform new TL glass dosimetry application in future research. Calcium magnesium borate glass systems of (70-y) B2O3 - 20 CaO - 10 MgO-(y) Dy2O3 with 0.05 mol % ≤ y ≤ 0.7 mol % of dyprosium were prepared by melt-quenching technique. The amorphous structure and TL properties of the prepared samples were determined using powder X-ray diffraction (XRD) and TL reader; model Harshaw 4500 respectively. The samples were irradiated to Co-60 gamma source at a dose of 50 Gy. Dosimetric properties such as annealing procedure, time temperature profile (TTP) setting, optimization of Dy2O3 concentration of 0.5 mol % were determined for thermoluminescence dosimeter (TLD) reader used.

  9. First biological and dosimetric results of the free flyer biostack experiment AO015 on LDEF

    NASA Technical Reports Server (NTRS)

    Reitz, G.; Buecker, H.; Facius, R.; Horneck, G.; Schaeffer, M.; Schott, J. U.; Bayonove, J.; Beaujean, R.; Benton, E. V.; Delpoux, M.

    1991-01-01

    The main objectives of the Biostack Experiment are to study the effectiveness of the structured components of the cosmic radiation to bacterial spores, plant seeds, and animal cysts for a long duration spaceflight and to get dosimetric data such as particle fluences and spectra and total doses for the Long Duration Exposure Facility orbit. The configuration of the experiment packages allows the localization of the trajectory of the particles in each biological layer and to correlate the potential biological impairment or injury with the physical characteristics of the responsible particle. Although the Biostack Experiment was designed for a long duration flight of only nine months, most of the biological systems show a high hatching or germination rate. Some of the first observations are an increase of the mutation rate of embryonic lethals in the second generation of Arabidopsis seeds, somatic mutations, and a reduction of growth rates of corn plants and a reduction of life span of Artemia salina shrimps. The different passive detector systems are also in a good shape and give access to a proper dosimetric analysis. The results are summarized, and some aspects of future analysis are shown.

  10. The Dosimetric Impact of Prostate Rotations During Electromagnetically Guided External-Beam Radiation Therapy

    SciTech Connect

    Amro, Hanan; Hamstra, Daniel A.; Mcshan, Daniel L.; Sandler, Howard; Vineberg, Karen; Hadley, Scott; Litzenberg, Dale

    2013-01-01

    Purpose: To study the impact of daily rotations and translations of the prostate on dosimetric coverage during radiation therapy (RT). Methods and Materials: Real-time tracking data for 26 patients were obtained during RT. Intensity modulated radiation therapy plans meeting RTOG 0126 dosimetric criteria were created with 0-, 2-, 3-, and 5-mm planning target volume (PTV) margins. Daily translations and rotations were used to reconstruct prostate delivered dose from the planned dose. D{sub 95} and V{sub 79} were computed from the delivered dose to evaluate target coverage and the adequacy of PTV margins. Prostate equivalent rotation is a new metric introduced in this study to quantify prostate rotations by accounting for prostate shape and length of rotational lever arm. Results: Large variations in prostate delivered dose were seen among patients. Adequate target coverage was met in 39%, 65%, and 84% of the patients for plans with 2-, 3-, and 5-mm PTV margins, respectively. Although no correlations between prostate delivered dose and daily rotations were seen, the data showed a clear correlation with prostate equivalent rotation. Conclusions: Prostate rotations during RT could cause significant underdosing even if daily translations were managed. These rotations should be managed with rotational tolerances based on prostate equivalent rotations.

  11. Role of intracanalicular volumetric and dosimetric parameters on hearing preservation after vestibular schwannoma radiosurgery

    SciTech Connect

    Massager, Nicolas . E-mail: nmassage@ulb.ac.be; Nissim, Ouzi; Delbrouck, Carine; Devriendt, Daniel; David, Philippe; Desmedt, Francoise; Wikler, David; Hassid, Sergio; Brotchi, Jacques; Levivier, Marc

    2006-04-01

    Purpose: To analyze the relationship between hearing preservation after gamma knife radiosurgery (GKR) for vestibular schwannoma (VS) and some volumetric and dosimetric parameters of the intracanalicular components of VS. Methods and Materials: This study included 82 patients with a VS treated by GKR; all patients had no NF2 disease, a Gardner-Robertson hearing class 1-4 before treatment, a marginal dose of 12 Gy, and a radiologic and audiologic follow-up {>=}1 year post-GKR. The volume of both the entire tumor and the intracanalicular part of the tumor and the mean and integrated dose of these two volumes were correlated to the auditory outcomes of patients. Results: At last hearing follow-up, 52 patients had no hearing worsening, and 30 patients had an increase of {>=}1 class on Gardner-Robertson classification. We found that hearing preservation after GKR is significantly correlated with the intracanalicular tumor volume, as well as with the integrated dose delivered to the intracanalicular tumor volume. Conclusions: Some volumetric and dosimetric parameters of the intracanalicular part of the tumor influence hearing preservation after GKR of VS. Consequently, we advise the direct treatment of patients with preserved functional hearing and a VS including a small intracanalicular volume.

  12. A Combined Tissue Kinetics and Dosimetric Model of Respiratory Tissue Exposed to Radiation

    SciTech Connect

    John R. Ford

    2005-11-01

    Existing dosimetric models of the radiation response of tissues are essentially static. Consideration of changes in the cell populations over time has not been addressed realistically. For a single acute dose this is not a concern, but for modeling chronic exposures or fractionated acute exposures, the natural turnover and progression of cells could have a significant impact on a variety of endpoints. This proposal addresses the shortcomings of current methods by combining current dose-based calculation techniques with information on the cell turnover for a model tissue. The proposed model will examine effects at the single-cell level for an exposure of a section of human bronchiole. The cell model will be combined with Monte Carlo calculations of doses to cells and cell nuclei due to varying dose-rates of different radiation qualities. Predictions from the model of effects on survival, apoptosis rates, and changes in the number of cycling and differentiating cells will be tested experimentally. The availability of dynamic dosimetric models of tissues at the single-cell level will be useful for analysis of low-level radiation exposures and in the development of new radiotherapy protocols.

  13. Dosimetric validation of the MCNPX Monte Carlo simulation for radiobiologic studies of megavoltage grid radiotherapy

    SciTech Connect

    Zhang Hualin . E-mail: zhang.568@osu.edu; Johnson, Ellis L.; Zwicker, Robert D.

    2006-12-01

    Purpose: To validate the MCNPX Monte Carlo simulation for radiobiologic studies of megavoltage grid radiotherapy. Methods and Materials: EDR2 films, a scanning water phantom with microionization chamber and MCNPX Monte Carlo code, were used to study the dosimetric characteristics of a commercially available megavoltage grid therapy collimator. The measured dose profiles, ratios between maximum and minimum doses at 1.5 cm depth, and percentage depth dose curve were compared with those obtained in the simulations. The simulated two-dimensional dose profile and the linear-quadratic formalism of cell survival were used to calculate survival statistics of tumor and normal cells for the treatment of melanoma with a list of doses of the fractionated grid therapy. Results: A good agreement between the simulated and measured dose data was found. The therapeutic ratio based on normal cell survival has been defined and calculated for treating both the acute and late responding melanoma tumors. The grid therapy in this study was found to be advantageous for treating the acutely responding tumors, but not for late responding tumors. Conclusions: Monte Carlo technique was demonstrated to be able to provide the dosimetric characteristics for grid therapy. The therapeutic ratio was dependent not only on the single {alpha}/{beta} value, but also on the individual {alpha} and {beta} values. Acutely responding tumors and radiosensitive normal tissues are more suitable for using the grid therapy.

  14. Synthesis and characterization of CaF{sub 2}:Dy nanophosphor for dosimetric application

    SciTech Connect

    Bhadane, Mahesh S.; Dahiwale, S. S.; Bhoraskar, V. N.; Dhole, S. D.; Patil, B. J.; Kulkarni, M. S.; Bhatt, B. C.

    2015-06-24

    In this work, nanoparticles (NPs) of dysprosium doped calcium fluoride (CaF{sub 2}:Dy) 1 mol % has been prepared using simple chemical co-precipitation method and its thermoluminescence (TL) dosimetric properties were studied. The synthesized nanoparticle sample was characterized by X-ray diffraction (XRD) and the particle size of face centered cubic phase NPs was found around 30 nm. The shape, morphology and size were also observed by scanning electron microscopy (SEM). From gamma irradiated CaF{sub 2}:Dy TL curves, it was observed that the total areas of all the glow peak intensities are dramatically changed with increase in annealing temperature. Further, TL glow curve of the CaF{sub 2}:Dy at 183 °C annealed at 400 °C, showed very sharp linear response in the dose range from 1 Gy to 750 Gy. This linear response of CaF{sub 2}:Dy nanophosphor as a function of gamma dose is very useful from radiation dosimetric point of view.

  15. A Dosimetric Analysis of IMRT and Multistatic Fields Techniques for Left Breast Radiotherapy

    SciTech Connect

    Moon, Seong Kwon; Kim, Yeon Sil; Kim, Soo Young; Lee, Mi Jo; Keum, Hyun Sup; Kim, Seung Jin; Youn, Seon Min

    2011-10-01

    The purpose of this study was to analyze the dosimetric difference between intensity-modulated radiation therapy (IMRT) using 3 or 5 beams and multistatic field technique (MSF) in radiotherapy of the left breast. We made comparative analysis of two kinds of radiotherapy that can achieve improved dose homogeneity. First is a MSF that uses both major and small irradiation fields at the same time. The other is IMRT using 3 or 5 beams with an inverse planning system using multiple static multileaf collimators. We made treatment plans for 16 early left breast cancer patients who were randomly selected and had undergone breast conserving surgery and radiotherapy, and analyzed them in the dosimetric aspect. For the mean values of V{sub 95} and dose homogeneity index, no statistically significant difference was observed among the three therapies. Extreme hot spots receiving >110% of prescribed dose were not found in any of the three methods. Using Tukey's test, IMRT showed a significantly larger increase in exposure dose to the ipsilateral lung and the heart than MSF in the low-dose area, but in the high-dose area, MSF showed a slight increase. To improve dose homogeneity, the application of MSF, which can be easily planned and applied more widely, is considered optimal as an alternative to IMRT for radiotherapy of early left breast cancer.

  16. Basics of particle therapy II biologic and dosimetric aspects of clinical hadron therapy.

    PubMed

    Rong, Yi; Welsh, James

    2010-12-01

    Besides photons and electrons, high-energy particles like protons, neutrons, ⁴He ions or heavier ions (C, Ne, etc) have been finding increasing applications in the treatment of radioresistant tumors and tumors located near critical structures. The main difference between photons and hadrons is their different biologic effect and depth-dose distribution. Generally speaking, protons are superior in dosimetric aspects whereas neutrons have advantages in biologic effectiveness because of the high linear energy transfer. In 1946 Robert Wilson first published the physical advantages in dose distribution of ion particles for cancer therapy. Since that time hadronic radiotherapy has been intensively studied in physics laboratories worldwide and clinical application have gradually come to fruition. Hadron therapy was made possible by the advances in accelerator technology, which increases the particles' energy high enough to place them at any depth within the patient's body. As a follow-up to the previous article Introduction to Hadrons, this review discusses certain biologic and dosimetric aspects of using protons, neutrons, and heavy charged particles for radiation therapy. PMID:20395789

  17. 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.

  18. A Dosimetric Comparison of Proton and Intensity-Modulated Photon Radiotherapy for Pediatric Parameningeal Rhabdomyosarcomas

    SciTech Connect

    Kozak, Kevin R.; Adams, Judith; Krejcarek, Stephanie J.; Tarbell, Nancy J.; Yock, Torunn I.

    2009-05-01

    Purpose: We compared tumor and normal tissue dosimetry of proton radiation therapy with intensity-modulated radiation therapy (IMRT) for pediatric parameningeal rhabdomyosarcomas (PRMS). Methods and Materials: To quantify dosimetric differences between contemporary proton and photon treatment for pediatric PRMS, proton beam plans were compared with IMRT plans. Ten patients treated with proton radiation therapy at Massachusetts General Hospital had IMRT plans generated. To facilitate dosimetric comparisons, clinical target volumes and normal tissue volumes were held constant. Plans were optimized for target volume coverage and normal tissue sparing. Results: Proton and IMRT plans provided acceptable and comparable target volume coverage, with at least 99% of the CTV receiving 95% of the prescribed dose in all cases. Improved dose conformality provided by proton therapy resulted in significant sparing of all examined normal tissues except for ipsilateral cochlea and mastoid; ipsilateral parotid gland sparing was of borderline statistical significance (p = 0.05). More profound sparing of contralateral structures by protons resulted in greater dose asymmetry between ipsilateral and contralateral retina, optic nerves, cochlea, and mastoids; dose asymmetry between ipsilateral and contralateral parotids was of borderline statistical significance (p = 0.05). Conclusions: For pediatric PRMS, superior normal tissue sparing is achieved with proton radiation therapy compared with IMRT. Because of enhanced conformality, proton plans also demonstrate greater normal tissue dose distribution asymmetry. Longitudinal studies assessing the impact of proton radiotherapy and IMRT on normal tissue function and growth symmetry are necessary to define the clinical consequences of these differences.

  19. Thermoluminescent dosimetric properties of CaF2:Tm produced by combustion synthesis

    NASA Astrophysics Data System (ADS)

    de Vasconcelos, D. A. A.; Barros, V. S. M.; Khoury, H. J.; Asfora, V. K.; Oliveira, R. A. P.

    2016-04-01

    Calcium Fluoride is one of the oldest known thermoluminescent materials and is considered to be one of the most sensitive. This work presents the dosimetric properties results of CaF2:Tm produced by combustion synthesis. The X-ray diffraction confirmed that CaF2 was successfully produced. TL emission spectra, obtained using a Hammamatsu optical spectrometer, have the same lines of commercial CaF2:Tm, although transitions 3P0→3F4 (455 nm) and 1G4→3H6 (482 nm) are shown to be proportionally more intense. The deconvolution technique was employed and seven glow peaks were found similar to the commercial CaF2:Tm. A linear dose response curve was obtained for the range 0.1 mGy to 100 Gy, with the onset of a supralinear behavior at 50 Gy up to 100 Gy. The minimum measurable dose for gamma was around 100 μGy for a 6.0 mm diameter by 1.0 mm in thickness pellet. No significant fading was observed in 60 days of storage, within experimental uncertainties, showing that the main dosimetric peak is stable.

  20. Monte Carlo dosimetric study of the Flexisource Co-60 high dose rate source

    PubMed Central

    Granero, Domingo; Perez-Calatayud, Jose; Ballester, Facundo

    2012-01-01

    Purpose Recently, a new HDR 60Co brachytherapy source, Flexisource Co-60, has been developed (Nucletron B.V. Veenendaal, The Netherlands). This study aims to obtain dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO. Material and methods Two Monte Carlo radiation transport codes were used: Penelope2008 and GEANT4. The source was centrally-positioned in a 100 cm radius water phantom. Absorbed dose and collisional kerma were obtained using 0.01 cm (close) and 0.1 cm (far) sized voxels to provide high-resolution dosimetry near (far from) the source. Dose rate distributions obtained with the two Monte Carlo codes were compared. Results and Discussion Simulations performed with those two radiation transport codes showed an agreement typically within 0.2% for r > 0.8 cm and up to 2% closer to the source. Detailed results of dose distributions are being made available. Conclusions Dosimetric data are provided for the new Flexisource Co-60 source. These data are meant to be used in treatment planning systems in clinical practice. PMID:23346138

  1. [Mathematical simulation support to the dosimetric monitoring on the Russian segment of the International Space Station].

    PubMed

    Mitrikas, V G

    2014-01-01

    To ensure radiation safety of cosmonauts, it is necessary not only to predict, but also to reconstruct absorbed dose dynamics with the knowledge of how long cosmonauts stay in specific space vehicle compartments with different shielding properties and lacking equipment for dosimetric monitoring. In this situation, calculating is one and only way to make a correct estimate of radiation exposure of cosmonaut's organism as a whole (tissue-average dose) and of separate systems and organs. The paper addresses the issues of mathematical simulation of epy radiation environment of standard dosimetric instruments in the Russian segments of the International Space Station (ISS RS). Results of comparing the simulation and experimental data for the complement of dosimeters including ionization chamber-based radiometer R-16, DB8 dosimeters composed of semiconductor detectors, and Pille dosimeters composed of thermoluminescent detectors evidence that the current methods of simulation in support of the ISS RS radiation monitoring provide a sufficiently good agreement between the calculated and experimental data. PMID:25163341

  2. Dosimetric properties of high energy current (HEC) detector in keV x-ray beams.

    PubMed

    Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

    2015-04-01

    We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications. PMID:25789488

  3. 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

  4. Poster — Thur Eve — 74: Distributed, asynchronous, reactive dosimetric and outcomes analysis using DICOMautomaton

    SciTech Connect

    Clark, Haley; Wu, Jonn; Moiseenko, Vitali; Thomas, Steven

    2014-08-15

    Many have speculated about the future of computational technology in clinical radiation oncology. It has been advocated that the next generation of computational infrastructure will improve on the current generation by incorporating richer aspects of automation, more heavily and seamlessly featuring distributed and parallel computation, and providing more flexibility toward aggregate data analysis. In this report we describe how a recently created — but currently existing — analysis framework (DICOMautomaton) incorporates these aspects. DICOMautomaton supports a variety of use cases but is especially suited for dosimetric outcomes correlation analysis, investigation and comparison of radiotherapy treatment efficacy, and dose-volume computation. We describe: how it overcomes computational bottlenecks by distributing workload across a network of machines; how modern, asynchronous computational techniques are used to reduce blocking and avoid unnecessary computation; and how issues of out-of-date data are addressed using reactive programming techniques and data dependency chains. We describe internal architecture of the software and give a detailed demonstration of how DICOMautomaton could be used to search for correlations between dosimetric and outcomes data.

  5. TL dosimetric properties of Li2O-B2O3 glasses for gamma dosimetry.

    PubMed

    El-Adawy, A; Khaled, N E; El-Sersy, A R; Hussein, A; Donya, H

    2010-06-01

    In this work, the thermoluminescence (TL) dosimetric characteristics of lithium borate glasses have been studied in detail before and after doping with silver. The glass specimens were prepared using a conventional melt-quenching method and checked using X-ray diffraction (XRD) pattern. The resultant glow curve of the undoped gamma-irradiated samples showed one strong peak at about 178 degrees C and at a constant heating-rate (beta) of 5 degrees C/s. While, the Ag-doped samples showed two TL glow peaks around 220 and 320 degrees C, which were mainly attributed to the Ag(+) ions. Trap parameters of glow peaks of the present glass systems were extracted. The dosimetric characteristics of glass specimens were read from the TL gamma-dose response curve, which showed a reasonably good linearity behavior between glow peak areas and gamma-dose values. The present results revealed the importance of using such current selective glass structures as gamma-radiation detectors within the studied dose-range where an acceptably good fading response was observed. PMID:20122841

  6. Dosimetric characteristics of fabricated silica fibre for postal radiotherapy dose audits

    NASA Astrophysics Data System (ADS)

    Fadzil, M. S. Ahmad; Ramli, N. N. H.; Jusoh, M. A.; Kadni, T.; Bradley, D. A.; Ung, N. M.; Suhairul, H.; Mohd Noor, N.

    2014-11-01

    Present investigation aims to establish the dosimetric characteristics of a novel fabricated flat fibre TLD system for postal radiotherapy dose audits. Various thermoluminescence (TL) properties have been investigated for five sizes of 6 mol% Ge-doped optical fibres. Key dosimetric characteristics including reproducibility, linearity, fading and energy dependence have been established. Irradiations were carried out using a linear accelerator (linac) and a Cobalt-60 machine. For doses from 0.5 Gy up to 10 Gy, Ge-doped flat fibres exhibit linearity between TL yield and dose, reproducible to better than 8% standard deviation (SD) following repeat measurements (n = 3). For photons generated at potentials from 1.25 MeV to 10 MV an energy-dependent response is noted, with a coefficient of variation (CV) of less than 40% over the range of energies investigated. For 6.0 mm length flat fibres 100 μm thick × 350 pm wide, the TL fading loss following 30 days of storage at room temperature was < 8%. The Ge-doped flat fibre system represents a viable basis for use in postal radiotherapy dose audits, corrections being made for the various factors influencing the TL yield.

  7. Revision of the ICRP dosimetric model for the human respiratory tract

    SciTech Connect

    Bair, W.J.

    1990-12-01

    Although the dosimetric model of the respiratory tract used in ICRP Publication 30 had not been shown to be seriously deficient for the purpose of calculating Annual Limits on Intake (ALIs) for workers, the availability of new information led the ICRP in 1984 to create a special Task Group to review the dosimetric model of the respiratory tract and, if justified, propose revisions or a new model. The Task Group directed its efforts toward improving the model used in Publication 30 rather than developing a completely new model. The objective was a model that would facilitate calculation of biologically meaningful doses; be consistent with morphological, physiological, and radiobiological characteristics of the respiratory tract; incorporate current knowledge; meet all radiation protection needs; be user friendly by not being unnecessarily sophisticated; be adaptable to development of computer software for calculation of relevant radiation doses from knowledge of a few readily measured exposure parameters; be equally useful for assessment purposes as for calculating ALIs; be applicable to all members of the world population; and consider the influence of smoking, air pollutants, and diseases of the inhalation, deposition, and clearance of radioactive particles from the respiratory tract. The model provides for calculation of a committed dose equivalent for each region, adjusted for the relative cancer sensitivity of that region, and for the summing of these to yield a committed dose equivalent for the entire respiratory tract. 3 figs.

  8. A simulation study of irregular respiratory motion and its dosimetric impact on lung tumors

    NASA Astrophysics Data System (ADS)

    Mutaf, Y. D.; Scicutella, C. J.; Michalski, D.; Fallon, K.; Brandner, E. D.; Bednarz, G.; Huq, M. S.

    2011-02-01

    This study is aimed at providing a dosimetric evaluation of the irregular motion of lung tumors due to variations in patients' respiration. Twenty-three lung cancer patients are retrospectively enrolled in this study. The motion of the patient clinical target volume is simulated and two types of irregularities are defined: characteristic and uncharacteristic motions. Characteristic irregularities are representative of random fluctuations in the observed target motion. Uncharacteristic irregular motion is classified as systematic errors in determination of the target motion during the planning session. Respiratory traces from measurement of patient abdominal motion are also used for the target motion simulations. Characteristic irregular motion was observed to cause minimal changes in target dosimetry with the largest effect of 2.5% ± 0.9% (1σ) reduction in the minimum target dose (Dmin) observed for targets that move 2 cm on average and exhibiting 50% amplitude variations within a session. However, uncharacteristic irregular motion introduced more drastic changes in the clinical target volume (CTV) dose; 4.1% ± 1.7% reduction for 1 cm motion and 9.6% ± 1.7% drop for 2 cm. In simulations with patients' abdominal motion, corresponding changes in target dosimetry were observed to be negligible (<0.1%). Only uncharacteristic irregular motion was identified as a clinically significant source of dosimetric uncertainty.

  9. Dosimetric evaluation of a MOSFET detector for clinical application in photon therapy.

    PubMed

    Kohno, Ryosuke; Hirano, Eriko; Nishio, Teiji; Miyagishi, Tomoko; Goka, Tomonori; Kawashima, Mitsuhiko; Ogino, Takashi

    2008-01-01

    Dosimetric characteristics of a metal oxide-silicon semiconductor field effect transistor (MOSFET) detector are studied with megavoltage photon beams for patient dose verification. The major advantages of this detector are its size, which makes it a point dosimeter, and its ease of use. In order to use the MOSFET detector for dose verification of intensity-modulated radiation therapy (IMRT) and in-vivo dosimetry for radiation therapy, we need to evaluate the dosimetric properties of the MOSFET detector. Therefore, we investigated the reproducibility, dose-rate effect, accumulated-dose effect, angular dependence, and accuracy in tissue-maximum ratio measurements. Then, as it takes about 20 min in actual IMRT for the patient, we evaluated fading effect of MOSFET response. When the MOSFETs were read-out 20 min after irradiation, we observed a fading effect of 0.9% with 0.9% standard error of the mean. Further, we applied the MOSFET to the measurement of small field total scatter factor. The MOSFET for dose measurements of small field sizes was better than the reference pinpoint chamber with vertical direction. In conclusion, we assessed the accuracy, reliability, and usefulness of the MOSFET detector in clinical applications such as pinpoint absolute dosimetry for small fields. PMID:20821164

  10. High-resolution digital dosimetric system for spatial characterization of radiation fields using a thermoluminescent CaF/sub 2/:Dy crystal

    SciTech Connect

    Atari, N.A.; Svensson, G.K.

    1986-05-01

    A high-resolution digital dosimetric system has been developed for the spatial characterization of radiation fields. The system comprises the following: 0.5-mm-thick, 25-mm-diam CaF/sub 2/:Dy thermoluminescent crystal; intensified charge coupled device video camera; video cassette recorder; and a computerized image processing subsystem. The optically flat single crystal is used as a radiation imaging device and the subsequent thermally stimulated phosphorescence is viewed by the intensified camera for further processing and analysis. Parameters governing the performance characteristics of the system were measured. A spatial resolution limit of 31 +- 2 ..mu..m (1sigma) corresponding to 16 +- 1 line pair/mm measured at the 4% level of the modulation transfer function has been achieved. The full width at half maximum of the line spread function measured independently by the slit method or derived from the edge response function was found to be 69 +- 4 ..mu..m (1sigma). The high resolving power, speed of readout, good precision, wide dynamic range, and the large image storage capacity make the system suitable for the digital mapping of the relative distribution of absorbed doses for various small radiation fields and the edges of larger fields.

  11. A high-resolution digital dosimetric system for spatial characterization of radiation fields using a thermoluminescent CaF2:Dy crystal.

    PubMed

    Atari, N A; Svensson, G K

    1986-01-01

    A high-resolution digital dosimetric system has been developed for the spatial characterization of radiation fields. The system comprises the following: 0.5-mm-thick, 25-mm-diam CaF2:Dy thermoluminescent crystal; intensified charge coupled device video camera; video cassette recorder; and a computerized image processing subsystem. The optically flat single crystal is used as a radiation imaging device and the subsequent thermally stimulated phosphorescence is viewed by the intensified camera for further processing and analysis. Parameters governing the performance characteristics of the system were measured. A spatial resolution limit of 31 +/- 2 microns (1 sigma) corresponding to 16 +/- 1 line pairs/mm measured at the 4% level of the modulation transfer function has been achieved. The full width at half maximum of the line spread function measured independently by the slit method or derived from the edge response function was found to be 69 +/- 4 microns (1 sigma). The high resolving power, speed of readout, good precision, wide dynamic range, and the large image storage capacity make the system suitable for the digital mapping of the relative distribution of absorbed doses for various small radiation fields and the edges of larger fields. PMID:3724696

  12. High-resolution digital dosimetric system for spatial characterization of radiation fields using a thermoluminescent CaF2:Dy crystal

    SciTech Connect

    Atari, N.A.; Svensson, G.K.

    1986-05-01

    A high-resolution digital dosimetric system has been developed for the spatial characterization of radiation fields. The system comprises the following: 0.5-mm-thick, 25-mm-diam CaF2:Dy thermoluminescent crystal; intensified charge coupled device video camera; video cassette recorder; and a computerized image processing subsystem. The optically flat single crystal is used as a radiation imaging device and the subsequent thermally stimulated phosphorescence is viewed by the intensified camera for further processing and analysis. Parameters governing the performance characteristics of the system were measured. A spatial resolution limit of 31 +/- 2 microns (1 sigma) corresponding to 16 +/- 1 line pairs/mm measured at the 4% level of the modulation transfer function has been achieved. The full width at half maximum of the line spread function measured independently by the slit method or derived from the edge response function was found to be 69 +/- 4 microns (1 sigma). The high resolving power, speed of readout, good precision, wide dynamic range, and the large image storage capacity make the system suitable for the digital mapping of the relative distribution of absorbed doses for various small radiation fields and the edges of larger fields.

  13. Evaluation of dosimetric effect caused by slowing with multi-leaf collimator (MLC) leaves for volumetric modulated arc therapy (VMAT)

    PubMed Central

    Wang, Iris Z.; Kumaraswamy, Lalith K.; Podgorsak, Matthew B.

    2016-01-01

    Background This study is to report 1) the sensitivity of intensity modulated radiation therapy (IMRT) QA method for clinical volumetric modulated arc therapy (VMAT) plans with multi-leaf collimator (MLC) leaf errors that will not trigger MLC interlock during beam delivery; 2) the effect of non-beam-hold MLC leaf errors on the quality of VMAT plan dose delivery. Materials and methods. Eleven VMAT plans were selected and modified using an in-house developed software. For each control point of a VMAT arc, MLC leaves with the highest speed (1.87-1.95 cm/s) were set to move at the maximal allowable speed (2.3 cm/s), which resulted in a leaf position difference of less than 2 mm. The modified plans were considered as ‘standard’ plans, and the original plans were treated as the ‘slowing MLC’ plans for simulating ‘standard’ plans with leaves moving at relatively lower speed. The measurement of each ‘slowing MLC’ plan using MapCHECK®2 was compared with calculated planar dose of the ‘standard’ plan with respect to absolute dose Van Dyk distance-to-agreement (DTA) comparisons using 3%/3 mm and 2%/2 mm criteria. Results All ‘slowing MLC’ plans passed the 90% pass rate threshold using 3%/3 mm criteria while one brain and three anal VMAT cases were below 90% with 2%/2 mm criteria. For ten out of eleven cases, DVH comparisons between ‘standard’ and ‘slowing MLC’ plans demonstrated minimal dosimetric changes in targets and organs-at-risk. Conclusions For highly modulated VMAT plans, pass rate threshold (90%) using 3%/3mm criteria is not sensitive in detecting MLC leaf errors that will not trigger the MLC leaf interlock. However, the consequential effects of non-beam hold MLC errors on target and OAR doses are negligible, which supports the reliability of current patient-specific IMRT quality assurance (QA) method for VMAT plans. PMID:27069458

  14. Human Mind Maps

    ERIC Educational Resources Information Center

    Glass, Tom

    2016-01-01

    When students generate mind maps, or concept maps, the maps are usually on paper, computer screens, or a blackboard. Human Mind Maps require few resources and little preparation. The main requirements are space where students can move around and a little creativity and imagination. Mind maps can be used for a variety of purposes, and Human Mind…

  15. Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer

    SciTech Connect

    Hong, Chae-Seon; Ju, Sang Gyu Kim, Minkyu; Kim, Jin Man; Han, Youngyih; Ahn, Yong Chan; Choi, Doo Ho; Park, Hee Chul; Kim, Jung-in; Nam, Heerim; Suh, Tae-Suk

    2014-02-15

    Purpose: The authors evaluated the effects of multileaf collimator (MLC) leaf width (2.5 vs. 5 mm) on dosimetric parameters and delivery efficiencies of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck (H and N) cancers. Methods: The authors employed two types of mock phantoms: large-sized head and neck (LH and N) and small-sized C-shape (C-shape) phantoms. Step-and-shoot IMRT (S and S-IMRT) and VMAT treatment plans were designed with 2.5- and 5.0-mm MLC for both C-shape and LH and N phantoms. Their dosimetric characteristics were compared in terms of the conformity index (CI) and homogeneity index (HI) for the planning target volume (PTV), the dose to organs at risk (OARs), and the dose-spillage volume. To analyze the effects of the field and arc numbers, 9-field IMRT (9F-IMRT) and 13-field IMRT (13F-IMRT) plans were established for S and S-IMRT. For VMAT, single arc (VMAT{sub 1}) and double arc (VMAT{sub 2}) plans were established. For all plans, dosimetric verification was performed using the phantom to examine the relationship between dosimetric errors and the two leaf widths. Delivery efficiency of the two MLCs was compared in terms of beam delivery times, monitor units (MUs) per fraction, and the number of segments for each plan. Results: 2.5-mm MLC showed better dosimetric characteristics in S and S-IMRT and VMAT for C-shape, providing better CI for PTV and lower spinal cord dose and high and intermediate dose-spillage volume as compared with the 5-mm MLC (p < 0.05). However, no significant dosimetric benefits were provided by the 2.5-mm MLC for LH and N (p > 0.05). Further, beam delivery efficiency was not observed to be significantly associated with leaf width for either C-shape or LH and N. However, MUs per fraction were significantly reduced for the 2.5-mm MLC for the LH and N. In dosimetric error analysis, absolute dose evaluations had errors of less than 3%, while the Gamma passing rate was

  16. Beam’s-eye-view dosimetrics (BEVD) guided rotational station parameter optimized radiation therapy (SPORT) planning based on reweighted total-variation minimization.

    PubMed

    Kim, Hojin; Li, Ruijiang; Lee, Rena; Xing, Lei

    2015-03-01

    Conventional VMAT optimizes aperture shapes and weights at uniformly sampled stations, which is a generalization of the concept of a control point. Recently, rotational station parameter optimized radiation therapy (SPORT) has been proposed to improve the plan quality by inserting beams to the regions that demand additional intensity modulations, thus formulating nonuniform beam sampling. This work presents a new rotational SPORT planning strategy based on reweighted total-variation (TV) minimization (min.), using beam’s-eye-view dosimetrics (BEVD) guided beam selection. The convex programming based reweighted TV min. assures the simplified fluence-map, which facilitates single-aperture selection at each station for single-arc delivery. For the rotational arc treatment planning and non-uniform beam angle setting, the mathematical model needs to be modified by additional penalty term describing the fluence-map similarity and by determination of appropriate angular weighting factors. The proposed algorithm with additional penalty term is capable of achieving more efficient and deliverable plans adaptive to the conventional VMAT and SPORT planning schemes by reducing the dose delivery time about 5 to 10 s in three clinical cases (one prostate and two head-and-neck (HN) cases with a single and multiple targets). The BEVD guided beam selection provides effective and yet easy calculating methodology to select angles for denser, non-uniform angular sampling in SPORT planning. Our BEVD guided SPORT treatment schemes improve the dose sparing to femoral heads in the prostate and brainstem, parotid glands and oral cavity in the two HN cases, where the mean dose reduction of those organs ranges from 0.5 to 2.5 Gy. Also, it increases the conformation number assessing the dose conformity to the target from 0.84, 0.75 and 0.74 to 0.86, 0.79 and 0.80 in the prostate and two HN cases, while preserving the delivery efficiency, relative to conventional single-arc VMAT plans. PMID

  17. Concept Mapping

    PubMed Central

    Brennan, Laura K.; Brownson, Ross C.; Kelly, Cheryl; Ivey, Melissa K.; Leviton, Laura C.

    2016-01-01

    Background From 2003 to 2008, 25 cross-sector, multidisciplinary community partnerships funded through the Active Living by Design (ALbD) national program designed, planned, and implemented policy and environmental changes, with complementary programs and promotions. This paper describes the use of concept-mapping methods to gain insights into promising active living intervention strategies based on the collective experience of community representatives implementing ALbD initiatives. Methods Using Concept Systems software, community representatives (n=43) anonymously generated actions and changes in their communities to support active living (183 original statements, 79 condensed statements). Next, respondents (n=26, from 23 partnerships) sorted the 79 statements into self-created categories, or active living intervention approaches. Respondents then rated statements based on their perceptions of the most important strategies for creating community changes (n=25, from 22 partnerships) and increasing community rates of physical activity (n=23, from 20 partnerships). Cluster analysis and multidimensional scaling were used to describe data patterns. Results ALbD community partnerships identified three active living intervention approaches with the greatest perceived importance to create community change and increase population levels of physical activity: changes to the built and natural environment, partnership and collaboration efforts, and land-use and transportation policies. The relative importance of intervention approaches varied according to subgroups of partnerships working with different populations. Conclusions Decision makers, practitioners, and community residents can incorporate what has been learned from the 25 community partnerships to prioritize active living policy, physical project, promotional, and programmatic strategies for work in different populations and settings. PMID:23079266

  18. Dosimetric feasibility of cone-beam CT-based treatment planning compared to CT-based treatment planning

    SciTech Connect

    Yoo, Sua . E-mail: sua.yoo@duke.edu; Yin, F.-F.

    2006-12-01

    Purpose: Cone-beam computed tomography (CBCT) images are currently used for positioning verification. However, it is yet unknown whether CBCT could be used in dose calculation for replanning in adaptive radiation therapy. This study investigates the dosimetric feasibility of CBCT-based treatment planning. Methods and Materials: Hounsfield unit (HU) values and profiles of Catphan, homogeneous/inhomogeneous phantoms, and various tissue regions of patients in CBCT images were compared to those in CT. The dosimetric consequence of the HU variation was investigated by comparing CBCT-based treatment plans to conventional CT-based plans for both phantoms and patients. Results: The maximum HU difference between CBCT and CT of Catphan was 34 HU in the Teflon. The differences in other materials were less than 10 HU. The profiles for the homogeneous phantoms in CBCT displayed reduced HU values up to 150 HU in the peripheral regions compared to those in CT. The scatter and artifacts in CBCT became severe surrounding inhomogeneous tissues with reduced HU values up to 200 HU. The MU/cGy differences were less than 1% for most phantom cases. The isodose distributions between CBCT-based and CT-based plans agreed very well. However, the discrepancy was larger when CBCT was scanned without a bowtie filter than with bowtie filter. Also, up to 3% dosimetric error was observed in the plans for the inhomogeneous phantom. In the patient studies, the discrepancies of isodose lines between CT-based and CBCT-based plans, both 3D and IMRT, were less than 2 mm. Again, larger discrepancy occurred for the lung cancer patients. Conclusion: This study demonstrated the feasibility of CBCT-based treatment planning. CBCT-based treatment plans were dosimetrically comparable to CT-based treatment plans. Dosimetric data in the inhomogeneous tissue regions should be carefully validated.

  19. TU-C-17A-10: Patient Features Based Dosimetric Pareto Front Prediction In Esophagus Cancer Radiotherapy

    SciTech Connect

    Wang, J; Zhao, K; Peng, J; Hu, W; Jin, X

    2014-06-15

    Purpose: The purpose of this study is to study the feasibility of the dosimetric pareto front (PF) prediction based on patient anatomic and dosimetric parameters for esophagus cancer patients. Methods: Sixty esophagus patients in our institution were enrolled in this study. A total 2920 IMRT plans were created to generated PF for each patient. On average, each patient had 48 plans. The anatomic and dosimetric features were extracted from those plans. The mean lung dose (MLD), mean heart dose (MHD), spinal cord max dose and PTV homogeneous index (PTVHI) were recorded for each plan. The principal component analysis (PCA) was used to extract overlap volume histogram (OVH) features between PTV and other critical organs. The full dataset was separated into two parts include the training dataset and the validation dataset. The prediction outcomes were the MHD and MLD for the current study. The spearman rank correlation coefficient was used to evaluate the correlation between the anatomical features and dosimetric features. The PF was fit by the the stepwise multiple regression method. The cross-validation method was used to evaluation the model. Results: The mean prediction error of the MHD was 465 cGy with 100 repetitions. The most correlated factors were the first principal components of the OVH between heart and PTV, and the overlap between heart and PTV in Z-axis. The mean prediction error of the MLD was 195 cGy. The most correlated factors were the first principal components of the OVH between lung and PTV, and the overlap between lung and PTV in Z-axis. Conclusion: It is feasible to use patients anatomic and dosimetric features to generate a predicted PF. Additional samples and further studies were required to get a better prediction model.

  20. Geometric and dosimetric verification of step-and-shoot modulated fields with a new fast and high resolution beam imaging system

    SciTech Connect

    Bindoni, Luca . E-mail: lucabindoni@inwind.it

    2005-06-15

    , extracted from BIS maps, are compared with the corresponding scans performed with a diode detector. Disagreement is always shown in the regions outside the field penumbra (tails) and near the field edges only for field sizes {>=}15x15 cm{sup 2} due to the metal/phosphor screen higher sensitivity to low energy scattering x-rays. A straightforward correction method for the 'tails effect' was developed and then generalized to MLC-shaped fields. In order to demonstrate the validity of this procedure, the comparison between the two-dimensional (2D) dose distributions of a triangle MLC-shaped field and of two simple IMRT fields created by the superimposition of five segments resulting from BIS images and the dose distribution of the same fields achieved by film, was measured and reported. The gamma index method, introduced by Low et al. (1998), was used for 2D dose distributions analysis. Agreements are good for both 6 and 15 MV energies. The described technique provides a lower time-expensive mean to verify geometric and dosimetric accuracy of the treatment delivered in IMRT with the use of a high resolution beam imaging system and homemade software tools.

  1. Dosimetric advantages of IMPT over IMRT for laser-accelerated proton beams

    NASA Astrophysics Data System (ADS)

    Luo, W.; Li, J.; Fourkal, E.; Fan, J.; Xu, X.; Chen, Z.; Jin, L.; Price, R.; Ma, C.-M.

    2008-12-01

    As a clinical application of an exciting scientific breakthrough, a compact and cost-efficient proton therapy unit using high-power laser acceleration is being developed at Fox Chase Cancer Center. The significance of this application depends on whether or not it can yield dosimetric superiority over intensity-modulated radiation therapy (IMRT). The goal of this study is to show how laser-accelerated proton beams with broad energy spreads can be optimally used for proton therapy including intensity-modulated proton therapy (IMPT) and achieve dosimetric superiority over IMRT for prostate cancer. Desired energies and spreads with a varying δE/E were selected with the particle selection device and used to generate spread-out Bragg peaks (SOBPs). Proton plans were generated on an in-house Monte Carlo-based inverse-planning system. Fifteen prostate IMRT plans previously used for patient treatment have been included for comparison. Identical dose prescriptions, beam arrangement and consistent dose constrains were used for IMRT and IMPT plans to show the dosimetric differences that were caused only by the different physical characteristics of proton and photon beams. Different optimization constrains and beam arrangements were also used to find optimal IMPT. The results show that conventional proton therapy (CPT) plans without intensity modulation were not superior to IMRT, but IMPT can generate better proton plans if appropriate beam setup and optimization are used. Compared to IMRT, IMPT can reduce the target dose heterogeneity ((D5-D95)/D95) by up to 56%. The volume receiving 65 Gy and higher (V65) for the bladder and the rectum can be reduced by up to 45% and 88%, respectively, while the volume receiving 40 Gy and higher (V40) for the bladder and the rectum can be reduced by up to 49% and 68%, respectively. IMPT can also reduce the whole body non-target tissue dose by up to 61% or a factor 2.5. This study has shown that the laser accelerator under development has a

  2. Dosimetric comparison between model 9011 and 6711 sources in prostate implants

    SciTech Connect

    Zhang, Hualin; Beyer, David

    2013-07-01

    The purpose of this work is to evaluate the model 9011 iodine-125 ({sup 125}I) in prostate implants by comparing dosimetric coverage provided by the 6711 vs 9011 source implants. Postimplant dosimetry was performed in 18 consecutively implanted patients with prostate cancer. Two were implanted with the 9011 source and 16 with the 6711 source. For purposes of comparison, each implant was then recalculated assuming use of the other source. The same commercially available planning system was used and the specific source data for both 6711 and 9011 products were entered. The results of these calculations are compared side by side in the terms of the isodose values covering 100% (D100) and 90% (D90) of prostate volume, and the percentages of volumes of prostate, bladder, rectum, and urethra covered by 200% (V200), 150% (V150), 100% (V100), 50% (V50), and 20% (V20) of the prescribed dose as well. The 6711 source data overestimate coverage by 6.4% (ranging from 4.9% to 6.9%; median 6.6%) at D100 and by 6.6% (ranging from 6.2% to 6.8%; median 6.6%) at D90 compared with actual 9011 data. Greater discrepancies of up to 67% are seen at higher dose levels: average reduction for V100 is 2.7% (ranging from 0.6% to 7.7%; median 2.3%), for V150 is 14.6% (ranging from 6.1% to 20.5%; median 15.3%), for V200 is 14.9% (ranging from 4.8% to 19.1%; median 16%); similarly seen in bladder, rectal, and urethral coverage. This work demonstrates a clear difference in dosimetric behavior between the 9011 and 6711 sources. Using the 6711 source data for 9011 source implants would create a pronounced error in dose calculation. This study provides evidence that the 9011 source can provide the same dosimetric quality as the 6711 source, if properly used; however, the 6711 source data should not be considered as a surrogate for the 9011 source implants.

  3. Dosimetric evaluation of a three-phase adaptive radiotherapy for nasopharyngeal carcinoma using helical tomotherapy

    SciTech Connect

    Fung, Winky Wing Ki; Wu, Vincent Wing Cheung; Teo, Peter Man Lung

    2012-04-01

    Adaptive radiotherapy (ART) has been introduced to correct the radiation-induced anatomic changes in head and neck cases during a treatment course. This study evaluated the potential dosimetric benefits of applying a 3-phase adaptive radiotherapy protocol in nasopharyngeal carcinoma (NPC) patients compared with the nonadaptive single-phase treatment protocol. Ten NPC patients previously treated with this 3-phase radiation protocol using Hi-Art Tomotherapy were recruited. Two new plans, PII-ART and PIII-ART, were generated based on the up-to-date computed tomography (CT) images and contours and were used for treatment in phase two (PII; after 25th fraction) and phase three (PIII; after 35th fraction), respectively. To simulate the situation of no replanning, 2 hybrid plans denoted as PII-NART and PIII-NART were generated using the original contours pasted on the PII- and PIII-CT sets by CT-CT fusion. Dosimetric comparisons were made between the NART plans and the corresponding ART plans. In both PII- and PIII-NART plans, the doses to 95% of all the target volumes (D{sub 95}) were increased with better dose uniformity, whereas the organs at risk (OARs) received higher doses compared with the corresponding ART plans. Without replanning, the total dose to 1% of brainstem and spinal cord (D{sub 1}) significantly increased 7.87 {+-} 7.26% and 10.69 {+-} 6.72%, respectively (P = 0.011 and 0.001, respectively), in which 3 patients would have these structures overdosed when compared with those with two replannings. The total maximum doses to the optic chiasm and pituitary gland and the mean doses to the left and right parotid glands were increased by 10.50 {+-} 10.51%, 8.59 {+-} 6.10%, 3.03 {+-} 4.48%, and 2.24 {+-} 3.11%, respectively (P = 0.014, 0.003, 0.053, and 0.046, respectively). The 3-phase radiotherapy protocol showed improved dosimetric results to the critical structures while keeping satisfactory target dose coverage, which demonstrated the advantages of ART in

  4. Dosimetric evaluation of the interplay effect in respiratory-gated RapidArc radiation therapy

    SciTech Connect

    Riley, Craig; Yang, Yong Li, Tianfang; Zhang, Yongqian; Heron, Dwight E.; Huq, M. Saiful

    2014-01-15

    Purpose: Volumetric modulated arc therapy (VMAT) with gating capability has had increasing adoption in many clinics in the United States. In this new technique, dose rate, gantry rotation speed, and the leaf motion speed of multileaf collimators (MLCs) are modulated dynamically during gated beam delivery to achieve highly conformal dose coverage of the target and normal tissue sparing. Compared with the traditional gated intensity-modulated radiation therapy technique, this complicated beam delivery technique may result in larger dose errors due to the intrafraction tumor motion. The purpose of this work is to evaluate the dosimetric influence of the interplay effect for the respiration-gated VMAT technique (RapidArc, Varian Medical Systems, Palo Alto, CA). Our work consisted of two parts: (1) Investigate the interplay effect for different target residual errors during gated RapidArc delivery using a one-dimensional moving phantom capable of producing stable sinusoidal movement; (2) Evaluate the dosimetric influence in ten clinical patients’ treatment plans using a moving phantom driven with a patient-specific respiratory curve. Methods: For the first part of this study, four plans were created with a spherical target for varying residual motion of 0.25, 0.5, 0.75, and 1.0 cm. Appropriate gating windows were applied for each. The dosimetric effect was evaluated using EDR2 film by comparing the gated delivery with static delivery. For the second part of the project, ten gated lung stereotactic body radiotherapy cases were selected and reoptimized to be delivered by the gated RapidArc technique. These plans were delivered to a phantom, and again the gated treatments were compared to static deliveries by the same methods. Results: For regular sinusoidal motion, the dose delivered to the target was not substantially affected by the gating windows when evaluated with the gamma statistics, suggesting the interplay effect has a small role in respiratory-gated Rapid

  5. Multi-institutional dosimetric and geometric commissioning of image-guided small animal irradiators

    SciTech Connect

    Lindsay, P. E.; Granton, P. V.; Hoof, S. van; Hermans, J.; Gasparini, A.; Jelveh, S.; Clarkson, R.; Kaas, J.; Wittkamper, F.; Sonke, J.-J.; Verhaegen, F.; Jaffray, D. A.

    2014-03-15

    Purpose: To compare the dosimetric and geometric properties of a commercial x-ray based image-guided small animal irradiation system, installed at three institutions and to establish a complete and broadly accessible commissioning procedure. Methods: The system consists of a 225 kVp x-ray tube with fixed field size collimators ranging from 1 to 44 mm equivalent diameter. The x-ray tube is mounted opposite a flat-panel imaging detector, on a C-arm gantry with 360° coplanar rotation. Each institution performed a full commissioning of their system, including half-value layer, absolute dosimetry, relative dosimetry (profiles, percent depth dose, and relative output factors), and characterization of the system geometry and mechanical flex of the x-ray tube and detector. Dosimetric measurements were made using Farmer-type ionization chambers, small volume air and liquid ionization chambers, and radiochromic film. The results between the three institutions were compared. Results: At 225 kVp, with 0.3 mm Cu added filtration, the first half value layer ranged from 0.9 to 1.0 mm Cu. The dose-rate in-air for a 40 × 40 mm{sup 2} field size, at a source-to-axis distance of 30 cm, ranged from 3.5 to 3.9 Gy/min between the three institutions. For field sizes between 2.5 mm diameter and 40 × 40 mm{sup 2}, the differences between percent depth dose curves up to depths of 3.5 cm were between 1% and 4% on average, with the maximum difference being 7%. The profiles agreed very well for fields >5 mm diameter. The relative output factors differed by up to 6% for fields larger than 10 mm diameter, but differed by up to 49% for fields ≤5 mm diameter. The mechanical characteristics of the system (source-to-axis and source-to-detector distances) were consistent between all three institutions. There were substantial differences in the flex of each system. Conclusions: With the exception of the half-value layer, and mechanical properties, there were significant differences between the

  6. Dosimetric properties of an amorphous silicon EPID for verification of modulated electron radiotherapy

    SciTech Connect

    Chatelain, Cecile; Vetterli, Daniel; Henzen, Dominik; Favre, Pascal; Fix, Michael K.; Manser, Peter; Morf, Daniel; Scheib, Stefan

    2013-06-15

    Purpose: To investigate the dosimetric properties of an electronic portal imaging device (EPID) for electron beam detection and to evaluate its potential for quality assurance (QA) of modulated electron radiotherapy (MERT). Methods: A commercially available EPID was used to detect electron beams shaped by a photon multileaf collimator (MLC) at a source-surface distance of 70 cm. The fundamental dosimetric properties such as reproducibility, dose linearity, field size response, energy response, and saturation were investigated for electron beams. A new method to acquire the flood-field for the EPID calibration was tested. For validation purpose, profiles of open fields and various MLC fields (square and irregular) were measured with a diode in water and compared to the EPID measurements. Finally, in order to use the EPID for QA of MERT delivery, a method was developed to reconstruct EPID two-dimensional (2D) dose distributions in a water-equivalent depth of 1.5 cm. Comparisons were performed with film measurement for static and dynamic monoenergy fields as well as for multienergy fields composed by several segments of different electron energies. Results: The advantageous EPID dosimetric properties already known for photons as reproducibility, linearity with dose, and dose rate were found to be identical for electron detection. The flood-field calibration method was proven to be effective and the EPID was capable to accurately reproduce the dose measured in water at 1.0 cm depth for 6 MeV, 1.3 cm for 9 MeV, and 1.5 cm for 12, 15, and 18 MeV. The deviations between the output factors measured with EPID and in water at these depths were within {+-}1.2% for all the energies with a mean deviation of 0.1%. The average gamma pass rate (criteria: 1.5%, 1.5 mm) for profile comparison between EPID and measurements in water was better than 99% for all the energies considered in this study. When comparing the reconstructed EPID 2D dose distributions at 1.5 cm depth to film

  7. Dosimetric Evaluation of Different Intensity-Modulated Radiotherapy Techniques for Breast Cancer After Conservative Surgery.

    PubMed

    Zhang, Fuli; Wang, Yadi; Xu, Weidong; Jiang, Huayong; Liu, Qingzhi; Gao, Junmao; Yao, Bo; Hou, Jun; He, Heliang

    2015-10-01

    Intensity-modulated radiotherapy (IMRT) potentially leads to a more favorite dose distribution compared to 3-dimensional or conventional tangential radiotherapy (RT) for breast cancer after conservative surgery or mastectomy. The aim of this study was to compare dosimetric parameters of the planning target volume (PTV) and organs at risk (OARs) among helical tomotherapy (HT), inverse-planned IMRT (IP-IMRT), and forward-planned field in field (FP-FIF) IMRT techniques after breast-conserving surgery. Computed tomography scans from 20 patients (12 left sided and 8 right sided) previously treated with T1N0 carcinoma were selected for this dosimetric planning study. We designed HT, IP-IMRT, and FP-FIF plans for each patient. Plans were compared according to dose-volume histogram analysis in terms of PTV homogeneity and conformity indices (HI and CI) as well as OARs dose and volume parameters. Both HI and CI of the PTV showed statistically significant difference among IP-IMRT, FP-FIF, and HT with those of HT were best (P < .05). Compared to FP-FIF, IP-IMRT showed smaller exposed volumes of ipsilateral lung, heart, contralateral lung, and breast, while HT indicated smaller exposed volumes of ipsilateral lung but larger exposed volumes of contralateral lung and breast as well as heart. In addition, HT demonstrated an increase in exposed volume of ipsilateral lung (except for fraction of lung volume receiving >30 Gy and 20 Gy), heart, contralateral lung, and breast compared with IP-IMRT. For breast cancer radiotherapy (RT) after conservative surgery, HT provides better dose homogeneity and conformity of PTV compared to IP-IMRT and FP-FIF techniques, especially for patients with supraclavicular lymph nodes involved. Meanwhile, HT decreases the OAR volumes receiving higher doses with an increase in the volumes receiving low doses, which is known to lead to an increased rate of radiation-induced secondary malignancies. Hence, composite factors including dosimetric advantage

  8. Maps & minds : mapping through the ages

    USGS Publications Warehouse

    U.S. Geological Survey

    1984-01-01

    Throughout time, maps have expressed our understanding of our world. Human affairs have been influenced strongly by the quality of maps available to us at the major turning points in our history. "Maps & Minds" traces the ebb and flow of a few central ideas in the mainstream of mapping. Our expanding knowledge of our cosmic neighborhood stems largely from a small number of simple but grand ideas, vigorously pursued.

  9. Mapping: A Course.

    ERIC Educational Resources Information Center

    Whitmore, Paul M.

    1988-01-01

    Reviews the history of cartography. Describes the contributions of Strabo and Ptolemy in early maps. Identifies the work of Gerhard Mercator as the most important advancement in mapping. Discusses present mapping standards from history. (CW)

  10. SU-E-T-456: Development of An EPID-Based Output Measurement and Dosimetric Verification Tool for Electron Beam Therapy

    SciTech Connect

    Ding, A; Han, B; Xing, L

    2014-06-01

    Purpose: To develop an efficient and robust method for output and absolute dosimetric measurements of electron beam therapy by using a high spatialresolution and high frame-rate amorphous silicon flat-panel electronic portal imaging device (EPID). Methods: A previously-established EPID dosimetry system was extended to measure the output factors of electron beams of various sizes and their planar dose distributions at reference depths. Specific EPID responses to different electron energies were derived from Monte Carlo (MC) simulations to de-convolve the EPID raw images to the incident electron fluence map. To reconstruct the 2D water-based dose distribution map at reference depths for different energies, the fluence map was further convolved with a MC simulated pencil beam kernel. Different energies of 6, 9, 12, 16, and 20 MeV from a Varian C-series linac were tested. Standard square fields ranging from 2×2 to 15×15 cm{sup 2} were measured and validated against film/ion chamber measurements. Small fields of different patient cases with irregular cutout shapes were also tested. Results: The EPIDmeasured output factors for 2×2, 3×3, 6×6, and 10×10 cm{sup 2} fields with all electron energies agree with the film/ion chamber data within 2.7%. The average discrepancy between EPID and film/ion chamber measurements was 1.4%. The differences for the three patient cases were 0.1%, 2.1%, and 1.6%. Deliveries with different monitor units were tested and the results exhibited good linearity. Measurements with different dose rate showed that the dose rate dependence was less than 1%. Using the proposed method, 2D absolute dose maps were created from the EPID raw images and the results were consistent with film measurements. Conclusion: The efficient data readout and portability of the newly developed EPID system provides an efficient and accurate solution for electron beam therapy. It addresses an important unmet clinical need for a fast and reliable small field output

  11. Verification of the agreement of two dosimetric methods with radioiodine therapy in hyperthyroid patients

    SciTech Connect

    Canzi, Cristina; Zito, Felicia; Voltini, Franco; Reschini, Eugenio; Gerundini, Paolo

    2006-08-15

    The aim of this study was to verify the capability of an MIRD formula-based dosimetric method to predict radioiodine kinetics (fraction of administered iodine transferred to the thyroid, U{sub 0}, and effective clearance rate, {lambda}{sub eff}) and absorbed dose after oral therapeutic {sup 131}I administration. The method is based on {sup 123}I intravenous administration and five subsequent gamma camera measured uptake values determined separately on different structures within the thyroid. Another dosimetric method based on only the {sup 123}I 24-h uptake and a fixed {lambda}{sub eff} value was also considered. Eighty-nine hyperthyroid patients (10 with Graves' disease and 79 with autonomously functioning nodules) were studied and 132 thyroidal structures were evaluated. The mean time interval between dosimetry and therapy was 20{+-}10d. Uptake values were measured at 2, 4, 24, 48, and 120 h during dosimetry and at 2, 4, 24, 48, 96, and 168 h during therapy. The value 0.125d{sup -1} was chosen in the fixed-{lambda}{sub eff} method. The planned doses to the target ranged from 120 to 250 Gy depending on the type and severity of hyperthyroidism. The following significant correlations between therapeutic and dosimetric parameters were found: U{sub 0}ther=0.88U{sub 0}dos (r=0.97,p<0.01), {lambda}{sub eff}ther=1.01{lambda}{sub eff}dos (r=0.85,p<0.01), and D{sub estimated}=0.85D{sub planned} (r=0.88,p<0.01). The percent difference between U{sub 0}ther and U{sub 0}dos ranged from -44 to 32% and between {lambda}{sub eff}ther and {lambda}{sub eff}dos from -32 to 48%. U{sub 0}ther was lower than U{sub 0}dos in 74% of cases: this can be explained by the self-stunning effect of {sup 131}I therapeutic activity that produced a dose of about 20 Gy with a maximum dose rate of 0.6 Gy/h over the initial 24-48 h. The differences, {delta}D, between the estimated and the planned doses ranged from -42% (-87 Gy) to 32% (59 Gy); in 73% of cases the difference was within {+-}35 Gy

  12. Growth of silver doped Li2B4O7 single crystals for dosimetric application

    NASA Astrophysics Data System (ADS)

    Patra, G. D.; Singh, S. G.; Singh, A. K.; Desai, D. G.; Tiwari, B.; Sen, S.; Gadkari, S. C.

    2013-02-01

    High quality lithium tetraborate; Li2B4O7 (LTB) single crystals with varying concentrations of Ag have been grown using the Czochralski technique. Optimized growth parameters enabled us to grow crystals that were transparent, colorless, crack-free, and core-free. The grown LTB:Ag crystals were characterized using UV-VIS-NIR transmission, photoluminescence (PL) and thermoluminescence (TL) measurements. The transmission of about 85 % in the range from 200 nm to 1100 nm revealed a good optical quality of the grown crystals. The TL glow peak of LTB:Ag single crystals at 160°C with an emission at 270 nm is found useful for the dosimetric applications. The dose response is found to be linear in the range from 100 mGy to 50 Gy.

  13. The ESR dosimetric features of strontium sulfate and temperature effects on radiation-induced signals

    NASA Astrophysics Data System (ADS)

    Acar, Ali Osman; Polat, Mustafa; Aydin, Talat; Aydaş, Canan

    2016-06-01

    In the present work, the ESR dosimetric potential of strontium sulfate has been investigated in the radiation dose range of 1-100 Gy. It does not exhibit any ESR signal before irradiation. However, irradiation produced three intensive resonance signals (A, B and C) which increase linearly in the studied dose range. Variable temperature study showed that all ESR signals were found to decrease significantly at temperatures higher than 340 K. Kinetic studies performed at high temperatures showed that at least two distinct radical species with the activation energy values of 42.8±3.6 and 88.2±5.8 kJ/mol, respectively, contributed to the ESR signal B.

  14. Dosimetric Characteristics of 6 MV Modified Beams by Physical Wedges of a Siemens Linear Accelerator.

    PubMed

    Zabihzadeh, Mansour; Birgani, Mohammad Javad Tahmasebi; Hoseini-Ghahfarokhi, Mojtaba; Arvandi, Sholeh; Hoseini, Seyed Mohammad; Fadaei, Mahbube

    2016-01-01

    Physical wedges still can be used as missing tissue compensators or filters to alter the shape of isodose curves in a target volume to reach an optimal radiotherapy plan without creating a hotspot. The aim of this study was to investigate the dosimetric properties of physical wedges filters such as off-axis photon fluence, photon spectrum, output factor and half value layer. The photon beam quality of a 6 MV Primus Siemens modified by 150 and 450 physical wedges was studied with BEAMnrc Monte Carlo (MC) code. The calculated present depth dose and dose profile curves for open and wedged photon beam were in good agreement with the measurements. Increase of wedge angle increased the beam hardening and this effect was more pronounced at the heal region. Using such an accurate MC model to determine of wedge factors and implementation of it as a calculation algorithm in the future treatment planning systems is recommended. PMID:27221838

  15. Dosimetric and clinical experience in eye proton treatment at INFN-LNS

    SciTech Connect

    Cirrone, G. A. P.; Cuttone, G.; Di Rosa, F.; Lojacono, P.; Mongelli, V.; Patti, I. V.; Pittera, S.; Russo, G.; Valastro, L. M.; Lo Nigro, S.; Ott, J.; Reibaldi, A.; Privitera, G.; Raffaele, L.; Salamone, V.; Spatola, C.; Sabini, M. G.

    2009-05-04

    After six years of activity 155 patients have been treated inside the CATANA (Centro di AdroTerapia ed Applicazioni Nucleari Avanzate) facility. CATANA is the first and unique proton therapy facility in which the 62 MeV proton beams, accelerated by a Superconducting Cyclotron, are used for the radio-therapeutic treatments of choroidal and iris melanomas. Inside CATANA new absolute and relative dosimetric techniques have been developed in order to achieve the best results in terms of treatment precision and dose release accuracy. The follow-up results for 42 patients demonstrated the efficacy of high energy protons in the radiotherapeutic field and encouraged us in our activity in the battle against cancer.

  16. Investigation of pulsed IMRT and VMAT for re-irradiation treatments: dosimetric and delivery feasibilities.

    PubMed

    Lin, Mu-Han; Price, Robert A; Li, Jinsheng; Kang, Shengwei; Li, Jie; Ma, C-M

    2013-11-21

    Many tumor cells demonstrate hyperradiosensitivity at doses below ~50 cGy. Together with the increased normal tissue repair under low dose rate, the pulsed low dose rate radiotherapy (PLDR), which separates a daily fractional dose of 200 cGy into 10 pulses with 3 min interval between pulses (~20 cGy/pulse and effective dose rate 6.7 cGy min−1), potentially reduces late normal tissue toxicity while still providing significant tumor control for re-irradiation treatments. This work investigates the dosimetric and technical feasibilities of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT)-based PLDR treatments using Varian Linacs. Twenty one cases (12 real re-irradiation cases) including treatment sites of pancreas, prostate, pelvis, lung, head-and-neck, and breast were recruited for this study. The lowest machine operation dose rate (100 MU min−1) was employed in the plan delivery. Ten-field step-and-shoot IMRT and dual-arc VMAT plans were generated using the Eclipse TPS with routine planning strategies. The dual-arc plans were delivered five times to achieve a 200 cGy daily dose (~20 cGy arc−1). The resulting plan quality was evaluated according to the heterogeneity and conformity indexes (HI and CI) of the planning target volume (PTV). The dosimetric feasibility of retaining the hyperradiosensitivity for PLDR was assessed based on the minimum and maximum dose in the target volume from each pulse. The delivery accuracy of VMAT and IMRT at the 100 MU min−1 machine operation dose rate was verified using a 2D diode array and ion chamber measurements. The delivery reproducibility was further investigated by analyzing the Dynalog files of repeated deliveries. A comparable plan quality was achieved by the IMRT (CI 1.10–1.38; HI 1.04–1.10) and the VMAT (CI 1.08–1.26; HI 1.05–1.10) techniques. The minimum/maximum PTV dose per pulse is 7.9 ± 5.1 cGy/33.7 ± 6.9 cGy for the IMRT and 12.3 ± 4.1 cGy/29.2 ± 4.7 cGy for the

  17. Dosimetric investigation of the solar erythemal UV radiation protection provided by beards and moustaches.

    PubMed

    Parisi, A V; Turnbull, D J; Downs, N; Smith, D

    2012-07-01

    A dosimetric technique has been employed to establish the amount of erythemal ultraviolet radiation (UVR) protection provided by facial hair considering the influence of solar zenith angle (SZA) and beard-moustache length. The facial hair reduced the exposure ratios (ERs) to approximately one-third of those to the sites with no hair. The variation in the ERs over the different sites was reduced compared with the cases with no beard. The ultraviolet protection factor (UPF) provided by the facial hair ranged from 2 to 21. The UPF decreases with increasing SZA. The minimum UPF was in the 53-62° range. The longer hair provides a higher UPF at the smaller SZA, but the difference between the protection provided by the longer hair compared with the shorter hair reduces with increasing SZA. Protection from UVR is provided by the facial hair; however, it is not very high, particularly at the higher SZA. PMID:22090417

  18. Investigation of pulsed IMRT and VMAT for re-irradiation treatments: dosimetric and delivery feasibilities

    NASA Astrophysics Data System (ADS)

    Lin, Mu-Han; Price, Robert A., Jr.; Li, Jinsheng; Kang, Shengwei; Li, Jie; Ma, C.-M.

    2013-11-01

    Many tumor cells demonstrate hyperradiosensitivity at doses below ˜50 cGy. Together with the increased normal tissue repair under low dose rate, the pulsed low dose rate radiotherapy (PLDR), which separates a daily fractional dose of 200 cGy into 10 pulses with 3 min interval between pulses (˜20 cGy/pulse and effective dose rate 6.7 cGy min-1), potentially reduces late normal tissue toxicity while still providing significant tumor control for re-irradiation treatments. This work investigates the dosimetric and technical feasibilities of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT)-based PLDR treatments using Varian Linacs. Twenty one cases (12 real re-irradiation cases) including treatment sites of pancreas, prostate, pelvis, lung, head-and-neck, and breast were recruited for this study. The lowest machine operation dose rate (100 MU min-1) was employed in the plan delivery. Ten-field step-and-shoot IMRT and dual-arc VMAT plans were generated using the Eclipse TPS with routine planning strategies. The dual-arc plans were delivered five times to achieve a 200 cGy daily dose (˜20 cGy arc-1). The resulting plan quality was evaluated according to the heterogeneity and conformity indexes (HI and CI) of the planning target volume (PTV). The dosimetric feasibility of retaining the hyperradiosensitivity for PLDR was assessed based on the minimum and maximum dose in the target volume from each pulse. The delivery accuracy of VMAT and IMRT at the 100 MU min-1 machine operation dose rate was verified using a 2D diode array and ion chamber measurements. The delivery reproducibility was further investigated by analyzing the Dynalog files of repeated deliveries. A comparable plan quality was achieved by the IMRT (CI 1.10-1.38 HI 1.04-1.10) and the VMAT (CI 1.08-1.26 HI 1.05-1.10) techniques. The minimum/maximum PTV dose per pulse is 7.9 ± 5.1 cGy/33.7 ± 6.9 cGy for the IMRT and 12.3 ± 4.1 cGy/29.2 ± 4.7 cGy for the VMAT. Six out of

  19. Dosimetric differences in flattened and flattening filter-free beam treatment plans

    PubMed Central

    Yan, Yue; Yadav, Poonam; Bassetti, Michael; Du, Kaifang; Saenz, Daniel; Harari, Paul; Paliwal, Bhudatt R.

    2016-01-01

    This study investigated the dosimetric differences in treatment plans from flattened and flattening filter-free (FFF) beams from the TrueBeam System. A total of 104 treatment plans with static (sliding window) intensity-modulated radiotherapy beams and volumetric-modulated arc therapy (VMAT) beams were generated for 15 patients involving three cancer sites. In general, the FFF beam provides similar target coverage as the flattened beam with improved dose sparing to organ-at-risk (OAR). Among all three cancer sites, the head and neck showed more important differences between the flattened beam and FFF beam. The maximum reduction of the FFF beam in the mean dose reached up to 2.82 Gy for larynx in head and neck case. Compared to the 6 MV flattened beam, the 10 MV FFF beam provided improved dose sparing to certain OARs, especially for VMAT cases. Thus, 10 MV FFF beam could be used to improve the treatment plan. PMID:27217620

  20. The Dosimetric Parameters Investigation of the Pulsed X-ray and Gamma Radiation Sources

    NASA Astrophysics Data System (ADS)

    Stuchebrov, S. G.; Miloichikova, I. A.; Shilova, X. O.

    2016-01-01

    The most common type of radiation used for diagnostic purposes are X-rays. However, X-rays methods have limitations related to the radiation dose for the biological objects. It is known that the use of the pulsed emitting source synchronized with the detection equipment for internal density visualization of objects significant reduces the radiation dose to the object. In the article the analysis of the suitability of the different dosimetric equipment for the radiation dose estimation of the pulsed emitting sources is carried out. The approbation results on the pulsed X-ray generator RAP-160-5 of the dosimetry systems workability with the pulse radiation and its operation range are presented. The results of the dose field investigation of the portable betatron OB-4 are demonstrated. The depth dose distribution in the air, lead and water of the pulsed bremsstrahlung generated by betatron are shown.

  1. The role of deep centers in formation of dosimetric properties of wide-gap materials

    NASA Astrophysics Data System (ADS)

    Nikiforov, S. V.; Kortov, V. S.

    2014-11-01

    The direct and indirect methods of experimental detection of deep traps in wide-gap insulators are described. The experimentally observed effects of influence of deep traps with different nature on luminescent and dosimetric properties of materials are analyzed. It is established that the most wide-spread and well-studied effects are the sensitization and superlinearity of dose response. They are interpreted in terms of the kinetic model of competitive electron traps. Taking into account the temperature dependence of capture probability by deep traps in this model allows one to explain some new effects associated with luminescence thermal quenching. The luminescence model of Al2O3:C single crystal is described. In this model the temperature dependence of competitive interaction between the main and deep traps is caused by thermal ionization of excited states of F-centers.

  2. Intensity-modulated radiotherapy in high-grade gliomas: Clinical and dosimetric results

    SciTech Connect

    Narayana, Ashwatha . E-mail: narayana@mskcc.org; Yamada, Josh; Berry, Sean; Shah, Priti B.S.; Hunt, Margie; Gutin, Philip H.; Leibel, Steven A.

    2006-03-01

    Purpose: To report preliminary clinical and dosimetric data from intensity-modulated radiotherapy (IMRT) for malignant gliomas. Methods and Materials: Fifty-eight consecutive high-grade gliomas were treated between January 2001 and December 2003 with dynamic multileaf collimator IMRT, planned with the inverse approach. A dose of 59.4-60 Gy at 1.8-2.0 Gy per fraction was delivered. A total of three to five noncoplanar beams were used to cover at least 95% of the target volume with the prescription isodose line. Glioblastoma accounted for 70% of the cases, and anaplastic oligodendroglioma histology (pure or mixed) was seen in 15% of the cases. Surgery consisted of biopsy only in 26% of the patients, and 80% received adjuvant chemotherapy. Results: With a median follow-up of 24 months, 85% of the patients have relapsed. The median progression-free survival time for anaplastic astrocytoma and glioblastoma histology was 5.6 and 2.5 months, respectively. The overall survival time for anaplastic glioma and glioblastoma was 36 and 9 months, respectively. Ninety-six percent of the recurrences were local. No Grade IV/V late neurologic toxicities were noted. A comparative dosimetric analysis revealed that regardless of tumor location, IMRT did not significantly improve target coverage compared with three-dimensional planning. However, IMRT resulted in a decreased maximum dose to the spinal cord, optic nerves, and eye by 16%, 7%, and 15%, respectively, owing to its improved dose conformality. The mean brainstem dose also decreased by 7%. Intensity-modulated radiotherapy delivered with a limited number of beams did not result in an increased dose to the normal brain. Conclusions: It is unlikely that IMRT will improve local control in high-grade gliomas without further dose escalation compared with conventional radiotherapy. However, it might result in decreased late toxicities associated with radiotherapy.

  3. Neovascular Glaucoma After Stereotactic Radiotherapy for Juxtapapillary Choroidal Melanoma: Histopathologic and Dosimetric Findings

    SciTech Connect

    Fernandes, Bruno F.; Weisbrod, Daniel; Yuecel, Yeni H.; Follwell, Matthew; Krema, Hatem; Heydarian, Mostafa; Xu Wei; Payne, David; McGowan, Hugh; Simpson, Ernest R.; Laperriere, Normand; Sahgal, Arjun

    2011-06-01

    Purpose: Enucleation after stereotactic radiotherapy (SRT) for juxtapapillary choroidal melanoma may be required because of tumor progression (TP) or the development of intractable radiation-induced neovascular glaucoma (NVG). We compare pathologic changes and dosimetric findings in those eyes enucleated secondary to NVG as opposed to TP to better understand potential mechanisms. Methods and Materials: Patients with juxtapapillary choroidal melanoma treated with SRT (70 Gy in 5 fractions, alternate days over a total of 10 days) at the Princess Margaret Hospital, Toronto, Ontario, Canada, who underwent enucleation between 1998 and 2006 were selected. We correlated dosimetric data based on the patient's original SRT treatment plan with histopathologic findings in the retina, optic nerve head, and anterior chamber. A dedicated ocular pathologist reviewed each case in a blinded fashion. Results: Ten eyes in ten patients were enucleated after SRT. Six were enucleated secondary to NVG and four secondary to because of TP. Aggressive tumor features such as invasion of the sclera and epithelioid cell type were observed predominantly in the TP group. Retinal damage was more predominant in the NVG group, as were findings of radiation-related retinal vascular changes of fibrinoid necrosis and hyalinization. No conclusive radiation-related effects were found in the anterior chamber. The maximum point dose and dose to 0.1 cc were lower for the anterior chamber as compared with the dose to the tumor, retina, and optic nerve head. The mean 0.1-cc doses to the retina were 69.4 Gy and 73.5 Gy and to the anterior chamber were 4.9 Gy and 17.3 Gy for the NVG group and tumor progression group, respectively. Conclusions: Our findings suggest that NVG is due to radiation damage to the posterior chamber of the eye rather than primary radiation damage to the anterior segment.

  4. Evaluation of Specific Absorption Rate as a Dosimetric Quantity for Electromagnetic Fields Bioeffects

    PubMed Central

    Panagopoulos, Dimitris J.; Johansson, Olle; Carlo, George L.

    2013-01-01

    Purpose To evaluate SAR as a dosimetric quantity for EMF bioeffects, and identify ways for increasing the precision in EMF dosimetry and bioactivity assessment. Methods We discuss the interaction of man-made electromagnetic waves with biological matter and calculate the energy transferred to a single free ion within a cell. We analyze the physics and biology of SAR and evaluate the methods of its estimation. We discuss the experimentally observed non-linearity between electromagnetic exposure and biological effect. Results We find that: a) The energy absorbed by living matter during exposure to environmentally accounted EMFs is normally well below the thermal level. b) All existing methods for SAR estimation, especially those based upon tissue conductivity and internal electric field, have serious deficiencies. c) The only method to estimate SAR without large error is by measuring temperature increases within biological tissue, which normally are negligible for environmental EMF intensities, and thus cannot be measured. Conclusions SAR actually refers to thermal effects, while the vast majority of the recorded biological effects from man-made non-ionizing environmental radiation are non-thermal. Even if SAR could be accurately estimated for a whole tissue, organ, or body, the biological/health effect is determined by tiny amounts of energy/power absorbed by specific biomolecules, which cannot be calculated. Moreover, it depends upon field parameters not taken into account in SAR calculation. Thus, SAR should not be used as the primary dosimetric quantity, but used only as a complementary measure, always reporting the estimating method and the corresponding error. Radiation/field intensity along with additional physical parameters (such as frequency, modulation etc) which can be directly and in any case more accurately measured on the surface of biological tissues, should constitute the primary measure for EMF exposures, in spite of similar uncertainty to predict

  5. Dosimetric Feasibility of Hypofractionated Proton Radiotherapy for Neoadjuvant Pancreatic Cancer Treatment

    SciTech Connect

    Kozak, Kevin R.; Kachnic, Lisa A.; Adams, Judith C; Crowley, Elizabeth M.; Alexander, Brian M.; Mamon, Harvey J.; Ryan, David P.; DeLaney, Thomas F.; Hong, Theodore S. . E-mail: tshong1@partners.org

    2007-08-01

    Purpose: To evaluate tumor and normal tissue dosimetry of a 5 cobalt gray equivalent (CGE) x 5 fraction proton radiotherapy schedule, before initiating a clinical trial of neoadjuvant, short-course proton radiotherapy for pancreatic adenocarcinoma. Methods and Materials: The first 9 pancreatic cancer patients treated with neoadjuvant intensity-modulated radiotherapy (1.8 Gy x 28) at the Massachusetts General Hospital had treatment plans generated using a 5 CGE x 5 fraction proton regimen. To facilitate dosimetric comparisons, clinical target volumes and normal tissue volumes were held constant. Plans were optimized for target volume coverage and normal tissue sparing. Results: Hypofractionated proton and conventionally fractionated intensity-modulated radiotherapy plans both provided acceptable target volume coverage and dose homogeneity. Improved dose conformality provided by the hypofractionated proton regimen resulted in significant sparing of kidneys, liver, and small bowel, evidenced by significant reductions in the mean doses, expressed as percentage prescribed dose, to these structures. Kidney and liver sparing was most evident in low-dose regions ({<=}20% prescribed dose for both kidneys and {<=}60% prescribed dose for liver). Improvements in small-bowel dosimetry were observed in high- and low-dose regions. Mean stomach and duodenum doses, expressed as percentage prescribed dose, were similar for the two techniques. Conclusions: A proton radiotherapy schedule consisting of 5 fractions of 5 CGE as part of neoadjuvant therapy for adenocarcinoma of the pancreas seems dosimetrically feasible, providing excellent target volume coverage, dose homogeneity, and normal tissue sparing. Hypofractionated proton radiotherapy in this setting merits Phase I clinical trial investigation.

  6. Gamma Knife irradiation method based on dosimetric controls to target small areas in rat brains

    SciTech Connect

    Constanzo, Julie; Paquette, Benoit; Charest, Gabriel; Masson-Côté, Laurence; Guillot, Mathieu

    2015-05-15

    Purpose: Targeted and whole-brain irradiation in humans can result in significant side effects causing decreased patient quality of life. To adequately investigate structural and functional alterations after stereotactic radiosurgery, preclinical studies are needed. The purpose of this work is to establish a robust standardized method of targeted irradiation on small regions of the rat brain. Methods: Euthanized male Fischer rats were imaged in a stereotactic bed, by computed tomography (CT), to estimate positioning variations relative to the bregma skull reference point. Using a rat brain atlas and the stereotactic bregma coordinates obtained from CT images, different regions of the brain were delimited and a treatment plan was generated. A single isocenter treatment plan delivering ≥100 Gy in 100% of the target volume was produced by Leksell GammaPlan using the 4 mm diameter collimator of sectors 4, 5, 7, and 8 of the Gamma Knife unit. Impact of positioning deviations of the rat brain on dose deposition was simulated by GammaPlan and validated with dosimetric measurements. Results: The authors’ results showed that 90% of the target volume received 100 ± 8 Gy and the maximum of deposited dose was 125 ± 0.7 Gy, which corresponds to an excellent relative standard deviation of 0.6%. This dose deposition calculated with GammaPlan was validated with dosimetric films resulting in a dose-profile agreement within 5%, both in X- and Z-axes. Conclusions: The authors’ results demonstrate the feasibility of standardizing the irradiation procedure of a small volume in the rat brain using a Gamma Knife.

  7. Correlation of Clinical and Dosimetric Factors With Adverse Pulmonary Outcomes in Children After Lung Irradiation

    SciTech Connect

    Venkatramani, Rajkumar; Kamath, Sunil; Wong, Kenneth; Malvar, Jemily; Sposto, Richard; Goodarzian, Fariba; Freyer, David R.; Keens, Thomas G.; and others

    2013-08-01

    Purpose: To identify the incidence and the risk factors for pulmonary toxicity in children treated for cancer with contemporary lung irradiation. Methods and Materials: We analyzed clinical features, radiographic findings, pulmonary function tests, and dosimetric parameters of children receiving irradiation to the lung fields over a 10-year period. Results: We identified 109 patients (75 male patients). The median age at irradiation was 13.8 years (range, 0.04-20.9 years). The median follow-up period was 3.4 years. The median prescribed radiation dose was 21 Gy (range, 0.4-64.8 Gy). Pulmonary toxic chemotherapy included bleomycin in 58.7% of patients and cyclophosphamide in 83.5%. The following pulmonary outcomes were identified and the 5-year cumulative incidence after irradiation was determined: pneumonitis, 6%; chronic cough, 10%; pneumonia, 35%; dyspnea, 11%; supplemental oxygen requirement, 2%; radiographic interstitial lung disease, 40%; and chest wall deformity, 12%. One patient died of progressive respiratory failure. Post-irradiation pulmonary function tests available from 44 patients showed evidence of obstructive lung disease (25%), restrictive disease (11%), hyperinflation (32%), and abnormal diffusion capacity (12%). Thoracic surgery, bleomycin, age, mean lung irradiation dose (MLD), maximum lung dose, prescribed dose, and dosimetric parameters between V{sub 22} (volume of lung exposed to a radiation dose ≥22 Gy) and V{sub 30} (volume of lung exposed to a radiation dose ≥30 Gy) were significant for the development of adverse pulmonary outcomes on univariate analysis. MLD, maximum lung dose, and V{sub dose} (percentage of volume of lung receiving the threshold dose or greater) were highly correlated. On multivariate analysis, MLD was the sole significant predictor of adverse pulmonary outcome (P=.01). Conclusions: Significant pulmonary dysfunction occurs in children receiving lung irradiation by contemporary techniques. MLD rather than prescribed

  8. Dosimetric accuracy of proton therapy for chordoma patients with titanium implants

    PubMed Central

    Verburg, Joost M.; Seco, Joao

    2013-01-01

    Purpose: To investigate dosimetric errors in proton therapy treatment planning due to titanium implants, and to determine how these affect postoperative passively scattered proton therapy for chordoma patients with orthopedic hardware. Methods: The presence of titanium hardware near the tumor may affect the dosimetric accuracy of proton therapy. Artifacts in the computed tomography (CT) scan can cause errors in the proton stopping powers used for dose calculation, which are derived from CT numbers. Also, clinical dose calculation algorithms may not accurately simulate proton beam transport through the implants, which have very different properties as compared to human tissue. The authors first evaluated the impact of these two main issues. Dose errors introduced by metal artifacts were studied using phantoms with and without titanium inserts, and patient scans on which a metal artifact reduction method was applied. Pencil-beam dose calculations were compared to models of nuclear interactions in titanium and Monte Carlo simulations. Then, to assess the overall impact on treatment plans for chordoma, the authors compared the original clinical treatment plans to recalculated dose distributions employing both metal artifact reduction and Monte Carlo methods. Results: Dose recalculations of clinical proton fields showed that metal artifacts cause range errors up to 6 mm distal to regions affected by CT artifacts. Monte Carlo simulations revealed dose differences >10% in the high-dose area, and range differences up to 10 mm. Since these errors are mostly local in nature, the large number of fields limits the impact on target coverage in the chordoma treatment plans to a small decrease of dose homogeneity. Conclusions: In the presence of titanium implants, CT metal artifacts and the approximations of pencil-beam dose calculations cause considerable errors in proton dose calculation. The spatial distribution of the errors however limits the overall impact on passively

  9. Design, manufacture, and evaluation of an anthropomorphic pelvic phantom purpose-built for radiotherapy dosimetric intercomparison

    SciTech Connect

    Harrison, K. M.; Ebert, M. A.; Kron, T.; Howlett, S. J.; Cornes, D.; Hamilton, C. S.; Denham, J. W.

    2011-10-15

    Purpose: An anthropomorphic pelvic phantom was designed and constructed to meet specific criteria for multicenter radiotherapy dosimetric intercomparison. Methods: Three dimensional external and organ outlines were generated from a computed tomography image set of a male pelvis, forming the basis of design for an anatomically realistic phantom. Clinically relevant points of interest were selected throughout the dataset where point-dose values could be measured with thermoluminescence dosimeters and a small-volume ionization chamber. Following testing, three materials were selected and the phantom was manufactured using modern prototyping techniques into five separate coronal slices. Time lines and resource requirements for the phantom design and manufacture were recorded. The ability of the phantom to mimic the entire treatment chain was tested. Results: The phantom CT images indicated that organ densities and geometries were comparable to those of the original patient. The phantom proved simple to load for dosimetry and rapid to assemble. Due to heat release during manufacture, small air gaps and density heterogeneities were present throughout the phantom. The overall cost for production of the prototype phantom was comparable to other commercial anthropomorphic phantoms. The phantom was shown to be suitable for use as a ''patient'' to mimic the entire treatment chain for typical external beam radiotherapy for prostate and rectal cancer. Conclusions: The phantom constructed for the present study incorporates all characteristics necessary for accurate Level III intercomparison studies. Following use in an extensive Level III dosimetric comparison over a large time scale and geographic area, the phantom retained mechanical stability and did not show signs of radiation-induced degradation.

  10. Predicting Nonauditory Adverse Radiation Effects Following Radiosurgery for Vestibular Schwannoma: A Volume and Dosimetric Analysis

    SciTech Connect

    Hayhurst, Caroline; Monsalves, Eric; Bernstein, Mark; Gentili, Fred; Heydarian, Mostafa; Tsao, May; Schwartz, Michael; Prooijen, Monique van; Millar, Barbara-Ann; Menard, Cynthia; Kulkarni, Abhaya V.; Laperriere, Norm; Zadeh, Gelareh

    2012-04-01

    Purpose: To define clinical and dosimetric predictors of nonauditory adverse radiation effects after radiosurgery for vestibular schwannoma treated with a 12 Gy prescription dose. Methods: We retrospectively reviewed our experience of vestibular schwannoma patients treated between September 2005 and December 2009. Two hundred patients were treated at a 12 Gy prescription dose; 80 had complete clinical and radiological follow-up for at least 24 months (median, 28.5 months). All treatment plans were reviewed for target volume and dosimetry characteristics; gradient index; homogeneity index, defined as the maximum dose in the treatment volume divided by the prescription dose; conformity index; brainstem; and trigeminal nerve dose. All adverse radiation effects (ARE) were recorded. Because the intent of our study was to focus on the nonauditory adverse effects, hearing outcome was not evaluated in this study. Results: Twenty-seven (33.8%) patients developed ARE, 5 (6%) developed hydrocephalus, 10 (12.5%) reported new ataxia, 17 (21%) developed trigeminal dysfunction, 3 (3.75%) had facial weakness, and 1 patient developed hemifacial spasm. The development of edema within the pons was significantly associated with ARE (p = 0.001). On multivariate analysis, only target volume is a significant predictor of ARE (p = 0.001). There is a target volume threshold of 5 cm3, above which ARE are more likely. The treatment plan dosimetric characteristics are not associated with ARE, although the maximum dose to the 5th nerve is a significant predictor of trigeminal dysfunction, with a threshold of 9 Gy. The overall 2-year tumor control rate was 96%. Conclusions: Target volume is the most important predictor of adverse radiation effects, and we identified the significant treatment volume threshold to be 5 cm3. We also established through our series that the maximum tolerable dose to the 5th nerve is 9 Gy.

  11. SU-C-213-06: Dosimetric Verification of 3D Printed Electron Bolus

    SciTech Connect

    Rasmussen, K; Corbett, M; Pelletier, C; Huang, Z; Feng, Y; Jung, J

    2015-06-15

    Purpose: To determine the dosimetric effect of 3D printed bolus in an anthropomorphic phantom. Methods: Conformable bolus material was generated for an anthropomorphic phantom from a DICOM volume. The bolus generated was a uniform expansion of 5mm applied to the nose region of the phantom, as this is a difficult area to uniformly apply bolus clinically. A Printrbot metal 3D Printer using PLA plastic generated the bolus. A 9MeV anterior beam with a 5cm cone was used to deliver dose to the nose of the phantom. TLD measurements were compared to predicted values at the phantom surface. Film planes were analyzed for the printed bolus, a standard 5mm bolus sheet placed on the phantom, and the phantom with no bolus applied to determine depth and dose distributions. Results: TLDs measured within 2.5% of predicted value for the 3D bolus. Film demonstrated a more uniform dose distribution in the nostril region for the 3d printed bolus than the standard bolus. This difference is caused by the air gap created around the nostrils by the standard bolus, creating a secondary build-up region. Both demonstrated a 50% central axis dose shift of 5mm relative to the no bolus film. HU for the bolus calculated the PLA electron density to be ∼1.1g/cc. Physical density was measured to be 1.3g/cc overall. Conclusion: 3D printed PLA bolus demonstrates improved dosimetric performance to standard bolus for electron beams with complex phantom geometry.

  12. Dosimetric Quantities for Computed Tomography Examinations of Paediatric Patients on the Thoracic and Abdominal Regions

    SciTech Connect

    Flores-M, E.; Gamboa de Buen, I.; Buenfil, A. E.; Ruiz-Trejo, C.; Dies, P.

    2010-12-07

    Computed Tomography (CT) is a high dose X ray imaging procedure and its use has rapidly increased in the last two decades fueled by the development of helical CT. The aim of this study is to present values of the dosimetric quantities for CT paediatric examinations of thoracic and abdominal regions. The protocols studied were those of chest, lung-mediastine, chest-abdomen, pulmonary high resolution and mediastine-abdomen, which are the more common examinations performed at ''Hospital Infantil de Mexico Federico Gomez'' in the thoracic-abdominal region. The measurements were performed on a Siemens SOMATOM Sensation 16 CT Scanner and the equipment used was a CT pencil ionization chamber, connected to an electrometer. This system was calibrated for RQT9 CT beam quality. A PMMA head phantom with diameter of 16 cm and length of 15 cm was also used. The dosimetric quantities measured were the weighted air kerma index (C{sub w}), the volumetric dose index (C{sub vol}) and the CT air kerma-length product. It was found that the pulmonary high resolution examination presented the highest values for the C{sub w}(31.1 mGy) and C{sub vol}(11.1 mGy). The examination with the lowest values of these two quantities was the chest-abdomen protocol with 10.5 mGy for C{sub w} and 5.5 mGy for C{sub vol}. However, this protocol presented the highest value for P{sub KL,CT}(282.2 mGy cm) when considering the average clinical length of the examinations.

  13. Dosimetric Effects of Air Pockets Around High-Dose Rate Brachytherapy Vaginal Cylinders

    SciTech Connect

    Richardson, Susan; Palaniswaamy, Geethpriya; Grigsby, Perry W.

    2010-09-01

    Purpose: Most physicians use a single-channel vaginal cylinder for postoperative endometrial cancer brachytherapy. Recent published data have identified air pockets between the vaginal cylinders and the vaginal mucosa. The purpose of this research was to evaluate the incidence, size, and dosimetric effects of these air pockets. Methods and Materials: 25 patients receiving postoperative vaginal cuff brachytherapy with a high-dose rate vaginal cylinders were enrolled in this prospective data collection study. Patients were treated with 6 fractions of 200 to 400 cGy per fraction prescribed at 5 mm depth. Computed tomography simulation for brachytherapy treatment planning was performed for each fraction. The quantity, volume, and dosimetric impact of the air pockets surrounding the cylinder were quantified. Results: In 25 patients, a total of 90 air pockets were present in 150 procedures (60%). Five patients had no air pockets present during any of their treatments. The average number of air pockets per patient was 3.6, with the average total air pocket volume being 0.34 cm{sup 3} (range, 0.01-1.32 cm{sup 3}). The average dose reduction to the vaginal mucosa at the air pocket was 27% (range, 9-58%). Ten patients had no air pockets on their first fraction but air pockets occurred in subsequent fractions. Conclusion: Air pockets between high-dose rate vaginal cylinder applicators and the vaginal mucosa are present in the majority of fractions of therapy, and their presence varies from patient to patient and fraction to fraction. The existence of air pockets results in reduced radiation dose to the vaginal mucosa.

  14. Conventional Versus Automated Implantation of Loose Seeds in Prostate Brachytherapy: Analysis of Dosimetric and Clinical Results

    SciTech Connect

    Genebes, Caroline; Filleron, Thomas; Graff, Pierre; Jonca, Frédéric; Huyghe, Eric; Thoulouzan, Matthieu; Soulie, Michel; Malavaud, Bernard; Aziza, Richard; Brun, Thomas; Delannes, Martine; Bachaud, Jean-Marc

    2013-11-15

    Purpose: To review the clinical outcome of I-125 permanent prostate brachytherapy (PPB) for low-risk and intermediate-risk prostate cancer and to compare 2 techniques of loose-seed implantation. Methods and Materials: 574 consecutive patients underwent I-125 PPB for low-risk and intermediate-risk prostate cancer between 2000 and 2008. Two successive techniques were used: conventional implantation from 2000 to 2004 and automated implantation (Nucletron, FIRST system) from 2004 to 2008. Dosimetric and biochemical recurrence-free (bNED) survival results were reported and compared for the 2 techniques. Univariate and multivariate analysis researched independent predictors for bNED survival. Results: 419 (73%) and 155 (27%) patients with low-risk and intermediate-risk disease, respectively, were treated (median follow-up time, 69.3 months). The 60-month bNED survival rates were 95.2% and 85.7%, respectively, for patients with low-risk and intermediate-risk disease (P=.04). In univariate analysis, patients treated with automated implantation had worse bNED survival rates than did those treated with conventional implantation (P<.0001). By day 30, patients treated with automated implantation showed lower values of dose delivered to 90% of prostate volume (D90) and volume of prostate receiving 100% of prescribed dose (V100). In multivariate analysis, implantation technique, Gleason score, and V100 on day 30 were independent predictors of recurrence-free status. Grade 3 urethritis and urinary incontinence were observed in 2.6% and 1.6% of the cohort, respectively, with no significant differences between the 2 techniques. No grade 3 proctitis was observed. Conclusion: Satisfactory 60-month bNED survival rates (93.1%) and acceptable toxicity (grade 3 urethritis <3%) were achieved by loose-seed implantation. Automated implantation was associated with worse dosimetric and bNED survival outcomes.

  15. SU-E-T-09: A Dosimetric Analysis of Various Clinically Used Bolus Materials

    SciTech Connect

    Stowe, M; Yeager, C; Zhou, F; Hand, C

    2014-06-01

    Purpose: To evaluate the dosimetric effect of various clinically used bolus materials. Methods: Materials investigated include solid water, superflab, wet gauze, wet sheets, Play-Doh{sup ™}, and gauze embedded with petroleum jelly. Each bolusing material was scanned in a Philips CT to determine the Hounsfield unit (HU) and to verify uniformity throughout the material. Using the corresponding HU, boluses of 0.5 cm and 1.0 cm thicknesses were created in the Eclipse treatment planning system (TPS) on a solid water phantom. Dose was calculated at various depths for beam energies 6 MV, 6 MeV, 9 MeV, and 12 MeV to determine the effects of each material on deposition of dose. In addition, linac-based measurements at these energies were made using a farmer chamber in solid water. Wet sheets and wet gauze were measured with various water content to quantify the effects on dose. Results: Preliminary CT scans find a range in HU of bolus materials from −120 to almost 300. There is a trend in the dose at depth based on the HU of the material; however inconsistencies are found when the bolus materials have a negative HU value. The measured data indicates that there is a linear relationship between the mass of water in a material and the dose reading, the slope of which is material dependent. Conclusion: Due to the variation in HU of the bolus materials studied, it is recommended that any new bolus be evaluated before clinical use to determine physical and dosimetric properties. If possible, patients should have bolus included in their CT scans; or if the bolus is created in the TPS, the HU should correspond to the material used. For water-soaked materials, once the bolus material is selected (gauze or sheet), the bolusing effect is only dependent on the amount of water applied to the material.

  16. Bolus-dependent dosimetric effect of positioning errors for tangential scalp radiotherapy with helical tomotherapy

    SciTech Connect

    Lobb, Eric

    2014-04-01

    The dosimetric effect of errors in patient position is studied on-phantom as a function of simulated bolus thickness to assess the need for bolus utilization in scalp radiotherapy with tomotherapy. A treatment plan is generated on a cylindrical phantom, mimicking a radiotherapy technique for the scalp utilizing primarily tangential beamlets. A planning target volume with embedded scalplike clinical target volumes (CTVs) is planned to a uniform dose of 200 cGy. Translational errors in phantom position are introduced in 1-mm increments and dose is recomputed from the original sinogram. For each error the maximum dose, minimum dose, clinical target dose homogeneity index (HI), and dose-volume histogram (DVH) are presented for simulated bolus thicknesses from 0 to 10 mm. Baseline HI values for all bolus thicknesses were in the 5.5 to 7.0 range, increasing to a maximum of 18.0 to 30.5 for the largest positioning errors when 0 to 2 mm of bolus is used. Utilizing 5 mm of bolus resulted in a maximum HI value of 9.5 for the largest positioning errors. Using 0 to 2 mm of bolus resulted in minimum and maximum dose values of 85% to 94% and 118% to 125% of the prescription dose, respectively. When using 5 mm of bolus these values were 98.5% and 109.5%. DVHs showed minimal changes in CTV dose coverage when using 5 mm of bolus, even for the largest positioning errors. CTV dose homogeneity becomes increasingly sensitive to errors in patient position as bolus thickness decreases when treating the scalp with primarily tangential beamlets. Performing a radial expansion of the scalp CTV into 5 mm of bolus material minimizes dosimetric sensitivity to errors in patient position as large as 5 mm and is therefore recommended.

  17. Dosimetric Quantities for Computed Tomography Examinations of Paediatric Patients on the Thoracic and Abdominal Regions

    NASA Astrophysics Data System (ADS)

    Flores-M, E.; Buenfil, A. E.; Dies, P.; Gamboa-deBuen, I.; Ruiz-Trejo, C.

    2010-12-01

    Computed Tomography (CT) is a high dose X ray imaging procedure and its use has rapidly increased in the last two decades fueled by the development of helical CT. The aim of this study is to present values of the dosimetric quantities for CT paediatric examinations of thoracic and abdominal regions. The protocols studied were those of chest, lung-mediastine, chest-abdomen, pulmonary high resolution and mediastine-abdomen, which are the more common examinations performed at "Hospital Infantil de México Federico Gómez" in the thoracic-abdominal region. The measurements were performed on a Siemens SOMATOM Sensation 16 CT Scanner and the equipment used was a CT pencil ionization chamber, connected to an electrometer. This system was calibrated for RQT9 CT beam quality. A PMMA head phantom with diameter of 16 cm and length of 15 cm was also used. The dosimetric quantities measured were the weighted air kerma index (Cw), the volumetric dose index (Cvol) and the CT air kerma-length product. It was found that the pulmonary high resolution examination presented the highest values for the Cw (31.1 mGy) and Cvol (11.1 mGy). The examination with the lowest values of these two quantities was the chest-abdomen protocol with 10.5 mGy for Cw and 5.5 mGy for Cvol. However, this protocol presented the highest value for PKL,CT (282.2 mGy cm) when considering the average clinical length of the examinations.

  18. SU-E-J-167: Dosimetric Consequences From Minimal Displacements in APBI with SAVI Applicators

    SciTech Connect

    Chandrasekara, S; Dumitru, N; Hyvarinen, M; Pella, S

    2015-06-15

    Purpose: To determine the importance of providing proper solid immobilization in every fraction of treatment in APBI with brachytherapy. Methods: 125 patients treated with APBI brachytherapy with SAVI applicators at SFRO Boca Raton, from 2013–2015 were considered for this retrospective study. The CT scans of each patient, which were taken before each treatment, were imported in to the Oncentra treatment planning system. Then they were compared with the initial CT scan which was used for the initial plan. Deviation in displacements in reference to ribs and skin surface was measured and dosimetric evaluations respective to the initial image were performed. Results: Small deviations in displacements were observed from the SAVI applicator to the ribs and the skin surface. Dosimetric evaluations revealed, very small changes in the inter-fractionation position make significant differences in the maximum dose to critical organs. Additionally, the volume of the cavity also changed between fractions. As a Result, the maximum dose manifested variance between 10% and 32% in ribs and skin surface respectively. Conclusion: It appears that taking a CT scan before each treatment is necessary to minimize the risk of delivering undesired high doses to the critical organs. This study indicates, in 30% of the cases re-planning was necessary between treatments. We conclude that, treatment planning teams should evaluate the placement of the device by analyzing the CT images before each treatment and they must be prepared for re-planning if needed. This study also reveals the urgent need of improving the immobilization methods with APBI when treating with the SAVI applicator.

  19. Clinical and dosimetric factors of radiation-induced esophageal injury: Radiation-induced esophageal toxicity

    PubMed Central

    Qiao, Wen-Bo; Zhao, Yan-Hui; Zhao, Yan-Bin; Wang, Rui-Zhi

    2005-01-01

    AIM: To analyze the clinical and dosimetric predictive factors for radiation-induced esophageal injury in patients with non-small-cell lung cancer (NSCLC) during three-dimensional conformal radiotherapy (3D-CRT). METHODS: We retrospectively analyzed 208 consecutive patients (146 men and 62 women) with NSCLC treated with 3D-CRT. The median age of the patients was 64 years (range 35-87 years). The clinical and treatment parameters including gender, age, performance status, sequential chemotherapy, concurrent chemotherapy, presence of carinal or subcarinal lymph nodes, pretreatment weight loss, mean dose to the entire esophagus, maximal point dose to the esophagus, and percentage of volume of esophagus receiving >55 Gy were studied. Clinical and dosimetric factors for radiation-induced acute and late grade 3-5 esophageal injury were analyzed according to Radiation Therapy Oncology Group (RTOG) criteria. RESULTS: Twenty-five (12%) of the two hundred and eight patients developed acute or late grade 3-5 esophageal injury. Among them, nine patients had both acute and late grade 3-5 esophageal injury, two died of late esophageal perforation. Concurrent chemotherapy and maximal point dose to the esophagus ≥60 Gy were significantly associated with the risk of grade 3-5 esophageal injury. Fifty-four (26%) of the two hundred and eight patients received concurrent chemotherapy. Among them, 25 (46%) developed grade 3-5 esophageal injury (P = 0.0001<0.01). However, no grade 3-5 esophageal injury occurred in patients who received a maximal point dose to the esophagus <60 Gy (P = 0.0001<0.01). CONCLUSION: Concurrent chemotherapy and the maximal esophageal point dose ≥60 Gy are significantly associated with the risk of grade 3-5 esophageal injury in patients with NSCLC treated with 3D-CRT. PMID:15849822

  20. Clinical and dosimetric experience with MammoSite-based brachytherapy under the RTOG 0413 protocol.

    PubMed

    Wojcicka, Jadwiga B; Lasher, Donette E; Malcom, Ronald; Fortier, Gregory

    2007-01-01

    MammoSite balloon brachytherapy is a relatively new technique for partial breast irradiation. The present paper focuses on the treatment planning, dosimetry, and quality assurance aspects of that treatment, based on the Radiation Therapy Oncology Group 0413 randomized prospective trial (RTOG 0413) protocol. We investigate the usefulness of evaluating implants for treatment appropriateness according to the full set of RTOG criteria as compared with the manufacturer's guidelines. We describe our methods to improve MammoSite balloon implants that would otherwise not comply with the protocol. The initially acquired computed tomography (CT) images are evaluated for tissue conformance, balloon surface-to-skin distance, and balloon symmetry. If the implant fails to meet the foregoing criteria, corrective action such as delay in the CT scan, balloon manipulation, or fluid volume adjustment is taken, and the patient is re-scanned. If the corrective action appears to be successful, three dimensional treatment planning and dose-volume histogram analysis is performed to evaluate the geometric and dosimetric parameters with regard to the RTOG 0413 protocol. The evaluated parameters include, volume ratio of the lumpectomy cavity to the ipsilateral breast, target volume coverage, tissue-balloon conformance, balloon symmetry, minimal balloon surface-to-skin distance, maximum skin dose, and normal breast tissue dose-volume parameters V150 and V200. Among our implants, 21.7% did not initially meet the RTOG 0413 acceptance criteria. Asymmetry and poor conformance values reduce the target volume coverage, and so an implant with moderate conformance and asymmetry can be within the manufacturer's guidelines, but still not meet the RTOG criteria. Our intervention corrected all but one of the implants that failed to meet the criteria. Manipulating the cavity and adjusting the balloon volume may salvage an implant and meet the strict geometric and dosimetric criteria imposed by the RTOG

  1. Monte Carlo investigation of the dosimetric effect of the Autoscan ultrasound probe for guidance in radiotherapy

    NASA Astrophysics Data System (ADS)

    Martyn, Michael; O'Shea, Tuathan; Harris, Emma; Bamber, Jeffrey; Gilroy, Stephen; Foley, Mark J.

    2016-04-01

    The aim of this study was to quantify the dosimetric effect of the Autoscan™ ultrasound probe, which is a 3D transperineal probe used for real-time tissue tracking during the delivery of radiotherapy. CT images of an anthropomorphic phantom, with and without the probe placed in contact with its surface, were obtained (0.75 mm slice width, 140 kVp). CT datasets were used for relative dose calculation in Monte Carlo simulations of a 7-field plan delivered to the phantom. The Monte Carlo software packages BEAMnrc and DOSXYZnrc were used for this purpose. A number of simulations, which varied the distance of the radiation field edge from the probe face (0 mm to 5 mm), were performed. Perineal surface doses as a function of distance from the radiation field edge, with and without the probe in place, were compared. The presence of the probe was found to result in an increase in perineal surface dose, relative to the maximum dose. The maximum increase in surface dose was 18.15%, at a probe face to field edge distance of 0 mm. However increases in surface dose fall-off rapidly as this distance increases, agreeing within Monte Carlo simulation uncertainty at distances >= 5 mm. Using data from three patient volunteers, a typical probe face to field edge distance was calculated to be ≍20 mm. Our results therefore indicate that the presence of the probe is unlikely to adversely affect a typical patient treatment, since the dosimetric effect of the probe is minimal at these distances.

  2. Mapping the Heart

    ERIC Educational Resources Information Center

    Hulse, Grace

    2012-01-01

    In this article, the author describes how her fourth graders made ceramic heart maps. The impetus for this project came from reading "My Map Book" by Sara Fanelli. This book is a collection of quirky, hand-drawn and collaged maps that diagram a child's world. There are maps of her stomach, her day, her family, and her heart, among others. The…

  3. Fundamentals of Physical Mapping

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This book chapter provides an overview of physical mapping in plants and its use for map-based gene cloning. A brief overview of cytogenetics-based physical mapping strategies, and physical mapping approaches currently used and the lessons learnt from the success stories were furnished. The statisti...

  4. National Atlas maps

    USGS Publications Warehouse

    U.S. Geological Survey

    1991-01-01

    The National Atlas of the United States of America was published by the U.S. Geological Survey in 1970. Its 765 maps and charts are on 335 14- by 19-inch pages. Many of the maps span facing pages. It's worth a quick trip to the library just to leaf through all 335 pages of this book. Rapid scanning of its thematic maps yields rich insights to the geography of issues of continuing national interest. On most maps, the geographic patterns are still valid, though the data are not current. The atlas is out of print, but many of its maps can be purchased separately. Maps that span facing pages in the atlas are printed on one sheet. The maps dated after 1970 are either revisions of original atlas maps, or new maps published in atlas format. The titles of the separate maps are listed here.

  5. Google Maps: You Are Here

    ERIC Educational Resources Information Center

    Jacobsen, Mikael

    2008-01-01

    Librarians use online mapping services such as Google Maps, MapQuest, Yahoo Maps, and others to check traffic conditions, find local businesses, and provide directions. However, few libraries are using one of Google Maps most outstanding applications, My Maps, for the creation of enhanced and interactive multimedia maps. My Maps is a simple and…

  6. Dosimetric prerequisites for routine clinical use of photon emitting brachytherapy sources with average energy higher than 50 kev

    SciTech Connect

    Li Zuofeng; Das, Rupak K.; De Werd, Larry A.; Ibbott, Geoffrey S.; Meigooni, Ali S.; Perez-Calatayud, Jose; Rivard, Mark J.; Sloboda, Ronald S.; Williamson, Jeffrey F.

    2007-01-15

    This paper presents the recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Therapeutic Radiology and Oncology (ESTRO) on the dosimetric parameters to be characterized, and dosimetric studies to be performed to obtain them, for brachytherapy sources with average energy higher than 50 keV that are intended for routine clinical use. In addition, this document makes recommendations on procedures to be used to maintain vendor source strength calibration accuracy. These recommendations reflect the guidance of the AAPM and the ESTRO for its members, and may also be used as guidance to vendors and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.

  7. Estimation of a cosmonaut's radiation hazard during long-term space missions on the basis of a generalized dosimetric function.

    PubMed

    Shafirkin, A V; Petrov, V M

    2002-01-01

    This paper presents a new concept of radiation hazard assessment for spacecraft crew members during long term space missions on the basis of a generalized dosimetric function. This new dosimetric function enables a complicated nature of space radiation exposure to be reduced to the conditions of a standard irradiation. It can be obtained on the basis of mean-tissue equivalent dose values calculated for each space radiation source and transmission coefficients describing the influence of the complex spatial and temporal distribution of the absorbed dose in the cosmonaut's body on the radiobiological effects. The combination of cosmic ionizing radiation with other non-radiation nature factors in flight can also be accounted for. In terms of the generalized dose, it is possible to assess the nature and extent of lowering a crew working capacity, as well as radiation risk, both during a flight and post flight period. PMID:12539776

  8. Dosimetric Characteristics of Circular 6-MeV X-Ray Beams for Stereotactic Radiotherapy with a Linear Accelerator

    NASA Astrophysics Data System (ADS)

    Wysocka, A.; Rostkowska, J.; Kania, M.; Bulski, W.; Fijuth, J.

    2000-01-01

    Dosimetric characteristics of 6 MeV circular X-ray beams of diameters ranging from 7.5 to 35.0 mm are reported. The 6-MeV X-ray beam from Clinac 2300CD was formed using additional cylindrical BrainLAB's collimators. The mechanical stability of the entire system was verified. Specific quantities measured include tissue maximum ratios (TMR), beam profiles (off-axis ratios OAR) and relative output factors. Measurements of these parameters were performed in a water phantom using small cylindrical ionization chambers and a diamond detector. Comparison of TMR values measured with the ionization chamber and the diamond detector showed no significant differences. It was shown that the latter yields more accurate results for beam profiles than ionization chambers. The mechanical and dosimetric characteristics of this radiotherapy unit are found to be suitable for stereotactic radiosurgery and radiotherapy.

  9. The work of the ICRP dose calculational task group: Issues in implementation of the ICRP dosimetric methodology

    SciTech Connect

    Eckerman, K.F.

    1999-01-01

    Committee 2 of the International Commission on Radiological Protection (ICRP) has had efforts underway to provide the radiation protection community with age-dependent dose coefficients, i.e.g, the dose per unit intake. The Task Group on Dose Calculations, chaired by the author, is responsible for the computation of these coefficients. The Task Group, formed in 1974 to produce ICRP Publication 30, is now international in its membership and its work load has been distributed among the institutions represented on the task group. This paper discusses: (1) recent advances in biokinetic modeling; (2) the recent changes in the dosimetric methodology; (3) the novel computational problems with some of the ICRP quantities; and (4) quality assurance issues which the Task Group has encountered. Potential future developments of the dosimetric framework which might strengthen the relationships with the emerging understanding of radiation risk will also be discussed.

  10. Map reading tools for map libraries.

    USGS Publications Warehouse

    Greenberg, G.L.

    1982-01-01

    Engineers, navigators and military strategists employ a broad array of mechanical devices to facilitate map use. A larger number of map users such as educators, students, tourists, journalists, historians, politicians, economists and librarians are unaware of the available variety of tools which can be used with maps to increase the speed and efficiency of their application and interpretation. This paper identifies map reading tools such as coordinate readers, protractors, dividers, planimeters, and symbol-templets according to a functional classification. Particularly, arrays of tools are suggested for use in determining position, direction, distance, area and form (perimeter-shape-pattern-relief). -from Author

  11. [Metrological and operating characteristics of thermoluminescent and photographic film dosimeters for the centralized individual dosimetric monitoring of medical personnel].

    PubMed

    Kalmykov, L Z; Gorelik, G I; Stadnik, L L; Romanova, I N; Kovalevskaia, L N

    1989-07-01

    Characteristics of a TLD thermoluminescent kit with LiF detectors of TLD and DTG-4 types (diameters 3.5 and 5 mm) and TLD-400 were compared with those of a kit of IFKU-1 individual photographic film badges. Individual thermoluminescent dosimeters record a total dose of occupational and background irradiation, and film badges--a dose of occupational irradiation only. It should be taken into account in radiation-hygienic interpretation of individual dosimetric control readings. PMID:2761377

  12. Sensitivity of postplanning target and OAR coverage estimates to dosimetric margin distribution sampling parameters

    SciTech Connect

    Xu Huijun; Gordon, J. James; Siebers, Jeffrey V.

    2011-02-15

    Purpose: A dosimetric margin (DM) is the margin in a specified direction between a structure and a specified isodose surface, corresponding to a prescription or tolerance dose. The dosimetric margin distribution (DMD) is the distribution of DMs over all directions. Given a geometric uncertainty model, representing inter- or intrafraction setup uncertainties or internal organ motion, the DMD can be used to calculate coverage Q, which is the probability that a realized target or organ-at-risk (OAR) dose metric D{sub v} exceeds the corresponding prescription or tolerance dose. Postplanning coverage evaluation quantifies the percentage of uncertainties for which target and OAR structures meet their intended dose constraints. The goal of the present work is to evaluate coverage probabilities for 28 prostate treatment plans to determine DMD sampling parameters that ensure adequate accuracy for postplanning coverage estimates. Methods: Normally distributed interfraction setup uncertainties were applied to 28 plans for localized prostate cancer, with prescribed dose of 79.2 Gy and 10 mm clinical target volume to planning target volume (CTV-to-PTV) margins. Using angular or isotropic sampling techniques, dosimetric margins were determined for the CTV, bladder and rectum, assuming shift invariance of the dose distribution. For angular sampling, DMDs were sampled at fixed angular intervals {omega} (e.g., {omega}=1 deg., 2 deg., 5 deg., 10 deg., 20 deg.). Isotropic samples were uniformly distributed on the unit sphere resulting in variable angular increments, but were calculated for the same number of sampling directions as angular DMDs, and accordingly characterized by the effective angular increment {omega}{sub eff}. In each direction, the DM was calculated by moving the structure in radial steps of size {delta}(=0.1,0.2,0.5,1 mm) until the specified isodose was crossed. Coverage estimation accuracy {Delta}Q was quantified as a function of the sampling parameters {omega} or

  13. On the implementation of a recently proposed dosimetric formalism to a robotic radiosurgery system

    SciTech Connect

    Pantelis, E.; Moutsatsos, A.; Zourari, K.; Kilby, W.; Antypas, C.; Papagiannis, P.; Karaiskos, P.; Georgiou, E.; Sakelliou, L.

    2010-05-15

    Purpose: The aim of this work is to implement a recently proposed dosimetric formalism for nonstandard fields to the calibration and small field output factor measurement of a robotic stereotactic radiosurgery system. Methods: Reference dosimetry measurements were performed in the nonstandard, 60 mm diameter machine specific reference (msr) field using a Farmer ion chamber, five other cylindrical chambers with cavity lengths ranging from 16.25 down to 2.7 mm, and alanine dosimeters. Output factor measurements were performed for the 5, 7.5, 10, and 15 mm field sizes using microchambers, diode detectors, alanine dosimeters, TLD microcubes, and EBT Gafchromic films. Measurement correction factors as described in the proposed formalism were calculated for the ion chamber and diode detector output factor measurements based on published Monte Carlo data. Corresponding volume averaging correction factors were calculated for the alanine output factor measurements using 3D dose distributions, measured with polymer gel dosimeters. Results: Farmer chamber and alanine reference dosimetry results were found in close agreement, yielding a correction factor of k{sub Q{sub m{sub s{sub r,Q}{sup f{sub m}{sub s}{sub r},f{sub r}{sub e}{sub f}}}}}=0.999{+-}0.016 for the chamber readings. These results were also found to be in agreement within experimental uncertainties with corresponding results obtained using the shorter cavity length ionization chambers. The mean measured dose values of the latter, however, were found to be consistently greater than that of the Farmer chamber. This finding, combined with an observed inverse relationship between the mean measured dose and chamber cavity length that follows the trend predicted by theoretical volume averaging calculations in the msr field, implies that the Farmer k{sub Q{sub m{sub s{sub r,Q}{sup f{sub m}{sub s}{sub r},f{sub r}{sub e}{sub f}}}}} correction is greater than unity. Regarding the output factor results, deviations as large as

  14. Dosimetric feasibility of intensity modulated proton therapy in a transverse magnetic field of 1.5 T.

    PubMed

    Hartman, J; Kontaxis, C; Bol, G H; Frank, S J; Lagendijk, J J W; van Vulpen, M; Raaymakers, B W

    2015-08-01

    Proton therapy promises higher dose conformality in comparison with regular radiotherapy techniques. Also, image guidance has an increasing role in radiotherapy and MRI is a prime candidate for this imaging. Therefore, in this paper the dosimetric feasibility of Intensity Modulated Proton Therapy (IMPT) in a magnetic field of 1.5 T and the effect on the generated dose distributions compared to those at 0 T is evaluated, using the Monte Carlo software TOol for PArticle Simulation (TOPAS). For three different anatomic sites IMPT plans are generated. It is shown that the generation of an IMPT plan in a magnetic field is feasible, the impact of the magnetic field is small, and the resulting dose distributions are equivalent for 0 T and 1.5 T. Also, the framework of Monte Carlo simulation combined with an inverse optimization method can be used to generate IMPT plans. These plans can be used in future dosimetric comparisons with e.g. IMRT and conventional IMPT. Finally, this study shows that IMPT in a 1.5 T magnetic field is dosimetrically feasible. PMID:26182957

  15. Dosimetric feasibility of intensity modulated proton therapy in a transverse magnetic field of 1.5 T

    NASA Astrophysics Data System (ADS)

    Hartman, J.; Kontaxis, C.; Bol, G. H.; Frank, S. J.; Lagendijk, J. J. W.; van Vulpen, M.; Raaymakers, B. W.

    2015-08-01

    Proton therapy promises higher dose conformality in comparison with regular radiotherapy techniques. Also, image guidance has an increasing role in radiotherapy and MRI is a prime candidate for this imaging. Therefore, in this paper the dosimetric feasibility of Intensity Modulated Proton Therapy (IMPT) in a magnetic field of 1.5 T and the effect on the generated dose distributions compared to those at 0 T is evaluated, using the Monte Carlo software TOol for PArticle Simulation (TOPAS). For three different anatomic sites IMPT plans are generated. It is shown that the generation of an IMPT plan in a magnetic field is feasible, the impact of the magnetic field is small, and the resulting dose distributions are equivalent for 0 T and 1.5 T. Also, the framework of Monte Carlo simulation combined with an inverse optimization method can be used to generate IMPT plans. These plans can be used in future dosimetric comparisons with e.g. IMRT and conventional IMPT. Finally, this study shows that IMPT in a 1.5 T magnetic field is dosimetrically feasible.

  16. Matched-pair analysis and dosimetric variations of two types of software for interstitial permanent brachytherapy for prostate cancer.

    PubMed

    Ishiyama, Hiromichi; Nakamura, Ryuji; Satoh, Takefumi; Tanji, Susumu; Teh, Bin S; Uemae, Mineko; Baba, Shiro; Hayakawa, Kazushige

    2012-01-01

    The purpose of this study was to determine whether identical dosimetric results could be achieved using different planning software for permanent interstitial brachytherapy for prostate cancer. Data from 492 patients treated with brachytherapy were used for matched-pair analysis. Interplant and Variseed were used as software for ultrasound-based treatment planning. Institution, neoadjuvant hormonal therapy, prostate volume, and source strength were used for factors to match the 2 groups. The study population comprised of 126 patients with treatment planning using Interplant software and 127 matched patients using Variseed software. Dosimetric results were compared between the 2 groups. The Variseed group showed significantly higher values for dose covering 90% of prostate volume (pD90), prostate volume covered by 150% of prescription dose (pV150), and dose covering 30% of the urethra (uD30) compared with the Interplant group. Our results showed that use of different software could lead to different dosimetric results, which might affect the clinical outcomes. PMID:21937217

  17. Dosimetric Significance of the ICRP's Updated Guidance and Models, 1989-2003, and Implications for U.S. Federal Guidance

    SciTech Connect

    Leggett, R.W.

    2003-09-10

    Over the past two decades the U.S. Environmental Protection Agency (EPA) has issued a series of Federal guidance documents for the purpose of providing the Federal and State agencies with technical information to assist their implementation of radiation protection programs. Currently recommended dose conversion factors, annual limits on intake, and derived air concentrations for intake of radionuclides are tabulated in Federal Guidance Report No. 11 (FGR 11), published in 1988. The tabulations in FGR 11 were based on dosimetric quantities and biokinetic and dosimetric models of the International Commission on Radiological Protection (ICRP) developed for application to occupational exposures. Since the publication of FGR 11 the ICRP has revised some of its dosimetric quantities and its models for workers and has also developed age-specific models and dose conversion factors for intake of radionuclides by members of the public. This report examines the extent of the changes in the inhalation and ingestion dose coefficients of FGR 11 implied by the updated recommendations of the ICRP, both for workers and members of the public.

  18. Retrospective evaluation of dosimetric quality for prostate carcinomas treated with 3D conformal, intensity modulated and volumetric modulated arc radiotherapy

    SciTech Connect

    Crowe, Scott B; Kairn, Tanya; Middlebrook, Nigel; Hill, Brendan; Christie, David R H; Knight, Richard T; Kenny, John; Langton, Christian M; Trapp, Jamie V

    2013-12-15

    This study examines and compares the dosimetric quality of radiotherapy treatment plans for prostate carcinoma across a cohort of 163 patients treated across five centres: 83 treated with three-dimensional conformal radiotherapy (3DCRT), 33 treated with intensity modulated radiotherapy (IMRT) and 47 treated with volumetric modulated arc therapy (VMAT). Treatment plan quality was evaluated in terms of target dose homogeneity and organs at risk (OAR), through the use of a set of dose metrics. These included the mean, maximum and minimum doses; the homogeneity and conformity indices for the target volumes; and a selection of dose coverage values that were relevant to each OAR. Statistical significance was evaluated using two-tailed Welch's T-tests. The Monte Carlo DICOM ToolKit software was adapted to permit the evaluation of dose metrics from DICOM data exported from a commercial radiotherapy treatment planning system. The 3DCRT treatment plans offered greater planning target volume dose homogeneity than the other two treatment modalities. The IMRT and VMAT plans offered greater dose reduction in the OAR: with increased compliance with recommended OAR dose constraints, compared to conventional 3DCRT treatments. When compared to each other, IMRT and VMAT did not provide significantly different treatment plan quality for like-sized tumour volumes. This study indicates that IMRT and VMAT have provided similar dosimetric quality, which is superior to the dosimetric quality achieved with 3DCRT.

  19. Retrospective evaluation of dosimetric quality for prostate carcinomas treated with 3D conformal, intensity modulated and volumetric modulated arc radiotherapy

    PubMed Central

    Crowe, Scott B; Kairn, Tanya; Middlebrook, Nigel; Hill, Brendan; Christie, David R H; Knight, Richard T; Kenny, John; Langton, Christian M; Trapp, Jamie V

    2013-01-01

    Introduction This study examines and compares the dosimetric quality of radiotherapy treatment plans for prostate carcinoma across a cohort of 163 patients treated across five centres: 83 treated with three-dimensional conformal radiotherapy (3DCRT), 33 treated with intensity modulated radiotherapy (IMRT) and 47 treated with volumetric modulated arc therapy (VMAT). Methods Treatment plan quality was evaluated in terms of target dose homogeneity and organs at risk (OAR), through the use of a set of dose metrics. These included the mean, maximum and minimum doses; the homogeneity and conformity indices for the target volumes; and a selection of dose coverage values that were relevant to each OAR. Statistical significance was evaluated using two-tailed Welch's T-tests. The Monte Carlo DICOM ToolKit software was adapted to permit the evaluation of dose metrics from DICOM data exported from a commercial radiotherapy treatment planning system. Results The 3DCRT treatment plans offered greater planning target volume dose homogeneity than the other two treatment modalities. The IMRT and VMAT plans offered greater dose reduction in the OAR: with increased compliance with recommended OAR dose constraints, compared to conventional 3DCRT treatments. When compared to each other, IMRT and VMAT did not provide significantly different treatment plan quality for like-sized tumour volumes. Conclusions This study indicates that IMRT and VMAT have provided similar dosimetric quality, which is superior to the dosimetric quality achieved with 3DCRT. PMID:26229621

  20. MO-G-17A-04: Internal Dosimetric Calculations for Pediatric Nuclear Imaging Applications, Using Monte Carlo Simulations and High-Resolution Pediatric Computational Models

    SciTech Connect

    Papadimitroulas, P; Kagadis, GC; Loudos, G

    2014-06-15

    Purpose: Our purpose is to evaluate the administered absorbed dose in pediatric, nuclear imaging studies. Monte Carlo simulations with the incorporation of pediatric computational models can serve as reference for the accurate determination of absorbed dose. The procedure of the calculated dosimetric factors is described, while a dataset of reference doses is created. Methods: Realistic simulations were executed using the GATE toolkit and a series of pediatric computational models, developed by the “IT'IS Foundation”. The series of the phantoms used in our work includes 6 models in the range of 5–14 years old (3 boys and 3 girls). Pre-processing techniques were applied to the images, to incorporate the phantoms in GATE simulations. The resolution of the phantoms was set to 2 mm3. The most important organ densities were simulated according to the GATE “Materials Database”. Several used radiopharmaceuticals in SPECT and PET applications are being tested, following the EANM pediatric dosage protocol. The biodistributions of the several isotopes used as activity maps in the simulations, were derived by the literature. Results: Initial results of absorbed dose per organ (mGy) are presented in a 5 years old girl from the whole body exposure to 99mTc - SestaMIBI, 30 minutes after administration. Heart, kidney, liver, ovary, pancreas and brain are the most critical organs, in which the S-factors are calculated. The statistical uncertainty in the simulation procedure was kept lower than 5%. The Sfactors for each target organ are calculated in Gy/(MBq*sec) with highest dose being absorbed in kidneys and pancreas (9.29*10{sup 10} and 0.15*10{sup 10} respectively). Conclusion: An approach for the accurate dosimetry on pediatric models is presented, creating a reference dosage dataset for several radionuclides in children computational models with the advantages of MC techniques. Our study is ongoing, extending our investigation to other reference models and

  1. Dosimetric accuracy of a deterministic radiation transport based {sup 192}Ir brachytherapy treatment planning system. Part III. Comparison to Monte Carlo simulation in voxelized anatomical computational models

    SciTech Connect

    Zourari, K.; Pantelis, E.; Moutsatsos, A.; Sakelliou, L.; Georgiou, E.; Karaiskos, P.; Papagiannis, P.

    2013-01-15

    Purpose: To compare TG43-based and Acuros deterministic radiation transport-based calculations of the BrachyVision treatment planning system (TPS) with corresponding Monte Carlo (MC) simulation results in heterogeneous patient geometries, in order to validate Acuros and quantify the accuracy improvement it marks relative to TG43. Methods: Dosimetric comparisons in the form of isodose lines, percentage dose difference maps, and dose volume histogram results were performed for two voxelized mathematical models resembling an esophageal and a breast brachytherapy patient, as well as an actual breast brachytherapy patient model. The mathematical models were converted to digital imaging and communications in medicine (DICOM) image series for input to the TPS. The MCNP5 v.1.40 general-purpose simulation code input files for each model were prepared using information derived from the corresponding DICOM RT exports from the TPS. Results: Comparisons of MC and TG43 results in all models showed significant differences, as reported previously in the literature and expected from the inability of the TG43 based algorithm to account for heterogeneities and model specific scatter conditions. A close agreement was observed between MC and Acuros results in all models except for a limited number of points that lay in the penumbra of perfectly shaped structures in the esophageal model, or at distances very close to the catheters in all models. Conclusions: Acuros marks a significant dosimetry improvement relative to TG43. The assessment of the clinical significance of this accuracy improvement requires further work. Mathematical patient equivalent models and models prepared from actual patient CT series are useful complementary tools in the methodology outlined in this series of works for the benchmarking of any advanced dose calculation algorithm beyond TG43.

  2. Dosimetric comparison of volumetric modulated arc therapy and intensity-modulated radiation therapy for pancreatic malignancies

    SciTech Connect

    Ali, Arif N.; Dhabaan, Anees H.; Jarrio, Christie S.; Siddiqi, Arsalan K.; Landry, Jerome C.

    2012-10-01

    Volumetric-modulated arc therapy (VMAT) has been previously evaluated for several tumor sites and has been shown to provide significant dosimetric and delivery benefits when compared with intensity-modulated radiation therapy (IMRT). To date, there have been no published full reports on the benefits of VMAT use in pancreatic patients compared with IMRT. Ten patients with pancreatic malignancies treated with either IMRT or VMAT were retrospectively identified. Both a double-arc VMAT and a 7-field IMRT plan were generated for each of the 10 patients using the same defined tumor volumes, organs at risk (OAR) volumes, dose, fractionation, and optimization constraints. The planning tumor volume (PTV) maximum dose (55.8 Gy vs. 54.4 Gy), PTV mean dose (53.9 Gy vs. 52.1 Gy), and conformality index (1.11 vs. 0.99) were statistically similar between the IMRT and VMAT plans, respectively. The VMAT plans had a statistically significant reduction in monitor units compared with the IMRT plans (1109 vs. 498, p < 0.001). In addition, the doses to the liver, small bowel, and spinal cord were comparable between the IMRT and VMAT plans. However, the VMAT plans demonstrated a statistically significant reduction in the mean left kidney V{sub 25} (9.4 Gy vs. 2.3 Gy, p = 0.018), mean right kidney V{sub 15} (53.4 Gy vs. 45.9 Gy, p = 0.035), V{sub 20} (32.2 Gy vs. 25.5 Gy, p = 0.016), and V{sub 25} (21.7 Gy vs. 14.9 Gy, p = 0.001). VMAT was investigated in patients with pancreatic malignancies and compared with the current standard of IMRT. VMAT was found to have similar or improved dosimetric parameters for all endpoints considered. Specifically, VMAT provided reduced monitor units and improved bilateral kidney normal tissue dose. The clinical relevance of these benefits in the context of pancreatic cancer patients, however, is currently unclear and requires further investigation.

  3. Dosimetric effects on small-field beam-modeling for stereotactic body radiation therapy

    NASA Astrophysics Data System (ADS)

    Cho, Woong; Kim, Suzy; Kim, Jung-In; Wu, Hong-Gyun; Jung, Joo-Young; Kim, Min-Joo; Suh, Tae-Suk; Kim, Jin-Young; Kim, Jong Won

    2015-02-01

    The treatment planning of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) requires high accuracy of dosimetric data for small radiation fields. The dosimetric effects on the beam-modeling process of a treatment planning system (TPS) were investigated using different measured small-field data sets. We performed small-field dosimetry with three detectors: a CC13 ion chamber, a CC01 ion chamber, and an edge detector. Percentage depth doses (PDDs) and dose profiles for field sizes given by 3 × 3 cm2, 2 × 2 cm2, and 1 × 1 cm2 were obtained for 6 MV and 15 MV photon beams. Each measured data set was used as data input for a TPS, in which a beam-modeling process was implemented using the collapsed cone convolution (CCC) algorithm for dose calculation. The measured data were used to generate six beam-models based on each combination of detector type and photon energy, which were then used to calculate the corresponding PDDs and dose profiles for various depths and field sizes. Root mean square differences (RMSDs) between the calculated and the measured doses were evaluated for the PDDs and the dose profiles. The RMSDs of PDDs beyond the maximum dose depth were within an accuracy of 0.2-0.6%, being clinically acceptable. The RMSDs of the dose profiles corresponding to the CC13, the CC01, and the edge detector were 2.80%, 1.49%, and 1.46% for a beam energy of 6 MV and 2.34%, 1.15%, and 1.44% for a beam energy of 15 MV, respectively. The calculated results for the CC13 ion chamber showed the most discrepancy compared to the measured data, due to the relatively large sensitive volume of this detector. However, the calculated dose profiles for the detectors were not significantly different from another. The physical algorithm used in the beam-modeling process did not seem to be sensitive to blurred data measured with detectors with large sensitive volumes. Each beam-model was used to clinically evaluate lung and lymphatic node SBRT plans

  4. Dosimetric characteristics of four PTW microDiamond detectors in high-energy proton beams

    NASA Astrophysics Data System (ADS)

    Marsolat, F.; De Marzi, L.; Patriarca, A.; Nauraye, C.; Moignier, C.; Pomorski, M.; Moignau, F.; Heinrich, S.; Tromson, D.; Mazal, A.

    2016-09-01

    Small diamond detectors are useful for the dosimetry of high-energy proton beams. However, linear energy transfer (LET) dependence has been observed in the literature with such solid state detectors. A novel synthetic diamond detector has recently become commercially available from the manufacturer PTW-Freiburg (PTW microDiamond type 60019). This study was designed to thoroughly characterize four microDiamond detectors in clinical proton beams, in order to investigate their response and their reproducibility in high LET regions. Very good dosimetric characteristics were observed for two of them, with good stability of their response (deviation less than 0.4% after a pre-irradiation dose of approximately 12 Gy), good repeatability (coefficient of variation of 0.06%) and a sensitivity of approximately 0.85 nC Gy‑1. A negligible dose rate dependence was also observed for these two microDiamonds with a deviation of the sensitivity less than 0.7% with respect to the one measured at the reference dose rate of 2.17 Gy min‑1, in the investigated dose rate range from 1.01 Gy min‑1 to 5.52 Gy min‑1. Lateral dose profile measurements showed the high spatial resolution of the microDiamond oriented with its stem perpendicular to the beam axis and with its small sensitive thickness of about 1 μm in the scanning profile direction. Finally, no significant LET dependence was found with these two diamond dosimeters in comparison to a reference ionization chamber (model IBA PPC05). These good results were in accordance to the literature. However, this study showed also a non reproducibility between the devices in terms of stability, sensitivity and LET dependence, since the two other microDiamonds characterized in this work showed different dosimetric characteristics making them not suitable for proton beam dosimetry with a maximum difference of the peak-to-plateau ratio of 6.7% relative to the reference ionization chamber in a clinical 138 MeV proton beam.

  5. An evaluation of a novel synthetic diamond probe for dosimetric applications

    NASA Astrophysics Data System (ADS)

    Ade, N.; Nam, T. L.

    2015-10-01

    A study is presented that characterises the dosimetric performances of two synthetic diamond sensors (HP1 and HP2) when either one or both detectors are subjected to clinical beams of various types under large as well as small-field conditions. Detector performances were evaluated using a prototype probe housing constructed of tissue-equivalent materials. The probe can accommodate diamond sensors of various sizes and is configured for radiation detection in different exposure orientations without having first to re-orient the sensor plate within its body. Also, the diamond sensor is aligned in the same configuration as its rectangular housing and the probe is designed to be compatible with commercially available electrometer systems. Dosimetric measurements were conducted using mammography X-rays (25-32 kVp) and megavoltage electron (6-21 MeV) and photon (60Co γ-ray, 6-18 MV X-ray) beams. Whereas HP1 was evaluated using all beam types under large-flied conditions and small-photon-beam fields down to 0.7×0.7 cm2, HP2 was evaluated using small-electron and photon-beam conditions down to 0.3×0.3 cm2 6 MV photon field. Using HP1 sensor, the synthetic diamond probe was found not to require daily pre-irradiation as long as it is properly shielded from ambient light and its response stabilised. Furthermore, the diamond probe exhibited linear response characteristics with absorbed dose and on exposure parameters to various beam types, negligible energy dependence and almost no variation in angular response. Exposing the sensor HP2 under a 0.4×0.4 cm2 6 MV photon radiation field, a sensitivity value of 197.3 nC Gy-1 mm-3 was established compared to a value of 136.1 nC Gy-1 mm-3 obtained with a small-field diode detector. Also, a figure of 5.5×103 for the SNR was established for the sensor in the same radiation field. Relative beam data measured with the diamond sensors were found to agree within 1-2% with data obtained with reference detectors. The presentation

  6. Quantitative dosimetric assessment for effect of gold nanoparticles as contrast media on radiotherapy planning

    NASA Astrophysics Data System (ADS)

    Tu, Shu-Ju; Yang, Pei-Ying; Hong, Ji-Hong; Lo, Ching-Jung

    2013-07-01

    In CT planning for radiation therapy, patients may be asked to have a medical procedure of contrast agent (CA) administration as required by their physicians. CA media improve quality of CT images and assist radiation oncologists in delineation of the target or organs with accuracy. However, dosimetric discrepancy may occur between scenarios in which CA media are present in CT planning and absent in treatment delivery. In recent preclinical experiments of small animals, gold nanoparticles (AuNPs) have been identified as an excellent contrast material of x-ray imaging. In this work, we quantitatively evaluate the effect of AuNPs to be used as a potential material of contrast enhancement in radiotherapy planning with an analytical phantom and clinical case. Conray 60, an iodine-based product for contrast enhancement in clinical uses, is included as a comparison. Other additional variables such as different concentrations of CA media, radiation delivery techniques and dose calculation algorithms are included. We consider 1-field AP, 4-field box, 7-field intensity modulated radiation therapy (IMRT) and a recent technique of volumetric modulated arc therapy (VMAT). CA media of AuNPs (Conray 60) with concentrations of 10%, 20%, 30%, 40% and 50% containing 28.2, 56.4, 84.6, 112.8 and 141.0 mg of gold (iodine) per mL were prepared prior to CT scanning. A virtual phantom with a target where nanoparticle media are loaded and clinical case of gastric lymphoma in which the Conray 60 media were given to the patient prior to the CT planning are included for the study. Compared to Conray 60 media with concentration of 10%/50%, Hounsfield units for AuNP media of 10%/50% are 322/1608 higher due to the fact that atomic number of Au (Z=79) is larger than I (Z=53). In consequence, dosimetric discrepancy of AuNPs is magnified between presence and absence of contrast media. It was found in the phantom study that percent dose differences between presence and absence of CA media may be

  7. The dosimetric impact of dental implants on head-and-neck volumetric modulated arc therapy.

    PubMed

    Lin, Mu-Han; Li, Jinsheng; Price, Robert A; Wang, Lu; Lee, Chung-Chi; Ma, C-M

    2013-02-21

    This work aims to investigate the dosimetric impact of dental implants on volumetric modulated arc therapy (VMAT) for head-and-neck patients and to evaluate the effectiveness of using the material's electron-density ratio for the correction. An in-house Monte Carlo (MC) code was utilized for the dose calculation to account for the scattering and attenuation caused by the high-Z implant material. Three different dental implant materials were studied in this work: titanium, Degubond®4 and gold. The dose perturbations caused by the dental implant materials were first investigated in a water phantom with a 1 cm(3) insert. The per cent depth dose distributions of a 3 × 3 cm(2) photon field were compared with the insert material as water and the three selected dental implant materials. To evaluate the impact of the dental implant on VMAT patient dose calculation, four head-and-neck cases were selected. For each case, the VMAT plan was designed based on the artifact-corrected patient geometry using a treatment planning system (TPS) that was typically utilized for routine patient treatment. The plans were re-calculated using the MC code for five situations: uncorrected geometry, artifact-corrected geometry and artifact-corrected geometry with one of the three different implant materials. The isodose distributions and the dose-volume histograms were cross-compared with each other. To evaluate the effectiveness of using the material's electron-density ratio for dental implant correction, the implant region was set as water with the material's electron-density ratio and the calculated dose was compared with the MC simulation with the real material. The main effect of the dental implant was the severe attenuation in the downstream. The 1 cm(3) dental implant can lower the downstream dose by 10% (Ti) to 51% (Au) for a 3 × 3 cm(2) field. The TPS failed to account for the dose perturbation if the dental implant material was not precisely defined. For the VMAT

  8. Dosimetric feasibility of real-time MRI-guided proton therapy

    SciTech Connect

    Moteabbed, M. Schuemann, J.; Paganetti, H.

    2014-11-01

    Purpose: Magnetic resonance imaging (MRI) is a prime candidate for image-guided radiotherapy. This study was designed to assess the feasibility of real-time MRI-guided proton therapy by quantifying the dosimetric effects induced by the magnetic field in patients’ plans and identifying the associated clinical consequences. Methods: Monte Carlo dose calculation was performed for nine patients of various treatment sites (lung, liver, prostate, brain, skull-base, and spine) and tissue homogeneities, in the presence of 0.5 and 1.5 T magnetic fields. Dose volume histogram (DVH) parameters such as D{sub 95}, D{sub 5}, and V{sub 20} as well as equivalent uniform dose were compared for the target and organs at risk, before and after applying the magnetic field. The authors further assessed whether the plans affected by clinically relevant dose distortions could be corrected independent of the planning system. Results: By comparing the resulting dose distributions and analyzing the respective DVHs, it was determined that despite the observed lateral beam deflection, for magnetic fields of up to 0.5 T, neither was the target coverage jeopardized nor was the dose to the nearby organs increased in all cases except for prostate. However, for a 1.5 T magnetic field, the dose distortions were more pronounced and of clinical concern in all cases except for spine. In such circumstances, the target was severely underdosed, as indicated by a decrease in D{sub 95} of up to 41% of the prescribed dose compared to the nominal situation (no magnetic field). Sites such as liver and spine were less affected due to higher tissue homogeneity, typically smaller beam range, and the choice of beam directions. Simulations revealed that small modifications to certain plan parameters such as beam isocenter (up to 19 mm) and gantry angle (up to 10°) are sufficient to compensate for the magnetic field-induced dose disturbances. The authors’ observations indicate that the degree of required

  9. SU-E-J-165: Dosimetric Impact of Liver Rotations in Stereotactic Body Radiation Therapy

    SciTech Connect

    Pinnaduwage, D; Paulsson, A; Sudhyadhom, A; Chen, J; Chang, A; Anwar, M; Gottschalk, A; Yom, S S.; Descovich, M

    2015-06-15

    Purpose: Often in liver stereotactic body radiotherapy a single fiducial is implanted near the tumor for image-guided treatment delivery. In such cases, rotational corrections are calculated based on the spine. This study quantifies rotational differences between the spine and liver, and investigates the corresponding dosimetric impact. Methods: Seven patients with 3 intrahepatic fiducials and 4DCT scans were identified. The planning CT was separately co-registered with 4 phases of the 4DCT (0%, 50%, 100% inhale and 50% exhale) by 1) rigid registration of the spine, and 2) point-based registration of the 3 fiducials. Rotation vectors were calculated for each registration. Translational differences in fiducial positions between the 2 registrations methods were investigated. Dosimetric impact due to liver rotations and deformations was assessed using critical structures delineated on the 4DCT phases. For dose comparisons, a single fiducial was translationally aligned following spine alignment to represent what is typically done in the clinic. Results: On average, differences between spine and liver rotations during the 0%, 50%, 100% inhale, and 50% exhale phases were 3.23°, 3.27°, 2.26° and 3.11° (pitch), 3.00°, 2.24°, 3.12° and 1.73° (roll), and 1.57°, 1.98°, 2.09° and 1.36° (yaw), respectively. The maximum difference in rotations was 12°, with differences of >3° seen in 14/28 (pitch), 10/28 (roll), and 6/28 (yaw) cases. Average fiducial displacements of 2.73 (craniocaudal), 1.04 (lateral) and 1.82 mm (vertical) were seen. Evaluating percent dose differences for 5 patients at the peaks of the respiratory cycle, the maximum dose to the duodenum, stomach, bowel and esophagus differed on average by 11.4%, 5.3%, 11.2% and 49.1% between the 2 registration methods. Conclusion: Lack of accounting for liver rotation during treatment might Result in clinically significant dose differences to critical structures. Both rotational and translational deviations

  10. SU-E-T-613: Dosimetric Consequences of Systematic MLC Leaf Positioning Errors

    SciTech Connect

    Kathuria, K; Siebers, J

    2014-06-01

    Purpose: The purpose of this study is to determine the dosimetric consequences of systematic MLC leaf positioning errors for clinical IMRT patient plans so as to establish detection tolerances for quality assurance programs. Materials and Methods: Dosimetric consequences were simulated by extracting mlc delivery instructions from the TPS, altering the file by the specified error, reloading the delivery instructions into the TPS, recomputing dose, and extracting dose-volume metrics for one head-andneck and one prostate patient. Machine error was simulated by offsetting MLC leaves in Pinnacle in a systematic way. Three different algorithms were followed for these systematic offsets, and are as follows: a systematic sequential one-leaf offset (one leaf offset in one segment per beam), a systematic uniform one-leaf offset (same one leaf offset per segment per beam) and a systematic offset of a given number of leaves picked uniformly at random from a given number of segments (5 out of 10 total). Dose to the PTV and normal tissue was simulated. Results: A systematic 5 mm offset of 1 leaf for all delivery segments of all beams resulted in a maximum PTV D98 deviation of 1%. Results showed very low dose error in all reasonably possible machine configurations, rare or otherwise, which could be simulated. Very low error in dose to PTV and OARs was shown in all possible cases of one leaf per beam per segment being offset (<1%), or that of only one leaf per beam being offset (<.2%). The errors resulting from a high number of adjacent leaves (maximum of 5 out of 60 total leaf-pairs) being simultaneously offset in many (5) of the control points (total 10–18 in all beams) per beam, in both the PTV and the OARs analyzed, were similarly low (<2–3%). Conclusions: The above results show that patient shifts and anatomical changes are the main source of errors in dose delivered, not machine delivery. These two sources of error are “visually complementary” and uncorrelated

  11. Dosimetric characterization of a microDiamond detector in clinical scanned carbon ion beams

    SciTech Connect

    Marinelli, Marco; Prestopino, G. Verona, C.; Verona-Rinati, G.; Ciocca, M.; Mirandola, A.; Mairani, A.; Raffaele, L.; Magro, G.

    2015-04-15

    Purpose: To investigate for the first time the dosimetric properties of a new commercial synthetic diamond detector (PTW microDiamond) in high-energy scanned clinical carbon ion beams generated by a synchrotron at the CNAO facility. Methods: The detector response was evaluated in a water phantom with actively scanned carbon ion beams ranging from 115 to 380 MeV/u (30–250 mm Bragg peak depth in water). Homogeneous square fields of 3 × 3 and 6 × 6 cm{sup 2} were used. Short- and medium-term (2 months) detector response stability, dependence on beam energy as well as ion type (carbon ions and protons), linearity with dose, and directional and dose-rate dependence were investigated. The depth dose curve of a 280 MeV/u carbon ion beam, scanned over a 3 × 3 cm{sup 2} area, was measured with the microDiamond detector and compared to that measured using a PTW Advanced Markus ionization chamber, and also simulated using FLUKA Monte Carlo code. The detector response in two spread-out-Bragg-peaks (SOBPs), respectively, centered at 9 and 21 cm depths in water and calculated using the treatment planning system (TPS) used at CNAO, was measured. Results: A negligible drift of detector sensitivity within the experimental session was seen, indicating that no detector preirradiation was needed. Short-term response reproducibility around 1% (1 standard deviation) was found. Only 2% maximum variation of microDiamond sensitivity was observed among all the evaluated proton and carbon ion beam energies. The detector response showed a good linear behavior. Detector sensitivity was found to be dose-rate independent, with a variation below 1.3% in the evaluated dose-rate range. A very good agreement between measured and simulated Bragg curves with both microDiamond and Advanced Markus chamber was found, showing a negligible LET dependence of the tested detector. A depth dose curve was also measured by positioning the microDiamond with its main axis oriented orthogonally to the beam

  12. Palliative radiotherapy for thoracic spine metastases: Dosimetric advantage of three-dimensional conformal plans

    PubMed Central

    YEO, SEUNG-GU

    2015-01-01

    The aim of the present study was to investigate the dosimetric advantages of three-dimensional conformal radiation therapy (3DCRT) for thoracic spine metastases and compare it with conventional two-dimensional (2D) plans. Radiation therapy (RT) planning data of 10 patients with mid-to-low thoracic spine metastases were analyzed. Computed tomography simulation was performed and the planning target volume (PTV), heart, esophagus, lung and spinal cord were contoured. The 3DCRT plan comprised one posteroanterior (PA) field and two posterior oblique fields. The 2D plans used a single PA field or opposed anteroposterior (AP)/PA fields. The prescription dose of radiation was 30 Gy in 10 fractions. All comparisons of the maximum or mean doses to the organs at risk or the PTV, between two of the three RT plans, demonstrated statistically significant differences (P<0.05), with the exception of the mean esophageal doses between the single PA vs. AP/PA (P=0.285) plans. The mean heart doses were 15.0±3.1 Gy in single PA, 17.3±4.3 Gy in AP/PA and 8.5±1.7 Gy using 3DCRT. The median reduction rates using 3DCRT were 38.9% compared with single PA (range, 29.4–58.5%) or 47.5% relative to AP/PA (range, 34.5–67.1%). The mean esophageal doses were 17.9±2.3 Gy in single PA, 18.2±2.2 Gy in AP/PA and 15.3±1.9 Gy in 3DCRT. The median reduction rate using 3DCRT was 12.8% compared with single PA or 15.6% relative to AP/PA. Compared with the single PA or AP/PA 2D plan, 3DCRT reduced the median dose by 13.7 or 1.9% of the maximum spinal cord dose, respectively, and 14.7 or 2.9% of the maximum PTV dose, respectively. The mean lung doses were 2.7±0.7 Gy in single PA, 2.6±0.7 Gy in AP/PA and 5.1±1.0 Gy in 3DCRT. In conclusion, 3DCRT for mid-to-low thoracic spine metastases demonstrated significant dosimetric advantages by reducing the unnecessary irradiation of critical organs, particularly the heart, and by achieving a homogeneous target dose. PMID:26171058

  13. Dosimetric feasibility of real-time MRI-guided proton therapy

    PubMed Central

    Moteabbed, M.; Schuemann, J.; Paganetti, H.

    2014-01-01

    Purpose: Magnetic resonance imaging (MRI) is a prime candidate for image-guided radiotherapy. This study was designed to assess the feasibility of real-time MRI-guided proton therapy by quantifying the dosimetric effects induced by the magnetic field in patients’ plans and identifying the associated clinical consequences. Methods: Monte Carlo dose calculation was performed for nine patients of various treatment sites (lung, liver, prostate, brain, skull-base, and spine) and tissue homogeneities, in the presence of 0.5 and 1.5 T magnetic fields. Dose volume histogram (DVH) parameters such as D95, D5, and V20 as well as equivalent uniform dose were compared for the target and organs at risk, before and after applying the magnetic field. The authors further assessed whether the plans affected by clinically relevant dose distortions could be corrected independent of the planning system. Results: By comparing the resulting dose distributions and analyzing the respective DVHs, it was determined that despite the observed lateral beam deflection, for magnetic fields of up to 0.5 T, neither was the target coverage jeopardized nor was the dose to the nearby organs increased in all cases except for prostate. However, for a 1.5 T magnetic field, the dose distortions were more pronounced and of clinical concern in all cases except for spine. In such circumstances, the target was severely underdosed, as indicated by a decrease in D95 of up to 41% of the prescribed dose compared to the nominal situation (no magnetic field). Sites such as liver and spine were less affected due to higher tissue homogeneity, typically smaller beam range, and the choice of beam directions. Simulations revealed that small modifications to certain plan parameters such as beam isocenter (up to 19 mm) and gantry angle (up to 10°) are sufficient to compensate for the magnetic field-induced dose disturbances. The authors’ observations indicate that the degree of required corrections strongly depends

  14. Dosimetric Predictors of Radiation-induced Acute Nausea and Vomiting in IMRT for Nasopharyngeal Cancer

    SciTech Connect

    Lee, Victor H.F.; Ng, Sherry C.Y.; Leung, T.W.; Au, Gordon K.H.; Kwong, Dora L.W.

    2012-09-01

    Purpose: We wanted to investigate dosimetric parameters that would predict radiation-induced acute nausea and vomiting in intensity-modulated radiation therapy (IMRT) for undifferentiated carcinoma of the nasopharynx (NPC). Methods and Materials: Forty-nine consecutive patients with newly diagnosed NPC were treated with IMRT alone in this prospective study. Patients receiving any form of chemotherapy were excluded. The dorsal vagal complex (DVC) as well as the left and right vestibules (VB-L and VB-R, respectively) were contoured on planning computed tomography images. A structure combining both the VB-L and the VB-R, named VB-T, was also generated. All structures were labeled organs at risk (OAR). A 3-mm three-dimensional margin was added to these structures and labeled DVC+3 mm, VB-L+3 mm, VB-R+3 mm, and VB-T+3 mm to account for physiological body motion and setup error. No weightings were given to these structures during optimization in treatment planning. Dosimetric parameters were recorded from dose-volume histograms. Statistical analysis of parameters' association with nausea and vomiting was performed using univariate and multivariate logistic regression. Results: Six patients (12.2%) reported Grade 1 nausea, and 8 patients (16.3%) reported Grade 2 nausea. Also, 4 patients (8.2%) complained of Grade 1 vomiting, and 4 patients (8.2%) experienced Grade 2 vomiting. No patients developed protracted nausea and vomiting after completion of IMRT. For radiation-induced acute nausea, V40 (percentage volume receiving at least 40Gy) to the VB-T and V40>=80% to the VB-T were predictors, using univariate analysis. On multivariate analysis, V40>=80% to the VB-T was the only predictor. There were no predictors of radiation-induced acute vomiting, as the number of events was too small for analysis. Conclusions: This is the first study demonstrating that a V40 to the VB-T is predictive of radiation-induced acute nausea. The vestibules should be labeled as sensitive OARs, and

  15. Cranio Spinal Irradiation of Medulloblastoma Using High Precision Techniques - A Dosimetric Comparison.

    PubMed

    Pichandi, A; Ganesh, K M; Jerrin, A; Balaji, K; Sridhar, P S; Surega, A

    2015-08-01

    Radiotherapy planning, delivery and junction dose verification remain exigent for Cranio Spinal Irradiation (CSI) in medulloblastoma patients. This study aims to evaluate high precision techniques such as Intensity Modulated Radiation Therapy (IMRT), Rapid Arc Therapy (RA) with and without flattening filter (FF) on the basis of dosimetric analysis. Five patients treated with jagged junction Intensity Modulated RadioTherapy (IMRT) using dynamic Multi Leaf Collimators (MLC) were randomly selected for this retrospective study. IMRT, Rapid Arc (RA) plans were simulated in the same CT data set with and without flattening filter. Total dose prescribed was 28.80 Gy in 16 fractions. An evaluation criterion of 98% of PTV receiving 100% of the prescription dose was followed in all plans. Twenty treatment plans with 260 Dose Volume Histograms (DVHs) was created. Dosimetric parameters such as Dmax, Dmin, Dmean, V95%, V107%, CI for PTV and Dmax, Dmean, V80%, V50%, V30%, V10% for Organs At Risk (OAR) were extracted from DVHs. Treatment delivery efficiency was also evaluated for total Beam On Time (BOT). FFF Rapid Arc therapy : 6F_RA) resulted in conformal doses throughout the cranio spinal axis. FF and FFF dynamic IMRT had minimal V107%, 1.23% and 2.88% compared to 49.15 and 66.36 of rapid arc therapy (with and without FF). 6F_IMRT resulted in lesser mean doses to eyes, liver, lungs and kidneys. Heart mean dose was less (3.08 Gy) with 6X_IMRT. Thyroid and esophagus doses could be reduced to about 41.2% and 10% respectively with 6F_RA. The BOT for the treatment techniques were 3.43 min (6X_IMRT), 1.59 min (6F_IMRT), 5min (6X_RA), 4.5 min (6F_RA). Removal of flattening filter in IMRT could improve dose coverage along the caniospinal axis and normal tissue sparing. A reduction of 46.3% BOT could increase treatment efficiency of 6F_IMRT compared to 6X_IMRT. CSI could be simpler since junction doses can be evaded in IMRT and RA techniques. PMID:26269611

  16. Effect of endorectal balloon positioning errors on target deformation and dosimetric quality during prostate SBRT

    NASA Astrophysics Data System (ADS)

    Jones, Bernard L.; Gan, Gregory; Kavanagh, Brian; Miften, Moyed

    2013-11-01

    An inflatable endorectal balloon (ERB) is often used during stereotactic body radiation therapy (SBRT) for treatment of prostate cancer in order to reduce both intrafraction motion of the target and risk of rectal toxicity. However, the ERB can exert significant force on the prostate, and this work assessed the impact of ERB position errors on deformation of the prostate and treatment dose metrics. Seventy-one cone-beam computed tomography (CBCT) image datasets of nine patients with clinical stage T1cN0M0 prostate cancer were studied. An ERB (Flexi-Cuff, EZ-EM, Westbury, NY) inflated with 60 cm3 of air was used during simulation and treatment, and daily kilovoltage (kV) CBCT imaging was performed to localize the prostate. The shape of the ERB in each CBCT was analyzed to determine errors in position, size, and shape. A deformable registration algorithm was used to track the dose received by (and deformation of) the prostate, and dosimetric values such as D95, PTV coverage, and Dice coefficient for the prostate were calculated. The average balloon position error was 0.5 cm in the inferior direction, with errors ranging from 2 cm inferiorly to 1 cm superiorly. The prostate was deformed primarily in the AP direction, and tilted primarily in the anterior-posterior/superior-inferior plane. A significant correlation was seen between errors in depth of ERB insertion (DOI) and mean voxel-wise deformation, prostate tilt, Dice coefficient, and planning-to-treatment prostate inter-surface distance (p < 0.001). Dosimetrically, DOI is negatively correlated with prostate D95 and PTV coverage (p < 0.001). For the model of ERB studied, error in ERB position can cause deformations in the prostate that negatively affect treatment, and this additional aspect of setup error should be considered when ERBs are used for prostate SBRT. Before treatment, the ERB position should be verified, and the ERB should be adjusted if the error is observed to exceed tolerable values.

  17. TG-43 U1 based dosimetric characterization of model 67-6520 Cs-137 brachytherapy source

    SciTech Connect

    Meigooni, Ali S.; Wright, Clarissa; Koona, Rafiq A.; Awan, Shahid B.; Granero, Domingo; Perez-Calatayud, Jose; Ballester, Facundo

    2009-10-15

    Purpose: Brachytherapy treatment has been a cornerstone for management of various cancer sites, particularly for the treatment of gynecological malignancies. In low dose rate brachytherapy treatments, {sup 137}Cs sources have been used for several decades. A new {sup 137}Cs source design has been introduced (model 67-6520, source B3-561) by Isotope Products Laboratories (IPL) for clinical application. The goal of the present work is to implement the TG-43 U1 protocol in the characterization of the aforementioned {sup 137}Cs source. Methods: The dosimetric characteristics of the IPL {sup 137}Cs source are measured using LiF thermoluminescent dosimeters in a Solid Water phantom material and calculated using Monte Carlo simulations with the GEANT4 code in Solid Water and liquid water. The dose rate constant, radial dose function, and two-dimensional anisotropy function of this source model were obtained following the TG-43 U1 recommendations. In addition, the primary and scatter dose separation (PSS) formalism that could be used in convolution/superposition methods to calculate dose distributions around brachytherapy sources in heterogeneous media was studied. Results: The measured and calculated dose rate constants of the IPL {sup 137}Cs source in Solid Water were found to be 0.930({+-}7.3%) and 0.928({+-}2.6%) cGy h{sup -1} U{sup -1}, respectively. The agreement between these two methods was within our experimental uncertainties. The Monte Carlo calculated value in liquid water of the dose rate constant was {Lambda}=0.948({+-}2.6%) cGy h{sup -1} U{sup -1}. Similarly, the agreement between measured and calculated radial dose functions and the anisotropy functions was found to be within {+-}5%. In addition, the tabulated data that are required to characterize the source using the PSS formalism were derived. Conclusions: In this article the complete dosimetry of the newly designed {sup 137}Cs IPL source following the AAPM TG-43 U1 dosimetric protocol and the PSS

  18. Does prior transurethral resection of prostate compromise brachytherapy quality: A dosimetric analysis

    SciTech Connect

    Cesaretti, Jamie A. . E-mail: Jamie.Cesaretti@msnyuhealth.org; Stone, Nelson N.; Stock, Richard G.

    2004-10-01

    Purpose: To evaluate, in a retrospective review, prostate brachytherapy dosimetry outcomes relative to the transurethral resection of the prostate (TURP) cavity size to address the theoretical concern that an intraprostatic cavity may hinder adequate radioactive source placement. Methods and materials: A total of 73 patients who underwent prostate brachytherapy as part of their treatment of localized prostate cancer had a history of a prior TURP. Of these 73 patients, 37 underwent {sup 125}I implantation, 19 {sup 103}Pd implantation, and 17 partial {sup 103}Pd implantation. The dose was calculated using the dose to 90% of the prostate gland (D{sub 90}) from the 1-month post-implant dosimetric analysis. The doses were normalized relative to 100% of the prescription dose. Archived transrectal ultrasound images were used to determine the maximal length and width of the visible residual TURP cavities. The prolate spheroid or symmetric egg shape was used to calculate each residual cavity volume. The derived volume of the TURP cavity was divided by the measured ultrasound volume of the prostate at brachytherapy, creating a percentage of volume measurement for each prostate. All p values, unless otherwise specified, were generated by comparing patients without a visible TURP defect with the subgroups of patients with a visible defect using the Student t test. Results: A visible residual TURP defect was noted on the operative transrectal ultrasound images of 55 (75%) of the 73 patients with a history of TURP before brachytherapy. The 18 patients without a visible TURP defect had a median D{sub 90} of 96% and were used for subsequent statistical comparison. Thirty-six patients with a TURP defect <10% of the entire prostate volume had a median D{sub 90} of 109% (p = 0.02). Thirteen patients with a TURP defect between 10% and 20% of the prostate volume had a median D{sub 90} of 112% (p = 0.03). Six patients with a TURP defect >20% of the prostate volume had a D{sub 90} of 89

  19. Dosimetric Comparison Between 3-Dimensional Conformal and Robotic SBRT Treatment Plans for Accelerated Partial Breast Radiotherapy.

    PubMed

    Goggin, L M; Descovich, M; McGuinness, C; Shiao, S; Pouliot, J; Park, C

    2016-06-01

    Accelerated partial breast irradiation is an attractive alternative to conventional whole breast radiotherapy for selected patients. Recently, CyberKnife has emerged as a possible alternative to conventional techniques for accelerated partial breast irradiation. In this retrospective study, we present a dosimetric comparison between 3-dimensional conformal radiotherapy plans and CyberKnife plans using circular (Iris) and multi-leaf collimators. Nine patients who had undergone breast-conserving surgery followed by whole breast radiation were included in this retrospective study. The CyberKnife planning target volume (PTV) was defined as the lumpectomy cavity + 10 mm + 2 mm with prescription dose of 30 Gy in 5 fractions. Two sets of 3-dimensional conformal radiotherapy plans were created, one used the same definitions as described for CyberKnife and the second used the RTOG-0413 definition of the PTV: lumpectomy cavity + 15 mm + 10 mm with prescription dose of 38.5 Gy in 10 fractions. Using both PTV definitions allowed us to compare the dose delivery capabilities of each technology and to evaluate the advantage of CyberKnife tracking. For the dosimetric comparison using the same PTV margins, CyberKnife and 3-dimensional plans resulted in similar tumor coverage and dose to critical structures, with the exception of the lung V5%, which was significantly smaller for 3-dimensional conformal radiotherapy, 6.2% when compared to 39.4% for CyberKnife-Iris and 17.9% for CyberKnife-multi-leaf collimator. When the inability of 3-dimensional conformal radiotherapy to track motion is considered, the result increased to 25.6%. Both CyberKnife-Iris and CyberKnife-multi-leaf collimator plans demonstrated significantly lower average ipsilateral breast V50% (25.5% and 24.2%, respectively) than 3-dimensional conformal radiotherapy (56.2%). The CyberKnife plans were more conformal but less homogeneous than the 3-dimensional conformal radiotherapy plans. Approximately 50% shorter

  20. Predictive dosimetric parameters for gastrointestinal toxicity with hypofractioned radiotherapy in pancreatic adenocarcinoma

    PubMed Central

    Liu, Xian; Ren, Gang; Li, Liqin; Xia, Tingyi

    2016-01-01

    To better guide the development and optimization of radiotherapy planning, to reduce the incidence of radiation reactions, and to improve the quality of life of the patients with pancreatic cancer using radiotherapy, we conducted this study to explore the dosimetric parameters that predict the risk of gastrointestinal (GI) toxicity with hypofractioned radiotherapy for pancreatic cancer. Between January 2014 and January 2015, the medical records of 68 patients with pancreatic cancer who underwent helical tomotherapy at the Air Force General Hospital were analyzed. The doses delivered to the planning target volume, clinical target volume, and gross tumor volume–internal gross tumor volume of the primary pancreatic lesions were 50, 60, and 70–80 Gy in 15–20 fractions, respectively. GI toxicity was scored according to version 4.0 of the National Cancer Institute Common Terminology Criteria for Adverse Events. The stomach and duodenum were contoured separately to determine the dose–volume histogram parameters. Univariate and multivariate analyses were adopted to identify clinical and physical risk factors associated with GI toxicity. The median follow-up was 9 months (range: 4–16 months). Eighteen patients had grade II acute GI toxicity, one patient had grade III acute GI toxicity, 17 patients had grade II late GI toxicity, and one patient had grade III late GI toxicity. On univariate analysis, the volume, the average dose Dmean, the maximum dose to 1, 3, 5, and 10 cm3 of the stomach and duodenum (D1, D3, D5, and D10), and the relative volumes receiving 5–40 Gy (V5–V40), and the absolute volumes receiving 5–45 Gy (aV5–aV45) of the duodenum were significantly associated with grade II or higher GI toxicity (P<0.05). On multivariate analysis, aV45 of the duodenum was an independent predictor for grade II or higher GI toxicity (P=0.031). The receiver operating characteristic analysis also showed that an aV45 of 0.5 cm3 was the optimal threshold to predict

  1. The dosimetric impact of dental implants on head-and-neck volumetric modulated arc therapy

    NASA Astrophysics Data System (ADS)

    Lin, Mu-Han; Li, Jinsheng; Price, Robert A., Jr.; Wang, Lu; Lee, Chung-Chi; Ma, C.-M.

    2013-02-01

    This work aims to investigate the dosimetric impact of dental implants on volumetric modulated arc therapy (VMAT) for head-and-neck patients and to evaluate the effectiveness of using the material's electron-density ratio for the correction. An in-house Monte Carlo (MC) code was utilized for the dose calculation to account for the scattering and attenuation caused by the high-Z implant material. Three different dental implant materials were studied in this work: titanium, Degubond®4 and gold. The dose perturbations caused by the dental implant materials were first investigated in a water phantom with a 1 cm3 insert. The per cent depth dose distributions of a 3 × 3 cm2 photon field were compared with the insert material as water and the three selected dental implant materials. To evaluate the impact of the dental implant on VMAT patient dose calculation, four head-and-neck cases were selected. For each case, the VMAT plan was designed based on the artifact-corrected patient geometry using a treatment planning system (TPS) that was typically utilized for routine patient treatment. The plans were re-calculated using the MC code for five situations: uncorrected geometry, artifact-corrected geometry and artifact-corrected geometry with one of the three different implant materials. The isodose distributions and the dose-volume histograms were cross-compared with each other. To evaluate the effectiveness of using the material's electron-density ratio for dental implant correction, the implant region was set as water with the material's electron-density ratio and the calculated dose was compared with the MC simulation with the real material. The main effect of the dental implant was the severe attenuation in the downstream. The 1 cm3 dental implant can lower the downstream dose by 10% (Ti) to 51% (Au) for a 3 × 3 cm2 field. The TPS failed to account for the dose perturbation if the dental implant material was not precisely defined. For the VMAT patient dose calculation

  2. Dosimetric characteristics of four PTW microDiamond detectors in high-energy proton beams.

    PubMed

    Marsolat, F; De Marzi, L; Patriarca, A; Nauraye, C; Moignier, C; Pomorski, M; Moignau, F; Heinrich, S; Tromson, D; Mazal, A

    2016-09-01

    Small diamond detectors are useful for the dosimetry of high-energy proton beams. However, linear energy transfer (LET) dependence has been observed in the literature with such solid state detectors. A novel synthetic diamond detector has recently become commercially available from the manufacturer PTW-Freiburg (PTW microDiamond type 60019). This study was designed to thoroughly characterize four microDiamond detectors in clinical proton beams, in order to investigate their response and their reproducibility in high LET regions. Very good dosimetric characteristics were observed for two of them, with good stability of their response (deviation less than 0.4% after a pre-irradiation dose of approximately 12 Gy), good repeatability (coefficient of variation of 0.06%) and a sensitivity of approximately 0.85 nC Gy(-1). A negligible dose rate dependence was also observed for these two microDiamonds with a deviation of the sensitivity less than 0.7% with respect to the one measured at the reference dose rate of 2.17 Gy min(-1), in the investigated dose rate range from 1.01 Gy min(-1) to 5.52 Gy min(-1). Lateral dose profile measurements showed the high spatial resolution of the microDiamond oriented with its stem perpendicular to the beam axis and with its small sensitive thickness of about 1 μm in the scanning profile direction. Finally, no significant LET dependence was found with these two diamond dosimeters in comparison to a reference ionization chamber (model IBA PPC05). These good results were in accordance to the literature. However, this study showed also a non reproducibility between the devices in terms of stability, sensitivity and LET dependence, since the two other microDiamonds characterized in this work showed different dosimetric characteristics making them not suitable for proton beam dosimetry with a maximum difference of the peak-to-plateau ratio of 6.7% relative to the reference ionization chamber in a clinical 138 MeV proton beam. PMID:27499356

  3. Mapping the Future of Map Librarianship.

    ERIC Educational Resources Information Center

    Lang, Laura

    1992-01-01

    Discussion of electronic versions of maps focuses on TIGER files (i.e., electronic maps distributed by the U.S. Bureau of the Census) and their manipulation using geographic information system (GIS) technology. Topics addressed include applications of GIS software, projects to improve access to TIGER files, and the role of GIS in libraries. (MES)

  4. Density Equalizing Map Projections

    SciTech Connect

    Close, E. R.; Merrill, D. W.; Holmes, H. H.

    1995-07-01

    A geographic map is mathematically transformed so that the subareas of the map are proportional to a given quantity such as population. In other words, population density is equalized over the entire map. The transformed map can be used as a display tool, or it can be statistically analyzed. For example, cases of disease plotted on the transformed map should be uniformly distributed at random, if disease rates are everywhere equal. Geographic clusters of disease can be readily identified, and their statistical significance determined, on a density equalized map.

  5. Density Equalizing Map Projections

    1995-07-01

    A geographic map is mathematically transformed so that the subareas of the map are proportional to a given quantity such as population. In other words, population density is equalized over the entire map. The transformed map can be used as a display tool, or it can be statistically analyzed. For example, cases of disease plotted on the transformed map should be uniformly distributed at random, if disease rates are everywhere equal. Geographic clusters of diseasemore » can be readily identified, and their statistical significance determined, on a density equalized map.« less

  6. Riparian Wetlands: Mapping

    EPA Science Inventory

    Riparian wetlands are critical systems that perform functions and provide services disproportionate to their extent in the landscape. Mapping wetlands allows for better planning, management, and modeling, but riparian wetlands present several challenges to effective mapping due t...

  7. Active Fire Mapping Program

    MedlinePlus

    ... Incidents (Home) New Large Incidents Fire Detection Maps MODIS Satellite Imagery VIIRS Satellite Imagery Fire Detection GIS ... Data Web Services Latest Detected Fire Activity Other MODIS Products Frequently Asked Questions About Active Fire Maps ...

  8. Information-Mapped Chemistry.

    ERIC Educational Resources Information Center

    Olympia, P. L., Jr.

    1979-01-01

    This paper describes the use of information mapping in chemistry and in other related sciences. Information mapping is a way of presenting information without paragraphs and unnecessary transitional phrases. (BB)

  9. Linkage map integration

    SciTech Connect

    Collins, A.; Teague, J.; Morton, N.E.; Keats, B.J.

    1996-08-15

    The algorithms that drive the map+ program for locus-oriented linkage mapping are presented. They depend on the enhanced location database program ldb+ to specify an initial comprehensive map that includes all loci in the summary lod file. Subsequently the map may be edited or order constrained and is automatically improved by estimating the location of each locus conditional on the remainder, beginning with the most discrepant loci. Operating characteristics permit rapid and accurate construction of linkage maps with several hundred loci. The map+ program also performs nondisjunction mapping with tests of nonstandard recombination. We have released map+ on Internet as a source program in the C language together with the location database that now includes the LODSOURCE database. 28 refs., 5 tabs.

  10. Creative Concept Mapping.

    ERIC Educational Resources Information Center

    Brown, David S.

    2002-01-01

    Recommends the use of concept mapping in science teaching and proposes that it be presented as a creative activity. Includes a sample lesson plan of a potato stamp concept mapping activity for astronomy. (DDR)

  11. Using maps in genealogy

    USGS Publications Warehouse

    U.S. Geological Survey

    1994-01-01

    In genealogy, maps are most often used as clues to where public or other records about an ancestor are likely to be found. Searching for maps seldom begins until a newcomer to genealogy has mastered basic genealogical routines

  12. Potential application of metal nanoparticles for dosimetric systems: Concepts and perspectives

    SciTech Connect

    Guidelli, Eder José Baffa, Oswaldo

    2014-11-07

    Metallic nanoparticles increase the delivered dose and consequently enhance tissue radio sensitization during radiation therapy of cancer. The Dose Enhancement Factor (DEF) corresponds to the ratio between the dose deposited on a tissue containing nanoparticles, and the dose deposited on a tissue without nanoparticles. In this sense, we have used electron spin resonance spectroscopy (ESR) to investigate how silver and gold nanoparticles affect the dose deposition in alanine dosimeters, which act as a surrogate of soft tissue. Besides optimizing radiation absorption by the dosimeter, the optical properties of these metal nanoparticles could also improve light emission from materials employed as radiation detectors. Therefore, we have also examined how the plasmonic properties of noble metal nanoparticles could enhance radiation detection using optically stimulated luminescence (OSL) dosimetry. This work will show results on how the use of gold and silver nanoparticles are beneficial for the ESR and OSL dosimetric techniques, and will describe the difficulties we have been facing, the challenges to overcome, and the perspectives.

  13. Dosimetric properties of dysprosium doped lithium borate glass irradiated by 6 MV photons

    NASA Astrophysics Data System (ADS)

    Ab Rasid, A.; Wagiran, H.; Hashim, S.; Ibrahim, Z.; Ali, H.

    2015-07-01

    Undoped and dysprosium doped lithium borate glass system with empirical formula (70-x) B2O3-30 Li2O-(x) Dy2O3 (x=0.1, 0.3, 0.5, 0.7, 1.0 mol%) were prepared using the melt-quenching technique. The dosimetric measurements were performed by irradiating the samples to 6 MV photon beam using linear accelerator (LINAC) over a dose range of 0.5-5.0 Gy. The glass series of dysprosium doped lithium borate glass produced the best thermoluminescence (TL) glow curve with the highest intensity peak from sample with 1.0 mol% Dy2O3 concentration. Minimum detectable dose was detected at 2.24 mGy, good linearity of regression coefficient, high reproducibility and high sensitivity compared to the undoped glass are from 1.0 mol% dysprosium doped lithium borate glass. The results indicated that the series of dysprosium doped lithium glasses have a great potential to be considered as a thermoluminescence dosimetry (TLD).

  14. Calibration of laser tomography as a new optical diagnostic tool applied to dosimetric polymer gels

    NASA Astrophysics Data System (ADS)

    Alwan, R.; Guermeur, F.; Bailly, Y.; Simonin, L.; Svoboda, J.; Makovicka, L.; Martin, E.

    2008-03-01

    Numerous medical applications, as radiotherapy for example, require accurate and reproducible three-dimensional dose measurements with high spatial resolution. A solution of great interest and which has been exploited for many years is the use of dosimetric gels based on different physico-chemical principles, as Fricke's gels or polymer gels. Fricke's gels take advantage of the oxidation of ferrous ions in ferric while polymer gels are the result of the synthesis of polyacrylamide hydrogel from monomer and cross-linking agent. Fricke's gels have particular limitations not encountered with polymer gel dosimeters: the time delay between irradiation and measurement must be reduced in order to limit the diffusion of ferric ions which may remove the spatial dose information. That's why, during the past decade, many compositions of polymer gels have been studied (PAG, MAGIC, …), elaborated and even commercialized (BANG gels). However the gel composition remains of great interest regarding its physical properties. In this work, the authors propose a new optical diagnostic tool more flexible and less expensive in comparison with existing techniques like magnetic resonance imaging (MRI) and Optical-CT. This technique is based on light scattering behaviour occurring in an irradiated polymer gel (note that light scattering in Fricke's gels is very feeble, the latter being essentially absorbant).

  15. Cellular uptake of {sup 212}BiOCl by Ehrlich ascites cells: A dosimetric analysis

    SciTech Connect

    Roeske, J.C.; Whitlock, J.L.; Harper, P.V.; Rotmensch, J.; Stinchcomb, T.G.; Schwartz, J.L.; Hines, J.J.

    1999-01-01

    Bi-212 is an alpha-emitting radionuclide being investigated as a therapeutic agent in the intraperitoneal treatment of micrometastatic ovarian carcinoma. In evaluating a new therapeutic modality, cell-survival studies are often used as a means of quantifying the biological effects of radiation. In this analysis, Ehrlich ascites cells were irradiated under conditions similar to therapy in various concentrations of Bi-212. Immediately following irradiation, a cell survival assay was performed in which cells were plated and colonies were counted after 10--14 days. Both a macrodosimetric and a microdosimetric approach were used in analyzing these data. These models used as input the fraction of activity within the cell and in solution, the distribution of cell sizes, and the variation of LET along individual alpha-particle tracks. The results indicate that the energy deposited within the nucleus varies significantly among individual cells. There is a small fraction of cell nuclei which receive no hits, while the remaining cells receive energy depositions which can differ significantly from the mean value. These dosimetric parameters are correlated with measured cell survival and will be a useful predictor of outcome for therapeutic doses.

  16. Topological detector: measuring continuous dosimetric quantities with few-element detector array

    NASA Astrophysics Data System (ADS)

    Han, Zhaohui; Brivio, Davide; Sajo, Erno; Zygmanski, Piotr

    2016-08-01

    A prototype topological detector was fabricated and investigated for quality assurance of radiation producing medical devices. Unlike a typical array or flat panel detector, a topological detector, while capable of achieving a very high spatial resolution, consists of only a few elements and therefore is much simpler in construction and more cost effective. The key feature allowing this advancement is a geometry-driven design that is customized for a specific dosimetric application. In the current work, a topological detector of two elements was examined for the positioning verification of the radiation collimating devices (jaws, MLCs, and blades etc). The detector was diagonally segmented from a rectangular thin film strip (2.5 cm  ×  15 cm), giving two contiguous but independent detector elements. The segmented area was the central portion of the strip measuring 5 cm in length. Under irradiation, signals from each detector element were separately digitized using a commercial multichannel data acquisition system. The center and size of an x-ray field, which were uniquely determined by the collimator positions, were shown mathematically to relate to the difference and sum of the two signals. As a proof of concept, experiments were carried out using slit x-ray fields ranging from 2 mm to 20 mm in size. It was demonstrated that, the collimator positions can be accurately measured with sub-millimeter precisions.

  17. SU-E-T-237: Monte Carlo Dosimetric Characterization of the Mobetron Mobile Linac

    SciTech Connect

    Garcia, F; Granero, D; Vijande, J; Ballester, F; Perez-Calatayud, J

    2014-06-01

    Purpose: The aim of this work is to characterize dosimetrically a clinical intraoperative electron beam accelerator, Mobetron (IntraOp Medical, Inc.) in clinical use in our Hospital. Once this first step is completed our purpose is to evaluate shielding requirements for such a device by preparing adequate phase space files. Methods: It is known that electron beam simulation parameters required for state-of-the-art Monte Carlo codes to obtain a good match with measured data, like the mean energy or the FWHM, may not be code-independent due to the different set of process simulated and formalisms involved. Then, to cross-check our results against any issue in the simulation we have compared experimental data (PDD and profiles for electrons in the range 4 to 12 MeV) with simulations performed independently using both Penelope2011 and Geant4 codes. To do so, the geometry and materials of the head of the accelerator have been fully characterized following information provided by the manufacturer. Results: Both simulations agree with experimental data within experimental uncertainties (±1 mm displacement), although small variations (less than 10%) in the mean energy and FWHM are required to match measured values depending on the code used. Conclusion: Independent Monte Carlo simulations were used to obtain an excellent match to measured electron dose distributions. This opens the road to use such data for evaluating shielding requirements which is the main objective of this project.

  18. Dosimetric effect on pediatric conformal treatment plans using dynamic jaw with Tomotherapy HDA

    SciTech Connect

    Han, Eun Young; Kim, Dong-Wook; Zhang, Xin; Penagaricano, Jose; Liang, Xiaoying; Hardee, Matthew; Morrill, Steve; Ratanatharathorn, Vaneerat

    2015-10-01

    It is important to minimize the radiation dose delivered to healthy tissues in pediatric cancer treatment because of the risk of secondary malignancies. Tomotherapy HDA provides a dynamic jaw (DJ) delivery mode that creates a sharper penumbra at the craniocaudal ends of a target in addition to a fixed jaw (FJ) delivery mode. The purpose of this study was to evaluate its dosimetric effect on the pediatric cancer cases. We included 6 pediatric cases in this study. The dose profiles and plan statistics—target dose conformity, uniformity, organ-at-risk (OAR) mean dose, beam-on time, and integral dose—were compared for each case. Consequently, the target dose coverage and uniformity were similar for different jaw settings. The OAR dose sparing depended on its relative location to the target and disease sites. For example, in the head and neck cancer cases, the brain stem dose using DJ 2.5 was reduced by more than two-fold (2.4 Gy vs. 6.3 Gy) than that obtained with FJ 2.5. The integral dose with DJ 2.5 decreased by more than 9% compared with that with FJ 2.5. Thus, using dynamic jaw in pediatric cases could be critical to reduce a probability of a secondary malignancy.

  19. Calculated dosimetric parameters of the IoGold 125I source model 3631-A.

    PubMed

    Wierzbicki, J G; Rivard, M J; Waid, D S; Arterbery, V E

    1998-11-01

    Basic dosimetric parameters as recommended by the AAPM Task Group No. 43 (TG-43) have been determined for recently available IoGold 125I brachytherapy seeds. Monte Carlo methods (MCNP) were used in the calculation of these parameters in water, and results compared with soon to be published experimental parameters also for 125I IoGold seeds as well with parameters for model 6702 and 6711 125I seeds. These parameters were the radial dose function, anisotropy factor and constant, and the dose rate constant. Using MCNP, values for the radial dose function at 0.5, 2.0, and 5.0 cm were 1.053, 0.877, and 0.443, respectively. The anisotropy factor was 0.975, 0.946, 0.945, and 0.952 at 0.5, 1.0, 2.0, and 5.0 cm, respectively, with an anisotropy constant of 0.95. The IoGold dose rate constant was determined by excluding the low energy titanium characteristic x rays produced in the IoGold titanium capsule. Using this post TG-43 revised NIST air kerma methodology, the IoGold dose rate constant was 0.96 cGy h-1 U-1. These calculatively determined parameters for IoGold seeds were compared with those determined experimentally for IoGold seeds, and also compared with parameters determined for model 6702 and 6711 seeds as presented in TG-43. PMID:9829245

  20. Dosimetric estimates for clinical positron emission tomographic scanning after injection of ( sup 18 F)-6-fluorodopamine

    SciTech Connect

    Goldstein, D.S.; Chang, P.C.; Smith, C.B.; Herscovitch, P.; Austin, S.M.; Eisenhofer, G.; Kopin, I.J. )

    1991-01-01

    Positron emission tomographic (PET) scanning after systemic i.v. injection of fluorine-18-6-fluorodopamine (({sup 18}F)-6F-DA) is a method for visualizing and measuring regional sympathetic nervous system innervation and function. Based on results of preclinical studies of rats and dogs and on previous literature about the fate of injected tracer-labeled catecholamines, dosimetric estimates for clinical studies are presented here. After injection of 1 mCi of ({sup 18}F)-F-DA, the radiation dose would be highest to the wall of the urinary bladder (1.40 rem/mCi), due to accumulation of radioactive metabolites of ({sup 18}F)-F-DA in urine. Radioactivity also would accumulate in bile. Organs receiving the next highest dose would be the kidneys (0.9 rem/mCi) and small intestine (0.2 rem/mCi). The parenchymal radiation dose would be lowest in the brain, since there is an effective blood-brain barrier for circulating catecholamines. Radiation doses to all organs after administration of 1 mCi of ({sup 18}F)-F-DA to humans would be less than 3 rem and, therefore, within current FDA guidelines.

  1. Dosimetric verification of enhanced dynamic wedges by a 2D ion chamber array

    NASA Astrophysics Data System (ADS)

    Oh, Se An; Kim, Sung Kyu; Kang, Min Kyu; Yea, Ji Woon; Kim, Eng Chan

    2013-12-01

    Wedge filters are commonly used to achieve dose uniformity in the target volume in radiotherapy and can be categorized as physical wedges (PWs) and enhanced dynamic wedges (EDWs). The EDW generates PW-like dose profiles while moving the upper jaw in the Y directions with a varying dose rate in the treatment beams. Task Group 53 of the AAPM (American Association of Physicists in Medicine) recommended that the dynamic wedge be verified before implementation in the radiation treatment planning (RTP) system. The aim of this study was to use the I'mRT MatriXX to verify the dose profiles of the EDWs manufactured by Varian. We used Pencil Beam Convolution algorithms (eclipse 8.6) for the calculation and I'mRT MatriXX with Plastic Water® phantom MULTICube for dose measurements. The gamma indices of the calculations and the measurements for the EDWs were 84.84% and 86.54% in 2%/2 mm tolerance, and 99.47% and 99.64% in 3%/3 mm tolerance for wedge angles of 15°, 30°, 45° and 60°, respectively. The dose distributions differed between the calculations using the system and the measurements in the penumbra and the outer beam regions of the wedge fields. We confirmed that the dosimetric verifications of the EDW were acceptable when using the criterion for external beam dose calculations of Task Group 53.

  2. The Application of Elliptic Cylindrical Phantom in Brachytherapy Dosimetric Study of HDR 192Ir Source

    NASA Astrophysics Data System (ADS)

    Ahn, Woo Sang; Park, Sung Ho; Jung, Sang Hoon; Choi, Wonsik; Do Ahn, Seung; Shin, Seong Soo

    2014-06-01

    The purpose of this study is to determine the radial dose function of HDR 192Ir source based on Monte Carlo simulation using elliptic cylindrical phantom, similar to realistic shape of pelvis, in brachytherapy dosimetric study. The elliptic phantom size and shape was determined by analysis of dimensions of pelvis on CT images of 20 patients treated with brachytherapy for cervical cancer. The radial dose function obtained using the elliptic cylindrical water phantom was compared with radial dose functions for different spherical phantom sizes, including the Williamsion's data loaded into conventional planning system. The differences in the radial dose function for the different spherical water phantoms increase with radial distance, r, and the largest differences in the radial dose function appear for the smallest phantom size. The radial dose function of the elliptic cylindrical phantom significantly decreased with radial distance in the vertical direction due to different scatter condition in comparison with the Williamson's data. Considering doses to ICRU rectum and bladder points, doses to reference points can be underestimated up to 1-2% at the distance from 3 to 6 cm. The radial dose function in this study could be used as realistic data for calculating the brachytherapy dosimetry for cervical cancer.

  3. Helical Tomotherapy in Children and Adolescents: Dosimetric Comparisons, Opportunities and Issues

    PubMed Central

    Mascarin, Maurizio; Giugliano, Francesca Maria; Coassin, Elisa; Drigo, Annalisa; Chiovati, Paola; Dassie, Andrea; Franchin, Giovanni; Minatel, Emilio; Trovò, Mauro Gaetano

    2011-01-01

    Helical Tomotherapy (HT) is a highly conformal image-guided radiation technique, introduced into clinical routine in 2006 at the Centro di Riferimento Oncologico Aviano (Italy). With this new technology, intensity-modulated radiotherapy (IMRT) is delivered using a helicoidal method. Here we present our dosimetric experiences using HT in 100 children, adolescents and young adults treated from May 2006 to February 2011. The median age of the patients was 13 years (range 1–24). The most common treated site was the central nervous system (50; of these, 24 were craniospinal irradiations), followed by thorax (22), head and neck (10), abdomen and pelvis (11), and limbs (7). The use of HT was calculated in accordance to the target dose conformation, the target size and shape, the dose to critical organs adjacent to the target, simultaneous treatment of multiple targets, and re-irradiation. HT has demonstrated to improve target volume dose homogeneity and the sparing of critical structures, when compared to 3D Linac-based radiotherapy (RT). In standard cases this technique represented a comparable alternative to IMRT delivered with conventional linear accelerator. In certain cases (e.g., craniospinal and pleural treatments) only HT generated adequate treatment plans with good target volume coverage. However, the gain in target conformality should be balanced with the spread of low-doses to distant areas. This remains an open issue for the potential risk of secondary malignancies (SMNs) and longer follow-up is mandatory. PMID:24213120

  4. Evaluation of the deformation and corresponding dosimetric implications in prostate cancer treatment

    PubMed Central

    Glide-Hurst, Carri; Nurushev, Teamour; Xing, Lei; Kim, Jinkoo; Zhong, Hualiang; Liu, Dezhi; Liu, Manju; Burmeister, Jay; Movsas, Benjamin; Chetty, Indrin J

    2013-01-01

    The cone-beam computed tomography (CBCT) imaging modality is an integral component of image-guided adaptive radiation therapy (IGART), which uses patient-specific dynamic/temporal information for potential treatment plan modification. In this study, an offline process for the integral component IGART framework has been implemented that consists of deformable image registration (DIR) and its validation, dose reconstruction, dose accumulation and dose verification. This study compares the differences between planned and estimated delivered doses under an IGART framework of five patients undergoing prostate cancer radiation therapy. The dose calculation accuracy on CBCT was verified by measurements made in a Rando pelvic phantom. The accuracy of DIR on patient image sets was evaluated in three ways: landmark matching with fiducial markers, visual image evaluation and unbalanced energy (UE); UE has been previously demonstrated to be a feasible method for the validation of DIR accuracy at a voxel level. The dose calculated on each CBCT image set was reconstructed and accumulated over all fractions to reflect the ‘actual dose’ delivered to the patient. The deformably accumulated (delivered) plans were then compared to the original (static) plans to evaluate tumor and normal tissue dose discrepancies. The results support the utility of adaptive planning, which can be used to fully elucidate the dosimetric impact based on the simulated delivered dose to achieve the desired tumor control and normal tissue sparing, which may be of particular importance in the context of hypofractionated radiotherapy regimens. PMID:22863976

  5. Topological detector: measuring continuous dosimetric quantities with few-element detector array.

    PubMed

    Han, Zhaohui; Brivio, Davide; Sajo, Erno; Zygmanski, Piotr

    2016-08-21

    A prototype topological detector was fabricated and investigated for quality assurance of radiation producing medical devices. Unlike a typical array or flat panel detector, a topological detector, while capable of achieving a very high spatial resolution, consists of only a few elements and therefore is much simpler in construction and more cost effective. The key feature allowing this advancement is a geometry-driven design that is customized for a specific dosimetric application. In the current work, a topological detector of two elements was examined for the positioning verification of the radiation collimating devices (jaws, MLCs, and blades etc). The detector was diagonally segmented from a rectangular thin film strip (2.5 cm  ×  15 cm), giving two contiguous but independent detector elements. The segmented area was the central portion of the strip measuring 5 cm in length. Under irradiation, signals from each detector element were separately digitized using a commercial multichannel data acquisition system. The center and size of an x-ray field, which were uniquely determined by the collimator positions, were shown mathematically to relate to the difference and sum of the two signals. As a proof of concept, experiments were carried out using slit x-ray fields ranging from 2 mm to 20 mm in size. It was demonstrated that, the collimator positions can be accurately measured with sub-millimeter precisions. PMID:27452789

  6. Dosimetric evaluations of the interplay effect in respiratory-gated intensity-modulated radiation therapy

    SciTech Connect

    Chen Hungcheng; Wu, Andrew; Brandner, Edward D.; Heron, Dwight E.; Huq, M. Saiful; Yue, Ning J.; Chen Wencheng

    2009-03-15

    The interplay between a mobile target and a dynamic multileaf collimator can compromise the accuracy of intensity-modulated radiation therapy (IMRT). Our goal in this study is to investigate the dosimetric effects caused by the respiratory motion during IMRT. A moving phantom was built to simulate the typical breathing motion. Different sizes of the gating windows were selected for gated deliveries. The residual motions during the beam-on period ranged from 0.5 to 3 cm. An IMRT plan with five treatment fields from different gantry angles were delivered to the moving phantom for three irradiation conditions: Stationary condition, moving with the use of gating system, and moving without the use of gating system. When the residual motion was 3 cm, the results showed significant differences in dose distributions between the stationary condition and the moving phantom without gating beam control. The overdosed or underdosed areas enclosed about 33% of the treatment area. In contrast, the dose distribution on the moving phantom with gating window set to 0.5 cm showed no significant differences from the stationary phantom. With the appropriate setting of the gating window, the deviation of dose from the respiratory motion can be minimized. It appeals that limiting the residual motion to less than 0.5 cm is critical for the treatments of mobile structures.

  7. Potential application of metal nanoparticles for dosimetric systems: Concepts and perspectives

    NASA Astrophysics Data System (ADS)

    Guidelli, Eder José; Baffa, Oswaldo

    2014-11-01

    Metallic nanoparticles increase the delivered dose and consequently enhance tissue radio sensitization during radiation therapy of cancer. The Dose Enhancement Factor (DEF) corresponds to the ratio between the dose deposited on a tissue containing nanoparticles, and the dose deposited on a tissue without nanoparticles. In this sense, we have used electron spin resonance spectroscopy (ESR) to investigate how silver and gold nanoparticles affect the dose deposition in alanine dosimeters, which act as a surrogate of soft tissue. Besides optimizing radiation absorption by the dosimeter, the optical properties of these metal nanoparticles could also improve light emission from materials employed as radiation detectors. Therefore, we have also examined how the plasmonic properties of noble metal nanoparticles could enhance radiation detection using optically stimulated luminescence (OSL) dosimetry. This work will show results on how the use of gold and silver nanoparticles are beneficial for the ESR and OSL dosimetric techniques, and will describe the difficulties we have been facing, the challenges to overcome, and the perspectives.

  8. Dosimetric Evaluation of a Simple Planning Technique for Improving Intensity-Modulated Radiotherapy for Nasopharyngeal Cancer

    PubMed Central

    Xie, Wen-Jia; Xie, Liang-Xi

    2015-01-01

    Purpose To evaluate the dosimetric outcomes of a simple planning technique for improving intensity-modulated radiotherapy (IMRT) for nasopharyngeal cancer (NPC). Methods For 39 NPC cases, generally acceptable original plans were generated and were improved by the two planning techniques, respectively: (1) a basal-dose-compensation (BDC) technique, in which the treatment plans were re-optimized based on the original plans; (2) a local-dose-control (LDC) technique, in which the original plans were re-optimized with constraints for hot and cold spots. The BDC, original, and LDC plans were then compared regarding homogeneity index (HI) and conformity index (CI) of planning target volumes (PTVs), organ-at-risk (OAR) sparing and monitor units (MUs) per fraction. The whole planning times were also compared between the BDC and LDC plans. Results The BDC plans had superior HIs / CIs, by 13-24% / 3-243%, respectively, over the original plans. Compared to the LDC plans, the BDC plans provided better HIs only for PTVnx (the PTV of nasopharyngeal primary tumor) by 11% and better CIs for all PTVs by 2-134%. The BDC technique spared most OARs, by 1-9%. The average MUs of the BDC, original, and LDC plans were 2149, 2068 and 2179, respectively. The average whole planning times were 48 and 69 minutes for the BDC and LDC plans, respectively. Conclusions For the IMRT of nasopharyngeal cancer, the BDC planning technique can improve target dose homogeneity, conformity and OAR sparing, with better planning efficiency. PMID:26132167

  9. Optimization of Internal Margin to Account for Dosimetric Effects of Respiratory Motion

    SciTech Connect

    Mutaf, Yildirim D. Brinkmann, Debra H.

    2008-04-01

    Purpose: Use of internal margins to account for respiratory motion of the target volumes is a common strategy in radiotherapy of mobile tumors. Although efficient for tumor coverage, this expansion also risks increased toxicity to nearby healthy organs and therefore requires a careful selection of appropriate margins. In this study, we demonstrate an optimization of the internal margin used to account for respiration motion. Methods and Materials: Three-dimensional conformal treatment plans for phantom spherical target volumes as well as clinical treatment plans of 11 patients were evaluated retrospectively for optimum internal margin selection. A software-based simulation of respiration motion was performed for all cases. Moreover, the interplay with treatment setup uncertainties and corresponding margins was investigated in the phantom study. Results: Optimum internal margins in both phantom and patient studies were found to be substantially smaller than the actual target displacement due to respiration. The optimal internal margin was also observed to be approximately independent of the setup margins. Furthermore, no statistically significant dependence on target size and shape was observed in the group of 11 patients. Conclusions: These findings present significant implications for treatment planning of mobile targets, such as tumors found in the lung and upper abdomen. We conclude that the full motion amplitude for the internal margin is overly conservative, and optimization of the internal margin provides improved sparing of nearby organs at risk without sacrificing dosimetric coverage for the target.

  10. Dosimetric consequences of pencil beam width variations in scanned beam particle therapy

    NASA Astrophysics Data System (ADS)

    Chanrion, M. A.; Ammazzalorso, F.; Wittig, A.; Engenhart-Cabillic, R.; Jelen, U.

    2013-06-01

    Scanned ion beam delivery enables the highest degree of target dose conformation attainable in external beam radiotherapy. Nominal pencil beam widths (spot sizes) are recorded during treatment planning system commissioning. Due to changes in the beam-line optics, the actual spot sizes may differ from these commissioning values, leading to differences between planned and delivered dose. The purpose of this study was to analyse the dosimetric consequences of spot size variations in particle therapy treatment plans. For 12 patients with skull base tumours and 12 patients with prostate carcinoma, scanned-beam carbon ion and proton treatment plans were prepared and recomputed simulating spot size changes of (1) ±10% to simulate the typical magnitude of fluctuations, (2) ±25% representing the worst-case scenario and (3) ±50% as a part of a risk analysis in case of fault conditions. The primary effect of the spot size variation was a dose deterioration affecting the target edge: loss of target coverage and broadening of the lateral penumbra (increased spot size) or overdosage and contraction of the lateral penumbra (reduced spot size). For changes ⩽25%, the resulting planning target volume mean 95%-isodose line coverage (CI-95%) deterioration was ranging from negligible to moderate. In some cases changes in the dose to adjoining critical structures were observed.

  11. Technical and dosimetric aspects of the total skin electron beam technique implemented at Heidelberg University Hospital

    PubMed Central

    Hensley, Frank W.; Major, Gerald; Edel, Carolin; Hauswald, Henrik; Bischof, Marc

    2013-01-01

    Aim To give a technical description and present the dosimetric proporties of the total skin electron beam technique implemented at Heidelberg University Hospital. Background Techniques used for total skin electron beam irradiation were developed as early as in the 1960s to 1980s and have, since then, hardly changed. However, new measurements of the established methods allow deeper insight into the dose distributions and reasons for possible deviations from uniform dose. Materials and methods The TSEI technique applied at Heidelberg University Hospital since 1992 consists of irradiating the patient with a superposition of two beams of low energy electrons at gantry angles of 72° and 108° while he is rotating in a standing position on a turntable at 370 cm distance from the accelerator. The energy of the electron beam is degraded to 3.9 MeV by passing through an attenuator of 6 mm of Perspex. A recent re-measurement of the dose distribution is presented using modern dosimetry tools like a linear array of ionization chambers in combination with established methods like thermoluminescent detectors and film dosimetry. Results The measurements show a strong dependence of dose uniformity on details of the setup like gantry angles. Conclusions Dose uniformity of −4/+8% to the majority of the patient's skin can be achieved, however, for the described rotational technique overdoses up to more than 20% in small regions seem unavoidable. PMID:24936332

  12. Dosimetric evaluation of a Monte Carlo IMRT treatment planning system incorporating the MIMiC

    NASA Astrophysics Data System (ADS)

    Rassiah-Szegedi, P.; Fuss, M.; Sheikh-Bagheri, D.; Szegedi, M.; Stathakis, S.; Lancaster, J.; Papanikolaou, N.; Salter, B.

    2007-12-01

    The high dose per fraction delivered to lung lesions in stereotactic body radiation therapy (SBRT) demands high dose calculation and delivery accuracy. The inhomogeneous density in the thoracic region along with the small fields used typically in intensity-modulated radiation therapy (IMRT) treatments poses a challenge in the accuracy of dose calculation. In this study we dosimetrically evaluated a pre-release version of a Monte Carlo planning system (PEREGRINE 1.6b, NOMOS Corp., Cranberry Township, PA), which incorporates the modeling of serial tomotherapy IMRT treatments with the binary multileaf intensity modulating collimator (MIMiC). The aim of this study is to show the validation process of PEREGRINE 1.6b since it was used as a benchmark to investigate the accuracy of doses calculated by a finite size pencil beam (FSPB) algorithm for lung lesions treated on the SBRT dose regime via serial tomotherapy in our previous study. Doses calculated by PEREGRINE were compared against measurements in homogeneous and inhomogeneous materials carried out on a Varian 600C with a 6 MV photon beam. Phantom studies simulating various sized lesions were also carried out to explain some of the large dose discrepancies seen in the dose calculations with small lesions. Doses calculated by PEREGRINE agreed to within 2% in water and up to 3% for measurements in an inhomogeneous phantom containing lung, bone and unit density tissue.

  13. Dosimetric characterization of the irradiation cavity for accelerator-based in vivo neutron activation analysis.

    PubMed

    Byun, S H; Pejović-Milić, A; McMaster, S; Matysiak, W; Aslam; Liu, Z; Watters, L M; Prestwich, W V; McNeill, F E; Chettle, D R

    2007-03-21

    A neutron irradiation cavity for in vivo activation analysis has been characterized to estimate its dosimetric specifications. The cavity is defined to confine irradiation to the hand and modifies the neutron spectrum produced by a low energy accelerator neutron source to optimize activation per dose. Neutron and gamma-ray dose rates were measured with the microdosimetric technique using a tissue-equivalent proportional counter at the hand irradiation site and inside the hand access hole. For the outside of the cavity, a spherical neutron dose equivalent meter and a Farmer dosemeter were employed instead due to the low intensity of the radiation field. The maximum dose equivalent rate at the outside of the cavity was 2.94 microSv/100 microA min, which is lower by a factor of 1/2260 than the dose rate at the hand irradiation position. The local dose contributions from a hand, an arm and the rest of a body to the effective dose rate were estimated to be 1.73, 0.782 and 2.94 microSv/100 microA min, respectively. For the standard irradiation protocol of the in vivo hand activation, 300 microA min, an effective dose of 16.3 microSv would be delivered. PMID:17455391

  14. Relative TL and OSL efficiency to protons of various dosimetric materials.

    PubMed

    Sądel, M; Bilski, P; Swakoń, J

    2014-10-01

    Thermoluminescence (TL) and optically stimulated luminescence (OSL) are the well-known phenomena used for passive methods of dose measurements. TL and OSL detectors are frequently used in the dosimetry of cosmic radiation in space and of particle radiotherapy beams. However, the relative TL/OSL efficiency, which is defined as a ratio of the emitted light intensity per unit dose for a given radiation type, to the same quantity for the reference gamma radiation is not constant and depends on radiation type and energy. In the present work several types of TL and OSL dosimetric materials, including lithium fluoride (LiF), aluminium oxide, beryllium oxide and lithium aluminate, were tested with protons. The measurements were realised exploiting the 60-MeV proton beam of the AIC-144 cyclotron in the Proton Eye Radiotherapy Facility at Institute of Nuclear Physics (IFJ PAN). The influence of proton energy on the relative efficiency and other TL/OSL characteristics of the studied detector types was presented. PMID:24036656

  15. Effect of radiation on solid paracetamol: ESR identification and dosimetric features of gamma-irradiated paracetamol

    NASA Astrophysics Data System (ADS)

    Polat, M.; Korkmaz, M.

    2006-01-01

    In the present work, electron spin resonance (ESR) identification of gamma-irradiated paracetamol and its potential use as a normal and/or accidental dosimetric material were investigated in the dose range of 2.5-25 kGy. Both unirradiated paracetamol and mechanically ground vermidon samples exhibited a weak single resonance line at g = 2.0049 +/- 0.0006 and had Delta H-pp = 0.6 +/- 0.02 mT. Gamma irradiation produced an increase in signal intensity with a small hyperfine splitting in both paracetamol and vermidon and many weak resonance lines on both sides of a central line in the case of vermidon. Dose-response curves associated with central line of paracetamol and vermidon were found to follow polynomial and linear function, respectively. Simulation calculations based on the room temperature ESR intensity data of the paracetamol sample irradiated at 10 kGy were performed to determine the structure and spectral parameters of the radiation-induced radical species involved in the formation of the experimental ESR spectrum of paracetamol.

  16. On the physical, spectral, and dosimetric characteristics of a new {sup 125}I brachytherapy source

    SciTech Connect

    Pirchio, Rosana; Galiano, Eduardo; Saravi, Margarita; Banchik, David; Munoz, Carlos

    2007-07-15

    A new {sup 125}I source under the name Braquibac{sup TM} has been developed in Argentina for interstitial brachytherapy applications. The aim of this work is to study the new seed's design and to calculate its dosimetric parameters. Radiographic and destructive tests were carried out on inactive seeds to determine the physical characteristics of the source. Values of g(r), {lambda}, F(r,{theta}), and {phi}{sub an}(r), were obtained in water and air by simulation using the MCNP5 Monte Carlo code according to the methodology recommended in TG-43 and updated in TG-43U1. The dose rate constant was determined to be 0.937{+-}0.004 cGy h{sup -1} U{sup -1} (overall statistical uncertainty {+-}2.7%). S{sub k} per unity activity was calculated to be 0.671{+-}0.003 cGy cm{sup 2} h{sup -1} mCi{sup -1} by simulation of the seed in dry air using point detectors. Spectroscopic studies for both the new and the Amersham model 6711 seed were performed using an HPGe planar detector. The emission spectra of both seeds proved to be very similar. The anisotropy of the total photon intensity in air was measured in planes containing the seed's short and long axes using the HPGe detector. The minimum photon intensity for the new seed was 31.14{+-}3.10% of the transverse intensity.

  17. Dosimetric shield evaluation with tungsten sheet in 4, 6, and 9MeV electron beams.

    PubMed

    Fujimoto, Takahiro; Monzen, Hajime; Nakata, Manabu; Okada, Takashi; Yano, Shinsuke; Takakura, Toru; Kuwahara, Junichi; Sasaki, Makoto; Higashimura, Kyoji; Hiraoka, Masahiro

    2014-11-01

    In electron radiotherapy, shielding material is required to attenuate beam and scatter. A newly introduced shielding material, tungsten functional paper (TFP), has been anticipated to become a very useful device that is lead-free, light, flexible, and easily processed, containing very fine tungsten powder at as much as 80% by weight. The purpose of this study was to investigate the dosimetric changes due to TFP shielding for electron beams. TFP (thickness 0-15mm) was placed on water or a water-equivalent phantom. Percentage depth ionization and transmission were measured for 4, 6, and 9MeV electron beams. Off-center ratio was also measured using film dosimetry at depth of dose maximum under similar conditions. Then, beam profiles and transmission with two shielding materials, TFP and lead, were evaluated. Reductions of 95% by using TFP at 0.5cm depth occurred at 4, 9, and 15mm with 4, 6, and 9MeV electron beams, respectively. It is found that the dose tend to increase at the field edge shaped with TFP, which might be influenced by the thickness. TFP has several unique features and is very promising as a useful tool for radiation protection for electron beams, among others. PMID:24953537

  18. Dosimetric and clinical advantages of deep inspiration breath-hold (DIBH) during radiotherapy of breast cancer

    PubMed Central

    2013-01-01

    Background To investigate the potential dosimetric and clinical benefits of Deep Inspiration Breath-Hold (DIBH) technique during radiotherapy of breast cancer compared with Free Breathing (FB). Methods Eight left-sided breast cancer patients underwent a supervised breath hold during treatment. For each patient, two CT scans were acquired with and without breath hold, and virtual simulation was performed for conventional tangential fields, utilizing 6 or 15 MV photon fields. The resulting dose–volume histograms were calculated, and the volumes of heart/lung irradiated to given doses were assessed. The left anterior descending coronary artery (LAD) mean and maximum doses were calculated, together with tumour control probability (TCP) and normal tissue complication probabilities (NTCP) for lung and heart. Results For all patients a reduction of at least 16% in lung mean dose and at least 20% in irradiated pulmonary volumes was observed when DIBH was applied. Heart and LAD maximum doses were decreased by more than 78% with DIBH. The NTCP values for pneumonitis and long term cardiac mortality were also reduced by about 11% with DIBH. The NTCP values for pericarditis were zero for both DIBH and FB. Conclusion Delivering radiation in DIBH conditions the dose to the surrounding normal structures could be reduced, in particular heart, LAD and lung, due to increased distance between target and heart, and to reduced lung density. PMID:24423396

  19. Dosimetric impact of a CT metal artefact suppression algorithm for proton, electron and photon therapies

    NASA Astrophysics Data System (ADS)

    Wei, Jikun; Sandison, George A.; Hsi, Wen-Chien; Ringor, Michael; Lu, Xiaoyi

    2006-10-01

    Accurate dose calculation is essential to precision radiation treatment planning and this accuracy depends upon anatomic and tissue electron density information. Modern treatment planning inhomogeneity corrections use x-ray CT images and calibrated scales of tissue CT number to electron density to provide this information. The presence of metal in the volume scanned by an x-ray CT scanner causes metal induced image artefacts that influence CT numbers and thereby introduce errors in the radiation dose distribution calculated. This paper investigates the dosimetric improvement achieved by a previously proposed x-ray CT metal artefact suppression technique when the suppressed images of a patient with bilateral hip prostheses are used in commercial treatment planning systems for proton, electron or photon therapies. For all these beam types, this clinical image and treatment planning study reveals that the target may be severely underdosed if a metal artefact-contaminated image is used for dose calculations instead of the artefact suppressed one. Of the three beam types studied, the metal artefact suppression is most important for proton therapy dose calculations, intermediate for electron therapy and least important for x-ray therapy but still significant. The study of a water phantom having a metal rod simulating a hip prosthesis indicates that CT numbers generated after image processing for metal artefact suppression are accurate and thus dose calculations based on the metal artefact suppressed images will be of high fidelity.

  20. Monte Carlo calculations and experimental measurements of dosimetric parameters of the IRA-103Pd brachytherapy source.

    PubMed

    Sadeghi, Mahdi; Raisali, Gholamreza; Hosseini, S Hamed; Shavar, Arzhang

    2008-04-01

    This article presents a brachytherapy source having 103Pd adsorbed onto a cylindrical silver rod that has been developed by the Agricultural, Medical, and Industrial Research School for permanent implant applications. Dosimetric characteristics (radial dose function, anisotropy function, and anisotropy factor) of this source were experimentally and theoretically determined in terms of the updated AAPM Task group 43 (TG-43U1) recommendations. Monte Carlo simulations were used to calculate the dose rate constant. Measurements were performed using TLD-GR200A circular chip dosimeters using standard methods employing thermoluminescent dosimeters in a Perspex phantom. Precision machined bores in the phantom located the dosimeters and the source in a reproducible fixed geometry, providing for transverse-axis and angular dose profiles over a range of distances from 0.5 to 5 cm. The Monte Carlo N-particle (MCNP) code, version 4C simulation techniques have been used to evaluate the dose-rate distributions around this model 103Pd source in water and Perspex phantoms. The Monte Carlo calculated dose rate constant of the IRA-103Pd source in water was found to be 0.678 cGy h(-1) U(-1) with an approximate uncertainty of +/-0.1%. The anisotropy function, F(r, theta), and the radial dose function, g(r), of the IRA- 103Pd source were also measured in a Perspex phantom and calculated in both Perspex and liquid water phantoms. PMID:18491522

  1. Oil Exploration Mapping

    NASA Technical Reports Server (NTRS)

    1994-01-01

    After concluding an oil exploration agreement with the Republic of Yemen, Chevron International needed detailed geologic and topographic maps of the area. Chevron's remote sensing team used imagery from Landsat and SPOT, combining images into composite views. The project was successfully concluded and resulted in greatly improved base maps and unique topographic maps.

  2. Reading Angles in Maps

    ERIC Educational Resources Information Center

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S.

    2014-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections…

  3. Applications of Concept Mapping

    ERIC Educational Resources Information Center

    De Simone, Christina

    2007-01-01

    This article reviews three major uses of the concept-mapping strategies for postsecondary learning: the external representation of concept maps as an external scratch pad to represent major ideas and their organization, the mental construction of concept maps when students are seeking a time-efficient tool, and the electronic construction and…

  4. Mapping Sociological Concepts.

    ERIC Educational Resources Information Center

    Trepagnier, Barbara

    2002-01-01

    Focuses on the use of cognitive mapping within sociology. Describes an assignment where students created a cognitive map that focused on names of theorists and concepts related to them. Discusses sociological imagination in relation to cognitive mapping and the assessment of the assignment. (CMK)

  5. Statistical Mapping by Computer.

    ERIC Educational Resources Information Center

    Utano, Jack J.

    The function of a statistical map is to provide readers with a visual impression of the data so that they may be able to identify any geographic characteristics of the displayed phenomena. The increasingly important role played by the computer in the production of statistical maps is manifested by the varied examples of computer maps in recent…

  6. Using maps in genealogy

    USGS Publications Warehouse

    U.S. Geological Survey

    1999-01-01

    Maps are one of many sources you may need to complete a family tree. In genealogical research, maps can provide clues to where our ancestors may have lived and where to look for written records about them. Beginners should master basic genealogical research techniques before starting to use topographic maps.

  7. Quantitative DNA fiber mapping

    DOEpatents

    Gray, Joe W.; Weier, Heinz-Ulrich G.

    1998-01-01

    The present invention relates generally to the DNA mapping and sequencing technologies. In particular, the present invention provides enhanced methods and compositions for the physical mapping and positional cloning of genomic DNA. The present invention also provides a useful analytical technique to directly map cloned DNA sequences onto individual stretched DNA molecules.

  8. Beam’s-eye-view dosimetrics (BEVD) guided rotational station parameter optimized radiation therapy (SPORT) planning based on reweighted total-variation minimization

    NASA Astrophysics Data System (ADS)

    Kim, Hojin; Li, Ruijiang; Lee, Rena; Xing, Lei

    2015-03-01

    Conventional VMAT optimizes aperture shapes and weights at uniformly sampled stations, which is a generalization of the concept of a control point. Recently, rotational station parameter optimized radiation therapy (SPORT) has been proposed to improve the plan quality by inserting beams to the regions that demand additional intensity modulations, thus formulating non-uniform beam sampling. This work presents a new rotational SPORT planning strategy based on reweighted total-variation (TV) minimization (min.), using beam’s-eye-view dosimetrics (BEVD) guided beam selection. The convex programming based reweighted TV min. assures the simplified fluence-map, which facilitates single-aperture selection at each station for single-arc delivery. For the rotational arc treatment planning and non-uniform beam angle setting, the mathematical model needs to be modified by additional penalty term describing the fluence-map similarity and by determination of appropriate angular weighting factors. The proposed algorithm with additional penalty term is capable of achieving more efficient and deliverable plans adaptive to the conventional VMAT and SPORT planning schemes by reducing the dose delivery time about 5 to 10 s in three clinical cases (one prostate and two head-and-neck (HN) cases with a single and multiple targets). The BEVD guided beam selection provides effective and yet easy calculating methodology to select angles for denser, non-uniform angular sampling in SPORT planning. Our BEVD guided SPORT treatment schemes improve the dose sparing to femoral heads in the prostate and brainstem, parotid glands and oral cavity in the two HN cases, where the mean dose reduction of those organs ranges from 0.5 to 2.5 Gy. Also, it increases the conformation number assessing the dose conformity to the target from 0.84, 0.75 and 0.74 to 0.86, 0.79 and 0.80 in the prostate and two HN cases, while preserving the delivery efficiency, relative to conventional single-arc VMAT plans.

  9. Map projections for larger-scale mapping

    NASA Technical Reports Server (NTRS)

    Snyder, J. P.

    1982-01-01

    For the U.S. Geological Survey maps at 1:1,000,000-scale and larger, the most common projections are conformal, such as the Transverse Mercator and Lambert Conformal Conic. Projections for these scales should treat the Earth as an ellipsoid. In addition, the USGS has conceived and designed some new projections, including the Space Oblique Mercator, the first map projection designed to permit low-distortion mapping of the Earth from satellite imagery, continuously following the groundtrack. The USGS has programmed nearly all pertinent projection equations for inverse and forward calculations. These are used to plot maps or to transform coordinates from one projection to another. The projections in current use are described.

  10. Cartographic mapping study

    NASA Technical Reports Server (NTRS)

    Wilson, C.; Dye, R.; Reed, L.

    1982-01-01

    The errors associated with planimetric mapping of the United States using satellite remote sensing techniques are analyzed. Assumptions concerning the state of the art achievable for satellite mapping systems and platforms in the 1995 time frame are made. An analysis of these performance parameters is made using an interactive cartographic satellite computer model, after first validating the model using LANDSAT 1 through 3 performance parameters. An investigation of current large scale (1:24,000) US National mapping techniques is made. Using the results of this investigation, and current national mapping accuracy standards, the 1995 satellite mapping system is evaluated for its ability to meet US mapping standards for planimetric and topographic mapping at scales of 1:24,000 and smaller.

  11. On genetic map functions

    SciTech Connect

    Zhao, Hongyu; Speed, T.P.

    1996-04-01

    Various genetic map functions have been proposed to infer the unobservable genetic distance between two loci from the observable recombination fraction between them. Some map functions were found to fit data better than others. When there are more than three markers, multilocus recombination probabilities cannot be uniquely determined by the defining property of map functions, and different methods have been proposed to permit the use of map functions to analyze multilocus data. If for a given map function, there is a probability model for recombination that can give rise to it, then joint recombination probabilities can be deduced from this model. This provides another way to use map functions in multilocus analysis. In this paper we show that stationary renewal processes give rise to most of the map functions in the literature. Furthermore, we show that the interevent distributions of these renewal processes can all be approximated quite well by gamma distributions. 43 refs., 4 figs.

  12. Comparative dosimetric study of two strategies of intensity-modulated radiotherapy in nasopharyngeal cancer

    SciTech Connect

    Chen, S.-W.; Yang, S.-N.; Liang, J.-A.; Shiau, A.-C. . E-mail: joseph.shiau@msa.hinet.net; Lin, F.-J.

    2005-01-01

    This study compared the target volume coverage and normal tissues sparing of simultaneous integrated boost (SIB-IMRT, 1-phase) and sequential-IMRT (2-phase) for nasopharyngeal carcinoma (NPC). Fourteen consecutive patients with newly diagnosed primary NPC were enrolled in this study. The CT images were transferred to a commercial planning system for structural delineation. The gross tumor volume (GTV) included gross nasopharyngeal tumor and involved lymph nodes of more than 1-cm diameter. The clinical target volume (CTV) modeled two regions considered to represent different risks. CTV1 encompassed the GTV with 5-10-mm margin of adjacent tissues. CTV2 encompassed ipsilateral or contralateral elective nodal regions at risk of harboring microscopic tumor. A commercial IMRT treatment planning system (Eclipse Version 7.1) was used to provide treatment planning. Seven fixed-gantry (0{sup o}, 50{sup o}, 100{sup o}, 150{sup o}, 210{sup o}, 260{sup o}, 310{sup o}) angles were designated. The 14 patients were treated with sequential-IMRT, and treatment was then replanned with an SIB strategy to compare the dosimetric difference. For the sequential strategy, the dose delivered to CTV1/CTV2 in the first course was 54 Gy (1.8 Gy x 30 Fr); while CTV1 was boosted by an additional 16.2 Gy (1.8 Gy x 9 Fr) in the second course. For SIB-IMRT, the dose prescribed to CTV1 was 69.7 Gy (2.05 Gy x 34 Fr); 56.1 Gy was given to CTV2 (1.65 Gy x 34 Fr). A statistical analysis of the dose-volume-histogram of target volumes and critical organs was performed. Paired Student's t-test was used to compare the dosimetric differences between the two techniques. The mean dose to CTV1 was 101.7 {+-} 2.4% and 102.3 {+-} 3.1% of the prescribed dose for SIB-IMRT and sequential-IMRT, respectively. The mean CTV2 dose was 109.8 {+-} 4.7% of the prescribed dose for SIB-IMRT and 112.6 {+-} 6.0% of the prescribed dose for sequential-IMRT. The maximal dose to the spinal cord was 4489 {+-} 495 cGy and 3547

  13. Dosimetric comparison of Acuros XB, AAA, and XVMC in stereotactic body radiotherapy for lung cancer

    SciTech Connect

    Tsuruta, Yusuke; Nakata, Manabu; Higashimura, Kyoji; Nakamura, Mitsuhiro Matsuo, Yukinori; Monzen, Hajime; Mizowaki, Takashi; Hiraoka, Masahiro

    2014-08-15

    Purpose: To compare the dosimetric performance of Acuros XB (AXB), anisotropic analytical algorithm (AAA), and x-ray voxel Monte Carlo (XVMC) in heterogeneous phantoms and lung stereotactic body radiotherapy (SBRT) plans. Methods: Water- and lung-equivalent phantoms were combined to evaluate the percentage depth dose and dose profile. The radiation treatment machine Novalis (BrainLab AG, Feldkirchen, Germany) with an x-ray beam energy of 6 MV was used to calculate the doses in the composite phantom at a source-to-surface distance of 100 cm with a gantry angle of 0°. Subsequently, the clinical lung SBRT plans for the 26 consecutive patients were transferred from the iPlan (ver. 4.1; BrainLab AG) to the Eclipse treatment planning systems (ver. 11.0.3; Varian Medical Systems, Palo Alto, CA). The doses were then recalculated with AXB and AAA while maintaining the XVMC-calculated monitor units and beam arrangement. Then the dose-volumetric data obtained using the three different radiation dose calculation algorithms were compared. Results: The results from AXB and XVMC agreed with measurements within ±3.0% for the lung-equivalent phantom with a 6 × 6 cm{sup 2} field size, whereas AAA values were higher than measurements in the heterogeneous zone and near the boundary, with the greatest difference being 4.1%. AXB and XVMC agreed well with measurements in terms of the profile shape at the boundary of the heterogeneous zone. For the lung SBRT plans, AXB yielded lower values than XVMC in terms of the maximum doses of ITV and PTV; however, the differences were within ±3.0%. In addition to the dose-volumetric data, the dose distribution analysis showed that AXB yielded dose distribution calculations that were closer to those with XVMC than did AAA. Means ± standard deviation of the computation time was 221.6 ± 53.1 s (range, 124–358 s), 66.1 ± 16.0 s (range, 42–94 s), and 6.7 ± 1.1 s (range, 5–9 s) for XVMC, AXB, and AAA, respectively. Conclusions: In the

  14. Dosimetric impact of intrafraction motion for compensator-based proton therapy of lung cancer

    NASA Astrophysics Data System (ADS)

    Zhao, Li; Sandison, George A.; Farr, Jonathan B.; Chien Hsi, Wen; Li, X. Allen

    2008-06-01

    Compensator-based proton therapy of lung cancer using an un-gated treatment while allowing the patient to breathe freely requires a compensator design that ensures tumor coverage throughout respiration. Our investigation had two purposes: one is to investigate the dosimetric impact when a composite compensator correction is applied, or is not, and the other one is to evaluate the significance of using different respiratory phases as the reference computed tomography (CT) for treatment planning dose calculations. A 4D-CT-based phantom study and a real patient treatment planning study were performed. A 3D MIP dataset generated over all phases of the acquired 4D-CT scans was adopted to design the field-specific composite aperture and compensator. In the phantom study, the MIP-based compensator design plan named plan D was compared to the other three plans, in which average intensity projection (AIP) images in conjunction with the composite target volume contour copied from the MIP images were used. Relative electron densities within the target envelope were assigned either to original values from the AIP image dataset (plan A) or to predetermined values, 0.8 (plan B) and 0.9 (plan C). In the patient study, the dosimetric impact of a compensator design based on the MIP images (plan ITVMIP) was compared to designs based on end-of-inhale (EOI) (plan ITVEOI) and middle-of-exhale (MOE) CT images (plan ITVMOE). The dose distributions were recalculated for each phase. Throughout the ten phases, it shows that DGTVmin changed slightly from 86% to 89% (SD = 0.9%) of prescribed dose (PD) in the MIP plan, while varying greatly from 10% to 79% (SD = 26.7%) in plan A, 17% to 73% (SD = 22.5%) in plan B and 53% to 73% (SD = 6.8%) in plan C. The same trend was observed for DGTVmean and V95 with less amplitude. In the MIP-based plan ITVMIP, DGTVmean was almost identically equal to 95% in each phase (SD = 0.5%). The patient study verified that the MIP approach increased the minimum

  15. Dosimetric study of 2D ion chamber array matrix for the modern radiotherapy treatment verification.

    PubMed

    Saminathan, Sathiyan; Manickam, Ravikumar; Chandraraj, Varatharaj; Supe, Sanjay S

    2010-01-01

    Intensity-modulated radiotherapy treatment demands stringent quality assurance and accurate dose determination for delivery of highly conformal dose to the patients. Generally 3D dose distributions obtained from a treatment planning system have to be verified by dosimetric methods. Mainly, a comparison of two-dimensional calculated and measured data in several coplanar planes is performed. In principle, there are many possibilities to measure two-dimensional dose distributions such as films, flat-panel electronic portal imaging devices (EPID), ion chambers and ionization chamber arrays, and radiographic and radiochromic films. The flat-panel EPIDs show a good resolution and offer a possibility for real-time measurements: however to convert the signal into dose, a separate commercial algorithm is required. The 2D ion chamber array system offers the real-time measurements. In this study, dosimetric characteristics of 2D ion chamber array matrix were analyzed for verification of radiotherapy treatments. The dose linearity and dose rate effect of the I'matriXX device was studied using 6 MV, 18 MV photons and 12 MeV electrons. The output factor was estimated using I'matriXX device and compared with ion chamber measurements. The ion chamber array system was found to be linear in the dose range of 2-500 cGy and the response of the detector was found to be independent of dose rate between 100 MU/min to 600 MU/min. The estimated relative output factor with I'matriXX was found to match very well with the ion chamber measurements. To check the final dose delivered during IMRT planning, dose distribution patterns such as field-in-field, pyramidal, and chair tests were generated with the treatment planning system (TPS) and the same was executed in the accelerator and measured with the I'matriXX device. The dose distribution pattern measured by the matrix device for field-in-field, pyramidal, and chair test were found to be in good agreement with the calculated dose distribution

  16. Dosimetric characteristics of the novel 2D ionization chamber array OCTAVIUS Detector 1500

    SciTech Connect

    Stelljes, T. S. Looe, H. K.; Chofor, N.; Poppe, B.; Harmeyer, A.; Reuter, J.; Harder, D.

    2015-04-15

    Purpose: The dosimetric properties of the OCTAVIUS Detector 1500 (OD1500) ionization chamber array (PTW-Freiburg, Freiburg, Germany) have been investigated. A comparative study was carried out with the OCTAVIUS Detector 729 and OCTAVIUS Detector 1000 SRS arrays. Methods: The OD1500 array is an air vented ionization chamber array with 1405 detectors in a 27 × 27 cm{sup 2} measurement area arranged in a checkerboard pattern with a chamber-to-chamber distance of 10 mm in each row. A sampling step width of 5 mm can be achieved by merging two measurements shifted by 5 mm, thus fulfilling the Nyquist theorem for intensity modulated dose distributions. The stability, linearity, and dose per pulse dependence were investigated using a Semiflex 31013 chamber (PTW-Freiburg, Freiburg, Germany) as a reference detector. The effective depth of measurement was determined by measuring TPR curves with the array and a Roos chamber type 31004 (PTW-Freiburg, Freiburg, Germany). Comparative output factor measurements were performed with the array, the Semiflex 31010 ionization chamber and the Diode 60012 (both PTW-Freiburg, Freiburg, Germany). The energy dependence of the OD1500 was measured by comparing the array’s readings to those of a Semiflex 31010 ionization chamber for varying mean photon energies at the depth of measurement, applying to the Semiflex chamber readings the correction factor k{sub NR} for nonreference conditions. The Gaussian lateral dose response function of a single array detector was determined by searching the convolution kernel suitable to convert the slit beam profiles measured with a Diode 60012 into those measured with the array’s central chamber. An intensity modulated dose distribution measured with the array was verified by comparing a OD1500 measurement to TPS calculations and film measurements. Results: The stability and interchamber sensitivity variation of the OD1500 array were within ±0.2% and ±0.58%, respectively. Dose linearity was within 1

  17. Dosimetric evaluation of two treatment planning systems for high dose rate brachytherapy applications

    SciTech Connect

    Shwetha, Bondel; Ravikumar, Manickam; Supe, Sanjay S.; Sathiyan, Saminathan; Lokesh, Vishwanath; Keshava, Subbarao L.

    2012-04-01

    Various treatment planning systems are used to design plans for the treatment of cervical cancer using high-dose-rate brachytherapy. The purpose of this study was to make a dosimetric comparison of the 2 treatment planning systems from Varian medical systems, namely ABACUS and BrachyVision. The dose distribution of Ir-192 source generated with a single dwell position was compared using ABACUS (version 3.1) and BrachyVision (version 6.5) planning systems. Ten patients with intracavitary applications were planned on both systems using orthogonal radiographs. Doses were calculated at the prescription points (point A, right and left) and reference points RU, LU, RM, LM, bladder, and rectum. For single dwell position, little difference was observed in the doses to points along the perpendicular bisector. The mean difference between ABACUS and BrachyVision for these points was 1.88%. The mean difference in the dose calculated toward the distal end of the cable by ABACUS and BrachyVision was 3.78%, whereas along the proximal end the difference was 19.82%. For the patient case there was approximately 2% difference between ABACUS and BrachyVision planning for dose to the prescription points. The dose difference for the reference points ranged from 0.4-1.5%. For bladder and rectum, the differences were 5.2% and 13.5%, respectively. The dose difference between the rectum points was statistically significant. There is considerable difference between the dose calculations performed by the 2 treatment planning systems. It is seen that these discrepancies are caused by the differences in the calculation methodology adopted by the 2 systems.

  18. Dosimetric characteristics of linear accelerator photon beams with small monitor unit settings.

    PubMed

    Kang, Sei-Kwon; Cheong, Kwang-Ho; Hwang, Taejin; Cho, Byung Chul; Kim, Su Ssan; Kim, Kyoung Ju; Oh, Do Hoon; Bae, Hoonsik; Suh, Tae-Suk

    2008-11-01

    Several studies on the effect of tumor cell killing by dose rate variation have implied that the use of a shorter treatment time is more favorable for intensity modulated radiation therapy (IMRT). Aiming at step-and-shoot IMRT with higher dose rates, the stabilities of beam output and profiles with small monitor unit (MU) settings were investigated for various dose rates. With the use of a Varian 21EX (Varian Medical Systems Inc., Palo Alto, CA), static and step-and-shoot IMRT beam output along with profiles were measured by use of an ion chamber and a two-dimensional diode array detector as a function of monitor units and dose rates. For a static case, as the MU approached 1, the beam output increased up to 2% for 300 MU/min and 4.5% for 600 MU/min, showing a larger overdose as the dose rate increased. Deterioration of the beam symmetry and flatness were also observed as the MU decreased to 1 monitor unit. For the step-and-shoot IMRT case, a large dosimetric error of more than 10% was also detected with the use of a small MU segment. However, no definite correlation with the dose rate was observed due to the combined beam start-up effects by the grid pulse and finite communication time between the machine console and multileaf collimator (MLC) controller. For step-and-shoot IMRT with higher dose rates, beam output and beam profile stability with small MU needs to be checked, and adequate MU limitation where segments are not allowed need to be reflected in the step-and-shoot IMRT planning. PMID:19070251

  19. Consequences of the spectral response of an a-Si EPID and implications for dosimetric calibration

    SciTech Connect

    Kirkby, C.; Sloboda, R.

    2005-08-15

    One of the attractive features of amorphous silicon electronic portal imaging devices (a-Si EPIDs) as dosimetric tools is that for open fields they are known to exhibit a generally linear relation between pixel value and incident energy fluence as measured by an ion chamber. It has also been established that a-Si EPIDs incorporating high atomic number phosphors such as Gd{sub 2}O{sub 2}S:Tb exhibit a disproportionately large response to low-energy (<1 MeV) photons. The present work examines the consequences of this hypersensitivity in a commercially available EPID, the Varian aS500, with respect to energy fluence calibration in a 6 MV radiotherapy beam. EPIDs may be deployed in situations where the spectrum of the incident beam is modified by passing through a compensator or through a patient or phantom. By examining the specific case of a beam hardened by passage through compensator material, we show that the discrepancy between open and attenuated beam calibration curves can be as high as 8%. A Monte Carlo study using a comprehensive model of the aS500 shows that this difference can be explained by spectral changes, and further suggests that it can be reduced by the addition of an external copper plate. We consider configurations with the plate placed directly on top of the EPID cassette and 15 cm above the cassette, supported by Styrofoam. In order to reduce the maximum discrepancy to <4%, it was found that a copper thickness of {approx}0.7 cm was required in the elevated configuration. Improvement was minimal with the copper in the contact configuration. Adding 0.7 cm of copper in the elevated configuration reduced the contrast-to-noise ratio by 19% and the modulation transfer for a given spatial frequency by 30%.

  20. Dosimetric evaluation of simultaneous integrated boost during stereotactic body radiation therapy for pancreatic cancer

    SciTech Connect

    Yang, Wensha; Reznik, Robert; Fraass, Benedick A.; Nissen, Nicholas; Hendifar, Andrew; Wachsman, Ashley; Sandler, Howard; Tuli, Richard

    2015-04-01

    Stereotactic body radiation therapy (SBRT) provides a promising way to treat locally advanced pancreatic cancer and borderline resectable pancreatic cancer. A simultaneous integrated boost (SIB) to the region of vessel abutment or encasement during SBRT has the potential to downstage otherwise likely positive surgical margins. Despite the potential benefit of using SIB-SBRT, the ability to boost is limited by the local geometry of the organs at risk (OARs), such as stomach, duodenum, and bowel (SDB), relative to tumor. In this study, we have retrospectively replanned 20 patients with 25 Gy prescribed to the planning target volume (PTV) and 33~80 Gy to the boost target volume (BTV) using an SIB technique for all patients. The number of plans and patients able to satisfy a set of clinically established constraints is analyzed. The ability to boost vessels (within the gross target volume [GTV]) is shown to correlate with the overlap volume (OLV), defined to be the overlap between the GTV + a 1(OLV1)- or 2(OLV2)-cm margin with the union of SDB. Integral dose, boost dose contrast (BDC), biologically effective BDC, tumor control probability for BTV, and normal tissue complication probabilities are used to analyze the dosimetric results. More than 65% of the cases can deliver a boost to 40 Gy while satisfying all OAR constraints. An OLV2 of 100 cm{sup 3} is identified as the cutoff volume: for cases with OLV2 larger than 100 cm{sup 3}, it is very unlikely the case could achieve 25 Gy to the PTV while successfully meeting all the OAR constraints.

  1. NOTE: Practical and dosimetric implications of a new type of packaging for radiographic film

    NASA Astrophysics Data System (ADS)

    Gillis, S.; DeWagter, C.

    2005-04-01

    Recently, Kodak introduced new light-tight packages (vacuum packaging, aluminium layer under black polyethylene and different paper) for their oncology films (EDR-2, X-Omat V and PPL-2). In order to avoid additional uncertainty and to ensure transferability of previously published results, we assessed in this study the effect of the old and new packages on the dosimetric response of EDR-2 radiographic film. Therefore, sensitometric measurements were performed for different film assemblies (new envelope + new paper, old envelope + old paper, new envelope without paper and old envelope without paper). In addition, to assess possible effects of the package on the film depth dose response, packaged films were irradiated in parallel geometry, and central depth dose curves were retrieved. For the perpendicular geometry, on the other hand, the effect of the package was assessed at large depth for a high intensity-modulated inverse-pyramid beam. The results of the sensitometric measurements reveal no difference between the packages. However, the white colour of the paper in both the packages induces a dose-dependent increase in optical density (0 0.12) of the film. The depth dose curves show better reproducibility for the new package and the new paper improves the accuracy of film dosimetry, but despite the company's effort to evacuate the air out of the new envelope, it remains necessary to clamp the films in the phantom for the parallel irradiation geometry. At 5 cm depth, the films irradiated in parallel geometry show an under-response of 3 5% compared to films irradiated perpendicularly. Finally, even at locations of large photon scatter, no filtration effect from the aluminium layer incorporated in the new envelope has been observed for perpendicular irradiation geometry.

  2. In vivo real-time dosimetric verification in high dose rate prostate brachytherapy

    SciTech Connect

    Seymour, Erin L.; Downes, Simon J.; Fogarty, Gerald B.; Izard, Michael A.; Metcalfe, Peter

    2011-08-15

    Purpose: To evaluate the performance of a diode array in the routine verification of planned dose to points inside the rectum from prostate high dose rate (HDR) brachytherapy using a real-time planning system. Methods: A dosimetric study involving 28 patients was undertaken where measured doses received during treatment were compared to those calculated by the treatment planning system (TPS). After the ultrasound imaging required for treatment planning had been recorded, the ultrasound probe was replaced with a geometric replica that contained an 8 mm diameter cylindrical cavity in which a PTW diode array type 9112 was placed. The replica probe was then positioned inside the rectum with the individual diode positions determined using fluoroscopy. Dose was then recorded during the patients' treatment and compared to associated coordinates in the planning system. Results: Factors influencing diode response and experimental uncertainty were initially investigated to estimate the overall uncertainty involved in dose measurements, which was determined to be {+-}10%. Data was acquired for 28 patients' first fractions, 11 patients' second fractions, and 13 patients' third fractions with collection dependent upon circumstances. Deviations between the diode measurements and predicted values ranged from -42% to +35% with 71% of measurements experiencing less than a 10% deviation from the predicted values. If the {+-}10% measurement uncertainty was combined with a tolerated dose discrepancy of {+-}10% then over 95% of the diode results exhibited agreement with the calculated data to within {+-}20%. It must also be noted that when large dose discrepancies were apparent they did not necessarily occur for all five diodes in the one measurement. Conclusions: This technique provided a method that could be utilized to detect gross errors in dose delivery of a real-time prostate HDR plan. Limitations in the detection system used must be well understood if meaningful results are to

  3. Dosimetric verification of stereotactic radiosurgery/stereotactic radiotherapy dose distributions using Gafchromic EBT3

    SciTech Connect

    Cusumano, Davide; Fumagalli, Maria L.; Marchetti, Marcello; Fariselli, Laura; De Martin, Elena

    2015-10-01

    Aim of this study is to examine the feasibility of using the new Gafchromic EBT3 film in a high-dose stereotactic radiosurgery and radiotherapy quality assurance procedure. Owing to the reduced dimensions of the involved lesions, the feasibility of scanning plan verification films on the scanner plate area with the best uniformity rather than using a correction mask was evaluated. For this purpose, signal values dispersion and reproducibility of film scans were investigated. Uniformity was then quantified in the selected area and was found to be within 1.5% for doses up to 8 Gy. A high-dose threshold level for analyses using this procedure was established evaluating the sensitivity of the irradiated films. Sensitivity was found to be of the order of centiGray for doses up to 6.2 Gy and decreasing for higher doses. The obtained results were used to implement a procedure comparing dose distributions delivered with a CyberKnife system to planned ones. The procedure was validated through single beam irradiation on a Gafchromic film. The agreement between dose distributions was then evaluated for 13 patients (brain lesions, 5 Gy/die prescription isodose ~80%) using gamma analysis. Results obtained using Gamma test criteria of 5%/1 mm show a pass rate of 94.3%. Gamma frequency parameters calculation for EBT3 films showed to strongly depend on subtraction of unexposed film pixel values from irradiated ones. In the framework of the described dosimetric procedure, EBT3 films proved to be effective in the verification of high doses delivered to lesions with complex shapes and adjacent to organs at risk.

  4. Dosimetric Advantages of Midventilation Compared With Internal Target Volume for Radiation Therapy of Pancreatic Cancer

    SciTech Connect

    Lens, Eelco Horst, Astrid van der; Versteijne, Eva; Tienhoven, Geertjan van; Bel, Arjan

    2015-07-01

    Purpose: The midventilation (midV) approach can be used to take respiratory-induced pancreatic tumor motion into account during radiation therapy. In this study, the dosimetric consequences for organs at risk and tumor coverage of using a midV approach compared with using an internal target volume (ITV) were investigated. Methods and Materials: For each of the 18 patients, 2 treatment plans (25 × 2.0 Gy) were created, 1 using an ITV and 1 using a midV approach. The midV dose distribution was blurred using the respiratory-induced motion from 4-dimensional computed tomography. The resulting planning target volume (PTV) coverage for this blurred dose distribution was analyzed; PTV coverage was required to be at least V{sub 95%} >98%. In addition, the change in PTV size and the changes in V{sub 10Gy}, V{sub 20Gy}, V{sub 30Gy}, V{sub 40Gy}, D{sub mean} and D{sub 2cc} for the stomach and for the duodenum were analyzed; differences were tested for significance using the Wilcoxon signed-rank test. Results: Using a midV approach resulted in sufficient target coverage. A highly significant PTV size reduction of 13.9% (P<.001) was observed. Also, all dose parameters for the stomach and duodenum, except the D{sub 2cc} of the duodenum, improved significantly (P≤.002). Conclusions: By using the midV approach to account for respiratory-induced tumor motion, a significant PTV reduction and significant dose reductions to the stomach and to the duodenum can be achieved when irradiating pancreatic tumors.

  5. Computed Tomography Appearance of Early Radiation Injury to the Lung: Correlation With Clinical and Dosimetric Factors

    SciTech Connect

    Jenkins, Peter; Welsh, Anne

    2011-09-01

    Purpose: To systematically assess the spectrum of radiologic changes in the lung after radiation therapy for non-small-cell lung cancer. Methods and Materials: We reviewed the cases of 146 patients treated with radical radiotherapy at our institution. All patients had computed tomography (CT) scans performed 3 months after completion of therapy. Radiographic appearances were categorized using a standard grading system. The association of these abnormalities with pretreatment factors and clinical radiation pneumonitis (RP) was investigated. Results: New intrapulmonary abnormalities were seen in 92 patients (63%). These were ground-glass opacity in 16 (11%), patchy consolidation in 19 (13%), and diffuse consolidation in 57 (39%). Twenty-five patients (17%) developed clinical symptoms of RP. Although 80% of the patients with RP had areas of consolidation seen on the posttreatment CT scan, the majority (74%) of patients with such radiographic changes were asymptomatic. For patients with lung infiltrates, the minimum isodose encompassing the volume of radiologic abnormality was usually {>=}27 Gy. Traditional dose-volume metrics, pulmonary function tests, and the coadministration of angiotensin converting enzyme inhibitors (ACE-I) were all strongly correlated with the presence of radiologic injury on univariate analysis (p {<=} 0.002). There was also an inverse correlation between prior smoking history and CT scan changes (p = 0.02). On multivariate analysis, dosimetric parameters and the use of ACE-I retained significance (p = 0.005). Conclusions: Our findings suggest that there is substantial interindividual variation in lung radiosensitivity. ACE-I prevented the radiologic changes seen after high-dose radiation therapy, and their role as radioprotectants warrants further investigation.

  6. Postoperative radiotherapy following mastectomy for patients with left-sided breast cancer: A comparative dosimetric study

    SciTech Connect

    Wang, Jiahao; Li, Xiadong; Deng, Qinghua; Xia, Bing; Wu, Shixiu; Liu, Jian; Ma, Shenglin

    2015-10-01

    The purposes of this article were to compare the biophysical dosimetry for postmastectomy left-sided breast cancer using 4 different radiotherapy (RT) techniques. In total, 30 patients with left-sided breast cancer were randomly selected for this treatment planning study. They were planned using 4 RT techniques, including the following: (1) 3-dimensional conventional tangential fields (TFs), (2) tangential intensity-modulated therapy (T-IMRT), (3) 4 fields IMRT (4F-IMRT), and (4) single arc volumetric-modulated arc therapy (S-VMAT). The planning target volume (PTV) dose was prescribed 50 Gy, the comparison of target dose distribution, conformity index, homogeneity index, dose to organs at risk (OARs), tumor control probability (TCP), normal tissue complication probability (NTCP), and number of monitor units (MUs) between 4 plans were investigated for their biophysical dosimetric difference. The target conformity and homogeneity of S-VMAT were better than the other 3 kinds of plans, but increased the volume of OARs receiving low dose (V{sub 5}). TCP of PTV and NTCP of the left lung showed no statistically significant difference in 4 plans. 4F-IMRT plan was superior in terms of target coverage and protection of OARs and demonstrated significant advantages in decreasing the NTCP of heart by 0.07, 0.03, and 0.05 compared with TFs, T-IMRT, and S-VMAT plan. Compared with other 3 plans, TFs reduced the average number of MUs. Of the 4 techniques studied, this analysis supports 4F-IMRT as the most appropriate balance of target coverage and normal tissue sparing.

  7. A dosimetric comparison of whole-lung treatment techniques in the pediatric population.

    PubMed

    Bosarge, Christina L; Ewing, Marvene M; DesRosiers, Colleen M; Buchsbaum, Jeffrey C

    2016-01-01

    To demonstrate the dosimetric advantages and disadvantages of standard anteroposterior-posteroanterior (S-AP/PAAAA), inverse-planned AP/PA (IP-AP/PA) and volumetry-modulated arc (VMAT) radiotherapies in the treatment of children undergoing whole-lung irradiation. Each technique was evaluated by means of target coverage and normal tissue sparing, including data regarding low doses. A historical approach with and without tissue heterogeneity corrections is also demonstrated. Computed tomography (CT) scans of 10 children scanned from the neck to the reproductive organs were used. For each scan, 6 plans were created: (1) S-AP/PAAAA using the anisotropic analytical algorithm (AAA), (2) IP-AP/PA, (3) VMAT, (4) S-AP/PANONE without heterogeneity corrections, (5) S-AP/PAPB using the Pencil-Beam algorithm and enforcing monitor units from technique 4, and (6) S-AP/PAAAA[FM] using AAA and forcing fixed monitor units. The first 3 plans compare modern methods and were evaluated based on target coverage and normal tissue sparing. Body maximum and lower body doses (50% and 30%) were also analyzed. Plans 4 to 6 provide a historic view on the progression of heterogeneity algorithms and elucidate what was actually delivered in the past. Averages of each comparison parameter were calculated for all techniques. The S-AP/PAAAA technique resulted in superior target coverage but had the highest maximum dose to every normal tissue structure. The IP-AP/PA technique provided the lowest dose to the esophagus, stomach, and lower body doses. VMAT excelled at body maximum dose and maximum doses to the heart, spine, and spleen, but resulted in the highest dose in the 30% body range. It was, however, superior to the S-AP/PAAAA approach in the 50% range. Each approach has strengths and weaknesses thus associated. Techniques may be selected on a case-by-case basis and by physician preference of target coverage vs normal tissue sparing. PMID:26778010

  8. Stereotactic body radiation therapy for liver tumours using flattening filter free beam: dosimetric and technical considerations

    PubMed Central

    2012-01-01

    Purpose To report the initial institute experience in terms of dosimetric and technical aspects in stereotactic body radiation therapy (SBRT) delivered using flattening filter free (FFF) beam in patients with liver lesions. Methods and Materials From October 2010 to September 2011, 55 consecutive patients with 73 primary or metastatic hepatic lesions were treated with SBRT on TrueBeam using FFF beam and RapidArc technique. Clinical target volume (CTV) was defined on multi-phase CT scans, PET/CT, MRI, and 4D-CT. Dose prescription was 75 Gy in 3 fractions to planning target volume (PTV). Constraints for organs at risk were: 700 cc of liver free from the 15 Gy isodose, Dmax < 21 Gy for stomach and duodenum, Dmax < 30 Gy for heart, D0.1 cc < 18 Gy for spinal cord, V15 Gy < 35% for kidneys. The dose was downscaled in cases of not full achievement of dose constraints. Daily cone beam CT (CBCT) was performed. Results Forty-three patients with a single lesion, nine with two lesions and three with three lesions were treated with this protocol. Target and organs at risk objectives were met for all patients. Mean delivery time was 2.8 ± 1.0 min. Pre-treatment plan verification resulted in a Gamma Agreement Index of 98.6 ± 0.8%. Mean on-line co-registration shift of the daily CBCT to the simulation CT were: -0.08, 0.05 and -0.02 cm with standard deviations of 0.33, 0.39 and 0.55 cm in, vertical, longitudinal and lateral directions respectively. Conclusions SBRT for liver targets delivered by means of FFF resulted to be feasible with short beam on time. PMID:22296849

  9. Dosimetric comparison of IMRT rectal and anal canal plans generated using an anterior dose avoidance structure

    SciTech Connect

    Leicher, Brian; Day, Ellen; Colonias, Athanasios; Gayou, Olivier

    2014-10-01

    To describe a dosimetric method using an anterior dose avoidance structure (ADAS) during the treatment planning process for intensity-modulated radiation therapy (IMRT) for patients with anal canal and rectal carcinomas. A total of 20 patients were planned on the Elekta/CMS XiO treatment planning system, version 4.5.1 (Maryland Heights MO) with a superposition algorithm. For each patient, 2 plans were created: one employing an ADAS (ADAS plan) and the other replanned without an ADAS (non-ADAS plan). The ADAS was defined to occupy the volume between the inguinal nodes and primary target providing a single organ at risk that is completely outside of the target volume. Each plan used the same beam parameters and was analyzed by comparing target coverage, overall plan dose conformity using a conformity number (CN) equation, bowel dose-volume histograms, and the number of segments, daily treatment duration, and global maximum dose. The ADAS and non-ADAS plans were equivalent in target coverage, mean global maximum dose, and sparing of small bowel in low-dose regions (5, 10, 15, and 20 Gy). The mean difference between the CN value for the non-ADAS plans and ADAS plans was 0.04 ± 0.03 (p < 0.001). The mean difference in the number of segments was 15.7 ± 12.7 (p < 0.001) in favor of ADAS plans. The ADAS plan delivery time was shorter by 2.0 ± 1.5 minutes (p < 0.001) than the non-ADAS one. The ADAS has proven to be a powerful tool when planning rectal and anal canal IMRT cases with critical structures partially contained inside the target volume.

  10. Dosimetric properties of improved GafChromic films for seven different digitizers.

    PubMed

    Devic, Slobodan; Seuntjens, Jan; Hegyi, Gyorgy; Podgorsak, Ervin B; Soares, Christopher G; Kirov, Assen S; Ali, Imad; Williamson, Jeffrey F; Elizondo, Angel

    2004-09-01

    Two recently introduced GafChromic film models, HS and XR-T, have been developed as more sensitive and uniform alternatives to GafChromic MD-55-2 film. The HS model has been specifically designed for measurement of absorbed dose in high-energy photon beams (above 1 MeV), while the XR-T model has been introduced for dose measurements of low energy (0.1 MeV) photons. The goal of this study is to compare the sensitometric curves and estimated dosimetric uncertainties associated with seven different GafChromic film dosimetry systems for the two new film models. The densitometers tested are: LKB Pharmacia UltroScan XL, Molecular Dynamics Personal Densitometer, Nuclear Associates Radiochromic Densitometer Model 37-443, Photoelectron Corporation CMR-604, Laser Pro 16, Vidar VXR-16, and AGFA Arcus II document scanner. Pieces of film were exposed to different doses in a dose range from 0.5 to 50 Gy using 6 MV photon beam. Functional forms for dose vs net optical density have been determined for each of the GafChromic film-dosimetry systems used in this comparison. Two sources of uncertainties in dose measurements, governed by the experimental measurement and calibration curve fit procedure, have been compared for the densitometers used. Among the densitometers tested, it is found that for the HS film type the uncertainty caused by the experimental measurement varies from 1% to 3% while the calibration fit uncertainty ranges from 2% to 4% for doses above 5 Gy. Corresponding uncertainties for XR-T film model are somewhat higher and range from 1% to 5% for experimental and from 2% to 7% for the fit uncertainty estimates. Notwithstanding the significant variations in sensitivity, the studied densitometers exhibit very similar precision for GafChromic film based dose measurements above 5 Gy. PMID:15487718

  11. EGSnrc Monte Carlo-aided dosimetric studies of the new BEBIG 60Co HDR brachytherapy source

    PubMed Central

    Akramuzzaman, Mir Md.; Zakaria, Golam Abu

    2013-01-01

    Purpose The purpose of this study is to obtain the dosimetric parameters of the new BEBIG 60Co brachytherapy source following by TG-43U1 recommendation with appropriate electron cutoff energy (0.521 MeV). Material and methods The new BEBIG 60Co brachytherapy source is used to calculate the TG-43U1 parameters. EGSnrc-based Monte Carlo simulation code has been used to calculate the radial dose functions and anisotropy functions. 2D dose rate table is obtained with Cartesian coordinate system for surrounding the source. Results The radial dose functions are calculated for the distance of 0.06 cm to 100 cm from the source center with different cutoff energies and compared. The anisotropy functions values are calculated with the range of 1° to 179°, and apart from 0.2 cm to 20 cm of radial distances. The along-away dose rate data are calculated for quality assurance purposes. The calculated values are compared with the consensus data set and previous published results. Conclusions The radial dose function values from 0.06 cm to 0.16 cm are low, and these values gradually increased up to 0.3 cm radial distance. The radial dose function values are compared with the values of consensus data set using EGSnrc code system, and it is in good agreement with the published data range. The data for < 0.1 cm is not available in consensus data set, and extrapolated value is included for 0 distances which is the same as the value of 0.1 cm. In this study, the obtained values are strictly fall-off to < 0.1 cm distances. Good agreement with the published data was observed, except the values less than 40° angle at 0.5 cm distance for anisotropy function values. PMID:24143150

  12. Evaluation of the dosimetric parameters for 125I brachytherapy determined in prostate medium using CT images.

    PubMed

    Hanada, Takashi; Yorozu, Atsunori; Ohashi, Toshio; Shigematsu, Naoyuki; Maruyama, Koichi

    2010-01-01

    In the present study, the prostate medium determined from the CT images of 149 patients was developed. The dosimetric parameters such as Λ, g(L)(r) and F(r, θ) used in TG-43U1-based calculation for an iodine-125 ((125)I) brachytherapy-source were examined using Monte Carlo code Geant4. Clinical dosimetry parameters such as the D(90) were evaluated among a subgroup of 50 randomly selected patients who had been treated with permanent brachytherapy between January 2008 and December 2008 at the Tokyo Medical Center. The results show a slight difference in the dose rate constant Λ (within 1.0%). The radial dose function g(L)(r) exhibits a prominent difference in the region over 3 cm, and this difference is maintained within 2.9% in the region close to the source. The calculated values of F(r, θ) for the prostate medium were similar to values for water (within 1%), except in the longitudinal axis. A comparison of D(90) values shows a systematic dose overestimation of 2.8 ± 0.7 Gy in water, where the distribution of the differences can be seen with a spread of 1.8 ± 0.3% compared to that in prostate medium. It was concluded that the introduction of any kind of tissue correction for the TG-43U1-based calculation was not necessary to allow for the differences in elemental compositions and densities between water and prostate medium. PACS number: 87.00.00; 87.55.dk; 87.55.K-; 87.56.B-. PMID:20921822

  13. Dosimetric perturbations of a lead shield for surface and interstitial high-dose-rate brachytherapy.

    PubMed

    Candela-Juan, Cristian; Granero, Domingo; Vijande, Javier; Ballester, Facundo; Perez-Calatayud, Jose; Rivard, Mark J

    2014-06-01

    In surface and interstitial high-dose-rate brachytherapy with either (60)Co, (192)Ir, or (169)Yb sources, some radiosensitive organs near the surface may be exposed to high absorbed doses. This may be reduced by covering the implants with a lead shield on the body surface, which results in dosimetric perturbations. Monte Carlo simulations in Geant4 were performed for the three radionuclides placed at a single dwell position. Four different shield thicknesses (0, 3, 6, and 10 mm) and three different source depths (0, 5, and 10 mm) in water were considered, with the lead shield placed at the phantom surface. Backscatter dose enhancement and transmission data were obtained for the lead shields. Results were corrected to account for a realistic clinical case with multiple dwell positions. The range of the high backscatter dose enhancement in water is 3 mm for (60)Co and 1 mm for both (192)Ir and (169)Yb. Transmission data for (60)Co and (192)Ir are smaller than those reported by Papagiannis et al (2008 Med. Phys. 35 4898-4906) for brachytherapy facility shielding; for (169)Yb, the difference is negligible. In conclusion, the backscatter overdose produced by the lead shield can be avoided by just adding a few millimetres of bolus. Transmission data provided in this work as a function of lead thickness can be used to estimate healthy organ equivalent dose saving. Use of a lead shield is justified. PMID:24705066

  14. SU-F-BRD-11: Prediction of Dosimetric Endpoints From Patient Geometry Using Neural Nets

    SciTech Connect

    O'Connell, D; Chow, P; Agazaryan, N; Jani, S; Low, D; Lamb, J

    2014-06-15

    Purpose: The previously-published overlap volume histogram (OVH) technique lends itself naturally to prediction of the dose received by a given volume of tissue (e.g. D90) in intensity-modulated radiotherapy (IMRT) treatment plans. Here we extend the OVH technique using artificial neural networks in order to predict the volume of tissue receiving a given dose (e.g. V90) in both prostate IMRT and conventional breast radiotherapy. Methods: Twenty-nine prostate treatment plans and forty-three breast treatment plans were analyzed. The spatial relationships between the prostate and rectum and between the breast and ipsilateral lung were characterized using OVHs. The OVH is a cumulative histogram representing the fractional volume of the risk organ overlapped by a series of isotropic expansions of the planning target volume (PTV). Seven cases were identified as outliers and replanned. OVH points were used as inputs to a one hidden layer feed forward artificial neural network with quality parameters of the corresponding plan, such as the rectum V50, as targets. A 3-fold cross-validation was used to estimate the prediction error. Results: The root mean square (RMS) error between the predicted rectum V50s and the planned values was 2.3, which was 35% of the standard deviation of V50 for the twenty-nine plans. The RMS error of prediction of V20 of the ipsilateral lung in breast cases was 3.9, which was 90% of the standard deviation of the V20 values in the breast plan database. Conclusion: This study demonstrates that artificial neural nets can be used to extend the OVH technique to predict dosimetric endpoints taking the form of a volume receiving a given dose, rather than the minimum dose received by a given volume. Prediction of ipsilateral lung dose in breast radiotherapy using the OVH technique remains a work in progress.

  15. Radioiodine therapy in patients with hyperthyroid disorder: standard versus dosimetric activity application.

    PubMed

    Reinartz, P; Zimny, M; Schaefer, W; Mueller, B; Buell, U; Sabri, O

    2003-12-01

    Due to its high success rate and non-invasive character, an increasing demand for radioiodine therapy can be seen. This study was conducted to determine whether standardized 131I activities can be used to facilitate management of patients with hyperthyroid disorder or whether a pre-therapeutic radioiodine test is advisable to determine an adequate therapeutic activity. The therapeutic uptake of 218 patients with benign thyroid disorders were determined and compared with 24 h and 48 h test uptake measurements as well as with calculated standard uptake values. Since there is a linear relationship between iodine uptake and delivered radiation dose, the effect of the different therapeutic approaches on the latter parameter was analysed. Special care was taken to assess possible differences between the various thyroid disorders. A mean deviation between pre-therapeutic test uptake and actual therapeutic uptake of 14.7% was observed in contrast to one of 29.1% when using disease specific standard values per millilitre of thyroid tissue. Furthermore, the proportion of patients with large deviations of more than 40% increased drastically when using standard uptake values (with radioiodine test, 4.1%; with standard values, 18.8%). In conclusion, the dosimetric approach with a pre-therapeutic radioiodine test proved to be the most accurate therapeutic procedure. Both the 24 h and 48 h test uptake measurements gave analogous results and yielded a correlation coefficient of 0.91 when compared with the therapeutic uptake. While it may be tempting to use standard activities to facilitate patient management, the findings of this study confirm that, for precise therapy planning, a pre-therapeutic radioiodine test is advised. Since no significant difference could be found between the 24 h and 48 h test uptake values, an early measurement 24 h after administration of the test activity is recommended. PMID:14627852

  16. Dosimetric characterization and optimization of a customized Stanford total skin electron irradiation (TSEI) technique.

    PubMed

    Luĉić, Felipe; Sánchez-Nieto, Beatriz; Caprile, Paola; Zelada, Gabriel; Goset, Karen

    2013-01-01

    Total skin electron irradiation (TSEI) has been used as a treatment for mycosis fungoides. Our center has implemented a modified Stanford technique with six pairs of 6 MeV adjacent electron beams, incident perpendicularly on the patient who remains lying on a translational platform, at 200 cm from the source. The purpose of this study is to perform a dosimetric characterization of this technique and to investigate its optimization in terms of energy characteristics, extension, and uniformity of the treatment field. In order to improve the homogeneity of the distribution, a custom-made polyester filter of variable thickness and a uniform PMMA degrader plate were used. It was found that the characteristics of a 9 MeV beam with an 8 mm thick degrader were similar to those of the 6 MeV beam without filter, but with an increased surface dose. The combination of the degrader and the polyester filter improved the uniformity of the distribution along the dual field (180cm long), increasing the dose at the borders of field by 43%. The optimum angles for the pair of beams were ± 27°. This configuration avoided displacement of the patient, and reduced the treatment time and the positioning problems related to the abutting superior and inferior fields. Dose distributions in the transversal plane were measured for the six incidences of the Stanford technique with film dosimetry in an anthropomorphic pelvic phantom. This was performed for the optimized treatment and compared with the previously implemented technique. The comparison showed an increased superficial dose and improved uniformity of the 85% isodose curve coverage for the optimized technique. PMID:24036877

  17. Dosimetric evaluation of sucrose and granulated cane sugar in the therapeutic dose range

    SciTech Connect

    Davidson, Melanie T. M.; Jordan, Kevin J.

    2009-04-15

    Granulated cane sugar has been used as a dosimetric material to report dose in high dose accidental irradiations. The purpose of this study was to assess whether clinical dosimetry is also plausible with such a commonly available material. The behavior of cane sugar was explored with respect to therapeutically relevant radiation quantities (dose, dose rate) and qualities (energy, radiation type) as well as under different temperature conditions. The stability of the signal postirradiation was also measured. Absorbed dose was measured by spectrophotometric readout of a ferrous ammonium sulfate xylenol orange (FX)-sugar solution in 10 cm path length cells. A visible color change was produced as a function of dose when the irradiated sugar samples were dissolved in FX solution (10% dilution by mass). A comparison of the optical absorbance spectra and dose response of cane sugar with analytical grade sucrose was done to establish a benchmark standard from which subsequent dosimetry measurements can be validated. The response of the sugar dosimeter read at 590 nm was found to be linear over the dose range of 100-2000 cGy, independent of energy (6-18 MV) and of the average dose rate (100-500 cGy/min). The readout of sugar samples irradiated with mixed photon and electron fields was also shown to be independent of radiation type (photons and electrons). Sugar temperature (20-40 degree sign C) during irradiation did not affect dose estimates, making it a promising dosimeter for in vivo dosimetry, particularly in cases where the dosimeter must remain in contact with the patient for an extended period of time. Sugar can be used as an integrating dosimeter, since it exhibits no fractionation effects. Granulated cane sugar is cost effective, safe, soft tissue equivalent, and can be used under various experimental conditions, making it a suitable dosimeter for some radiotherapy applications.

  18. Fractionated stereotactic radiotherapy: A method to evaluate geometric and dosimetric uncertainties using radiochromic films

    SciTech Connect

    Coscia, Gianluca; Vaccara, Elena; Corvisiero, Roberta; Cavazzani, Paolo; Ruggieri, Filippo Grillo; Taccini, Gianni

    2009-07-15

    In the authors' hospital, stereotactic radiotherapy treatments are performed with a Varian Clinac 600C equipped with a BrainLAB m3 micro-multileaf-collimator generally using the dynamic conformal arc technique. Patient immobilization during the treatment is achieved with a fixation mask supplied by BrainLAB, made with two reinforced thermoplastic sheets fitting the patient's head. With this work the authors propose a method to evaluate treatment geometric accuracy and, consequently, to determine the amount of the margin to keep in the CTV-PTV expansion during the treatment planning. The reproducibility of the isocenter position was tested by simulating a complete treatment on the anthropomorphic phantom Alderson Rando, inserting in between two phantom slices a high sensitivity Gafchromic EBT film, properly prepared and calibrated, and repeating several treatment sessions, each time removing the fixing mask and replacing the film inside the phantom. The comparison between the dose distributions measured on films and computed by TPS, after a precise image registration procedure performed by a commercial piece of software (FILMQA, 3cognition LLC (Division of ISP), Wayne, NJ), allowed the authors to measure the repositioning errors, obtaining about 0.5 mm in case of central spherical PTV and about 1.5 mm in case of peripheral irregular PTV. Moreover, an evaluation of the errors in the registration procedure was performed, giving negligible values with respect to the quantities to be measured. The above intrinsic two-dimensional estimate of treatment accuracy has to be increased for the error in the third dimension, but the 2 mm margin the authors generally use for the CTV-PTV expansion seems adequate anyway. Using the same EBT films, a dosimetric verification of the treatment planning system was done. Measured dose values are larger or smaller than the nominal ones depending on geometric irradiation conditions, but, in the authors' experimental conditions, always

  19. Fractionated stereotactic radiotherapy: a method to evaluate geometric and dosimetric uncertainties using radiochromic films.

    PubMed

    Coscia, Gianluca; Vaccara, Elena; Corvisiero, Roberta; Cavazzani, Paolo; Ruggieri, Filippo Grillo; Taccini, Gianni

    2009-07-01

    In the authors' hospital, stereotactic radiotherapy treatments are performed with a Varian Clinac 600C equipped with a BrainLAB m3 micro-multileaf-collimator generally using the dynamic conformal arc technique. Patient immobilization during the treatment is achieved with a fixation mask supplied by BrainLAB, made with two reinforced thermoplastic sheets fitting the patient's head. With this work the authors propose a method to evaluate treatment geometric accuracy and, consequently, to determine the amount of the margin to keep in the CTV-PTV expansion during the treatment planning. The reproducibility of the isocenter position was tested by simulating a complete treatment on the anthropomorphic phantom Alderson Rando, inserting in between two phantom slices a high sensitivity Gafchromic EBT film, properly prepared and calibrated, and repeating several treatment sessions, each time removing the fixing mask and replacing the film inside the phantom. The comparison between the dose distributions measured on films and computed by TPS, after a precise image registration procedure performed by a commercial piece of software (FILMQA, 3cognition LLC (Division of ISP), Wayne, NJ), allowed the authors to measure the repositioning errors, obtaining about 0.5 mm in case of central spherical PTV and about 1.5 mm in case of peripheral irregular PTV. Moreover, an evaluation of the errors in the registration procedure was performed, giving negligible values with respect to the quantities to be measured. The above intrinsic two-dimensional estimate of treatment accuracy has to be increased for the error in the third dimension, but the 2 mm margin the authors generally use for the CTV-PTV expansion seems adequate anyway. Using the same EBT films, a dosimetric verification of the treatment planning system was done. Measured dose values are larger or smaller than the nominal ones depending on geometric irradiation conditions, but, in the authors' experimental conditions, always

  20. Photon buildup factors in some dosimetric materials for heterogeneous radiation sources.

    PubMed

    Kurudirek, Murat

    2014-03-01

    Effective photon energy absorption (EABF(eff)) and exposure buildup factors (EBF(eff)) have been calculated based on the effective energy concept, for some dosimetric materials such as water, polymethyl methacrylate (PMMA), polystyrene, solid water (WT1), RW3 (Goettingen Water 3), and ABS (acrylonitrile butadiene styrene), for MV X-rays and (60)Co gamma rays. Firstly, the equivalent atomic numbers (Z(eq)) of the given materials have been determined using the effective photon energies (E eff). Then, the five-parameter geometric progression (G-P) fitting approximation has been used to calculate both EABF(eff) and EBF(eff) values. Since the G-P fitting parameters are not available for the E eff values of the given materials, a linear interpolation in which a function of the logarithm of the variable is used has been performed, in order to calculate the parameters in each E eff, which will be further used for the determination of EABF(eff) and EBF(eff). In the present paper, water equivalence properties of the given materials are also discussed based on the effective buildup factors. In this study, special emphasis is placed on the calculation of EABF(eff) and EBF(eff) values of different materials for photons that are not monoenergetic but heterogeneous in energy, to obtain an initial and prior knowledge of the probable energy and buildup of photons at locations of interest, i.e., to understand whether the real absorbed dose occurs at the surface or somewhere inside the medium of interest. PMID:24287785

  1. Development and Dosimetric Characterization of a Tissue Substitute (Bolus) For Use in Linear Accelerator Electron Radiotherapy

    NASA Astrophysics Data System (ADS)

    Estrada Trujillo, Jorge; Villaseñor Navarro, Luis Felipe; Mitsoura, Eleni

    2003-09-01

    We propose the design of a new custom made material, to be used as a tissue substitute in external beam electron radiotherapy, based on cotton fabric and beeswax. Due to its inexpensive, easy preparation, constant thickness, flexibility, uniform density and physical properties similar to those of soft tissue, this bolus will insure personalized optimal dose build up and dose distribution in irregular treatment regions. Materials and Methods: We used commercial Campeche beeswax and 100% cotton fabric to prepare the bolus. Beeswax's physical characteristics were determined by thermal and density analysis. Its chemical properties are to be determined by electronic microcopy. We performed quality control tests and calibration of the Varian 2100C linear accelerator. The tissue equivalence of the material is established for a range of electron energies (6, 9, 12, 16, 20 MeV) using a water equivalent solid phantom (PTW; Freiburg, Germany) and a plane parallel ionization chamber (PTW) associated to a PTW electrometer. Results: Beeswax's absolute density was found to be 0.9181g/ml at 21°C, with a melting point of 45°C. For the bolus elaboration, the cotton fabric was soaked in liquid beeswax and thin sheets of approximately 1 mm were obtained. These presented high flexibility, physical stability (color, texture, thickness) and homogeneity. Determination of this dosimetric characteristics and equivalent thickness are still in process. Discussion and conclusions: Our preliminary results suggest that the tissue substitute is easily made, inexpensive to produce, molds well to the treatment area and its positioning is easy and reproducible over the course of the treatment. So we consider that it's a good alternative to the commercial bolus.

  2. Postoperative radiotherapy following mastectomy for patients with left-sided breast cancer: A comparative dosimetric study.

    PubMed

    Wang, Jiahao; Li, Xiadong; Deng, Qinghua; Xia, Bing; Wu, Shixiu; Liu, Jian; Ma, Shenglin

    2015-01-01

    The purposes of this article were to compare the biophysical dosimetry for postmastectomy left-sided breast cancer using 4 different radiotherapy (RT) techniques. In total, 30 patients with left-sided breast cancer were randomly selected for this treatment planning study. They were planned using 4 RT techniques, including the following: (1) 3-dimensional conventional tangential fields (TFs), (2) tangential intensity-modulated therapy (T-IMRT), (3) 4 fields IMRT (4F-IMRT), and (4) single arc volumetric-modulated arc therapy (S-VMAT). The planning target volume (PTV) dose was prescribed 50Gy, the comparison of target dose distribution, conformity index, homogeneity index, dose to organs at risk (OARs), tumor control probability (TCP), normal tissue complication probability (NTCP), and number of monitor units (MUs) between 4 plans were investigated for their biophysical dosimetric difference. The target conformity and homogeneity of S-VMAT were better than the other 3 kinds of plans, but increased the volume of OARs receiving low dose (V5). TCP of PTV and NTCP of the left lung showed no statistically significant difference in 4 plans. 4F-IMRT plan was superior in terms of target coverage and protection of OARs and demonstrated significant advantages in decreasing the NTCP of heart by 0.07, 0.03, and 0.05 compared with TFs, T-IMRT, and S-VMAT plan. Compared with other 3 plans, TFs reduced the average number of MUs. Of the 4 techniques studied, this analysis supports 4F-IMRT as the most appropriate balance of target coverage and normal tissue sparing. PMID:25534167

  3. Dosimetric and toxicity comparison between prone and supine position IMRT for endometrial cancer

    SciTech Connect

    Beriwal, Sushil . E-mail: beriwals@upmc.edu; Jain, Sheena K.; Heron, Dwight E.; De Andrade, Regiane S.; Lin, Chyonghiou J.; Kim, Hayeon

    2007-02-01

    Purpose: To determine the dosimetric and toxicity differences between prone and supine position intensity-modulate radiotherapy in endometrial cancer patients treated with adjuvant radiotherapy. Methods: Forty-seven consecutive endometrial cancer patients treated with adjuvant RT were analyzed. Of these, 21 were treated in prone position and 26 in the supine position. Dose-volume histograms for normal tissue structures and targets were compared between the two groups. Acute and chronic toxicity were also compared between the cohorts. Results: The percentage of volume receiving 10, 20, 30, 40, 45, and 50 Gy for small bowel was 89.5%, 69%, 33%, 12.2%, 5%, and 0% in the prone group and 87.5%, 62.7%, 26.4%, 8%, 4.3%, and 0% in the supine group, respectively. The difference was not statistically significant. The dose-volume histograms for bladder and rectum were also comparable, except for a slightly greater percentage of volume receiving 10 Gy (1.5%) and 20 Gy (5%) for the rectum in the prone group. Acute small bowel toxicities were Grade 1 in 7 patients and Grade 2 in 14 patients in the prone group vs. Grade 1 in 6 patients and Grade 2 in 19 patients in the supine group. Chronic toxicity was Grade 1 in 7 patients and Grade 3 in 1 patient in the prone group and Grade 1 in 5 patients in the supine group. Conclusion: These preliminary results suggest that no difference exists in the dose to the normal tissue and toxicity between prone and supine intensity-modulated radiotherapy for endometrial cancer. Longer follow-up and more outcome studies are needed to determine whether any differences exist between the two approaches.

  4. Dosimetric quality control of Eclipse treatment planning system using pelvic digital test object

    NASA Astrophysics Data System (ADS)

    Benhdech, Yassine; Beaumont, Stéphane; Guédon, Jeanpierre; Crespin, Sylvain

    2011-03-01

    Last year, we demonstrated the feasibility of a new method to perform dosimetric quality control of Treatment Planning Systems in radiotherapy, this method is based on Monte-Carlo simulations and uses anatomical Digital Test Objects (DTOs). The pelvic DTO was used in order to assess this new method on an ECLIPSE VARIAN Treatment Planning System. Large dose variations were observed particularly in air and bone equivalent material. In this current work, we discuss the results of the previous paper and provide an explanation for observed dose differences, the VARIAN Eclipse (Anisotropic Analytical) algorithm was investigated. Monte Carlo simulations (MC) were performed with a PENELOPE code version 2003. To increase efficiency of MC simulations, we have used our parallelized version based on the standard MPI (Message Passing Interface). The parallel code has been run on a 32- processor SGI cluster. The study was carried out using pelvic DTOs and was performed for low- and high-energy photon beams (6 and 18MV) on 2100CD VARIAN linear accelerator. A square field (10x10 cm2) was used. Assuming the MC data as reference, χ index analyze was carried out. For this study, a distance to agreement (DTA) was set to 7mm while the dose difference was set to 5% as recommended in the TRS-430 and TG-53 (on the beam axis in 3-D inhomogeneities). When using Monte Carlo PENELOPE, the absorbed dose is computed to the medium, however the TPS computes dose to water. We have used the method described by Siebers et al. based on Bragg-Gray cavity theory to convert MC simulated dose to medium to dose to water. Results show a strong consistency between ECLIPSE and MC calculations on the beam axis.

  5. Dosimetric Comparison of Tandem and Ovoids vs. Tandem and Ring for Intracavitary Gynecologic Applications

    SciTech Connect

    Levin, Daphne Menhel, Janna; Rabin, Tanya; Pfeffer, M. Raphael; Symon, Zvi

    2008-01-01

    We evaluated dosimetric differences in tandem and ovoid (TO) and tandem and ring (TR) gynecologic brachytherapy applicators. Seventeen patients with cervical cancer (Stages II-IV) receiving 3 high-dose-rate (HDR) brachytherapy applications (both TO and TR) were studied. Patients underwent computed tomography (CT) scans with contrast in bladder, and were prescribed 8 Gy to ICRU points A, with additional optimization goals of maintaining the pear-shaped dose distribution and minimizing bladder and rectum doses. Bladder and rectum point doses, mean, and maximum doses were calculated. Total treatment time and volumes treated to 95%, 85%, 50%, and 20% or the prescription dose were compared. There were no significant differences between TO and TR applicators in doses to prescription points or critical organs. However, there were significant differences (p < 0.001) between the applicators in treated volumes and total treatment time. The TO treated larger volumes over a longer time. Within each patient, when the applicators were compared, treated volumes were also found to be significantly different (p < 0.01, {chi}{sup 2}). Our results demonstrate that the 2 applicators, while delivering the prescribed dose to points A and keeping critical organ doses below tolerance, treat significantly different volumes. It is unclear if this difference is clinically meaningful. TO applicators may be treating surrounding healthy tissue unnecessarily, or TR applicators may be underdosing tumor tissue. Further investigation with appropriate imaging modalities is required for accurate delineation of target volumes. Clearly, the TO and TR are not identical, and should not be used interchangeably without further study.

  6. 3D-Conformal Versus Intensity-Modulated Postoperative Radiotherapy of Vaginal Vault: A Dosimetric Comparison

    SciTech Connect

    Cilla, Savino; Macchia, Gabriella Digesu, Cinzia; Deodato, Francesco; Romanella, Michele; Ferrandina, Gabriella; Padula, Gilbert; Picardi, Vincenzo; Scambia, Giovanni; Morganti, Alessio Giuseppe

    2010-07-01

    We evaluated a step-and-shoot IMRT plan in the postoperative irradiation of the vaginal vault compared with equispaced beam arrangements (3-5) 3D-radiotherapy (RT) optimized plans. Twelve patients were included in this analysis. Four plans for each patient were compared in terms of dose-volume histograms, homogeneity index (HI), and conformity index (CI): (1) 3 equispaced beam arrangement 3D-RT; (2) 4 equispaced beam arrangement 3D-RT; (3) 5 equispaced beam arrangement 3D-RT; (4) step-and-shoot IMRT technique. CI showed a good discrimination between the four plans. The mean scores of CI were 0.58 (range: 0.38-0.67) for the 3F-CRT plan, 0.58 (range: 0.41-0.66) for 4F-CRT, 0.62 (range: 0.43-0.68) for 5F-CRT and 0.69 (range: 0.58-0.78) for the IMRT plan. A significant improvement of the conformity was reached by the IMRT plan (p < 0.001 for all comparisons). As expected, the increment of 3D-CRT fields was associated with an improvement of target dose conformity and homogeneity; on the contrary, in the IMRT plans, a better conformity was associated to a worse target dose homogeneity. A significant reduction in terms of D{sub mean}, V90%, V95%, V100% was recorded for rectal and bladder irradiation with the IMRT plan. Surprisingly, IMRT supplied a significant dose reduction also for rectum and bladder V30% and V50%. A significant dosimetric advantage of IMRT over 3D-RT in the adjuvant treatment of vaginal vault alone in terms of treatment conformity and rectum and bladder sparing is shown.

  7. Dosimetric characteristics of the Leipzig surface applicators used in the high dose rate brachy radiotherapy

    SciTech Connect

    Niu Hongquan; Hsi, Wen C.; Chu, James C.H.; Kirk, Michael C.; Kouwenhoven, Erik

    2004-12-01

    The nucletron Leipzig applicator is designed for (HDR) {sup 192}Ir brachy radiotherapy of surface lesions. The dosimetric characteristics of this applicator were investigated using simulation method based on Monte Carlo N-particle (MCNP) code and phantom measurements. The simulation method was validated by comparing calculated dose rate distributions of nucletron microSelectron HDR {sup 192}Ir source against published data. Radiochromic films and metal-oxide-semiconductor field-effect transistor (MOSFET) detectors were used for phantom measurements. The double exposure technique, correcting the nonuniform film sensitivity, was applied in the film dosimetry. The linear fit of multiple readings with different irradiation times performed for each MOSFET detector measurement was used to obtain the dose rate of each measurement and to correct the source transit-time error. The film and MOSFET measurements have uncertainties of 3%-7% and 3%-5%, respectively. The dose rate distributions of the Leipzig applicator with 30 mm opening calculated by the validated MC method were verified by measurements of film and MOSFET detectors. Calculated two-dimensional planar dose rate distributions show similar patterns as the film measurement. MC calculated dose rate at a reference point defined at depth 5 mm on the applicator's central axis is 7% lower than the film and 3% higher than the MOSFET measurements. The dose rate of a Leipzig applicator with 30 mm opening at reference point is 0.241{+-}3% cGy h{sup -1} U{sup -1}. The MC calculated depth dose rates and profiles were tabulated for clinic use.

  8. Effects of alignment of adjustable collimator on dosimetric parameters of a telecobalt machine.

    PubMed

    Sahani, G; Sharma, S D; Dash Sharma, P K; Sharma, D N; Hussain, S A

    2013-04-01

    The objectives of this study was to investigate the most appropriate hinge point for the alignment of adjustable collimators/trimmer bars in a telecobalt machine for obtaining acceptable dosimetric parameters of a telecobalt machine. Variations of relative output of the telecobalt machine with selection of different hinge points were also investigated. MCNP code was used for the present the study. A water phantom of dimension 50 x 50 x 40 cm(3) having voxels each of volume 0.72 cm(3) was used in our study for generating beam profiles and depth dose curves. When hinge points are selected at the periphery of the source bottom and the source top, flatness, symmetry and penumbra were found to be well within the recommended tolerance limits whereas values are far beyond with the hinge points selected at the centre of source bottom or the source top. Moreover, it was observed that the relative output of a telecobalt machine with hinge points at centre of the source bottom and the source top are appreciably lower than that of at periphery of source bottom particularly for smaller field sizes. This effect is due to the blockage of the part of the source volume in the radiation field. Therefore, hinge point for the alignment of adjustable collimators/trimmer bars should be selected either at periphery of source bottom or the source top for obtaining clinically acceptable flatness, symmetry and penumbra. However, selecting hinge point at the periphery of the source bottom for the alignment of the adjustable collimators/trimmer bars would be more appropriate as height of the source will vary depending on activity of the source used in the source capsule for given specific activity. PMID:23098284

  9. Evaluation of the dosimetric accuracy for a couch-based tracking system (CBTS)

    NASA Astrophysics Data System (ADS)

    Chang, Kyung Hwan; Lee, Suk; Kim, Kwang Hyeon; Shim, Jang Bo; Yang, Dae Sik; Park, Young Je; Yoon, Won Sup; Kim, Chul Yong; Cao, Yuanjie

    2016-07-01

    In this study, the geometric and dosimetric accuracy of an in-house-developed couch-based tracking system (CBTS) was investigated using both film and in-house-developed polymer gel dosimeters. We evaluated the 1D and the 2D motion accuracies of our couch system by using Gafchromic EBT film. For the 1D test, the couch system was moved 5, 10, and 20 mm in the X, Y, and Z directions, respectively. Meanwhile, for the 2D test, it was moved along the XY, YZ, and ZX directions. We compared the profiles, full widths at half maximum (FWHMs), and penumbras between the static and the tracking fields. For the 3D test, we quantitatively compared the dose distribution between the static and the tracking fields by using the polymer gel dosimeter when it was simultaneously moved in the XYZ directions. We confirmed that the film was moved according to motion amplitudes of 5, 10, and 20 mm in the X, Y, and Z directions, respectively, in the 1D and 2D motion tests. The value of the FWHM of the static field and the three tracking fields were 51.88, 53.28, 57.67, and 64.43 mm, respectively. Two types of penumbras became wider with increasing amplitudes compared to the static field. For the 3D test, the dose distribution of the XYZ tracking field was qualitatively larger than that of the static field. We conclude that this CBTS has the potential for pre-clinical applications in adaptive radiation therapy.

  10. Dosimetric and Late Radiation Toxicity Comparison Between Iodine-125 Brachytherapy and Stereotactic Radiation Therapy for Juxtapapillary Choroidal Melanoma

    SciTech Connect

    Krema, Hatem

    2013-07-01

    Purpose: To compare the dose distributions and late radiation toxicities for {sup 125}I brachytherapy (IBT) and stereotactic radiation therapy (SRT) in the treatment of juxtapapillary choroidal melanoma. Methods: Ninety-four consecutive patients with juxtapapillary melanoma were reviewed: 30 have been treated with IBT and 64 with SRT. Iodine-125 brachytherapy cases were modeled with plaque simulator software for dosimetric analysis. The SRT dosimetric data were obtained from the Radionics XKnife RT3 software. Mean doses at predetermined intraocular points were calculated. Kaplan-Meier estimates determined the actuarial rates of late toxicities, and the log–rank test compared the estimates. Results: The median follow-up was 46 months in both cohorts. The 2 cohorts were balanced with respect to pretreatment clinical and tumor characteristics. Comparisons of radiation toxicity rates between the IBT and SRT cohorts yielded actuarial rates at 50 months for cataracts of 62% and 75% (P=.1), for neovascular glaucoma 8% and 47% (P=.002), for radiation retinopathy 59% and 89% (P=.0001), and for radiation papillopathy 39% and 74% (P=.003), respectively. Dosimetric comparisons between the IBT and SRT cohorts yielded mean doses of 12.8 and 14.1 Gy (P=.56) for the lens center, 17.6 and 19.7 Gy (P=.44) for the lens posterior pole, 13.9 and 10.8 Gy (P=.30) for the ciliary body, 61.9 and 69.7 Gy (P=.03) for optic disc center, and 48.9 and 60.1 Gy (P<.0001) for retina at 5-mm distance from tumor margin, respectively. Conclusions: Late radiation-induced toxicities were greater with SRT, which is secondary to the high-dose exposure inherent to the technique as compared with IBT. When technically feasible, IBT is preferred to treat juxtapapillary choroidal melanoma.

  11. Volumetric modulated arc radiotherapy sparing the thyroid gland for early-stage glottic cancer: A dosimetrical analysis

    PubMed Central

    KIM, EUN SEOK; YEO, SEUNG-GU

    2014-01-01

    Previous studies on advanced radiotherapy (RT) techniques for early stage glottic cancer have focused on sparing the carotid artery. However, the aim of the present study was to evaluate the dosimetric advantages of volumetric modulated arc therapy (VMAT) in terms of sparing the thyroid gland in early-stage glottic cancer patients. In total, 15 cT1N0M0 glottic cancer patients treated with definitive RT using VMAT were selected, and for dosimetric comparison, a conventional RT plan comprising opposed-lateral wedged fields was generated for each patient. The carotid artery, thyroid gland and spinal cord were considered organs at risk. The prescription dose was 63 Gy at 2.25 Gy per fraction. For the thyroid gland and carotid artery, all compared parameters were significantly lower with VMAT compared with conventional RT. For the thyroid gland, the median reduction rates of the mean dose (Dmean), the volume receiving ≥30% of the prescription dose (V30) and the V50 were 32.6, 40.9 and 46.0%, respectively. The Dmean was 14.7±2.6 Gy when using VMAT compared with 22.2±3.9 Gy when using conventional RT. The differences between the techniques in terms of planning target volume coverage and dose homogeneity were not significant. When considering a recent normal tissue complication probability model, which indicated the mean thyroid gland dose as the most significant predictor of radiation-induced hypothyroidism, the dosimetric advantage shown in this study may be valuable in reducing hypothyroidism following RT for early stage glottic cancer patients. PMID:24932276

  12. SU-F-BRE-04: Construction of 3D Printed Patient Specific Phantoms for Dosimetric Verification Measurements

    SciTech Connect

    Ehler, E; Higgins, P; Dusenbery, K

    2014-06-15

    Purpose: To validate a method to create per patient phantoms for dosimetric verification measurements. Methods: Using a RANDO phantom as a substitute for an actual patient, a model of the external features of the head and neck region of the phantom was created. A phantom was used instead of a human for two reasons: to allow for dosimetric measurements that would not be possible in-vivo and to avoid patient privacy issues. Using acrylonitrile butadiene styrene thermoplastic as the building material, a hollow replica was created using the 3D printer filled with a custom tissue equivalent mixture of paraffin wax, magnesium oxide, and calcium carbonate. A traditional parallel-opposed head and neck plan was constructed. Measurements were performed with thermoluminescent dosimeters in both the RANDO phantom and in the 3D printed phantom. Calculated and measured dose was compared at 17 points phantoms including regions in high and low dose regions and at the field edges. On-board cone beam CT was used to localize both phantoms within 1mm and 1° prior to radiation. Results: The maximum difference in calculated dose between phantoms was 1.8% of the planned dose (180 cGy). The mean difference between calculated and measured dose in the anthropomorphic phantom and the 3D printed phantom was 1.9% ± 2.8% and −0.1% ± 4.9%, respectively. The difference between measured and calculated dose was determined in the RANDO and 3D printed phantoms. The differences between measured and calculated dose in each respective phantom was within 2% for 12 of 17 points. The overlap of the RANDO and 3D printed phantom was 0.956 (Jaccard Index). Conclusion: A custom phantom was created using a 3D printer. Dosimetric calculations and measurements showed good agreement between the dose in the RANDO phantom (patient substitute) and the 3D printed phantom.

  13. Dosimetric Comparison of Helical Tomotherapy and Linac-IMRT Treatment Plans for Head and Neck Cancer Patients

    SciTech Connect

    Zhang Xin; Penagaricano, Jose; Moros, Eduardo G.; Corry, Peter M.; Yan Yulong; Ratanatharathorn, Vaneerat

    2010-01-01

    The rapid development and clinical implementation of external beam radiation treatment technologies continues. The existence of various commercially available technologies for intensity-modulated radiation therapy (IMRT) has stimulated interest in exploring the differential potential advantage one may have compared with another. Two such technologies, Hi-Art Helical Tomotherapy (HT) and conventional medical linear accelerator-based IMRT (LIMRT) have been shown to be particularly suitable for the treatment of head and neck cancers. In this study, 23 patients who were diagnosed with stages 3 or 4 head and neck cancers, without evidence of distance metastatic disease, were treated in our clinic. Treatment plans were developed for all patients simultaneously on the HT planning station and on the Pinnacle treatment planning system for step-and-shoot IMRT. Patients were treated only on the HT unit, with the LIMRT plan serving as a backup in case the HT system might not be available. All plans were approved for clinical use by a physician. The prescription was that patients receive at least 95% of the planning target volume (PTV), which is 66 Gy at 2.2 Gy per fraction. Several dosimetric parameters were computed: PTV dose coverage; PTV volume conformity index; the normalized total dose (NTD), where doses were converted to 2 Gy per fraction to organs at risk (OAR); and PTV dose homogeneity. Both planning systems satisfied our clinic's PTV prescription requirements. The results suggest that HT plans had, in general, slightly better dosimetric characteristics, especially regarding PTV dose homogeneity and normal tissue sparing. However, for both techniques, doses to OAR were well below the currently accepted normal tissue tolerances. Consequently, factors other than the dosimetric parameters studied here may have to be considered when making a choice between IMRT techniques.

  14. Dosimetric Comparison of Split Field and Fixed Jaw Techniques for Large IMRT Target Volumes in the Head and Neck

    SciTech Connect

    Srivastava, Shiv P.; Das, Indra J.; Kumar, Arvind; Johnstone, Peter A.S.

    2011-04-01

    Some treatment planning systems (TPSs), when used for large-field (>14 cm) intensity-modulated radiation therapy (IMRT), create split fields that produce excessive multiple-leaf collimator segments, match-line dose inhomogeneity, and higher treatment times than nonsplit fields. A new method using a fixed-jaw technique (FJT) forces the jaw to stay at a fixed position during optimization and is proposed to reduce problems associated with split fields. Dosimetric comparisons between split-field technique (SFT) and FJT used for IMRT treatment is presented. Five patients with head and neck malignancies and regional target volumes were studied and compared with both techniques. Treatment planning was performed on an Eclipse TPS using beam data generated for Varian 2100C linear accelerator. A standard beam arrangement consisting of nine coplanar fields, equally spaced, was used in both techniques. Institutional dose-volume constraints used in head and neck cancer were kept the same for both techniques. The dosimetric coverage for the target volumes between SFT and FJT for head and neck IMRT plan is identical within {+-}1% up to 90% dose. Similarly, the organs at risk (OARs) have dose-volume coverage nearly identical for all patients. When the total monitor unit (MU) and segments were analyzed, SFT produces statistically significant higher segments (17.3 {+-} 6.3%) and higher MU (13.7 {+-} 4.4%) than the FJT. There is no match line in FJT and hence dose uniformity in the target volume is superior to the SFT. Dosimetrically, SFT and FJT are similar for dose-volume coverage; however, the FJT method provides better logistics, lower MU, shorter treatment time, and better dose uniformity. The number of segments and MU also has been correlated with the whole body radiation dose with long-term complications. Thus, FJT should be the preferred option over SFT for large target volumes.

  15. TH-E-BRE-05: Analysis of Dosimetric Characteristics in Two Leaf Motion Calculator Algorithms for Sliding Window IMRT

    SciTech Connect

    Wu, L; Huang, B; Rowedder, B; Ma, B; Kuang, Y

    2014-06-15

    Purpose: The Smart leaf motion calculator (SLMC) in Eclipse treatment planning system is an advanced fluence delivery modeling algorithm as it takes into account fine MLC features including inter-leaf leakage, rounded leaf tips, non-uniform leaf thickness, and the spindle cavity etc. In this study, SLMC and traditional Varian LMC (VLMC) algorithms were investigated, for the first time, in dosimetric characteristics and delivery accuracy of sliding window (SW) IMRT. Methods: The SW IMRT plans of 51 cancer cases were included to evaluate dosimetric characteristics and dose delivery accuracy from leaf motion calculated by SLMC and VLMC, respectively. All plans were delivered using a Varian TrueBeam Linac. The DVH and MUs of the plans were analyzed. Three patient specific QA tools - independent dose calculation software IMSure, Delta4 phantom, and EPID portal dosimetry were also used to measure the delivered dose distribution. Results: Significant differences in the MUs were observed between the two LMCs (p≤0.001).Gamma analysis shows an excellent agreement between the planned dose distribution calculated by both LMC algorithms and delivered dose distribution measured by three QA tools in all plans at 3%/3 mm, leading to a mean pass rate exceeding 97%. The mean fraction of pixels with gamma < 1 of SLMC is slightly lower than that of VLMC in the IMSure and Delta4 results, but higher in portal dosimetry (the highest spatial resolution), especially in complex cases such as nasopharynx. Conclusion: The study suggests that the two LMCs generates the similar target coverage and sparing patterns of critical structures. However, SLMC is modestly more accurate than VLMC in modeling advanced MLC features, which may lead to a more accurate dose delivery in SW IMRT. Current clinical QA tools might not be specific enough to differentiate the dosimetric discrepancies at the millimeter level calculated by these two LMC algorithms. NIH/NIGMS grant U54 GM104944, Lincy Endowed

  16. CBCT-based volumetric and dosimetric variation evaluation of volumetric modulated arc radiotherapy in the treatment of nasopharyngeal cancer patients

    PubMed Central

    2013-01-01

    Objective To investigate the anatomic and dosimetric variations of volumetric modulated arc therapy (VMAT) in the treatment of nasopharyngeal cancer (NPC) patients based on weekly cone beam CT (CBCT). Materials and methods Ten NPC patients treated by VMAT with weekly CBCT for setup corrections were reviewed retrospectively. Deformed volumes of targets and organs at risk (OARs) in the CBCT were compared with those in the planning CT. Delivered doses were recalculated based on weekly CBCT and compared with the planned doses. Results No significant volumetric changes on targets, brainstem, and spinal cord were observed. The average volumes of right and left parotid measured from the fifth CBCT were about 4.4 and 4.5 cm3 less than those from the first CBCT, respectively. There were no significant dose differences between average planned and delivered doses for targets, brainstem and spinal cord. For right parotid, the delivered mean dose was 10.5 cGy higher (p = 0.004) than the planned value per fraction, and the V26 and V32 increased by 7.5% (p = 0.002) and 7.4% (p = 0.01), respectively. For the left parotid, the D50 (dose to the 50% volume) was 8.8 cGy higher (p = 0.03) than the planned values per fraction, and the V26 increased by 8.8% (p = 0.002). Conclusion Weekly CBCTs were applied directly to study the continuous volume changes and resulting dosimetric variations of targets and OARs for NPC patients undergoing VMAT. Significant volumetric and dosimetric variations were observed for parotids. Replanning after 30 Gy will benefit the protection on parotids. PMID:24289312

  17. Correlation of dosimetric parameters obtained with the analytical anisotropic algorithm and toxicity of chest chemoradiation in lung carcinoma

    SciTech Connect

    Cartier, Lysian; Auberdiac, Pierre; Khodri, Mustapha; Malkoun, Nadia; Chargari, Cyrus; Thorin, Julie; Melis, Adrien; Talabard, Jean-Noeel; Laroche, Guy de; Fournel, Pierre; Tiffet, Olivier; Schmitt, Thierry; and others

    2012-07-01

    The purpose of this study was to analyze and revisit toxicity related to chest chemoradiotherapy and to correlate these side effects with dosimetric parameters obtained using analytical anisotropic algorithm (AAA) in locally unresectable advanced lung cancer. We retrospectively analyzed data from 47 lung cancer patients between 2005 and 2008. All received conformal 3D radiotherapy using high-energy linear accelerator plus concomitant chemotherapy. All treatment planning data were transferred into Eclipse 8.05 (Varian Medical Systems, Palo Alto, CA) and dosimetric calculations were performed using AAA. Thirty-three patients (70.2%) developed acute pneumopathy after radiotherapy (grades 1 and 2). One patient (2.1%) presented with grade 3 pneumopathy. Thirty-one (66%) presented with grades 1-2 lung fibrosis, and 1 patient presented with grade 3 lung fibrosis. Thirty-four patients (72.3%) developed grade 1-2 acute oesophagic toxicity. Four patients (8.5%) presented with grades 3 and 4 dysphagia, necessitating prolonged parenteral nutrition. Median prescribed dose was 64 Gy (range 50-74) with conventional fractionation (2 Gy per fraction). Dose-volume constraints were respected with a median V20 of 23.5% (maximum 34%) and a median V30 of 17% (maximum 25%). The median dose delivered to healthy contralateral lung was 13.1 Gy (maximum 18.1 Gy). At univariate analysis, larger planning target volume and V20 were significantly associated with the probability of grade {>=}2 radiation-induced pneumopathy (p = 0.022 and p = 0.017, respectively). No relation between oesophagic toxicity and clinical/dosimetric parameters could be established. Using AAA, the present results confirm the predictive value of the V20 for lung toxicity as already demonstrated with the conventional pencil beam convolution approach.

  18. Comparison of the dose distribution obtained from dosimetric systems with intensity modulated radiotherapy planning system in the treatment of prostate cancer

    NASA Astrophysics Data System (ADS)

    Gökçe, M.; Uslu, D. Koçyiǧit; Ertunç, C.; Karalı, T.

    2016-03-01

    The aim of this study is to compare Intensity Modulated Radiation Therapy (IMRT) plan of prostate cancer patients with different dose verification systems in dosimetric aspects and to compare these systems with each other in terms of reliability, applicability and application time. Dosimetric control processes of IMRT plan of three prostate cancer patients were carried out using thermoluminescent dosimeter (TLD), ion chamber (IC) and 2D Array detector systems. The difference between the dose values obtained from the dosimetric systems and treatment planning system (TPS) were found to be about % 5. For the measured (TLD) and calculated (TPS) doses %3 percentage differences were obtained for the points close to center while percentage differences increased at the field edges. It was found that TLD and IC measurements will increase the precision and reliability of the results of 2D Array.

  19. Dosimetric properties of new cards with high-sensitivity MCP-N (LiF:Mg,Cu,P) detectors for Harshaw automatic reader.

    PubMed

    Budzanowski, M; Bilski, P; Olko, P; Ryba, E; Perle, S; Majewski, M

    2007-01-01

    A new configuration for a thermoluminescent dosimetric card has been developed through collaboration between the Institute of Nuclear Physics in Kraków and several commercial dosimetric companies. The card is based on high-sensitivity LiF:Mg,Cu,P circular pellets (MCP-N) welded inside synthetic foils. The basic configuration consists of two pellets of 3.6 mm diameter and thicknesses from 0.25 up to 0.38 mm. The cards can be processed in a standard 6600 or 8800 Harshaw automatic TLD reader. The dosemeters demonstrate very high sensitivity, low background and good stability. This article presents results of the performance tests of the new dosimetric cards in the automatic TLD readers and a comparison of their properties. PMID:17020912

  20. SESAME: a software tool for the numerical dosimetric reconstruction of radiological accidents involving external sources and its application to the accident in Chile in December 2005.

    PubMed

    Huet, C; Lemosquet, A; Clairand, I; Rioual, J B; Franck, D; de Carlan, L; Aubineau-Lanièce, I; Bottollier-Depois, J F

    2009-01-01

    Estimating the dose distribution in a victim's body is a relevant indicator in assessing biological damage from exposure in the event of a radiological accident caused by an external source. This dose distribution can be assessed by physical dosimetric reconstruction methods. Physical dosimetric reconstruction can be achieved using experimental or numerical techniques. This article presents the laboratory-developed SESAME--Simulation of External Source Accident with MEdical images--tool specific to dosimetric reconstruction of radiological accidents through numerical simulations which combine voxel geometry and the radiation-material interaction MCNP(X) Monte Carlo computer code. The experimental validation of the tool using a photon field and its application to a radiological accident in Chile in December 2005 are also described. PMID:19066489

  1. Dosimetric effects of positioning shifts using 6D-frameless stereotactic Brainlab system in hypofractionated intracranial radiotherapy.

    PubMed

    Jin, Hosang; Keeling, Vance P; Ali, Imad; Ahmad, Salahuddin

    2016-01-01

    Dosimetric consequences of positional shifts were studied using frameless Brainlab ExacTrac X-ray system for hypofractionated (3 or 5 fractions) intracranial stereo-tactic radiotherapy (SRT). SRT treatments of 17 patients with metastatic intracranial tumors using the stereotactic system were retrospectively investigated. The treatments were simulated in a treatment planning system by modifying planning parameters with a matrix conversion technique based on positional shifts for initial infrared (IR)-based setup (XC: X-ray correction) and post-correction (XV: X-ray verification). The simulation was implemented with (a) 3D translational shifts only and (b) 6D translational and rotational shifts for dosimetric effects of angular correction. Mean translations and rotations (± 1 SD) of 77 fractions based on the initial IR setup (XC) were 0.51 ± 0.86 mm (lateral), 0.30 ± 1.55 mm (longitudinal), and -1.63 ± 1.00 mm (vertical); -0.53° ± 0.56° (pitch), 0.42° ± 0.60° (roll), and 0.44°± 0.90° (yaw), respectively. These were -0.07 ± 0.24 mm, -0.07 ± 0.25 mm, 0.06± 0.21 mm, 0.04° ± 0.23°, 0.00° ± 0.30°, and -0.02° ± 0.22°, respectively, for the postcorrection (XV). Substantial degradation of the treatment plans was observed in D95 of PTV (2.6% ± 3.3%; simulated treatment versus treatment planning), Dmin of PTV (13.4% ± 11.6%), and Dmin of CTV (2.8% ± 3.8%, with the maximum error of 10.0%) from XC, while dosimetrically negligible changes (< 0.1%) were detected for both CTV and PTV from XV simulation. 3D angular correction significantly improved CTV dose coverage when the total angular shifts (|pitch| + |roll| + |yaw|) were greater than 2°. With the 6D stereoscopic X-ray verification imaging and frameless immobilization, submillimeter and subdegree accuracy is achieved with negligible dosimetric deviations. 3D angular correction is required when the angular deviation is substantial. A CTV-to-PTV safety margin of 2 mm is large enough to prevent

  2. An innovative dosimetric model for formulating a semi-analytical solution for the activity-volume relationship in prostate implants

    SciTech Connect

    Lee, Plato C.; Parks, Eric K.; Moran, Brian J

    2003-12-31

    An innovative (and yet simple) dosimetric model is proposed that provides a semi-analytical solution to the total activity-volume relationship in ultrasound-guided transperineal prostate implant. This dosimetric model is based on 4 simple assumptions. First, the prostate target volume is approximated as a sphere. Second, the urethra is presumed to transverse through the center of the prostate target volume. Third, peripheral loading is applied as the seed-loading technique. Fourth, as the major innovation of the proposed model, the radial dose function of the Iodine-125 {sup 125}I seed is forced to fit a simple power function of the distance r. Pursuant to the third assumption, the peripherally-loaded seeds also define a spherical volume defined as the loading volume w. Also pursuant to the fourth assumption, the radial dose function is expressed as 1.139*r{sup -0.474} for r = 1.5 to 2.5 cm. Thereafter, a simple analytical power-law equation, A = 1.630* w{sup 0.825}, for the relationship between the total activity A in mCi and the loading volume w in cc is derived for {sup 125}I monotherapy. Isodose plans for loading volumes corresponding to r = 1.5, 1.8, 2.2, and 2.5 cm were performed. The maximal isodose coverage volume {sub max}V100 was calculated for each case and was found to be on the average 65% larger than the loading volume w. Matching prostate target volume V to the loading volume w therefore yields a generous implant (with a margin of approximately 3.3 mm). Conversely, matching the prostate target volume V to the {sub max}V100 yields a tight implant (with 0.0 mm or no margin). Matching the prostate target volume V to a midpoint between the loading volume w and {sub max}V100 yields a moderate implant (with approximately 1- to 2-mm margin). Three individual equations are derived for each type of implants: A = 1.630* V{sup 0.825}, A = 1.288* V{sup 0.825}, or A = 1.078 V{sup 0.825} for generous, tight, or moderate implants, respectively. Patient data at the

  3. Dosimetric and biological results from the Bacillus subtilis Biostack experiment with the Apollo-Soyuz Test Project.

    PubMed

    Facius, R; Bucker, H; Horneck, G; Reitz, G; Schafer, M

    1979-01-01

    The evaluation of the Bacillus subtilis experiment has been completed. The biological and the physical results for this part of the Apollo-Soyuz Test Project (ASTP) Biostack experiment are given. This comprises dosimetric data for the cosmic radiation at that orbit as well as biological findings from two types of plastic detectors. Further, the frequency distributions of the physical quantities atomic number, energy and energy loss of the heavy ions within the sample of spores hit are presented. The biological hazard presented by cosmic HZE-particles has been much underestimated. PMID:12001965

  4. Dosimetric comparison of two arc-based stereotactic body radiotherapy techniques for early-stage lung cancer

    SciTech Connect

    Liu, Huan Ye, Jingjing; Kim, John J.; Deng, Jun; Kaur, Monica S.; Chen, Zhe

    2015-04-01

    To compare the dosimetric and delivery characteristics of two arc-based stereotactic body radiotherapy (SBRT) techniques for early-stage lung cancer treatment. SBRT treatment plans for lung tumors of different sizes and locations were designed using a single-isocenter multisegment dynamic conformal arc technique (SiMs-arc) and a volumetric modulated arc therapy technique (RapidArc) for 5 representative patients treated previously with lung SBRT. The SiMs-arc plans were generated with the isocenter located in the geometric center of patient's axial plane (which allows for collision-free gantry rotation around the patient) and 6 contiguous 60° arc segments spanning from 1° to 359°. 2 RapidArc plans, one using the same arc geometry as the SiMs-arc and the other using typical partial arcs (210°) with the isocenter inside planning target volume (PTV), were generated for each corresponding SiMs-arc plan. All plans were generated using the Varian Eclipse treatment planning system (V10.0) and were normalized with PTV V{sub 100} to 95%. PTV coverage, dose to organs at risk, and total monitor units (MUs) were then compared and analyzed. For PTV coverage, the RapidArc plans generally produced higher PTV D{sub 99} (by 1.0% to 3.3%) and higher minimum dose (by 2.7% to 12.7%), better PTV conformality index (by 1% to 8%), and less volume of 50% dose outside 2 cm from PTV (by 0 to 20.8 cm{sup 3}) than the corresponding SiMs-arc plans. For normal tissues, no significant dose differences were observed for the lungs, trachea, chest wall, and heart; RapidArc using partial arcs produced lowest maximum dose to spinal cord. For dose delivery, the RapidArc plans typically required 50% to 90% more MUs than SiMs-arc plans to deliver the same prescribed dose. The additional intensity modulation afforded by variable gantry speed and dose rate and by overlapping arcs enabled RapidArc plans to produce dosimetrically improved plans for lung SBRT, but required more MUs (by a factor > 1.5) to

  5. Analysis of Clinical and Dosimetric Factors Influencing Radiation-Induced Lung Injury in Patients with Lung Cancer

    PubMed Central

    Han, Shuiyun; Gu, Feiying; Lin, Gang; Sun, Xiaojiang; Wang, Yuezhen; Wang, Zhun; Lin, Qingren; Weng, Denghu; Xu, Yaping; Mao, Weimin

    2015-01-01

    Purpose: Dose escalation of thoracic radiation can improve the local tumor control and surivival, and is in the meantime limited by the occurrence of radiation-induced lung injury (RILI). This study investigated the clinical and dosimetric factors influencing RILI in lung-cancer patients receiving chemoradiotherapy for better radiation planning. Methods and Materials: A retrospective analysis was carried out on 161 patients with non-small-cell or small-cell lung cancer (NSCLC and SCLC, respectively), who underwent chemoradiotherapy between April 2010 and May 2011 with a median follow-up time of 545 days (range: 39-1453). Chemotherapy regimens were based on the histological type (squamous cell carcinoma, adenocarcinoma, or SCLC), and radiotherapy was delivered in 1.8-3.0 Gy (median, 2.0 Gy) fractions, once daily, to a total of 39-66 Gy (median, 60 Gy). Univariate analysis was performed to analyze clinical and dosimetric factors associated with RILI. Multivariate analysis using logistic regression identified independent risk factors correlated to RILI. Results: The incidence of symptomatic RILI (≥grade 2) was 31.7%. Univariate analysis showed that V5, V20, and mean lung dose (MLD) were significantly associated with RILI incidence (P=0.029, 0.048, and 0.041, respectively). The association was not statistically significant for histological type (NSCLC vs. SCLC, P = 0.092) or radiation technology (IMRT vs. 3D-CRT, P = 0.095). Multivariate analysis identified MLD as an independent risk factor for symptomatic RILI (OR=1.249, 95%CI=1.055-1.48, P= 0.01). The incidence of bilateral RILI in cases where the tumor was located unilaterally was 22.7% (32/141) and all dosimetric-parameter values were not significantly different (P>0.05) for bilateral versus ipsilateral injury, except grade-1 (low) RILI (P < 0.05). The RILI grade was higher in cases of ipsilateral lung injury than in bilateral cases (Mann-Whitney U test, z=8.216, P< 0.001). Conclusion: The dosimetric parameter

  6. Dosimetric Verification and Validation of Conformal and IMRT Treatments Fields with an Ionization Chamber 2D-Array

    NASA Astrophysics Data System (ADS)

    Evangelina, Figueroa M.; Gabriel, Reséndiz G.; Miguel, Pérez P.

    2008-08-01

    A three-dimensional treatment planning system requires comparisons of calculated and measured dose distributions. It is necessary to confirm by means of patient specific QA that the dose distributions are correctly calculated, and that the patient data is correctly transferred to and delivered by the treatment machine. We used an analysis software for bi-dimensional dosimetric verification of conformal treatment and IMRT fields using as objective criterion the gamma index. An ionization chamber bi-dimensional array was used for absolute dose measurement in the complete field area.

  7. Dosimetric experience with 2 commercially available multilumen balloon-based brachytherapy to deliver accelerated partial-breast irradiation

    SciTech Connect

    Fu, Weihua Kim, Jong Oh; Chen, Alex S.J.; Mehta, Kiran; Pucci, Pietro; Huq, M. Saiful

    2015-10-01

    The purpose of this work was to report dosimetric experience with 2 kinds of multilumen balloon (MLB), 5-lumen Contura MLB (C-MLB) and 4-lumen MammoSite MLB (MS-MLB), to deliver accelerated partial-breast irradiation, and compare the ability to achieve target coverage and control skin and rib doses between 2 groups of patients treated with C-MLB and MS-MLB brachytherapy. C-MLB has 5 lumens, the 4 equal-spaced peripheral lumens are 5 mm away from the central lumen. MS-MLB has 4 lumens, the 3 equal-spaced peripheral lumens are 3 mm away from the central lumen. In total, 43 patients were treated, 23 with C-MLB, and 20 with MS-MLB. For C-MLB group, 8 patients were treated with a skin spacing < 7 mm and 12 patients with rib spacing < 7 mm. For MS-MLB group, 2 patients were treated with a skin spacing < 7 mm and 5 patients with rib spacing < 7 mm. The dosimetric goals were (1) ≥ 95% of the prescription dose (PD) covering ≥ 95% of the target volume (V{sub 95%} ≥ 95%), (2) maximum skin dose ≤ 125% of the PD, (3) maximum rib dose ≤ 145% of the PD (if possible), and (4) the V{sub 150%} ≤ 50 cm{sup 3} and V{sub 200%} ≤ 10 cm{sup 3}. All dosimetric criteria were met concurrently in 82.6% of C-MLB patients, in 80.0% of MS-MLB patients, and in 81.4% of all 43 patients. For each dosimetric parameter, t-test of these 2 groups showed p > 0.05. Although the geometric design of C-MLB is different from that of MS-MLB, both applicators have the ability to shape the dose distribution and to provide good target coverage, while limiting the dose to skin and rib. No significant difference was observed between the 2 patient groups in terms of target dose coverage and dose to organs at risk.

  8. Evaluation of the dosimetric properties of a synthetic single crystal diamond detector in high energy clinical proton beams

    SciTech Connect

    Mandapaka, A. K.; Ghebremedhin, A.; Patyal, B.; Marinelli, Marco; Prestopino, G.; Verona, C.; Verona-Rinati, G.

    2013-12-15

    Purpose: To investigate the dosimetric properties of a synthetic single crystal diamond Schottky diode for accurate relative dose measurements in large and small field high-energy clinical proton beams.Methods: The dosimetric properties of a synthetic single crystal diamond detector were assessed by comparison with a reference Markus parallel plate ionization chamber, an Exradin A16 microionization chamber, and Exradin T1a ion chamber. The diamond detector was operated at zero bias voltage at all times. Comparative dose distribution measurements were performed by means of Fractional depth dose curves and lateral beam profiles in clinical proton beams of energies 155 and 250 MeV for a 14 cm square cerrobend aperture and 126 MeV for 3, 2, and 1 cm diameter circular brass collimators. ICRU Report No. 78 recommended beam parameters were used to compare fractional depth dose curves and beam profiles obtained using the diamond detector and the reference ionization chamber. Warm-up/stability of the detector response and linearity with dose were evaluated in a 250 MeV proton beam and dose rate dependence was evaluated in a 126 MeV proton beam. Stem effect and the azimuthal angle dependence of the diode response were also evaluated.Results: A maximum deviation in diamond detector signal from the average reading of less than 0.5% was found during the warm-up irradiation procedure. The detector response showed a good linear behavior as a function of dose with observed deviations below 0.5% over a dose range from 50 to 500 cGy. The detector response was dose rate independent, with deviations below 0.5% in the investigated dose rates ranging from 85 to 300 cGy/min. Stem effect and azimuthal angle dependence of the diode signal were within 0.5%. Fractional depth dose curves and lateral beam profiles obtained with the diamond detector were in good agreement with those measured using reference dosimeters.Conclusions: The observed dosimetric properties of the synthetic single

  9. Heat Capacity Mapping Mission

    NASA Technical Reports Server (NTRS)

    Nilsson, C. S.; Andrews, J. C.; Scully-Power, P.; Ball, S.; Speechley, G.; Latham, A. R. (Principal Investigator)

    1980-01-01

    The Tasman Front was delineated by airborne expendable bathythermograph survey; and an Heat Capacity Mapping Mission (HCMM) IR image on the same day shows the same principal features as determined from ground-truth. It is clear that digital enhancement of HCMM images is necessary to map ocean surface temperatures and when done, the Tasman Front and other oceanographic features can be mapped by this method, even through considerable scattered cloud cover.

  10. Map-likelihood phasing

    PubMed Central

    Terwilliger, Thomas C.

    2001-01-01

    The recently developed technique of maximum-likelihood density modification [Terwilliger (2000 ▶), Acta Cryst. D56, 965–972] allows a calculation of phase probabilities based on the likelihood of the electron-density map to be carried out separately from the calculation of any prior phase probabilities. Here, it is shown that phase-probability distributions calculated from the map-likelihood function alone can be highly accurate and that they show minimal bias towards the phases used to initiate the calculation. Map-likelihood phase probabilities depend upon expected characteristics of the electron-density map, such as a defined solvent region and expected electron-density distributions within the solvent region and the region occupied by a macromolecule. In the simplest case, map-likelihood phase-probability distributions are largely based on the flatness of the solvent region. Though map-likelihood phases can be calculated without prior phase information, they are greatly enhanced by high-quality starting phases. This leads to the technique of prime-and-switch phasing for removing model bias. In prime-and-switch phasing, biased phases such as those from a model are used to prime or initiate map-likelihood phasing, then final phases are obtained from map-likelihood phasing alone. Map-likelihood phasing can be applied in cases with solvent content as low as 30%. Potential applications of map-likelihood phasing include unbiased phase calculation from molecular-replacement models, iterative model building, unbiased electron-density maps for cases where 2Fo − Fc or σA-weighted maps would currently be used, structure validation and ab initio phase determination from solvent masks, non-crystallographic symmetry or other knowledge about expected electron density. PMID:11717488

  11. Regularity of mappings inverse to Sobolev mappings

    SciTech Connect

    Vodop'yanov, Sergei K

    2012-10-31

    For homeomorphisms {phi}:{Omega}{yields}{Omega}' on Euclidean domains in R{sup n}, n{>=}2, necessary and sufficient conditions ensuring that the inverse mapping belongs to a Sobolev class are investigated. The result obtained is used to describe a new two-index scale of homeomorphisms in some Sobolev class such that their inverses also form a two-index scale of mappings, in another Sobolev class. This scale involves quasiconformal mappings and also homeomorphisms in the Sobolev class W{sup 1}{sub n-1} such that rankD{phi}(x){<=}n-2 almost everywhere on the zero set of the Jacobian det D{phi}(x). Bibliography: 65 titles.

  12. Making maps with computers

    USGS Publications Warehouse

    Guptill, S.C.; Starr, L.E.

    1988-01-01

    Soon after their introduction in the 1950s, digital computers were used for various phases of the mapping process, especially for trigonometric calculations of survey data and for orientation of aerial photographs on map manuscripts. In addition, computer-controlled plotters were used to draw simple outline maps. The process of collecting data for the plotters was slow and not as precise as those produced by the best manual cartography. Only during the 1980s has it become technologically feasible and cost-effective to assemble and use the data required to automate the mapping process. -from Authors

  13. DENALI IMAGE MAP.

    USGS Publications Warehouse

    Binnie, Douglas R.; Colvocoresses, Alden P.

    1987-01-01

    The Denali National Park and Preserve 1:250,000-scale image map has been prepared and published as part of the US Geological Survey's (USGS) continuing research to improve image mapping techniques. Nine multispectral scanner (MSS) images were geometrically corrected, digitally mosaicked, and enhanced at the National Mapping Division's (NMD) EROS Data Center (EDC). This process involves ground control and digital resampling to the Universal Tranverse Mercator (UTM) projection. This paper specifically discusses the preparation of the digital mosaic and the production peculiarities associated with the Denali National Park and Preserve image map.

  14. Chaotic Polynomial Maps

    NASA Astrophysics Data System (ADS)

    Zhang, Xu

    This paper introduces a class of polynomial maps in Euclidean spaces, investigates the conditions under which there exist Smale horseshoes and uniformly hyperbolic invariant sets, studies the chaotic dynamical behavior and strange attractors, and shows that some maps are chaotic in the sense of Li-Yorke or Devaney. This type of maps includes both the Logistic map and the Hénon map. For some diffeomorphisms with the expansion dimension equal to one or two in three-dimensional spaces, the conditions under which there exist Smale horseshoes and uniformly hyperbolic invariant sets on which the systems are topologically conjugate to the two-sided fullshift on finite alphabet are obtained; for some expanding maps, the chaotic region is analyzed by using the coupled-expansion theory and the Brouwer degree theory. For three types of higher-dimensional polynomial maps with degree two, the conditions under which there are Smale horseshoes and uniformly hyperbolic invariant sets are given, and the topological conjugacy between the maps on the invariant sets and the two-sided fullshift on finite alphabet is obtained. Some interesting maps with chaotic attractors and positive Lyapunov exponents in three-dimensional spaces are found by using computer simulations. In the end, two examples are provided to illustrate the theoretical results.

  15. BOREAS Hardcopy Maps

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Nelson, Elizabeth; Newcomer, Jeffrey A.

    2000-01-01

    Boreal Ecosystem-Atmospheric Study (BOREAS) hardcopy maps are a collection of approximately 1,000 hardcopy maps representing the physical, climatological, and historical attributes of areas covering primarily the Manitoba and Saskatchewan provinces of Canada. These maps were collected by BOREAS Information System (BORIS) and Canada for Remote Sensing (CCRS) staff to provide basic information about site positions, manmade features, topography, geology, hydrology, land cover types, fire history, climate, and soils of the BOREAS study region. These maps are not available for distribution through the BOREAS project but may be used as an on-site resource. Information is provided within this document for individuals who want to order copies of these maps from the original map source. Note that the maps are not contained on the BOREAS CD-ROM set. An inventory listing file is supplied on the CD-ROM to inform users of the maps that are available. This inventory listing is available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). For hardcopies of the individual maps, contact the sources provided.

  16. Three-dimensional spatial and dosimetric characterization of radiotherapy beams using laser read-out of TLDs

    SciTech Connect

    Grupen-Shemansky, M.E.

    1989-01-01

    A fully automated thermoluminescent detector (TLD) read-out apparatus has been designed and constructed for the express purpose of extracting spatially resolved dosimetric information using localized IR laser phosphor stimulation. A composite TLD plate has been designed that withstands the thermal stresses developed during laser heating. This detector and unique read-out scheme may be used to spatially and dosimetrically characterize ionizing radiation fields. The thermal response of TL materials cannot be fully characterized experimentally due to the inability of modern measuring techniques to accurately record the rapidly changing temperatures. Two-dimensional, time transient models have been derived to determine radial and axial temperature profiles in a TL layer when a 4 W CO{sub 2} focused or unfocused Gaussian laser beam is used to heat a single or multiple spots. Numerically derived temperature profiles were then used in a first-order kinetic model for the thermoluminescent emission. The experimental laser heated TLD read-out apparatus was used to image a {sup 60}Co radiotherapy beam. A 2.2 cm by 3.3 cm LiF detector was used to image the penumbra of a 5 cm by 5 cm collimated field of a Theratron-80. Qualitative and quantitative results agreed well with accepted beam depth dose profiles measured with ionization chambers in water bath phantoms.

  17. Total occupational exposure during characterisation, conditioning and securing of radioactive sealed sources: a new dosimetric concept using active electronic dosimeters.

    PubMed

    Prlić, Ivica; Mihić, Marija Surić; Marović, Gordana; Mestrović, Tomislav

    2009-03-01

    Radiation dosimetry in protection against ionising radiation involves research of all possible pathways through which natural or man-made radioactive materials can contaminate a habitat and actually harm its biota. It also takes into account natural and artificial (man-made) electromagnetic ionizing radiation (gamma and x radiation). This article presents a dosimetric study assessing exposure to man-made ionising radiation of local environment and total occupational exposure of two professional workers involved in characterisation, conditioning, and securing of unused radioactive sealed sources. The purpose of the study was to validate a new active electronic dosimeter (AED) of type ALARA OD and to develop a new monitoring method by tracing the external occupational exposure over real time. This method is used to continuously measure and record external radiation doses and, which is a novelty, establish dose rates receiving pattern as a function of real time. Occupational whole body dosimetric results obtained with AED were compared with results obtained with passive dosimetry (film badge and thermoluminiscence). Air, dust, and silicon sand samples were analysed by gamma-spectrometry to estimate internal exposure of the two workers to 222Rn due to inhalation or ingestion of dust and sand in indoor air. In order to establish total occupational exposure, control radon measurement was performed in the immediate environment and the external Hazard index (Hex) was calculated. PMID:19329376

  18. Dosimetric differences between intraoperative and postoperative plans using Cs-131 in transrectal ultrasound–guided brachytherapy for prostatic carcinoma

    SciTech Connect

    Jones, Andrew; Treas, Jared; Yavoich, Brian; Dean, Douglas; Danella, John; Yumen, Omar

    2014-01-01

    The aim of the study was to investigate the differences between intraoperative and postoperative dosimetry for transrectal ultrasound–guided transperineal prostate implants using cesium-131 ({sup 131}Cs). Between 2006 and 2010, 166 patients implanted with {sup 131}Cs had both intraoperative and postoperative dosimetry studies. All cases were monotherapy and doses of 115 were prescribed to the prostate. The dosimetric properties (D{sub 90}, V{sub 150}, and V{sub 100} for the prostate) of the studies were compared. Two conformity indices were also calculated and compared. Finally, the prostate was automatically sectioned into 6 sectors (anterior and posterior sectors at the base, midgland, and apex) and the intraoperative and postoperative dosimetry was compared in each individual sector. Postoperative dosimetry showed statistically significant changes (p < 0.01) in every dosimetric value except V{sub 150}. In each significant case, the postoperative plans showed lower dose coverage. The conformity indexes also showed a bimodal frequency distribution with the index indicating poorer dose conformity in the postoperative plans. Sector analysis revealed less dose coverage postoperatively in the base and apex sectors with an increase in dose to the posterior midgland sector. Postoperative dosimetry overall and in specific sectors of the prostate differs significantly from intraoperative planning. Care must be taken during the intraoperative planning stage to ensure complete dose coverage of the prostate with the understanding that the final postoperative dosimetry will show less dose coverage.

  19. The dosimetric effects of tissue heterogeneities in intensity-modulated radiation therapy (IMRT) of the head and neck.

    PubMed

    Al-Hallaq, H A; Reft, C S; Roeske, J C

    2006-03-01

    The dosimetric effects of bone and air heterogeneities in head and neck IMRT treatments were quantified. An anthropomorphic RANDO phantom was CT-scanned with 16 thermoluminescent dosimeter (TLD) chips placed in and around the target volume. A standard IMRT plan generated with CORVUS was used to irradiate the phantom five times. On average, measured dose was 5.1% higher than calculated dose. Measurements were higher by 7.1% near the heterogeneities and by 2.6% in tissue. The dose difference between measurement and calculation was outside the 95% measurement confidence interval for six TLDs. Using CORVUS' heterogeneity correction algorithm, the average difference between measured and calculated doses decreased by 1.8% near the heterogeneities and by 0.7% in tissue. Furthermore, dose differences lying outside the 95% confidence interval were eliminated for five of the six TLDs. TLD doses recalculated by Pinnacle3's convolution/superposition algorithm were consistently higher than CORVUS doses, a trend that matched our measured results. These results indicate that the dosimetric effects of air cavities are larger than those of bone heterogeneities, thereby leading to a higher delivered dose compared to CORVUS calculations. More sophisticated algorithms such as convolution/superposition or Monte Carlo should be used for accurate tailoring of IMRT dose in head and neck tumours. PMID:16481684

  20. The dosimetric effects of tissue heterogeneities in intensity-modulated radiation therapy (IMRT) of the head and neck

    NASA Astrophysics Data System (ADS)

    Al-Hallaq, H. A.; Reft, C. S.; Roeske, J. C.

    2006-03-01

    The dosimetric effects of bone and air heterogeneities in head and neck IMRT treatments were quantified. An anthropomorphic RANDO phantom was CT-scanned with 16 thermoluminescent dosimeter (TLD) chips placed in and around the target volume. A standard IMRT plan generated with CORVUS was used to irradiate the phantom five times. On average, measured dose was 5.1% higher than calculated dose. Measurements were higher by 7.1% near the heterogeneities and by 2.6% in tissue. The dose difference between measurement and calculation was outside the 95% measurement confidence interval for six TLDs. Using CORVUS' heterogeneity correction algorithm, the average difference between measured and calculated doses decreased by 1.8% near the heterogeneities and by 0.7% in tissue. Furthermore, dose differences lying outside the 95% confidence interval were eliminated for five of the six TLDs. TLD doses recalculated by Pinnacle3's convolution/superposition algorithm were consistently higher than CORVUS doses, a trend that matched our measured results. These results indicate that the dosimetric effects of air cavities are larger than those of bone heterogeneities, thereby leading to a higher delivered dose compared to CORVUS calculations. More sophisticated algorithms such as convolution/superposition or Monte Carlo should be used for accurate tailoring of IMRT dose in head and neck tumours.

  1. Dosimetric impact of applicator displacement during high dose rate (HDR) Cobalt-60 brachytherapy for cervical cancer: A planning study

    NASA Astrophysics Data System (ADS)

    Yong, J. S.; Ung, N. M.; Jamalludin, Z.; Malik, R. A.; Wong, J. H. D.; Liew, Y. M.; Ng, K. H.

    2016-02-01

    We investigated the dosimetric impact of applicator displacement on dose specification during high dose rate (HDR) Cobalt-60 (Co-60) brachytherapy for cervical cancer through a planning study. Eighteen randomly selected HDR full insertion plans were restrospectively studied. The tandem and ovoids were virtually shifted translationally and rotationally in the x-, y- and z-axis directions on the treatment planning system. Doses to reference points and volumes of interest in the plans with shifted applicators were compared with the original plans. The impact of dose displacement on 2D (point-based) and 3D (volume-based) treatment planning techniques was also assessed. A ±2 mm translational y-axis applicator shift and ±4° rotational x-axis applicator shift resulted in dosimetric changes of more than 5% to organs at risk (OAR) reference points. Changes to the maximum doses to 2 cc of the organ (D2cc) in 3D planning were statistically significant and higher than the reference points in 2D planning for both the rectum and bladder (p<0.05). Rectal D2cc was observed to be the most sensitive to applicator displacement among all dose metrics. Applicator displacement that is greater than ±2 mm translational y-axis and ±4° rotational x-axis resulted in significant dose changes to the OAR. Thus, steps must be taken to minimize the possibility of applicator displacement during brachytherapy.

  2. Dosimetric impact of interplay effect in lung IMRT and VMAT treatment using in-house dynamic thorax phantom

    NASA Astrophysics Data System (ADS)

    Mukhlisin; Pawiro, S. A.

    2016-03-01

    Tumor motion due to patient's respiratory is a significant problem in radiotherapy treatment of lung cancer. The purpose of this project is to study the interplay effect through dosimetry verification between the calculated and delivered dose, as well as the dosimetric impact of leaf interplay with breathing-induced tumor motion in IMRT and VMAT treatment. In this study, a dynamic thorax phantom was designed and constructed for dosimetry measurement. The phantom had a linear sinusoidal tumor motion toward superior-inferior direction with variation of amplitudes and periods. TLD-100 LiF:Mg,Ti and Gafchromic EBT2 film were used to measure dose in the midpoint target and the spinal cord. The IMRT and VMAT treatment had prescription dose of 200 cGy per fraction. The dosimetric impact due to interplay effect during IMRT and VMAT treatment were resulted in the range of 0.5% to -6.6% and 0.9% to -5.3% of target dose reduction, respectively. Meanwhile, mean dose deviation of spinal cord in IMRT and VMAT treatment were around 1.0% to -6.9% and 0.9% to -6.3%, respectively. The results showed that if respiratory management technique were not implemented, the presence of lung tumor motion during dose delivery in IMRT and VMAT treatment causes dose discrepancies inside tumor volume.

  3. Dosimetric comparison of four new design {sup 103}Pd brachytherapy sources: Optimal design using silver and copper rod cores

    SciTech Connect

    Hosseini, S. Hamed; Sadeghi, Mahdi; Ataeinia, Vahideh

    2009-07-15

    Four new brachytherapy sources, IRA1-{sup 103}Pd, IRA2-{sup 103}Pd, IRA3-{sup 103}Pd, and IRA4-{sup 103}Pd, have been developed at Agricultural, Medical, and Industrial Research School and are designed for permanent implant application. With the goal of determining an optimal design for a {sup 103}Pd source, this article compares the dosimetric properties of these sources with reference to the authors' earlier IRA-{sup 103}Pd source. The four new sources differ in end cap configuration and thickness and in the core material, silver or copper, that carries the adsorbed {sup 103}Pd. Dosimetric data derived from the authors' Monte Carlo simulation results are reported in accordance with the updated AAPM Task Group No. 43 report (TG-43U1). For each source, the authors obtained detailed results for the dose rate constant {Lambda}, the radial dose function g(r), the anisotropy function F(r,{theta}), and the anisotropy factor {phi}{sub an}(r). In this study, the optimal source IRA3-{sup 103}Pd provides the most isotropic dose distribution in water with the dose rate constant of 0.678({+-}0.1%) cGy h{sup -1} U{sup -1}. The IRA3-{sup 103}Pd design has a silver rod core combined with thin-wall, concave end caps. Finally, the authors compared the results for their optimal source with published results for those of other source manufacturers.

  4. Lyman Alpha Mapping Project (LAMP) Brightness Maps

    NASA Astrophysics Data System (ADS)

    Retherford, Kurt D.; Gladstone, G.; Stern, S.; Egan, A. F.; Miles, P. F.; Parker, J. W.; Greathouse, T. K.; Davis, M. W.; Slater, D. C.; Kaufmann, D. E.; Versteeg, M. H.; Feldman, P. D.; Hurley, D. M.; Pryor, W. R.; Hendrix, A. R.

    2010-10-01

    The Lyman Alpha Mapping Project (LAMP) is an ultraviolet (UV) spectrograph on the Lunar Reconnaissance Orbiter (LRO) that is designed to map the lunar albedo at far-UV wavelengths. LAMP primarily measures interplanetary Hydrogen Lyman-alpha sky-glow and far-UV starlight reflected from the night-side lunar surface, including permanently shadowed regions (PSRs) near the poles. Dayside observations are also obtained. Brightness maps sorted by wavelength (including the Lyman-alpha wavelength of 121.6 nm) are reported for the polar regions, with a few regions of interest reported in more detail. LAMP's spectral range of 58 nm to 196 nm includes a water ice spectral feature near 160 nm, which provides a diagnostic tool for detecting water on the lunar surface that is complementary to recent discoveries using infrared and radio frequency techniques. Progress towards producing far-UV albedo maps and searching for water ice signatures will be reported. We'll discuss how LAMP data may address questions regarding how water is formed on the moon, transported through the lunar atmosphere, and deposited in the PSRs.

  5. Maps and Map Learning in Social Studies

    ERIC Educational Resources Information Center

    Bednarz, Sarah Witham; Acheson, Gillian; Bednarz, Robert S.

    2006-01-01

    The importance of maps and other graphic representations has become more important to geography and geographers. This is due to the development and widespread diffusion of geographic (spatial) technologies. As computers and silicon chips have become more capable and less expensive, geographic information systems (GIS), global positioning satellite…

  6. Chizu Task Mapping Tool

    2014-07-01

    Chizu is a tool for Mapping MPI processes or tasks to physical processors or nodes for optimizing communication performance. It takes the communication graph of a High Performance Computing (HPC) application and the interconnection topology of a supercomputer as input. It outputs a new MPI rand to processor mapping, which can be used when launching the HPC application.

  7. The Mapping of Admissionsland.

    ERIC Educational Resources Information Center

    Tyson, Daniel C.

    1982-01-01

    Describes a map designed to help students chart a college application strategy. The map locates each student on a grid by academic coordinates based on G.P.A. and test score index. Colleges are located on the same grid by identifying students admitted and circling dots representing academic locations. (RC)

  8. Temporal mapping and analysis

    NASA Technical Reports Server (NTRS)

    O'Hara, Charles G. (Inventor); Shrestha, Bijay (Inventor); Vijayaraj, Veeraraghavan (Inventor); Mali, Preeti (Inventor)

    2011-01-01

    A compositing process for selecting spatial data collected over a period of time, creating temporal data cubes from the spatial data, and processing and/or analyzing the data using temporal mapping algebra functions. In some embodiments, the temporal data cube is creating a masked cube using the data cubes, and computing a composite from the masked cube by using temporal mapping algebra.

  9. Map of Nasca Geoglyphs

    NASA Astrophysics Data System (ADS)

    Hanzalová, K.; Pavelka, K.

    2013-07-01

    The Czech Technical University in Prague in the cooperation with the University of Applied Sciences in Dresden (Germany) work on the Nasca Project. The cooperation started in 2004 and much work has been done since then. All work is connected with Nasca lines in southern Peru. The Nasca project started in 1995 and its main target is documentation and conservation of the Nasca lines. Most of the project results are presented as WebGIS application via Internet. In the face of the impending destruction of the soil drawings, it is possible to preserve this world cultural heritage for the posterity at least in a digital form. Creating of Nasca lines map is very useful. The map is in a digital form and it is also available as a paper map. The map contains planimetric component of the map, map lettering and altimetry. Thematic folder in this map is a vector layer of the geoglyphs in Nasca/Peru. Basis for planimetry are georeferenced satellite images, altimetry is created from digital elevation model. This map was created in ArcGis software.

  10. E-Concept Mapping

    ERIC Educational Resources Information Center

    Shmaefsky, Brian R.

    2007-01-01

    Not all demonstrations involve using exciting visual displays of one or a series of scientific principles. Demonstrations can be as simple as showing the interrelationship between scientific concepts or principles using concept maps. Concepts maps are tools that help people conceptualize and remember a conglomeration of facts making up complex…

  11. The Map Corner.

    ERIC Educational Resources Information Center

    Cheyney, Arnold B.; Capone, Donald L.

    This teaching resource is aimed at helping students develop the skills necessary to locate places on the earth. Designed as a collection of map skill exercises rather than a sequential program of study, this program expects that students have access to and some knowledge of how to use globes, maps, atlases, and encyclopedias. The volume contains 6…

  12. Handmade Multitextured Maps.

    ERIC Educational Resources Information Center

    Trevelyan, Simon

    1984-01-01

    Tactile maps for visually impaired persons can be made by drawing lines with an aqueous adhesive solution, dusting with thermoengraving powder, and exposing the card to a source of intense heat (such as a heat gun or microwave oven). A raised line map results. (CL)

  13. Acoustic mapping velocimetry

    NASA Astrophysics Data System (ADS)

    Muste, M.; Baranya, S.; Tsubaki, R.; Kim, D.; Ho, H.; Tsai, H.; Law, D.

    2016-05-01

    Knowledge of sediment dynamics in rivers is of great importance for various practical purposes. Despite its high relevance in riverine environment processes, the monitoring of sediment rates remains a major and challenging task for both suspended and bed load estimation. While the measurement of suspended load is currently an active area of testing with nonintrusive technologies (optical and acoustic), bed load measurement does not mark a similar progress. This paper describes an innovative combination of measurement techniques and analysis protocols that establishes the proof-of-concept for a promising technique, labeled herein Acoustic Mapping Velocimetry (AMV). The technique estimates bed load rates in rivers developing bed forms using a nonintrusive measurements approach. The raw information for AMV is collected with acoustic multibeam technology that in turn provides maps of the bathymetry over longitudinal swaths. As long as the acoustic maps can be acquired relatively quickly and the repetition rate for the mapping is commensurate with the movement of the bed forms, successive acoustic maps capture the progression of the bed form movement. Two-dimensional velocity maps associated with the bed form migration are obtained by implementing algorithms typically used in particle image velocimetry to acoustic maps converted in gray-level images. Furthermore, use of the obtained acoustic and velocity maps in conjunction with analytical formulations (e.g., Exner equation) enables estimation of multidirectional bed load rates over the whole imaged area. This paper presents a validation study of the AMV technique using a set of laboratory experiments.

  14. Association mapping in cacao

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Association mapping is becoming important in perennial crops because it is a better alternative to the classical QTL's mapping approaches. The development of large breeding populations (F2, backcrosses and recombinant inbred populations) is a requirement of QTL's discovery; however, this process req...

  15. Mapping of Outdoor Classrooms.

    ERIC Educational Resources Information Center

    Horvath, Victor G.

    Mapping symbols adopted by the Michigan Department of Natural Resources are presented with their explanations. In an effort to provide standardization and familiarity teachers and other school people involved in an outdoor education program are encouraged to utilize the same symbols in constructing maps. (DK)

  16. Mapping the Llano Estacado

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Early maps of North America, prepared in the 18th and early 19th centuries, often depicted the Llano Estacado as a conspicuous blank spot - a terra incognita. A good example is a map of the southwest sketched by Alexander von Humboldt in 1804. In 1830, Stephen F. Austin added little detail to the ...

  17. Mapping Microbial Biodiversity

    SciTech Connect

    Stoner, Daphne Lisabet; Micah C. Geary; White, Luke James; Lee, Randy Dean; Brizzee, Julie Ann; Rodman, A. C.; Rope, Ronald C

    2001-09-01

    We report the development of a prototype database that "maps" microbial diversity in the context of the geochemical and geological environment and geographic location. When it is fully implemented, scientists will be able to conduct database searches, construct maps containing the information of interest, download files, and enter data over the Internet.

  18. Reliability of Current Biokinetic and Dosimetric Models for Radionuclides: A Pilot Study

    SciTech Connect

    Leggett, Richard Wayne; Eckerman, Keith F; Meck, Robert A.

    2008-10-01

    This report describes the results of a pilot study of the reliability of the biokinetic and dosimetric models currently used by the U.S. Nuclear Regulatory Commission (NRC) as predictors of dose per unit internal or external exposure to radionuclides. The study examines the feasibility of critically evaluating the accuracy of these models for a comprehensive set of radionuclides of concern to the NRC. Each critical evaluation would include: identification of discrepancies between the models and current databases; characterization of uncertainties in model predictions of dose per unit intake or unit external exposure; characterization of variability in dose per unit intake or unit external exposure; and evaluation of prospects for development of more accurate models. Uncertainty refers here to the level of knowledge of a central value for a population, and variability refers to quantitative differences between different members of a population. This pilot study provides a critical assessment of models for selected radionuclides representing different levels of knowledge of dose per unit exposure. The main conclusions of this study are as follows: (1) To optimize the use of available NRC resources, the full study should focus on radionuclides most frequently encountered in the workplace or environment. A list of 50 radionuclides is proposed. (2) The reliability of a dose coefficient for inhalation or ingestion of a radionuclide (i.e., an estimate of dose per unit intake) may depend strongly on the specific application. Multiple characterizations of the uncertainty in a dose coefficient for inhalation or ingestion of a radionuclide may be needed for different forms of the radionuclide and different levels of information of that form available to the dose analyst. (3) A meaningful characterization of variability in dose per unit intake of a radionuclide requires detailed information on the biokinetics of the radionuclide and hence is not feasible for many infrequently

  19. A motion phantom study on helical tomotherapy: the dosimetric impacts of delivery technique and motion

    NASA Astrophysics Data System (ADS)

    Kanagaki, Brian; Read, Paul W.; Molloy, Janelle A.; Larner, James M.; Sheng, Ke

    2007-01-01

    Helical tomotherapy (HT) can potentially be used for lung cancer treatment including stereotactic radiosurgery because of its advanced image guidance and its ability to deliver highly conformal dose distributions. However, previous theoretical and simulation studies reported that the effect of respiratory motion on statically planned tomotherapy treatments may cause substantial differences between the calculated and actual delivered radiation isodose distribution, particularly when the treatment is hypofractionated. In order to determine the dosimetric effects of motion upon actual HT treatment delivery, phantom film dosimetry measurements were performed under static and moving conditions using a clinical HT treatment unit. The motion phantom system was constructed using a programmable motor, a base, a moving platform and a life size lung heterogeneity phantom with wood inserts representing lung tissue with a 3.0 cm diameter spherical tumour density equivalent insert. In order to determine the effects of different motion and tomotherapy delivery parameters, treatment plans were created using jaw sizes of 1.04 cm and 2.47 cm, with incremental gantry rotation periods between the minimum allowed (10 s) and the maximum allowed (60 s). The couch speed varied from 0.009 cm s-1 to 0.049 cm s-1, and delivered to a phantom under static and dynamic conditions with peak-to-peak motion amplitudes of 1.2 cm and 2 cm and periods of 3 and 5 s to simulate human respiratory motion of lung tumours. A cylindrical clinical target volume (CTV) was contoured to tightly enclose the tumour insert. 2.0 Gy was prescribed to 95% of the CTV. Two-dimensional dose was measured by a Kodak EDR2 film. Dynamic phantom doses were then quantitatively compared to static phantom doses in terms of axial dose profiles, cumulative dose volume histograms (DVH), percentage of CTV receiving the prescription dose and the minimum dose received by 95% of the CTV. The larger motion amplitude resulted in more

  20. Dosimetric evaluation of the staff working in a PET/CT department

    NASA Astrophysics Data System (ADS)

    Dalianis, K.; Malamitsi, J.; Gogou, L.; Pagou, M.; Efthimiadou, R.; Andreou, J.; Louizï, A.; Georgiou, E.

    2006-12-01

    The dosimetric literature data concerning the medical personnel working in positron emission tomography/computed tomography (PET/CT) departments are limited. Therefore, we measured the radiation dose of the staff working in the first PET/CT department in Greece at the Diagnostic and Therapeutic Center of Athens HYGEIA—Harvard Medical International. As, for the time being, only 2-deoxy-2-[ 18F]fluoro-d-glucose (FDG) PET studies are performed, radiation dose measurements concern those derived from dispensing of the radiopharmaceutical as well as from the patients undergoing FDG-PET imaging. Our aim is to develop more effective protective measures against radionuclide exposure. To estimate the effective dose from external exposure, all seven members of the staff (two nurses, two medical physicists, two technologists, one secretary) had TLD badges worn at the upper pocket of their overall, TLD rings on the right hand and digital dosimeters at their upper side pocket. In addition, isodose curves were measured with thermoluminescence detectors for distances of 20, 50, 70 and 100 cm away from patients who had been injected with 18F-FDG. Dose values of the PET/CT staff were measured with digital detectors, TLD badges and TLD rings over the first 8 months for a total of 160 working days of the department's operation, consisting of a workload of about 10-15 patients/week who received 250-420 MBq of 18F-FDG each. Whole - body collective doses and hand doses for the staff were the following: Nurse #1 received 1.6 mSv as a whole body dose and 2,1 as a hand dose, Nurse #2 received 1.9 and 2.4 mSv respectively. For medical physicist #1 the dose values were 1.45 mSv whole body and 1.7 mSv hand dose, for medical physicist #2 1.67 mSv wholebody dose and 1.55 mSv hand dose and for technologists #1 & #2 the whole body doses were 0.7 and 0.64 mSv respectively. Lastly, the secretary received 0.1 mSv whole body dose. These preliminary data have shown that the dose levels of our PET

  1. Dosimetric evaluation of three adaptive strategies for prostate cancer treatment including pelvic lymph nodes irradiation

    SciTech Connect

    Cantin, Audrey; Gingras, Luc; Archambault, Louis; Lachance, Bernard; Foster, William; Goudreault, Julie

    2015-12-15

    Purpose: The movements of the prostate relative to the pelvic lymph nodes during intensity-modulated radiation therapy treatment can limit margin reduction and affect the protection of the organs at risk (OAR). In this study, the authors performed an analysis of three adaptive treatment strategies that combine information from both bony and gold marker registrations. The robustness of those treatments against the interfraction prostate movements was evaluated. Methods: A retrospective study was conducted on five prostate cancer patients with 7–13 daily cone-beam CTs (CBCTs). The clinical target volumes (CTVs) consisting of pelvic lymph nodes, prostate, and seminal vesicles as well as the OARs were delineated on each CBCT and the initial CT. Three adaptive strategies were analyzed. Two of these methods relied on a two-step patient positioning at each fraction. First step: a bony registration was used to deliver the nodal CTV prescription. Second step: a gold marker registration was then used either to (1) complete the dose delivered to the prostate (complement); (2) or give almost the entire prescription to the prostate with a weak dose gradient between the targets to compensate for possible motions (gradient). The third method (COR) used a pool of precalculated plans based on images acquired at previous treatment fractions. At each new fraction, a plan is selected from that pool based on the daily position of prostate center-of-mass. The dosimetric comparison was conducted and results are presented with and without the systematic shift in the prostate position on the CT planning. The adaptive strategies were compared to the current clinical standard where all fractions are treated with the initial nonadaptive plan. Results: The minimum daily prostate D{sub 95%} is improved by 2%, 9%, and 6% for the complement, the gradient, and the COR approaches, respectively, compared to the nonadaptive method. The average nodal CTV D{sub 95%} remains constant across the

  2. Dosimetric aspects of inverse-planned modulated-arc total-body irradiation

    SciTech Connect

    Held, Mareike; Kirby, Neil; Morin, Olivier; Pouliot, Jean

    2012-08-15

    Purpose: To develop optimal beam parameters and to verify the dosimetric aspects of the recently developed modulated-arc total-body irradiation (MATBI) technique, which delivers an inverse-planned dose to the entire body using gantry rotation. Methods: The patient is positioned prone and supine underneath the gantry at about 2 m source-to-surface distance (SSD). Then, up to 28 beams irradiate the patient from different gantry angles. Based on full-body computed-tomography (CT) images of the patient, the weight of each beam is optimized, using inverse planning, to create a uniform body dose. This study investigates how to best simulate patients and the ideal beam setup parameters, such as field size, number of beams, and beam geometry, for treatment time and dose homogeneity. In addition, three anthropomorphic water phantoms were constructed and utilized to verify the accuracy of dose delivery, with both diode array and ion chamber measurements. Furthermore, to improve the accuracy of the new technique, a beam model is created specifically for the extended-SSD positioning for MATBI. Results: Low dose CT scans can be utilized for dose calculations without affecting the accuracy. The largest field size of 40 Multiplication-Sign 40 cm{sup 2} was found to deliver the most uniform dose in the least amount of time. Moreover, a higher number of beams improves dose homogeneity. The average dose discrepancy between ion chamber measurements and extended-SSD beam model calculations was 1.2%, with the largest discrepancy being 3.2%. This average dose discrepancy was 1.4% with the standard beam model for delivery at isocenter. Conclusions: The optimum beam setup parameters, regarding dose uniformity and treatment duration, are laid out for modulated-arc TBI. In addition, the presented dose measurements show that these treatments can be delivered accurately. These measurements also indicated that a new beam model did not significantly improve the accuracy of dose calculations

  3. Dosimetric characterization of whole brain radiotherapy of pediatric patients using modulated proton beams.

    PubMed

    Jin, Hosang; Hsi, Wen; Yeung, Daniel; Li, Zuofeng; Mendenhall, Nancy P; Marcus, Robert B

    2011-01-01

    This study was designed to investigate dosimetric variations between proton plans with (PPW) and without (PPWO), a compensator for whole brain radiotherapy (WBRT). The retrospective study on PPW and PPWO in Eclipse and XiO systems and photon plans (XP) using controlled segments in Pinnacle system was performed on nine pediatric patients for craniospinal irradiations. DVHs and derived metrics, such as the homogeneity index (HI), the doses to 2% (D(2%)) and 5% (D(5%)) volumes, and mean dose (D(mean)) of the whole brain (i.e., PTV), and the organs at risk (OARs) such as lens and skull, were obtained. The PPW plans from both Eclipse and XiO systems uncovered the following advantages: (1) encompassing a cribriform plate area with the 100% isodose line was better than either PPWO or XP, according to calculated two-dimensional distributions of one patient; (2) the mean value of D(5%) for lens was reduced to 23.6% of D(P) from 54.1% for PPWO or 41.6% for XP; and (3) the mean value of D(mean) for skull was reduced to 94.8% of D(P) from either 98.4% for PPWO or 98.3% for XP. However, the PPW plans also exposed several disadvantages including: (1) the HI of PTV increased to 7.7 from 4.7 for PPWO or 3.7 for XP; (2) D(2%) to PTV increased to 108.8% of D(P) from 104.8% for PPWO or 105.1% for XP; and (3) D(5%) to the skull increased to 104.9% of D(P) from 101.6% for PPWO or 103.4% of for XP. One-half of the observed variations were caused by different penumbra on lateral profiles and distal fall-off depth doses of protons in Eclipse and XiO. Because the utilization on the sharp proton distal fall-off was limited for WBRT, the difference between PPW and PPWO or XP indicated no distinguishable improvement by using a compensator in proton plans. PMID:21587172

  4. Integral test phantom for dosimetric quality assurance of image guided and intensity modulated stereotactic radiotherapy

    SciTech Connect

    Letourneau, Daniel; Keller, Harald; Sharpe, Michael B.; Jaffray, David A.

    2007-05-15

    The objective of this work is to develop a dosimetric phantom quality assurance (QA) of linear accelerators capable of cone-beam CT (CBCT) image guided and intensity-modulated radiotherapy (IG-IMRT). This phantom is to be used in an integral test to quantify in real-time both the performance of the image guidance and the dose delivery systems in terms of dose localization. The prototype IG-IMRT QA phantom consisted of a cylindrical imaging phantom (CatPhan) combined with an array of 11 radiation diodes mounted on a 10 cm diameter disk, oriented perpendicular to the phantom axis. Basic diode response characterization was performed for 6 and 18 MV photons. The diode response was compared to planning system calculations in the open and penumbrae regions of simple and complex beam arrangements. The clinical use of the QA phantom was illustrated in an integral test of an IG-IMRT treatment designed for a clinical spinal radiosurgery case. The sensitivity of the phantom to multileaf collimator (MLC) calibration and setup errors in the clinical setting was assessed by introducing errors in the IMRT plan or by displacing the phantom. The diodes offered good response linearity and long-term reproducibility for both 6 and 18 MV. Axial dosimetry of coplanar beams (in a plane containing the beam axes) was made possible with the nearly isoplanatic response of the diodes over 360 deg. of gantry (usually within {+-}1%). For single beam geometry, errors in phantom placement as small as 0.5 mm could be accurately detected (in gradient {>=}1%/mm). In clinical setting, MLC systematic errors of 1 mm on a single MLC bank introduced in the IMRT plan were easily detectable with the QA phantom. The QA phantom demonstrated also sufficient sensitivity for the detection of setup errors as small as 1 mm for the IMRT delivery. These results demonstrated that the prototype can accurately and efficiently verify the entire IG-IMRT process. This tool, in conjunction with image guidance capabilities

  5. Dosimetric Study of Pelvic Proton Radiotherapy for High-Risk Prostate Cancer

    SciTech Connect

    Chera, Bhishamjit S.; Vargas, Carlos; Morris, Christopher G.; Louis, Debbie; Flampouri, Stella; Yeung, Daniel; Duvvuri, Srividya; Li Zuofeng; Mendenhall, Nancy Price

    2009-11-15

    Purpose: To compare dose distributions in targeted tissues (prostate, seminal vesicles, pelvic regional nodes) and nontargeted tissues in the pelvis with intensity-modulated radiotherapy (IMRT) and forward-planned, double-scattered, three-dimensional proton radiotherapy (3D-PRT). Methods and Materials: IMRT, IMRT followed by a prostate 3D-PRT boost (IMRT/3D-PRT), and 3D-PRT plans were created for 5 high-risk prostate cancer patients (n = 15 plans). A 78-CGE/Gy dose was prescribed to the prostate and proximal seminal vesicles and a 46-CGE/Gy was prescribed to the pelvic nodes. Various dosimetric endpoints were compared. Results: Target coverage of the prostate and nodal planning target volumes was adequate for all three plans. Compared with the IMRT and IMRT/3D-PRT plans, the 3D-PRT plans reduced the mean dose to the rectum, rectal wall, bladder, bladder wall, small bowel, and pelvis. The relative benefit of 3D-PRT (vs IMRT) at reducing the rectum and rectal wall V5-V40 was 53% to 71% (p < 0.05). For the bladder and bladder wall, the relative benefit for V5 to V40 CGE/Gy was 40% to 63% (p < 0.05). The relative benefit for reducing the volume of small bowel irradiated from 5 to 30 CGE/Gy in the 3D-PRT ranged from 62% to 69% (p < 0.05). Use of 3D-PRT did not produce the typical low-dose 'bath' of radiation to the pelvis seen with IMRT. Femoral head doses were higher for the 3D-PRT. Conclusions: Use of 3D-PRT significantly reduced the dose to normal tissues in the pelvis while maintaining adequate target coverage compared with IMRT or IMRT/3D-PRT. When treating the prostate, seminal vesicles, and pelvic lymph nodes in prostate cancer, proton therapy may improve the therapeutic ratio beyond what is possible with IMRT.

  6. Changes in optically stimulated luminescent dosimeter (OSLD) dosimetric characteristics with accumulated dose

    SciTech Connect

    Jursinic, Paul A.

    2010-01-15

    Purpose: A new type of in vivo dosimeter, an optically stimulated luminescent dosimeter (OSLD), has now become commercially available for clinical use. The OSLD is a plastic disk infused with aluminum oxide doped with carbon (Al{sub 2}O{sub 3}:C). Crystals of Al{sub 2}O{sub 3}:C, when exposed to ionizing radiation, store energy that is released as luminescence (420 nm) when the OSLD is illuminated with stimulation light (540 nm). The intensity of the luminescence depends on the dose absorbed by the OSLD and the intensity of the stimulation light. The effects of accumulated dose on OSLD response were investigated. Methods: The OSLDs used in this work were nanodot dosimeters, which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x rays and gamma rays from Co-60 and Ir-192. The signal on the OSLDs after irradiation is removed by optical annealing with a 150 W tungsten-halogen lamp or a 14 W compact fluorescent lamp was investigated. Results: It was found that OSLD response to dose was supralinear and this response was altered with the amount of accumulated dose to the OSLD. The OSLD response can be modeled by a quadratic and an exponential equation. For accumulated doses up to 60 Gy, the OSLD sensitivity (counts/dose) decreases and the extent of supralinear increases. Above 60 Gy of accumulated dose the sensitivity increases and the extent of supralinearity decreases or reaches a plateau, depending on how the OSLDs were optically annealed. With preirradiation of OSLDs with greater than 1 kGy, it is found that the sensitivity reaches a plateau 2.5 folds greater than that of an OSLD with no accumulated dose and the supralinearity disappears. A regeneration of the luminescence signal in the dark after full optical annealing occurs with a half time of about two days. The extent of this regeneration signal depends on the amount of accumulated dose. Conclusions: For in vivo dosimetric measurements, a precision of

  7. Dosimetric characterization and output verification for conical brachytherapy surface applicators. Part I. Electronic brachytherapy source

    PubMed Central

    Fulkerson, Regina K.; Micka, John A.; DeWerd, Larry A.

    2014-01-01

    Purpose: Historically, treatment of malignant surface lesions has been achieved with linear accelerator based electron beams or superficial x-ray beams. Recent developments in the field of brachytherapy now allow for the treatment of surface lesions with specialized conical applicators placed directly on the lesion. Applicators are available for use with high dose rate (HDR) 192Ir sources, as well as electronic brachytherapy sources. Part I of this paper will discuss the applicators used with electronic brachytherapy sources; Part II will discuss those used with HDR 192Ir sources. Although the use of these applicators has gained in popularity, the dosimetric characteristics including depth dose and surface dose distributions have not been independently verified. Additionally, there is no recognized method of output verification for quality assurance procedures with applicators like these. Existing dosimetry protocols available from the AAPM bookend the cross-over characteristics of a traditional brachytherapy source (as described by Task Group 43) being implemented as a low-energy superficial x-ray beam (as described by Task Group 61) as observed with the surface applicators of interest. Methods: This work aims to create a cohesive method of output verification that can be used to determine the dose at the treatment surface as part of a quality assurance/commissioning process for surface applicators used with HDR electronic brachytherapy sources (Part I) and 192Ir sources (Part II). Air-kerma rate measurements for the electronic brachytherapy sources were completed with an Attix Free-Air Chamber, as well as several models of small-volume ionization chambers to obtain an air-kerma rate at the treatment surface for each applicator. Correction factors were calculated using MCNP5 and EGSnrc Monte Carlo codes in order to determine an applicator-specific absorbed dose to water at the treatment surface from the measured air-kerma rate. Additionally, relative dose

  8. Dosimetric analysis of the carousel setup for the exposure of rats at 1.62 GHz.

    PubMed

    Schönborn, Frank; Poković, Katja; Kuster, Niels

    2004-01-01

    The so-called carousel setup has been widely utilized for testing the hypotheses of adverse health effects on the central nervous system (CNS) due to mobile phone exposures in the frequency bands 800-900 MHz. The objectives of this article were to analyze the suitability of the setup for the upper mobile frequency range, i.e., 1.4-2 GHz, and to conduct a detailed experimental and numerical dosimetry for the setup at the IRIDIUM frequency band of 1.62 GHz. The setup consists of a plastic base on which ten rats, restrained in radially positioned tubes, are exposed to the electromagnetic field emanating from a sleeved dipole antenna at the center. Latest generation miniaturized dosimetric E field and temperature probes were used to measure the specific absorption rate (SAR) inside the brain of three rat cadavers of the Lewis strain and two rat cadavers of the Fisher 344 strain. A numerical analysis was conducted on the basis of three numerical rat phantoms with voxel sizes between 1.5 and 0.125 mm3 that are based on high resolution MRI scans of a 300 g male Wistar rat and a 370 g male Sprague-Dawley rat. The average of the assessed SAR values in the brain was 2.8 mW/g per W antenna input power for adult rats with masses between 220 and 350 g and 5.3 mW/g per W antenna input power for a juvenile rat with a mass of 95 g. The strong increase of the SAR in the brain with decreasing animal size was verified by simulations of the absorption in numerical phantoms scaled to sizes between 100 and 500 g with three different scaling methods. The study also demonstrated that current rat phantom models do not provide sufficient spatial resolution to perform absolute SAR assessment for the brain tissue. The variation of the SAR(brain)(av) due to changes in position was assessed to be in the range from +15% to -30%. A study on the dependence of the performance of the carousel setup on the frequency revealed that efficiency, defined as SAR(brain)(av) per W antenna input power, and

  9. Dosimetric advantages of proton therapy compared with photon therapy using an adaptive strategy in cervical cancer.

    PubMed

    van de Schoot, Agustinus J A J; de Boer, Peter; Crama, Koen F; Visser, Jorrit; Stalpers, Lukas J A; Rasch, Coen R N; Bel, Arjan

    2016-07-01

    Background Image-guided adaptive proton therapy (IGAPT) can potentially be applied to take into account interfraction motion while limiting organ at risk (OAR) dose in cervical cancer radiation therapy (RT). In this study, the potential dosimetric advantages of IGAPT compared with photon-based image-guided adaptive RT (IGART) were investigated. Material and methods For 13 cervical cancer patients, full and empty bladder planning computed tomography (CT) images and weekly CTs were acquired. Based on both primary clinical target volumes (pCTVs) [i.e. gross tumor volume (GTV), cervix, corpus-uterus and upper part of the vagina] on planning CTs, the pretreatment observed full range primary internal target volume (pITV) was interpolated to derive pITV subranges. Given corresponding ITVs (i.e. pITVs including lymph nodes), patient-specific photon and proton plan libraries were generated. Using all weekly CTs, IGART and IGAPT treatments were simulated by selecting library plans and recalculating the dose. For each recalculated IGART and IGAPT fraction, CTV (i.e. pCTV including lymph nodes) coverage was assessed and differences in fractionated substitutes of dose-volume histogram (DVH) parameters (V15Gy, V30Gy, V45Gy, Dmean, D2cc) for bladder, bowel and rectum were tested for significance (Wilcoxon signed-rank test). Also, differences in toxicity-related DVH parameters (rectum V30Gy, bowel V45Gy) were approximated based on accumulated dose distributions. Results In 92% (96%) of all recalculated IGAPT (IGART) fractions adequate CTV coverage (V95% >98%) was obtained. All dose parameters for bladder, bowel and rectum, except the fractionated substitute for rectum V45Gy, were improved using IGAPT. Also, IGAPT reduced the mean dose to bowel, bladder and rectum significantly (p < 0.01). In addition, an average decrease of rectum V30Gy and bowel V45Gy indicated reductions in toxicity probabilities when using IGAPT. Conclusion This study demonstrates the feasibility of IGAPT

  10. Dosimetric characterization of GafChromic EBT film and its implication on film dosimetry quality assurance

    NASA Astrophysics Data System (ADS)

    Fuss, Martina; Sturtewagen, Eva; DeWagter, Carlos; Georg, Dietmar

    2007-07-01

    , presents a versatile system for high-precision dosimetry in two dimensions, provided that the intrinsic behaviour of the film reading device is taken into account. EBT film itself presents substantial improvements on formerly available models of radiographic and a radiochromic film and its dosimetric characteristics allow us to measure absorbed dose levels in a large variety of situations with a single calibration curve.

  11. Spine Radiosurgery: A Dosimetric Analysis in 124 Patients Who Received 18 Gy

    SciTech Connect

    Schipani, Stefano; Wen, Winston; Jin, Jain-Yue; Kim, Jin Koo; Ryu, Samuel

    2012-12-01

    Purpose: To define the safely tolerated doses to organs at risk (OARs) adjacent to the target volume (TV) of spine radiosurgery (SRS) with 18-Gy in a single fraction. Methods and Materials: A total of 124 patient cases with 165 spine metastases were reviewed. An 18-Gy single-fraction regimen was prescribed to the 90% isodose line encompassing the TV. A constraint of 10 Gy to 10% of the spinal cord outlined 6 mm above and below the TV was used. Dosimetric data to OARs were analyzed. Results: A total of 124 patients (100%) were followed-up, and median follow-up time was 7 months (1-50 months). Symptoms and local control were achieved in 114 patients (92%). Acute Radiation Therapy Oncology Group (RTOG) grade 1 oral mucositis occurred in 11 of 11 (100%) patients at risk for oropharyngeal toxicity after cervical spine treatment. There were no RTOG grade 2-4 acute or late complications. Median TV was 43.2 cc (5.3-175.4 cc) and 90% of the TV received median dose of 19 Gy (17-19.8 Gy). Median (range) of spinal cord maximum dose (Dmax), dose to spinal cord 0.35 cc (Dsc0.35), and cord volume receiving 10 Gy (Vsc10) were 13.8 Gy (5.4-21 Gy), 8.9 Gy (2.6-11.4 Gy) and 0.33 cc (0-1.6 cc), respectively. Other OARs were evaluated when in proximity to the TV. Esophagus (n=58), trachea (n=28), oropharynx (n=11), and kidneys (n=34) received median (range) V10 and V15 of 3.1 cc (0-5.8 cc) and 1.2 cc (0-2.9 cc), 2.8 cc (0-4.9 cc), and 0.8 cc (0-2.1 cc), 3.4 cc (0-6.2 cc) and 1.6 cc (0-3.2 cc), 0.3 cc (0-0.8 cc) and 0.08 cc (0-0.1 cc), respectively. Conclusions: Cord Dmax of 14 Gy and D0.35 of 10 Gy are safe dose constraints for 18-Gy single-fraction SRS. Esophagus V10 of 3 cc and V15 of 1 cc, trachea V10 of 3 cc, and V15 of 1 cc, oropharynx V10 of 3.5 cc and V15 of 1.5 cc, kidney V10 of 0.3 cc, and V15 of 0.1 cc are planning guidelines when these OARs are in proximity to the TV.

  12. TH-A-9A-03: Dosimetric Effect of Rotational Errors for Lung Stereotactic Body Radiotherapy

    SciTech Connect

    Lee, J; Kim, H; Park, J; Kim, J; Kim, H; Ye, S

    2014-06-15

    Purpose: To evaluate the dosimetric effects on target volume and organs at risk (OARs) due to roll rotational errors in treatment setup of stereotactic body radiation therapy (SBRT) for lung cancer. Methods: There were a total of 23 volumetric modulated arc therapy (VMAT) plans for lung SBRT examined in this retrospective study. Each CT image of VMAT plans was intentionally rotated by ±1°, ±2°, and ±3° to simulate roll rotational setup errors. The axis of rotation was set at the center of T-spine. The target volume and OARs in the rotated CT images were re-defined by deformable registration of original contours. The dose distributions on each set of rotated images were re-calculated to cover the planning target volume (PTV) with the prescription dose before and after the couch translational correction. The dose-volumetric changes of PTVs and spinal cords were analyzed. Results: The differences in D95% of PTVs by −3°, −2°, −1°, 1°, 2°, and 3° roll rotations before the couch translational correction were on average −11.3±11.4%, −5.46±7.24%, −1.11±1.38% −3.34±3.97%, −9.64±10.3%, and −16.3±14.7%, respectively. After the couch translational correction, those values were −0.195±0.544%, −0.159±0.391%, −0.188±0.262%, −0.310±0.270%, −0.407±0.331%, and −0.433±0.401%, respectively. The maximum dose difference of spinal cord among the 23 plans even after the couch translational correction was 25.9% at −3° rotation. Conclusions: Roll rotational setup errors in lung SBRT significantly influenced the coverage of target volume using VMAT technique. This could be in part compensated by the translational couch correction. However, in spite of the translational correction, the delivered doses to the spinal cord could be more than the calculated doses. Therefore if rotational setup errors exist during lung SBRT using VMAT technique, the rotational correction would rather be considered to prevent over-irradiation of normal

  13. Dosimetric properties of a proton beamline dedicated to the treatment of ocular disease

    SciTech Connect

    Slopsema, R. L. Mamalui, M.; Yeung, D.; Malyapa, R.; Li, Z.; Zhao, T.

    2014-01-15

    Purpose: A commercial proton eyeline has been developed to treat ocular disease. Radiotherapy of intraocular lesions (e.g., uveal melanoma, age-related macular degeneration) requires sharp dose gradients to avoid critical structures like the macula and optic disc. A high dose rate is needed to limit patient gazing times during delivery of large fractional dose. Dose delivery needs to be accurate and predictable, not in the least because current treatment planning algorithms have limited dose modeling capabilities. The purpose of this paper is to determine the dosimetric properties of a new proton eyeline. These properties are compared to those of existing systems and evaluated in the context of the specific clinical requirements of ocular treatments. Methods: The eyeline is part of a high-energy, cyclotron-based proton therapy system. The energy at the entrance of the eyeline is 105 MeV. A range modulator (RM) wheel generates the spread-out Bragg peak, while a variable range shifter system adjusts the range and spreads the beam laterally. The range can be adjusted from 0.5 up to 3.4 g/cm{sup 2}; the modulation width can be varied in steps of 0.3 g/cm{sup 2} or less. Maximum field diameter is 2.5 cm. All fields can be delivered with a dose rate of 30 Gy/min or more. The eyeline is calibrated according to the IAEA TRS-398 protocol using a cylindrical ionization chamber. Depth dose distributions and dose/MU are measured with a parallel-plate ionization chamber; lateral profiles with radiochromic film. The dose/MU is modeled as a function of range, modulation width, and instantaneous MU rate with fit parameters determined per option (RM wheel). Results: The distal fall-off of the spread-out Bragg peak is 0.3 g/cm{sup 2}, larger than for most existing systems. The lateral penumbra varies between 0.9 and 1.4 mm, except for fully modulated fields that have a larger penumbra at skin. The source-to-axis distance is found to be 169 cm. The dose/MU shows a strong dependence

  14. Dosimetric evaluation of new approaches in GRID therapy using nonconventional radiation sources

    SciTech Connect

    Martínez-Rovira, I. Prezado, Y.; Fois, G.

    2015-02-15

    Purpose: Spatial fractionation of the dose has proven to be a promising approach to increase the tolerance of healthy tissue, which is the main limitation of radiotherapy. A good example of that is GRID therapy, which has been successfully used in the management of large tumors with low toxicity. The aim of this work is to explore new avenues using nonconventional sources: GRID therapy by using kilovoltage (synchrotron) x-rays, the use of very high-energy electrons, and proton GRID therapy. They share in common the use of the smallest possible grid sizes in order to exploit the dose–volume effects. Methods: Monte Carlo simulations (PENELOPE/PENEASY and GEANT4/GATE codes) were used as a method to study dose distributions resulting from irradiations in different configurations of the three proposed techniques. As figure of merit, percentage (peak and valley) depth dose curves, penumbras, and central peak-to-valley dose ratios (PVDR) were evaluated. As shown in previous biological experiments, high PVDR values are requested for healthy tissue sparing. A superior tumor control may benefit from a lower PVDR. Results: High PVDR values were obtained in the healthy tissue for the three cases studied. When low energy photons are used, the treatment of deep-seated tumors can still be performed with submillimetric grid sizes. Superior PVDR values were reached with the other two approaches in the first centimeters along the beam path. The use of protons has the advantage of delivering a uniform dose distribution in the tumor, while healthy tissue benefits from the spatial fractionation of the dose. In the three evaluated techniques, there is a net reduction in penumbra with respect to radiosurgery. Conclusions: The high PVDR values in the healthy tissue and the use of small grid sizes in the three presented approaches might constitute a promising alternative to treat tumors with such spatially fractionated radiotherapy techniques. The dosimetric results presented here

  15. Dosimetric characterization and output verification for conical brachytherapy surface applicators. Part I. Electronic brachytherapy source

    SciTech Connect

    Fulkerson, Regina K. Micka, John A.; DeWerd, Larry A.

    2014-02-15

    Purpose: Historically, treatment of malignant surface lesions has been achieved with linear accelerator based electron beams or superficial x-ray beams. Recent developments in the field of brachytherapy now allow for the treatment of surface lesions with specialized conical applicators placed directly on the lesion. Applicators are available for use with high dose rate (HDR){sup 192}Ir sources, as well as electronic brachytherapy sources. Part I of this paper will discuss the applicators used with electronic brachytherapy sources; Part II will discuss those used with HDR {sup 192}Ir sources. Although the use of these applicators has gained in popularity, the dosimetric characteristics including depth dose and surface dose distributions have not been independently verified. Additionally, there is no recognized method of output verification for quality assurance procedures with applicators like these. Existing dosimetry protocols available from the AAPM bookend the cross-over characteristics of a traditional brachytherapy source (as described by Task Group 43) being implemented as a low-energy superficial x-ray beam (as described by Task Group 61) as observed with the surface applicators of interest. Methods: This work aims to create a cohesive method of output verification that can be used to determine the dose at the treatment surface as part of a quality assurance/commissioning process for surface applicators used with HDR electronic brachytherapy sources (Part I) and{sup 192}Ir sources (Part II). Air-kerma rate measurements for the electronic brachytherapy sources were completed with an Attix Free-Air Chamber, as well as several models of small-volume ionization chambers to obtain an air-kerma rate at the treatment surface for each applicator. Correction factors were calculated using MCNP5 and EGSnrc Monte Carlo codes in order to determine an applicator-specific absorbed dose to water at the treatment surface from the measured air-kerma rate. Additionally

  16. Assessing the Dosimetric Impact of Real-Time Prostate Motion During Volumetric Modulated Arc Therapy

    SciTech Connect

    Azcona, Juan Diego; Xing, Lei; Chen, Xin; Bush, Karl; Li, Ruijiang

    2014-04-01

    Purpose: To develop a method for dose reconstruction by incorporating the interplay effect between aperture modulation and target motion, and to assess the dosimetric impact of real-time prostate motion during volumetric modulated arc therapy (VMAT). Methods and Materials: Clinical VMAT plans were delivered with the TrueBeam linac for 8 patients with prostate cancer. The real-time target motion during dose delivery was determined based on the 2-dimensional fiducial localization using an onboard electronic portal imaging device. The target shift in each image was correlated with the control point with the same gantry angle in the VMAT plan. An in-house-developed Monte Carlo simulation tool was used to calculate the 3-dimensional dose distribution for each control point individually, taking into account the corresponding real-time target motion (assuming a nondeformable target with no rotation). The delivered target dose was then estimated by accumulating the dose from all control points in the plan. On the basis of this information, dose–volume histograms and 3-dimensional dose distributions were calculated to assess their degradation from the planned dose caused by target motion. Thirty-two prostate motion trajectories were analyzed. Results: The minimum dose to 0.03 cm{sup 3} of the gross tumor volume (D{sub 0.03cc}) was only slightly degraded after taking motion into account, with a minimum value of 94.1% of the planned dose among all patients and fractions. However, the gross tumor volume receiving prescription dose (V{sub 100%}) could be largely affected by motion, dropping below 60% in 1 trajectory. We did not observe a correlation between motion magnitude and dose degradation. Conclusions: Prostate motion degrades the delivered dose to the target in an unpredictable way, although its effect is reduced over multiple fractions, and for most patients the degradation is small. Patients with greater prostate motion or those treated with stereotactic body

  17. A feasibility study of using couch-based real time dosimetric device in external beam radiotherapy

    SciTech Connect

    Prabhakar, Ramachandran; Cramb, Jim; Kron, Tomas

    2011-12-15

    Purpose: Measurement of actual dose delivered during radiotherapy treatment aids in checking the accuracy of dose delivered to the patient. In this study, a couch-based real time dosimetric device has been proposed to measure the exit or entrance dose to a patient during external beam radiotherapy. The utility and feasibility of such a device using a 2D array of diodes has been demonstrated. Methods: Two MAPCHECK devices: MAPCHECK (1175) and MAPCHECK 2 (both SunNuclear) were embedded in a foam block in the treatment couch of a Varian 21iX linear accelerator. The angular dependence of the detector response for both devices was studied before implementing the MAPCHECKs for experimental purposes. An Alderson Rando head phantom was scanned with the MAPCHECK and MAPCHECK 2 devices separately and four different treatment plans were generated with target volumes at three different positions simulating typical clinical situations. The analytical anisotropic algorithm (AAA) was used to compute the doses in an Eclipse treatment planning system (Varian Medical Systems). The Rando phantom with the MAPCHECK device was exposed in Clinac 21iX linear accelerator. The measured dose distribution was compared with the calculated dose distribution to check for the accuracy in dose delivery. Results: Measured and computed dose distribution were found to agree with more than 93% of pixels passing at 3% and 3 mm gamma criteria for all the treatment plans. The couch-based real time dosimetry system may also be applied for noncoplanar beams where electronic portal imaging device (EPID) is not practical to measure the dose. Other advantages include checking the beam stability during the patient treatment, performing routine morning quality assurance (QA) tests in the linear accelerator, and to perform pretreatment verification of intensity modulated radiation therapy (IMRT). One of the drawbacks of this system is that it cannot be used for measuring the dose at 90 deg. or 270 deg. gantry

  18. An evaluation of some pertinent parameters that influence the dosimetric performance of synthetic diamond detectors

    NASA Astrophysics Data System (ADS)

    Ade, N.; Nam, T. L.; Mhlanga, S. H.

    2013-05-01

    correction using the Δ values obtained seemed to worsen the performance of the HPHT sample (up to about 3.3%) but it had a marginal effect on the performance of the CVD sample. In addition, the angular response of the CVD diamond detector was shown to be comparable with that of a cylindrical chamber. This study concludes that once the responses of the diamond detectors have been stabilised and they are properly shielded from ambient light, pre-irradiation prior to each measurement is not required. Also, the relative dose measured with the diamond detectors do not require dose rate dependence corrections as the required correction is only marginal and could have no dosimetric significance.

  19. SU-E-J-56: Dosimetric Impact of Patient Roll Variability in Peripheral-Lung SBRT

    SciTech Connect

    Casto, B; Ying, J; Ku, L

    2014-06-01

    Purpose: Positional variation about the patient longitudinal axis may introduce deleterious effects to clinical treatment plans, the effects of which are exacerbated by hypo-fractionated treatment regimens. Our goal is to evaluate the dosimetric impact of rotational setup error in stereotactic body radiation therapy (SBRT) for peripherally-located lung lesions. Methods: Six patients who had been treated for peripheral lung lesions using varying SBRT techniques were analyzed. Each patient's planning CT was processed using custom in-house software to simulate 1, 3, and 5 degree roll in both directions about their longitudinal axis. The original plan was fused and re-calculated. Agreement between planned and error-simulated dose distributions was quantified using 3%, 3mm criteria for the 3-dimensional gamma metric, and changes in target coverage and adjacent normal anatomy were also quantified. Results: Increased rotational setup error resulted in reduced target coverage, with changes in equivalent uniform dose ranging from −1.24% to −6.11% for simulated roll greater than or equal to 3 degrees, increasing with magnitude of error and skewed for roll directed toward the involved side. Changes to normal tissue metrics are linearly related to simulated roll, with rib D(1cc) changes ranging from −4.23% to 3.27% relative to the original treatment plan. Error-simulated dose distributions demonstrate agreement by the gamma metric in the planned target of 72.56%, 81.02%, and 99.52% for 5, 3, and 1 degree simulated roll scenarios, respectively. Corresponding agreement for the regional dose in excess of 50% of the maximum were 65.71%,70.77%, and 97.88%. Conclusion: This study suggests that the ability to detect and compensate for rotational positioning variations beyond a threshold level may improve care for patients with peripherally-located lesions beyond that which may be accomplished using only translational axes. Positional error of one degree of roll had little

  20. Model-based versus specific dosimetry in diagnostic context: Comparison of three dosimetric approaches

    SciTech Connect

    Marcatili, S. Villoing, D.; Mauxion, T.; Bardiès, M.; McParland, B. J.

    2015-03-15

    Purpose: The dosimetric assessment of novel radiotracers represents a legal requirement in most countries. While the techniques for the computation of internal absorbed dose in a therapeutic context have made huge progresses in recent years, in a diagnostic scenario the absorbed dose is usually extracted from model-based lookup tables, most often derived from International Commission on Radiological Protection (ICRP) or Medical Internal Radiation Dose (MIRD) Committee models. The level of approximation introduced by these models may impact the resulting dosimetry. The aim of this work is to establish whether a more refined approach to dosimetry can be implemented in nuclear medicine diagnostics, by analyzing a specific case. Methods: The authors calculated absorbed doses to various organs in six healthy volunteers administered with flutemetamol ({sup 18}F) injection. Each patient underwent from 8 to 10 whole body 3D PET/CT scans. This dataset was analyzed using a Monte Carlo (MC) application developed in-house using the toolkit GATE that is capable to take into account patient-specific anatomy and radiotracer distribution at the voxel level. They compared the absorbed doses obtained with GATE to those calculated with two commercially available software: OLINDA/EXM and STRATOS implementing a dose voxel kernel convolution approach. Results: Absorbed doses calculated with GATE were higher than those calculated with OLINDA. The average ratio between GATE absorbed doses and OLINDA’s was 1.38 ± 0.34 σ (from 0.93 to 2.23). The discrepancy was particularly high for the thyroid, with an average GATE/OLINDA ratio of 1.97 ± 0.83 σ for the six patients. Differences between STRATOS and GATE were found to be higher. The average ratio between GATE and STRATOS absorbed doses was 2.51 ± 1.21 σ (from 1.09 to 6.06). Conclusions: This study demonstrates how the choice of the absorbed dose calculation algorithm may introduce a bias when gamma radiations are of importance, as is

  1. A Dosimetric Model of Duodenal Toxicity After Stereotactic Body Radiotherapy for Pancreatic Cancer

    SciTech Connect

    Murphy, James D.; Christman-Skieller, Claudia; Kim, Jeff; Dieterich, Sonja; Chang, Daniel T.; Koong, Albert C.

    2010-12-01

    Introduction: Dose escalation for pancreas cancer is limited by the tolerance of adjacent normal tissues, especially with stereotactic body radiotherapy (SBRT). The duodenum is generally considered to be the organ at greatest risk. This study reports on the dosimetric determinants of duodenal toxicity with single-fraction SBRT. Methods and Materials: Seventy-three patients with locally advanced unresectable pancreatic adenocarcinoma received 25 Gy in a single fraction. Dose-volume histogram (DVH) endpoints evaluated include V{sub 5} (volume of duodenum that received 5 Gy), V{sub 10}, V{sub 15}, V{sub 20}, V{sub 25}, and D{sub max} (maximum dose to 1 cm{sup 3}). Normal tissue complication probability (NTCP) was evaluated with a Lyman model. Univariate and multivariate analyses were conducted with Kaplan-Meier and Cox regression models. Results: The median time to Grade 2-4 duodenal toxicity was 6.3 months (range, 1.6-11.8 months). The 6- and 12-month actuarial rates of toxicity were 11% and 29%, respectively. V{sub 10}-V{sub 25} and D{sub max} all correlated significantly with duodenal toxicity (p < 0.05). In particular, V{sub 15} {>=} 9.1 cm{sup 3} and V{sub 15} < 9.1 cm{sup 3} yielded duodenal toxicity rates of 52% and 11%, respectively (p = 0.002); V{sub 20} {>=} 3.3 cm{sup 3} and V{sub 20} < 3.3 cm{sup 3} gave toxicity rates of 52% and 11%, respectively (p = 0.002); and D{sub max} {>=} 23 Gy and D{sub max} < 23 Gy gave toxicity rates of 49% and 12%, respectively (p = 0.004). Lyman NTCP model optimization generated the coefficients m = 0.23, n = 0.12, and TD{sub 50} = 24.6 Gy. Only the Lyman NTCP model remained significant in multivariate analysis (p = 0.001). Conclusions: Multiple DVH endpoints and a Lyman NTCP model are strongly predictive of duodenal toxicity after SBRT for pancreatic cancer. These dose constraints will be valuable in future abdominal SBRT studies.

  2. Commissioning and dosimetric characteristics of TrueBeam system: Composite data of three TrueBeam machines

    SciTech Connect

    Chang Zheng; Wu Qiuwen; Adamson, Justus; Ren Lei; Bowsher, James; Yan Hui; Thomas, Andrew; Yin Fangfang

    2012-11-15

    Purpose: A TrueBeam linear accelerator (TB-LINAC) is designed to deliver traditionally flattened and flattening-filter-free (FFF) beams. Although it has been widely adopted in many clinics for patient treatment, limited information is available related to commissioning of this type of machine. In this work, commissioning data of three units were measured, and multiunit comparison was presented to provide valuable insights and reliable evaluations on the characteristics of the new treatment system. Methods: The TB-LINAC is equipped with newly designed waveguide, carousel assembly, monitoring control, and integrated imaging systems. Each machine in this study has 4, 6, 8, 10, 15 MV flattened photon beams, and 6 MV and 10 MV FFF photon beams as well as 6, 9, 12, 16, 20, and 22 MeV electron beams. Dosimetric characteristics of the three new TB-LINAC treatment units are systematically measured for commissioning. High-resolution diode detectors and ion chambers were used to measure dosimetric data for a range of field sizes from 10 Multiplication-Sign 10 to 400 Multiplication-Sign 400 mm{sup 2}. The composite dosimetric data of the three units are presented in this work. The commissioning of intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), image-guided radiation therapy, and gating systems are also illustrated. Critical considerations of P{sub ion} of FFF photon beams and small field dosimetric measurements were investigated. Results: The authors found all PDDs and profiles matched well among the three machines. Beam data were quantitatively compared and combined through average to yield composite beam data. The discrepancies among the machines were quantified using standard deviation (SD). The mean SD of the PDDs among the three units is 0.12%, and the mean SD of the profiles is 0.40% for 10 MV FFF open fields. The variations of P{sub ion} of the chamber CC13 is 1.2 {+-} 0.1% under 6 MV FFF and 2.0 {+-} 0.5% under 10 MV FFF from dmax to

  3. Characterization and use of a 2D-array of ion chambers for brachytherapy dosimetric quality assurance

    SciTech Connect

    Yewondwossen, Mammo

    2012-10-01

    The two-dimensional (2D) ionization chamber array MatriXX Evolution is one of the 2D ionization chamber arrays developed by IBA Dosimetry (IBA Dosimetry, Germany) for megavoltage real-time absolute 2D dosimetry and verification of intensity-modulated radiation therapy (IMRT). The purpose of this study was to (1) evaluate the performance of ion chamber array for submegavoltage range brachytherapy beam dose verification and quality assurance (QA) and (2) use the end-to-end dosimetric evaluation that mimics a patient treatment procedure and confirm the primary source strength calibration agrees in both the treatment planning system (TPS) and treatment delivery console computers. The dose linearity and energy dependence of the 2D ion chamber array was studied using kilovoltage X-ray beams (100, 180 and 300 kVp). The detector calibration factor was determined using 300 kVp X-ray beams so that we can use the same calibration factor for dosimetric verification of high-dose-rate (HDR) brachytherapy. The phantom used for this measurement consists of multiple catheters, the IBA MatriXX detector, and water-equivalent slab of RW3 to provide full scattering conditions. The treatment planning system (TPS) (Oncentra brachy version 3.3, Nucletron BV, Veenendaal, the Netherlands) dose distribution was calculated on the computed tomography (CT) scan of this phantom. The measured and TPS calculated distributions were compared in IBA Dosimetry OmniPro-I'mRT software. The quality of agreement was quantified by the gamma ({gamma}) index (with 3% delta dose and distance criterion of 2 mm) for 9 sets of plans. Using a dedicated phantom capable of receiving 5 brachytherapy intralumenal catheters a QA procedure was developed for end-to-end dosimetric evaluation for routine QA checks. The 2D ion chamber array dose dependence was found to be linear for 100-300 kVp and the detector response (k{sub user}) showed strong energy dependence for 100-300 kVp energy range. For the Ir-192 brachytherapy

  4. Geologic map of Mars

    USGS Publications Warehouse

    Tanaka, Kenneth L.; Skinner, James A.; Dohm, James M.; Irwin, Rossman P., III; Kolb, Eric J.; Fortezzo, Corey M.; Platz, Thomas; Michael, Gregory G.; Hare, Trent M.

    2014-01-01

    This global geologic map of Mars, which records the distribution of geologic units and landforms on the planet's surface through time, is based on unprecedented variety, quality, and quantity of remotely sensed data acquired since the Viking Orbiters. These data have provided morphologic, topographic, spectral, thermophysical, radar sounding, and other observations for integration, analysis, and interpretation in support of geologic mapping. In particular, the precise topographic mapping now available has enabled consistent morphologic portrayal of the surface for global mapping (whereas previously used visual-range image bases were less effective, because they combined morphologic and albedo information and, locally, atmospheric haze). Also, thermal infrared image bases used for this map tended to be less affected by atmospheric haze and thus are reliable for analysis of surface morphology and texture at even higher resolution than the topographic products.

  5. Iconicity as structure mapping

    PubMed Central

    Emmorey, Karen

    2014-01-01

    Linguistic and psycholinguistic evidence is presented to support the use of structure-mapping theory as a framework for understanding effects of iconicity on sign language grammar and processing. The existence of structured mappings between phonological form and semantic mental representations has been shown to explain the nature of metaphor and pronominal anaphora in sign languages. With respect to processing, it is argued that psycholinguistic effects of iconicity may only be observed when the task specifically taps into such structured mappings. In addition, language acquisition effects may only be observed when the relevant cognitive abilities are in place (e.g. the ability to make structural comparisons) and when the relevant conceptual knowledge has been acquired (i.e. information key to processing the iconic mapping). Finally, it is suggested that iconicity is better understood as a structured mapping between two mental representations than as a link between linguistic form and human experience. PMID:25092669

  6. Iconicity as structure mapping.

    PubMed

    Emmorey, Karen

    2014-09-19

    Linguistic and psycholinguistic evidence is presented to support the use of structure-mapping theory as a framework for understanding effects of iconicity on sign language grammar and processing. The existence of structured mappings between phonological form and semantic mental representations has been shown to explain the nature of metaphor and pronominal anaphora in sign languages. With respect to processing, it is argued that psycholinguistic effects of iconicity may only be observed when the task specifically taps into such structured mappings. In addition, language acquisition effects may only be observed when the relevant cognitive abilities are in place (e.g. the ability to make structural comparisons) and when the relevant conceptual knowledge has been acquired (i.e. information key to processing the iconic mapping). Finally, it is suggested that iconicity is better understood as a structured mapping between two mental representations than as a link between linguistic form and human experience. PMID:25092669

  7. Bodily maps of emotions

    PubMed Central

    Nummenmaa, Lauri; Glerean, Enrico; Hari, Riitta; Hietanen, Jari K.

    2014-01-01

    Emotions are often felt in the body, and somatosensory feedback has been proposed to trigger conscious emotional experiences. Here we reveal maps of bodily sensations associated with different emotions using a unique topographical self-report method. In five experiments, participants (n = 701) were shown two silhouettes of bodies alongside emotional words, stories, movies, or facial expressions. They were asked to color the bodily regions whose activity they felt increasing or decreasing while viewing each stimulus. Different emotions were consistently associated with statistically separable bodily sensation maps across experiments. These maps were concordant across West European and East Asian samples. Statistical classifiers distinguished emotion-specific activation maps accurately, confirming independence of topographies across emotions. We propose that emotions are represented in the somatosensory system as culturally universal categorical somatotopic maps. Perception of these emotion-triggered bodily changes may play a key role in generating consciously felt emotions. PMID:24379370

  8. SU-E-J-72: Dosimetric Study of Cone-Beam CT-Based Radiation Treatment Planning Using a Patient-Specific Stepwise CT-Density Table

    SciTech Connect

    Chen, S; Le, Q; Mutaf, Y; Yi, B; D’Souza, W

    2015-06-15

    Purpose: To assess dose calculation accuracy of cone-beam CT (CBCT) based treatment plans using a patient-specific stepwise CT-density conversion table in comparison to conventional CT-based treatment plans. Methods: Unlike CT-based treatment planning which use fixed CT-density table, this study used patient-specific CT-density table to minimize the errors in reconstructed mass densities due to the effects of CBCT Hounsfield unit (HU) uncertainties. The patient-specific CT-density table was a stepwise function which maps HUs to only 6 classes of materials with different mass densities: air (0.00121g/cm3), lung (0.26g/cm3), adipose (0.95g/cm3), tissue (1.05 g/cm3), cartilage/bone (1.6g/cm3), and other (3g/cm3). HU thresholds to define different materials were adjusted for each CBCT via best match with the known tissue types in these images. Dose distributions were compared between CT-based plans and CBCT-based plans (IMRT/VMAT) for four types of treatment sites: head and neck (HN), lung, pancreas, and pelvis. For dosimetric comparison, PTV mean dose in both plans were compared. A gamma analysis was also performed to directly compare dosimetry in the two plans. Results: Compared to CT-based plans, the differences for PTV mean dose were 0.1% for pelvis, 1.1% for pancreas, 1.8% for lung, and −2.5% for HN in CBCT-based plans. The gamma passing rate was 99.8% for pelvis, 99.6% for pancreas, and 99.3% for lung with 3%/3mm criteria, and 80.5% for head and neck with 5%/3mm criteria. Different dosimetry accuracy level was observed: 1% for pelvis, 3% for lung and pancreas, and 5% for head and neck. Conclusion: By converting CBCT data to 6 classes of materials for dose calculation, 3% of dose calculation accuracy can be achieved for anatomical sites studied here, except HN which had a 5% accuracy. CBCT-based treatment planning using a patient-specific stepwise CT-density table can facilitate the evaluation of dosimetry changes resulting from variation in patient anatomy.

  9. A Course To Understand Maps.

    ERIC Educational Resources Information Center

    Winter, E. A.

    Secondary students in Tasmania, Australia, can develop their skills in social studies and geography by solving the problems involving map use that this resource book provides. Several different types of maps are covered including: building plans, sketch maps, contours maps, world-grids, atlases, and urban maps. (DB)

  10. Mental Mapping: A Classroom Strategy

    ERIC Educational Resources Information Center

    Solomon, Les

    1978-01-01

    Examines potential uses of mental maps in the classroom by reviewing research efforts, providing an example of the differences between mental maps of two student groups, and suggesting how to use mental maps in the geography curriculum. Mental mapping (or cognitive mapping) refers to individuals' processes of collecting, storing, and retrieving…

  11. Getting Results with Curriculum Mapping

    ERIC Educational Resources Information Center

    Jacobs, Heidi Hayes

    2004-01-01

    This helpful resource will speed the mapping effort along and apply curriculum mapping to special situations. In this book teachers and administrators offer concrete advice on how to get the most out of curriculum mapping in districts and schools: (1) Steps to implementing mapping procedures and leading the mapping process; (2) Tools and resources…

  12. Development of radiochromic film for spatially quantitative dosimetric analysis of indirect ionizing radiation fields

    NASA Astrophysics Data System (ADS)

    Brady, Samuel Loren

    sensors measured < 2% and < 7% deviation in pixel light intensities for 50 consecutive scans, respectively. Both scanner light sources were shown to be uniform in transmission and reflection scan modes along the center axis of light source translation. Additionally, RCFs demonstrated a larger dynamic range in pixel light intensities, and to be less sensitive to off axis light inhomogeneity, when scanned in landscape mode (long axis of film parallel with axis of light source translation). The EPSON 10000XL demonstrated slightly better light source/CCD temporal stability and provided a capacity to scan larger film formats at the center of the scanner in landscape mode. However, the EPSON V700 only measured an overall difference in accuracy and precision by 2%, and though smaller in size, at the time of this work, was one sixth the cost of the 10000XL. A scan protocol was developed to maximize RCF digitization accuracy and precision, and a calibration fitting function was developed for RCF absolute dosimetry. The fitting function demonstrated a superior goodness of fit for both RCF types over a large range of absorbed dose levels as compared to the currently accepted function found in literature. The RCF dosimetry system was applied to three novel areas from which a benefit could be derived for 2D or 3D dosimetric information. The first area was for a 3D dosimetry of a pendant breast in 3D-CT mammography. The novel method of developing a volumetric image of the breast from a CT acquisition technique was empirically measured for its dosimetry and compared to standard dual field digital mammography. The second area was dose reduction in CT for pediatric and adult scan protocols. In this application, novel methodologies were developed to measure 3D organ dosimetry and characterize a dose reduction scan protocol for pediatric and adult body habitus. The third area was in the field of small animal irradiation for radiobiology purposes and cancer patient treatment verification. In

  13. Analyzing thematic maps and mapping for accuracy

    USGS Publications Warehouse

    Rosenfield, G.H.

    1982-01-01

    Two problems which exist while attempting to test the accuracy of thematic maps and mapping are: (1) evaluating the accuracy of thematic content, and (2) evaluating the effects of the variables on thematic mapping. Statistical analysis techniques are applicable to both these problems and include techniques for sampling the data and determining their accuracy. In addition, techniques for hypothesis testing, or inferential statistics, are used when comparing the effects of variables. A comprehensive and valid accuracy test of a classification project, such as thematic mapping from remotely sensed data, includes the following components of statistical analysis: (1) sample design, including the sample distribution, sample size, size of the sample unit, and sampling procedure; and (2) accuracy estimation, including estimation of the variance and confidence limits. Careful consideration must be given to the minimum sample size necessary to validate the accuracy of a given. classification category. The results of an accuracy test are presented in a contingency table sometimes called a classification error matrix. Usually the rows represent the interpretation, and the columns represent the verification. The diagonal elements represent the correct classifications. The remaining elements of the rows represent errors by commission, and the remaining elements of the columns represent the errors of omission. For tests of hypothesis that compare variables, the general practice has been to use only the diagonal elements from several related classification error matrices. These data are arranged in the form of another contingency table. The columns of the table represent the different variables being compared, such as different scales of mapping. The rows represent the blocking characteristics, such as the various categories of classification. The values in the cells of the tables might be the counts of correct classification or the binomial proportions of these counts divided by

  14. SU-E-J-66: Significant Anatomical and Dosimetric Changes Observed with the Pharyngeal Constrictor During Head and Neck Radiotherapy Elicited From Daily Deformable Image Registration and Dose Accumulation

    SciTech Connect

    Kumarasiri, A; Siddiqui, F; Liu, C; Kamal, M; Fraser, C; Chetty, I; Kim, J

    2015-06-15

    Purpose: To evaluate the anatomical changes and associated dosimetric consequences to the pharyngeal constrictor (PC) that occurs during head and neck radiotherapy (H&N RT). Methods: A cohort of 13 oro-pharyngeal cancer patients, who had daily CBCT’s for localization, was retrospectively studied. On every 5th CBCT, PC was manually delineated by a radiation oncologist. The anterior-posterior PC thickness was measured at the C3 level. Delivered dose to PC was estimated by calculating daily doses on CBCT’s, and accumulating to corresponding planning CT images. For accumulation, a parameter-optimized B- spline-based deformable image registration algorithm (Elastix) was used, in conjunction with an energy-mass mapping dose transfer algorithm. Mean and maximum dose (Dmean, Dmax) to PC was determined and compared with corresponding planned quantities. Results: The mean (±standard deviation) volume increase (ΔV) and thickness increase (Δt) over the course of 35 total fractions were 54±33% (11.9±7.6 cc), and 63±39% (2.9±1.9 mm), respectively. The resultant cumulative mean dose increase from planned dose to PC (ΔDmean) was 1.4±1.3% (0.9±0.8 Gy), while the maximum dose increase (ΔDmax) was 0.0±1.6% (0.0±1.1 Gy). Patients with adaptive replanning (n=6) showed a smaller mean dose increase than those without (n=7); 0.5±0.2% (0.3±0.1 Gy) vs. 2.2±1.4% (1.4±0.9 Gy). There was a statistically significant (p<0.0001) strong correlation between ΔDmean and Δt (Pearson coefficient r=0.78), and a moderate-to-strong correlation (r=0.52) between ΔDmean and ΔV. Correlation between ΔDmean and weight loss ΔW (r=0.1), as well as ΔV and ΔW (r=0.2) were negligible. Conclusion: Patients were found to undergo considerable anatomical changes to pharyngeal constrictor during H&N RT, resulting in non-negligible dose deviations from intended dose. Results are indicative that pharyngeal constrictor thickness, measured at C3 level, is a good predictor for the dose change to

  15. Noise Mapping and Annoyance.

    PubMed

    Knauss, D.

    2002-01-01

    The EC has published a Green Paper on noise policy in the EU and has issued a directive on the assessment and reduction of environmental noise. This directive will make noise mapping mandatory for cities with at least 250.000 inhabitants. Due to the development in computer technology it is possible to calculate noise maps for large urban areas using the available data on buildings, ground profile, road and rail traffic. Examples for noise mapping are Birmingham (GB), Linz (A) and various German cities. Based on noise maps and empirical data on the correlation between annoyance and noise levels annoyance maps for different sources (rail, road, aircraft) can be calculated. Under the assumption that the annoyance for the different sources are only weakly correlated, a combined annoyance map can be calculated. In a second step using the distribution of the population the actual number of annoyed people can be evaluated. This analysis can be used, for example, to identify noise hot spots and to assess the impact of major traffic projects - roads, airports- on the noise situation as well as the impact on the population. Furthermore, the combined annoyance maps can be used to investigate on health effects and to check whether or not empirical correlations between annoyance and noise levels are sufficiently correct. PMID:12678944

  16. Color on emergency mapping

    NASA Astrophysics Data System (ADS)

    Jiang, Lili; Qi, Qingwen; Zhang, An

    2007-06-01

    There are so many emergency issues in our daily life. Such as typhoons, tsunamis, earthquake, fires, floods, epidemics, etc. These emergencies made people lose their lives and their belongings. Every day, every hour, even every minute people probably face the emergency, so how to handle it and how to decrease its hurt are the matters people care most. If we can map it exactly before or after the emergencies; it will be helpful to the emergency researchers and people who live in the emergency place. So , through the emergency map, before emergency is occurring we can predict the situation, such as when and where the emergency will be happen; where people can refuge, etc. After disaster, we can also easily assess the lost, discuss the cause and make the lost less. The primary effect of mapping is offering information to the people who care about the emergency and the researcher who want to study it. Mapping allows the viewers to get a spatial sense of hazard. It can also provide the clues to study the relationship of the phenomenon in emergency. Color, as the basic element of the map, it can simplify and clarify the phenomenon. Color can also affects the general perceptibility of the map, and elicits subjective reactions to the map. It is to say, structure, readability, and the reader's psychological reactions can be affected by the use of color.

  17. Coastal mapping handbook

    USGS Publications Warehouse

    U.S. Geological Survey; National Oceanic and Atmospheric Administration; Ellis, Melvin Y., (Edited By)

    1978-01-01

    Passage of the Coastal Zone Management Act of 1972 focused attention on the Nation's coastal land and water areas. As plans for more effective management of the coastal zone evolved, it soon became apparent that improved maps and charts of these areas were needed. This handbook was prepared with the requirements of the entire coastal community in mind, giving greatest attention to the needs of coastal zone managers and planners at the State and local levels. Its principal objective is to provide general information and guidance; it is neither a textbook nor a technical manual, but rather a primer on coastal mapping. This handbook should help planners and managers of coastal programs to determine their mapping requirements, select the best maps and charts for their particular needs, and to deal effectively with personnel who gather data and prepare maps. The sections on "Sources of Assistance and Advice" and "Product and Data Sources" should be especially useful to all involved in mapping the coastal zone. Brief summaries of the mapping efforts of several State coastal zone management programs are included. "Future outlook" discusses anticipated progress and changes in mapping procedures and techniques. Illustrations are inserted, where appropriate, to illustrate the products and equipment discussed. Because of printing restrictions, the colors in map illustrations may vary from those in the original publication. The appendixes include substantial material which also should be of interest. In addition a glossary and an index are included to provide easy and quick access to the terms and concepts used in the text. For those interested in more technical detail than is provided in this handbook, the "Selected references" will be useful. Also, the publications of the professional societies listed in appendix 4 will provide technical information in detail.

  18. Mapping luna incognita

    NASA Astrophysics Data System (ADS)

    Westfall, John E.

    1990-11-01

    The portion of the moon near the south and southwestern limbs was poorly photographed by the 1960s lunar missions, and is accordingly designated 'luna incognita'. The Association of Lunar and Planetary Observers accordingly undertook a study of this region from 1972 to 1990 which ultimately encompassed 1509 photographs by terrestrial observers, photographs from the Lunar Orbiters IV and V and from Zond 8, radar maps and images, and charts of the moon's limb profile. On these bases, a shaded-relief topographic map was compiled and executed by a computerized 'shading' program at 1:2.5 million scale. This map is presently reproduced in 1:3.5 million scale.

  19. Automatic cloud cover mapping.

    NASA Technical Reports Server (NTRS)

    Strong, J. P., III; Rosenfeld, A.

    1971-01-01

    A method of converting a picture into a 'cartoon' or 'map' whose regions correspond to differently textured regions is described. Texture edges in the picture are detected, and solid regions surrounded by these (usually broken) edges are 'colored in' using a propagation process. The resulting map is cleaned by comparing the region colors with the textures of the corresponding regions in the picture, and also by merging some regions with others according to criteria based on topology and size. The method has been applied to the construction of cloud cover maps from cloud cover pictures obtained by satellites.

  20. Generalized qudit Choi maps

    SciTech Connect

    Jafarizadeh, M. A.; Rezaee, M.; Ahadpour, S.

    2006-10-15

    Following the linear programming prescription of Jafarizadeh et al. [Phys. Rev. A 72, 062106 (2005)], the d(multiply-in-circle sign)d Bell diagonal entanglement witnesses are provided. By using Jamiolkowski isomorphism, it is shown that the corresponding positive maps are the generalized qudit Choi maps. Also by manipulating particular d(multiply-in-circle sign)d Bell diagonal separable states and constructing corresponding bound entangled states, it is shown that the obtained d(multiply-in-circle sign)d Bell states diagonal entanglement witnesses (consequently qudit Choi maps) are nondecomposable in a certain range of their parameters.

  1. Mapping the Baby Universe

    NASA Technical Reports Server (NTRS)

    Wanjek, Christopher

    2003-01-01

    In June, NASA plans to launch the Microwave Anisotropy Probe (MAP) to survey the ancient radiation in unprecedented detail. MAP will map slight temperature fluctuations within the microwave background that vary by only 0.00001 C across a chilly radiation that now averages 2.73 C above absolute zero. The temperature differences today point back to density differences in the fiery baby universe, in which there was a little more matter here and a little less matter there. Areas of slightly enhanced density had stronger gravity than low-density areas. The high-density areas pulled back on the background radiation, making it appear slightly cooler in those directions.

  2. Evaluation of Dosimetric Parameters and Disease Response After {sup 125}Iodine Transperineal Brachytherapy for Low- and Intermediate-Risk Prostate Cancer

    SciTech Connect

    Morris, W. James Keyes, Mira M.D.; Palma, David M.D.; McKenzie, Michael; Spadinger, Ingrid; Agranovich, Alex; Pickles, Tom; Liu, Mitchell; Kwan, Winkle; Wu, Jonn; Lapointe, Vince; Berthelet, Eric; Pai, Howard; Harrison, Robert; Kwa, William; Bucci, Joe; Racz, Violet; Woods, Ryan

    2009-04-01

    Purpose: To analyze dosimetric outcomes after permanent brachytherapy for men with low-risk and 'low-tier' intermediate-risk prostate cancer and explore the relationship between the traditional dosimetric values, V100 (volume of prostate receiving 100% of the prescribed dose) and D90 (minimum dose to 90% of the prostate), and risk of biochemical failure. Methods and Materials: A total of 1,006 consecutive patients underwent implantation between July 20, 1998, and Oct 23, 2003. Most (58%) had low-risk disease; the remaining 42% comprised a selected low-tier subgroup of intermediate-risk patients. The prescribed minimum peripheral dose (MPD) was 144 Gy. All implants used 0.33 mCi {sup 125}I sources using a preplan technique featuring right-left symmetry and a strong posterior-peripheral dose bias. Sixty-five percent of patients had 6 months of androgen deprivation therapy. Postimplantation dosimetry was calculated using day-28 CT scans. Results: With a median follow-up of 54 months, the actuarial 5-year rate of freedom from biochemical recurrence (bNED) was 95.6% {+-} 1.6%. Median D90 was 105% of MPD, median V100 was 92%, median V150 was 58%, and median V200 was 9%. Dosimetric values were not predictive of biochemical recurrence on univariate or multivariate analysis. Analysis of dosimetric values by implantation number showed statistically significant increases in all values with time (D90, V100, V150, and V200; p < 0.001), but this did not translate into improved bNED. Conclusions: In contrast to some previous studies, dosimetric outcomes did not correlate with biochemical recurrence in the first 1,006 patients treated with {sup 125}I prostate brachytherapy at the British Columbia Cancer Agency. Despite a median D90 of only 105% of MPD, our bNED rates are indistinguishable from series that reported higher D90 values.

  3. SWIMRT: a graphical user interface using sliding window algorithm to construct a fluence map machine file.

    PubMed

    Chow, James C L; Grigorov, Grigor N; Yazdani, Nuri

    2006-01-01

    A custom-made computer program, SWIMRT, to construct "multileaf collimator (MLC) machine" file for intensity-modulated radiotherapy (IMRT) fluence maps was developed using MATLAB and the sliding window algorithm. The user can either import a fluence map with a graphical file format created by an external treatment-planning system such as Pinnacle3 or create his or her own fluence map using the matrix editor in the program. Through comprehensive calibrations of the dose and the dimension of the imported fluence field, the user can use associated image-processing tools such as field resizing and edge trimming to modify the imported map. When the processed fluence map is suitable, a "MLC machine" file is generated for our Varian 21 EX linear accelerator with a 120-leaf Millennium MLC. This machine file is transferred to the MLC console of the LINAC to control the continuous motions of the leaves during beam irradiation. An IMRT field is then irradiated with the 2D intensity profiles, and the irradiated profiles are compared to the imported or modified fluence map. This program was verified and tested using film dosimetry to address the following uncertainties: (1) the mechanical limitation due to the leaf width and maximum traveling speed, and (2) the dosimetric limitation due to the leaf leakage/transmission and penumbra effect. Because the fluence map can be edited, resized, and processed according to the requirement of a study, SWIMRT is essential in studying and investigating the IMRT technique using the sliding window algorithm. Using this program, future work on the algorithm may include redistributing the time space between segmental fields to enhance the fluence resolution, and readjusting the timing of each leaf during delivery to avoid small fields. Possible clinical utilities and examples for SWIMRT are given in this paper. PMID:17533330

  4. Verification of dosimetric accuracy on the TrueBeam STx: Rounded leaf effect of the high definition MLC

    SciTech Connect

    Kielar, Kayla N.; Mok, Ed; Hsu, Annie; Wang Lei; Luxton, Gary

    2012-10-15

    Purpose: The dosimetric leaf gap (DLG) in the Varian Eclipse treatment planning system is determined during commissioning and is used to model the effect of the rounded leaf-end of the multileaf collimator (MLC). This parameter attempts to model the physical difference between the radiation and light field and account for inherent leakage between leaf tips. With the increased use of single fraction high dose treatments requiring larger monitor units comes an enhanced concern in the accuracy of leakage calculations, as it accounts for much of the patient dose. This study serves to verify the dosimetric accuracy of the algorithm used to model the rounded leaf effect for the TrueBeam STx, and describes a methodology for determining best-practice parameter values, given the novel capabilities of the linear accelerator such as flattening filter free (FFF) treatments and a high definition MLC (HDMLC). Methods: During commissioning, the nominal MLC position was verified and the DLG parameter was determined using MLC-defined field sizes and moving gap tests, as is common in clinical testing. Treatment plans were created, and the DLG was optimized to achieve less than 1% difference between measured and calculated dose. The DLG value found was tested on treatment plans for all energies (6 MV, 10 MV, 15 MV, 6 MV FFF, 10 MV FFF) and modalities (3D conventional, IMRT, conformal arc, VMAT) available on the TrueBeam STx. Results: The DLG parameter found during the initial MLC testing did not match the leaf gap modeling parameter that provided the most accurate dose delivery in clinical treatment plans. Using the physical leaf gap size as the DLG for the HDMLC can lead to 5% differences in measured and calculated doses. Conclusions: Separate optimization of the DLG parameter using end-to-end tests must be performed to ensure dosimetric accuracy in the modeling of the rounded leaf ends for the Eclipse treatment planning system. The difference in leaf gap modeling versus physical

  5. SU-E-J-39: Dosimetric Benefit of Implanted Marker-Based CBCT Setup for Definitive Prostatic Radiotherapy

    SciTech Connect

    Zhen, H; Wu, Z; Bluemenfeld, P; Chu, J; Wang, D

    2015-06-15

    Purpose Daily setup for definitive prostatic radiotherapy is challenged by suboptimal visibility of the prostate boundary and daily variation of rectum shape and position. For patients with improved bowel preparation, we conducted a dosimetric comparison between prostate implanted marker (IM)-based daily setup and anterior rectal wall (ARW)-based setup, with the hypothesis that the former leads to adequate target coverage with better rectal sparing. Methods Five IMRT/VMAT prostate cases with implanted markers were selected for analysis. Daily CBCT showed improvement of the rectal volume compared to planning CT. For each patient, the prostate and rectum were contoured on three CBCT images (fraction 5/15/25) with subsequent physician review. The CBCTs were then registered to a planning CT using IM-based registration. The deviation of ARW positions from planning CT to CBCT were analyzed at various sup-inf levels (−1.8 cm to 1.8 cm from level of prostate center). To estimate the potential dosimetric impact from ARW-based setup, the treatment plans were recalculated using A-P shifts ranging from −1mm to +6mm. Clinically important rectum DVH values including Dmax, D3cc and Dmean were computed. Results For the studied patients, we observed on average 32% rectum volume reduction from planning CT to CBCT. As a Results, the ARW on average shifts posteriorly by −1mm to +5mm, depending on the sup-inf level of observation, with larger shifts observed at more superior levels. Recalculation shows that when ARW shifts 1mm posteriorly, ARW-based CBCT setup leads to a 1.0%, 4.2%, and 3.2% increase in rectum Dmax, D3cc, and Dmean, respectively, compared to IM-based setup. The dosimetric deviations increase to 4.7%, 25.8% and 24.7% when ARW shifts 6mm posteriorly. No significant prostate-only dose difference was observed. Conclusion For patients with improved bowel preparation, IM-based CBCT setup leads to accurate prostate coverage along with significantly lower rectal dose

  6. Dosimetric comparison of treatment plans based on free breathing, maximum, and average intensity projection CTs for lung cancer SBRT

    SciTech Connect

    Tian Yuan; Wang Zhiheng; Ge Hong; Zhang Tian; Cai Jing; Kelsey, Christopher; Yoo, David; Yin Fangfang

    2012-05-15

    Purpose: To determine whether there is a CT dataset may be more favorable for planning and dose calculation by comparing dosimetric characteristics between treatment plans calculated using free breathing (FB), maximum and average intensity projection (MIP and AIP, respectively) CTs for lung cancer patients receiving stereotactic body radiation therapy (SBRT). Methods: Twenty lung cancer SBRT patients, treated on a linac with 2.5 mm width multileaf-collimator (MLC), were analyzed retrospectively. Both FB helical and four-dimensional CT scans were acquired for each patient. Internal target volume (ITV) was delineated based on MIP CTs and modified based on both ten-phase datasets and FB CTs. Planning target volume (PTV) was then determined by adding additional setup margin to ITV. The PTVs and beams in the optimized treatment plan based on FB CTs were copied to MIP and AIP CTs, with the same isocenters, MLC patterns and monitor units. Mean effective depth (MED) of beams, and some dosimetric parameters for both PTVs and most important organ at risk (OAR), lung minus PTV, were compared between any two datasets using two-tail paired t test. Results: The MEDs in FB and AIP plans were similar but significantly smaller (Ps < 0.001) than that in MIP plans. Minimum dose, mean dose, dose covering at least 90% and 95% of PTVs in MIP plans were slightly higher than two other plans (Ps < 0.008). The absolute volume of lung minus PTV receiving greater than 5, 10, and 20 Gy in MIP plans were significantly smaller than those in both FB and AIP plans (Ps < 0.008). Conformity index for FB plans showed a small but statistically significantly higher. Conclusions: Dosimetric characteristics of AIP plans are similar to those of FB plans. Slightly better target volume coverage and significantly lower low-dose region ({<=}30 Gy) in lung was observed in MIP plans. The decrease in low-dose region in lung was mainly caused by the change of lung volume contoured on two datasets rather than the

  7. Dosimetric comparison of 3D conformal, IMRT, and V-MAT techniques for accelerated partial-breast irradiation (APBI).

    PubMed

    Qiu, Jian-Jian; Chang, Zheng; Horton, Janet K; Wu, Qing-Rong Jackie; Yoo, Sua; Yin, Fang-Fang

    2014-01-01

    The purpose is to dosimetrically compare the following 3 delivery techniques: 3-dimensional conformal radiation therapy (3D-CRT), intensity-modulated arc therapy (IMRT), and volumetric-modulated arc therapy (V-MAT) in the treatment of accelerated partial-breast irradiation (APBI). Overall, 16 patients with T1/2N0 breast cancer were treated with 3D-CRT (multiple, noncoplanar photon fields) on the RTOG 0413 partial-breast trial. These cases were subsequently replanned using static gantry IMRT and V-MAT technology to understand dosimetric differences among these 3 techniques. Several dosimetric parameters were used in plan quality evaluation, including dose conformity index (CI) and dose-volume histogram analysis of normal tissue coverage. Quality assurance studies including gamma analysis were performed to compare the measured and calculated dose distributions. The IMRT and V-MAT plans gave more conformal target dose distributions than the 3D-CRT plans (p < 0.05 in CI). The volume of ipsilateral breast receiving 5 and 10Gy was significantly less using the V-MAT technique than with either 3D-CRT or IMRT (p < 0.05). The maximum lung dose and the ipsilateral lung volume receiving 10 (V10) or 20Gy (V20) were significantly less with both V-MAT and IMRT (p < 0.05). The IMRT technique was superior to 3D-CRT and V-MAT of low dose distributions in ipsilateral lung (p < 0.05 in V5 and D5). The total mean monitor units (MUs) for V-MAT (621.0 ± 111.9) were 12.2% less than those for 3D-CRT (707.3 ± 130.9) and 46.5% less than those for IMRT (1161.4 ± 315.6) (p < 0.05). The average machine delivery time was 1.5 ± 0.2 minutes for the V-MAT plans, 7.0 ± 1.6 minutes for the 3D-CRT plans, and 11.5 ± 1.9 minutes for the IMRT plans, demonstrating much less delivery time for V-MAT. Based on this preliminary study, V-MAT and IMRT techniques offer improved dose conformity as compared with 3D-CRT techniques without increasing dose to the ipsilateral lung. In terms of MU and delivery

  8. Dosimetric variation due to the photon beam energy in the small-animal irradiation: A Monte Carlo study

    SciTech Connect

    Chow, James C. L.; Leung, Michael K. K.; Lindsay, Patricia E.; Jaffray, David A.

    2010-10-15

    Purpose: The impact of photon beam energy and tissue heterogeneities on dose distributions and dosimetric characteristics such as point dose, mean dose, and maximum dose was investigated in the context of small-animal irradiation using Monte Carlo simulations based on the EGSnrc code. Methods: Three Monte Carlo mouse phantoms, namely, heterogeneous, homogeneous, and bone homogeneous were generated based on the same mouse computed tomography image set. These phantoms were generated by overriding the tissue type of none of the voxels (heterogeneous), all voxels (homogeneous), and only the bone voxels (bone homogeneous) to that of soft tissue. Phase space files of the 100 and 225 kVp photon beams based on a small-animal irradiator (XRad225Cx, Precision X-Ray Inc., North Branford, CT) were generated using BEAMnrc. A 360 deg. photon arc was simulated and three-dimensional (3D) dose calculations were carried out using the DOSXYZnrc code through DOSCTP in the above three phantoms. For comparison, the 3D dose distributions, dose profiles, mean, maximum, and point doses at different locations such as the isocenter, lung, rib, and spine were determined in the three phantoms. Results: The dose gradient resulting from the 225 kVp arc was found to be steeper than for the 100 kVp arc. The mean dose was found to be 1.29 and 1.14 times higher for the heterogeneous phantom when compared to the mean dose in the homogeneous phantom using the 100 and 225 kVp photon arcs, respectively. The bone doses (rib and spine) in the heterogeneous mouse phantom were about five (100 kVp) and three (225 kVp) times higher when compared to the homogeneous phantom. However, the lung dose did not vary significantly between the heterogeneous, homogeneous, and bone homogeneous phantom for the 225 kVp compared to the 100 kVp photon beams. Conclusions: A significant bone dose enhancement was found when the 100 and 225 kVp photon beams were used in small-animal irradiation. This dosimetric effect, due to

  9. Dosimetric impact of source-positioning uncertainty in high-dose-rate balloon brachytherapy of breast cancer

    PubMed Central

    2015-01-01

    Purpose To evaluate the dosimetric impact of source-positioning uncertainty in high-dose-rate (HDR) balloon brachytherapy of breast cancer. Material and methods For 49 HDR balloon patients, each dwell position of catheter(s) was manually shifted distally (+) and proximally (–) with a magnitude from 1 to 4 mm. Total 392 plans were retrospectively generated and compared to corresponding clinical plans using 7 dosimetric parameters: dose (D95) to 95% of planning target volume for evaluation (PTV_EVAL), and volume covered by 100% and 90% of the prescribed dose (PD) (V100 and V90); skin and rib maximum point dose (Dmax); normal breast tissue volume receiving 150% and 200% of PD (V150 and V200). Results PTV_EVAL dosimetry deteriorated with larger average/maximum reduction (from ± 1 mm to ± 4 mm) for larger source position uncertainty (p value < 0.0001): from 1.0%/2.5%, 3.3%/5.9%, 6.3%/10.0% to 9.8%/14.5% for D95; from 1.0%/2.6%, 3.1%/5.7%, 5.8%/8.9% to 8.7%/12.3% for V100; from 0.2%/1.5%, 1.0%/4.0%, 2.7%/6.8% to 5.1%/10.3% for V90. ≥ ± 3 mm shift reduced average D95 to < 95% and average V100 to < 90%. While skin and rib Dmax change was case-specific, its absolute change (∣Δ(Value)∣) showed that larger shift and high dose group had larger variation compared to smaller and lower dose group (p value < 0.0001), respectively. Normal breast tissue V150 variation was case-specific and small. Average ∣Δ(V150)∣ was 0.2 cc for the largest shift (± 4 mm) with maximum < 1.7 cc. V200 was increased with higher elevation for larger shift: from 6.4 cc/9.8 cc, 7.0 cc/10.1 cc, 8.0 cc/11.3 cc to 9.2 cc/ 13.0 cc. Conclusions The tolerance of ± 2 mm recommended by AAPM TG 56 is clinically acceptable in most clinical cases. However, special attention should be paid to a case where both skin and rib are located proximally to balloon, and the orientation of balloon catheter(s) is vertical to these critical structures. In this case, sufficient dosimetric planning margins are

  10. SU-F-BRD-06: Dosimetric Cost of a GTV Margin for Simultaneous Integrated Intra- Prostatic Boost Treatments

    SciTech Connect

    Studenski, M; Abramowitz, M; Dogan, N; Pollack, A

    2014-06-15

    Purpose: Quantify the dosimetric cost for a margin around the MRI-defined high risk GTV for simultaneous integrated intra-prostatic boosts (SIIB) treated with RapidArc. Methods: For external beam radiotherapy of the prostate, a 3-7 mm PTV margin is typically used to account for setup and intra-fraction uncertainties after adjusting for inter-fraction motion. On the other hand, our current paradigm is to treat the MRI-defined high risk GTV with no margin. In this work, 11 patients treated SIIB (7 post-prostatectomy, 4 intact prostate) with RapidArc were re-planned with 1-5 mm margins around the GTV to quantify dosimetric effects. Two 358 degree, 10 MV RapidArcs were used to deliver 68 Gy (76.5 Gy boost) to the post-prostatectomy patients and 80 Gy (86 Gy boost) to the intact prostates. Paired, two tail t-tests were used to determine if there were any significant differences (p<0.05) in the total MUs and dosimetric parameters used to evaluate rectum, bladder, and PTV dose with and without margin. Results: The average GTV volume without margin was 8.1cc (2.8% of the PTV volume) while the average GTV volume with a 5 mm margin was 20.1cc (9.0% of the PTV volume). GTV volumes ranged from 0.2% of the PTV volume up to 33.0%. Despite these changes in volume, the only statistical difference was found for the rectal V65 Gy with a 5 mm margin (18.6% vs. 19.4%; p-value = 0.026) when all patients were considered as a single group. No difference was found when analyzed as two groups. The rectum V40Gy, bladder V40Gy and V65Gy, PTV Dmax and D95% or the total MUs did not show any significant difference for any margin. Conclusion: A 4 mm margin on the high risk GTV is possible with no statistically significant change in dosimetry or total MUs. Further work will assess the appropriate margin required for intra-prostatic boosts.

  11. Dosimetric comparison of 3D conformal, IMRT, and V-MAT techniques for accelerated partial-breast irradiation (APBI)

    SciTech Connect

    Qiu, Jian-Jian; Chang, Zheng; Horton, Janet K.; Wu, Qing-Rong Jackie; Yoo, Sua; Yin, Fang-Fang

    2014-07-01

    The purpose is to dosimetrically compare the following 3 delivery techniques: 3-dimensional conformal radiation therapy (3D-CRT), intensity-modulated arc therapy (IMRT), and volumetric-modulated arc therapy (V-MAT) in the treatment of accelerated partial-breast irradiation (APBI). Overall, 16 patients with T1/2N0 breast cancer were treated with 3D-CRT (multiple, noncoplanar photon fields) on the RTOG 0413 partial-breast trial. These cases were subsequently replanned using static gantry IMRT and V-MAT technology to understand dosimetric differences among these 3 techniques. Several dosimetric parameters were used in plan quality evaluation, including dose conformity index (CI) and dose-volume histogram analysis of normal tissue coverage. Quality assurance studies including gamma analysis were performed to compare the measured and calculated dose distributions. The IMRT and V-MAT plans gave more conformal target dose distributions than the 3D-CRT plans (p < 0.05 in CI). The volume of ipsilateral breast receiving 5 and 10 Gy was significantly less using the V-MAT technique than with either 3D-CRT or IMRT (p < 0.05). The maximum lung dose and the ipsilateral lung volume receiving 10 (V{sub 10}) or 20 Gy (V{sub 20}) were significantly less with both V-MAT and IMRT (p < 0.05). The IMRT technique was superior to 3D-CRT and V-MAT of low dose distributions in ipsilateral lung (p < 0.05 in V{sub 5} and D{sub 5}). The total mean monitor units (MUs) for V-MAT (621.0 ± 111.9) were 12.2% less than those for 3D-CRT (707.3 ± 130.9) and 46.5% less than those for IMRT (1161.4 ± 315.6) (p < 0.05). The average machine delivery time was 1.5 ± 0.2 minutes for the V-MAT plans, 7.0 ± 1.6 minutes for the 3D-CRT plans, and 11.5 ± 1.9 minutes for the IMRT plans, demonstrating much less delivery time for V-MAT. Based on this preliminary study, V-MAT and IMRT techniques offer improved dose conformity as compared with 3D-CRT techniques without increasing dose to the ipsilateral lung. In

  12. Uniqueness of the momentum map

    NASA Astrophysics Data System (ADS)

    Esposito, Chiara; Nest, Ryszard

    2016-08-01

    We give a detailed discussion of existence and uniqueness of the momentum map associated to Poisson Lie actions, which was defined by Lu. We introduce a weaker notion of momentum map, called infinitesimal momentum map, which is defined on one-forms and we analyze its integrability to the Lu's momentum map. Finally, the uniqueness of the Lu's momentum map is studied by describing, explicitly, the tangent space to the space of momentum maps.

  13. Interest rates mapping

    NASA Astrophysics Data System (ADS)

    Kanevski, M.; Maignan, M.; Pozdnoukhov, A.; Timonin, V.

    2008-06-01

    The present study deals with the analysis and mapping of Swiss franc interest rates. Interest rates depend on time and maturity, defining term structure of the interest rate curves (IRC). In the present study IRC are considered in a two-dimensional feature space-time and maturity. Exploratory data analysis includes a variety of tools widely used in econophysics and geostatistics. Geostatistical models and machine learning algorithms (multilayer perceptron and Support Vector Machines) were applied to produce interest rate maps. IR maps can be used for the visualisation and pattern perception purposes, to develop and to explore economical hypotheses, to produce dynamic asset-liability simulations and for financial risk assessments. The feasibility of an application of interest rates mapping approach for the IRC forecasting is considered as well.

  14. Mars planimetric mapping

    NASA Astrophysics Data System (ADS)

    Batson, R. M.; Bridges, P. M.; Lee, E. M.

    1985-04-01

    The 1:5,000,000 scale shaded relief maps of Mars originally compiled from Mariner 9 pictures are being upgraded by adding details visible on Viking Orbiter images. This work is done by modifying the original airbrush drawings; no attempt is made to reposition features according to the latest control nets. Thirteen of these maps have been published to date, two are in compilation, and two are in press. A hard cover atlas containing reduced scale versions of all Mars cartographic products will be published upon completion of the revisions of the 1:5,000,000 scale maps, the 1:2,000,000 scale photomosaics, and Mars color albedo mapping tasks. This atlas will supersede the existing Atlas of Mars prepared by Batson and others.

  15. Mapping Earth Science Concepts.

    ERIC Educational Resources Information Center

    McDuffie, Thomas E., Jr.; Van Dine, William E.

    1978-01-01

    Presents two experiments concerned with mapping skills. Directions are given for calculating the circumference of the earth and for developing a model of the solar system using familiar territory as a frame of reference. (MA)

  16. Reading Angles in Maps

    PubMed Central

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S.

    2013-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15–53:30 months) were presented with fragments of geometric maps, in which angle sections appeared without any relevant length or distance information. Children were able to read these map fragments and compare 2D to 3D angles. However, this ability appeared both variable and fragile among the youngest children of the sample. These findings suggest that 4-year-old children begin to form an abstract concept of angle that applies both to 2D and 3D displays and that serves to interpret novel spatial symbols. PMID:23647223

  17. Obesity Prevalence Maps

    MedlinePlus

    ... Physical Activity Overweight & Obesity Healthy Weight Breastfeeding Micronutrient Malnutrition State and Local Programs Adult Obesity Prevalence Maps ... Physical Activity Overweight & Obesity Healthy Weight Breastfeeding Micronutrient Malnutrition State and Local Programs File Formats Help: How ...

  18. DAM - detection and mapping

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Integrated set of manual procedures, computer programs, and graphic devices processes multispectral scanner data from orbiting Landsat into precisely registered and formatted maps of surface water and other resources at variety of scales, sheet formats, and tick intervals.

  19. Dating the Vinland Map

    ScienceCinema

    None

    2013-07-17

    Scientists from Brookhaven National Laboratory, the University of Arizona, and the Smithsonian Institution used carbon-dating technology to determine the age of a controversial parchment that might be the first-ever map of North America.

  20. Dating the Vinland Map

    SciTech Connect

    2013-01-04

    Scientists from Brookhaven National Laboratory, the University of Arizona, and the Smithsonian Institution used carbon-dating technology to determine the age of a controversial parchment that might be the first-ever map of North America.

  1. enceladus_stress_map

    NASA Video Gallery

    This is a map of the changing stress on the surface of Enceladus' icy crust from the wobble and gravitational tides. Blue lines show the direction of forces pulling the crust apart, and red lines s...

  2. Barrier Island Hazard Mapping.

    ERIC Educational Resources Information Center

    Pilkey, Orrin H.; Neal, William J.

    1980-01-01

    Describes efforts to evaluate and map the susceptibility of barrier islands to damage from storms, erosion, rising sea levels and other natural phenomena. Presented are criteria for assessing the safety and hazard potential of island developments. (WB)

  3. Irrigation on Topographic Maps.

    ERIC Educational Resources Information Center

    Raitz, Karl B.

    1979-01-01

    Describes how study of irrigation practices on topographic maps can help students in introductory high school and college geography courses understand man and land relationships to geography. (Author/DB)

  4. Reading angles in maps.

    PubMed

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S

    2014-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections appeared without any relevant length or distance information. Children were able to read these map fragments and compare two-dimensional to three-dimensional angles. However, this ability appeared both variable and fragile among the youngest children of the sample. These findings suggest that 4-year-old children begin to form an abstract concept of angle that applies both to two-dimensional and three-dimensional displays and that serves to interpret novel spatial symbols. PMID:23647223

  5. Map of physics

    NASA Astrophysics Data System (ADS)

    2008-10-01

    Based on bibliometric data from information-services provider Thomson Reuters, this map reveals "core areas" of physics, shown as coloured circular nodes, and the relationship between these subdisciplines, shown as lines.

  6. 100 Weekly Sky Maps

    NASA Technical Reports Server (NTRS)

    2002-01-01

    100 Aum Weekly Sky Maps for mission weeks 4 to 44, and the 100 Aum Annual Average Map. Shows sky coverage each week of the DIRBE mission over the period during which the COBE cryogen supply lasted. As the Earth, with COBE in orbit, revolved around the Sun, DIRBE viewed the sky from an ever-changing vantage point in the solar system, enabling light reflected and emitted by the interplanetary dust cloud to be modeled.

  7. Mapping the human genome

    SciTech Connect

    Annas, G.C.; Elias, S.

    1992-01-01

    This article is a review of the book Mapping the Human Genome: Using Law and Ethics as Guides, edited by George C. Annas and Sherman Elias. The book is a collection of essays on the subject of using ethics and laws as guides to justify human gene mapping. It addresses specific issues such problems related to eugenics, patents, insurance as well as broad issues such as the societal definitions of normality.

  8. Wind Resource Maps (Postcard)

    SciTech Connect

    Not Available

    2011-07-01

    The U.S. Department of Energy's Wind Powering America initiative provides high-resolution wind maps and estimates of the wind resource potential that would be possible from development of the available windy land areas after excluding areas unlikely to be developed. This postcard is a marketing piece that stakeholders can provide to interested parties; it will guide them to Wind Powering America's online wind energy resource maps.

  9. Treatment planning and dosimetric comparison study on two different volumetric modulated arc therapy delivery techniques

    PubMed Central

    Kumar, S.A. Syam; Holla, Raghavendra; Sukumar, Prabakar; Padmanaban, Sriram; Vivekanandan, Nagarajan

    2012-01-01

    Aim To compare and evaluate the performance of two different volumetric modulated arc therapy delivery techniques. Background Volumetric modulated arc therapy is a novel technique that has recently been made available for clinical use. Planning and dosimetric comparison study was done for Elekta VMAT and Varian RapidArc for different treatment sites. Materials and methods Ten patients were selected for the planning comparison study. This includes 2 head and neck, 2 oesophagus, 1 bladder, 3 cervix and 2 rectum cases. Total dose of 50 Gy was given for all the plans. All plans were done for RapidArc using Eclipse and for Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X-rays for both RapidArc and Elekta VMAT. Plans were evaluated based on the ability to meet the dose volume histogram, dose homogeneity index, radiation conformity index, estimated radiation delivery time, integral dose and monitor units needed to deliver the prescribed dose. Results RapidArc plans achieved the best conformity (CI95% = 1.08 ± 0.07) while Elekta VMAT plans were slightly inferior (CI95% = 1.10 ± 0.05). The in-homogeneity in the PTV was highest with Elekta VMAT with HI equal to 0.12 ± 0.02 Gy when compared to RapidArc with 0.08 ± 0.03. Significant changes were observed between the RapidArc and Elekta VMAT plans in terms of the healthy tissue mean dose and integral dose. Elekta VMAT plans show a reduction in the healthy tissue mean dose (6.92 ± 2.90) Gy when compared to RapidArc (7.83 ± 3.31) Gy. The integral dose is found to be inferior with Elekta VMAT (11.50 ± 6.49) × 104 Gy cm3 when compared to RapidArc (13.11 ± 7.52) × 104 Gy cm3. Both Varian RapidArc and Elekta VMAT respected the planning objective for all organs at risk. Gamma analysis result for the pre-treatment quality assurance shows good agreement between the planned and delivered fluence for 3 mm DTA, 3% DD for all the evaluated points inside the

  10. Dosimetric advantages of IMRT simultaneous integrated boost for high-risk prostate cancer

    SciTech Connect

    Li, X. Allen . E-mail: ali@radonc.mcw.edu; Wang, Jian Z.; Jursinic, Paul A.; Lawton, Colleen A.; Wang Dian

    2005-03-15

    Purpose: A sequential two-phase process, initial and boost irradiation, is the common practice for the radiotherapy management of high-risk prostate cancer. In this work, we explore the feasibility of using intensity modulated radiation therapy (IMRT) simultaneous integrated boost (SIB), a single-phase process, to simultaneously deliver high dose to the prostate and lower dose to the pelvic nodes. In addition, we introduce the concept of voxel-equivalent dose for the comparison of treatment plans. Methods and materials: The SIB is designed to deliver the same dose (e.g., 45 Gy, 25 x 1.8 Gy) as the conventional method to the pelvic nodes and to deliver higher doses to prostate in the same 25 fractions (i.e., hypofractionation). The equivalent uniform dose (EUD) was used to determine suitable SIB fractionations that deliver the biologically equivalent doses to prostate. For tumor, the EUD was estimated based on the linear quadratic (LQ) model. The most recent LQ parameters derived from clinical data for prostate cancer were used. The sensitivity of LQ parameters was evaluated. The EUD for normal tissue was computed based on the widely used Lyman model. To be able to consider biologic effectiveness spatially (e.g., voxel by voxel), we propose a new concept, termed the voxel-equivalent dose (VED). The calculation of VED was similar to that for EUD, except that it was done within a voxel. To demonstrate dosimetric feasibility and advantages of the proposed IMRT SIB, we have performed a retrospective planning study on selected patient cases using commercial IMRT and three-dimensional (3D) planning systems. Four treatment scenarios were considered: (1) the conventional 3D plan for initial whole-pelvic irradiation and subsequent conventional 3D boost plan for prostate gland (2) the conventional 3D plan for initial whole-pelvic irradiation and subsequent IMRT boost plan for prostate (3) IMRT plan for initial whole-pelvic irradiation and subsequent IMRT boost plan for

  11. Simultaneous integrated intensity-modulated radiotherapy boost for locally advanced gynecological cancer: Radiobiological and dosimetric considerations

    SciTech Connect

    Guerrero, Mariana; Li, X. Allen . E-mail: ali@radonc.mcw.edu; Ma Lijun; Linder, Jeanette; Deyoung, Chad; Erickson, Beth

    2005-07-01

    Purpose: Whole-pelvis irradiation (WPI) followed by a boost to the tumor site is the standard of practice for the radiotherapeutic management of locally advanced gynecologic cancers. The boost is frequently administered by use of brachytherapy or, occasionally, external-beam radiotherapy (EBRT) when brachytherapy does not provide sufficient coverage because of the size of the tumor or the geometry of the patient. In this work, we propose using an intensity-modulated radiotherapy (IMRT) simultaneous integrated boost (SIB), which is a single-phase process, to replace the conventional two-phase process involving WPI plus a boost. Radiobiological modeling is used to design appropriate regimens for the IMRT SIB. To demonstrate feasibility, a dosimetric study is carried out on an example patient. Methods and Materials: The standard linear-quadratic (LQ) model is used to calculate the biologically effective dose (BED) and equivalent uniform dose (EUD). A series of regimens that are biologically equivalent to those conventional two-phase treatments is calculated for the proposed SIB. A commercial inverse planning system (Corvus) was used to generate IMRT SIB plans for a sample patient case that used the newly designed fractionations. The dose-volume histogram (DVH) and EUD of both the target and normal structures for conventional treatments and the SIB are compared. A sparing factor was introduced to characterize the sparing of normal structures. Results: Fractionation regimes that are equivalent to the conventional treatments and are suitable for the IMRT SIB are deduced. For example, a SIB plan with 25 x 3.1 Gy (77.5 Gy) to a tumor is equivalent to a conventional treatment of EBRT of 45 Gy to the whole pelvis in 25 fractions plus a high-dose rate (HDR) brachytherapy boost with 30 Gy in 5 fractions. The normal tissue BED is found to be lower for the SIB plan than for the whole-pelvis plus HDR scheme when a sparing factor for the critical structures is considered. This

  12. Dosimetric impact of image artifact from a wide-bore CT scanner in radiotherapy treatment planning

    SciTech Connect

    Wu, Vincent; Podgorsak, Matthew B.; Tran, Tuan-Anh; Malhotra, Harish K.; Wang, Iris Z.

    2011-07-15

    Purpose: Traditional computed tomography (CT) units provide a maximum scan field-of-view (sFOV) diameter of 50 cm and a limited bore size, which cannot accommodate a large patient habitus or an extended simulation setup in radiation therapy (RT). Wide-bore CT scanners with increased bore size were developed to address these needs. Some scanners have the capacity to reconstruct the CT images at an extended FOV (eFOV), through data interpolation or extrapolation, using projection data acquired with a conventional sFOV. Objects that extend past the sFOV for eFOV reconstruction may generate image artifacts resulting from truncated projection data; this may distort CT numbers and structure contours in the region beyond the sFOV. The purpose of this study was to evaluate the dosimetric impact of image artifacts from eFOV reconstruction with a wide-bore CT scanner in radiotherapy (RT) treatment planning. Methods: Testing phantoms (i.e., a mini CT phantom with equivalent tissue inserts, a set of CT normal phantoms and anthropomorphic phantoms of the thorax and the pelvis) were used to evaluate eFOV artifacts. Reference baseline images of these phantoms were acquired with the phantom centrally positioned within the sFOV. For comparison, the phantoms were then shifted laterally and scanned partially outside the sFOV, but still within the eFOV. Treatment plans were generated for the thoracic and pelvic anthropomorphic phantoms utilizing the Eclipse treatment planning system (TPS) to study the potential effects of eFOV artifacts on dose calculations. All dose calculations of baseline and test treatment plans were carried out using the same MU. Results: Results show that both body contour and CT numbers are altered by image artifacts in eFOV reconstruction. CT number distortions of up to -356 HU for bone tissue and up to 323 HU for lung tissue were observed in the mini CT phantom. Results from the large body normal phantom, which is close to a clinical patient size, show

  13. Prostate brachytherapy postimplant dosimetry: Seed orientation and the impact of dosimetric anisotropy in stranded implants

    SciTech Connect

    Chng, Nicholas; Spadinger, Ingrid; Rasoda, Rosey; Morris, W. James; Salcudean, Septimiu

    2012-02-15

    Purpose: In postimplant dosimetry for prostate brachytherapy, dose is commonly calculated using the TG-43 1D formalism, because seed orientations are difficult to determine from CT images, the current standard for the procedure. However, the orientation of stranded seeds soon after implantation is predictable, as these seeds tend to maintain their relative spacing, and orient themselves along the implant trajectory. The aim of this study was to develop a method for determining seed orientations from reconstructed strand trajectories, and to use this information to investigate the dosimetric impact of applying the TG-43 2D formalism to clinical postimplant analysis. Methods: Using in-house software, the preplan to postimplant seed correspondence was determined for a cohort of 30 patients during routine day-0 CT-based postimplant dosimetry. All patients were implanted with stranded-seed trains. Spline curves were fit to each set of seeds composing a strand, with the requirement that the distance along the spline between seeds be equal to the seed spacing within the strand. The orientations of the seeds were estimated by the tangents to the spline at each seed centroid. Dose distributions were then determined using the 1D and 2D TG-43 formalisms. These were compared using the TG-137 recommended dose metrics for the prostate, prostatic urethra, and rectum. Results: Seven hundred and sixty one strands were analyzed in total. Defining the z-axis to be cranial-positive and the x-axis to be left-lateral positive in the CT coordinate system, the average seed had an inclination of 21 deg. {+-} 10 deg. and an azimuth of -81 deg. {+-} 57 deg. These values correspond to the average strand rising anteriorly from apex to base, approximately parallel to the midsagittal plane. Clinically minor but statistically significant differences in dose metrics were noted. Compared to the 2D calculation, the 1D calculation underestimated prostate V100 by 1.1% and D90 by 2.3 Gy, while

  14. Dosimetric characterization of the iBEAM evo carbon fiber couch for radiotherapy

    SciTech Connect

    Smith, David W.; Christophides, Damianos; Dean, Christopher; Naisbit, Mitchell; Mason, Joshua; Morgan, Andrew

    2010-07-15

    Purpose: This study characterizes the dosimetric properties of the iBEAM evo carbon fiber couch manufactured by Medical Intelligence and examines the accuracy of the CMS XiO and Nucletron Oncentra Masterplan (OMP) treatment planning systems for calculating beam attenuation due to the presence of the couch. Methods: To assess the homogeneity of the couch, it was CT scanned at isocentric height and a number of signal intensity profiles were generated and analyzed. To simplify experimental procedures, surface dose and central axis depth dose measurements were performed in a solid water slab phantom using Gafchromic film for 6 and 10 MV photon beams at gantry angles of 0 deg. (normal incidence), 30 deg., and 60 deg. with an inverted iBEAM couch placed on top of the phantom. Attenuation measurements were performed in a cylindrical solid water phantom with an ionization chamber positioned at the isocenter. Measurements were taken for gantry angles from 0 deg. to 90 deg. in 10 deg. increments for both 6 and 10 MV photon beams. This setup was replicated in the XiO and OMP treatment planning systems. Dose was calculated using the pencil beam, collapsed cone, convolution, and superposition algorithms. Results: The CT scan of the couch showed that it was uniformly constructed. Surface dose increased by (510{+-}30)% for a 6 MV beam and (600{+-}20)% for a 10 MV beam passing through the couch at normal incidence. Obliquely incident beams resulted in a higher surface dose compared to normally incident beams for both open fields and fields with the couch present. Depth dose curves showed that the presence of the couch resulted in an increase in dose in the build up region. For 6 and 10 MV beams incident at 60 deg., nearly all skin sparing was lost. Attenuation measurements derived using the ionization chamber varied from 2.7% (0 deg.) to a maximum of 4.6% (50 deg.) for a 6 MV beam and from 1.9% (0 deg.) to a maximum of 4.0% (50 deg.) for a 10 MV beam. The pencil beam and