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Radiation sensitive MOSFETs irradiated with various positive gate biases. JOURNAL OF RADIATION RESEARCH AND APPLIED SCIENCES 2021. [DOI: 10.1080/16878507.2021.1970921] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Monte Carlo calculation of charge collection efficiencies in ionization chambers. Phys Med Biol 2021; 66:045011. [PMID: 33339014 DOI: 10.1088/1361-6560/abd4f8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Collection efficiency is an important quantity in dosimetry with ionization chambers. It can be calculated by solving a hyperbolic system of partial differential equations. This system can be solved only in few, simple, idealized geometries, but for more realistic designs an analytical resolution is no longer possible. In the present work a Monte Carlo scheme that could permit to calculate the collection efficiency for any ionization chamber geometry is proposed. This scheme has been tested against Boag's approach for three chambers with plane-parallel, cylindrical and spherical geometries, operated in the recombination regime. The results obtained in the full Monte Carlo simulation closely agree with the Boag's ones for the three ideal geometries considered. The largest relative difference, ∼0.3%, has been found for the plane-parallel chamber in case of 50 V, the lowest potential difference investigated in this study. Results appear to be stable against changes in the chamber volume, the ion mobility and the recombination constant. The method proposed could be a useful tool to calculate collection efficiencies of ionization chambers, provided the electric field inside them is known.
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Response of the ArcCHECK® device at 6 MV and 15 MV for VMAT and IMRT quality control. Phys Med 2020; 80:373-382. [PMID: 33310373 DOI: 10.1016/j.ejmp.2020.11.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 11/10/2020] [Accepted: 11/14/2020] [Indexed: 10/22/2022] Open
Abstract
PURPOSE To study the response of the ArcCHECK® device as VMAT and IMRT verification system. METHODS Various tests analyzing the linearity, the repeatability and the angular dependence of the device response, its dependence with the pulse repetition rate and the leakage losses were performed. The long-term response in dose measurements and the uniformity of the detectors conforming the system were controlled using a statistical process control program. The Elekta Infinity™ 6 and 15MV photon beams were used. RESULTS The device showed excellent repeatability and linearity. The differences between the responses obtained for any pair of angular incidences were less than 2%. The absorbed dose increased by 3% when the pulse repetition rate varied from 50 to 600MU/min. Results are in overall agreement with those found in previous works for the ArcCHECK®, in which a reduced number of the device diodes were analyzed, and for the MapCheck®, an older 2D device that used the same diodes. Charge losses were found to be negligible except for some of the diodes of the device. The statistical process control program is a very useful tool to control the correct functioning of the device in the long term. CONCLUSIONS The results of the analysis carried out indicate that the working and stability conditions of the ArcCHECK® device are adequate for its purpose. The dependence with the pulse repetition rate should be considered when VMAT or similar treatments are evaluated. A control program for the statistical monitoring of the device would be desirable and useful.
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An on-lattice agent-based Monte Carlo model simulating the growth kinetics of multicellular tumor spheroids. Phys Med 2020; 77:194-203. [PMID: 32882615 DOI: 10.1016/j.ejmp.2020.07.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 07/19/2020] [Indexed: 11/26/2022] Open
Abstract
PURPOSE To develop an on-lattice agent-based model describing the growth of multicellular tumor spheroids using simple Monte Carlo tools. METHODS Cells are situated on the vertices of a cubic grid. Different cell states (proliferative, hypoxic or dead) and cell evolution rules, driven by 10 parameters, and the effects of the culture medium are included. About twenty spheroids of MCF-7 human breast cancer were cultivated and the experimental data were used for tuning the model parameters. RESULTS Simulated spheroids showed adequate sizes of the necrotic nuclei and of the hypoxic and proliferative cell phases as a function of the growth time, mimicking the overall characteristics of the experimental spheroids. The relation between the radii of the necrotic nucleus and the whole spheroid obtained in the simulations was similar to the experimental one and the number of cells, as a function of the spheroid volume, was well reproduced. The statistical variability of the Monte Carlo model described the whole volume range observed for the experimental spheroids. Assuming that the model parameters vary within Gaussian distributions it was obtained a sample of spheroids that reproduced much better the experimental findings. CONCLUSIONS The model developed allows describing the growth of in vitro multicellular spheroids and the experimental variability can be well reproduced. Its flexibility permits to vary both the agents involved and the rules that govern the spheroid growth. More general situations, such as, e. g., tumor vascularization, radiotherapy effects on solid tumors, or the validity of the tumor growth mathematical models can be studied.
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Simple variance reduction in Monte Carlo calculations of specific absorbed fractions: Russian roulette and splitting at the source organ. Biomed Phys Eng Express 2020; 6:035015. [PMID: 33438660 DOI: 10.1088/2057-1976/ab817f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE To investigate the capabilities of several variance reduction techniques in the calculation of specific absorbed fractions in cases where the source and the target organs are far away and/or the target organs have a small volume. METHODS The specific absorbed fractions have been calculated by using the Monte Carlo code PENELOPE and by assuming the thyroid gland as the source organ and the testicles, the urinary bladder, the uterus, and the ovaries as the target ones. A mathematical anthropomorphic phantom, similar to the MIRD-type phantoms, has been considered. Photons with initial energies of 50, 100 and 500 keV were emitted isotropically from the volume of the source organ. Simulations have been carried out by implementing the variance reduction techniques of splitting and Russian roulette at the source organ only and the interaction forcing at the target organs. The influence of the implementation details of those techniques have been investigated and optimal parameters have been determined. All simulations were run with a CPU time of 1.5 · 105 s. RESULTS Specific absorbed fractions with relative uncertainties well below 10% have been obtained in most cases, agreeing with those used as reference. The best value for the factor defining the application of the Russian roulette technique was r = 0.3. The best value for the splitting number was between s = 3 and s = 10, depending on the specific energies and target organs. CONCLUSIONS The proposed strategy provides an effective method for computing specific absorbed fractions for the most unfavorable situations, with a computing effort that is considerably reduced with respect to other methodologies.
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Evaluation of the overdiagnosis in breast screening programmes using a Monte Carlo simulation tool: a study of the influence of the parameters defining the programme configuration. BMJ Open 2019; 9:e023187. [PMID: 30782874 PMCID: PMC6398694 DOI: 10.1136/bmjopen-2018-023187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
OBJECTIVES To build up and test a Monte Carlo simulation procedure for the investigation of overdiagnosis in breast screening programmes (BSPs). DESIGN A Monte Carlo tool previously developed has been adapted for obtaining the quantities of interest in order to determine the overdiagnosis: the annual and cumulative number of cancers detected by screening, plus interval cancers, for a population following the BSP, and detected clinically for the same population in the absence of screening. Overdiagnosis is obtained by comparing these results in a direct way. RESULTS Overdiagnosis between 7% and 20%, depending on the specific configuration of the programme, have been found. These range of values is in agreement with some of the results available for actual BSPs. In the cases analysed, a reduction of 11% at most has been found in the number of invasive tumours detected by screening in comparison to those clinically detected in the control population. It has been possible to establish that overdiagnosis is almost entirely linked to ductal carcinoma in situ tumours. CONCLUSIONS The use of Monte Carlo tools may facilitate the analysis of overdiagnosis in actual BSPs, permitting to address the role played by various quantities of relevance for them.
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Fractal behavior of the trajectories of the foot centers of pressure during pregnancy. Biomed Phys Eng Express 2019. [DOI: 10.1088/2057-1976/aaf0f3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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[P150] Air density dependence of the response of the PTW sourcecheck 4PI ionization chamber to PD-103 brachytherapy sources. Phys Med 2018. [DOI: 10.1016/j.ejmp.2018.06.455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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[OA240] Comparison between four routine control devices detecting photon beam energy changes. Phys Med 2018. [DOI: 10.1016/j.ejmp.2018.06.312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Radiobiological parameters for breast cancer: a Monte Carlo analysis of START trial published results. Br J Radiol 2018; 91:20170979. [PMID: 30052466 DOI: 10.1259/bjr.20170979] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE: Trial results are usually given in terms of end point confidence intervals, the data concerning the participating patients being not available. Sometimes, it would be useful or necessary to obtain derived quantities, such as dose-response relationships, from the known information. In this work, we describe a methodology that allows to do that and illustrate it by analyzing the UK standardization of breast radiotherapy (START) trials. METHODS: Using Monte Carlo techniques, virtual data sets were generated by sampling trial outcome distributions in terms of the tumor control probability (described by means of a logistic dose response and the equations of isoeffect in the linear-quadratic model). After fitting the available experimental data, the radiobiological parameters of interest and their confidence intervals were obtained from the TCP vs 'EQD2 curve in which the surgery effect is also taken into account. RESULTS: The value of [Formula: see text] obtained for breast cancer was 3.6 Gy, with a 95% confidence interval of (1.5,15.5) Gy, in agreement with the one estimated by the START group. The time factor, referred to a scheme of 2 Gy per fraction, was 0.74 (0.41,2.67) Gy day-1, of the same order than that estimated for head and neck cancers. CONCLUSION: A methodology permitting an analysis of trial results was developed and tested with the results of the START trials. The procedure does not require detailed knowledge of the distributions actually found in the trials. The values obtained for the parameters are similar to those of the START estimations and this can be considered an independent confirmation of their validity, thus showing the model usefulness. The methodology presented here relies on basic statistical methods that are general enough to permit it to be applied to any kind of trial. This may be particularly interesting when the original data are no longer available. ADVANCES IN KNOWLEDGE: The main novelty of this paper is to provide with a Monte Carlo based tool that permits an independent analysis of published trial results in order to obtain radiobiological parameters without a detailed knowledge of the data corresponding to the participating patients.
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Impact of cardiosynchronous brain pulsations on Monte Carlo calculated doses for synchrotron micro‐ and minibeam radiation therapy. Med Phys 2018; 45:3379-3390. [DOI: 10.1002/mp.12973] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 04/02/2018] [Accepted: 05/05/2018] [Indexed: 11/07/2022] Open
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Performance of a virtual source model for stereotactic radiosurgery with a dynamic micro-multileaf collimator. Biomed Phys Eng Express 2017. [DOI: 10.1088/2057-1976/aa84ca] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Abstract ID: 79 Virtual source model for stereotactic radiosurgery with a dynamic micro-multileaf collimator. Phys Med 2017. [DOI: 10.1016/j.ejmp.2017.09.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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A Monte Carlo analysis of breast screening randomized trials. Phys Med 2016; 32:1609-1614. [PMID: 27914780 DOI: 10.1016/j.ejmp.2016.11.116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 10/16/2016] [Accepted: 11/16/2016] [Indexed: 11/16/2022] Open
Abstract
PURPOSE To analyze breast screening randomized trials with a Monte Carlo simulation tool. METHODS A simulation tool previously developed to simulate breast screening programmes was adapted for that purpose. The history of women participating in the trials was simulated, including a model for survival after local treatment of invasive cancers. Distributions of time gained due to screening detection against symptomatic detection and the overall screening sensitivity were used as inputs. Several randomized controlled trials were simulated. Except for the age range of women involved, all simulations used the same population characteristics and this permitted to analyze their external validity. The relative risks obtained were compared to those quoted for the trials, whose internal validity was addressed by further investigating the reasons of the disagreements observed. RESULTS The Monte Carlo simulations produce results that are in good agreement with most of the randomized trials analyzed, thus indicating their methodological quality and external validity. A reduction of the breast cancer mortality around 20% appears to be a reasonable value according to the results of the trials that are methodologically correct. Discrepancies observed with Canada I and II trials may be attributed to a low mammography quality and some methodological problems. Kopparberg trial appears to show a low methodological quality. CONCLUSION Monte Carlo simulations are a powerful tool to investigate breast screening controlled randomized trials, helping to establish those whose results are reliable enough to be extrapolated to other populations and to design the trial strategies and, eventually, adapting them during their development.
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Testing Monte Carlo absolute dosimetry formalisms for a small field ‘D’-shaped collimator used in retinoblastoma external beam radiotherapy. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/2/6/065008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Monte Carlo systems used for treatment planning and dose verification. Strahlenther Onkol 2016; 193:243-259. [PMID: 27888282 DOI: 10.1007/s00066-016-1075-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 10/25/2016] [Indexed: 11/28/2022]
Abstract
General-purpose radiation transport Monte Carlo codes have been used for estimation of the absorbed dose distribution in external photon and electron beam radiotherapy patients since several decades. Results obtained with these codes are usually more accurate than those provided by treatment planning systems based on non-stochastic methods. Traditionally, absorbed dose computations based on general-purpose Monte Carlo codes have been used only for research, owing to the difficulties associated with setting up a simulation and the long computation time required. To take advantage of radiation transport Monte Carlo codes applied to routine clinical practice, researchers and private companies have developed treatment planning and dose verification systems that are partly or fully based on fast Monte Carlo algorithms. This review presents a comprehensive list of the currently existing Monte Carlo systems that can be used to calculate or verify an external photon and electron beam radiotherapy treatment plan. Particular attention is given to those systems that are distributed, either freely or commercially, and that do not require programming tasks from the end user. These systems are compared in terms of features and the simulation time required to compute a set of benchmark calculations.
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Photon beam quality correction factors for the NE2571A and NE2581A thimble ionization chambers using PENELOPE. Phys Med 2016; 32:232-6. [DOI: 10.1016/j.ejmp.2015.09.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 09/03/2015] [Accepted: 09/28/2015] [Indexed: 10/22/2022] Open
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Characterization of the PTW SourceCheck ionization chamber with the Valencia lodgment for 125 I seed verification. Phys Med 2015; 31:922-928. [DOI: 10.1016/j.ejmp.2015.07.142] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 06/19/2015] [Accepted: 07/13/2015] [Indexed: 10/22/2022] Open
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A source model for the electron contamination of clinical linac heads in photon mode. Biomed Phys Eng Express 2015. [DOI: 10.1088/2057-1976/1/2/025202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Monte Carlo calculation of specific absorbed fractions: variance reduction techniques. Phys Med Biol 2015; 60:2625-44. [DOI: 10.1088/0031-9155/60/7/2625] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Dosimetric characterization of the 60Co BEBIG Co0.A86 high dose rate brachytherapy source using PENELOPE. Phys Med 2014; 30:960-7. [DOI: 10.1016/j.ejmp.2014.06.039] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Revised: 06/04/2014] [Accepted: 06/18/2014] [Indexed: 11/24/2022] Open
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Electron beam qualitykQ,Q0factors for various ionization chambers: a Monte Carlo investigation with penelope. Phys Med Biol 2014; 59:6673-91. [DOI: 10.1088/0022-3727/59/21/6673] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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A method to relate StarTrack(®) measurements to R50 variations in clinical linacs. Phys Med 2014; 30:827-32. [PMID: 24735905 DOI: 10.1016/j.ejmp.2014.03.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 03/18/2014] [Accepted: 03/19/2014] [Indexed: 11/16/2022] Open
Abstract
The relation between the data recorded with any device for the daily checking of the behavior of a clinical linac and the reference magnitudes to be monitored may be unknown. An experimental method relating the energy stability of the electron beam measured with StarTrack(®) to the R50 beam quality index is proposed. The bending magnet current is varied producing a change in the exit energy window and, therefore, a modification of the R50 value. For different values of this current, the output data of StarTrack(®) and the R50, obtained from depth doses measured in a water phantom are determined. A linear fit between both sets of data allows the identification of the StarTrack(®) output that provides the best way to obtain the quality index R50, for each beam nominal energy. Using these fits, an historical datum series is used to analyze the method proposed in the daily quality control. The ouput data of the StarTrack(®) and the R50 values show a good linear correlation. It is possible to establish a methodology that allows the monitoring of R50 by direct use of the daily quality control data measured with StarTrack(®). A method to monitor R50 in the daily quality control using the StarTrack(®) device has been developed. The method may be applied to similar devices in which the statistical control variable does not show a linear behavior with R50.
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On the shape of the Task Group 43 anisotropy factor for linear brachytherapy sources at short distances. Brachytherapy 2014; 13:424-9. [PMID: 24561104 DOI: 10.1016/j.brachy.2014.01.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 01/16/2014] [Accepted: 01/17/2014] [Indexed: 11/26/2022]
Abstract
PURPOSE To investigate the peak shown by the American Association of Physicists in Medicine (AAPM) Task Group 43 1D anisotropy function at short distances from the source. METHODS AND MATERIALS The 1D anisotropy function of an ideal nonencapsulated photon linear source is calculated. A simple analytical model developed to evaluate the dose because of photon point-like sources has been applied. Previously, the model has been tested by comparing the values obtained for the various Task Group 43 dosimetric functions with those calculated with the Monte Carlo code PENELOPE for three different photon energies. RESULTS The model is able to reproduce the behavior of the 1D anisotropy function, describing the maximum that appears at a distance between 1 and 2 mm from the source. The reason for this behavior has been identified in terms of the contributions of the source activity inside and outside the scoring sphere. CONCLUSIONS Although it is not usually shown in reference data, this behavior should be taken into account for accurate dosimetric calculations.
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Monte Carlo study for designing a dedicated "D"-shaped collimator used in the external beam radiotherapy of retinoblastoma patients. Med Phys 2014; 41:011714. [PMID: 24387506 DOI: 10.1118/1.4855855] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Retinoblastoma is the most common intraocular malignancy in the early childhood. Patients treated with external beam radiotherapy respond very well to the treatment. However, owing to the genotype of children suffering hereditary retinoblastoma, the risk of secondary radio-induced malignancies is high. The University Hospital of Essen has successfully treated these patients on a daily basis during nearly 30 years using a dedicated "D"-shaped collimator. The use of this collimator that delivers a highly conformed small radiation field, gives very good results in the control of the primary tumor as well as in preserving visual function, while it avoids the devastating side effects of deformation of midface bones. The purpose of the present paper is to propose a modified version of the "D"-shaped collimator that reduces even further the irradiation field with the scope to reduce as well the risk of radio-induced secondary malignancies. Concurrently, the new dedicated "D"-shaped collimator must be easier to build and at the same time produces dose distributions that only differ on the field size with respect to the dose distributions obtained by the current collimator in use. The scope of the former requirement is to facilitate the employment of the authors' irradiation technique both at the authors' and at other hospitals. The fulfillment of the latter allows the authors to continue using the clinical experience gained in more than 30 years. METHODS The Monte Carlo code PENELOPE was used to study the effect that the different structural elements of the dedicated "D"-shaped collimator have on the absorbed dose distribution. To perform this study, the radiation transport through a Varian Clinac 2100 C/D operating at 6 MV was simulated in order to tally phase-space files which were then used as radiation sources to simulate the considered collimators and the subsequent dose distributions. With the knowledge gained in that study, a new, simpler, "D"-shaped collimator is proposed. RESULTS The proposed collimator delivers a dose distribution which is 2.4 cm wide along the inferior-superior direction of the eyeball. This width is 0.3 cm narrower than that of the dose distribution obtained with the collimator currently in clinical use. The other relevant characteristics of the dose distribution obtained with the new collimator, namely, depth doses at clinically relevant positions, penumbrae width, and shape of the lateral profiles, are statistically compatible with the results obtained for the collimator currently in use. CONCLUSIONS The smaller field size delivered by the proposed collimator still fully covers the planning target volume with at least 95% of the maximum dose at a depth of 2 cm and provides a safety margin of 0.2 cm, so ensuring an adequate treatment while reducing the irradiated volume.
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Dependence with air density of the response of the PTW SourceCheck ionization chamber for low energy brachytherapy sources. Med Phys 2013; 40:122103. [DOI: 10.1118/1.4831757] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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A simple modification of TG-43 based brachytherapy dosimetry with improved fitting functions: Application to the selectSeed source. Phys Med 2013; 29:403-11. [DOI: 10.1016/j.ejmp.2012.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 05/10/2012] [Accepted: 05/18/2012] [Indexed: 11/28/2022] Open
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A Monte Carlo tool to study the mortality reduction due to breast screening programs. Med Phys 2013; 39:7215-23. [PMID: 23231272 DOI: 10.1118/1.4764484] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To develop a Monte Carlo tool that permits to study the reduction in breast cancer mortality rate due to breast screening programs. METHODS Simulations implement woman histories undergoing a screening program, include a model of survival after local treatment of invasive cancers and use distributions of time gained due to screening detection against symptomatic detection and overall sensitivity of the screening obtained previously. Mortalities for the whole woman population and for those women with ages within the range considered in the program have been calculated. RESULTS For the whole woman population, a reduction in breast cancer mortality up to 29% has been found for a configuration that includes women aged between 50 and 70 years, with a screening interval of two years and 100% acceptance rate. If an acceptance of 70% is considered, this percentage reduces to 20%. If, in the same conditions, the program starts at 40 years, the reduction of the mortality reaches 24% while if the screening interval is one year, this percentage raises to 28%. If mortalities are calculated for those women with ages within the range included in the program these reductions are greater and no significant differences are found between the programs with age ranges [50-70] and [40-70]. In the model, radio-induced cancers have no effect in survival. CONCLUSIONS The results agree reasonably well with those of different trials. Mortality reductions of 12%-20% (between two and four deaths per year and 10(5) women) are obtained only for acceptances above 50%. This could be considered as a threshold for the acceptance, which appears to be a critical parameter.
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Calculation of beam quality correction factors for various thimble ionization chambers using the Monte Carlo code PENELOPE. Phys Med 2013; 29:163-70. [DOI: 10.1016/j.ejmp.2012.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 12/31/2011] [Accepted: 01/05/2012] [Indexed: 10/14/2022] Open
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Abstract
OBJECTIVE We propose and study a new model aimed at describing the low-dose hyper-radiosensitivity phenomenon appearing in the survival curves of different cell lines. METHODS The model uses the induced repair assumption, considering that the critical dose at which this mechanism begins to act varies from cell to cell in a given population. The model proposed is compared with the linear-quadratic model and the modified linear-quadratic model, which is commonly used in literature and in which the induced repair is taken into account in a heuristic way. The survival curve for the MCF-7 line of human breast cancer is measured at low absorbed doses and the uncertainties in these doses are estimated using thermoluminiscent dosemeters. RESULTS It is shown that these multicellular spheroids present low-dose hyper-radiosensitivity. The new model permits an accurate description of the data of two human cell lines (previously published) and of the multicellular spheroids of the MCF-7 line here measured. CONCLUSION The model shows enough flexibility to account for data with very different characteristics and considers in a faithful way the hypothesis of the repair induction.
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Retinoblastoma external beam photon irradiation with a special ‘D’-shaped collimator: a comparison between measurements, Monte Carlo simulation and a treatment planning system calculation. Phys Med Biol 2012; 57:7741-51. [DOI: 10.1088/0031-9155/57/22/7741] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Monte Carlo simulation of COMS ophthalmic applicators loaded with Bebig I25.S16 seeds and comparison with planning system predictions. Phys Med 2012; 29:670-6. [PMID: 22858007 DOI: 10.1016/j.ejmp.2012.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2012] [Revised: 06/29/2012] [Accepted: 07/09/2012] [Indexed: 10/28/2022] Open
Abstract
PURPOSE To simulate the Bebig model I125.S16 source and obtain AAPM Task Group Report 43 brachytherapy dosimetry parameters for comparison to consensus and previously published values. The seed model will then be incorporated into a Monte Carlo model of COMS eye plaques and simulation results will be used for seed-carrier set modeling in a commercial planning system. METHODS PENELOPE was used to simulate the seed and the applicators for different sizes and loading levels. The corresponding TG-43U1 dosimetric parameters of the seed were calculated. Bebig Plaque Simulator was used. RESULTS The air kerma strength, the dose rate constant and the radial dose and 2D anisotropy functions found showed a good agreement with those published by other authors. Dose distributions were determined for the 12 and 20 mm COMS plaques loaded with a single seed and for the 12 mm plaque fully loaded. The plaque effect on the eye dose and the interseed absorption were evaluated. If the plaque is loaded with a single seed, the dose in the central axis reduces about 10% at 5-6 mm depth with respect to the case in which the plaque is not present. This reduction does not depend on the plaque size. When the plaque is fully loaded, an additional reduction in the dose with respect to the dose in water is observed mainly due to the effect of the Silastic carrier. The mean dose reduction in the central axis of the 12 mm plaque due to the interseed absorption was 0.5%. A new physics file for the planning system was created with the results obtained from the simulations. Results obtained using this adapted model for the 12 mm plaque fully loaded agreed with the corresponding simulation. Dose rate at the prescription point differs 4.7% when the adapted model is used instead of the default model. CONCLUSIONS Simulation results for COMS plaques are consistent with those published for other seeds. The planning system studied appears as a good tool for dose calculation in ophthalmic brachytherapy treatments. The new physics model, built up from Monte Carlo results, has been commissioned by comparing calculations made with the planning system to those obtained from Monte Carlo simulations.
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Specific absorbed fractions in thyroid diagnostics and treatment: Monte Carlo calculation with PENELOPE. RADIATION PROTECTION DOSIMETRY 2012; 150:41-49. [PMID: 21914641 DOI: 10.1093/rpd/ncr372] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In nuclear medicine, diagnostic and therapy procedures in which a certain radiopharmaceutical is administered to a patient are performed. An important point is the determination of the dose absorbed by the important organs of the patient due to these procedures. This dose depends on the particular radionuclide used and the so-called specific absorbed fractions. In this work, by means of Monte Carlo (MC) simulation, the specific absorbed fractions in case the thyroid gland acts as a source organ and for photon energies between 30 keV and 2 MeV have been determined. The computer code PENELOPE has been used as well as the adult male mathematical phantom provided with the distribution of this code. Three different simulation types were carried out. In one of them, only photon transport was considered. In the other two, electron transport was included, doing a detailed and a mixed simulation. In general, the fractions were estimated with uncertainties <9 %, for the mixed and detailed simulations, and <3 %, for the simulation in which only photons are included. For some target organs and, especially for energies <100 keV, the uncertainties found were larger. The results obtained here have been compared with those obtained by other authors using other MC codes. A good agreement has been found in 80 % of the cases.
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Neutron dosimetry in organs of an adult human phantom using linacs with multileaf collimator in radiotherapy treatments. Med Phys 2012; 39:2854-66. [PMID: 22559658 DOI: 10.1118/1.4704527] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To calculate absorbed doses due to neutrons in 87 organs/tissues for anthropomorphic phantoms, irradiated in position supine (head first into the gantry) with orientations anteroposterior (AP) and right-left (RLAT) with a 18 MV accelerator. Conversion factors from monitor units to μGy per neutron in organs, equivalent doses in organs/tissues, and effective doses, which permit to quantify stochastic risks, are estimated. METHODS MAX06 and FAX06 phantoms were modeled with MCNPX and irradiated with a 18 MV Varian Clinac 2100C/D accelerator whose geometry included a multileaf collimator. Two actual fields of a pelvic treatment were simulated using electron-photon-neutron coupled transport. Absorbed doses due to neutrons were estimated from kerma. Equivalent doses were estimated using the radiation weighting factor corresponding to an average incident neutron energy 0.47 MeV. Statistical uncertainties associated to absorbed doses, as calculated by MCNPX, were also obtained. RESULTS Largest doses were absorbed in shallowest (with respect to the neutron pathway) organs. In μGyMU(-1), values of 2.66 (for penis) and 2.33 (for testes) were found in MAX06, and 1.68 (for breasts), 1.05 (for lenses of eyes), and 0.94 (for sublingual salivary glands) in FAX06, in AP orientation. In RLAT, the largest doses were found for bone tissues (leg) just at the entrance of the beam in the body (right side in our case). Values, in μGyMU(-1), of 1.09 in upper leg bone right spongiosa, for MAX06, and 0.63 in mandible spongiosa, for FAX06, were found. Except for gonads, liver, and stomach wall, equivalent doses found for FAX06 were, in both orientations, higher than for MAX06. Equivalent doses in AP are higher than in RLAT for all organs/tissues other than brain and liver. Effective doses of 12.6 and 4.1 μSvMU(-1) were found for AP and RLAT, respectively. The organs/tissues with larger relative contributions to the effective dose were testes and breasts, in AP, and breasts and red marrow, in RLAT. Equivalent and effective doses obtained for MAX06/FAX06 were smaller (between 2 and 20 times) than those quoted for the mathematical phantoms ADAM/EVA in ICRP-74. CONCLUSIONS The new calculations of conversion coefficients for neutron irradiation in AP and RLAT irradiation geometries show a reduction in the values of effective dose by factors 7 (AP) and 6 (RLAT) with respect to the old data obtained with mathematical phantoms. The existence of tissues or anatomical regions with maximum absorbed doses, such as penis, lens of eyes, fascia (part of connective tissue), etc., organs/tissues that classic mathematical phantoms did not include because they were not considered for the study of stochastic effects, has been revealed. Absorbed doses due to photons, obtained following the same simulation methodology, are larger than those due to neutrons, reaching values 100 times larger as the primary beam is approached. However, for organs far from the treated volume, absorbed photon doses can be up to three times smaller than neutron ones. Calculations using voxel phantoms permitted to know the organ dose conversion coefficients per MU due to secondary neutrons in the complete anatomy of a patient.
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Ambient neutron dose equivalent outside concrete vault rooms for 15 and 18 MV radiotherapy accelerators. RADIATION PROTECTION DOSIMETRY 2012; 148:457-464. [PMID: 21750004 DOI: 10.1093/rpd/ncr208] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this work, the ambient dose equivalent, H*(10), due to neutrons outside three bunkers that house a 15- and a 18-MV Varian Clinac 2100C/D and a 15-MV Elekta Inor clinical linacs, has been calculated. The Monte Carlo code MCNPX (v. 2.5) has been used to simulate the neutron production and transport. The complete geometries including linacs and full installations have been built up according to the specifications of the manufacturers and the planes provided by the corresponding medical physical services of the hospitals where the three linacs operate. Two of these installations, those lodging the Varian linacs, have an entrance door to the bunker while the other one does not, although it has a maze with two bends. Various treatment orientations were simulated in order to establish plausible annual equivalent doses. Specifically anterior-posterior, posterior-anterior, left lateral, right lateral orientations and an additional one with the gantry rotated 30° have been studied. Significant dose rates have been found only behind the walls and the door of the bunker, near the entrance and the console, with a maximum of 12 µSv h(-1). Dose rates per year have been calculated assuming a conservative workload for the three facilities. The higher dose rates in the corresponding control areas were 799 µSv y(-1), in the case of the facility which operates the 15-MV Clinac, 159 µSv y(-1), for that with the 15-MV Elekta, and 21 µSv y(-1) for the facility housing the 18-MV Varian. A comparison with measurements performed in similar installations has been carried out and a reasonable agreement has been found. The results obtained indicate that the neutron contamination does not increase the doses above the legal limits and does not produce a significant enhancement of the dose equivalent calculated. When doses are below the detection limits provided by the measuring devices available today, MCNPX simulation provides an useful method to evaluate neutron dose equivalents based on a detailed description of linac, patient and bunker.
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Neutron dose equivalent and neutron spectra in tissue for clinical linacs operating at 15, 18 and 20 MV. RADIATION PROTECTION DOSIMETRY 2011; 147:498-511. [PMID: 21233098 DOI: 10.1093/rpd/ncq501] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this work, the dose equivalent due to photoneutrons and the neutron spectra in tissue was calculated for various linacs (Varian Clinac 2100C, Elekta Inor, Elekta SL25 and Siemens Mevatron KDS) operating at energies between 15 and 20 MV, using the Monte Carlo code MCNPX (v. 2.5). The dose equivalent in an ICRU tissue phantom has been calculated for anteroposterior treatments with a detailed simulation of the geometry of the linac head and the coupled electron-photon-neutron transport. Neutron spectra at the phantom entrance and at 1-cm depth in the phantom, depth distribution of the neutron fluence in the beam axis and dose distributions outside the beam axis at various depths have also been calculated and compared with previously published results. The differences between the neutron production of the various linacs considered has been analysed. Varian linacs show a larger neutron production than the Elekta and Siemens linacs at the same operating energy. The dose equivalent due to neutrons produced by medical linacs operating at energies >15 MeV is relevant and should not be neglected because of the additional doses that patients can receive.
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Quality control for system count rate performance with scatter in gamma cameras. Phys Med 2011; 28:254-61. [PMID: 21641844 DOI: 10.1016/j.ejmp.2011.05.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Revised: 05/05/2011] [Accepted: 05/09/2011] [Indexed: 11/24/2022] Open
Abstract
We aimed to analyze the optimal conditions to carry out the periodical statistical control tests of the gamma camera count rate performance. First we focused in reproducing the actual R(20) value of the gamma camera response. Second we studied the variability of this parameter in the statistical control test. We performed a reference measurement, which consisted of the determination of the complete curve relating observed and incident count rates, the counting model describing it and the reference R(20). This reference determined the conditions for the statistical control tests and the way to analyze the results obtained. Results from three different gamma cameras were studied. Each gamma camera showed a different behavior and required specific data analysis. The optimal conditions to perform the statistical control test were determined in each case. Our procedure provides the information necessary to correlate the average value of R(20) obtained in the quality control test with the reference one. The critical requirement to perform any statistical control test, that is to have a reduced variability of the control variable, can be fulfilled in this case only for relatively high activities.
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Monte Carlo simulation of the dynamic micro-multileaf collimator of a LINAC Elekta Precise using PENELOPE. Phys Med Biol 2011; 56:3417-31. [DOI: 10.1088/0031-9155/56/11/015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Ant colony algorithm implementation in electron and photon Monte Carlo transport: application to the commissioning of radiosurgery photon beams. Med Phys 2010; 37:3782-90. [PMID: 20831086 DOI: 10.1118/1.3456108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In this work, the authors describe an approach which has been developed to drive the application of different variance-reduction techniques to the Monte Carlo simulation of photon and electron transport in clinical accelerators. METHODS The new approach considers the following techniques: Russian roulette, splitting, a modified version of the directional bremsstrahlung splitting, and the azimuthal particle redistribution. Their application is controlled by an ant colony algorithm based on an importance map. RESULTS The procedure has been applied to radiosurgery beams. Specifically, the authors have calculated depth-dose profiles, off-axis ratios, and output factors, quantities usually considered in the commissioning of these beams. The agreement between Monte Carlo results and the corresponding measurements is within approximately 3%/0.3 mm for the central axis percentage depth dose and the dose profiles. The importance map generated in the calculation can be used to discuss simulation details in the different parts of the geometry in a simple way. The simulation CPU times are comparable to those needed within other approaches common in this field. CONCLUSIONS The new approach is competitive with those previously used in this kind of problems (PSF generation or source models) and has some practical advantages that make it to be a good tool to simulate the radiation transport in problems where the quantities of interest are difficult to obtain because of low statistics.
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Production of negative osmium ions by laser desorption and ionization. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:013301. [PMID: 20113087 DOI: 10.1063/1.3276685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The interest to produce negative osmium ions is manifold in the realm of high-accuracy ion trap experiments: high-resolution nearly Doppler-free laser spectroscopy, antihydrogen formation in its ground state, and contributions to neutrino mass spectrometry. Production of these ions is generally accomplished by sputtering an Os sample with Cs(+) ions at tens of keV. Though this is a well-established method commonly used at accelerators, these kind of sources are quite demanding and tricky to operate. Therefore, the development of a more straightforward and cost effective production scheme will be of benefit for ion trap and other experiments. Such a scheme makes use of desorption and ionization with pulsed lasers and identification of the ions by time-of-flight mass spectrometry. First investigations of negative osmium ion production using a pulsed laser for desorption and ionization and a commercial matrix-assisted laser desorption/ionization time-of-flight system for identification has demonstrated the suitability of this technique. More than 10(3) negative osmium ions per shot were registered after bombarding pure osmium powder with a 5 ns pulse width Nd:yttrium aluminum garnet laser. The limitation in the ion number was imposed by the detection limit of the microchannel plate detector.
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Multiple scattering of 13 and 20 MeV electrons by thin foils: a Monte Carlo study with GEANT, Geant4, and PENELOPE. Med Phys 2009; 36:3964-70. [PMID: 19810469 DOI: 10.1118/1.3183501] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In this work, recent results from experiments and simulations (with EGSnrc) performed by Ross et al. [Med. Phys. 35, 4121-4131 (2008)] on electron scattering by foils of different materials and thicknesses are compared to those obtained using several Monte Carlo codes. METHODS Three codes have been used: GEANT (version 3.21), Geant4 (version 9.1, patch03), and PENELOPE (version 2006). In the case of PENELOPE, mixed and fully detailed simulations have been carried out. RESULTS Transverse dose distributions in air have been obtained in order to compare with measurements. The detailed PENELOPE simulations show excellent agreement with experiment. The calculations performed with GEANT and PENELOPE (mixed) agree with experiment within 3% except for the Be foil. In the case of Geant4, the distributions are 5% narrower compared to the experimental ones, though the agreement is very good for the Be foil. Transverse dose distribution in water obtained with PENELOPE (mixed) is 4% wider than those calculated by Ross et al. using EGSnrc and is 1% narrower than the transverse dose distributions in air, as considered in the experiment. CONCLUSIONS All the codes give a reasonable agreement (within 5%) with the experimental results for all the material and thicknesses studied.
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Monte Carlo simulation using the PENELOPE code with an ant colony algorithm to study MOSFET detectors. Phys Med Biol 2009; 54:6263-76. [DOI: 10.1088/0031-9155/54/20/015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Simple analytical expressions for the dose of point photon sources in homogeneous media. Phys Med Biol 2009. [DOI: 10.1088/0031-9155/54/14/c02] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Study of the formalism used to determine the absorbed dose for low-energy x-ray beams. Phys Med Biol 2008; 53:6963-77. [DOI: 10.1088/0031-9155/53/23/020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Simple analytical expressions for the dose of point photon sources in homogeneous media. Phys Med Biol 2008; 53:6113-28. [DOI: 10.1088/0031-9155/53/21/015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Effect of the multiple scattering of electrons in Monte Carlo simulation of LINACS. Radiother Oncol 2008; 86:104-8. [DOI: 10.1016/j.radonc.2007.11.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Revised: 11/26/2007] [Accepted: 11/26/2007] [Indexed: 10/22/2022]
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Obtaining the intrinsic electron spectrum of linear accelerators using the relation between the current of the bending magnet and the absorbed dose in water. Radiother Oncol 2007; 86:109-13. [PMID: 18160159 DOI: 10.1016/j.radonc.2007.11.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Revised: 11/27/2007] [Accepted: 11/27/2007] [Indexed: 12/01/2022]
Abstract
PURPOSE To present a novel methodology to model the intrinsic electron spectra of a linear accelerator and its situation with respect to the energy window. METHODS The spectra are obtained by fitting the variation of R(50) and the maximum dose rate measured in a water phantom with the bending magnet current. The obtained spectra are verified with a realistic Monte Carlo simulation of the accelerator. RESULTS The intrinsic spectra and their relative position with respect to the energy window of the bending magnet have been obtained for a Siemens Mevatron KDS and an ELEKTA SL20 accelerators. CONCLUSIONS Using this method in the commissioning and scheduled revisions of the accelerator, the tuning of the current of the bending magnet could be done in such a way that both the quality of the beam and the dose rate would reach a better long-term stability.
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