1
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Ezzati AO, Studenski MT, Gohari M. Spatial Mesh-Based Surface Source Model for the Electron Contamination of an 18 MV Photon Beams. J Med Phys 2021; 45:221-225. [PMID: 33953497 PMCID: PMC8074718 DOI: 10.4103/jmp.jmp_29_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 10/14/2020] [Accepted: 11/02/2020] [Indexed: 11/04/2022] Open
Abstract
Background Source modeling is an approach to reduce computational burden in Monte Carlo simulations but at the cost of reduced accuracy. Although this method can be effective, one component of the source model that is exceptionally difficult to model is the electron contamination, a significant contributor to the skin and shallow dose. Aims and Objectives To improve the accuracy for the electron contamination component of the overall source model, we have generated a spatial mesh based surface source model. Methods and Materials The source model is located downstream from the flattening filter and mirror but upstream from the movable jaws. A typical phase space file uses around ten parameters per particle, but this method simplifies this number to five components. By using only the electron distance from the central axis, angles from the central axis and energy, the computational time and disk space required is greatly reduced. Results and Conclusion Despite the simplification in the source model, the electron contamination is still accurate to within 1.5%.
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Affiliation(s)
- Ahad Ollah Ezzati
- Department of Nuclear Physics, Faculty of Physics, University of Tabriz, Tabriz, Iran
| | | | - Masuomeh Gohari
- Department of Nuclear Physics, Faculty of Physics, University of Tabriz, Tabriz, Iran
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2
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Park JI, Lee S, Kim IH, Ye SJ. Artifact-free CT images for electron beam therapy using a patient-specific non metallic shield. Phys Med 2020; 75:92-99. [PMID: 32559651 DOI: 10.1016/j.ejmp.2020.06.001] [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: 12/14/2019] [Revised: 05/10/2020] [Accepted: 06/01/2020] [Indexed: 10/24/2022] Open
Abstract
Patient's CT images taken with metallic shields for radiotherapy suffer from artifacts. Furthermore, the treatment planning system (TPS) has a limitation on accurate dose calculations for high density materials. In this study, a Monte Carlo (MC)-based method was developed to accurately evaluate the dosimetric effect of the metallic shield. Two patients with a commercial tungsten shield of lens and two patients with a custom-made lead shield of lip were chosen to produce their non-metallic dummy shields using 3D scanner and printer. With these dummy shields, we generated artifact-free CT images. The maximum CT number allowed in TPS was assigned to metallic shields. MC simulations with real material information were carried out. In addition, clinically relevant dose-volumetric parameters were calculated for the comparison between MC and TPS. Relative dosimetry was performed using radiochromic films. The dose reductions below metallic structures were shown on MC dose distributions, but not evident on TPS dose distributions. The differences in dose-volumetric parameters of PTV between TPS and MC for eye shield cases were not clearly shown. However, the mean dose of lens from TPS and MC was different. The MC results were in superior agreement with measured data in relative dosimetry. The lens dose could be overestimated by TPS. The differences in dose-volumetric parameters of PTV between TPS and MC were generally larger in lip cases than in eye cases. The developed method is useful in predicting the realistic dose distributions around the organs blocked by the metallic shields.
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Affiliation(s)
- Jong In Park
- Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, South Korea.
| | - Sangmin Lee
- Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, South Korea
| | - Il Han Kim
- Department of Radiation Oncology, Seoul National University Hospital, Seoul, South Korea
| | - Sung-Joon Ye
- Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, South Korea; Department of Radiation Oncology, Seoul National University Hospital, Seoul, South Korea; Robotics Research Laboratory for Extreme Environment, Advanced Institutes of Convergence Technology, Seoul National University, Suwon, Gyeonggi-do, South Korea
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3
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Efendi MA, Funsian A, Chittrakarn T, Bhongsuwan T. Monte Carlo simulation using PRIMO code as a tool for checking the credibility of commissioning and quality assurance of 6 MV TrueBeam STx varian LINAC. Rep Pract Oncol Radiother 2020; 25:125-132. [PMID: 31920464 DOI: 10.1016/j.rpor.2019.12.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Revised: 10/03/2019] [Accepted: 12/18/2019] [Indexed: 11/26/2022] Open
Abstract
Aim To validate and implement Monte Carlo simulation using PRIMO code as a tool for checking the credibility of measurements in LINAC initial commissioning and routine Quality Assurance (QA). Relative and absolute doses of 6 MV photon beam from TrueBeam STx Varian Linear Accelerator (LINAC) were simulated and validated with experimental measurement, Analytical Anisotropic Algorithm (AAA) calculation, and golden beam. Methods and Materials Varian phase-space files were imported to the PRIMO code and four blocks of jaws were simulated to determine the field size of the photon beam. Water phantom was modeled in the PRIMO code with water equivalent density. Golden beam data, experimental measurement, and AAA calculation results were imported to PRIMO code for gamma comparison. Results PRIMO simulations of Percentage Depth Dose (PDD) and in-plane beam profiles had good agreement with experimental measurements, AAA calculations and golden beam. However, PRIMO simulations of cross-plane beam profiles have a better agreement with AAA calculation and golden beam than the experimental measurement. Furthermore, PRIMO simulations of absolute dose agreed well with experimental results with ±0.8% uncertainty. Conclusion The PRIMO code has good accuracy and is appropriate for use as a tool to check the credibility of beam scanning and output measurement in initial commissioning and routine QA.
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Affiliation(s)
- M Arif Efendi
- Department of Radiology, Faculty of Medicine, Prince of Songkla University, Hatyai, Thailand
| | - Amporn Funsian
- Department of Radiology, Faculty of Medicine, Prince of Songkla University, Hatyai, Thailand
| | - Thawat Chittrakarn
- Department of Physics, Faculty of Science, Prince of Songkla University, Hatyai, Thailand
| | - Tripob Bhongsuwan
- Department of Physics, Faculty of Science, Prince of Songkla University, Hatyai, Thailand
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4
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Ma CMC, Chetty IJ, Deng J, Faddegon B, Jiang SB, Li J, Seuntjens J, Siebers JV, Traneus E. Beam modeling and beam model commissioning for Monte Carlo dose calculation-based radiation therapy treatment planning: Report of AAPM Task Group 157. Med Phys 2019; 47:e1-e18. [PMID: 31679157 DOI: 10.1002/mp.13898] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 10/01/2019] [Accepted: 10/18/2019] [Indexed: 11/07/2022] Open
Abstract
Dose calculation plays an important role in the accuracy of radiotherapy treatment planning and beam delivery. The Monte Carlo (MC) method is capable of achieving the highest accuracy in radiotherapy dose calculation and has been implemented in many commercial systems for radiotherapy treatment planning. The objective of this task group was to assist clinical physicists with the potentially complex task of acceptance testing and commissioning MC-based treatment planning systems (TPS) for photon and electron beam dose calculations. This report provides an overview on the general approach of clinical implementation and testing of MC-based TPS with a specific focus on models of clinical photon and electron beams. Different types of beam models are described including those that utilize MC simulation of the treatment head and those that rely on analytical methods and measurements. The trade-off between accuracy and efficiency in the various source-modeling approaches is discussed together with guidelines for acceptance testing of MC-based TPS from the clinical standpoint. Specific recommendations are given on methods and practical procedures to commission clinical beam models for MC-based TPS.
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Affiliation(s)
- Chang Ming Charlie Ma
- Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA, 19111, USA
| | - Indrin J Chetty
- Radiation Oncology Department, Henry Ford Health System, Detroit, MI, 48188, USA
| | - Jun Deng
- Department of Therapeutic Radiology, Yale University, New Haven, CT, 06032, USA
| | - Bruce Faddegon
- Department of Radiation Oncology, UCSF, San Francisco, CA, 94143, USA
| | - Steve B Jiang
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | | | - Jan Seuntjens
- Medical Physics Unit, McGill University, Montreal, QC, H4A 3J1, Canada
| | - Jeffrey V Siebers
- Department of Radiation Oncology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Erik Traneus
- RaySearch Laboratories AB, SE-103 65, Stockholm, Sweden
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5
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Garnier N, Amblard R, Villeneuve R, Haykal R, Ortholan C, Colin P, Gérard A, Belhomme S, Mady F, Benabdesselam M, Serrano B. Detectors assessment for stereotactic radiosurgery with cones. J Appl Clin Med Phys 2018; 19:88-98. [PMID: 30216702 PMCID: PMC6236831 DOI: 10.1002/acm2.12449] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 08/06/2018] [Accepted: 08/16/2018] [Indexed: 12/03/2022] Open
Abstract
The purpose of this work is to assess eight detectors performance for output factor (OF), percent depth dose (PDD), and beam profiles in a 6‐MV Clinac stereotactic radiosurgery mode for cone irradiation using Monte Carlo simulation as reference. Cones with diameters comprised between 30 and 4 mm have been studied. The evaluated detectors were ionization chambers: pinpoint and pinpoint 3D, diodes: SRS, P and E, Edge, MicroDiamond and EBT3 radiochromic films. The results showed that pinpoints underestimate OF up to −2.3% for cone diameters ≥10 mm and down to −12% for smaller cones. Both nonshielded (SRS and E) and shielded diodes (P and Edge) overestimate the OF respectively up to 3.3% and 5.2% for cone diameters ≥10 mm and in both cases more than 7% for smaller cones. MicroDiamond slightly overestimates the OF, 3.7% for all the cones and EBT3 film is the closest to Monte Carlo with maximum difference of ±1% whatever the cone size is. For the profiles and the PDD, particularly for the small cones, the size of the detector predominates. All diodes and EBT3 agree with the simulation within ±0.2 mm for beam profiles determination. For PDD curve all the active detectors response agree with simulation up to 1% for all the cones. EBT3 is the more accurate detector for beam profiles and OF determinations of stereotactic cones but it is restrictive to use. Due to respectively inappropriate size of the sensitive volume and composition, pinpoints and diodes do not seem appropriate without OF corrective factors below 10 mm diameter cone. MicroDiamond appears to be the best detector for OF determination regardless all cones. For off‐axis measurements, the size of the detector predominates and for PDD all detectors give promising results.
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Affiliation(s)
- Nicolas Garnier
- Medical Physics Department, Princess Grace Hospital Center, Monaco, Monaco.,Institut de Physique de Nice, Côte d'Azur University, Parc Valrose, Nice, France
| | - Régis Amblard
- Medical Physics Department, Princess Grace Hospital Center, Monaco, Monaco
| | - Rémy Villeneuve
- Medical Physics Department, Princess Grace Hospital Center, Monaco, Monaco
| | - Rodolphe Haykal
- Medical Physics Department, Princess Grace Hospital Center, Monaco, Monaco
| | - Cécile Ortholan
- Radiotherapy Department, Princess Grace Hospital Center, Monaco, Monaco
| | - Philippe Colin
- Radiotherapy Department, Princess Grace Hospital Center, Monaco, Monaco
| | - Anaïs Gérard
- Medical Physics Department, Centre Antoine Lacassagne, Nice, France
| | - Sarah Belhomme
- Medical Physics Department, Institut Bergonié, Bordeaux, France
| | - Franck Mady
- Institut de Physique de Nice, Côte d'Azur University, Parc Valrose, Nice, France
| | - Mourad Benabdesselam
- Institut de Physique de Nice, Côte d'Azur University, Parc Valrose, Nice, France
| | - Benjamin Serrano
- Medical Physics Department, Princess Grace Hospital Center, Monaco, Monaco
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Dowlatabadi H, Mowlavi A, Ghorbani M, Mohammadi S, Akbari F. Benchmarking of Siemens Linac in Electron Modes: 8-14 MeV Electron Beams. J Biomed Phys Eng 2018; 8:157-166. [PMID: 29951442 PMCID: PMC6015647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 07/27/2017] [Indexed: 11/23/2022]
Abstract
BACKGROUND Radiation therapy using electron beams is a promising method due to its physical dose distribution. Monte Carlo (MC) code is the best and most accurate technique for forespeaking the distribution of dose in radiation treatment of patients. MATERIAL AND METHODS We report an MC simulation of a linac head and depth dose on central axis, along with profile calculations. The purpose of the present research is to carefully analyze the application of MC methods for the calculation of dosimetric parameters for electron beams with energies of 8-14 MeV at a Siemens Primus linac. The principal components of the linac head were simulated using MCNPX code for different applicators. RESULTS The consequences of measurements and simulations revealed a good agreement. Gamma index values were below 1 for most points, for all energy values and all applicators in percent depth dose and dose profile computations. A number of states exhibited rather large gamma indices; these points were located at the tail of the percent depth dose graph; these points were less used in in radiotherapy. In the dose profile graph, gamma indices of most parts were below 1. The discrepancies between the simulation results and measurements in terms of Zmax, R90, R80 and R50 were insignificant. The results of Monte Carlo simulations showed a good agreement with the measurements. CONCLUSION The software can be used for simulating electron modes of a Siemens Primus linac when direct experimental measurements are not feasible.
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Affiliation(s)
- H. Dowlatabadi
- Physics Department, School of Sciences, Payame Noor University of Mashhad, Mashhad, Iran
| | - A.A. Mowlavi
- Physics Department, School of Sciences, Hakim Sabzevari University, Sabzevar, Iran
,ICTP, Associate Federation Scheme, Medical Physics Field, Trieste, Italy
| | - M. Ghorbani
- Biomedical Engineering and Medical Physics Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - S. Mohammadi
- Physics Department, School of Sciences, Payame Noor University of Mashhad, Mashhad, Iran
| | - F. Akbari
- Medical Physics Department, Reza Radiation Oncology Center, Mashhad, Iran
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7
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Nevelsky A, Borzov E, Daniel S, Bar-Deroma R. Room scatter effects in Total Skin Electron Irradiation: Monte Carlo simulation study. J Appl Clin Med Phys 2017; 18:196-201. [PMID: 28291915 PMCID: PMC5689893 DOI: 10.1002/acm2.12039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 11/09/2016] [Accepted: 11/28/2016] [Indexed: 11/10/2022] Open
Abstract
Purpose Total Skin Electron Irradiation (TSEI) is a complex technique which usually involves the use of large electron fields and the dual‐field approach. In this situation, many electrons scattered from the treatment room floor are produced. However, no investigations of the effect of scattered electrons in TSEI treatments have been reported. The purpose of this work was to study the contribution of floor scattered electrons to skin dose during TSEI treatment using Monte Carlo (MC) simulations. Methods All MC simulations were performed with the EGSnrc code. Influence of beam energy, dual‐field angle, and floor material on the contribution of floor scatter was investigated. Spectrum of the scattered electrons was calculated. Measurements of dose profile were performed in order to verify MC calculations. Results Floor scatter dependency on the floor material was observed (at 20 cm from the floor, scatter contribution was about 21%, 18%, 15%, and 12% for iron, concrete, PVC, and water, respectively). Although total dose profiles exhibited slight variation as functions of beam energy and dual‐field angle, no dependence of the floor scatter contribution on the beam energy or dual‐field angle was found. The spectrum of the scattered electrons was almost uniform between a few hundred KeV to 4 MeV, and then decreased linearly to 6 MeV. Conclusions For the TSEI technique, dose contribution due to the electrons scattered from the room floor may be clinically significant and should be taken into account during design and commissioning phases. MC calculations can be used for this task.
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Affiliation(s)
| | - Egor Borzov
- Division of Oncology, Rambam Health Care Campus, Haifa, Israel
| | - Shahar Daniel
- Division of Oncology, Rambam Health Care Campus, Haifa, Israel
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8
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Molazadeh M, Zeinali A, Robatjazi M, Shirazi A, Geraily G. Dosimetric characteristics of LinaTech DMLC H multi leaf collimator: Monte Carlo simulation and experimental study. J Appl Clin Med Phys 2017; 18:113-124. [PMID: 28300380 PMCID: PMC5689964 DOI: 10.1002/acm2.12055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 01/08/2017] [Accepted: 01/10/2017] [Indexed: 11/09/2022] Open
Abstract
This study evaluated the basic dosimetric characteristics of a Dynamic Multi Leaf Collimator (DMLC) using a diode detector and film measurements for Intensity Modulated Radiation Therapy Quality Assurance (IMRT QA). The EGSnrc Monte Carlo (MC) simulation system was used for the determination of MLC characteristics. Radiation transmission and abutting leaf leakage relevant to the LinaTech DMLC H were measured using an EDGE detector and EBT3 film. In this study, the BEAMnrc simulation code was used for modeling. The head of Siemens PRIMUS linac (6 MV) with external DMLC H was entered into a BEAMnrc Monte Carlo model using practical dosimetry data. Leaf material density, as well as interleaf and abutting air gaps were determined according to the computed and measured dose profiles. The IMRT QA field was used to evaluate the dose distribution of the simulated DMLC H. According to measurements taken with the EDGE detector and film, the total average measured leakage was 1.60 ± 0.03% and 1.57 ± 0.05%, respectively. For these measurements, abutting leaf transmission was 54.35 ± 1.85% and 53.08 ± 2.05%, respectively. To adapt the simulated leaf dose profiles with measurements, leaf material density, interleaf and abutting air gaps were adjusted to 18 g/cm3, 0.008 cm and 0.108 cm, respectively. Thus, the total average leakage was estimated to be about 1.59 ± 0.02%. The step‐and‐shoot IMRT was implemented and 94% agreement was achieved between the film and MC, using 3%‐3 mm gamma criteria. The results of this study showed that the dosimetric characteristics of DMLC H satisfied international standards.
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Affiliation(s)
- Mikaeil Molazadeh
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ahad Zeinali
- Department of Medical Physics, Faculty of Medicine, Urmia University of Medical Science, Nazloo Campus, Urmia, Iran
| | - Mostafa Robatjazi
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Alireza Shirazi
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ghazale Geraily
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
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Park JI, Ha SW, Kim JI, Lee H, Lee J, Kim IH, Ye SJ. Design and evaluation of electron beam energy degraders for breast boost irradiation. Radiat Oncol 2016; 11:112. [PMID: 27580698 PMCID: PMC5007734 DOI: 10.1186/s13014-016-0686-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 08/19/2016] [Indexed: 11/25/2022] Open
Abstract
Background For breast cancer patients who require electron boost energies between 6 and 9 MeV, an energy degraders (ED) in the 9 MeV beamline was specially designed and manufactured to increase the skin dose of 6 MeV and to reduce the penetration depth of 9 MeV beams. Methods We used Monte Carlo (MC) techniques as a guide in the design of ED for use with linear accelerators. In order to satisfy percent depth dose (PDD) characteristics and dose profile uniformity in water, the shape and thickness of Lucite® ED in the 9 MeV beamline was iteratively optimized and then manufactured. The ED geometry consists of a truncated cone attached on top of a plane plate, with total central thickness of 1.0 cm. The ED was placed on the lower most scraper of the electron applicator. The PDDs, profiles, and output factors were measured in water to validate the MC-based design. Results Skin doses with the EDs increased by 8–9 %, compared to those of the 9 MeV beam. The outputs with the EDs were 0.882 and 0.972 for 10 × 10 and 15 × 15 cm2 cones, respectively, as compared to that of a conventional 9 MeV beam for a 10 × 10 cm2 cone. The X-ray contamination remained less than 1.5 %. In-vivo measurements were also performed for three breast boost patients and showed close agreement with expected values. Conclusions The optimally designed ED in the 9 MeV beamline provides breast conserving patients with a new energy option of 7 MeV for boost of the shallow tumor bed. It would be an alternative to bolus and thus eliminate inconvenience and concern about the daily variation of bolus setup.
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Affiliation(s)
- Jong In Park
- Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, 151-742, Korea.,Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.,Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea
| | - Sung Whan Ha
- Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.,Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea
| | - Jung-In Kim
- Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.,Advanced Institutes of Convergence Technology, Seoul National University, Suwon, Korea
| | - Hyunseok Lee
- Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, 151-742, Korea.,Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea
| | - Jaegi Lee
- Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, 151-742, Korea.,Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea
| | - Il Han Kim
- Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.,Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea
| | - Sung-Joon Ye
- Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, 151-742, Korea. .,Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea. .,Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea. .,Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea. .,Advanced Institutes of Convergence Technology, Seoul National University, Suwon, Korea.
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Nevelsky A, Borzov E, Daniel S, Bar-Deroma R. Validation of total skin electron irradiation (TSEI) technique dosimetry data by Monte Carlo simulation. J Appl Clin Med Phys 2016; 17:418-429. [PMID: 27455502 PMCID: PMC5690047 DOI: 10.1120/jacmp.v17i4.6230] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Revised: 02/10/2016] [Accepted: 02/04/2016] [Indexed: 12/01/2022] Open
Abstract
Total skin electron irradiation (TSEI) is a complex technique which requires many nonstandard measurements and dosimetric procedures. The purpose of this work was to validate measured dosimetry data by Monte Carlo (MC) simulations using EGSnrc‐based codes (BEAMnrc and DOSXYZnrc). Our MC simulations consisted of two major steps. In the first step, the incident electron beam parameters (energy spectrum, FWHM, mean angular spread) were adjusted to match the measured data (PDD and profile) at SSD=100 cm for an open field. In the second step, these parameters were used to calculate dose distributions at the treatment distance of 400 cm. MC simulations of dose distributions from single and dual fields at the treatment distance were performed in a water phantom. Dose distribution from the full treatment with six dual fields was simulated in a CT‐based anthropomorphic phantom. MC calculations were compared to the available set of measurements used in clinical practice. For one direct field, MC calculated PDDs agreed within 3%/1 mm with the measurements, and lateral profiles agreed within 3% with the measured data. For the OF, the measured and calculated results were within 2% agreement. The optimal angle of 17° was confirmed for the dual field setup. Dose distribution from the full treatment with six dual fields was simulated in a CT‐based anthropomorphic phantom. The MC‐calculated multiplication factor (B12‐factor), which relates the skin dose for the whole treatment to the dose from one calibration field, for setups with and without degrader was 2.9 and 2.8, respectively. The measured B12‐factor was 2.8 for both setups. The difference between calculated and measured values was within 3.5%. It was found that a degrader provides more homogeneous dose distribution. The measured X‐ray contamination for the full treatment was 0.4%; this is compared to the 0.5% X‐ray contamination obtained with the MC calculation. Feasibility of MC simulation in an anthropomorphic phantom for a full TSEI treatment was proved and is reported for the first time in the literature. The results of our MC calculations were found to be in general agreement with the measurements, providing a promising tool for further studies of dose distribution calculations in TSEI. PACS number(s): 87.10. Rt, 87.55.K, 87.55.ne
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11
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Rodrigues A, Sawkey D, Yin FF, Wu Q. A Monte Carlo simulation framework for electron beam dose calculations using Varian phase space files for TrueBeam Linacs. Med Phys 2015; 42:2389-403. [DOI: 10.1118/1.4916896] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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12
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Herranz E, Herraiz JL, Ibáñez P, Pérez-Liva M, Puebla R, Cal-González J, Guerra P, Rodríguez R, Illana C, Udías JM. Phase space determination from measured dose data for intraoperative electron radiation therapy. Phys Med Biol 2015; 60:375-401. [PMID: 25503853 DOI: 10.1088/0031-9155/60/1/375] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A procedure to characterize beams of a medical linear accelerator for their use in Monte Carlo (MC) dose calculations for intraoperative electron radiation therapy (IOERT) is presented. The procedure relies on dose measurements in homogeneous media as input, avoiding the need for detailed simulations of the accelerator head. An iterative algorithm (EM-ML) has been employed to extract the relevant details of the phase space (PHSP) of the particles coming from the accelerator, such as energy spectra, spatial distribution and angle of emission of particles. The algorithm can use pre-computed dose volumes in water and/or air, so that the machine-specific tuning with actual data can be performed in a few minutes. To test the procedure, MC simulations of a linear accelerator with typical IOERT applicators and energies, have been performed and taken as reference. A solution PHSP derived from the dose produced by the simulated accelerator has been compared to the reference PHSP. Further, dose delivered by the simulated accelerator for setups not included in the fit of the PHSP were compared to the ones derived from the solution PHSP. The results show that it is possible to derive from dose measurements PHSP accurate for IOERT MC dose estimations.
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Affiliation(s)
- E Herranz
- Grupo de Física Nuclear, Dpto. Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, CEI Moncloa, Madrid E-28040, Spain
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13
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Herranz E, Herraiz JL, Ibáñez P, Pérez-Liva M, Puebla R, Cal-González J, Guerra P, Rodríguez R, Illana C, Udías JM. Phase space determination from measured dose data for intraoperative electron radiation therapy. Phys Med Biol 2014. [DOI: https://doi.org/10.1088/0031-9155/60/1/375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Ojala J, Hyödynmaa S, Barańczyk R, Góra E, Waligórski M. Performance of two commercial electron beam algorithms over regions close to the lung–mediastinum interface, against Monte Carlo simulation and point dosimetry in virtual and anthropomorphic phantoms. Phys Med 2014; 30:147-54. [DOI: 10.1016/j.ejmp.2013.04.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 03/06/2013] [Accepted: 04/25/2013] [Indexed: 11/25/2022] Open
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Park JM, Kim JI, Heon Choi C, Chie EK, Kim IH, Ye SJ. Photon energy-modulated radiotherapy: Monte Carlo simulation and treatment planning study. Med Phys 2013; 39:1265-77. [PMID: 22380358 DOI: 10.1118/1.3682172] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
PURPOSE To demonstrate the feasibility of photon energy-modulated radiotherapy during beam-on time. METHODS A cylindrical device made of aluminum was conceptually proposed as an energy modulator. The frame of the device was connected with 20 tubes through which mercury could be injected or drained to adjust the thickness of mercury along the beam axis. In Monte Carlo (MC) simulations, a flattening filter of 6 or 10 MV linac was replaced with the device. The thickness of mercury inside the device varied from 0 to 40 mm at the field sizes of 5 × 5 cm(2) (FS5), 10 × 10 cm(2) (FS10), and 20 × 20 cm(2) (FS20). At least 5 billion histories were followed for each simulation to create phase space files at 100 cm source to surface distance (SSD). In-water beam data were acquired by additional MC simulations using the above phase space files. A treatment planning system (TPS) was commissioned to generate a virtual machine using the MC-generated beam data. Intensity modulated radiation therapy (IMRT) plans for six clinical cases were generated using conventional 6 MV, 6 MV flattening filter free, and energy-modulated photon beams of the virtual machine. RESULTS As increasing the thickness of mercury, Percentage depth doses (PDD) of modulated 6 and 10 MV after the depth of dose maximum were continuously increased. The amount of PDD increase at the depth of 10 and 20 cm for modulated 6 MV was 4.8% and 5.2% at FS5, 3.9% and 5.0% at FS10 and 3.2%-4.9% at FS20 as increasing the thickness of mercury from 0 to 20 mm. The same for modulated 10 MV was 4.5% and 5.0% at FS5, 3.8% and 4.7% at FS10 and 4.1% and 4.8% at FS20 as increasing the thickness of mercury from 0 to 25 mm. The outputs of modulated 6 MV with 20 mm mercury and of modulated 10 MV with 25 mm mercury were reduced into 30%, and 56% of conventional linac, respectively. The energy-modulated IMRT plans had less integral doses than 6 MV IMRT or 6 MV flattening filter free plans for tumors located in the periphery while maintaining the similar quality of target coverage, homogeneity, and conformity. CONCLUSIONS The MC study for the designed energy modulator demonstrated the feasibility of energy-modulated photon beams available during beam-on time. The planning study showed an advantage of energy-and intensity modulated radiotherapy in terms of integral dose without sacrificing any quality of IMRT plan.
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Borges C, Zarza-Moreno M, Heath E, Teixeira N, Vaz P. Monte Carlo modeling and simulations of the High Definition (HD120) micro MLC and validation against measurements for a 6 MV beam. Med Phys 2012; 39:415-23. [PMID: 22225311 DOI: 10.1118/1.3671935] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The most recent Varian(®) micro multileaf collimator (MLC), the High Definition (HD120) MLC, was modeled using the BEAMNRC Monte Carlo code. This model was incorporated into a Varian medical linear accelerator, for a 6 MV beam, in static and dynamic mode. The model was validated by comparing simulated profiles with measurements. METHODS The Varian(®) Trilogy(®) (2300C/D) accelerator model was accurately implemented using the state-of-the-art Monte Carlo simulation program BEAMNRC and validated against off-axis and depth dose profiles measured using ionization chambers, by adjusting the energy and the full width at half maximum (FWHM) of the initial electron beam. The HD120 MLC was modeled by developing a new BEAMNRC component module (CM), designated HDMLC, adapting the available DYNVMLC CM and incorporating the specific characteristics of this new micro MLC. The leaf dimensions were provided by the manufacturer. The geometry was visualized by tracing particles through the CM and recording their position when a leaf boundary is crossed. The leaf material density and abutting air gap between leaves were adjusted in order to obtain a good agreement between the simulated leakage profiles and EBT2 film measurements performed in a solid water phantom. To validate the HDMLC implementation, additional MLC static patterns were also simulated and compared to additional measurements. Furthermore, the ability to simulate dynamic MLC fields was implemented in the HDMLC CM. The simulation results of these fields were compared with EBT2 film measurements performed in a solid water phantom. RESULTS Overall, the discrepancies, with and without MLC, between the opened field simulations and the measurements using ionization chambers in a water phantom, for the off-axis profiles are below 2% and in depth-dose profiles are below 2% after the maximum dose depth and below 4% in the build-up region. On the conditions of these simulations, this tungsten-based MLC has a density of 18.7 g cm(- 3) and an overall leakage of about 1.1 ± 0.03%. The discrepancies between the film measured and simulated closed and blocked fields are below 2% and 8%, respectively. Other measurements were performed for alternated leaf patterns and the agreement is satisfactory (to within 4%). The dynamic mode for this MLC was implemented and the discrepancies between film measurements and simulations are within 4%. CONCLUSIONS The Varian(®) Trilogy(®) (2300 C/D) linear accelerator including the HD120 MLC was successfully modeled and simulated using the Monte Carlo BEAMNRC code by developing an independent CM, the HDMLC CM, either in static and dynamic modes.
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Affiliation(s)
- C Borges
- MedicalConsult SA, Campo Grande n°56 8A 1700-093 Lisboa, Portugal.
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17
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Ali OA, Willemse CA, Shaw W, O'Reilly FHJ, du Plessis FCP. Monte Carlo electron source model validation for an Elekta Precise linac. Med Phys 2011; 38:2366-73. [DOI: 10.1118/1.3570579] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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18
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O'Shea TP, Sawkey DL, Foley MJ, Faddegon BA. Monte Carlo commissioning of clinical electron beams using large field measurements. Phys Med Biol 2010; 55:4083-105. [DOI: 10.1088/0031-9155/55/14/009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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19
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Chow JCL, Jiang R. Monte Carlo calculation of monitor unit for electron arc therapy. Med Phys 2010; 37:1571-8. [PMID: 20443478 DOI: 10.1118/1.3359819] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Monitor unit (MU) calculations for electron are therapy were carried out using Monte Carlo simulations and verified by measurements. Variations in the dwell factor (DF), source-to-surface distance (SSD), and treatment are angle (a) were studied. Moreover, the possibility of measuring the DF, which requires gantry rotation, using a solid water rectangular, instead of cylindrical, phantom was investigated. METHODS A phase space file based on the 9 MeV electron beam with rectangular cutout (physical size = 2.6 x 21 cm2) attached to the block tray holder of a Varian 21 EX linear accelerator (linac) was generated using the EGSnrc-based Monte Carlo code and verified by measurement. The relative output factor (ROF), SSD offset, and DF, needed in the MU calculation, were determined using measurements and Monte Carlo simulations. An ionization chamber, a radiographic film, a solid water rectangular phantom, and a cylindrical phantom made of polystyrene were used in dosimetry measurements. RESULTS Percentage deviations of ROF, SSD offset, and DF between measured and Monte Carlo results were 1.2%, 0.18%, and 1.5%, respectively. It was found that the DF decreased with an increase in a, and such a decrease in DF was more significant in the a range of 0 degrees-60 degrees than 60 degrees-120 degrees. Moreover, for a fixed a, the DF increased with an increase in SSD. Comparing the DF determined using the rectangular and cylindrical phantom through measurements and Monte Carlo simulations, it was found that the DF determined by the rectangular phantom agreed well with that by the cylindrical one within +/- 1.2%. It shows that a simple setup of a solid water rectangular phantom was sufficient to replace the cylindrical phantom using our specific cutout to determine the DF associated with the electron arc. CONCLUSIONS By verifying using dosimetry measurements, Monte Carlo simulations proved to be an alternative way to perform MU calculations effectively for electron are therapy. Since Monte Carlo simulations can generate a precalculated database of ROF, SSD offset, and DF for the MU calculation, with a reduction in human effort and linac beam-on time, it is recommended that Monte Carlo simulations be partially or completely integrated into the commissioning of electron are therapy.
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Affiliation(s)
- James C L Chow
- Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto, Ontario M5G 2M9, Canada.
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20
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Gajewski R. An enhanced sector integration model for output and dose distribution calculation of irregular concave shaped electron beams. Med Phys 2009; 36:2966-75. [PMID: 19673195 DOI: 10.1118/1.3148583] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A comprehensive method of output factor and dose distribution calculation for electron beams has been developed. It allows one to calculate the output factors and isodose distributions in water of arbitrary shaped electron fields with excellent accuracy even for the cases of concaved, small, elongated beams, and extended source to surface distances (SSDs). The method requires two sets of data: Depth dose distribution per monitor unit for circular cutouts and depth dose distributions per monitor unit for circular blocks (plugs), both for two SSDs, one reference of 100 cm and second extended one. The method has been extensively tested using a combination of different irregular cutouts and various SSDs for the 6 and 9 MeV electron beams. The calculated values agreed with the measured data well within 1% for output factors and below 1 for gamma (gamma test) for isodose distributions. The computer program has been developed to facilitate the method for practical application. The method has been used for almost 8 years considerably cutting workload in the department.
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Affiliation(s)
- Romuald Gajewski
- Department of Medical Physics, Sydney West Cancer Network, Westmead, New South Wales 2145, Australia.
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Weinberg R, Antolak JA, Starkschall G, Kudchadker RJ, White RA, Hogstrom KR. Influence of source parameters on large-field electron beam profiles calculated using Monte Carlo methods. Phys Med Biol 2008; 54:105-16. [PMID: 19075360 DOI: 10.1088/0031-9155/54/1/007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The purpose of this paper was to study the source model for a Monte Carlo simulation of electron beams from a medical linear accelerator. In a prior study, a non-divergent Gaussian source with a full-width at half-maximum (FWHM) of 0.15 cm was successful in predicting relative dose distributions for electron beams with applicators. However, for large fields with the applicator removed, discrepancies were found between measured and calculated profiles, particularly in the shoulder region. In this work, the source was changed to a divergent Gaussian spatial distribution and the FWHM parameter was varied to produce better agreement with measured data. The influence of the FWHM source parameter on profiles was observed at multiple locations in the simulation geometry including in-air fluence profiles at a 95 cm source-to-surface distance (SSD), percent depth dose profiles and off-axis profiles (OARs) in a water phantom for two SSDs, 80 and 100 cm. For a 6 MeV 40 x 40 cm(2) OAR profile, discrepancies in the shoulder region were reduced from 15% to 4% using a FWHM value of 0.45 cm. The optimal FWHM values for the other energies were 0.45 cm for 9 MeV, 0.22 for 12 MeV, 0.25 for 16 MeV and 0.2 cm for 20 MeV. Although this range of values was larger than measured focal spot sizes reported by other researchers, using the increased FWHM values improved the fit at most locations in the simulation geometry, giving confidence that the model could be used with a variety of SSDs and field sizes.
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Affiliation(s)
- Rebecca Weinberg
- Department of Radiation Physics, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA.
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22
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Das IJ, Cheng CW, Watts RJ, Ahnesjö A, Gibbons J, Li XA, Lowenstein J, Mitra RK, Simon WE, Zhu TC. Accelerator beam data commissioning equipment and procedures: Report of the TG-106 of the Therapy Physics Committee of the AAPM. Med Phys 2008; 35:4186-215. [PMID: 18841871 DOI: 10.1118/1.2969070] [Citation(s) in RCA: 302] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Indra J Das
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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Al-Yahya K, Verhaegen F, Seuntjens J. Design and dosimetry of a few leaf electron collimator for energy modulated electron therapy. Med Phys 2008; 34:4782-91. [PMID: 18196806 DOI: 10.1118/1.2795827] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Despite the capability of energy modulated electron therapy (EMET) to achieve highly conformal dose distributions in superficial targets it has not been widely implemented due to problems inherent in electron beam radiotherapy such as planning dosimetry accuracy, and verification as well as a lack of systems for automated delivery. In previous work we proposed a novel technique to deliver EMET using an automated "few leaf electron collimator" (FLEC) that consists of four motor-driven leaves fit in a standard clinical electron beam applicator. Integrated with a Monte Carlo based optimization algorithm that utilizes patient-specific dose kernels, a treatment delivery was incorporated within the linear accelerator operation. The FLEC was envisioned to work as an accessory tool added to the clinical accelerator. In this article the design and construction of the FLEC prototype that match our compact design goals are presented. It is controlled using an in-house developed EMET controller. The structure of the software and the hardware characteristics of the EMET controller are demonstrated. Using a parallel plate ionization chamber, output measurements were obtained to validate the Monte Carlo calculations for a range of fields with different energies and sizes. Further verifications were also performed for comparing 1-D and 2-D dose distributions using energy independent radiochromic films. Comparisons between Monte Carlo calculations and measurements of complex intensity map deliveries show an overall agreement to within +/- 3%. This work confirms our design objectives of the FLEC that allow for automated delivery of EMET. Furthermore, the Monte Carlo dose calculation engine required for EMET planning was validated. The result supports the potential of the prototype FLEC for the planning and delivery of EMET.
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Affiliation(s)
- Khalid Al-Yahya
- Health Sciences Center Saad Specialist Hospital, Al-Khobar, Saudi Arabia 31952
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Fragoso M, Pillai S, Solberg TD, Chetty IJ. Experimental verification and clinical implementation of a commercial Monte Carlo electron beam dose calculation algorithm. Med Phys 2008; 35:1028-38. [DOI: 10.1118/1.2839098] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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25
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Klein EE, Vicic M, Ma CM, Low DA, Drzymala RE. Validation of calculations for electrons modulated with conventional photon multileaf collimators. Phys Med Biol 2008; 53:1183-208. [PMID: 18296757 DOI: 10.1088/0031-9155/53/5/003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Treating shallow tumors with a homogeneous dose while simultaneously minimizing the dose to distal critical organs remains a challenge in radiotherapy. One promising approach is modulated electron radiotherapy (MERT). Due to the scattering properties of electron beams, the commercially provided secondary and tertiary photon collimation systems are not conducive for electron beam delivery when standard source-to-surface distances are used. Also, commercial treatment planning systems may not accurately model electron-beam dose distributions when collimated without the standard applicators. However, by using the photon multileaf collimators (MLCs) to create segments to modulate electron beams, the quality of superficial tumor dose distributions may improve substantially. The purpose of this study is to develop and evaluate calculations for the narrow segments needed to modulate megavoltage electron beams using photon beam multileaf collimators. Modulated electron radiotherapy (MERT) will be performed with a conventional linear accelerator equipped with a 120 leaf MLC for 6-20 MeV electron beam energies. To provide a sharp penumbra, segments were delivered with short SSDs (70-85 cm). Segment widths (SW) ranging from 1 to 10 cm were configured for delivery and planning, using BEAMnrc Monte Carlo (MC) code, and the DOSXYZnrc MC dose calculations. Calculations were performed with voxel size of 0.2 x 0.2 x 0.1 cm3. Dosimetry validation was performed using radiographic film and micro- or parallel-plate chambers. Calculated and measured data were compared using technical computing software. Beam sharpness (penumbra) degraded with decreasing incident beam energy and field size (FS), and increasing SSD. A 70 cm SSD was found to be optimal. The PDD decreased significantly with decreasing FS. The comparisons demonstrated excellent agreement for calculations and measurements within 3%, 1 mm. This study shows that accurate calculations for MERT as delivered with existing photon MLC are feasible and allows the opportunity to take advantage of the dynamic leaf motion capabilities and control systems, to provide conformal dose distributions.
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26
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Chetty IJ, Curran B, Cygler JE, DeMarco JJ, Ezzell G, Faddegon BA, Kawrakow I, Keall PJ, Liu H, Ma CMC, Rogers DWO, Seuntjens J, Sheikh-Bagheri D, Siebers JV. Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning. Med Phys 2007; 34:4818-53. [PMID: 18196810 DOI: 10.1118/1.2795842] [Citation(s) in RCA: 438] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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28
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Wieslander E, Knöös T. A virtual-accelerator-based verification of a Monte Carlo dose calculation algorithm for electron beam treatment planning in clinical situations. Radiother Oncol 2007; 82:208-17. [PMID: 17222475 DOI: 10.1016/j.radonc.2006.12.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 11/21/2006] [Accepted: 12/08/2006] [Indexed: 10/23/2022]
Abstract
BACKGROUND AND PURPOSE The introduction of Monte Carlo (MC) techniques for treatment planning and also for verification purposes will have considerable impact on the radiation therapy planning process. The aim of this work was to use a virtual accelerator to study the performance of a MC-based electron dose calculation algorithm, implemented in a commercial treatment planning system. METHODS The performance in phantoms containing air and bone as well as in patient-specific geometries (thorax wall, nose, parotid gland and spinal cord) has been studied. RESULTS The agreement between the virtual accelerator and the MC dose calculation algorithm is generally very good. A gamma-evaluation with criteria of 0.03 Gy/3 mm (per Gy at the depth of maximum dose) shows that, even for the worst cases, only a small volume of about 1.5% has gamma>1.0. In the worst case, with the 0.02 Gy/2 mm criteria, about 92% of the volume receiving more than 0.85 Gy per 100 monitor units (MU) has gamma-values <1.0. The corresponding value for the volume receiving more than 0.10 Gy/100 MU is about 98%. For the 18 MeV spinal-cord case, where a 6 x 20 cm2 insert is used, the TPS underestimates the dose outside the primary field due to inadequate modelling of the insert. CONCLUSION The possibility of dose calculations in typical patient cases makes the virtual accelerator a powerful tool for validation and evaluation of dose calculation algorithms present in treatment planning systems.
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Abstract
For over 50 years, electron beams have been an important modality for providing an accurate dose of radiation to superficial cancers and disease and for limiting the dose to underlying normal tissues and structures. This review looks at many of the important contributions of physics and dosimetry to the development and utilization of electron beam therapy, including electron treatment machines, dose specification and calibration, dose measurement, electron transport calculations, treatment and treatment-planning tools, and clinical utilization, including special procedures. Also, future changes in the practice of electron therapy resulting from challenges to its utilization and from potential future technology are discussed.
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Affiliation(s)
- Kenneth R Hogstrom
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001, USA.
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Aljarrah K, Sharp GC, Neicu T, Jiang SB. Determination of the initial beam parameters in Monte Carlo linac simulation. Med Phys 2006; 33:850-8. [PMID: 16696460 DOI: 10.1118/1.2168433] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
For Monte Carlo linac simulations and patient dose calculations, it is important to accurately determine the phase space parameters of the initial electron beam incident on the target. These parameters, such as mean energy and radial intensity distribution, have traditionally been determined by matching the calculated dose distributions with the measured dose distributions through a trial and error process. This process is very time consuming and requires a lot of Monte Carlo simulation experience and computational resources. In this paper, we propose an easy, efficient, and accurate method for the determination of the initial beam parameters. We hypothesize that (1) for one type of linacs, the geometry and material of major components of the treatment head are the same; the only difference is the phase space parameters of the initial electron beam incident on the target, and (2) most linacs belong to a limited number of linac types. For each type of linacs, Monte Carlo treatment planning system (MC-TPS) vendors simulate the treatment head and calculate the three-dimensional (3D) dose distribution in water phantom for a grid of initial beam energies and radii. The simulation results (phase space files and dose distribution files) are then stored in a data library. When a MC-TPS user tries to model their linac which belongs to the same type, a standard set of measured dose data is submitted and compared with the calculated dose distributions to determine the optimal combination of initial beam energy and radius. We have applied this method to the 6 MV beam of a Varian 21EX linac. The linac was simulated using EGSNRC/BEAM code and the dose in water phantom was calculated using EGSNRC/DOSXYZ. We have also studied issues related to the proposed method. Several common cost functions were tested for comparing measured and calculated dose distributions, including chi2, mean absolute error, dose difference at the penumbra edge point, slope of the dose difference of the lateral profile, and the newly proposed Kappaalpha factor (defined as the fraction of the voxels with absolute dose difference less than alpha%). It was found that the use of the slope of the lateral profile difference or the difference of the penumbra edge points may lead to inaccurate determination of the initial beam parameters. We also found that in general the cost function value is very sensitive to the simulation statistical uncertainty, and there is a tradeoff between uncertainty and specificity. Due to the existence of statistical uncertainty in simulated dose distributions, it is practically impossible to determine the best energy/radius combination; we have to accept a group of energy/radius combinations. We have also investigated the minimum required data set for accurate determination of the initial beam parameters. We found that the percent depth dose curves along or only a lateral profile at certain depth for a large field size is not sufficient and the minimum data set should include several lateral profiles at various depths as well as the central axis percent depth dose curve for a large field size.
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Affiliation(s)
- Khaled Aljarrah
- Department of Physics, University of Massachusetts Lowell, Lowell, Massachusetts, USA
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Ali Nedaie H, Mosleh-Shirazi M, Shariary M, Gharaati H, Allahverdi M. Monte Carlo study of electron dose distributions produced by the elekta precise linear accelerator. Rep Pract Oncol Radiother 2006. [DOI: 10.1016/s1507-1367(06)71074-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Ye SJ, Pareek PN, Spencer S, Duan J, Brezovich IA. Monte Carlo techniques for scattering foil design and dosimetry in total skin electron irradiations. Med Phys 2005; 32:1460-8. [PMID: 16013701 DOI: 10.1118/1.1924368] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Total skin electron irradiation (TSEI) with single fields requires large electron beams having good dose uniformity, dmax at the skin surface, and low bremsstrahlung contamination. To satisfy these requirements, energy degraders and scattering foils have to be specially designed for the given accelerator and treatment room. We used Monte Carlo (MC) techniques based on EGS4 user codes (BEAM, DOSXYZ, and DOSRZ) as a guide in the beam modifier design of our TSEI system. The dosimetric characteristics at the treatment distance of 382 cm source-to-surface distance (SSD) were verified experimentally using a linear array of 47 ion chambers, a parallel plate chamber, and radiochromic film. By matching MC simulations to standard beam measurements at 100 cm SSD, the parameters of the electron beam incident on the vacuum window were determined. Best match was achieved assuming that electrons were monoenergetic at 6.72 MeV, parallel, and distributed in a circular pattern having a Gaussian radial distribution with full width at half maximum = 0.13 cm. These parameters were then used to simulate our TSEI unit with various scattering foils. Two of the foils were fabricated and experimentally evaluated by measuring off-axis dose uniformity and depth doses. A scattering foil, consisting of a 12 x 12 cm2 aluminum plate of 0.6 cm thickness and placed at isocenter perpendicular to the beam direction, was considered optimal. It produced a beam that was flat within +/-3% up to 60 cm off-axis distance, dropped by not more than 8% at a distance of 90 cm, and had an x-ray contamination of <3%. For stationary beams, MC-computed dmax, Rp, and R50 agreed with measurements within 0.5 mm. The MC-predicted surface dose of the rotating phantom was 41% of the dose rate at dmax of the stationary phantom, whereas our calculations based on a semiempirical formula in the literature yielded a drop to 42%. The MC simulations provided the guideline of beam modifier design for TSEI and estimated the dosimetric performance for stationary and rotational irradiations.
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Affiliation(s)
- Sung-Joon Ye
- Department of Radiation Oncology, The University of Alabama School of Medicine, 1824 6th Avenue South, Birmingham, Alabama 35294, USA.
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Abstract
Accurate simulation of large electron fields may lead to improved accuracy in Monte Carlo treatment planning while simplifying the commissioning procedure. We have used measurements made with wide-open jaws and no electron applicator to adjust simulation parameters. Central axis depth dose curves and profiles of 6-21 MeV electron beams measured in this geometry were used to estimate source and geometry parameters, including those that affect beam symmetry: incident beam direction and offset of the secondary scattering foil and monitor chamber from the beam axis. Parameter estimation relied on a comprehensive analysis of the sensitivity of the measured quantities, in the large field, to source and geometry parameters. Results demonstrate that the EGS4 Monte Carlo system is capable of matching dose distributions in the largest electron field to the least restrictive of 1 cGy or 1 mm, with D(max) of 100 cGy, over the full energy range. This match results in an underestimation of the bremsstrahlung dose of 10-20% at 15-21 MeV, exceeding the combined experimental and calculational uncertainty in this quantity of 3%. The simulation of electron scattering at energies of 15-21 MeV in EGS4 may be in error. The recently released EGSnrc/BEAMnrc system may provide a better match to measurement.
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Affiliation(s)
- B Faddegon
- Department of Radiation Oncology, University of California, San Francisco, CA 94143, USA.
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Björk P, Knöös T, Nilsson P. Measurements of output factors with different detector types and Monte Carlo calculations of stopping-power ratios for degraded electron beams. Phys Med Biol 2004; 49:4493-506. [PMID: 15552413 DOI: 10.1088/0031-9155/49/19/004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The aim of the present study was to investigate three different detector types (a parallel-plate ionization chamber, a p-type silicon diode and a diamond detector) with regard to output factor measurements in degraded electron beams, such as those encountered in small-electron-field radiotherapy and intraoperative radiation therapy (IORT). The Monte Carlo method was used to calculate mass collision stopping-power ratios between water and the different detector materials for these complex electron beams (nominal energies of 6, 12 and 20 MeV). The diamond detector was shown to exhibit excellent properties for output factor measurements in degraded beams and was therefore used as a reference. The diode detector was found to be well suited for practical measurements of output factors, although the water-to-silicon stopping-power ratio was shown to vary slightly with treatment set-up and irradiation depth (especially for lower electron energies). Application of ionization-chamber-based dosimetry, according to international dosimetry protocols, will introduce uncertainties smaller than 0.3% into the output factor determination for conventional IORT beams if the variation of the water-to-air stopping-power ratio is not taken into account. The IORT system at our department includes a 0.3 cm thin plastic scatterer inside the therapeutic beam, which furthermore increases the energy degradation of the electrons. By ignoring the change in the water-to-air stopping-power ratio due to this scatterer, the output factor could be underestimated by up to 1.3%. This was verified by the measurements. In small-electron-beam dosimetry, the water-to-air stopping-power ratio variation with field size could mostly be ignored. For fields with flat lateral dose profiles (>3 x 3 cm2), output factors determined with the ionization chamber were found to be in close agreement with the results of the diamond detector. For smaller field sizes the lateral extension of the ionization chamber hampers its use. We therefore recommend that the readily available silicon diode detector should be used for output factor measurements in complex electron fields.
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Affiliation(s)
- Peter Björk
- Department of Radiation Physics, Lund University Hospital, Lund, Sweden.
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Pavón EC, Sánchez-Doblado F, Leal A, Capote R, Lagares JI, Perucha M, Arráns R. Total skin electron therapy treatment verification: Monte Carlo simulation and beam characteristics of large non-standard electron fields. Phys Med Biol 2004; 48:2783-96. [PMID: 14516101 DOI: 10.1088/0031-9155/48/17/304] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Total skin electron therapy (TSET) is a complex technique which requires non-standard measurements and dosimetric procedures. This paper investigates an essential first step towards TSET Monte Carlo (MC) verification. The non-standard 6 MeV 40 x 40 cm2 electron beam at a source to surface distance (SSD) of 100 cm as well as its horizontal projection behind a polymethylmethacrylate (PMMA) screen to SSD = 380 cm were evaluated. The EGS4 OMEGA-BEAM code package running on a Linux home made 47 PCs cluster was used for the MC simulations. Percentage depth-dose curves and profiles were calculated and measured experimentally for the 40 x 40 cm2 field at both SSD = 100 cm and patient surface SSD = 380 cm. The output factor (OF) between the reference 40 x 40 cm2 open field and its horizontal projection as TSET beam at SSD = 380 cm was also measured for comparison with MC results. The accuracy of the simulated beam was validated by the good agreement to within 2% between measured relative dose distributions, including the beam characteristic parameters (R50, R80, R100, Rp, E0) and the MC calculated results. The energy spectrum, fluence and angular distribution at different stages of the beam (at SSD = 100 cm, at SSD = 364.2 cm, behind the PMMA beam spoiler screen and at treatment surface SSD = 380 cm) were derived from MC simulations. Results showed a final decrease in mean energy of almost 56% from the exit window to the treatment surface. A broader angular distribution (FWHM of the angular distribution increased from 13 degrees at SSD = 100 cm to more than 30 degrees at the treatment surface) was fully attributable to the PMMA beam spoiler screen. OF calculations and measurements agreed to less than 1%. The effect of changing the electron energy cut-off from 0.7 MeV to 0.521 MeV and air density fluctuations in the bunker which could affect the MC results were shown to have a negligible impact on the beam fluence distributions. Results proved the applicability of using MC as a treatment verification tool for complex radiotherapy techniques.
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Affiliation(s)
- Ester Carrasco Pavón
- Dpto Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Avda Sánchez Pizjuán, 4, E-41009, Sevilla, Spain.
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Ma CM, Price RA, Li JS, Chen L, Wang L, Fourkal E, Qin L, Yang J. Monitor unit calculation for Monte Carlo treatment planning. Phys Med Biol 2004; 49:1671-87. [PMID: 15152923 DOI: 10.1088/0031-9155/49/9/006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this work, we investigate a formalism for monitor unit (MU) calculation in Monte Carlo based treatment planning. By relating MU to dose measured under reference calibration conditions (central axis, depth of dose maximum in water, 10 cm x 10 cm field defined at 100 cm source-to-surface distance) our formalism determines the MU required for a treatment plan based on the prescription dose and Monte Carlo calculated dose distribution. Detailed descriptions and formulae are given for various clinical situations including conventional treatments and advanced techniques such as intensity-modulated radiotherapy (IMRT) and modulated electron radiotherapy (MERT). Analysis is made of the effects of source modelling, beam modifier simulation and patient dose calculation accuracy, all of which are important factors for absolute dose calculations using Monte Carlo simulations. We have tested the formalism through phantom measurements and the predicted MU values were consistent with measured values to within 2%. The formalism has been used for MU calculation and plan comparison for advanced treatment techniques such as MERT, extracranial stereotactic IMRT, MRI-based treatment planning and intensity-modulated laser-proton therapy studies. It is also used for absolute dose calculations using Monte Carlo simulations for treatment verification, which has become part of our comprehensive IMRT quality assurance programme.
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Affiliation(s)
- C M Ma
- Radiation Oncology Department, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
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Turian JV, Smith BD, Bernard DA, Griem KL, Chu JC. Monte Carlo calculations of output factors for clinically shaped electron fields. J Appl Clin Med Phys 2004; 5:42-63. [PMID: 15738912 PMCID: PMC5723462 DOI: 10.1120/jacmp.v5i2.1976] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
We report on the use of the EGS4/BEAM Monte Carlo technique to predict the output factors for clinically relevant, irregularly shaped inserts as they intercept a linear accelerator's electron beams. The output factor for a particular combination—energy, cone, insert, and source‐to‐surface distance (SSD)—is defined in accordance with AAPM TG‐25 as the product of cone correction factor and insert correction factor, evaluated at the depth of maximum dose. Since cone correction factors are easily obtained, we focus our investigation on the insert correction factors (ICFs). An analysis of the inserts used in routine clinical practice resulted in the identification of a set of seven “idealized” shapes characterized by specific parameters. The ICFs for these shapes were calculated using a Monte Carlo method (EGS4/BEAM) and measured for a subset of them using an ion chamber and well‐established measurement methods. Analytical models were developed to predict the Monte Carlo–calculated ICF values for various electron energies, cone sizes, shapes, and SSDs. The goodness‐of‐fit between predicted and Monte Carlo–calculated ICF values was tested using the Kolmogorov–Smirnoff statistical test. Results show that Monte Carlo–calculated ICFs match the measured values within 2.0% for most of the shapes considered, except for few highly elongated fields, where deviations up to 4.0% were recorded. Predicted values based on analytical modeling agree with measured ICF values within 2% to 3% for all configurations. We conclude that the predicted ICF values based on modeling of Monte Carlo–calculated values could be introduced in clinical use. PACS numbers: 87.53.Wz, 87.53.Hv
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Affiliation(s)
- Julius V Turian
- Department of Radiation Oncology, University of Illinois Medical Center, OCC C-400, 1801 W. Taylor Street, Chicago, Illinois 60612, USA.
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Jeraj R, Mackie TR, Balog J, Olivera G, Pearson D, Kapatoes J, Ruchala K, Reckwerdt P. Radiation characteristics of helical tomotherapy. Med Phys 2004; 31:396-404. [PMID: 15000626 DOI: 10.1118/1.1639148] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Helical tomotherapy is a dedicated intensity modulated radiation therapy (IMRT) system with on-board imaging capability (MVCT) and therefore differs from conventional treatment units. Different design goals resulted in some distinctive radiation field characteristics. The most significant differences in the design are the lack of flattening filter, increased shielding of the collimators, treatment and imaging operation modes and narrow fan beam delivery. Radiation characteristics of the helical tomotherapy system, sensitivity studies of various incident electron beam parameters and radiation safety analyses are presented here. It was determined that the photon beam energy spectrum of helical tomotherapy is similar to that of more conventional radiation treatment units. The two operational modes of the system result in different nominal energies of the incident electron beam with approximately 6 MeV and 3.5 MeV in the treatment and imaging modes, respectively. The off-axis mean energy dependence is much lower than in conventional radiotherapy units with less than 5% variation across the field, which is the consequence of the absent flattening filter. For the same reason the transverse profile exhibits the characteristic conical shape resulting in a 2-fold increase of the beam intensity in the center. The radiation leakage outside the field was found to be negligible at less than 0.05% because of the increased shielding of the collimators. At this level the in-field scattering is a dominant source of the radiation outside the field and thus a narrow field treatment does not result in the increased leakage. The sensitivity studies showed increased sensitivity on the incident electron position because of the narrow fan beam delivery and high sensitivity on the incident electron energy, as common to other treatment systems. All in all, it was determined that helical tomotherapy is a system with some unique radiation characteristics, which have been to a large extent optimized for intensity modulated delivery.
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Affiliation(s)
- Robert Jeraj
- Department of Medical Physics, University of Wisconsin-Madison, 1530 MSC, 1300 University Avenue, Madison, Wisconsin 53706, USA.
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Cho SH, Ibbott GS. Reference photon dosimetry data: a preliminary study of in-air off-axis factor, percentage depth dose, and output factor of the Siemens Primus linear accelerator. J Appl Clin Med Phys 2003; 4:300-6. [PMID: 14604419 PMCID: PMC5724467 DOI: 10.1120/jacmp.v4i4.2500] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The dosimetric characteristics for modern computer-controlled linear accelerators with the same make, model, and nominal energy are known to be very similar, as long as the machines are unaltered from the manufacturer's original specifications. In this preliminary study, a quantitative investigation of the similarity in the basic photon dosimetry data from the Siemens Primus linear accelerators at eight different institutions is reported. The output factor, percentage depth dose (PDD), and in-air off-axis factor (OAF) for the 6 and 18 MV photon beams measured or verified by the Radiological Physics Center (RPC) were analyzed. The RPC-measured output factors varied by less than about 2% for each field size. The difference between the maximum and minimum RPC-verified PDD values at each depth was less than about 3%. The difference between the maximum and minimum RPC-measured in-air OAF was no more than 4% at all off-axis distances considered in this study. These results strongly suggest that it is feasible to establish a reference photon dosimetry data set for each make, model, and nominal energy, universally applicable to those machines unaltered from the manufacturers' original specifications, within a clinically acceptable tolerance (e.g., approximately +/-2%).
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Affiliation(s)
- S. H. Cho
- Department of Radiation PhysicsThe University of Texas M.D. Anderson Cancer Center1515 Holcombe Boulevard, Unit 547HoustonTexas77030
| | - G. S. Ibbott
- Department of Radiation PhysicsThe University of Texas M.D. Anderson Cancer Center1515 Holcombe Boulevard, Unit 547HoustonTexas77030
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