The Experts below are selected from a list of 108 Experts worldwide ranked by ideXlab platform
Jaouad Tajmouati - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Secondary Photons Emergent from Combined Material Slab as a Function of Slab Thickness
Moscow University Physics Bulletin, 2018Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad Tajmouati, Abdessamad DidiAbstract:Material science is very important for developing the linear accelerator. Determination and understanding of material behavior face to X-rays is a basic study for photon Beam Modifiers improvements. In this study, the 6 MV photon Beams produced by Varian Clinac 2100 was modelled by Monte Carlo simulation using Beamnrc code and thereafter the flattening filter was replaced by a slab of aluminum and copper separately and by slab of both materials combined together with different thickness of 2.5, 5, 7.5, and 10 mm. The purpose of this study is to investigate the scattered photons with thickness of combined material slab as a function of off-axis distance. The scattered photons increased with thickness of copper alone slab, combined aluminum-copper slab and copper-aluminum slab, but for aluminum alone slab they decreased with slab thickness. The stacking order of these two materials affects the characterization of scattered photons emergent from material slab with thickness. The combination of materials and the manner that the stacking was done affects the scattered photons production. The material combination could improve the radiotherapy efficiency in Beam Modifier development using more than two materials.
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Photon Beam softening coefficient determination with slab thickness in small filed size: Monte Carlo study
Physics of Particles and Nuclei Letters, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:Determination and understanding of photon Beam softening using material soften photon Beam for clinical usage is important for material study for attenuation and for Beam Modifier enhancements and linac improvements. Monte Carlo model was used to simulate 6 MeV photon Beams produced by Varian Clinac 2100 accelerator with flattening filter thereafter the flattening filter was replaced by a slab of aluminum and copper with different of 0.5, 1, 1.5 and 2 mm. The Monte Carlo geometry was validated by a gamma index acceptance rate of 99% in PDD and 98% in dose profiles, the gamma criteria was 3% for dose difference and 3mm for distance to agreement. The purpose was to investigate the Beam softening for small size and Beam attenuation as a function of inserted slab thickness of copper and aluminum and also as a function of off-axis distance. For Beam softening evaluation, variation amplitude of Beam softening coefficient a1 was very high near the Beam central axis and decreased with off-axis distance and also it was high for aluminum slab compared to copper slab. For aluminum slab, variation amplitude of Beam softening coefficient a1 have a minimum at–0.5 cm–1 and a maximum at 0.5 cm–1 and for copper slab, variation amplitude of Beam softening a1 have a minimum at–0.15 cm–1 and a maximum at 0.11 cm–1. Variation amplitude of Beam softening coefficient a2 was very high near the Beam central axis and decreased with off-axis distance and it was very high for aluminum slab compared to copper slab. For aluminum slab, variation amplitude of Beam softening coefficient a2 have a minimum at–0.54 cm–2 and a maximum at 0.44 cm–2 and for copper slab, variation amplitude of Beam softening coefficient a2 have a minimum at–0.111 cm–2 and a maximum at 0.0825 cm–2.
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Relative Attenuation and Beam Softening Study with Flattening Filter Volume Reduction: Monte Carlo Study
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:The flattening filter (FF) volume reduction increases the clinical photons for deep tumor treatment. The Beam softening determination is crucial for flattening filter improvement in geometry and materials. Determination and understanding the photon Beam properties using material and geometry of a Beam Modifier is very important for dosimetry improvement in radiotherapy department and also for patient life quality development. This Monte Carlo study aims to investigate the relative attenuation and associated Beam softening due to flattening filter volume reduction. The FF volume was reduced by 10, 20, and 30% of the initial volume data provided by the manufacturer. The relative attenuation and Beam softening coefficients increased with FF volume reduction more near the Beam central axis than the Beam edge. We have illustrated that relative photon Beam softening coefficient v was more stable than the coefficient u as a function of offaxis distance and with FF volume reduction. For increasing the photon fluence and dose delivered inside the phantom volume as mentioned in IAEA protocols, the FF volume should be reduced more near the FF top region than the FF edge region. Our work can be a basic investigation that will be used in improvement for the future linac configuration in terms of photon Beam softening for material, geometry, and volume that were used in Beam Modifiers as a flattening filter.
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Study of Possibility to Reduce Flattening Filter Volume for Increasing Energetic Photons for High Radiotherapy Efficiency
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad Tajmouati, Abdesslam Lamrabet, Yassine BenkhouyAbstract:Increasing dose for improved radiotherapy efficiency is essential for linear accelerator development and also for flattening filter geometry and material enhancement. Determination and understanding the photon Beam properties using material and geometry of a Beam Modifier is very important in radiotherapy department and also for high patient life quality. This Monte Carlo study aims to improve the FF in a linac for increasing the photon number at the entrance of treatment volume tumor and the dose delivered inside the treatment volume as recommended by the IAEA protocols. The aim of this study was to check out the possibility to reduce the flattening filter volume for improving the clinical photons at phantom surface. We have studied photon attenuation coefficients and Beam softening coefficients with FF volume reduction. The FF volume was reduced by 10, 20, and 30% of initial FF volume. The photon fluence increased with FF volume reduction near the Beam central axis than the Beam edge and the Beam softening coefficients remained apparently invariable with FF volume reduction as a function of off-axis distance. Our work can be a basic study that will be used in research and improvement for future linac configuration in terms of photon attenuation and Beam softening for a material, geometry and volume that were used for finding out good flattening and good softening to produce an optimal delivered dose as recommended by IAEA.
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Photon Beam softening coefficients evaluation for a 6 MeV photon Beam for an aluminum slab: Monte Carlo study using Beamnrc Code, DOSXYZnrc Code, and BeamDP code
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:Determination and understanding the photon Beam attenuation by the photon Beam Modifier and the radiation Beam softening for clinical use is more important part of material study for the Beam Modifier enhancements and the linac improvements. A Monte Carlo model was used to simulate 6 MeV photon Beams from a Varian Clinac 2100 accelerator with the flattening filter and the later was replaced by the aluminum slab with variable thickness. The Monte Carlo geometry was validated by a gamma index acceptance rate of 99% in PDD and 98% in dose profiles, the gamma criteria was 3% for dose difference and 3 mm for distance to agreement. The purpose was to investigate aluminum material attenuation and Beam softening coefficients as a function of the inserted aluminum slab thickness and of off-axis distance. The attenuation and Beam softening coefficients were not identical for the same off-axis distance and they varied as a function of aluminum slab thickness. The results of our study were shown that the Beam softening coefficients were varied with thickness Beam Modifier material used for Beam softening and the off-axis distance inside the irradiation field. Thereafter, the softening coefficient a 1 have a maximum of 2.5 × 10–1 cm–1 for the aluminum slab thickness of 1 mm, 1.4 × 10–1 cm–1 for the aluminum slab thickness of 1.5 mm and 4.47 × 10–2 cm–1 for the aluminum slab thickness of 2 mm. The maximum of the second softening coefficient a 2 was 1.02 × 10–2 cm–2 for the aluminum slab thickness of 1 mm, was 1.92 × 10–2 cm–2 for the aluminum slab thickness of 1.5 mm and was 1.93 × 10–2 cm–2 for the aluminum slab thickness of 2 mm. Our study can be a basic investigation of photon Beam softening material that will be used in the future linac configuration and also in the photon Beam Modifiers.
Mohamed Bencheikh - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Secondary Photons Emergent from Combined Material Slab as a Function of Slab Thickness
Moscow University Physics Bulletin, 2018Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad Tajmouati, Abdessamad DidiAbstract:Material science is very important for developing the linear accelerator. Determination and understanding of material behavior face to X-rays is a basic study for photon Beam Modifiers improvements. In this study, the 6 MV photon Beams produced by Varian Clinac 2100 was modelled by Monte Carlo simulation using Beamnrc code and thereafter the flattening filter was replaced by a slab of aluminum and copper separately and by slab of both materials combined together with different thickness of 2.5, 5, 7.5, and 10 mm. The purpose of this study is to investigate the scattered photons with thickness of combined material slab as a function of off-axis distance. The scattered photons increased with thickness of copper alone slab, combined aluminum-copper slab and copper-aluminum slab, but for aluminum alone slab they decreased with slab thickness. The stacking order of these two materials affects the characterization of scattered photons emergent from material slab with thickness. The combination of materials and the manner that the stacking was done affects the scattered photons production. The material combination could improve the radiotherapy efficiency in Beam Modifier development using more than two materials.
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Photon Beam softening coefficient determination with slab thickness in small filed size: Monte Carlo study
Physics of Particles and Nuclei Letters, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:Determination and understanding of photon Beam softening using material soften photon Beam for clinical usage is important for material study for attenuation and for Beam Modifier enhancements and linac improvements. Monte Carlo model was used to simulate 6 MeV photon Beams produced by Varian Clinac 2100 accelerator with flattening filter thereafter the flattening filter was replaced by a slab of aluminum and copper with different of 0.5, 1, 1.5 and 2 mm. The Monte Carlo geometry was validated by a gamma index acceptance rate of 99% in PDD and 98% in dose profiles, the gamma criteria was 3% for dose difference and 3mm for distance to agreement. The purpose was to investigate the Beam softening for small size and Beam attenuation as a function of inserted slab thickness of copper and aluminum and also as a function of off-axis distance. For Beam softening evaluation, variation amplitude of Beam softening coefficient a1 was very high near the Beam central axis and decreased with off-axis distance and also it was high for aluminum slab compared to copper slab. For aluminum slab, variation amplitude of Beam softening coefficient a1 have a minimum at–0.5 cm–1 and a maximum at 0.5 cm–1 and for copper slab, variation amplitude of Beam softening a1 have a minimum at–0.15 cm–1 and a maximum at 0.11 cm–1. Variation amplitude of Beam softening coefficient a2 was very high near the Beam central axis and decreased with off-axis distance and it was very high for aluminum slab compared to copper slab. For aluminum slab, variation amplitude of Beam softening coefficient a2 have a minimum at–0.54 cm–2 and a maximum at 0.44 cm–2 and for copper slab, variation amplitude of Beam softening coefficient a2 have a minimum at–0.111 cm–2 and a maximum at 0.0825 cm–2.
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Relative Attenuation and Beam Softening Study with Flattening Filter Volume Reduction: Monte Carlo Study
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:The flattening filter (FF) volume reduction increases the clinical photons for deep tumor treatment. The Beam softening determination is crucial for flattening filter improvement in geometry and materials. Determination and understanding the photon Beam properties using material and geometry of a Beam Modifier is very important for dosimetry improvement in radiotherapy department and also for patient life quality development. This Monte Carlo study aims to investigate the relative attenuation and associated Beam softening due to flattening filter volume reduction. The FF volume was reduced by 10, 20, and 30% of the initial volume data provided by the manufacturer. The relative attenuation and Beam softening coefficients increased with FF volume reduction more near the Beam central axis than the Beam edge. We have illustrated that relative photon Beam softening coefficient v was more stable than the coefficient u as a function of offaxis distance and with FF volume reduction. For increasing the photon fluence and dose delivered inside the phantom volume as mentioned in IAEA protocols, the FF volume should be reduced more near the FF top region than the FF edge region. Our work can be a basic investigation that will be used in improvement for the future linac configuration in terms of photon Beam softening for material, geometry, and volume that were used in Beam Modifiers as a flattening filter.
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Study of Possibility to Reduce Flattening Filter Volume for Increasing Energetic Photons for High Radiotherapy Efficiency
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad Tajmouati, Abdesslam Lamrabet, Yassine BenkhouyAbstract:Increasing dose for improved radiotherapy efficiency is essential for linear accelerator development and also for flattening filter geometry and material enhancement. Determination and understanding the photon Beam properties using material and geometry of a Beam Modifier is very important in radiotherapy department and also for high patient life quality. This Monte Carlo study aims to improve the FF in a linac for increasing the photon number at the entrance of treatment volume tumor and the dose delivered inside the treatment volume as recommended by the IAEA protocols. The aim of this study was to check out the possibility to reduce the flattening filter volume for improving the clinical photons at phantom surface. We have studied photon attenuation coefficients and Beam softening coefficients with FF volume reduction. The FF volume was reduced by 10, 20, and 30% of initial FF volume. The photon fluence increased with FF volume reduction near the Beam central axis than the Beam edge and the Beam softening coefficients remained apparently invariable with FF volume reduction as a function of off-axis distance. Our work can be a basic study that will be used in research and improvement for future linac configuration in terms of photon attenuation and Beam softening for a material, geometry and volume that were used for finding out good flattening and good softening to produce an optimal delivered dose as recommended by IAEA.
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Photon Beam softening coefficients evaluation for a 6 MeV photon Beam for an aluminum slab: Monte Carlo study using Beamnrc Code, DOSXYZnrc Code, and BeamDP code
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:Determination and understanding the photon Beam attenuation by the photon Beam Modifier and the radiation Beam softening for clinical use is more important part of material study for the Beam Modifier enhancements and the linac improvements. A Monte Carlo model was used to simulate 6 MeV photon Beams from a Varian Clinac 2100 accelerator with the flattening filter and the later was replaced by the aluminum slab with variable thickness. The Monte Carlo geometry was validated by a gamma index acceptance rate of 99% in PDD and 98% in dose profiles, the gamma criteria was 3% for dose difference and 3 mm for distance to agreement. The purpose was to investigate aluminum material attenuation and Beam softening coefficients as a function of the inserted aluminum slab thickness and of off-axis distance. The attenuation and Beam softening coefficients were not identical for the same off-axis distance and they varied as a function of aluminum slab thickness. The results of our study were shown that the Beam softening coefficients were varied with thickness Beam Modifier material used for Beam softening and the off-axis distance inside the irradiation field. Thereafter, the softening coefficient a 1 have a maximum of 2.5 × 10–1 cm–1 for the aluminum slab thickness of 1 mm, 1.4 × 10–1 cm–1 for the aluminum slab thickness of 1.5 mm and 4.47 × 10–2 cm–1 for the aluminum slab thickness of 2 mm. The maximum of the second softening coefficient a 2 was 1.02 × 10–2 cm–2 for the aluminum slab thickness of 1 mm, was 1.92 × 10–2 cm–2 for the aluminum slab thickness of 1.5 mm and was 1.93 × 10–2 cm–2 for the aluminum slab thickness of 2 mm. Our study can be a basic investigation of photon Beam softening material that will be used in the future linac configuration and also in the photon Beam Modifiers.
Sharon A. Spencer - One of the best experts on this subject based on the ideXlab platform.
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su ff t 282 Beam Modifier design for total skin electron irradiations using monte carlo techniques
Medical Physics, 2005Co-Authors: Ivan A. Brezovich, Prem N. Pareek, Jun Duan, Sharon A. SpencerAbstract:Purpose: Total skin electron irradiation (TSEI) requires large electron Beams having good dose uniformity, d max at the skin surface, and low bremsstrahlung contamination. Energy degraders and scattering foils have to be specially designed for the given accelerator and treatment room. Method and Materials:Monte Carlo(MC) techniques based on EGS4 user codes (Beam, DOSXYZ, and DOSRZ) guided the Beam Modifier design of our TSEI system. The dosimetric characteristics at the treatment distance of 382 cm 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 primary electrons were determined to be mono‐energetic at 6.72 MeV, parallel, and circular Beams having a Gaussian radial distribution with FWHM = 0.13 cm. They were then used to simulate our TSEI with eight sets of energy degraders and flattening filters. Results: An energy degrader of a 0.6 cm‐thick PMMA plate, blacking a jaw‐shaped field (40 × 40 cm2) at 100 cm SSD, showed the best performance in terms of dose rate and uniformity. A flattening filter, consisting of a 12 × 12 cm2aluminum plate of 0.6 cm‐thickness and placed just behind the energy degrader was considered optimal. Such optimized combination produced a Beam that was flat within ±3% up to 60 cm off‐axis distance, dropped by not more than 6% at a distance of 90 cm, and had an x‐ray of < 3%. The maximum dose of the rotating phantom occurred at the surface and was approximately 40% of the maximum dose (at 0.65 cm‐depth) of the stationary phantom. Conclusion: By evaluating the dosimetric performance of Beam Modifier designs for TSEI, the Monte Carlo simulations reduced the costly efforts that could, otherwise, result from constructing and measuring lots of prototypes.
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SU‐FF‐T‐282: Beam Modifier Design for Total Skin Electron Irradiations Using Monte Carlo Techniques
Medical Physics, 2005Co-Authors: Ivan A. Brezovich, Prem N. Pareek, Jun Duan, Sharon A. SpencerAbstract:Purpose: Total skin electron irradiation (TSEI) requires large electron Beams having good dose uniformity, d max at the skin surface, and low bremsstrahlung contamination. Energy degraders and scattering foils have to be specially designed for the given accelerator and treatment room. Method and Materials:Monte Carlo(MC) techniques based on EGS4 user codes (Beam, DOSXYZ, and DOSRZ) guided the Beam Modifier design of our TSEI system. The dosimetric characteristics at the treatment distance of 382 cm 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 primary electrons were determined to be mono‐energetic at 6.72 MeV, parallel, and circular Beams having a Gaussian radial distribution with FWHM = 0.13 cm. They were then used to simulate our TSEI with eight sets of energy degraders and flattening filters. Results: An energy degrader of a 0.6 cm‐thick PMMA plate, blacking a jaw‐shaped field (40 × 40 cm2) at 100 cm SSD, showed the best performance in terms of dose rate and uniformity. A flattening filter, consisting of a 12 × 12 cm2aluminum plate of 0.6 cm‐thickness and placed just behind the energy degrader was considered optimal. Such optimized combination produced a Beam that was flat within ±3% up to 60 cm off‐axis distance, dropped by not more than 6% at a distance of 90 cm, and had an x‐ray of < 3%. The maximum dose of the rotating phantom occurred at the surface and was approximately 40% of the maximum dose (at 0.65 cm‐depth) of the stationary phantom. Conclusion: By evaluating the dosimetric performance of Beam Modifier designs for TSEI, the Monte Carlo simulations reduced the costly efforts that could, otherwise, result from constructing and measuring lots of prototypes.
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Monte Carlo techniques for scattering foil design and dosimetry in total skin electron irradiations
Medical physics, 2005Co-Authors: Prem N. Pareek, Jun Duan, Sharon A. Spencer, Ivan A. BrezovichAbstract:Total skinelectron irradiation (TSEI) with single fields requires large electron Beams having good dose uniformity, d max 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 × 12 cm 2 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 d max , R p , and R 50 agreed with measurements within 0.5 mm . The MC-predicted surface dose of the rotating phantom was 41% of the dose rate at d max 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.
Ivan A. Brezovich - One of the best experts on this subject based on the ideXlab platform.
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su ff t 282 Beam Modifier design for total skin electron irradiations using monte carlo techniques
Medical Physics, 2005Co-Authors: Ivan A. Brezovich, Prem N. Pareek, Jun Duan, Sharon A. SpencerAbstract:Purpose: Total skin electron irradiation (TSEI) requires large electron Beams having good dose uniformity, d max at the skin surface, and low bremsstrahlung contamination. Energy degraders and scattering foils have to be specially designed for the given accelerator and treatment room. Method and Materials:Monte Carlo(MC) techniques based on EGS4 user codes (Beam, DOSXYZ, and DOSRZ) guided the Beam Modifier design of our TSEI system. The dosimetric characteristics at the treatment distance of 382 cm 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 primary electrons were determined to be mono‐energetic at 6.72 MeV, parallel, and circular Beams having a Gaussian radial distribution with FWHM = 0.13 cm. They were then used to simulate our TSEI with eight sets of energy degraders and flattening filters. Results: An energy degrader of a 0.6 cm‐thick PMMA plate, blacking a jaw‐shaped field (40 × 40 cm2) at 100 cm SSD, showed the best performance in terms of dose rate and uniformity. A flattening filter, consisting of a 12 × 12 cm2aluminum plate of 0.6 cm‐thickness and placed just behind the energy degrader was considered optimal. Such optimized combination produced a Beam that was flat within ±3% up to 60 cm off‐axis distance, dropped by not more than 6% at a distance of 90 cm, and had an x‐ray of < 3%. The maximum dose of the rotating phantom occurred at the surface and was approximately 40% of the maximum dose (at 0.65 cm‐depth) of the stationary phantom. Conclusion: By evaluating the dosimetric performance of Beam Modifier designs for TSEI, the Monte Carlo simulations reduced the costly efforts that could, otherwise, result from constructing and measuring lots of prototypes.
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SU‐FF‐T‐282: Beam Modifier Design for Total Skin Electron Irradiations Using Monte Carlo Techniques
Medical Physics, 2005Co-Authors: Ivan A. Brezovich, Prem N. Pareek, Jun Duan, Sharon A. SpencerAbstract:Purpose: Total skin electron irradiation (TSEI) requires large electron Beams having good dose uniformity, d max at the skin surface, and low bremsstrahlung contamination. Energy degraders and scattering foils have to be specially designed for the given accelerator and treatment room. Method and Materials:Monte Carlo(MC) techniques based on EGS4 user codes (Beam, DOSXYZ, and DOSRZ) guided the Beam Modifier design of our TSEI system. The dosimetric characteristics at the treatment distance of 382 cm 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 primary electrons were determined to be mono‐energetic at 6.72 MeV, parallel, and circular Beams having a Gaussian radial distribution with FWHM = 0.13 cm. They were then used to simulate our TSEI with eight sets of energy degraders and flattening filters. Results: An energy degrader of a 0.6 cm‐thick PMMA plate, blacking a jaw‐shaped field (40 × 40 cm2) at 100 cm SSD, showed the best performance in terms of dose rate and uniformity. A flattening filter, consisting of a 12 × 12 cm2aluminum plate of 0.6 cm‐thickness and placed just behind the energy degrader was considered optimal. Such optimized combination produced a Beam that was flat within ±3% up to 60 cm off‐axis distance, dropped by not more than 6% at a distance of 90 cm, and had an x‐ray of < 3%. The maximum dose of the rotating phantom occurred at the surface and was approximately 40% of the maximum dose (at 0.65 cm‐depth) of the stationary phantom. Conclusion: By evaluating the dosimetric performance of Beam Modifier designs for TSEI, the Monte Carlo simulations reduced the costly efforts that could, otherwise, result from constructing and measuring lots of prototypes.
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Monte Carlo techniques for scattering foil design and dosimetry in total skin electron irradiations
Medical physics, 2005Co-Authors: Prem N. Pareek, Jun Duan, Sharon A. Spencer, Ivan A. BrezovichAbstract:Total skinelectron irradiation (TSEI) with single fields requires large electron Beams having good dose uniformity, d max 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 × 12 cm 2 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 d max , R p , and R 50 agreed with measurements within 0.5 mm . The MC-predicted surface dose of the rotating phantom was 41% of the dose rate at d max 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.
Abdelmajid Maghnouj - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Secondary Photons Emergent from Combined Material Slab as a Function of Slab Thickness
Moscow University Physics Bulletin, 2018Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad Tajmouati, Abdessamad DidiAbstract:Material science is very important for developing the linear accelerator. Determination and understanding of material behavior face to X-rays is a basic study for photon Beam Modifiers improvements. In this study, the 6 MV photon Beams produced by Varian Clinac 2100 was modelled by Monte Carlo simulation using Beamnrc code and thereafter the flattening filter was replaced by a slab of aluminum and copper separately and by slab of both materials combined together with different thickness of 2.5, 5, 7.5, and 10 mm. The purpose of this study is to investigate the scattered photons with thickness of combined material slab as a function of off-axis distance. The scattered photons increased with thickness of copper alone slab, combined aluminum-copper slab and copper-aluminum slab, but for aluminum alone slab they decreased with slab thickness. The stacking order of these two materials affects the characterization of scattered photons emergent from material slab with thickness. The combination of materials and the manner that the stacking was done affects the scattered photons production. The material combination could improve the radiotherapy efficiency in Beam Modifier development using more than two materials.
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Photon Beam softening coefficient determination with slab thickness in small filed size: Monte Carlo study
Physics of Particles and Nuclei Letters, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:Determination and understanding of photon Beam softening using material soften photon Beam for clinical usage is important for material study for attenuation and for Beam Modifier enhancements and linac improvements. Monte Carlo model was used to simulate 6 MeV photon Beams produced by Varian Clinac 2100 accelerator with flattening filter thereafter the flattening filter was replaced by a slab of aluminum and copper with different of 0.5, 1, 1.5 and 2 mm. The Monte Carlo geometry was validated by a gamma index acceptance rate of 99% in PDD and 98% in dose profiles, the gamma criteria was 3% for dose difference and 3mm for distance to agreement. The purpose was to investigate the Beam softening for small size and Beam attenuation as a function of inserted slab thickness of copper and aluminum and also as a function of off-axis distance. For Beam softening evaluation, variation amplitude of Beam softening coefficient a1 was very high near the Beam central axis and decreased with off-axis distance and also it was high for aluminum slab compared to copper slab. For aluminum slab, variation amplitude of Beam softening coefficient a1 have a minimum at–0.5 cm–1 and a maximum at 0.5 cm–1 and for copper slab, variation amplitude of Beam softening a1 have a minimum at–0.15 cm–1 and a maximum at 0.11 cm–1. Variation amplitude of Beam softening coefficient a2 was very high near the Beam central axis and decreased with off-axis distance and it was very high for aluminum slab compared to copper slab. For aluminum slab, variation amplitude of Beam softening coefficient a2 have a minimum at–0.54 cm–2 and a maximum at 0.44 cm–2 and for copper slab, variation amplitude of Beam softening coefficient a2 have a minimum at–0.111 cm–2 and a maximum at 0.0825 cm–2.
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Relative Attenuation and Beam Softening Study with Flattening Filter Volume Reduction: Monte Carlo Study
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:The flattening filter (FF) volume reduction increases the clinical photons for deep tumor treatment. The Beam softening determination is crucial for flattening filter improvement in geometry and materials. Determination and understanding the photon Beam properties using material and geometry of a Beam Modifier is very important for dosimetry improvement in radiotherapy department and also for patient life quality development. This Monte Carlo study aims to investigate the relative attenuation and associated Beam softening due to flattening filter volume reduction. The FF volume was reduced by 10, 20, and 30% of the initial volume data provided by the manufacturer. The relative attenuation and Beam softening coefficients increased with FF volume reduction more near the Beam central axis than the Beam edge. We have illustrated that relative photon Beam softening coefficient v was more stable than the coefficient u as a function of offaxis distance and with FF volume reduction. For increasing the photon fluence and dose delivered inside the phantom volume as mentioned in IAEA protocols, the FF volume should be reduced more near the FF top region than the FF edge region. Our work can be a basic investigation that will be used in improvement for the future linac configuration in terms of photon Beam softening for material, geometry, and volume that were used in Beam Modifiers as a flattening filter.
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Study of Possibility to Reduce Flattening Filter Volume for Increasing Energetic Photons for High Radiotherapy Efficiency
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad Tajmouati, Abdesslam Lamrabet, Yassine BenkhouyAbstract:Increasing dose for improved radiotherapy efficiency is essential for linear accelerator development and also for flattening filter geometry and material enhancement. Determination and understanding the photon Beam properties using material and geometry of a Beam Modifier is very important in radiotherapy department and also for high patient life quality. This Monte Carlo study aims to improve the FF in a linac for increasing the photon number at the entrance of treatment volume tumor and the dose delivered inside the treatment volume as recommended by the IAEA protocols. The aim of this study was to check out the possibility to reduce the flattening filter volume for improving the clinical photons at phantom surface. We have studied photon attenuation coefficients and Beam softening coefficients with FF volume reduction. The FF volume was reduced by 10, 20, and 30% of initial FF volume. The photon fluence increased with FF volume reduction near the Beam central axis than the Beam edge and the Beam softening coefficients remained apparently invariable with FF volume reduction as a function of off-axis distance. Our work can be a basic study that will be used in research and improvement for future linac configuration in terms of photon attenuation and Beam softening for a material, geometry and volume that were used for finding out good flattening and good softening to produce an optimal delivered dose as recommended by IAEA.
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Photon Beam softening coefficients evaluation for a 6 MeV photon Beam for an aluminum slab: Monte Carlo study using Beamnrc Code, DOSXYZnrc Code, and BeamDP code
Moscow University Physics Bulletin, 2017Co-Authors: Mohamed Bencheikh, Abdelmajid Maghnouj, Jaouad TajmouatiAbstract:Determination and understanding the photon Beam attenuation by the photon Beam Modifier and the radiation Beam softening for clinical use is more important part of material study for the Beam Modifier enhancements and the linac improvements. A Monte Carlo model was used to simulate 6 MeV photon Beams from a Varian Clinac 2100 accelerator with the flattening filter and the later was replaced by the aluminum slab with variable thickness. The Monte Carlo geometry was validated by a gamma index acceptance rate of 99% in PDD and 98% in dose profiles, the gamma criteria was 3% for dose difference and 3 mm for distance to agreement. The purpose was to investigate aluminum material attenuation and Beam softening coefficients as a function of the inserted aluminum slab thickness and of off-axis distance. The attenuation and Beam softening coefficients were not identical for the same off-axis distance and they varied as a function of aluminum slab thickness. The results of our study were shown that the Beam softening coefficients were varied with thickness Beam Modifier material used for Beam softening and the off-axis distance inside the irradiation field. Thereafter, the softening coefficient a 1 have a maximum of 2.5 × 10–1 cm–1 for the aluminum slab thickness of 1 mm, 1.4 × 10–1 cm–1 for the aluminum slab thickness of 1.5 mm and 4.47 × 10–2 cm–1 for the aluminum slab thickness of 2 mm. The maximum of the second softening coefficient a 2 was 1.02 × 10–2 cm–2 for the aluminum slab thickness of 1 mm, was 1.92 × 10–2 cm–2 for the aluminum slab thickness of 1.5 mm and was 1.93 × 10–2 cm–2 for the aluminum slab thickness of 2 mm. Our study can be a basic investigation of photon Beam softening material that will be used in the future linac configuration and also in the photon Beam Modifiers.