skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SU-E-T-08: A Beam Source Model for Monte Carlo Simulations of a Double-Scattering Proton Beam Delivery System Using Beam Current Modulation

Abstract

Purpose: To reconstruct phase-space information upstream of patient specific collimators for Monte Carlo simulations using only radiotherapy planning system data. Methods: The proton energies are calculated based on residual ranges, e.g., sum of prescribed ranges in a patient and SSD. The Kapchinskij and Vladimirskij (KV) distribution was applied to sample proton’s x-y positions and momentum direction and the beam shape was assumed to be a circle. Free parameters, e.g., the initial energy spread and the emittance of KV distribution were estimated from the benchmarking with commissioning data in a commercial treatment planning system for an operational proton therapy center. The number of histories, which defines the height of individual pristine Bragg peaks (BP) of Spread-out Bragg peak (SOBP), are weighted based on beam current modulation and a correction factor is applied to take into account the fluence reduction as the residual range decreases due to the rotation of the range modulator wheel. The timedependent behaviors, e.g., the changes of the residual range and histories per a pristine BP, are realized by utilizing TOPAS (Tool for Particle Simulation). Results: Benchmarking simulations for selected SOBPs ranging 7.5 cm to 15.5 cm matched within 2 mm in range and up to 5 mmmore » in SOBP width against measurement data in water phantom. We found this model tends to underestimate entrance dose by about 5 % in comparison to measurement. This was attributed to the situation that the energy distribution used in the model was limited in its granularity at the limit of single energy spectrum for the narrow angle modulator steps used in the proximal pull back region of the SOBPs. Conclusion: Within these limitations the source modeling method proved itself an acceptable alternative of a full treatment head simulation when the machine geometry and materials information are not available.« less

Authors:
; ; ; ; ;
Publication Date:
OSTI Identifier:
22545143
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; BEAM CURRENTS; BRAGG CURVE; COMPUTERIZED SIMULATION; ENERGY SPECTRA; MODULATION; MONTE CARLO METHOD; PATIENTS; PHANTOMS; PHASE SPACE; PROTON BEAMS; RADIOTHERAPY; WIDTH

Citation Formats

Shin, J, Merchant, T E, Lee, S, Li, Z, Shin, D, and Farr, J B. SU-E-T-08: A Beam Source Model for Monte Carlo Simulations of a Double-Scattering Proton Beam Delivery System Using Beam Current Modulation. United States: N. p., 2015. Web. doi:10.1118/1.4924369.
Shin, J, Merchant, T E, Lee, S, Li, Z, Shin, D, & Farr, J B. SU-E-T-08: A Beam Source Model for Monte Carlo Simulations of a Double-Scattering Proton Beam Delivery System Using Beam Current Modulation. United States. doi:10.1118/1.4924369.
Shin, J, Merchant, T E, Lee, S, Li, Z, Shin, D, and Farr, J B. Mon . "SU-E-T-08: A Beam Source Model for Monte Carlo Simulations of a Double-Scattering Proton Beam Delivery System Using Beam Current Modulation". United States. doi:10.1118/1.4924369.
@article{osti_22545143,
title = {SU-E-T-08: A Beam Source Model for Monte Carlo Simulations of a Double-Scattering Proton Beam Delivery System Using Beam Current Modulation},
author = {Shin, J and Merchant, T E and Lee, S and Li, Z and Shin, D and Farr, J B},
abstractNote = {Purpose: To reconstruct phase-space information upstream of patient specific collimators for Monte Carlo simulations using only radiotherapy planning system data. Methods: The proton energies are calculated based on residual ranges, e.g., sum of prescribed ranges in a patient and SSD. The Kapchinskij and Vladimirskij (KV) distribution was applied to sample proton’s x-y positions and momentum direction and the beam shape was assumed to be a circle. Free parameters, e.g., the initial energy spread and the emittance of KV distribution were estimated from the benchmarking with commissioning data in a commercial treatment planning system for an operational proton therapy center. The number of histories, which defines the height of individual pristine Bragg peaks (BP) of Spread-out Bragg peak (SOBP), are weighted based on beam current modulation and a correction factor is applied to take into account the fluence reduction as the residual range decreases due to the rotation of the range modulator wheel. The timedependent behaviors, e.g., the changes of the residual range and histories per a pristine BP, are realized by utilizing TOPAS (Tool for Particle Simulation). Results: Benchmarking simulations for selected SOBPs ranging 7.5 cm to 15.5 cm matched within 2 mm in range and up to 5 mm in SOBP width against measurement data in water phantom. We found this model tends to underestimate entrance dose by about 5 % in comparison to measurement. This was attributed to the situation that the energy distribution used in the model was limited in its granularity at the limit of single energy spectrum for the narrow angle modulator steps used in the proximal pull back region of the SOBPs. Conclusion: Within these limitations the source modeling method proved itself an acceptable alternative of a full treatment head simulation when the machine geometry and materials information are not available.},
doi = {10.1118/1.4924369},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}