Abstract:
Objective.This study aims to investigate the biological effectiveness of Spread-Out Bragg-Peak (SOBP) proton beams with initial kinetic energies 50-250 MeV at different depths in water using TOPAS Monte Carlo code.Approach.The study modelled SOBP proton beams using TOPAS time feature. Various LET-based models and Repair-Misrepair-Fixation model were employed to calculate Relative Biological Effectiveness (RBE) for V79 cell lines at different on-axis depths based on TOPAS. Microdosimetric Kinetic Model and biological weighting function-based models, which utilize microdosimetric distributions, were also used to estimate the RBE. A phase-space-based method was adopted for calculating microdosimetric distributions.Main results.The trend of variation of RBE with depth is similar in all the RBE models, but the absolute RBE values vary based on the calculation models. RBE sharply increases at the distal edge of SOBP proton beams. In the entrance region of all the proton beams, RBE values at 4 Gy i.e. RBE(4 Gy) resulting from different models are in the range of 1.04-1.07, comparable to clinically used generic RBE of 1.1. Moving from the proximal to distal end of the SOBP, RBE(4 Gy) is in the range of 1.15-1.33, 1.13-1.21, 1.11-1.17, 1.13-1.18 and 1.17-1.21, respectively for 50, 100, 150, 200 and 250 MeV SOBP beams, whereas at the distal dose fall-off region, these values are 1.68, 1.53, 1.44, 1.42 and 1.40, respectively.Significance.The study emphasises application of depth-, dose- and energy- dependent RBE values in clinical application of proton beams.
摘要:
目的:本研究旨在利用TOPAS蒙特卡洛代码研究初始动能为50-250MeV的扩散布拉格峰(SOBP)质子束在水中不同轴上深度的生物有效性。
方法:本研究使用TOPAS时间特征对SOBP质子束进行建模。采用各种基于LET的模型和修复-误修-固定模型来基于TOPAS计算V79细胞系在不同深度的相对生物学有效性(RBE)。微剂量动力学模型和基于生物加权函数的模型,利用微剂量分布,也用于估计RBE。
结果:所有RBE模型的RBE随深度的变化趋势相似,但是RBE的值对计算模型很敏感。RBE在SOBP质子束的远端边缘处急剧增加。对于所研究的质子束,在入口区域,RBE在1.04-1.07的范围内,其与临床使用的通用RBE值1.1相当。从SOBP的近端到远端,对于50、100、150、200和250MeVSOBP梁,RBE(4Gy)分别在1.15-1.33、1.13-1.21、1.11-1.17、1.13-1.18和1.17-1.21的范围内。而在远端剂量下降区域,RBE值分别为1.68、1.53、1.44、1.42和1.40。对于上述光束。RBE(2Gy)高于相应的RBE(4Gy)值。
结论:该研究揭示了应用深度的重要性-质子束临床应用中的剂量和能量依赖性RBE值。
.