Chattaraj Arghya, Selvam T Palani
Radiological Physics and Advisory Division, Health, Safety and Environment Group, Bhabha Atomic Research Centre, Mumbai-400 085, India.
Homi Bhabha National Institute, Anushaktinagar, Mumbai-400 094, India.
Biomed Phys Eng Express. 2024 Mar 8;10(3). doi: 10.1088/2057-1976/ad2b02.
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.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.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.The study emphasises application of depth-, dose- and energy- dependent RBE values in clinical application of proton beams.
本研究旨在使用TOPAS蒙特卡罗代码，研究初始动能为50-250 MeV的扩展布拉格峰（SOBP）质子束在水中不同深度处的生物效应。该研究利用TOPAS时间特性对SOBP质子束进行建模。采用了各种基于传能线密度（LET）的模型和修复-错配-固定模型，以基于TOPAS计算不同轴上深度处V79细胞系的相对生物效应（RBE）。还使用了基于微剂量动力学模型和生物加权函数的模型（利用微剂量分布）来估计RBE。采用基于相空间的方法计算微剂量分布。所有RBE模型中，RBE随深度的变化趋势相似，但绝对RBE值因计算模型而异。RBE在SOBP质子束的远端边缘急剧增加。在所有质子束的入射区域，4 Gy时不同模型产生的RBE值，即RBE(4 Gy)，在1.04-1.07范围内，与临床使用的通用RBE值1.1相当。从SOBP的近端向远端移动时，对于50、100、150、200和250 MeV的SOBP束，RBE(4 Gy)分别在1.15-1.33、1.13-1.21、1.11-1.17、1.13-1.18和1.17-1.21范围内，而在远端剂量下降区域，这些值分别为1.68、1.53、1.44、1.42和1.40。该研究强调在质子束临床应用中应用与深度、剂量和能量相关的RBE值。
