基于微剂量学的钆中子俘获治疗释放低能电子相对生物效应计算

Computation of relative biological effectiveness of low-energy electrons release in gadolinium neutron capture therapy based on microdosimetry

目的基于微剂量学方法计算钆中子俘获治疗(157GdNCT)中释放低能电子的相对生物效应(RBE)值。方法使用蒙特卡罗(MC)程序Geant4-DNA包模拟钆中子俘获治疗中释放的低能电子在不同敏感靶标体积和物理模型中径迹结构的能量沉积分布情况及微剂量学参数,并基于微剂量动力学模型(MKM)获取其RBE值。结果低能电子RBE值在不同的敏感靶标体积下差异性较大,且随着敏感靶标体积增大而减小。以敏感靶标直径6 nm的RBE值1.77为参考,敏感靶标直径10 nm的RBE值1.53,相比于6 nm的差异百分比为13%,而直径15 nm的RBE值1.40,相比于6 nm的差异百分比高达21%。不同Geant4-DNA物理模型对低能电子RBE影响较小。以物理模型option2的RBE值1.53作为参考,option6和option7的RBE值分别为1.49和1.52,相比于option2的差异百分比分别为2.6%和0.6%。结论利用MKM计算157GdNCT释放低能电子在不同敏感靶标体积及物理模型下的RBE值为1.40~1.77。

Objective To calculate the relative biological effectiveness(RBE)value of the released low-energy electrons in gadolinium neutron capture therapy(157GdNCT)based on microdosimetry.Methods The Monte Carlo(MC)code Geant4-DNA package was used to simulate the energy deposition distribution and microdosimetry parameters of low-energy electrons released during gadolinium neutron capture treatment in different sensitive target volumes and physical models on track structures.On this basis,RBE value was obtained based on the microdosimetry kinetic model(MKM).Results The low-energy electron RBE value was highly variable in different sensitive target volumes and decreases with increasing sensitive target volumes.With 6-nm-diameter sensitive target as reference,RBE value was 1.77 for 6-nm diameter,1.53 for 10 nm diameter with percentage difference 13%,and 1.40 for 15-nm diameter with percentage difference of 21%,respectively.The effect of different Geant4-DNA physical models on the RBE of low-energy electrons was small.Using the RBE value of 1.53 for physical model option2 as reference,the RBE values of option6 and option7 were 1.49 and 1.52,respectively,with the percentage differences of 2.6%and 0.6%,respectively.Conclusions The RBE values of low energy electrons released by 157GdNCT in different sensitive target volumes and physical models were calculated by MKM to be 1.40-1.77.