基于Geant4-DNA工具包的单能电子微剂量学模拟研究

Monoenergetic Electron Microdosimetry Simulation Based on Geant4-DNA Package

应用Geant4-DNA工具包分析和评估了不同物理过程影响因素对低能电子在液态水中的影响,为建立放射治疗与辐射防护所关心的微剂量学基本数据库提供理论支撑。在最新版本的Geant4中,Geant4-DNA工具包中共有7个物理模型可模拟电子在液态水中的输运。根据不同模型的特点,本文选择其中5个适用的模型来模拟单能入射电子(0.1~20 keV)在液态水中的输运过程;比较各模型记录的径迹结构具体信息,包括相互作用过程总次数、电离和激发次数及相应沉积能量占比等;分析Geant4-DNA选项模型、抽样位点小球半径及相互作用过程等因素对线能均值的影响。模拟结果显示:“option0”与“option2”之间、“option4”与“option5”之间的模拟结果基本吻合;由于各个模型相互作用截面的不同,“option2”、“option4”和“option6”的径迹信息及线能均值均存在差异;模型对线能均值的影响随着抽样位点小球半径的增大而减小。本工作通过设置不同输运控制条件较全面地比较了Geant4-DNA工具包中的不同选项模型,对用户根据需要选择合适的模型模拟单能电子有帮助和指导作用,为完善电子在液态水中的微剂量学数据库并用于评估电离辐射在微观尺度的生物学效应提供依据。

The influence of different physical process factors on low-energy electrons in liquid water was analyzed and evaluated using the latest Geant4-DNA package,providing theoretical support for establishing a basic database of microdosimetry concerned with radiotherapy and radiation protection.In the latest version of the package,there are 7 physical models to simulate the transport of electrons in liquid water.According to the characteristics of different models,5 suitable ones were selected to simulate the transport process of monoenergetic electrons(0.1-20 keV).The specific information of track structure recorded by each model was compared,including the total number of interaction processes,the number of ionization and excitation,and the proportion of corresponding deposition energy.Factors,such as the model option,the particle radius at sampling sites and the interaction process,were analyzed with respect to their impacts on the mean lineal energy.It shows that the simulation results between Option0 and Option2,and also,between Option4 and Option5 are basically consistent.Due to the different interaction cross sections of each model,there is difference for the track information and the mean linear energy.The influence of the model on the mean linear energy decreases with the increase of particle radius at sampling sites.The effort would be helpful and instructive for users to select the appropriate model to simulate low energy monoenergetic electrons according to their needs,and provide a powerful basis for further establishing a monoenergetic electronic database to evaluate the biological effects of ionizing radiation in microscopic scale.