聚苯乙烯掺入ZrO2的水等效性蒙特卡罗模拟研究

Water-equivalence of ZrO2 doped polystyrene by Monte Carlo simulation

目的 设计具有水等效性的塑料闪烁体探测器，用于肿瘤放射治疗中的吸收剂量测量。方法 根据经验公式估算出水等效性的聚苯乙烯材料中掺入ZrO2的浓度，利用蒙特卡罗程序Geant4（GEometry And Tracking 4）模拟不同能量的X射线在水、固体水RW34（由2.1 wt%的TiO2掺聚苯乙烯组成）和聚苯乙烯材料中掺入不同浓度ZrO2粒子的能量沉积和输运过程，比较不同材料和水中在不同深度的剂量和衰减系数。结果 聚苯乙烯中掺入约为0.4 wt% ZrO2纳米粒子构建的复合材料在不同深度处的剂量和衰减系数更接近水，其水等效性甚至优于RW34。结论 模拟结果为研制具有水等效性的闪烁体提供了依据。

Objective To design water-equivalent plastic scintillator detector for the measurement of absorbed dose in tumor radiotherapy. Methods The concentration of ZrO2 to be doped in polystyrene was estimated according to the empirical formula, and then the Monte Carlo program Geant4 （GEometry And Tracking 4） was used to simulate the energy deposition and transport process of X-rays with different energies in water, solid water RW34 （composed of 2.1 wt% TiO2 doping polystyrene） and different concentrations of ZrO2 particles doped in polystyrene. The dose and attenuation coefficients were compared among different materials at different depths of water. Results The doses at different depths and the attenuation coefficient of polystyrene （doped with about 0.4 wt% ZrO2 nanoparticles） were much more consistent with those of water and even exhibit much better water-equivalence than RW34. Conclusions The simulation results provide the basis for the development of water-equivalent scintillator.