高剂量率铱源剂量学特征的蒙特卡罗模拟研究

Dosimetric Characteristics Study on the Ir-192 High Dose Rate by Monte Carlo Simulation

目的采用蒙特卡罗模拟技术,借助程序MCNP5对国产高剂量率铱源剂量率的分布进行模拟研究。方法基于TG43号报告中的剂量率计算公式,借助MCNP5建立铱源模型,模拟计算此模型的空间剂量分布,分析研究铱源的径向剂量函数及各向异性函数。结果模拟的各向异性函数与发表结果在误差范围内一致。当径向距离较小时,模拟的径向剂量函数与发表结果符合较好;当径向距离较大时,模拟的径向剂量函数与部分发表结果符合较好,但也与部分发表结果相差较大,在r=15 cm处,最大相对误差为24%。结论基于MCNP5的蒙特卡罗模拟技术可较好地模拟研究国产高剂量率铱源的剂量学特征,这为进一步探索影响后装放疗剂量分布的因素奠定了理论基础。

Objective To simulate the dose rate distribution of domestic high dose rate Ir-192 with the help of the program MCNP5 using Monte Carlo simulation technology.Methods Based on TG43 protocol,the Ir-192 modelling was established through MCNP5 code.At then,the distribution of dose rate in space was simulated with this modeling.From the simulation,the radial dose function and anisotropy function were obtained.Results The simulated anisotropy function was in agreement with the published results within the error range.When the radial distance was small,the radial dose function agreed with each other in the small radial distance;for the big radial distance,the radial dose function was only agree with some published results.The largest relative difference was 24%at radial distance 15 cm.Conclusion The Monte Carlo technique based on MCNP5 can better simulate the dosimetry characteristics of domestic high-dose rate iridium source,which lays a theoretical foundation for further exploring the factors affecting the dose distribution of radiotherapy after loading.