摘要目的 采用美国医学物理师学会(AAPM)和欧洲放射治疗和肿瘤学会(ESTRO)推荐的蒙特卡罗方法对瓦里安GammaMed Plus HDR 192 Ir源的剂量学参数进行模拟研究.方法 基于EGSnrc蒙特卡罗软件,建立该型号192 Ir源精确的计算模型.采用公式推导、双线性插值及单位转换等方法,分别得到了单位活度空气比释动能强度、 剂量率常数、 径向剂量函数以及各向异性函数,并将结果与文献报道数据进行分析比较.结果 研究得到的单位活度空气比释动能强度为9.781×10-8 U/Bq,剂量率参数为1.113 cGy·h-1·U-1,与文献报道的相差在0.4％以内.本研究的径向剂量函数、各向异性函数与文献数据能较好吻合.结论 基于EGSnrc蒙特卡罗软件能对192 Ir源剂量学特性进行定量研究,这将为进一步研究后装剂量分布,精确评价临床放疗剂量提供理论依据.

abstractsObjective To study the dosimetric parameters of Varian GammaMed Plus HDR 192 Ir source via Monte Carlo ( MC ) method based on the recommendation of the American Association of Physicist in Medicine ( AAPM) and European Society for Radiotherapy and Oncology ( ESTRO) . Methods Using the Monte Carlo program EGSnrc, an accurate model of 192 Ir source for MC calculations was establish firstly. Through formula derivation, bilinear interpolation and unit conversion, the air kerma strength per unit source activity, the dose rate constant, radial dose function and anisotropy function was obtained then , and compare the result with those in other published studies. Results The air kerma strength per unit source activity was 9. 781 × 10-8 U/Bq. The dose rate constant was 1. 113 cGy · h-1 · U-1 , with a discrepancy of less than 0. 4％ compared with result published in other works. Furthermore, the curves of radial dose function and anisotropy function overall agree with the data shown in the literature. Conclusions The feasibility of performing dosimetric studies of 192 Ir source using the MC software EGSnrc was demonstrated. This work provides a theoretical guidance on analysis of the dose distribution of brachytherapy and on evaluation of the dose accuracy of clinical radiotherapy.