基于蒙特卡罗模拟散射效应和异质性对高剂量率192Ir近距离治疗剂量分布的影响  

Scatter and heterogeneity effects on dose distribution of high dose rate 192 Ir brachytherapy by Monte Carlo simulation

作　　者：李磊 陈斌 陈仁金 杨波 LI Lei;CHEN Bin;CHEN Renjin;YANG Bo(Department of Oncology,the Affiliated Hospital of Southwest Medical University,Sichuan Luzhou 646000,China;Medicine&Engineering&Informatics Fusion and Transformation Key Laboratory of Luzhou City,Sichuan Luzhou 646000,China)

机构地区：[1]西南医科大学附属医院肿瘤科,四川泸州646000 [2]医工医信融合与转化医学泸州市重点实验室,四川泸州646000

出　　处：《现代肿瘤医学》2024年第3期508-513,共6页Journal of Modern Oncology

基　　金：四川省科技计划项目(编号:2020JDTD0036);医工医信融合与转化医学泸州市重点实验室项目(编号:XGY202105);四川省医学科研课题计划(编号:S19007)。

摘　　要：目的:探究散射效应和异质性对高剂量率192Ir近距离治疗剂量分布的影响。方法:用MCNP5蒙特卡罗方法模拟Flexisource HDR192Ir放射源的TG-43剂量学参数:剂量率常数Λ、径向剂量函数g(r)、各向异性函数F(r,θ)。基于临床分别构建身体围度差异、偏心、浅表三种非完全散射和组织成分差异、肺插植、腔道插植三种异质性的简化模型,分别计算放射源的径向剂量分布,并通过比较各简化模型和标准模型的同点径向剂量的偏差来评价散射效应和异质性对剂量分布的影响。结果:Λ、g(r)和F(r,θ)模拟值和TPS数据的偏差均小于1%;非完全散射:TPS高估2 cm、5 cm、10 cm处的真实剂量可达约4%、14.8%、16.4%;皮质骨:TPS高估2 cm、5cm、10 cm处的真实剂量约0.7%、1.14%、10%;肿瘤介质:TPS高估真实剂量平均约1.1%;肺介质:TPS高估0.5 cm~6 cm内的真实剂量平均约1.80%,低估6 cm~15 cm内的真实剂量平均约7.77%;肺插植:半径1 cm肿瘤,TPS高估0.5 cm~8 cm内的真实剂量平均约4%,低估8 cm~15 cm内的真实剂量平均约7.8%;腔道插植:半径为1 mm、4 mm、8 mm腔道,TPS低估真实剂量平均约0.75%、1.30%、2.48%。结论:忽略散射效应和异质性会引入显著的剂量误差。临床治疗时,校正患者真实的剂量分布是必要的。Objective:To investigate the effects of scatter and heterogeneity on dose distribution of high dose rate 192 Ir brachytherapy.Methods:To simulate the TG-43 dosimetry parameters of Flexisource HDR 192 Ir radioactive source by MCNP5 Monte Carlo code,which include dose rate constantΛ,radial dose function g(r)and anisotropy function F(r,θ).Simplified models of body circumference difference,tumor on side of body,superficial radiotherapy,tissue component difference,lung implantation and luminal implantation were modeled based on clinic.The radial dose distribution of radioactive sources was calculated respectively.The effects of scatter and heterogeneity on dose distribution were evaluated by comparing the deviations of doseat the same point as the standard model.Results:The deviation between MC values of TG-43 dosimetry parameters and TPS datas was less than 1%.Insufficient scattering:TPS would overestimate real dose at 2 cm,5 cm and 10 cm about 4%,14.8%and 16.4%.Cortical bone:TPS would overestimate real dose at 2 cm,5 cm and 10 cm about 0.7%,1.14%and 10%.Tumor tissue:TPS would overestimate real dose by an average of 1.1%.Lung:TPS would overestimate real dose of 0.5 cm to 6 cm by an average of 1.8%,and underestimate real dose of 6 cm to 15 cm by an average of 7.77%.Lung implantation:TPS would overestimate real dose of 0.5 cm to 8 cm by an average of 4%,and underestimate real dose of 8 cm to 15 cm by an average of 7.8%.Luminal implantation:for 1 mm,4 mm and 8 mm radius air cavity,TPS underestimated real dose about 0.75%,1.30%and 2.48%on average.Conclusion:Ignoring scatter and heterogeneity can lead to significant errors in dose delivered to patients.It is necessary to correct the real dose delivered to patients in clinic.

关 键 词：192IR 近距离治疗 蒙特卡罗 剂量学 

分 类 号：R730.55[医药卫生—肿瘤]