补偿膜对浅表组织剂量学的GEANT4模拟研究  

GEANT4 simulation study of superficial tissue dosimetry with bolus

作　　者：王君辉 刘福友 刘海涛[1] 吴建亭[1] 金建华[1] 储开岳[1] WANG Jun-hui;LIU Fu-you;LIU Hai-tao;WU Jian-ting;JIN Jian-hua;CHU Kai-yue(Department of Radiotherapy,Nantong Cancer Hospital,Cancer Hospital Affiliated to Nantong University,Nantong 226361,Jiangsu,China)

机构地区：[1]南通市肿瘤医院放疗科·南通大学附属肿瘤医院,江苏南通226361

出　　处：《生物医学工程与临床》2021年第1期15-18,共4页Biomedical Engineering and Clinical Medicine

基　　金：江苏省重点研发计划项目(BE2017679);南通市指导性计划项目(GJZ17043)。

摘　　要：目的研究不同补偿膜厚度及不同空气间隙大小对浅表组织剂量学影响。方法利用蒙特卡罗程序“几何和跟踪”(GEANT4)构建位于加速器等中心的30 cm×30 cm×30 cm水模体及30 cm×30 cm×d cm(d为0.5、1.0、2.0)组织(水)等效补偿膜,通过改变等效补偿膜与水模体空气间隙至0 mm、1 mm、5 mm、10 mm、15 mm、20 mm设计不同的贴合模型,计算6 MV X射线10 cm×10 cm射野下不同模型水模体中心轴深度剂量分布和水模体表面(1 mm、2 mm、3 mm、4 mm、5 mm)的能量沉积。结果空气间隙≤5 mm时,对浅表的能量沉积误差小于1%;空气间隙≤10 mm,对于浅表深度≥1 mm时能量沉积误差小于1%;空气间隙>10 mm,添加任何厚度补偿膜对于浅表的能量沉积误差都较大,甚至>3%。结论摆位时应尽量减少补偿膜下空气间隙,补偿膜厚度越大时,空气间隙大小对其影响越大,模拟结果对于组织等效补偿膜的临床应用具有指导价值。Objective To study effects of different bolus thickness and different air gap sizes on dosimetry of superficial tissues.Methods The Monte Carlo code GEometry and Tracking 4(GEANT4)was used to construct 30 cm×30 cm×30 cm water phantom and 30 cm×30 cm×d cm(d=0.5,1.0,2.0)tissue(water)bolus at accelerator isocenter.Different fitting models were designed to be changed from 0 mm to 1 mm,5 mm,10 mm,15 mm and 20 mm by equivalent bolus and air gap of water phantom.The depth dose distribution of different water phantom models at 6 MV X-ray 10 cm×10 cm field and energy deposition on water phantom surface(1 mm,2 mm,3 mm,4 mm and 5 mm)were calculated.Results The energy deposition error for superficial surfaces was less than 1%in air gap≤5 mm;the energy deposition error for superficial surfaces was 1%in air gap≤10 mm.Any thickness of the bolus added would increase energy deposition error for superficial surfaces,and it was even>3%when air gap>10 mm.Conclusion It is demonstrated that air gap at bolus should be reduced,the thicker the bolus thickness,the greater the air gap impact,the simulation results provides guidance for clinical application of tissue equivalent bolus.

关 键 词：GEANT4 组织等效补偿膜 空气间隙 表面剂量 模拟实验 

分 类 号：R730.55[医药卫生—肿瘤]