Gafchromic EBT3胶片在螺旋断层放射治疗计划验证中的应用  

Application of Gafchromic EBT3 film in the verification of TomoTherapy plan

作　　者：蔡汉飞[1,2] 方美芳 徐露 梁保辉 曹露[1] 葛文洁 CAI Hanfei;FANG Meifang;XU Lu;LIANG Baohui;CAO Lu;GE Wenjie(Department of Radiation Oncology,the First Affiliated Hospital of Bengbu Medical College,Bengbu 233004,China;Department of Medical Imaging,Bengbu Medical College,Bengbu 233030,China)

机构地区：[1]蚌埠医学院第一附属医院肿瘤放疗科,安徽蚌埠233004 [2]蚌埠医学院医学影像系,安徽蚌埠233030

出　　处：《中国医学物理学杂志》2018年第11期1257-1260,共4页Chinese Journal of Medical Physics

基　　金：蚌埠医学院科技发展基金项目(BYKF1773)

摘　　要：目的:评估基于Gafchromic EBT3胶片的剂量测量系统用于螺旋断层放射治疗计划验证的可靠性,确定该系统的正确使用方法。方法:使用Gafchromic EBT3胶片和Vidar Dosimetry Pro Advantage Red扫描仪组成的剂量测量系统,测试并确定系统的一些重要特性对测量结果的影响。此外,使用该系统验证螺旋断层放射治疗计划,借助Gamma指数分析对胶片测量的剂量分布与计划系统计算结果之间进行比较。结果:胶片辐照后一开始透光度随时间变化比较明显,直到约4 h以后胶片着色渐趋饱和,4 h内扫描值变化最高达11.6%。扫描仪扫描重复性相对标准差小于0.5%。胶片正反方向放置扫描结果之间差别小于0.6%、横向和纵向放置扫描结果之间差别最高达7.0%。Gamma参数设置为3%/3 mm时,横向和纵向放置扫描验证平均通过率分别为96.5%±2.9%和95.7%±3.6%,方差分析显示两种扫描方式的验证通过率在a=0.05水平上没有统计学差异。结论:使用文中的胶片剂量测量系统时,应居中放置扫描,并使验证胶片和刻度胶片保持相同的扫描方向。通过直接建立扫描值与胶片吸收剂量之间的一一对应关系,将验证胶片的扫描值转换成吸收剂量的方法简便易行。Objective To evaluate the reliability of applying Gafchromic EBT3 film-based dosimetry system for the verification of TomoTherapy plan,and to validate the correct usage of the system.Methods The film dosimetry system is composed of Gafchromic EBT3 film and Vidar DosimetryPro Advantage Red scanner.The most important characteristics of the system were investigated to determine the main influencing factors.The system was used to verify TomoTherapy plan,and the comparison of the calculated and measured dose distributions was performed using Gamma index analysis.Results The transmittance changed with time obviously after irradiation until about 4 hours later when the coloration was nearly saturated.The largest difference of scan values within 4 hours was up to 11.6%.The relative standard deviation of the repeatability of scanner was less than 0.5%.The differences of scan values between film in face-up and face-down positions were less than 0.6%,while the largest difference of scan values between landscape and portrait orientations was up to 7.0%.The Gamma analysis with a criterion of 3%/3 mm showed that the average passing rates of landscape and portrait orientations were 96.5%±2.9%and 95.7%±3.6%,respectively.Analysis of variance showed that there is no statistical difference between both orientations(a=0.05).Conclusion When using a film dosimetry system as discussed in this research,the film should be placed in the center of scanning area,and verification film and calibration film should be maintained at the same scan direction.By directly establishing one-to-one correspondence between the scan values and the absorbed doses of film,it is easy and feasible to convert the scan values of the verification film into absorbed doses.

关 键 词：Gafchromic EBT3胶片 螺旋断层放射治疗 放射治疗计划验证 Gamma指数分析 

分 类 号：R812[医药卫生—放射医学]