射波刀图像引导系统额外吸收剂量评估

摘要

目的 定量评价G3型射波刀图像引导系统千伏级X线球管照射产生的额外电离辐射吸收剂量.方法 将PTW30010电离室插入CIRS Model 002LFC和002PRA体模不同位置、不同密度各5处组织等效模体插件中,测量不同曝光条件下单次曝光所产生的吸收剂量.通过以上数据定量评估300例不同部位、不同引导方式患者的曝光条件和平均曝光次数以及吸收剂量.结果 平均分割治疗次数为3.94次,中位数4次.采用静态追踪模式患者平均每位每次分割治疗接受曝光次数为36.5次,采用动态追踪模式时为49.2次.单次曝光最小吸收剂量为0.5 μGy,最大为385μGy.结论 射波刀的千伏级图像引导系统在实现3种图像引导功能的同时,对患者产生额外吸收剂量保持在一个很低范围内.%Objective To evaluate quantitatively the extra absorbed dose generated by image guided system of the Cyberknife.Methods The exposure parameters and the average frequency of images acquisition during the treatments with G3 Cyberknife in 300 cases with various tumor locations and tracking modes were collected for analysis ;The measurements of the absorbed doses in the phantom with 5 points after single exposure generated by image guided system in various exposure parameters were performed with equipment of phantom CIRS Model 002LFC and 002 PRA with ion chamber PTW30010 included.Based on the data we collected andmeasured,the conclusion of how much extra absorbed dose generated by image guided system of Cyberknife the patients received during Cyberknife treatments was drawn.Results With an average fractions of 3.94(the median was 4),the average exposure frequency was 36.5 times for static tracking per patient per fraction,while it was 49.2 times for dynamic tracking.The experimental results with various exposure parameters,positions and tissue densities showed that the minimum absorbed dose after single exposure was 0.5 μGy,while the maximum was 385 μGy.Conclusions The image guided system of the Cyberknife can induce quite low absorbed dose in patient,while providing all three types of image guided function.