Mapcheck的剂量学质量保证

目的:评价我中心新购美国Sun Nuclear公司生产二维半导体阵列Mapcheck的剂量学特点。方法:使用美国瓦里安公司23EX直线加速器高能光子束照射Mapcheck研究其重复性,线性以及验证其本身阵列校准方法的准确性;同时在研究其重复性,脉冲率依赖性及输出因子时使用德国PTW30013电离室测量数据并比较。结果:实施Mapcheck专用阵列校准方法后在0o和180o测量结果差异介于-0.5%至0.7%之间。矩阵重复性最大标准差是±0.16%,中心轴半导体探头(C点)12次测量标准差为0.065%。中心探头随剂量率变化最大范围是0.78%。同指形电离室结果比较,小于4cm×4cm射野时,Mapcheck低估了输出因子最大达1.1%,大于15cm×15cm射野时,Mapcheck开始高估输出因子最大达0.9%。结论:Mapcheck的各项剂量学检测结果符合出厂指标,适合应用于临床作常规射野剂量学质量保证及调强剂量学验证。

Dosimetric Quality Assurance for Mapcheck

Objective： To evaluate the dosimetric characteristics of the Mapcheck made by Sun Nuclear Cooperation in USA. Methods： High energy photon （produced by Varian 23EX ） was used to study its repetition ,linearity ,the dependence of dose rate,the output factor of the center diode and the correction of the array calibration. The ion chamber was also used in the study of the repetition,the dependence of dose rate ,the output factor of the center diode. Results： The dosimetic difference of diodes for array calibration was between -0.5% to 0.7%. The Mapcheck readings were reproducible to within a maximum SD of ± 0.16% while the center was to 0.065%. The maximum dose rate dependence of 0.78% was also noted .Compared with the ion chamber, Mapcheck underestimated the output factor to 1.1% in the field smaller than 4cm by 4cm while overestimated to 0.9% in those larger than 15 cm by 15 cm. Conclusion： The measured dosimetric results of the Mapcheck was coinsistent with the parameters supplied by the manufacturer. It＇s use in the clinic was reasonable for conventional field QA and IMRT dosimetric QA.