医用加速器输出剂量长期稳定性分析

Long-term stability analysis on output dose of medical accelerator

目的:分析医用加速器输出剂量长期稳定性及其影响因素。方法:按照IAEA TRS 277技术报告,对武警四川省总队医院医用加速器进行吸收剂量测量,统计分析2012年5月~2017年12月共计240组输出剂量数据,分析医用加速器输出剂量长期稳定性及其影响因素,为加速器剂量质量保证提供方法与措施。结果:6 MV-X输出剂量3组数据K-S检验双尾渐进概率P值分别为0.101、0.269、0.549,均大于显著性水平0.05,符合标准正态分布,且P值逐渐增大,符合程度越来越好;剂量误差≤1%符合率达到91.94%,剂量误差≤2%符合率达到97.92%。结论:武警四川省总队医院医用加速器输出剂量具有很好的正态性和长期稳定性,完全能够满足临床放疗需求;影响加速器输出剂量稳定性的主要因素有加速器硬件自身稳定性、剂量仪电离室稳定性、剂量测量方法准确性、摆位误差等;物理师应按照科室实际情况,制定个体化的加速器剂量质量保证程序,并按照规定频次校准输出剂量,监测输出剂量的稳定性,为精准放疗提供有力保障。

Objective To analyze the long-term stability of the output dose of medical accelerator and discuss its influencing factors.Methods According to IAEATRS 277 report,the absorbed dose measurement was performed on medical accelerators in Sichuan Provincial Corps Hospital of Chinese People's Armed Police Forces,and a total of 240 groups of output dose data from May 2012 to December 2017 were statistically analyzed.The long-term stability of the output dose of medical accelerator and its influencing factors were analyzed for providing methods and measures for the dose quality assurance of medical accelerator.Results The K-S test on 3 groups of 6 MV-X output doses showed that two-tailed progressive probability P values were 0.101,0.269,and 0.549,respectively,which were all greater than the significance level of 0.05 and accord with the standard normal distribution.The P value was gradually increased,and the degree of coincidence was also gradually increased.Moreover,the coincidence rates of dose error≤1%and≤2%were 91.94%and 97.92%,respectively.Conclusion The output dose of the medical accelerator in Sichuan Provincial Corps Hospital of Chinese People's Armed Police Forces has good normality and long-term stability,and can fully meet the needs of clinical radiotherapy.The main factors that affect the stability of the output dose of accelerator includes the self stable of accelerator hardware,the stable of dosimeter and ionization chamber,the accuracy of measurement method and setup errors,etc.Physicists should formulate an individualized accelerator dose quality assurance procedure according to the actual situation of the department,and calibrate the output dose according to the specified frequency,and monitor the stability of the output dose,thereby providing a guarantee for precision radiotherapy.