直线加速器日质控数据分析及过程评估

目的 应用统计过程控制方法对加速器日质控(QC)数据进行分析,并对使用晨检仪的QC过程进行评估。方法 加速器、晨检仪校准后分别收集由技师、物理师摆位的100组、30组QC数据,设备第2次校准后再次收集技师摆位的QC数据100组,分析两次校准后技师摆位数据(各100组)的归一化信噪比的变化规律。使用由技师和物理师摆位的QC数据(各30组)绘制控制图,比较中心线位置和上下控制线范围的不同。计算由技师、物理师摆位的3个组日QC的过程能力指数。结果 两次校准的技师摆位数据归一化信噪比均为前6周变化较大,6~8周后趋于稳定,8周后逐渐变小。物理师摆位的QC数据在输出量一致性方面,上下控制线范围更窄;在平坦度、对称性方面,中心线更接近目标值0。对输出量一致性、平坦度方面,3个组日QC的过程能力指数均满足≥1要求;对称性Transverse方向均不满足。结论 应采用30~40个数据点绘制加速器日QC过程的控制图。QC过程应由相对固定且较少的QC人员完成,检测项目也应设置更适合的容差。

Daily quality control data analysis and process evaluation of linear accelerator

Objective To analyze the quality control data of linear accelerator detected by Daily QA3 and to evaluate this quality control process using statistical process control.Methods After the calibrations of the accelerator and Daily QA3,Daily QA3 device was used to perform daily quality control by technicians and physicists and 100 groups and 30 groups of daily quality control data were collected. After the accelerator and Daily QA3 were re-calibrated,Daily QA3 device was utilized to perform daily quality control by technicians and 100 groups of the daily quality control data were repeatedly collected. The variations of normalized signal-to-noise ratio of quality control data collected after two calibrations were analyzed. The first 30 groups of daily quality control data measured by technicians and physicists were adopted to calculate the I-MR control chartsand compare the location of CL and the range of UCL and LCL. The process capability indices were calculated for three different quality control processes bytechnicians and physicists, respectively.Results For twice calibrations,normalized signal-to-noise ratio of quality control data significantly changed before 6 weeks, became stable between 6 and 8 weeks,and the changes became smaller after 8 weeks. For dose output measured by physicists,the rang of UCL and LCL was more narrow. In terms of flatness and symmetry,the location of CL was closer to zero. Regarding dose output and flatness,the process capability indices of three different quality control process were all satisfied ≥1,whereas unsatisfied for transverse symmetry. Conclusions The first 30–40 data points should be adopted to delineate I-MR control chart of the linear accelerator in daily quality control process. The quality control process should be completed by a fixed and small group of personnel and an optimal tolerance level should be customized.