基于验证模体的第六代射波刀系统多叶光栅模式临床质量控制检测研究

Verification Phantom-based clinical quality control and detection of the MLC of CyberKnife M6

目的设计并实现一种第6代射波刀(CK-M6)多叶光栅(MLC)模式的日常输出稳定性晨检方法。方法将20 cm×20 cm×10 cm验证体模(Phantom),经CT扫描后图像传入Precision计划系统,采用Fiducial追踪方式实现加速器输出前端与Phantom表面相对固定位置的高精度对准,设计10 cm×10 cm的MLC照射野且输出200 MU的晨检计划DailyCheck,进行重复性、灵敏度与准确度测量,并采用人工Fixed方式及研究所设计的DailyCheck方式对CK-M6进行1个月连续检测。结果DailyCheck 10次重复性测量均值为492.28 pC,标准差为0.09,具有较好的稳定性;测量值对系统输出剂量呈线性响应,二者相关系数R^(2)>0.999;当Phantom相对加速器输出前端中心位置的左右/前后方向上具有2 mm位置偏差时,位置所引起的测量误差等效于1.24 MU的输出剂量偏差;采用人工Fixed方式及DailyCheck方式连续测量结果均在允许限值内,且二者具有较好的一致性。结论通过验证体模Fiducial追踪所建立的DailyCheck晨检方式能简便、快捷、精准的实现CK-M6系统MLC模式下输出剂量稳定性的日常检测,可广泛用于临床CKM6系统的质量控制。

Objective To provide a new morning check method for the output dose stability of the multileaf collimator(MLC)of the CyberKnife M6(CK-M6)system.Methods The CT images of a verification phantom with a size of 20 cm×20 cm×10 cm were transmitted into the Precision Treatment Planning System(ver.1.1.1.1).The high-precision alignment between the accelerator output front and the fixed position of the phantom surface was achieved using the fiducial tracking method.A 10 cm×10 cm radiation field was formed by the MLC and a DailyCheck plan with an output of 200 MU was designed.The repeatability,sensitivity,and accuracy of the DailyCheck plan were measured,and the CK-M6 system was continuously tested for one month using the artificial fixed method and the DailyCheck plan designed in this study.Results The average and the standard deviation of 10 repeated measurements by the DailyCheck plan were 492.28 pC and 0.09,respectively,indicating good stability.There was a linear correlation between the measured values and the output dose,with a correlation coefficient of R^(2)>0.999.Moreover,there was a position deviation of 2 mm between the phantom and the accelerator output front,and the result ant effect on the measured values was equivalent to a dose deviation caused by an output of 1.24 MU.The result from the continuous measurement of both the artificial fixed method and the DailyCheck plan fell within permissible limits,showing high consistency.Conclusions The DailyCheck plan established through the fiducial tracking of a verification phantom can achieve the convenient,quick,and accurate daily detection of the output dose stability of the MLC of CK-M6.Therefore,this method can be widely applied in the clinical quality control of the CK-M6 system.