Versa HD医用直线加速器治疗床自动移位的系统误差

Systematic Error of Automatic Bed Moving of Versa HD Medical Linear Accelerator

目的验证图像引导放射治疗中Versa HD医用直线加速器治疗床自动移位的准确性及剂量的可靠性,为实现精准放射治疗提供参考依据。方法选取2019年6月至2020年7月于福建医科大学孟超肝胆医院放疗科行图像引导放射治疗的30例肝癌患者作为研究对象,治疗前均进行锥形束CT(CBCT)扫描,采用灰度配准的匹配方式获得左右、头脚、腹背方向的摆位误差(X_(1),Y_(1),Z_(1)),利用治疗床自动移位功能校正摆位误差后,再进行一次CBCT扫描,并采用相同的匹配方式得到系统误差(X_(2),Y_(2),Z_(2));将系统误差反向输入Matrixx系统,进行剂量验证。结果系统误差的最大值均<1 mm;考虑系统误差的γ通过率(3%/3 mm和2%/2 mm标准下)均>95%,可满足临床剂量验证通过率>90%的要求,与不考虑系统误差的γ通过率比较,差异无统计学意义(P>0.05)。结论Versa HD医用直线加速器远程控制的自动移位精度可以达到亚毫米量级,可忽略该系统误差对放射治疗计划剂量学验证的影响,有效提高工作效率。

Objective The accuracy and dose reliability of the automatic bed moving of Versa HD medical linear accelerator in image-guided radiotherapy were verified,aiming to provide references for achieving precise radiotherapy.Methods 30 cases of liver cancer patients treated with image-guided radiotherapy in Mengchao Hepatobiliary Hospital of Fujian Medical University were selected.Cone beam CT(CBCT) scanning was performed before treatment,and the setup errors of left and right,head and foot,abdomen and back directions (X_(1),Y_(1),Z_(1)) were obtained by gray-scale registration.After the positioning errors were corrected by automatic bed moving function,CBCT scanning was performed again.The system errors (X_(2),Y_(2),Z_(2)) were obtained by the same registration method;The system error was input into Matrixx system in reverse,and the dose verification were conducted again.Results The maximum values of systematic errors were all less than 1 mm,and theγpass rates(with the criteria of 3%/3 mm and 2%/2 mm)with system errors considered were all greater than 95%,which could meet the requirement that the pass rate of clinical dose verification should be higher than 90%,and when theγpass rate with and without system errors considered were compared,the difference was not statistically significant(P>0.05).Conclusion The accuracy of remote control automatic bed moving of Versa HD medical linear accelerator could reach submillimeter level,and the influence of this system error on dose verification can be ignored,thus the work efficiency could be improved.