基于光学表面监测系统进行头部肿瘤放疗实时定位准确性的初步研究

Preliminary study on accuracy of real-time positioning with optical surface monitoring system during radiotherapy for head tumor

目的:评估瓦里安直线加速器EDGE上搭载的光学表面监测系统(OSMS)对偏差探测的准确性(或纠错能力)。方法:使用一个颅脑体模,评估OSMS治疗前摆位准确性、治疗中监测偏移精确度、特定条件下(非零床角和仅双摄像头工作)能否正常使用。结果:OSMS实现治疗前摆位,其等中心与锥形束CT(CBCT)摆位的偏差范围为(0.6±0.5)mm,角度最大偏差为0.3°;治疗中监测偏移精确度,探测平移偏差范围(0.1±0.2)mm,探测角度偏差范围0.10°±0.07°;不同的床角下OSMS的精确度接近,挡住其中一个摄像头产生约0.5 mm的不确定度。结论:OSMS配合CBCT能够为头部肿瘤放疗的治疗前摆位及治疗中实时监测提供保证。

Objective To evaluate the deviation detection accuracy of optical surface monitoring system(OSMS) in Varian linear accelerator EDGE. Methods A head phantom was used to evaluate the positioning accuracy before treatment, monitor the position shift during treatment and assess the performance of OSMS under certain conditions(non-zero couch angle or only two cameras at work). Results OSMS achieved the positioning before treatment, and the deviation range between the positioning with CBCT and that with OSMS was(0.6±0.5) mm, with a maximum angle deviation of 0.3°. Moreover, the deviation range of position shift during treatment between OSMS and CBCT was(0.1±0.2) mm, and the deviation range of detection angle was 0.10°±0.07°. Even at different couch angles, the accuracy of OSMS was similar. However, an uncertainty of 0.5 mm was generated when one of cameras was blocked. Conclusion OSMS combined with CBCT in radiotherapy for head tumors can provide guarantee for positioning before treatment and real-time monitoring during treatment.