热塑头肩模与头颈肩真空垫在肺癌脑转移大分割立体定向放疗中固定效果分析

The setup errors of thermoplastic head and shoulder molds with or without vacuum pad in HFSRT for brain metastases in the lung cancer

目的回顾性分析热塑头肩模单用或联合使用头颈肩真空垫在脑转移瘤大分割立体定向放疗(HFSRT)中的固定效果。方法纳入2017—2019年间54例非小细胞肺癌脑转移并行HFSRT患者,热塑头肩模固定24例(单模组),热塑头肩模+真空垫固定30例(联合组)。治疗前后分别行在线图像配准,记录疗前分次间误差及疗后分次内误差,治疗过程中应用光学表面监测分次内误差,成组t检验分析两组各方向误差差异。结果全组患者分次间7.0%~15.4%的水平误差≥3mm,7.0%~12.6%旋转误差≥2°;单模组比联合组前后方向水平误差小[(1.035±1.180)mm∶(1.512±0.955)mm,P=0.009],矢状位旋转误差也小(0.665°±0.582°∶0.921°±0.682°,P=0.021)。全组患者分次内误差为0%~0.7%的水平误差>1mm,无旋转误差≥1°;联合组比单模组左右和前后方向水平误差小[(0.047±0.212)mm∶(0.246±0.474)mm,P=0.004和(0.023±0.152)mm∶(0.140±0.350)mm,P=0.020],矢状位旋转误差也小(0.091°±0.090°∶0.181°±0.210°,P=0.001)。光学表面监测数据印证了上述结果。结论热塑头肩模±头颈肩真空垫固定可达到脑转移瘤HFSRT的精度要求,但需配合在线图像配准及六维床体位校正,联合组的分次内固定效果更好。光学表面监测分次内运动有一定价值。

Objective To retrospectively analyze the setup errors of thermoplastic head and shoulder molds alone or combined with vacuum pad in hypofractionated stereotactic radiotherapy(HFSRT)for non-small cell lung cancer(NSCLC)with brain metastases.Methods Fifty-four NSCLC patients with brain metastases who received HFSRT from 2017 to 2019 were enrolled in this study.Twenty-four patients were fixed with thermoplastic head and shoulder molds(group A),and 30 patients were fixed with thermoplastic head and shoulder molds plus vacuum pad(group B).The interfraction and intrafraction setup errors were acquired from cone-beam CT online image registration before and after the HFSRT.Optical surface system was applied in monitoring the intrafraction setup errors.The setup errors in each direction between two groups were analyzed by independent samples t-test.Results For the interfraction setup errors of the whole group,the proportion of the horizontal setup errors of≥3mm was 7.0%to 15.4%and 7.0%to 12.6%for the rotation setup errors of≥2°.In group A,the anteroposterior setup error was(1.035±1.180)mm,significantly less than(1.512±0.955)mm in group B(P=0.009).In group A,the sagittal rotation setup error was 0.665°±0.582°,significantly less than 0.921°±0.682°in group B(P=0.021).For the intrafraction setup errors of the whole group,the proportion of horizontal setup errors of≥1mm was 0%to 0.7%,whereas no rotation setup error of≥1°were observed.In group B,bilateral,anteroposterior and sagittal rotation setup errors were(0.047±0.212)mm,(0.023±0.152)mm and 0.091°±0.090°,significantly less compared with(0.246±0.474)mm,(0.140±0.350)mm and 0.181°±0.210°in group A(P=0.004,P=0.020,P=0.001),respectively.Optical surface monitoring data were consistent with the obtained results.Conclusions Thermoplastic head and shoulder molds(with or without vacuum pad)combined with online image registration and six-dimensional robotic couch correction can be applied in HFSRT for brain metastases from NSCLC.The intrafraction setup errors in group B are smaller than those in group A.Optical surface system has certain value in monitoring the intrafractional movement.