两种体位固定方法在宫颈癌调强放射治疗中摆位固定精度的差异研究

Difference of positioning and fixation accuracy between two posture fixation methods in intensity-modulated radiotherapy for cervical cancer

目的分析使用真空袋和Orfit架2种固定方法在宫颈癌调强放疗摆位精度上的差异,为临床决策提供参考。方法选取2019-09-14-2020-11-02在本院进行调强放疗的56例宫颈癌患者为研究对象,其中28例患者使用仰卧位真空袋固定(真空袋组),另外28例患者使用俯卧位Orfit架固定(Orfit架组)。所有患者每次放疗前进行机载锥形束CT扫描,获得头脚、左右、前后平移方向误差和冠状位、矢状位、横断位旋转方向误差并进行非参数检验,根据计划靶区外扩边界(MPTV)=2.5Σ+0.7σ分别计算对应的MPTV。结果真空袋组头脚方向的摆位误差为(-0.32±3.25)mm,小于Orfit架组的(-1.76±4.37)mm,z=-9.819,P<0.001;左右方向的摆位误差为(0.98±3.10)mm,大于Orfit架组的(-0.49±3.10)mm,z=-6.602,P<0.001;前后方向的摆位误差为(0.94±2.64)mm,小于Orfit架组的(-1.08±2.63)mm,z=-13.675,P<0.001;冠状位旋转误差为(-0.07±0.84)°,小于Orfit架组的(0.09±1.18)°,z=-2.181,P=0.029;矢状位旋转误差为(1.26±1.28)°,大于Orfit架组的(-0.31±1.60)°,z=-17.666,P<0.001;横断位旋转误差为(-0.27±0.80)°,大于Orfit架组的(-0.01±0.90)°,z=-4.969,P<0.001。真空袋组的外扩边界为头脚6.24 mm,左右6.20 mm,前后5.83 mm;Orfit架组的外扩边界为头脚8.08 mm,左右6.36 mm,前后5.94 mm。结论使用真空袋仰卧位进行固定可减少患者头脚方向和前后方向的误差,而使用Orfit架俯卧位则能减少左右方向的误差,两者各有优势,在使用Orfit架俯卧位时,则应注意在头脚方向上的计划外扩边界稍大于其他方向。

Objective To analyze the difference in the setting accuracy of intensity-modulated radiotherapy for cervical cancer using the vacuum bag and the Orfit frame,and provide a reference for clinical decision-making.Methods Totally 56 cervical cancer patients with undergoing intensity-modulated radiotherapy in our hospital were selected as the research objects from September 14,2019 to November 2,2020.28 of them were fixed with a supine vacuum bag(vacuum bag group),and the other 28 were used Orfit frame fixed in prone position(Orfit frame group).All patients underwent airborne cone-beam CT scan before each radiotherapy to obtain head-foot,left-right,front-to-back translational errors,and coronal,sagittal,and transverse rotation directions.Non-parametric tests were performed,and formulas were used to plan outside the target area.According to the margin of planning target volume(MPTV)=2.5Σ+0.7σcalculated the corresponding MPTV respectively.Results The set-up error of the head and foot direction of the vacuum bag group was(-0.32±3.25)mm,which was smaller than the(-1.76±4.37)mm of the Orfit rack group,z=-9.819,P<0.001.The set-up error of the left and right directions was(0.98±3.10)mm,greater than(-0.49±3.10)mm of the Orfit frame group,z=-6.602,P<0.001.The set-up error in the front and back direction was(0.94±2.64)mm,which was smaller than that of the Orfit frame group(-1.08±2.63)mm,z=-13.675,P<0.001.The coronal rotation error was(-0.07±0.84)°,which was smaller than(0.09±1.18)°of Orfit frame group,z=-2.181,P=0.029.The sagittal rotation error was(1.26±1.28)°,greater than(-0.31±1.60)°of Orfit frame group,z=-17.666,P<0.001.The transverse rotation error was(-0.27±0.80)°,greater than Orfit frame group(-0.01±0.90)°,z=-4.969,P<0.001.The outer expansion boundary of the vacuum bag group was 6.24 mm head and foot,6.20 mm left and right,and 5.83 mm front and back.The outer expansion boundary of the Orfit rack group was 8.08 mm head and foot,6.36 mm left and right,and 5.94 mm front and rear.Conclusions The immobilization of vacuum bag in the supine position is better than that of Orfit frame in head-foot and front-back direction.The immobilization of Orfit frame in the prone position is better than that of vacuum bag in left-right direction,Both immobilization have their advantages.The margin in head-foot direction is slightly larger than in other directions when used the Orfit frame for immobilization.