扇形束在线高能X线计算机体层摄影术引导下食管癌的摆位误差分析

目的利用扇形束在线高能X线计算机体层摄影术（MVCT）获取的数据分析食管癌的摆位误差及其影响因素，为临床医生在临床靶区-计划靶区外放间距提供参考。方法收集行螺旋断层放射治疗（tomotherapy，TOMO）治疗的食管癌病人，将治疗前行MVCT扫描获取的图像与模拟CT的图像进行配准，记录X（左右）、Y（头脚）、Z（腹背）和ROLL（沿横截面旋转）四个方向的误差并对其分析。结果≥ 70岁病人在X、Z和ROLL三个方位的摆位误差均大于 < 70岁病人（P < 0.01），在Y方向上两年龄组摆位误差差异无统计学意义（P>0.05）。不同方向的摆位误差显示，X轴和Y轴方向的摆位误差主要集中在0~3 mm，Z轴方向的主要集中在3.1~6 mm；横断面旋转误差分布在区间0°~、1.1°~和2.1°~的分别为537（88.2%）、62（10.2%）和10（1.6%）。体膜固定与颈胸膜固定病人的摆位误差在X轴方向和Z轴方向差异无统计学意义（P>0.05），在Y轴方向和ROLL轴方向上采用体膜固定方式病人的摆位误差大于颈胸膜（P < 0.01）。在Y轴方向上女性摆位误差大于男性（P < 0.05），X、Z和ROLL方向不同性别间摆位误差差异均无统计学意义（P>0.05）。结果不同固定方式治疗食管各有优点与缺点，临床医生在勾画靶区外放距离时应考虑病人多方面的因素，比如年龄、性别等。

Analysis of the positioning error of esophageal carcinoma guided by fan-beam online high energy X-ray computed tomography

ObjectiveTo investigate the positioning error of esophageal carcinoma using the fan-beam online high energy X-ray computed tomography(MVCT), and analyze its influencing factors to provide a reference for clinical workers in CTV-PTV external spacing.MethodsThe clinical data of the esophageal cancer patients treated with tomotherapy(TOMO) were investigated.The images obtained from the MVCT scan before treatment were registered with those from the simulated CT, and the errors in X(left and right), Y(head and foot), Z(abdomen and back) and ROLL(rotation along the cross section) were recorded and analyzed.ResultsThe positioning errors of X, Z and ROLL directions in patients ≥ 70 years old were greater than those in patients < 70 years old(P < 0.01), and the difference of the positioning error of Y direction between two groups was not statistically significant(P>0.05).The results of positioning error in different directions showed that the positioning errors in the X-axis and Y-axis were mainly concentrated in 0-3 mm, while which in the Z-axis was mainly concentrated in 3.1-6 mm.The cross-sectional rotation error distributing in the interval 0°-, 1.1°-and 2.1°-were 537(88.2%), 62(10.2%) and 10(1.6%), respectively.The differences of the positioning errors in the X-axis and Z-axis were not statistically significant between body membrane fixation and cervical pleural fixation patients(P>0.05), and the positioning errors in the Y-axis and ROLL-axis in patients with body membrane fixation were greater than those in patients with cervical pleural fixation(P < 0.01).In the Y-axis direction, the positioning error of women was greater than that of men(P < 0.05), and there was no statistical significannce in the positioning errors of X, Z and ROLL directions between male and female(P>0.05).ConclusionsDifferent fixation methods have advantages and disadvantages in treating esophagus.In delineating the distance outside the target area, clinicians should consider various factors of patients, such as age and gender.