图像引导放射治疗在653例宫颈癌摆位误差的分析

Analysis of the setup error in 653 cervix cancer patients treated with image-guided radiotherapy

目的:应用锥形束CT(CBCT)评价宫颈癌患者图像引导放射治疗(IGRT)的摆位误差及体重因素对摆位误差的影响。方法:回顾性分析应用Trilogy直线加速器治疗的653例宫颈癌患者资料,使用其机载影像系统(OBI)行CBCT,共采集1175幅容积图像与计划CT图像进行配准,记录升降(X轴)、进出(Y轴)和左右(Z轴)3个轴向的误差。以正常体重指数(BMI=23)为分界,将患者分为正常组(BMI<23)和肥胖组(BMI≥23),对比分析两组BMI的差异。结果:X轴、Y轴及Z轴3个平移轴向的摆位误差分别为(-0.38±3.6)mm、(0.01±4.5)mm和(-0.13±2.8)mm,结果满足临床要求;提示体重因素对摆位误差有影响,其中肥胖组患者在X轴向的摆位误差大于正常组,差异有统计学意义(t=-2.446,P<0.05)。两组在Y轴及Z轴向的摆位误差无显著差异。结论:宫颈癌患者的整体摆位误差结果较好,能够满足临床要求;同时患者BMI对于X轴向的摆位误差具有一定影响,故应更加关注BMI较大患者的摆位情况。

Objective： The aim of this study was to evaluate setup errors by Cone-beam computed tomography（CBCT） method in cervical cancer patients with image-guided radiotherapy and discussthe impact of body mass index（BMI）. Methods： A retrospective study was adopted to analyze 653 cervix cancer patients were treated with Trilogy linear accelerator from 2008 to 2015 in our department. CBCT was performed on a Varian Trilogy linear accelerator via on–board images system, and 1175 images were acquired and matched up with planning CT images, and then systematic（∑） and random（σ） errors in X（vertical）Y（longitudinal）and Z（lateral） directions were analyzed. The patients were divided into normal BMI group（BMI23）and overweight patients group（BMI≥23）. The software SPSS 19.0 was used for data analyzing,and the differences between two groups were compared by paired samples T test and there was statistically significant if P0.05. Results： The errors in X、Y and Z direction were-0.38±3.6mm、0.01±4.5mm and-0.13±2.8mm, respectively, and they can meet the clinical demand;body weight factor had an impact on setup errors, and there was significant difference in vertical direction（t=-2.446, P0.05） between the two groups, however,there were no significantly difference in the other two directions. Conclusions： The overall setup errors results met the clinical demand; body weight factor can lead to larger setup errors in vertical direction, therefore more attention should be paid to the patients with larger BMI.