盆腔肿瘤放疗中的摆位误差及其与皮下脂肪厚度的关系分析

Analysis of setup error in pelvic tumor radiotherapy and its relation with subcutaneous fat thickness

目的:应用直线加速器机载锥形束CT(cone beam CT,CBCT)分析盆腔肿瘤放疗中的摆位误差,同时探究皮下脂肪厚度与摆位误差是否存在相关性。方法:选取2016年5月至2017年6月收治的59名盆腔肿瘤患者,以热塑体膜进行体位固定,应用CT扫描定位。治疗前均行CBCT扫描获取图像并与定位CT图像进行自动+手动微调方式进行配准,记录X(左-右)、Y(头-脚)、Z(前-后)轴3个方向上的位移数据,并记录盆腔皮下脂肪厚度。采用SPSS18.0软件进行数据统计。结果:59例患者X、Y、Z轴3个方向上的平均摆位误差为(1.07±2.18)、(-0.07±5.00)、(1.15±2.38)mm。患者皮下脂肪厚度范围为0.3~2.9 cm,平均为1.6 cm。X、Y、Z轴3个方向上的摆位误差绝对值与皮下脂肪厚度进行Spearman相关性分析的结果分别为0.15、0.11和0.20(P>0.05),差异无显著性。结论:各个轴向上的摆位误差值都在±5 mm范围内,确定了摆位方法的科学合理;摆位误差与皮下脂肪厚度只存在弱相关性。

Objective To analyze the setup error during tumor radiotherapy by linear accelerator cone beam CT（CBCT）,and to determine the presence of correlation between subcutaneous fat thickness and setup error. Methods From May 2016 to June 2017 59 patients with pelvic tumors underwent CT scan after body positioning with thermoplastic model,CBCT images were obtained before treatment and registered automatically and manually along with localizable CT images. The displacement data at X（left-right）, Y（head-foot） and Z（front-back） directions as well as pelvic subcutaneous fat thickness were recorded,and SPSS 18.0 was used for data statistics.Results The 59 patients had the mean setup errors at X,Y and Z directions being（1.07±2.18）,（-0.07±5.00）and（1.15±2.38）mm respectively,and the subcutaneous fat thickness ranging from 0.3 to 2.9 cm with a mean value of 1.6 cm.Spearman analysis showed the correlations between the absolute value of the errors and the subcutaneous fat thickness being 0.15, 0.11 and 0.20 respectively at X, Y and Z directions, and there were no significant differences between the correlations（P〉0.05）.Conclusion The setup method verifies its feasibility by restraining its errors at X, Y and Z directions between -5 and ＋5 mm, and there is a weak correlation between the setup error and subcutaneous fat thickness.