图像引导放疗技术在直肠癌患者术前调强放疗中的应用

Application of image-guided radiation therapy technology in patients with rectal cancer treated with intensity modulated radiation therapy technology before operation

目的:探讨图像引导放疗技术(IGRT)在直肠癌患者术前新辅助调强放疗(IMRT)中的应用,分析其对靶区勾画的指导意义。方法:67例临床分期为Ⅱ~Ⅲ期(T3-4N0M0或T1-4N1-2M0)的直肠癌患者行术前IMRT,放疗期间每周行1次IGRT,获得术前和术后的2组影像在三维空间的对比位置误差,计算系统误差(Σ)和随机误差(σ),按照Van Herk公式计算计划靶区扩边值(MPTV)。结果:389个CBCT扫描图像在x、y、z 3个轴位方向上的误差范围分别为(0.86^-1.13)、(1.94^-2.11)及(1.87^-1.81)cm。校正后y轴和z轴上的平移误差小于校正前(t=3.541,P=0.001;t=3.275,P=0.000);校正后x轴和y轴上的旋转误差小于校正前(t=1.260,P=0.000;t=2.797,P=0.000。校正前,x、y、z 3个轴位方向上的MPTV分别为2.00、3.25和2.88cm,校正后为0.73、1.74和1.50cm,分别减少了1.27、1.51及1.38cm。结论:IGRT可减少直肠癌患者术前IMRT的系统误差和摆位误差,是精确放疗的有效质量保证。

Objective：To explore the application of image-guided radiotherapy technology（IGRT）in intensity modulated radiation therapy（IMRT）in the patients with rectal cancer before operation,and to analyze its guiding significance for target region.Methods：A total of 67 patients with rectal cancer（Ⅱ-Ⅲ stages,CT3-4N0M0 or CT1-4N1-2M0）were treated with IMRT before operation.IGRT was used for once a week during the radiotherapy and two sets of image contrast errors in the three-dimensional space were obtained.The systematic（Σ）and random（σ）setup errors were calculated.The MPTV was calculated according to the van Herk formula.Results：A total of389 CBCT scans were analyzed.The error range in the directions of e x,y,z axis were（0.86--1.13）,（1.94--2.11）,and（1.87--1.81）cm,respectively.The translation errors of the corrected y axis and z axis were less than those before correction（t=3.541,P=0.001;t=3.275,P=0.000）;the rotation errors of the corrected x axis and y axis were less than those before correction（t=1.260,P=0.000;t=2.797,P=0.000）.Before correction,the MPTV in the directions of x,y,z axis were 2.00,3.25,and 2.88 cm,respectively,which were0.73,1.74,and 1.50 cm after correction,reduced by 1.27,1.51,and 1.38 cm,respectively.Conclusion：IGRT could effectivly guarantee the accuracy of IMRT of the patients with rectal cancer by reducing the systematic errors and position errors.