电子射野影像系统在盆腔肿瘤放疗中的应用

Application of Electronic Portal Imaging Device for Pelvic Cancers

目的:应用电子射野影像系统分析我院行盆腔适形调强放疗病人的摆位误差情况,为临床上计划靶区(PTV)的设定提供参考依据。方法:选取行盆腔适形调强肿瘤病人21例,应用电子射野影像系统对每例患者每周分别拍摄正侧射野图像各1张,共获取210张图像,分别将图像与计划系统所形成的相应数字重建影像(DRR)进行比较,获取上下(X轴)、左右(Y轴)、前后(Z轴)方向的摆位误差。结果:21例患者X轴、Y轴、Z轴各方向的系统误差的标准差分别1.02,2.37,1.94mm,随机误差的标准差分别是1.35,2.24,2.30mm。X轴、Y轴、Z轴的摆位扩边值分别为3.49,7.51,6.46mm。结论:尽管应用真空垫、热塑网膜等体位固定方法,但由于各种原因,盆腔肿瘤放疗仍有一定的摆位误差,在设定盆腔靶区时建议左右、上下、前后分别外扩3.5,8,7mm。

Objective：To study the role of electronic portal imaging device（EPID）on verification of setup errors of conformal intensity modulated radiotherapy for pelvic cancers,and to provide reference data for planning target volume（PTV）.Methods：For twenty one cases of pelvic cancers who received conformal intensity modulated radiotherapy,AP-PA and lateral EPID were performed every week during treatment.A total of 210digital photos were acquired and were compared with the results of digital reconstruction radiology（DRR）by planning system to calculate the setup error of X,Y,and Z axis.Results：The system error of setup error of X,Y,and Z axis in 21cases were 1.02mm,2.37mm,1.94mm,respectively,and the random error were 1.35mm,2.24mm,2.30mm,respectively.The margin of PTV（Mptv）was 3.49mm,7.51 mm and 6.46mm,respectively.Conclusion：Although patient fixation methods including vaccum cushion and thermal plastic mold were used,the setup error still existed for radiotherapy of pelvic cancers.We suggests the margin of planning PTV should be 3.5mm,8mm,and 7mm in direction of X,Y,and Z axix.