电子射野影像装置对盆腔肿瘤放疗摆位误差的测定  

Evaluation of set-up errors in pelvic irradiation with electronic portal imaging device

作　　者：邬筱莹[1] 章真[1] 王文超[1] 任珺[1] 郭晓梅[1] 陆惠忠[1] 

机构地区：[1]复旦大学附属肿瘤医院放疗科,上海200032

出　　处：《中华放射肿瘤学杂志》2007年第1期52-54,共3页Chinese Journal of Radiation Oncology

摘　　要：目的利用Elekta iView GT量化测定盆腔肿瘤放疗摆位中的系统误差及随机误差，为放疗计划Prv的设定提供初步的参考依据。方法对12例接受盆腔放疗的病例进行摆位误差量化测定，共获取244组图像数据。所有入组病例均为CT模拟定位及适形放疗。将每日前后野和两侧野的电子射野影像装置（EPID），采用盆腔骨性标志与数字重建图像（DRR）比较，记录在左右、头脚、前后方向上的移动，从得到的数据计算系统和随机误差。结果每日摆位误差的最大值在左右、头脚、前后方向上分别为9．9、14．0、21．1mm，摆位的系统误差分别为0．5、0．2、2．3mm。12例病例数据显示，在左右、头脚、前后方向上移动幅度5—10mm和＞10mm的发生频率分别为8％、9％、21％和0％、1％、3％。结论应用EPID测定盆腔肿瘤放疗的摆位误差，为放疗计划Prv的设定提供初步的参考依据。在Prv设定时，考虑由摆位误差而引起的边界（SM）至少需5mm，但前后方向以扩大到10mm为好，以达到97％的靶区包绕率，且需注意个体差异。Objective Evaluate the systematic and random set-up error in the pelvic irradiation using electronic portal imaging device（EPID） to provide institution-specific margin for PTV design in pelvic cancer treatment planning with 3D eonformal therapy and/or IMRT. Methods From May to August 2005, twelve patients who received pelvic irradiation, were involved in this study. CT simulations were performed and DRRs were generated as the reference images. Ant-post and lateral portal images were taken daily, and total of 244 sets of EPID images were collected for the whole group. The translational shifts along right-left, superior-inferior and anterior-posterior directions were calculated with aligning the pelvic bony structures on the DRRs and electronic portal images. The systematic and random setup errors were evaluated based on the 244 sets of data. PTV margin was assessed assuming target rotation was negligible. Results In the right-left （R-L）, superior-inferior （S-I） and anterior-posterior （A-P） directions, the maximum shifts were 9.9, 14. 0 and 21.1 mm and the systematic setup errors were 0.5,0.2 and 2.3 mm respectively. For all 244 sets of data in this study, the frequency of the shift larger than 10 nun were 0% （R-L） , 1% （ S-I ） and 3% （ A-P） ; and in R-L and S-I direction, 92% and 91% of the times the shift was smaller than 5 ram. However, only 79% of the times the A-P shift was less than 5 ram. Condusions It is suggested in this study that in order to achieve a target coverage of better than 95% of the times throughout the pelvic irradiation in our institution, a 5 mm PTV margin in right-left and superior-inferior directions is required, however, the anterior -posterior margin needs to be increased to at least 10 ram. One needs to be cautious though when applying the PTV margin derived from small sample of patient population to individual patient.

关 键 词：盆腔肿瘤/放射疗法 摆位误差 电子射野影像装置 

分 类 号：R686[医药卫生—骨科学]