中文摘要：

目的利用锥形束CT（CBCT）技术比较头颈胸膜和胸膜两种热塑体膜固定方式在胸部肿瘤放疗时的摆位误差。方法分别对30例头颈胸膜固定的165次、胸膜固定的163次CBCT数据进行回顾性分析,比较两种固定方式在左右、前后和头足3个方向上的摆位误差及其分布情况。结果在左右、前后和头足3个方向上的摆位误差均在3 mm以内,符合临床治疗要求。两种固定方式在左右和头足方向上的摆位误差差异有统计学意义（P〈0.05）,而在前后方向上的摆位误差差异无统计学意义（P〉0.05）;但头颈胸膜固定方式在头足方向上具有较好的稳定性,而胸膜固定方式在左右方向上具有较好的稳定性（P〈0.05）。结论两种固定方式各有优劣,在不同方向上的摆位误差不同,临床治疗时应注意选择合适的固定方式。

英文摘要：

Objective To compare difference of positioning errors between head-neck-pleural and pleural thermoplastic body models in thoracic tumor radiotherapy using cone beam CT（ CBCT）. Methods Clinical data of 30 patients with 165 CBCT times using head-neck-pleural fixation and 30 patients with 163 CBCT times using pleural fixation was retrospectively analyzed,and positioning errors and distribution conditions were compared in left-right,anterior-posterior and cranial-caudal directions between two fixation methods. Results The positioning errors were less than 3 mm in left-right,anterior-posterior and cranial-caudal directions,and the values met clinical requirements. There were significant differences of positioning errors in left-right and cranial-caudal directions（ P〈 0. 05）,but there was no significant difference in anterior-posterior direction between two fixation methods（ P 〉0. 05）; head-neck-pleural fixation had better stability in cranial-caudal direction,and pleural fixation had better stability in left-right direction（ P〈 0. 05）. Conclusion Two fixation methods have their own advantages and disadvantages,and positioning errors are different in different directions. It is very important to choose appropriate fixation in clinical radiotherapy.