中文摘要：

目的应用Vrian Trilogy锥形束CT（CBCT）分析盆腔部调强放射治疗中的摆位误差，为设计放疗临床靶区（CTV）外放到计划靶区（胛V）提供数据参考。方法30例盆腔肿瘤患者均采用调强放疗技术，真空袋固定，首次治疗均需行CBCT扫描，以后每周扫描1次，将CBCT图像和计划CT图像进行自动及手动匹配，获得X（左右）、Y（头脚）、Z（前后）方向的偏移数据，以判断摆位的准确性。结果患者首次摆位后行CBCT扫描，其在X、Y、Z方向上的误差分别为（1．73±0．62）mm、（5．63±0．13）mm、（2．81±0．52）mm；经纠正后的误差明显降低，且与首次摆位后的误差相比，有统计学意义（P〈0．05）；但在治疗过程中的再次摆位误差较纠正后显著增加（P〈0．05）；根据MPTV的计算公式（M=2．5∑总＋0．7总σ），纠正前X、Y、Z方向的MPTV分别为4．58mm、11．82mm、6．45mm，纠正后X、Y、Z方向的MPTV分别为1．78mm、2．84mm、2．14mm。结论使用CBCT扫描系统，能较准确、高效地修正摆位误差，提高治疗精确度，并为治疗单位准确设定计划靶体积（PTV）提供了依据。

英文摘要：

Objective Application of Vrian Trilogy linear accelerator cone beam CT positioning error analysis pelvic IMRT, provides reference data for the design of radiotherapy plan CTV into PTV. Methods A total of 30 cases of pelvic tumor were treated with IMRT, vacuum bag, the,first treatment were performed CBCT scanning, a week after the scan 1 times, the CBCT image and CT image automatic and manual matching, X （left-right）, Y （cranio-caudal）, Z （ven- tro-dorsal） data offset direction in order to judge, accuracy of positioning. Results Patients with a first positioning were scanned by CBCT, the X, Y, Z direction of the errors were （1.73±0.62）mm、（5.63±0.13）mm、（2.81±0.52）mm; the error corrected significantly decreased, compared with the first swing error bits, with statistical significance（P 〈 0.05）; but in the course of treatment of the position error is corrected again increased significantly （P 〈 0.05）; according to the calculation formula of MPTV （M=2.5 ∑ total＋0.7σ）, X, Y, Z before correction direction of MPTV were 4.58 mm, 11.82 mm, 6.45 mm, X, Y, corrected Z direction MPTV respectively 1.78 mm, 2.84 mm, 2.14 mm. Conclusion The use of CBCT scanning system, can accurately, efficiently correct positioning errors, improve the treatment accuracy, and for the treatment of unit set exactly planned target volume （PTV） provides a basis.