环形施源器重建偏差对宫颈癌患者剂量影响分析

Impacts of ring applicator reconstruction uncertainties on radiation dose in patients with cervical cancer

目的 研究在CT引导的三维后装中环形施源器（Nucletron#090617）重建偏差对宫颈癌患者后装受照剂量的影响.方法 选取已完成治疗的根治性宫颈癌患者20例,在计划系统中模拟宫腔施源器,环形施源器和两者同时发生重建偏差时的剂量分布,重建偏差的方向分为施源器顶端方向（＋）和施源器连接方向（-）,重建偏差模拟±1、±2、±3 mm.统计CTV的D100、D90、D50,膀胱、直肠、小肠的D0.1cc、D1cc、D2cc,分析施源器重建偏差对三维后装剂量的影响.结果 宫腔施源器重建偏差对剂量的影响高于环形施源器.对于CTV评价参数,由施源器重建偏差导致的剂量偏差随统计体积的增大而增大.对于OAR评价参数,由施源器重建偏差导致的剂量偏差随统计体积的增大而减小.小肠剂量受施源器重建偏差影响最大.对CTV D90、膀胱D2cc、直肠D2cc、小肠D2cc,当环形施源器,宫腔施源器,二者同时发生3 mm重建偏差时产生的影响偏差分别为090%、162%、174%,133%、153%、178%,089%、185%、197%,086%、304%、350%.结论 三维后装中施源器重建偏差会对剂量产生一定的影响,为提高后装放疗的精确性,需要对施源器重建过程进行全面质量控制.

Objective To investigate the impacts of ring applicator （ Nucletron#090617 ） reconstruction uncertainties on the radiation dose of computed tomography-guided three-dimensional （ 3D） brachytherapy for cervical cancer. Methods Twenty patients with cervical cancer who completed radical treatment were enrolled as subjects. In a treatment planning system, dose distribution was simulated with reconstruction uncertainties of tandem applicator, ring applicator, and both tandem and ring applicators, respectively. Two directions of reconstruction uncertainties were towards the tip （＋） and the connector end （-） of the applicator. Reconstruction uncertainties of ± 1 mm, ± 2 mm, and ± 3 mm were simulated. The D100 , D90 , and D50 for clinical target volume （ CTV） and D0.1cc , D1cc , and D2cc for the bladder, rectum, and small intestine were evaluated. The effects of applicator reconstruction uncertainties on radiation dose of 3D brachytherapy were analyzed. Results The tandem applicator had greater impacts on radiation dose than the ring applicator. The dose deviation due to applicator reconstruction uncertainties increased with the increase in volume for CTV parameters but decreased with the increase in volume for parameters of organs at risk. The impacts of applicator reconstruction uncertainties were greatest on the dose to the small intestine. The deviation due to 3 mm reconstruction uncertainty of tandem applicator, ring applicator, and both tandem and ring applicators was 090%, 162%, and 174% for D90 of CTV, 133%, 153%, and 178% for D2cc of the bladder, 089%, 185%, and 197% for D2cc of the rectum, and 086%, 304%, and 350% for D2cc of the small intestine, respectively. Conclusions Applicator reconstruction uncertainties have certain impacts on the radiation dose of 3D brachytherapy. In order to improve the accuracy of brachytherapy, comprehensive quality control is recommended for applicator reconstruction.