MRI-CT图像融合对颈椎原发肿瘤GTV勾画和剂量学影响

Influence of MRI-CT fusion image on gross tumor volume delineation and dose distribution for radiation of primary tumors of cervical vertebra

目的利用MRI-CT融合图像和CT为基础图像进行靶区勾画比较靶体积和危及器官体积差异，探讨带来的治疗计划剂量学差异。方法2013-2014年颈椎原发肿瘤患者10例，收集患者放疗前我院放射科MRI（GEDiscovery MR7503．0T）图像传输至我科Eclipse系统，与定位CT图像进行融合。比较以MRI-CT融合图像和CT图像为基础进行靶区及OAR勾画体积差异及靶体积差异所致治疗计划剂量分布差异。对不同医师不同影像参考下勾画靶体积、剂量学参数行单因素方差分析或配对t检验，非正态性资料行Wilcoxon秩和检验。组内相关系数（ICC）可靠性分析。结果GTVMRI-CT体积大于GTVCT二者体积重叠指数为0．84±0．17。脊髓MRI-CT体积小于CT的（P=0．001）。5例肿瘤科医师靶区勾画组内相关系数ICCM-CT〉ICCCT。脊髓剂量学参数D～MRI-CT〈DmaxCT（46．00、52．39Gy，P=0．014）。结论MRI-CT融合下的肿瘤靶区勾画不易造成靶区遗漏，不同医师间组间差异在MRI-CT融合图像后减少，并带来剂量学优势。

Objective To compare the differences of gross tumor volume （GTV） and dose distribution between MRI-CT fusion imaging and CT-based imaging and investigate the dose difference in the therapeutic regime. Methods Ten patients diagnosed with primary tumors of the cervical vertebra between 2013 and 2014 were enrolled. Prior to radiotherapy, the imaging data of MRI examination （GE Discovery MR 750 3.0T） were collected, transfered into the Eclipse system and subject to fusion with CT images. GT~ delineation, organ at risk （OAR） delineation and dose distribution discrepancy induced by target volume differences were analyzed and statistically compared between the MRI-CT fusion and CT-based images. GTV delineation and dose parameters among different radiologists between two approches were analyzed by analysis of variance （ANOVA） and paired t-test. Non-normally distributed variables were analyzed by Wilcoxon rank- sum test. The reliability of intraclass correlation coefficient （ICC） was assessed. Results The GTVMRI-CT volume was larger compared with the GTVcT volume. The volume overlap index was 0.84±0. 17.The cordMRI- CT volume was significantly less than the cordcT volume （P= 0. 001 ）. For 5 radiologists, the ICCMm-CT was larger than ICCcT. The DmaxMRI-CT of the spinal cord was （46.00± 1.09） Gy, significantly less than （52.39±1.34） Gy for the DmaxCT（P=0. 014）. Conclusions It is unlikely to miss the target delineation on MRI-CT fusion imaging. MRI-CT fusion imaging can minimize the discrepancy of interobserver radiologists and cause dosimetric advantages.