CT及3．0T MRI在食管癌IMRT中的价值

Significance of computed tomography and 3.0 T magnetic resonance imaging in intensity-modulated radiotherapy for esophageal carcinoma

目的 探讨CT及3.0T MRI在食管癌IMRT计划中的价值。方法 选取2013—2015年本院放疗科首次确诊并行根治性IMRT的食管癌患者35例,分别在CT及MRI T2WI与DWI融合图像上勾画靶区,以相同处方剂量和OAR限制剂量分别制定计划,比较2种计划的靶区体积、处方剂量及OAR受量差异。配对t检验差异。结果 2种计划的剂量分布及计划参数均达到了临床处方剂量要求。基于3.0T MRI计划的病灶长度、VGTV和VPTV均小于CT计划（P=0.00、0.03、0.03）。2种计划的PGTV、PTV-PGTV的D2%、D98%、D50%、HI、CI差异均无统计学意义（P均〉0.05）。基于3.0T MRI计划的双肺平均剂量明显低于CT计划（P=0.00）,双肺实际受量亦与CT计划相近（P均〉0.05）。2种计划的脊髓最大耐受量及心脏耐受量相近（P均〉0.05）。结论 基于CT及3.0T MRI计划所勾画的靶区及参数均能满足临床需求,但基于3.0T MRI计划的靶区体积更小,可能会使部分OAR潜在获益。

Objective To investigate the significance of computed tomography （CT） and 3.0 T magnetic resonance imaging （MRI） in intensity-modulated radiotherapy （IMRT） for esophageal carcinoma. Methods Thirty-five patients newly diagnosed with esophageal carcinoma who received radical radiotherapy in our hospital from November 2013 to April 2015 were enrolled as subjects. Target volume was delineated on the CT images and MRI images （T2-weighted and diffusion-weighted fusion images）. The MRI-and CT-based IMRT plans were designed using the same dose prescription and dose constraints for organs at risk （OAR）. The target volume,prescribed dose,and doses for OAR were compared between the two plans. Resutls In the two plans,dose distribution and planning parameters met the clinical requirement. The length of lesion,gross tumor volume （GTV）,and planning target volume （PTV） defined by 3.0 T MRI were significantly smaller than those defined by CT （P=0.00,0.03,0.03）. There were no significant differences in the D2%,D98%,D50%,homogeneity index,or conformity index for primary GTV （PGTV） and PTV-PGTV between the two plans （all P〉0.05）. Compared with the CT-based plan,the 3.0 T MRI-based plan had a significantly smaller mean dose to the lungs and an insignificantly smaller actual dose to the lungs （P=0.00;P〉0.05）. There were no significant differences in maximum doses tolerated by the spinal cord or heart between the two plans. Conclutions In terms of target volume delineation and dosimetric parameters,both CT-and 3.0 T MRI-based plans meet the clinical requirement. The 3.0 T MRI-based plan may provide potential benefits for some OAR due to a smaller target volume compared with the CT-based plan.