目的 探讨CT图像和CT/MR弥散加权成像(diffusion weighted imaging,DWI)图像融合在食管癌靶区勾画中的应用价值。方法 收集2017-08至2018-12医院收治的26例食管鳞癌患者,进行常规CT扫描及 MR DWI,扩散敏感梯度b值取为600 s/mm2,分别在CT图像和CT/MR DWI融合图像上勾画食管原发肿瘤大体体积(gross tumor volume,GTV)和PTV,计算GTV和PTV的长度,并利用TiGRT治疗计划系统获得GTV与PTV体积,以同样的处方剂量及危及器官限制剂量分别在两种图像上制定治疗计划,比较不同计划的GTV和PTV长度、体积、处方剂量和危及器官的剂量差异。结果 两种条件下计划的剂量分布和各项参数均达到了临床处方剂量要求。而在CT/MR DWI计划下的PTV、GTV的长度和体积均小于CT计划(P=0.00、0.00、0.01、0.03)。基于DWI计划的危及器官肺部平均剂量明显低于CT计划(P=0.00)。结论 DWI在食管癌放疗中的应用更精确,能够保护正常组织。
Abstract
Objective To explore the differences between CT images and CT and nuclear magnetic resonance (MRI) images in the delineation of target areas of esophageal cancer.Methods Twenty-six patients with esophageal squamous cell carcinoma were enrolled between August 2017 and December 2018. Routine CT scan and diffusion-weighted imaging (DWI) were performed. The diffusion-sensitive gradient b value was 600 s/mm2. The esophagus was delineated on CT images and CT/MR DWI fusion images. Cancer GTV and PTV were delineated on these images before their lengths were calculated. The TiGRT treatment planning system was used to obtain the volumes of GTV and PTV, so that treatment plans were made on the two images at the same prescription dose and end-of-life restricted doses. The length, volume, prescription dose and dose difference related to GTV and PTV were compared between different plans. The paired sample t test was performed to calculate the P value.Results The planned dose distribution and parameters under both conditions met the clinical prescription dose requirements. The length and volume of PTV and GTV under the CT/MR DWI plan were smaller than those under the CT plan (P=0.00, 0.00, 0.01, 0.03). The mean dose of the lung in critical organs based on the DWI plan was significantly lower than on the CT plan (P=0.00).Conclusions The application of DWI in radiotherapy of esophageal cancer is more accurate and beneficial for the protection of normal tissues.
关键词
食管癌 /
弥散加权成像 /
体层摄影术 /
靶区体积 /
靶区勾画
Key words
esophageal cancer /
diffusion-weighted magnetic resonance imaging;tomography /
target volume;target delineation
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