MRI影像与CT影像勾画宫颈癌三维腔内后装放疗靶区体积的比较

Comparison of the target volumes delineated by MRI and CT images in patients with cervical cancer who received 3D intracavitary brachytherapy

目的探讨在宫颈癌三维腔内后装放疗中,MRI影像与CT影像勾画大体肿瘤体积(GTV)的差异。方法选取2012年9月至2016年7月联勤保障部队第九〇〇医院收治的经组织病理学等结果确诊为宫颈癌Ⅱb~Ⅲb期的患者12例,年龄50~64岁。所有患者接受外照射及三维腔内后装放疗后行CT和MRI扫描,在OMP计划系统上进行影像融合,由3位放疗科医师分别在CT和MRI图像上2次勾画GTV,包括子宫体、子宫颈及宫颈原发病灶。CT、MRI图像分别勾画得到36个GTV(称为GTVCT、GTVMRI),计算GTVMRI与GTVCT的比值R,其差异比较采用配对t检验。结果GTVCT为(93.8±11.8)cm^3,GTVMRI为(71.1±3.1)cm^3。3位医师勾画的GTVCT、GTVMRI最大与最小体积的差值分别为41.3 cm^3、11.3 cm^3。与医师3相比,医师1、2分别勾画的GTV均较大,比值R之间的差异均有统计学意义(t=−8.644、−5.043,均P=0.000)。3位医师勾画的GTVMRI更接近,靶区体积受人为因素影响更小。结论CT影像引导的三维腔内后装放疗,受人为因素等影响,勾画GTV存在差异,应用MRI和CT影像融合技术可缩小这种差异。

Objective To investigate and compare the gross tumor volumes(GTVs)delineated by MRI and CT images in patients with cervical cancer who received 3D intracavitary brachytherapy.Methods A total of 12 patients,aged 50–64 years,who were confirmed to have cervical squamous cell carcinoma or adenocarcinoma by biopsy and pathology between September 2012 and June 2016 were selected in the 900 Hospital of the Joint Logistics Team.The tumor was staged during the second and third phases.All the patients underwent pelvic MRI which was administered through external beam radiation followed by a 3D CT-based high dose rate(HDR)intracavitary brachytherapy boost.After radiotherapy CT localization,the CT and MRI images were fused.Next,in the OMP system,three experienced radiologists(radiologists 1,2,and 3)respectively delineated the GTVs,which included the cervix uterus,corpus uteri,and primary lesion.Thirty-six target outlines were drawn based on the CT images(called GTVCT),and another 36 target outlines were drawn based on the MRI images(called GTVMRI).The ratio R of GTVMRI and GTVCT were calculated using the paired t-test to compare the difference between the two groups.Results The average target volume of GTVCT(93.8±11.8)cm^3 was larger than that of GTVMRI(71.1±3.1)cm^3.Some variations were observed among the definition results given by the three radiologists.The differences between the maximum volume and the minimum volume were 41.3 cm^3 and 11.3 cm^3 for GTVCT and GTVMRI,respectively.Compared with Radiologist 3,Radiologists 1 and 2 outlined that the volume of GTV is larger,and the difference between the ratios R is statistically significant(t=−8.644,−5.043,both P=0.000).The difference in target volumes between the radiologists guided by MRI images was smaller than that by the radiologist guided by CT images and was more slightly affected by individual factors.Conclusions For patients with cervical cancer who are administered external beam radiation followed by 3D CT-based HDR brachytherapy boost,variations in GTVs were observed among different radiologists for individual factors.The CT/MRI-fusion technology may decrease the variation in target volume between different radiologists.