基于PET/CT选定阈值与基于4D-CT呼气末时相所勾画非小细胞肺癌原发肿瘤靶区相关性分析

目的 探讨基于PET/CT图像选定阈值与基于4D-CT呼气末时相图像所勾画的非小细胞肺癌(NSCLC)原发肿瘤靶区相关性因素。方法 入组NSCLC患者序贯完成3DCT、4D-CT、¹⁸F-FDG PET/CT胸部定位扫描。基于4D-CT呼气末时相(50%)图像勾画原发肿瘤大体肿瘤体积(GTV_50%)。基于PET图像原发肿瘤标准摄取值(SUV)≥2.0、SUV最大值(SUV_max)的20%勾画内大体肿瘤体积(IGTV)分别命名为IGTV_PET2.0、IGTV_PET20%。分析IGTV_PET2.0、IGTV_PET20%与GTV_50%的体积比(VR_2.0、VR_20%)及适形指数(CI_2.0、CI_20%)与GTV_50%最大横径、GTV_50%体积大小、GTV头脚方向位移、GTV三维运动矢量及SUV_max的相关性。结果 VR_2.0和GTV_50%最大横径、GTV_50%体积大小、GTV头脚方向位移、GTV三维运动矢量及SUV_max均无相关性(P>0.05);VR_20%和GTV_50%体积大小、GTV_50%最大横径及SUV_max呈负相关(r=-0.663、-0.669、-0.752,P<0.05)。CI_2.0和GTV_50%体积大小、GTV_50%最大横径呈正相关(r=0.613、0.483,P<0.05)。结论 3D PET图像是包含了多个呼吸周期的中位图像,未能包含肿瘤的全部运动信息,基于3D PET/CT图像所构建的靶区不能准确地代表NSCLC的IGTV。

Detection of the correlations in target volumes for primary tumor of non-small cell lung cancer based on FDG PET/CT and the end-expiration phase of 4D-CT

Objective To investigate the correlations in target volumes based on positron emission tomography CT (PET/CT) and the end-expiration phase of four-dimensional CT (4D-CT) images for non-small cell lung cancer (NSCLC). Methods Seventeen patients with NSCLC sequentially underwent three-dimensional CT (3DCT), 4D-CT and ¹⁸F-FDG PET/CT thoracic simulation scans. The gross target volume (GTV) was contoured on the end-expiration phase (50%) of 4D-CT and defined as GTV_50%. The internal gross target volumes (IGTV) based on PET/CT images (IGTV_PET) were determined by the standardized uptake value (SUV) 2.0 (IGTV_PET2.0) and 20% percentage of the maximal standardized uptake value (SUV_max) (IGTV_PET20%). The following parameters were calculated to analyze the correlation between IGTV_PET and GTV_50% in volume ratio (VR) and conformity index (CI): maximum transverse diameter of GTV_50%, volume of GTV_50%, the displacement of GTV in the cranial-caudal direction and 3D Vector calculated from 4D-CT dataset as well as the SUV_max. Results There was no significant correlation between the VR of IGTV_PET2.0 to GTV_50% and the maximum transverse diameter of GTV_50%, volume of GTV_50%, the displacement of GTV in the cranial-caudal direction, 3D Vector and the SUV_max(P>0.05). The VR between IGTV_PET20% and GTV_50% inversely related to maximum transverse diameter of GTV_50%, volume of GTV_50% and SUV_max (r=-0.663, -0.669, -0.752, P<0.05). The CI between IGTV_PET2.0 and GTV_50% positively related to volume of GTV_50% and maximum transverse diameter of GTV_50% (r=0.613, 0.483, P<0.05). Conclusions 3D PET images provide a time-averaged image of the tumor during the numerous breathing cycle. They fail to include the full information of moving tumor. The target volumes based on 3D PET might not reflect the real IGTV of NSCLC.