3DCT、4DCT和PET-CT定义的胸段食管癌PTV比较研究

目的 探讨基于PET-CT图像SUV≥2.5、20%或25%SUV_max与基于3DCT、4DCT构建的胸段食管癌PTV位置及体闫积差异性。方法 18例胸段食管癌患者序贯完成3DCT、4DCT、FDG PET-CT 胸部定位扫描。3DCT图像常规外扩获得PTV_3D;PTV_4D通过10个时相靶区融合获得;基于SUV≥2.5、20%或25%SUV_max分别得到IGTV_PET2.5、IGTV_PET20%、IGTV_PET25%,分别将这3个靶区上下方向外扩3.5 cm,左右前后方向外扩1 cm得到PTV_PET2.5、PTV_PET20%、PTV_PET25%。结果 PTV_3D体积显著大于PTV_4D和PTV_PET(P=0.000~0.044),而PTV_PET和PTV_4D相近(P=0.216~0.633)。PTV_3D、PTV_4D相互间DI分别为0.70、0.95,同三维运动矢量呈负相关(P=0.039)。PTV_PET2.5、PTV_PET20%、PTV_PET25%相互间DI分别为0.74、0.72、0.78、0.73、0.77、0.70,同三维运动矢量无相关性(P=0.150~0.822)。PTV_3D、PTV_PET间相互DI分别为0.86、0.84、0.88、0.63、0.67、0.59。结论 由于各自所包含的靶区信息差异等原因,基于3DCT、4DCT及PET-CT构建的胸段食管癌PTV在空间上很难达到完全重合。利用自由呼吸状态下PET扫描图像来构建胸段食管癌PTV尚需慎重。

A comparative study of planning target volumes based on three-dimensional computed tomography,four-dimensional computed tomography,and positron emission tomography-computed tomography in thoracic esophageal cancer

Objective To investigate the differences in position and volume between planning target volumes (PTV) based on positron emission tomography-computed tomography (PET-CT) images with an standardized uptake value (SUV) no less than 2.5, 20% of the maximum SUV (SUV_max), or 25% of SUV_max, three-dimensional (3D) CT, and four-dimensional (4D) CT in thoracic esophageal cancer. Methods Eighteen patients with thoracic esophageal cancer sequentially received chest 3DCT, 4DCT, and[18F]fluoro-2-deoxy-D-glucose (FDG) PET-CT scans. PTV_3D was obtained by conventional expansion of 3DCT images;PTV_4D was obtained by fusion of target volumes from 10 phases of 4DCT images. The internal gross tumor volumes (IGTV), IGTV_PET2.5, IGTV_PET20%, and IGTV_PET25%, were generated based on PET-CT images with an SUV no less than 2.5, 20% of SUV_max, and 25% of SUV_max, respectively. These IGTVs were expanded longitudinally by 3.5 cm and radically by 1 cm to make PTV_PET2.5, PTV_PET20%, and PTV_PET25%, respectively. Results PTV_3D was significantly larger than both PTV_4D and PTV_PET(P=0.000－0.044), while there was no significant difference between PTV_4D and PTV_PET(P=0.216－0.633). The mutual degrees of inclusion (DIs) between PTV_3D and PTV_4D were 0.70 and 0.95, respectively, which were negatively correlated with 3D-Vector (P=0.039). The mutual DIs between PTV_PET2.5, PTV_PET20%, and PTV_PET25% were 0.74, 0.72, 0.78, 0.73, 0.77, and 0.70, respectively, which showed no correlation with 3D-Vector (P=0.150－0.822). The mutual DIs between PTV_3D and PTV_PET were 0.86, 0.84, 0.88, 0.63, 0.67, and 0.59, respectively. Conclusions It is difficult to achieve complete volumetric overlap of PTVs based on 3DCT, 4DCT and PET-CT in thoracic esophageal cancer due to different target volume information. PET scan during free breathing should be used with caution to generate PTVs in thoracic esophageal cancer.