诊断PET-CT用于食管癌原发肿瘤大体肿瘤体积勾画的比较研究

目的 比较单纯参考诊断¹⁸F-FDG PET-CT（PET-CT）在3D-CT上勾画的食管原发肿瘤大体肿瘤体积（GTV）与利用3D-CT和诊断PET-CT形变配准后勾画的GTV体积和位置差异。方法 选择在本院行同步放化疗的胸段食管癌患者72例，所有患者放疗前均行诊断PET-CT扫描和常规3D-CT模拟定位扫描。单纯基于常规3D-CT勾画GTV定义为GTV_3D，参考诊断PET-CT在3D-CT上勾画的GTV定义为GTV_PET-ref，基于3D-CT和诊断PET-CT形变配准图像上勾画的GTV定义为GTV_PET-reg。比较3种GTV剂量指标间的差异。结果 全组患者GTV_3D、GTV_PET-ref、GTV_PET-reg靶区中位体积分别为44.90、40.36、41.15 cm³，各靶区间体积大小差异无统计学意义（P>0.05）。三者靶区平均长度分别为8.54、9.29、8.38 cm，GTV_PET-ref>GTV_3D（t=2.134，P<0.05）。GTV_PET-ref对GTV_3D、GTV_PET-reg对GTV_3D的中位包含度（DI）值分别为0.86、0.82，两者间差异有统计学意义（Z=-2.741，P<0.05）；GTV_3D对 GTV_PET-ref、GTV_3D对GTV_PET-reg的中位DI值分别为0.87、0.84，两者间差异有统计学意义（Z=-1.429，P<0.05）。GTV_3D与GTV_PET-ref、GTV_3D与GTV_PET-reg的中位适形指数（CI）值分别为0.72、0.68，两者间差异有统计学意义（Z=2.756，P<0.05）。GTV_3D与GTV_PET-ref、GTV_3D与GTV_PET-reg、GTV_PET-ref与GTV_PET-reg的CI与靶区中心间距均呈显著负相关（P<0.05）。结论 参考诊断PET-CT在靶区体积大小及靶区空间位置与基于诊断PET-CT形变配准所勾画食管癌原发肿瘤GTV差异均无统计学意义，因此，建议放疗医生可以参照治疗前近期的诊断PET-CT勾画食管癌原发肿瘤GTV。

Comparison of the gross target volume based on diagnostic PET/CT for primary esophageal cancer

Objective To compare positional and volumetric differences between the gross target volumes (GTV) delineated on three-dimensional CT (3D-CT) referencing ¹⁸F-FDG PET/CT and the GTV on the deformed image derived from 3D-CT and ¹⁸F-FDG PET/CT for primary thoracic esophageal cancer (EC). Methods Seventy-two patients underwent chemoradiotherapy were enrolled. All the patients sequentially underwent ¹⁸F-FDG PET/CT scans for diagnosis and 3D-CT scans for simulation. The GTV_3D was delineated on 3D-CT without referencing ¹⁸F-FDG PET/CT. The GTV_PET-ref was delineated on 3D-CT referencing ¹⁸F-FDG PET/CT. The GTV_PET-regwas delineated on the deformed image derived from 3D-CT and ¹⁸F-FDG PET/CT by MIM deformable registration software. The differences in position, volume, length, conformity index (CI), and degree of inclusion (DI) of target volumes were compared, respectively. Results The median volume of GTV_3D, GTV_PET-ref, GTV_PET-reg were 44.90, 40.36 and 41.15 cm³, respectively. There was no statistical difference between the volumes of any two targets. The mean lengths of GTV_3D, GTV_PET-ref, GTV_PET-reg were 8.54, 9.29 and 8.38 cm, respectively. The length of GTV_PET-ref was longer than that of GTV_3D(t=2.134,P<0.05).The median DIs of GTV_PET-ref, GTV_PET-regin GTV_3D were 0.86, 0.82(Z=-2.741,P<0.05), and that of GTV_3D in GTV_PET-ref, GTV_PET-reg were 0.87, 0.84 (Z=-1.429,P<0.05). The median CIs of GTV_3D in GTV_PET-ref and GTV_PET-reg were 0.72,0.68 (Z=2.756,P<0.05), and the difference was significant. The CIs of GTV_3D and GTV_PET-ref, GTV_3D and GTV_PET-reg, GTV_PET-ref and GTV_PET-reg had significant negative correlation with the distance of target centers. Conclusions There was no significant difference between GTV contoured on three-dimensional CT (3D-CT) referencing ¹⁸F-FDG PET/CT and the GTV on the deformed image derived from 3D-CT and ¹⁸F-FDG PET/CT either in volume size or in spatial position. Therefore, it is recommended that radiation oncologists can refer to the recent diagnostic PET/CT when delineating the gross target volume for primary thoracic esophageal cancer.