基于4 D-CT的最大密度投影图像与基于PET-CT不同SUV值勾画的胸段食管癌原发肿瘤IGTV比较研究

Comparison of internal gross target volumes delineated on the maximum intensity projection of four-dimensional CT images and positron emission tomography-CT for primary thoracic esophageal cancer

目的：比较基于4D-CT的最大密度投影（MIP）图像与基于18F-FDG PET-CT不同SUV值勾画的胸段食管癌原发肿瘤靶区间的体积大小、适形指数（ CI）和包含度（ DI）。方法15例胸段食管癌患者序贯完成3D-CT、4D-CT、18 F-FDG PET-CT 胸部定位扫描。在4D-CT的MIP图像上勾画食管原发肿瘤的内大体肿瘤体积 IGTVMIP ，在 PET-CT 的 PET 图像上分别选择不同 SUV 阈值（≥2.0、2.5、3.0、3.5）、最大SUV值（SUVmax）的不同百分比（≥20％、25％、30％、35％、40％）及人工视觉观察勾画食管原发肿瘤靶区。结果 IGTVPET 2.5、IGTVPET20％、IGTVPETMAN与IGTVMIP体积比值最接近于1，分别为0.86、0.88、1.06；IGTVPET2.0、IGTVPET2．5、IGTVPET20％、IGTVPET25％、IGTVPETMAN与IGTVMIP间CI分别为0.55、0.56、0.56、0.54、0.55，均明显大于其他 IGTVPET与 IGTVMIP间的 CI 值（Z＝-3.408～2.215，P＜0.05）。 IGTVPET2．5、IGTVPET20％、IGTVPETMAN与IGTVMIP相互间DI值分别为0.77、0.82、0.71和0.67、0.68、0.82，差异均不明显（P ＞0.05）。结论基于PET图像SUV阈值2.5、最大SUV值的20％及人工视觉观察3种方法与基于4D-CT的MIP图像所勾画胸段食管癌原发肿瘤靶区体积大小最接近且空间错位相对较小。

Objective To compare volumetric size, conformity index （CI）, degree of inclusion （DI） of internal gross target volumes （IGTV） delineated on 4D-CT-MIP and PET-CT images for primary thoracic esophageal cancer. Methods Fifteen patients with thoracic esophageal cancer sequentially underwent enhanced 3D-CT, 4D-CT and PET-CT simulation scans. IGTVMIP was obtained by contouring on 4D-CT maximum intensity projection （ MIP）. The PET contours were determined with nine different threshold methods （SUV≥2.0, 2.5, 3.0, 3.5）, the percentages of the SUVmax（≥20%, 25%, 30%, 35%, 40%） and manual contours. The differences in size, conformity index （CI）, degree of inclusion （ DI） of different volumes were compared. Results The volume ratios （ VRs） of IGTVPET2. 5 to IGTVMIP , IGTVPET20% to IGTVMIP, IGTVPETMAN to IGTVMIP were 0.86, 0.88, 1.06, respectively, which approached closest to 1. The CIs of IGTVPET2.0,IGTVPET2.5,IGTVPET20%,IGTVPETMAN and IGTVMIP which were 0.55, 0.56, 0.56, 0.54,0.55, respectively, were significantly larger than other CIs of IGTVPET and IGTVMIP （Z= -3.408-2.215,P 〈0.05）. There were no statistical significance in the DIs of IGTVMIP and IGTVPET2.5,IGTVMIP and IGTVPET20%, IGTVMIP and IGTVPETMAN（0.77,0.82,0.71,0.67, 0.68,0.82,P〉0.05）. Conclusions The targets delineated based on SUV threshold setting of≥2.5, 20% of the SUVmax and manual contours on PET images correspond better with the target delineated on maximum intensity projection of 4D-CT images than other SUV thresholding methods.