Objective To define an optimal maximum standardized uptake value (SUVmax) threshold of 18F-fluorodeoxygluose (18F-FDG) in delineating metabolic tumor volume of cervical cancer by comparing positron emission tomography and computed tomography (PET/CT) with pathological volume of the tumor.Methods Twelve patients with cervical cancer prospectively underwent a PET/CT scan.Different SUVmax thresholds,including 10％,15％,20％,25％,30％,35％,40％,45％ and 50％,were screened from PET images to obtain the corresponding PET metabolism gross tumor volume (GTV).Pathological slices were prepared after the operation for determination of the edge and area of the tumor.Pathological tumor volumes were measured from each slice,and they were then combined to derive the pathological GTV.An optimal PET GTV was defined when PET GTV was closest to the pathological tumor volume,and SUVmax threshold corresponding to the optimal PET GTV was named as the optimal SUVmax threshold.Results The optimal SUVmax threshold was between 30％ and 50％ with an mean value of 40.83％ ± 6.07％ in all the 12 patients.There was no significant statistical difference between the pathological GTV and PET GTV with a SUVmax threshold of 41％(P=0.352),and they were well correlated with each other with a coefficient of 0.99(P=0.000).Conclusions PET optimal SUVmax threshold derived by comparison with pathological GTV is of great significance in improving the curative effect of intensified modulated radiation therapy (IMRT).%目的 通过18F-氟代脱氧葡萄糖正电子发射型计算机断层扫描仪(18F-FDG PET/CT)代谢体积与病理体积的比较,确定宫颈癌最大标准摄取值(SUMmax)的最佳百分阈值.方法 12例宫颈癌患者术前行PET/CT,经PET图像选取肿瘤SUVmax的10％、15％、20％、25％、30％、35％、40％、45％、50％等不同阈值勾画肿瘤边界,生成相应的PET大体肿瘤体积(PET GTV).术后进行病理切片,确定每层切片肿瘤边缘及面积,由面积乘以切片厚度计算每张切片的肿瘤体积,累积所有切片的肿瘤体积作为全部肿瘤的病理大体体积(病理GTV).将与肿瘤病理GTV最接近的PET GTV确定为最佳PET GTV值,将其对应的SUVmax阈值称为最佳百分阈值.结果 12例患者的最佳SUVmax阈值为40.83％±6.34％(30％～50％).以SUVmax的41％阈值勾画肿瘤边界所得PET GTV与病理GTV比较,差异无统计学意义(P=0.352),并且两者有较好的相关性(r=0.99,P=0.000).结论 通过病理体积确定的PET最佳SUVmax阈值能准确指导宫颈癌靶区的勾画,对提高三维适形调强放疗疗效具有重要意义.
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