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目的 评估18F-FDG PET/CT显像对直肠癌区域淋巴结转移的诊断价值.方法 纳入2013年5月至2015年5月48例直肠癌患者(男37例,女11例,平均年龄59.7岁),术前均行18F-FDG PET/CT显像,在PET/CT图像上测量区域淋巴结长径、短径及SUVmax,将目标淋巴结同术后病理对照,确定转移性、非转移性淋巴结.2组间长径、短径、SUVmax比较采用两样本t检验;绘制ROC曲线,计算AUC,确定上述指标最佳诊断界值,比较不同指标及指标组合诊断直肠癌区域淋巴结转移的灵敏度、特异性和准确性.结果 48例患者共切除淋巴结739枚,其中204枚(转移性淋巴结88枚,非转移性淋巴结116枚)可与PET/CT图像上淋巴结准确匹配.以SUVmax≥2.5为转移性淋巴结诊断标准,灵敏度、特异性、准确性分别为38.6％(34/88)、95.7％(111/116)、71.1％ (145/204).非转移性淋巴结、转移性淋巴结的长径分别为(6.13±1.94)和(8.49±3.78) mm,短径分别为(4.73±1.51)和(6.37±2.57) mm,SUVmax分别为1.13±0.74和2.54± 1.76,二者间差异均有统计学意义(t=-5.788、-5.691和-7.775,均P＜0.01).淋巴结长径、短径和SUVmax判断淋巴结转移的ROC AUC分别为0.709、0.731和0.851;最佳界值分别为7.50 mm、5.05 mm和1.45.分别以各界值为诊断标准,基于单个淋巴结的灵敏度分别为:54.5％(48/88)、67.0％(59/88)和68.2％(60/88),特异性分别为:86.2％(100/116)、85.3％ (99/116)和87.9％ (102/116),准确性分别为:72.5％(148/204)、77.5％(158/204)和79.4％ (162/204).将短径≥5.05 mm、SUVmax≥1.45二者满足其一作为转移性淋巴结诊断标准,基于单个淋巴结的灵敏度、特异性、准确性分别为:84.1％(74/88)、83.6％ (97/116)和83.8％(171/204).结论 18F-FDG PET/CT显像对直肠癌区域淋巴结转移的诊断有重要价值,SUVmax≥1.45为诊断标准的诊断价值优于长径≥7.50 mm、短径≥5.05 mm;SUVmax≥1.45、短径≥5.05 mm二者满足其一作为转移性淋巴结诊断标准时准确性最高.“,”Objective To evaluate the diagnostic value of 18F-FDG PET/CT imaging in detection of regional lymph node metastasis in patients with rectal cancer.Methods A total of 48 patients (37 males,11 females;average age 59.7 years) with rectal cancer who underwent preoperative PET/CT examination from May 2013 to May 2015 were enrolled.The long diameter,short diameter and SUVmax of lymph nodes on axial images were recorded.Metastatic lymph nodes (MLN) and non-metastatic lymph nodes (NMLN) were confirmed by postoperative pathology.Two-sample t test was used to compare the diameters and SUVmax between 2 groups;ROC curve was drawn to determine the optimal cutoff value and to assess the sensitivity,specificity,and accuracy of each index for differentiating MLN from NMLN.Results A total of 739 lymph nodes were resected,204 lymph nodes (88 MLN and 116 NMLN) were matched with those on PET/ CT images.The long diameters of NMLN and MLN were (6.13±1.94) mm and (8.49±3.78) mm,respectively,and the short diameters were (4.73±1.51) mm and (6.37±2.57) mm,respectively(t=-5.788,-5.691,both P＜0.01).The SUVmax of NMLN and MLN were 1.13±0.74 and 2.54±1.76,respectively(t=-7.775,P＜ 0.01).For long diameter,short diameter and SUVmax,the ROC AUCs were 0.709,0.731 and 0.851 respectively,the optimal cutoff values were 7.50 mm,5.05 mm and 1.45 respectively,with the corresponding sensitivities of 54.5％ (48/88),67.0％ (59/88) and 68.2％ (60/88),specificities of 86.2％ (100/116),85.3％(99/116) and 87.9％ (102/116),accuracies of 72.5％ (148/204),77.5％ (158/204) and 79.4％ (162/204).When a lymph node with SUVmax ≥ 1.45 or short diameter ≥ 5.05 mm was considered malignant,the sensitivity,specificity and accuracy were 84.1％ (74/88),83.6％ (97/116) and 83.8％ (171/ 204),respectively.Conclusions 18F-FDG PET/CT imaging has significant value in detection of regional lymph node metastasis in patients with rectal cancer.The SUVmax ≥ 1.45 showed better diagnostic value than short diameter≥ 5.05 mum and long diameter≥7.50 mm.The highest diagnostic accuracy could be achieved,if SUVmax ≥ 1.45 or short diameter≥5.05 mm is considered as the diagnostic criterion for lymph node metastasis.