目的 探讨18F-FDG PET/CT联合MRI评估直肠癌侧方淋巴结转移的应用价值。方法 回顾性分析51例直肠癌患者病理 证实的转移性、非转移性淋巴结33、45枚，比较两组间短径、SUVmax、ADC值，探讨不同指标及指标组合的诊断价值。 结果 PET/CT、MRI测量转移性、非转移性淋巴结短径差异无统计学意义（P>0.05），分别以MRI短径≥6.75 mm、PET/ CT短径≥5.05 mm为转移性淋巴结诊断标准，两者灵敏度、特异性、准确性差异不大（P>0.05）丨将PET/CT短径≥5.05 mm 联合T2WI信号不均联合诊断，灵敏度、特异性、准确性明显提高（P<0.05）丨非转移性淋巴结、转移性淋巴结ADC值、 SUVmax值差异无统计学意义（P>0.05）。分别以SUVmax≥1.45、ADC值≤1.049为转移性淋巴结诊断标准，两者灵敏度、特 异性、准确性差异不大（P>0.05）丨而SUVmax≥1.45联合ADC值≤1.049×10-3 mm2/s诊断转移性淋巴结灵敏度、特异性、准 确性明显提高（P<0.05）。结论 18F-FDG PET/CT联合MRI多模态显像在直肠癌侧方淋巴结转移有较高的临床应用价值，为 疗前分期提供更准确N分期信息。

Objective To investigate the application value of 18F-FDG PET/CT combined with MRI to evaluate for the assessment of lateral lymph node metastasis in rectal cancer. Methods Retrospective analyzed 33 and 45 metastatic and non-metastatic lymph nodes confirmed by surgical pathology in 51 rectal cancer patients, compared to the short diameter, SUVmax, and ADC values between the two groups, and explored the diagnostic value of different indexes and combinations indexes. Results There were no statistically significant differences in the measurement of metastatic and non-metastatic lymph node short diameters of PET/CT and MRI (P>0.05). MRI short diameter ≥6.75 mm and PET/CT short diameter≥5.05 mm were the diagnostic criteria for metastatic lymph nodes, the difference in specificity and accuracy is not significant (P>0.05). Combined diagnosis of PET/CT short diameter ≥5.05 mm combined with T2WI signal unevenness, its sensitivity, specificity and accuracy were significantly improved (P<0.05). The difference in ADC values and SUVmax values of non-metastatic lymph nodes and metastatic lymph nodes were not statistically significant (P>0.05). SUVmax ≥1.45 and ADC value≤1.049 were used as the diagnostic criteria for metastatic lymph nodes, respectively, while the sensitivity, specificity and accuracy of SUVmax≥1.45 combined with ADC value≤1.049×10-3 mm2/s for the diagnosis of metastatic lymph nodes were significantly improved (P<0.05). Conclusion 18F-FDG PET/CT combined with MRI multi-modality imaging has high clinical application value in lateral lymph node metastasis of rectal cancer, and provides more accurate N staging information for pre-treatment staging.