ABSTRACT
Objective:To investigate the value of CT enhancement degree in diagnosing cervical lymph node metastasis of papillary thyroid carcinoma (PTC) .Methods:CT data of 535 neck lymph nodes with pathological diagnosis in 251 cases were retrospectively analyzed. The ratio and difference between the density of CT enhancement and plain scan were calculated. Mann-Whitney test was used to analyze the distribution of ratio and difference in lymph node metastasis group and non-metastasis group. The optimal thresholds of ratio and difference in the two groups were obtained by receiver operating characteristic (ROC) curve analysis.Results:535 cervical lymph nodes including 271 in metastatic group and 264 in non-metastatic group. The ratios of two groups were 2.30 (2.04, 2.76) and 1.66 (1.51, 1.81) ( Z=-16.94, P<0.05) respectively, and the differences were 58 (49, 76) Hu and 31 (22, 36) Hu ( Z=-18.045, P<0.05) respectively. When the ROC area under curve of ratio and difference between the two groups were 0.923 and 0.951 respectively, the optimal thresholds were 1.93 and 39.5Hu respectively. The sensitivity and specificity of diagnosing lymph node metastasis were 84.9% and 87.1%、91.5% and 86.0%respectively.The sensitivity and specificity of combination of the two diagnosing lymph node metastasis were 82.3% and 91.7%. Conclusions:The ratio of enhancement and plain scan density ≥1.93 and the difference ≥39.5Hu have a high diagnostic efficiency for cervical lymph node metastasis of PTC. The specificity of the two is similar, but the latter has higher sensitivity. The combination of the two can significantly improve the specificity, thereby reducing unnecessary surgical trauma.