To study the application of strain ratio in differentiation of benign and malignant thyroid nodules through analyzing the influencing factors of the elastic strain ratio (SR) of thyroid nodules.

There were 468 patients with 476 thyroid nodules in present study, who came from the Nanjing Drum Tower Hospital from January 2012 to February 2014. SR characteristics of thyroid nodules were retrospectively analyzed, and the critical values were found by receiver-operating characteristic (ROC) curve. Then the size, echo, calcification, blood flow and the correlation between SR and pathology were analyzed by Pearson bivariate correlation analysis.

The ROC curve showed that SR=0.5 was the best threshold value of SR in differential diagnosis of benign and malignant thyroid nodules. The diagnostic sensitivity, specificity, and the area under the curve were 84.8%, 85.9%, and 0.894, respectively. SR was negatively correlated with echo and calcification, while positively correlated with nodule size and blood flow (r=0.158, P=0.001; r=-0.209, P=0.000; r=-0.218, P=0.000; r=0.189, P=0.000; r=-0.519, P=0.000). The pathology of thyroid nodules had no correlation with nodule size and blood flow (r=-0.025, P=0.582; r=-0.070, P=0.126). The pathology was positively correlated with echo and calcification, while negatively correlated with age (r=0.265, P=0.000; r=0.185, P=0.000; r=-0.207, P=0.000; r=-0.519, P=0.000).

To improve the accuracy of diagnosis, the differential diagnosis of benign and malignant thyroid nodules should be based on two-dimensional ultrasound combined with SR and fine needle aspiration.