To investigate the influencing factors of strain ratio(SR) value in differential diagnosis of benign and malignant thyroid nodules by using real-time tissue elastosonography (RTE).

One hundred and seventy-one patients with a total of 171 thyroid nodules were analyzed retrospectively.Their images, including 2D ultrasound, color Doppler flow imaging (CDFI) and RTE were reviewed and conventional ultrasonic features(including the maximum diameter, composition, shape, magin, calcification, intranodular blood flow, depth) and SR value were recorded. Receiver-operating characteristic (ROC) curve was employed to assess the diagnostic efficiency of SR value in differentiating malignant nodules from benign ones. Firstly, the correlation between the aforementioned factors and SR value was assessed by using malignant lesions as the research subjects. And then, the multiple linear regressions (MLR) was employed to evaluate the influence of particular features which turned out to be an important disturbing factor affecting SR value of the lesion in the first step of analysis and pathological type in all nodules (benign and malignant) on SR value.

With a cut-off point of SR value 3.67, the sensitivity and specificity of SR value in differential diagnosis of benign and malignant thyroid nodules was 85.6% and 81.1%, respectively, and the area under ROC curve was 0.891. Correlation between the maximum diameter and calcification and SR value was significant(r=0.345 and 0.261 respectively, P<0.05). However, there was no significant correlation between other features(5 factors) and SR value(P≥0.05). MLR indicated that the maximum diameter, calcification and the type of pathology of the nodule were associated with SR value (P<0.05). Among them, pathological nature was the most significant impact factor with a standardized coefficient 0.494).

SR value can be used to evaluate the hardness of thyroid nodules semi-quantitatively.Its value mainly depends on the pathological nature of the nodules. The maximum diameter and calcification are also the influencing factors of SR value.However, the composition, shape, margin, intranodular blood flow and depth have no obvious effect on SR value.

Elasticity imaging techniques; Thyroid nodule; Strain ratio