The application of qualitative shear wave elastography in differential diagnosis of thyroid nodules

Objective: To investigate the diagnostic performance of qualitative shear wave elastography (SWE) in the characterization of thyroid nodules, compared with quantitative SWE and grayscale ultrasound (US). Methods: A total of 174 thyroid nodules from 174 patients were preoperatively evaluated by grayscale US and SWE. The quantitative SWE metrics were measured. For the qualitative SWE analysis, a four-pattern classification was established according to the color distribution features of the elastic maps and assigned for each enrolled nodule, as 1 for no meaningful findings, 2 for a capsule-related color, 3 for marginal color, and 4 for interior color. Results: Intraobserver and inter-observer agreement of the qualitative classification proposed in this study were substantial (kappa=0.793 and 0.756, respectively). The area under the receiver operating characteristic curve (AUC) of the proposed classification was similar to that of grayscale US (P=0.73) and quantitative SWE metrics (P=0.90). Compared with the quantitative SWE, the qualitative classification yielded a higher sensitivity (P < 0.05) and a similar specificity (P=0.75). Adding SWE features to grayscale US, either qualitatively or quantitatively, improved the overall specificity (both P < 0.001). Among all data sets, the optimal diagnostic performance came from the combined set of grayscale US and the qualitative classification (AUC, 0.890), with 84.4% sensitivity and 94.6% specificity. Conclusion: The qualitative four-pattern classification proposed in this study was feasible and highly reproducible in the SWE evaluation of thyroid nodules. SWE imaging features, especially the qualitative classification, have the potential to facilitate ultrasound diagnosis for thyroid nodules.