Phantom experiment and clinical utility of quantitative shear wave elastography for differentiating thyroid nodules

Shear wave elastography (SWE) using acoustic radiation force impulse (ARFI) is a novel ultrasonography technique. The aim of this study was to investigate the clinical usefulness of quantitative SWE for differentiating thyroid nodules. For phantom study, we measured the shear wave velocities (SWVs) of the four spheres of 2- and 1-cm diameters with varying hardness. For clinical study, the SWVs of normal thyroid glands and thyroid nodules, that were classified as benign or malignant according to either cytological or pathological findings, were measured. The SWVs of each thyroid patient were compared with that of a normal thyroid and each other. In phantom study, the SWVs for the 2-cm spheres correlated with the hardness of the targets, whereas the values for the 1-cm spheres did not. In clinical study, 112 nodules identified in 167 patients and 94 normal thyroid glands were analyzed according to the criteria for the study. The nodules included 84 benign nodules, and 28 papillary carcinoma. The mean SWVs of each group were 1.64 ± 0.47 m/s for normal thyroid, 1.88 ± 0.62 m/s for benign nodules and 2.67 ± 0.76 m/s for papillary carcinoma. The SWVs of papillary carcinoma were significantly higher than those of benign nodules (P < 0.001). The area under the ROC curve was 0.809 with a cut-off value of 2.01 m/s. The sensitivity and specificity were 85.7% and 62.0% respectively. Results showed that SWE provides new information on tumor characteristics, such as hardness and larger nodules tended to provide stable measurements.