Shear Wave Elastography: A New Ultrasound Imaging Mode for the Differential Diagnosis of Benign and Malignant Thyroid Nodules

Abstract

Elastography uses ultrasound (US) to assess elasticity. Shear wave elastography (SWE) is a new technique that estimates tissue stiffness in real time and is quantitative and user independent. The aim of the study was to assess the efficiency of SWE in predicting malignancy and to compare SWE with US. Ninety-three patients and 39 control subjects were included in the study. Predictive value of SWE was assessed by correlation between elasticity, US parameters, and histology. Elasticity index (EI) was first analyzed alone. Scores have been constructed with echographic parameters, i.e. vascularity, hypoechogenicity, and microcalcifications (Score 1=US Score), and with the same parameters plus EI (Score 2=US+SWE Score). For statistical analysis, univariate and multivariate analysis and receiver operating characteristic curves were used. A total of 146 nodules from 93 patients were analyzed. Twenty-nine nodules (19.9%) were malignant. Mean (±sd) EI was 150±95 kPa (range, 30-356) in malignant nodules vs. 36±30 (range, 0-200) kPa in benign nodules (P<0.001, Student's t test). For a positive predictive value of at least 80%, characteristics of tissue elasticity (cutoff, 65 kPa) were: sensitivity=85.2%, and specificity=93.9%. Characteristics of the US Score were: sensitivity=51.9% [95% confidence interval (CI), 33.1; 70.7], and specificity=97% (95% CI, 93.6; 1). Characteristics of the US+SWE Score were: sensitivity=81.5% (95% CI, 66.9; 96.1), and specificity=97.0% (95% CI, 93.6; 1). Promising results have been obtained with SWE. This technique may be applied to multinodular goiters. Larger prospective studies are needed to confirm these results and to define the respective places of SWE, US, and FNA.