Abstract
Conventional ultrasound cannot satisfactorily distinguish malignant and benign thyroid nodules. Shear-wave elastography (SWE) can evaluate tissue stiffness and complement conventional ultrasound in diagnosing malignant nodules. However, calcification of nodules may affect the results of SWE. The purposes of this study are to compare the differences of shear-wave speed (SWS) measurement among different calcification groups and compare the diagnostic performance between using a single uniform SWS cutoff value and multiple individual calcification-specific cutoff values using technique of point SWS measurement. We retrospectively identified 517 thyroid nodules (346 benign and 171 malignant nodules) examined by conventional ultrasound and point SWS measurement. There were 177 non-calcified, 159 micro-calcified and 181 macro-calcified nodules. The diagnostic performance was evaluated by receiver operating characteristic (ROC) curve and area under the curve (AUC) was computed. The mean SWS in malignant nodules more than doubled that of benign nodules (4.81±2.03 m/s vs. 2.29±0.99 m/s, p<0.001). The mean SWS of nodules progressively increased from the non-calcification (2.60±1.49 m/s), to micro-calcification (3.27±1.85 m/s) and to macro-calcification (3.68±2.26 m/s) groups (p<0.001), which was true in both the benign and malignant nodules. If we used individual SWS cutoff values for non- (SWS >2.42 m/s), micro- (SWS >2.88 m/s) and macro-calcification (SWS >3.59 m/s) nodules in the whole group, the AUC was 0.859 (95% confidence interval [CI], 0.826-0.888), which was significantly better than the AUC of 0.816 (95% CI, 0.780-0.848) if a single uniform cutoff value (SWS >2.72 m/s) was applied to all the nodules regardless of calcification status (p=0.011). The cutoff values of SWS for different calcified nodules warrant future prospective validation.
Highlights
The incidences of thyroid nodules and thyroid cancer are increasing worldwide, largely due to enhanced diagnostic practices [1,2,3,4]
Conventional ultrasound imaging characteristics associated with malignant nodules include the presence of micro-calcifications, hypoechogenicity, size greater than 2 cm, taller-than wide shape, and an entirely solid composition [6], but these features have varing sensitivity and specificity for diagnosing malignant thyroid nodules [7]
The purposes of this study were to compare the differences of shear-wave speed (SWS) on point shear-wave speed (pSWS) measurement among nodules with different calcifications and to compare the diagnostic performance between a single cutoff value and individually defined cutoff values of SWS in diagnosing malignant thyroid nodules
Summary
The incidences of thyroid nodules and thyroid cancer are increasing worldwide, largely due to enhanced diagnostic practices [1,2,3,4]. There have been many studies evaluating whether elastography, a non-invasive ultrasound method to measure tissue stiffness, can complement conventional ultrasound in differentiating malignant from benign nodules [8]. SWE includes shear-wave speed (SWS) imaging and point shear-wave speed (pSWS) measurement, which can evaluate the tissue stiffness qualitatively and quantitatively by monitoring the SWS propagation in tissues [9, 10]. A number of studies [11,12,13,14] have shown that SWE is a promising complementary ultrasound technique for differentiating malignant and benign thyroid nodules. The purposes of this study were to compare the differences of SWS on pSWS measurement among nodules with different calcifications (non-, micro-, and macrocalcification) and to compare the diagnostic performance between a single cutoff value and individually defined cutoff values of SWS in diagnosing malignant thyroid nodules
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