Differentiation of benign from malignant thyroid lesions: calculation of the strain ratio on thyroid sonoelastography.

OBJECTIVES: Initial data suggest that elastography can improve the specificity of sonography for differentiating benign and malignant thyroid lesions. The primary objective of this study was to compare quantitative sonoelastography to conventional qualitative sonoelastography and sonography for thyroid nodule characterization.

METHODS: Ninety-eight thyroid masses (53 benign and 45 malignant) were examined with conventional sonography and sonoelastography. The images were classified into 4 patterns according to a previously proposed classification. In addition, strain ratios of thyroid tissue to the nodule were calculated. Receiver operating characteristic curve analysis was used to compare the diagnostic performance of the strain ratio and that of conventional sonography. The final diagnosis was obtained from histologic findings.

RESULTS: When a cutoff point of 3.79 was introduced, significantly different strain ratios for benign (mean ± SD, 2.97 ± 4.35) and malignant (11.59 ± 10.32) lesions was obtained (P < .0001). The strain ratio measurement had 97.8% sensitivity and 85.7% specificity. The area under the curve for the strain ratio was 0.92, whereas that for the 4-point scoring system was 0.85. Of the conventional sonographic patterns, microcalcification had the highest area under the curve, at 0.72.

CONCLUSIONS: Strain ratio measurement of thyroid lesions is a fast standardized method for analyzing stiffness inside examined areas. Used as an additional tool with B-mode sonography, it helps increase the diagnostic performance of the examination.