Maximal stiffness evaluation by real-time ultrasound elastography, an improved tool for the differential diagnosis of thyroid nodules

Objective: The aim of the study was to evaluate the diagnostic performance of a new ultrasound elastography (USE) parameter based on the measurement of the percentage of maximal stiffness within a nodule as compared with the already established elastographic strain index (SI) and to investigate their diagnostic performance according to nodule size. Methods: The study included 218 nodules. Each nodule underwent conventional ultrasound (US), USE evaluation, and fine-needle aspiration cytology (FNAC). Thyroid nodules were further stratified into 4 subgroups (G) according to their size (G1, <1 cm; G2, 1-2 cm; G3, >3 cm). USE evaluation comprised the measurement of the percentage of the areas included in the region of interest corresponding to the maximal stiffness (% Index) and of the SI. Results: The % Index and of the SI were significantly higher in malignant than in benign thyroid nodules, and both measurements displayed a good diagnostic performance (SI sensitivity and specificity, 0.66 and 0.90, respectively; % Index sensitivity and specificity, 0.76 and 0.89, respectively). Compared with SI, the % Index was more informative, both in the whole group of thyroid nodules (odds ratio [OR], 18.68; 95% confidence interval [CI], 6.06 to 63.49; P<.0001 versus OR, 26.15; 95% CI, 8.01 to 102.87; P<.0001, respectively) and in the G1 and G2 subgroups. Conclusion: The % Index is a stronger predictor of nodule malignancy than both the SI and the conventional US signs. This is particularly true in nodules smaller than 1 cm, which are more difficult to explore both by conventional US and FNAC.