Role of ultrasound elastography in assessment of indeterminate thyroid nodules

Abstract

PurposeTo evaluate the role of ultrasound elastography as an additional technique in differentiating US indeterminate thyroid nodules in order to decrease the number of tissue biopsies. MethodsWe evaluated 30 patients with 36 indeterminate thyroid nodules based on US, criteria, by US elastography, using both the elastography score and strain ratio. Baseband US data were downloaded for off-line analysis. Elastographic maps (color coding) and thyroid stiffness index (strain ratio) were calculated for all nodules, with histopathological results being the standard reference. Receiver operating characteristic (ROC) curve analysis was used to determine the optimal cutoff strain ratio for separating benign and malignant thyroid nodules. ResultsMalignant nodules had a higher degree of color and strain ratio compared to benign nodules, with a statistically significant difference (p<0.05). Nodules with an elastography score of 2 were benign, while those with an elastography score of 4 and 5 were mostly malignant. Malignancy could not be excluded using ultrasound elastography criteria only, in nodules with a score of 3. The sensitivity and specificity of the US-elastography strain color coding for thyroid cancer diagnosis were 91% and 72% respectively. Using ROC analysis, the optimal cutoff strain ratio for separating benign and malignant thyroid nodules was found to be 1.6 with a calculated 89% sensitivity and 70% specificity. The overall accuracy of strain color was slightly better than strain ratio, 91% compared to 86% respectively. ConclusionUltrasound elastography is an easy, non-invasive and rapid technique that can be routinely used in thyroid US scans to select cases for FNAC, and decrease the number of unnecessary biopsies, and consequently decrease the hazards and costs. However, future advances in image acquisition and reconstruction algorithms are required to improve the image quality and clinical usefulness of this technique.