Efficacy of Differential Diagnosis of Thyroid Nodules by Shear Wave Elastography, the Stiffness Map

Background: Fine-needle aspiration (FNA) is the first step in the differential diagnosis of thyroid nodules. However, malignancy rate of the indeterminate FNA is reported as 20-50 %. We aimed to evaluate the efficacy of shear wave elastography (SWE), the map of stiffness in the differential diagnosis of the histopathology of thyroid nodules. Methods: We retrospectively reviewed the medical records of 258 consecutive patients who visited the thyroid clinic for thyroid nodules and who underwent SWE before ultrasound-guided FNA and/or core-needle biopsy. We analyzed the EI using the total nodular region of interest method by the Q-Box Trace program. Thyroid nodules were divided in to 4 categoies according to maximum elasticity (E(Max)) and nodule depth/width (D/W) ratio; Category 1 (E(Max) ≥42.6 kPa & D/W<0.9), Category 2 (E(Max) <42.6 kPa & D/W<0.9), Category 3 (E(Max) ≥42.6 kPa & D/W≥ 0.9) and Category 4 (E(Max)<46.2 kPa & D/W≥ 0.9). The cutoff value of E(Max) was set using ROC curve analysis to predict follicular neoplasm (FN) from nodular hyperplasia (NH). Cutoff value ​​for nodule D/W ratio was set using ROC curve analysis to differentiate malignant nodule. Results: FN showed the lowest E(Max) among all pathologies and lower E(Max) than NH (p<0.05). FN was distributed mostly in the category 2 (70%) and NH was distributed mainly in the category 1 (73.9%). CLT belonged mostly to the category 1 (57.1%). PTC belonged in majority to the category 3 (58.9%) and the rest.to the category 1 (25%). So NH was the most frequent pathology group in category 1.FN was the most frequent pathology group in the category 2 and PTC was the most frequent pathology group in the category 3. Conclusion: SWE showed characteristic patterns of various pathology groups reflecting the degree of fibrosis and the information of E(Max) and nodule depth/width (D/W) ratio determining the category was useful to predict the pathology of thyroid nodules along with the advantage of noninvasiveness.