Value of Quantitative Contrast-Enhanced Ultrasonography in Distinguishing Asymptomatic Subacute Thyroiditis from Papillary Thyroid Carcinoma

Background: Asymptomatic subacute thyroiditis (aSAT) without inflammatory features is often difficult to distinguish from papillary thyroid carcinoma (PTC), even with ultrasonography. Under certain circumstances, a fine-needle aspiration biopsy (FNAB) is performed, which is known to increase the patient's physical pain. Objectives: To investigate the value of quantitative contrast-enhanced ultrasonography (CEUS) in discriminating aSAT from PTC Patients and Methods: A total of 30 aSAT and 23 PTC patients were systematically reviewed. Quantitative CEUS parameters, including the rise time (RT), time to peak (TTP), maximum intensity (IMAX), as well as their extension indicators (ART and ATTP), were determined in various nodule areas (total, central, peripheral, and control regions of nodules). Chi-square test and independentsamples t-test were performed to compare significant differences between PTC and aSAT. A receiver operating characteristics (ROC) curve analysis was also performed to assess the diagnostic efficacy of each parameter, as well as diagnostic efficacy indices, including sensitivity and specificity, in discriminating aSAT from PTC nodules. Results: Compared to the PTC group, patients with aSAT had a longer ART1 (RT of the control area - RT of the whole area; 0.12 +/- 0.69 vs. -0.2 +/- 0.57, P = 0.03) and ART3 (RT of the control area - RT of the central area; 0.43 +/- 0.72 vs. 0.04 +/- 0.94, P = 0.049). Besides, compared to the PTC group, the aSAT group had a shorter RT in the total area (RT1: 4.05 +/- 1.56 vs. 4.91 +/- 2.09, P = 0.045); a shorter TTP in the total (TTP1: 4.91 +/- 1.76 vs. 7.30 +/- 3.92, P = 0.005), peripheral (TTP2: 5.06 +/- 1.97 vs. 7.00 +/- 3.48, P = 0.01), and central (TTP3: 4.90 +/- 1.68 vs. 7.57 +/- 4.41, P = 0.004) areas; and a lower IMAX in the peripheral area (IMAX2: 0.74 +/- 0.36 vs. 1.09 +/- 0.57, P = 0.009). Based on the ROC curve analysis, the area under the curve was significantly larger for TTP1 as compared to RT1 (P = 0.027). Conclusion: Conventional ultrasound and CEUS examinations were inadequate in distinguishing PTC from aSAT. Overall, a quantitative analysis may indicate more biological characteristics of nodules, which can be helpful in the differential diagnosis.