Value of time-intensity curve analysis of contrast-enhanced ultrasound in the differential diagnosis of thyroid nodules

Objective To assess the feasibility of time-intensity curve (TIC) analysis of contrast-enhanced ultrasound (CEUS) in demonstrating features of benign and malignant thyroid nodules. Methods CEUS images of 98 patients with 103 thyroid nodules were retrospectively analyzed. The final diagnosis was confirmed by histology after surgical excision, or cytology after fine needle aspiration (FNA). Among the benign nodules, which were confirmed using cytology and not surgically removed, those with a >50% cystic component that showed no changes for 1 year on follow-up US, were diagnosed as clinically benign nodules. Similarly, nodules with a <50% cystic component that were aspirated twice and showed no changes for 1 year on follow-up US were also regarded as clinically benign nodules. TIC parameters, including perfusion parameters of relative values (RV) of peak intensity (PI) (△PI), RV of rise time (△RT), RV of time to peak (△TTP), RV of maximum slope coefficient (MSC) of wash-in (△MSCWI), RV of area under the rising curve (△AUCR), clearance parameters of RV of area under the falling curve (△AUCF), RV of MSC of washout (△MSCWO), comprehensive parameters of RV of mean transit time (△MTT), and area under the falling curve (△AUCF) were observed. Results Compared with benign thyroid nodules, malignant nodules on TIC analysis of CEUS showed a lower △PI (119.73 (115.34, 129.7), −15.82 (−17.7, -4.31)), later △RT (−0.27 (−0.51, −0.2), 0.58 (−0.26, 0.65)) and △TTP (−0.52 (−0.55, −0.36), 0.69 (−0.04, 0.74)), gentler △MSCWI (6.18 (5.29, 7.44), −6.1 (−7.6, 2.14)), and smaller △AUCR (75.7 (56.95, 93.22), −88.43 (−108.89, −73.21)) in perfusion parameters; a smaller △AUCF (112.92 (87.77, 137.58), −75.55 (−105.28, −59.32)) in clearance parameters; and a smaller △AUC (181.7 (151.50, 219.06), −160.64 (−200.08, −144.11)), and an earlier △MTT (2.00 (1.85, 3.14), −2.09 (−2.48, −0.95)) in comprehensive parameters (P < 0.05). Multivariate analysis of RV of TIC parameters demonstrated that △MSCWI (OR = 0.112; 95% confidence interval [CI], 0.025–0.507) and △MTT (OR = 0.099; 95% CI, 0.028–0.346) were protective factors. Conclusions TIC of CEUS is a very promising and valuable technique for differentiating benign and malignant thyroid nodules.