The role of multimodal ultrasonic flow imaging in Thyroid Imaging Reporting and Data System (TI-RADS) 4 nodules

Background: Color Doppler imaging (CDFI), contrast-enhanced ultrasound (CEUS), and superb microvascular imaging (SMI) are used to observe blood flow characteristics in Thyroid Imaging Reporting and Data System (TI-RADS) 4 nodules. The ability of these techniques to distinguish benign from malignant nodules was investigated. Methods: A total of 75 TI-RADS 4 nodules were examined using CDFI, SMI, and CEUS. The blood flow characteristics shown by the three methods were added to the current TI-RADS classification to establish a new TI-RADS classification. The value of the three methods and the diagnostic accuracy of the new and old TI-RADS classification were compared. Results: SMI better captured type II flow in benign nodules and type III flow in malignant nodules relative to CDFI. Malignant nodules detected with CEUS manifested mainly with hypo-enhancement, whereas benign nodules showed iso- and hyper-enhancement. The areas under the receiver operating characteristic (ROC) curves (AUC) obtained through the aforementioned flow distribution models were 0.690 (CDFI), 0.840 (SMI), 0.910 (CEUS), and 0.903 (CEUS and SMI combined mode), respectively. The diagnostic value of CEUS was the highest. Joint inspection using SMI with CEUS showed certain advantages in sensitivity, although the overall accuracy was equal to that of CEUS alone. Except for CDFI, the AUC of the new TI-RADS classification was significantly higher than that of the old one. Perforating vessels and low enhancement were independent predictors of thyroid carcinoma. Conclusions: Both SMI and CEUS visualized lower-velocity blood flow within TI-RADS 4 nodules. The new TI-RADS classification described here could improve diagnostic accuracy.