A Prospective Study to Compare Superb Microvascular Imaging with Grayscale Ultrasound and Color Doppler Flow Imaging of Vascular Distribution and Morphology in Thyroid Nodules

Background: This study aimed to compare superb microvascular imaging (SMI) with grayscale ultrasound (US) and color Doppler flow imaging (CDFI) to evaluate vascular distribution and morphology to distinguish between benign and malignant thyroid nodules. Material/Methods: Seventy-one patients with 76 thyroid nodules underwent grayscale US, CDFI, and SMI thyroid imaging. CDFI and SMI assessed vascular quantity, morphology, and distribution, and was graded according to Adler's method, as absent (grade 0), minimal (grade 1), moderate (grade 2), or marked (grade 3). The detection of malignancy was compared between the following imaging groups, grayscale US alone, US combined with CDFI, and US combined with SMI. Results: SMI was significantly more accurate in identifying malignant thyroid nodules (79.3%) compared with CDFI (55.2%) (P<0.001). In malignant thyroid nodules, penetrating blood vessels were identified by SMI in 62.1% and by CDFI in 41.4%; there was no significant difference in vascular distribution between SMI (P=0.835) and CDFI (P=0.806). Grayscale US with SMI resulted in the greatest diagnostic sensitivity, accuracy, and specificity (86.21%, 85.53%, and 85.11%) compared with grayscale US with CDFI (75.86%, 82.89%, and 87.23%). Receiver operating characteristic (ROC) area under the curve (AUC) values of US with SMI, US with CDFI, and US alone were 0.918 (95% CI, 0.856-0.979), 0.911 (95% CI, 0.849-0.973), and 0.847 (95% CI, 0.762-0.932), respectively (P<0.001). Conclusions: SMI as an adjunct to grayscale US provided significantly more information on vascularity associated with malignancy in thyroid nodules, when compared with grayscale US or with US and CDFI.