Added Value of the Vascular Index on Superb Microvascular Imaging for the Evaluation of Breast Masses

OBJECTIVES: To evaluate the value of the vascular index (VI) on Superb Microvascular Imaging (SMI; Canon Medical Systems Corporation, Tokyo, Japan) in comparison with grayscale ultrasound (US) alone for assessing breast masses. METHODS: We evaluated a total of 70 breast masses (36 malignant and 34 benign lesions) in 70 consecutive patients using grayscale US and SMI. Two breast radiologists analyzed grayscale US alone and the combination of grayscale US and SMI. They also measured the VI based on SMI. The diagnostic performance of grayscale US alone and the combination of grayscale US and SMI was compared. The VI was compared between benign and malignant masses, and the optimal cutoff value was determined. In addition, the interobserver agreement in imaging analyses and the VI was assessed. RESULTS: The interobserver agreements in imaging analyses and the VI were almost perfect. The VI of malignant breast masses was significantly higher than that of benign lesions (P < .001). The optimal cutoff value of the VI for differentiating between malignant and benign breast masses was 2.95, with sensitivity of 86.1% and specificity of 91.2%. The diagnostic performance values of grayscale US alone and the combination of grayscale US and SMI were 0.824 and 0.912, respectively, for reader 1 (P = .028) and 0.795 and 0.853 for reader 2 (P = .101). CONCLUSIONS: The VI on SMI was significantly higher for malignant breast masses than for benign lesions, with high interobserver agreement. Our study suggests that the combination of grayscale US and SMI with the VI could improve the characterization of breast masses.