A Novel Microvascular Flow Technique: Initial Results in Thyroids

To evaluate the flow imaging capabilities of a new prototype ultrasound (US) image processing technique (superb micro-vascular imaging [SMI]; Toshiba Medical Systems, Tokyo, Japan) for depiction of microvascular flow in normal thyroid tissue and thyroid nodules compared with standard color and power Doppler US imaging.Ten healthy volunteers and 22 patients, with a total of 25 thyroid nodules, scheduled for US-guided fine needle aspiration were enrolled in this prospective study. Subjects underwent US examination consisting of grayscale, color and power Doppler imaging (CDI and PDI) followed by color and monochrome SMI and pulsed Doppler. SMI is a novel, microvascular flow imaging mode implemented on the Aplio 500 US system (Toshiba). SMI uses advanced clutter suppression to extract flow signals from large to small vessels and depicts this information at high frame rates as a color overlay image or as a monochrome map of flow. Two radiologists independently scored still images and digital clips for overall flow detection, vessel branching details and noise on a visual-analog scale of 1 (worst) to 10 (best).For the volunteers SMI visualized microvasculature with significantly lower velocity than CDI and PDI (P < 0.012). In all thyroid nodules, SMI demonstrated microvascular flow with significantly higher image scores and provided better depiction of the vessel branching details compared with CDI and PDI (P < 0.0001). Clutter noise was significantly higher in monochrome SMI mode than in the other modes, including color SMI (P < 0.001).The novel SMI mode consistently improved the depiction of thyroid microvascular flow compared with standard CDI and PDI.