New microvascular ultrasound techniques: abdominal applications

Abstract

Microvascular ultrasound (MVUS) is a new ultrasound technique that allows the detection of slow-velocity flow, providing the visualization of the blood flow in small vessels without the need of intravenous contrast agent administration. This technology has been integrated in the most recent ultrasound equipment and applied for the assessment of vascularization. Compared to conventional color Doppler and power Doppler imaging, MVUS provides higher capability to detect intralesional flow. A growing number of studies explored the potential applications in hepatobiliary, genitourinary, and vascular pathologies. Different flow patterns can be observed in hepatic and renal focal lesions providing information on tumor vascularity and improving the differential diagnosis. This article aims to provide a detailed review on the current evidences and applications of MVUS in abdominal imaging.

Keywords: Contrast-enhanced ultrasound; Micro-flow imaging; Microvascular flow imaging; Superb microvascular imaging.

Fig. 1

40-year-old woman with a 5.7 cm hepatic hemangioma incidentally detected on abdominal ultrasound examination. Color (a) and directional power Doppler (b) imaging demonstrate minimal peripheral vascularization. Microvascular flow imaging shows a strip rim pattern of vascularization (c). Contrast-enhanced ultrasound (CEUS) confirmed the diagnosis of hepatic hemangioma by showing the peripheral globular enhancement (d, 63 s after contrast injection)

Fig. 2

78-year-old man with hepatocellular carcinoma. B-mode ultrasound (a) shows a 2.0 cm hypoechoic lesion in the right hepatic lobe (arrow). Color (b) and power Doppler (c) imaging demonstrate mild peripheral vascularization. Microvascular imaging clearly depicts both peripheral and irregular intratumoral vascular pattern (d)

Fig. 3

49-year-old woman with incidentally detected 1.2 cm gallbladder polyp. Color (a), directional power Doppler (b), and microvascular flow imaging (c) demonstrate intralesional vascular signal, with branching appearance on MVUS (arrow). The lesion shows homogeneous enhancement on contrast-enhanced ultrasound at 32 s after contrast injection (d). This lesion was confirmed as an adenomatous polyp after cholecystectomy

Fig. 4

56-year-old man with 5 cm cystic renal lesion detected on computed tomography. Color (a), directional power doppler (b), and microvascular flow imaging (c) do not detect any intracystic vascularization. Contrast-enhanced ultrasound (d) shows septa with minimal enhancement at 58 s after contrast injection. The lesion was classified as bosniak IIF

Fig. 5

64-year-old man with bladder cancer. Ultrasound examination with microvascular flow imaging (a) shows a 2.3 cm lesion of the bladder wall with intralesional vascularization (arrow). The lesion demonstrates strong enhancement on contrast-enhanced ultrasound at 50 s after contrast injection (b, arrow)

Fig. 6

76-year-old man undergoing follow-up examination after endovascular aneurysm repair. Ultrasound examination with color doppler imaging (a) shows patency of the graft without signs of endoleak. Microvascular flow imaging (b) demonstrates the presence of a peripherally located endoleak (arrow), consistent with type II endoleak from a lumbar artery, which was confirmed on contrast-enhanced ultrasound (c, arrow, at 96 s after contrast injection)