Ultrasound vector flow imaging in carotid stenosis caused by atherosclerosis: techniques, applications, and perspectives

Atherosclerotic carotid artery stenosis is a major contributor to ischemic stroke. Conventional Doppler ultrasound is widely used for screening and grading, but diagnostic performance is constrained by angle dependence and limited capability to characterize complex, non-laminar flow or to derive hemodynamic metrics such as wall shear stress (WSS). This review summarizes current evidence on ultrasound vector flow imaging (VFI) in carotid atherosclerotic disease, focusing on key technical approaches and clinical applications. By estimating at least two in-plane velocity components, VFI provides angle-independent velocity vectors and multidirectional flow visualization, most commonly implemented using transverse oscillation or multi-angle plane-wave imaging. In vitro studies and small, single-center cohorts suggest that VFI-derived peak systolic velocity (PSV) agrees with angiographic or MR references and may be less error-prone than pulsed-wave Doppler in disturbed flow. VFI also enables estimation of wall shear stress (WSS) and flow-disturbance metrics (e.g., turbulence indices), which have been associated with stenosis severity and plaque features such as ulceration or intraplaque neovascularization. However, evidence remains largely cross-sectional and frequently two-dimensional, and measurements may be affected by vendor-specific processing, imaging depth, and signal dropout in heavily calcified or tortuous vessels. VFI is a promising noninvasive adjunct to carotid ultrasound that may extend hemodynamic assessment beyond conventional Doppler, particularly in complex anatomy. Prospective multicenter validation with standardized acquisition/reporting and quality control is needed to define reproducible thresholds and incremental clinical utility; the roles of three-dimensional VFI and AI-enabled automation remain to be established.