Vector Flow Imaging for Carotid Artery Stenosis Assessment: A Scoping Review.

Background: Conventional Doppler ultrasound is limited by its angle dependence and its inability to characterize complex flow patterns adequately. Vector flow imaging (VFI) is an angle-independent ultrasound technique that enables two-dimensional velocity vector mapping and the assessment of hemodynamic parameters. This scoping review aims to map the current evidence on the application and validation of VFI for assessing carotid artery stenosis (CAS). Methods: Using the Population-Concept-Context framework, we included studies that evaluated the application, validity, or outcomes of vector flow imaging in individuals with suspected or confirmed carotid artery stenosis, as well as in healthy controls used for comparison or validation, in clinical or research settings. Five electronic databases were searched from inception through 30 April 2026. Studies limited to conventional Doppler ultrasound or to animal or phantom models without human validation were excluded. Data were synthesized using descriptive numerical analysis and narrative thematic synthesis. Results: A total of 48 sources of evidence met the inclusion criteria. Six trial registrations without reported results were excluded from synthesis, leaving 42 synthesized sources, including 40 original studies and two reviews. The most frequently reported parameters were wall shear stress (n = 25), turbulence indices (n = 11), and velocity vectors (n = 14). Most studies were cross-sectional (n = 20) or technical validation studies (n = 13) with small sample sizes (median 31 participants, IQR 10.5-57; range 1-476). The dominant research focus was plaque vulnerability assessment, while fewer studies addressed stenosis grading. Only eight studies reported diagnostic-performance metrics; none employed prespecified thresholds, two reported blinding, and none adhered to the Standards for Reporting Diagnostic Accuracy Studies guidelines (STARD). Conclusions: VFI enables detailed characterization of carotid hemodynamics, but the available evidence remains preliminary and does not establish clinical utility. Standardized, adequately powered studies with external validation are required before clinical implementation.