title: Vector projectile imaging: time-resolved dynamic visualization of complex flow patterns.
abstract: Achieving non-invasive, accurate and time-resolved imaging of vascular flow with spatiotemporal fluctuations is well acknowledged to be an ongoing challenge. In this article, we present a new ultrasound-based framework called vector projectile imaging (VPI) that can dynamically render complex flow patterns over an imaging view at millisecond time resolution. VPI is founded on three principles: (i) high-frame-rate broad-view data acquisition (based on steered plane wave firings); (ii) flow vector estimation derived from multi-angle Doppler analysis (coupled with data regularization and least-squares fitting); (iii) dynamic visualization of color-encoded vector projectiles (with flow speckles displayed as adjunct). Calibration results indicated that by using three transmit angles and three receive angles (-10°, 0°, +10° for both), VPI can consistently compute flow vectors in a multi-vessel phantom with three tubes positioned at different depths (1.5, 4, 6 cm), oriented at different angles (-10°, 0°, +10°) and of different sizes (dilated diameter: 2.2, 4.4 and 6.3 mm; steady flow rate: 2.5 mL/s). The practical merit of VPI was further illustrated through an anthropomorphic flow phantom investigation that considered both healthy and stenosed carotid bifurcation geometries. For the healthy bifurcation with 1.2-Hz carotid flow pulses, VPI was able to render multi-directional and spatiotemporally varying flow patterns (using a nominal frame rate of 416 fps or 2.4-ms time resolution). In the case of stenosed bifurcations (50% eccentric narrowing), VPI enabled dynamic visualization of flow jet and recirculation zones. These findings suggest that VPI holds promise as a new tool for complex flow analysis.
authors: Medical Engineering Program, University of Hong Kong, Pokfulam, Hong Kong.
authors: Billy Y S
authors: BY
authors: Yiu
authors: Medical Engineering Program, University of Hong Kong, Pokfulam, Hong Kong.
authors: Simon S M
authors: SS
authors: Lai
authors: Medical Engineering Program, University of Hong Kong, Pokfulam, Hong Kong. Electronic address: alfred.yu@hku.hk.
authors: Alfred C H
authors: AC
authors: Yu
mesh_terms: D000465:Algorithms; D001783:Blood Flow Velocity; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D016018:Least-Squares Analysis; D019047:Phantoms, Imaging; D012212:Rheology / Q000379:methods*; D018608:Ultrasonography, Doppler / Q000379:methods*
keywords: Complex flow analysis; Dynamic visualization; Ultrasound flow imaging; Vector estimation; Vector projectile