Two-Dimensional Flow Imaging in the Carotid Bifurcation Using a Combined Speckle Tracking and Phase-Shift Estimator: A Study Based on Ultrasound Simulations and in vivo Analysis

A two-dimensional (2-D) blood velocity estimator is presented combining speckle tracking (ST) and phase-shift estimation (PE) to measure lateral (vx) and axial (vz) velocities respectively. Estimator properties were assessed in a carotid bifurcation using ultrasound simulations based on computational fluid dynamics, allowing validation toward a ground truth. Simulation results were supported with in vivo data of a healthy carotid. ST and PE estimates were combined as: (1) vx from 2D-ST and vz from PE, (2) vx from 2D-ST and vz from PE with aliasing correction based on ST and (3) vz from PE and only lateral ST for vx. Regression analysis showed a 35% to 77% decrease in standard deviation for vz for PE compared with ST. Aliasing correction based on ST improved results but also introduced spurious artifacts. A marginal decrease in performance was observed when only tracking laterally. Further work will focus on in vivo trials in patients with carotid plaques. (E-mail: abigail.swillens@ugent.be)