A combined speckle tracking and phase-shift estimation approach for 2D blood flow imaging in the carotid bifurcation

A 2D blood velocity estimator is presented combining speckle tracking (ST) and phase-shift estimation (PE) to measure lateral (v_x) and axial (v_z) velocities respectively. Estimator properties were assessed in a computer model of a carotid bifurcation using ultrasound simulations based on computational fluid dynamics, allowing validation towards a ground truth. Simulation results were supported with in-vivo data of a healthy carotid. ST and PE estimates were combined as: 1) v_x from 2D-ST and v_z from PE, 2) v_x from 2D-ST and v_z from PE with aliasing correction based on ST, 3) v_z from PE and only lateral ST for v_x. Regression analysis showed a 35-77 % decrease in standard deviation for v_z for PE compared to ST. Aliasing correction based on ST improved results but also introduced spurious artifacts. A marginal decrease in performance was observed when only tracking laterally.