Robust angle-independent blood velocity estimation based on multi-angle speckle tracking and vector Doppler

Two-dimensional blood velocity estimation has shown potential to solve the angle-dependency of conventional ultrasound flow imaging. Clutter filtering, however, remains a major challenge for large beam-to-flow angles, leading to signal drop-outs and corrupted velocity estimates. This work presents and evaluates a compounding speckle tracking (ST) algorithm to obtain robust angle-independent two dimensional blood velocity estimates. A dual-angle plane wave imaging setup with full parallel receive beamforming is utilized to achieve high-frame-rate speckle tracking estimates from two scan angles, which may be compounded to obtain velocity estimates of increased robustness. The acquisition also allows direct comparison to vector Doppler (VD) imaging. The method was tested in vivo for vascular and neonatal cardiac imaging. In a carotid artery bifurcation the obtained blood velocity estimates showed that the compounded ST method was less influenced by clutter filtering than conventional ST and VD methods. In the cardiac case, a more consistent blood flow depiction was obtained using the compounded ST method compared with conventional ST. However, the ST methods were more affected by low signal-to-noise ratio than YD.