Two-dimensional flow velocity estimation in the carotid bifurcation: a study of crossed-beam vector Doppler and speckle tracking using computational fluid dynamics

Detailed imaging of complex blood flow may improve early diagnosis of cardiovascular disease. Searching for multi-dimensional velocity estimators, research has given attention to speckle tracking (ST) and vector Doppler (VD). However, these techniques have yet to be validated for complex flow as may arise in diseased arteries. In this work, the properties of ST and crossed-beam VD are compared with a ground truth for clinically relevant flow using an ultrasonic simulation model (Field II) coupled with the output from computational fluid dynamics (CFD). Using this CFD-based ultrasound simulation environment, ST and crossed-beam VD will be evaluated for pulsatile flow in a 3D stenosed carotid bifurcation. Both methods had overall a good agreement with the CFD reference, however VD suffered from more spurious artifacts and was more hampered by aliasing throughout the cardiac cycle. ST was less accurate in estimating the axial component, but prevailed in estimating velocities well beyond the Nyquist range. Based on our simulations, both methods may be used to image complex flow in the carotid bifurcation. However, considering also scanning limitations of VD, ST may provide a more consistent and practical approach.