Ultrasound imaging velocimetry: Toward reliable wall shear stress measurements

Ultrasound Imaging Velocimetry, or particle image velocimetry applied to ultrasound data, has received an increasing interest in recent years. In particular, it shows great promise to obtain non-invasive, in vivo hemodynamic information. Before the technique can be used in a clinical setting, the limitations and accuracy need to be addressed. In this study we validate the technique in vitro using contrast-enhanced imaging and demonstrate that data processing needs to be done with care to avoid biased measurements. In particular, bias toward integer displacements is much more prominent than in conventional particle image velocimetry. This is especially relevant for wall shear stress measurements, as velocities near the wall will be underestimated. A remedy is provided by using an alternative displacement estimator. Finally, preliminary results for the in vivo measurement in a rabbit abdominal aorta are presented.