Blood flow velocity and wall shear stress estimation in forward-viewing intravascular ultrasound imaging: Comparison of Doppler and Particle Image Velocimetry (PIV) approaches

Locally elevated wall shear stress (WSS) has been linked with plaque rupture and erosion, which can then lead to major adverse cardiac events. We have previously demonstrated proof-of-concept for a catheter-based forward-viewing (FV) intravascular ultrasound (IVUS) imaging system capable of imaging 3D velocity fields, from which WSS could be derived. To determine which velocity estimation techniques can best estimate blood flow velocity and WSS in an FV IVUS scenario, in this work, we quantitively compared the performance of two ultrasound-based velocity estimation techniques, Doppler and Particle Image Velocimetry (PIV), with computational fluid dynamics (CFD) in coronary artery phantoms both without stenosis and with an eccentric 54% diameter stenosis (% DS). For the case without stenosis, PIV estimation produced a root mean square error (RMSE) greater than 11 ± 2.82% throughout the entire cross-section compared to Doppler. With stenosis, Doppler estimation yielded a 2 ± 0.3% greater RMSE compared to PIV. In both cases, PIV overestimated WSS by 14% in the case without stenosis, and by 48.59% with stenosis. While further investigation is required, preliminary results of the current study suggest that when imaged in an FV orientation, a Doppler approach has higher accuracy in estimating WSS relative to PIV.