Wall shear stress mapping for human femoral artery based on ultrafast ultrasound vector Doppler estimations

Purpose: Wall shear stress (WSS), a type of friction exerted on the artery wall by flowing blood, is considered a crucial factor in atherosclerotic plaque development. Currently, achieving a reliable WSS mapping of an artery noninvasively by using existing imaging modalities is still challenging. In this study, a WSS mapping based on vector Doppler flow velocity estimation was proposed to measure the dynamic WSS on the human femoral artery. Methods: Because ultrafast ultrasound imaging was used here, flow-enhanced imaging was also performed to observe the moving blood flow condition. The performance of WSS mapping was verified using both straight (8 mm in diameter) and stenosis (70% of stenosis) phantoms under a pulsatile flow condition. A human study was conducted from five healthy volunteers. Results: Experimental results demonstrated that the WSS estimation was close to the standard value that was obtained from maximum velocity estimation in straight phantom experiments. In a stenosis phantom experiment, a low WSS region was observed at a site downstream of an obstruction, which is a high-risk area for plaque formation. Dynamic WSS mapping was accomplished in measurement in the femoral artery bifurcation. In measurements, the time-averaged WSS of the common femoral artery, superficial femoral artery, and deep femoral artery was 0.52± 0.19, 0.44 ± 0.21, and 0.29 ± 0.16 Pa, respectively, for the anterior wall and 0.29 ± 0.11, 0.54 ± 0.24, and 0.23 ± 0.10 Pa, respectively, for the posterior wall. Conclusions: All results indicated that WSS mapping has the potential to be a useful tool for vessel duplex scanning in the future.