VFI in Healthy Vessels

There is a wealth of evidence implicating the important role of blood flow throughout all stages of the process of atherogenesis. Two locations along the vascular tree at which atherosclerotic plaques are typically found are the carotid artery (CA) and the superficial femoral artery (SFA). Nowadays, ultrasound is the technique of choice for assessing the vascular condition in the CA and SFA. However, clinically used ultrasound techniques show a large variability in estimating the blood flow velocity, due to multiple limitations. With the advent of ultrafast ultrasound imaging, (almost) all elements of the transducer can be activated simultaneously. These so-called plane wave acquisition acquires thousands of images per second and makes continuous tracking of blood flow velocities in all directions in the field of view possible. This high-frame-rate acquisition opened up new possibilities for blood flow imaging at the CA and SFA, such as blood Speckle Tracking (bST) and ultrasound Particle Image Velocimetry (echoPIV). Both these vector flow imaging (VFI) techniques enable the quantification of 2D blood flow velocity profiles, where bST uses no contrast agents compared to echoPIV. Beside these novel ultrasound based techniques, 4D Phase Contrast Magnetic Resonance Imaging (4D flow MRI) enables a non-invasive quantification of the 4D blood flow velocity profiles (3D + time) and can be used as reference standard for blood flow assessments in-vivo. We therefore aim to evaluate the performance of both VFI techniques in comparison to 4D flow MRI measurements in the CA and SFA of healthy volunteers.