Abstract TP201: Carotid Artery Flow as Determined by Real-Time Phase-Contrast Flow Mri and Neurovascular Ultrasound: a Comparative Study of Healthy Subjects

Abstract

Background: The assessment of carotid artery flow by neurovascular ultrasound (nvUS) may be complemented by real-time phase-contrast (RT-PC) flow MRI which apart from quantitative flow parameters offers velocity distributions across the entire vessel lumen. Methods: The feasibility and diagnostic potential of RT-PC flow MRI was evaluated in 20 healthy volunteers in comparison to conventional nvUS. RT-PC flow MRI at 40 ms temporal resolution and 0.8 mm in-plane resolution resulted in velocity maps with low phase noise and high spatiotemporal accuracy by exploiting respective advances of a recent nonlinear inverse model-based reconstruction. Peak-systolic velocities (PSV), end-diastolic velocities (EDV), flow volumes and comprehensive velocity profiles were determined in the common, internal and external carotid artery on both sides. Results: Characteristics in pulsatility and laminar flow, including individual flow abnormalities shown on nvUS, could be reproduced and visualized in detail by RT-PC flow MRI. Fig. 1 shows a representative color-coded duplex sonography with doppler spectrum (A), flow volume measurement by RT-PC flow MRI (B) and a three-dimensional representation of through-plane velocities at peak systole (C) and end diastole (D) in the internal carotid artery. PSV to EDV differences revealed good agreement between both techniques, mean PSV and EDV were significantly lower and flow volumes were higher for MRI. Conclusions: Our findings suggest that RT-PC flow MRI may add to clinical diagnostics, e.g. by alterations of dynamic velocity distributions in patients with carotid stenosis. Lower PSV and EDV values than for nvUS mainly reflect the longer MRI acquisition time which attenuates short peak velocities, while higher flow volumes benefit from a proper assessment of the true vessel lumen.