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Measuring arterial pulsatility with dynamic inflow magnitude contrast

Whittaker, Joseph R., Fasano, Fabrizio, Venzi, Marcello, Liebig, Patrick, Gallichan, Daniel ORCID: https://orcid.org/0000-0002-0143-2855, Möller, Harald E. and Murphy, Kevin ORCID: https://orcid.org/0000-0002-6516-313X 2022. Measuring arterial pulsatility with dynamic inflow magnitude contrast. Frontiers in Neuroscience 15 , 795749. 10.3389/fnins.2021.795749

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Abstract

The pulsatility of blood flow through cerebral arteries is clinically important, as it is intrinsically associated with cerebrovascular health. In this study we outline a new MRI approach to measuring the real-time pulsatile flow in cerebral arteries, which is based on the inflow phenomenon associated with fast gradient-recalled-echo acquisitions. Unlike traditional phase-contrast techniques, this new method, which we dub dynamic inflow magnitude contrast (DIMAC), does not require velocity-encoding gradients as sensitivity to flow velocity is derived purely from the inflow effect. We achieved this using a highly accelerated single slice EPI acquisition with a very short TR (15 ms) and a 90° flip angle, thus maximizing inflow contrast. We simulate the spoiled GRE signal in the presence of large arteries and perform a sensitivity analysis. The sensitivity analysis demonstrates that in the regime of high inflow contrast, DIMAC shows much greater sensitivity to flow velocity over blood volume changes. We support this theoretical prediction with in-vivo data collected in two separate experiments designed to demonstrate the utility of the DIMAC signal contrast. We perform a hypercapnia challenge experiment in order to experimentally modulate arterial tone within subjects, and thus modulate the arterial pulsatile flow waveform. We also perform a thigh-cuff release challenge, designed to induce a transient drop in blood pressure, and demonstrate that the continuous DIMAC signal captures the complex transient change in the pulsatile and non-pulsatile components of flow. In summary, this study proposes a new role for a well-established source of MR image contrast and demonstrates its potential for measuring both steady-state and dynamic changes in arterial tone.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Physics and Astronomy
Additional Information: This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY
Publisher: Frontiers Media
ISSN: 1662-453X
Funders: Wellcome Trust
Date of First Compliant Deposit: 11 July 2022
Date of Acceptance: 22 December 2021
Last Modified: 30 Nov 2022 08:18
URI: https://orca.cardiff.ac.uk/id/eprint/151233

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