Impact of turbulence-induced asymmetric propagators on the accuracy of phase-contrast velocimetry

Al-Mubarak, H. F.I., Vallatos, A. and Holmes, W. M. (2021) Impact of turbulence-induced asymmetric propagators on the accuracy of phase-contrast velocimetry. Journal of Magnetic Resonance, 325, 106929. (doi: 10.1016/j.jmr.2021.106929) (PMID:33713991)

Abstract

Phase-contrast magnetic resonance velocimetry (PC-MRI) has been widely used to investigate flow properties in numerous systems. In a horizontal cylindrical pipe (3mm diameter), we investigated the accuracy of PC-MRI as the flow transitioned from laminar to turbulent flow (Reynolds number 352 to 2708). We focus primarily on velocimetry errors introduced by skewed intra-voxel displacement distributions, a consequence of PC-MRI theory assuming symmetric distributions. We demonstrated how rapid fluctuations in the velocity field, can produce broad asymmetric intravoxel displacement distributions near the wall. Depending on the shape of the distribution, this resulted in PC-MRI measurements under-estimating (positive skewness) or over-estimating (negative skewness) the true mean intravoxel velocity, which could have particular importance to clinical wall shear stress measurements. The magnitude of these velocity errors was shown to increase with the variance and decrease with the kurtosis of the intravoxel displacement distribution. These experimental results confirm our previous theoretical analysis, which gives a relationship for PC-MRI velocimetry errors, as a function of the higher moments of the intravoxel displacement distribution (skewness, variance, and kurtosis) and the experimental parameters q and Δ. This suggests that PC-MRI errors in such unsteady/turbulent flow conditions can potentially be reduced by employing lower q values or shorter observation times Δ.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Holmes, Dr William and Vallatos, Dr Antoine and Al-mubarak, Haitham Farooq Ibrahim
• Authors: Al-Mubarak, H. F.I., Vallatos, A., and Holmes, W. M.
• College/School: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Journal Name: Journal of Magnetic Resonance
• Publisher: Elsevier
• ISSN: 1090-7807
• ISSN (Online): 1096-0856
• Published Online: 04 February 2021
• Copyright Holders: Copyright © 2021 Elsevier Inc.
• First Published: First published in Journal of Magnetic Resonance 325: 106929
• Publisher Policy: Reproduced in accordance with the publisher copyright policy