A semi-automated method for measuring the evolution of both lumen area and blood flow in carotid from Phase Contrast MRI

Fasquel, Jean-Baptiste; Lécluse, Aldéric; Cavaro‐Ménard, Christine; Willoteaux, S.

doi:10.1016/j.compbiomed.2015.09.017

Cited by 3 publications

(1 citation statement)

References 22 publications

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“…The ability of PFG velocimetry to non-invasively map flow fields in opaque systems has since found an extraordinary range of applications. It is extensively used in clinical practice to image cardio-vascular flows [3,4], pulmonary gas flow [5] and even spinal fluid flow [6]. Applications in the physical sciences have ranged from studies of vortical flow [7] and turbulence [8] to falling droplets [9] and granular flows [10].…”

Section: Introductionmentioning

confidence: 99%

Accuracy of phase-contrast velocimetry in systems with skewed intravoxel velocity distributions

Vallatos

Al-Mubarak

Mullin

et al. 2018

Journal of Magnetic Resonance

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Phase contrast velocimetry (PCV) has been widely used to investigate flow properties in numerous systems. Several authors have reported errors in velocity measurements and have speculated on the sources, which have ranged from eddy current effects to acceleration artefacts. An often overlooked assumption in the theory of PCV, which may not be met in complex or unsteady flows, is that the intravoxel displacement distributions (propagators) are symmetric. Here, the effect of the higher moments of the displacement distribution (variance, skewness and kurtosis) on the accuracy of PCV is investigated experimentally and theoretically. Phase and propagator measurements are performed on tailored intravoxel distributions, achieved using a simple phantom combined with a single large voxel. Asymmetric distributions (Skewness ≠ 0) are shown to generate important phase measurement errors that lead to significant velocimetry errors. Simulations of the phase of the spin vector sum, based on experimentally measured propagators, are shown to quantitatively reproduce the relationship between measured phase and experimental parameters. These allow relating the observed velocimetry errors to a discrepancy between the average phase of intravoxel spins considered in PCV theory and the vector phase actually measured by a PFG experiment. A theoretical expression is derived for PCV velocimetry errors as a function of the moments of the displacement distribution. Positively skewed distributions result in an underestimation of the true mean velocity, while negatively skewed distributions result in an overestimation. The magnitude of these errors is shown to increase with the variance and decrease with the kurtosis of the intravoxel displacement distribution.

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