Local aortic stiffness prediction using a 1D flow model and Magnetic Resonance Imaging

, par  Dima

Mater/Engineering Intership
Duration : 4-6 months

Keywords : Fluid biomechanics, aortic flow modelling, aortic stiffness, Magnetic Resonance Imaging, central aortic pressure.

Location : Service Hospitalier Frédéric Joliot (SHFJ)

Context

Arterial stiffness emerges nowadays as a major risk factor of cardiovascular related mortality. In fact, changes in the mechanical properties of the arterial wall due to normal aging and/or vascular disease have become evident contributors to cardiovascular events. These structural and mechanical deteriorations cause
hypertension and induce a progressive increase of the left ventricle load, thus compromising the ventricular performance.
Global arterial stiffness associated with age can be assessed through some indexes measured during a routine medical exam. However, localized regional stiffnesses, such as those induced by early atherosclerosis, can only be assessed through simultaneous pressure and flow measurements at localized sites of the aorta. To this day no simple clinical exam can detect a localized aortic stiffening.

At the IR4M we have experimentally evaluated the effects of a local aortic stiffness on ventricular load and aortic hemodynamics using an aortic silicone phantom, Magnetic Resonance Imaging, and invasive pressure measurements [1]. On the other hand, we have developed a one-dimensional (1D) aortic flow model which estimates pressure waves along the aorta using MRI acquired flow wave as the inlet boundary condition and a Windkessel model as the exit boundary condition.
A variable compliance has then been introduced in the numerical model that would allow the simulation of a localized stiffness [2] and ultimately enable the prediction of the stiffness existence and localization through noninvasive imaging.
The stiffening model has not yet been fully validated against the experimental data, some improvements are necessary to better reflect the experimental reality.

Goals

The intern would have to revisit the stiffening numerical model and implement different compliance profiles to adapt the simulations to the experimental reality.
He/She should then propose an approach to predict the existence of a local stiffness, its position and length based on simulation outcomes.

Internship supervisor :

Dima AbiAbdallah Rodríguez

References

1. K. Rachid, D. Rodriguez, A phantom study to evaluate the effects of a local sectional stiffness on aortic hemodynamics, Biomedical Physic & Engineering Express, Vol.3, No. 6, P.065001, November 2017( DOI)
2. Khalil Rachid. Estimation de la pression aortique à l’aide de l’imagerie par résonance magnétique : développement d’un modèle biomécanique d’écoulement. Phd Thesis, Université Paris-Saclay, 2018.

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