Effects of Morphological Variations on Hemodynamic Parameters in the Middle Cerebral Artery: A study conducted through Computational Fluid Dynamics

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Malmsköld, Pontus
Odbratt, Johanna
Peyvandi, Ehsan
Åkesson, Louise
Stroke is a large contributor to deaths around the world. One common cause of stroke is an Intracranial Aneurysm, which causes the wall of the artery to expand and potentially rupture leading to hemorrhage in the brain. The formation and rupture of both aneurysms as well as other contributors to stroke, are tied to specific hemodynamic properties such as wall shear stress. This paper aims to investigate the differences in wall shear stress in different patients in a bifurcating part of the cerebral vascular system that is prone to developing stroke; the middle cerebral artery. This in order to see how morphological differences between patients affect the hemodynamic parameters such as wall shear stress. This was done using an in silico method within Computational fluid dynamics called the Lattice Boltzmann method for two different patients. The Herschel Bulkley model was used in order to properly model the non-Newtonian flow of blood. The data for the two patients were provided though open-source MRI scans where the vascular system was extracted through thresholding. The results of simulating the flow for both patients showed that the mean shear rate is quite similar for the two patients, with some significant differences in local shear rate. These differences were attributed to the bifurcation angles of the arteries, where the patient with the largest bifurcation angle had the highest local shear rate both in and after the bifurcation. A higher shear rate implies a higher wall shear stress, which resulted in the fact that a larger bifurcation angle seems to give rise to a higher wall shear stress. Hence, the risk of developing Intracranial Aneurysms and other conditions leading to stroke in the middle cerebral artery, seems to be higher when the bifurcation angle is large.
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