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Approximating oxygen transport in human carotid bifurcations with near-wall hemodynamic descriptors

Tanya Pagnotta

Approximating oxygen transport in human carotid bifurcations with near-wall hemodynamic descriptors.

Rel. Umberto Morbiducci, Diego Gallo, Giuseppe De Nisco, Valentina Mazzi. Politecnico di Torino, Corso di laurea magistrale in Ingegneria Biomedica, 2022


Atherosclerosis is the major cause of death and disability in developed countries. It is a progressive disease affecting main arteries due to a chronic inflammation of the tunica intima, with the formation of an atherosclerotic plaque. If the plaque protrudes into the vessel lumen, narrowing the artery, it may impede blood from flowing to downstream organs and tissues. The atherosclerotic disease results from a complex interplay of systemic, biological, and biomechanical factors. Among the latter, local hemodynamics, and, in particular, wall shear stress (WSS) magnitude and topology contribute to the initiation/progression of the disease. Additionally, mass transport in arteries also plays a key role in vascular diseases. Several studies have indeed revealed an association between endothelial inadequate oxygen supply (hypoxia) and lesion development sites. Those luminal regions are usually exposed to near-wall flow disturbances, such as flow stagnation, separation, recirculation. For this reason, over the years, several biomechanical descriptors have been proposed as markers of disturbed flow regions, and image-based computational fluid dynamics (CFD) has been adopted to investigate the links among disturbed flow, atherogenesis and arterial mass transport. Furthermore, very recently, a growing interest has emerged on the topological skeleton of WSS vector field due to its ability to provide a template of blood-wall mass transfer. In this scenario, here we test the capability of widely adopted hemodynamic descriptors of WSS magnitude and multidirectionality, and of Eulerian-based features of WSS topological skeleton, to properly describe near-wall oxygen transfer, overcoming the high computational costs currently limiting mass transfer modelling. In detail, starting from a larger dataset, two subject-specific computational models of carotid bifurcation were selected based on the amount of flow disturbances. The geometries were meshed to properly model near-wall oxygen transport/transfer, and personalized boundary conditions were prescribed to perform unsteady-state computational fluid dynamics simulations. Near-wall hemodynamics was characterized in terms of the three canonical WSS-based descriptors of disturbed flow (i.e., TAWSS, OSI, and RRT), and the WSS topological skeleton features (normalized WSS divergence); while the oxygen flux at the arterial wall was estimated based on the Sherwood number (Sh). Besides the appreciable co-localization between each of the WSS-based descriptors of disturbed flow and hypoxic condition at the vascular wall (identified by low Sh), a co-occurrence of luminal exposure to negative normalized WSS divergence and low Sh values clearly emerged. Findings from this study testify the capability of Eulerian-based WSS topological skeleton to provide an effective template of near-wall oxygen transport/transfer, with a significative reduction of both the computational costs and the complexity associated to classical techniques.

Relators: Umberto Morbiducci, Diego Gallo, Giuseppe De Nisco, Valentina Mazzi
Academic year: 2021/22
Publication type: Electronic
Number of Pages: 80
Additional Information: Tesi secretata. Fulltext non presente
Corso di laurea: Corso di laurea magistrale in Ingegneria Biomedica
Classe di laurea: New organization > Master science > LM-21 - BIOMEDICAL ENGINEERING
Aziende collaboratrici: UNSPECIFIED
URI: http://webthesis.biblio.polito.it/id/eprint/23760
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