title: MRI-based quantification of outflow boundary conditions for computational fluid dynamics of stenosed human carotid arteries.
abstract: Accurate assessment of wall shear stress (WSS) is vital for studies on the pathogenesis of atherosclerosis. WSS distributions can be obtained by computational fluid dynamics (CFD) using patient-specific geometries and flow measurements. If patient-specific flow measurements are unavailable, in- and outflow have to be estimated, for instance by using Murray's Law. It is currently unknown to what extent this law holds for carotid bifurcations, especially in cases where stenoses are involved. We performed flow measurements in the carotid bifurcation using phase-contrast MRI in patients with varying degrees of stenosis. An empirical relation between outflow and degree of area stenosis was determined and the outflow measurements were compared to estimations based on Murray's Law. Furthermore, the influence of outflow conditions on the WSS distribution was studied. For bifurcations with an area stenosis smaller than 65%, the outflow ratio of the internal carotid artery (ICA) to the common carotid artery (CCA) was 0.62+/-0.12 while the outflow ratio of the external carotid artery (ECA) was 0.35+/-0.13. If the area stenosis was larger than 65%, the flow to the ICA decreased linearly to zero at 100% area stenosis. The empirical relation fitted the flow data well (R(2)=0.69), whereas Murray's Law overestimated the flow to the ICA substantially for larger stenosis, resulting in an overestimation of the WSS. If patient-specific flow measurements of the carotid bifurcation are unavailable, estimation of the outflow ratio by the presented empirical relation will result in a good approximation of calculated WSS using CFD.
authors.affiliation: Biomechanics Laboratory, Biomedical Engineering, EE2322, Erasmus MC, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: Harald C
authors.initials: HC
authors.lastname: Groen
authors.forename: Lenette
authors.initials: L
authors.lastname: Simons
authors.forename: Quirijn J A
authors.initials: QJ
authors.lastname: van den Bouwhuijsen
authors.forename: E Marielle H
authors.initials: EM
authors.lastname: Bosboom
authors.forename: Frank J H
authors.initials: FJ
authors.lastname: Gijsen
authors.forename: Alina G
authors.initials: AG
authors.lastname: van der Giessen
authors.forename: Frans N
authors.initials: FN
authors.lastname: van de Vosse
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.forename: Antonius F W
authors.initials: AF
authors.lastname: van der Steen
authors.forename: Jacqueline C M
authors.initials: JC
authors.lastname: Witteman
authors.forename: Aad
authors.initials: A
authors.lastname: van der Lugt
authors.forename: Jolanda J
authors.initials: JJ
authors.lastname: Wentzel
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D001783:Blood Flow Velocity; D017536:Carotid Artery, Common / Q000473:pathology / Q000503:physiopathology; D002342:Carotid Artery, External / Q000473:pathology / Q000503:physiopathology; D002343:Carotid Artery, Internal / Q000473:pathology / Q000503:physiopathology; D016893:Carotid Stenosis / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography; D008955:Models, Cardiovascular; D011446:Prospective Studies; D012039:Regional Blood Flow