title: The impact of scaled boundary conditions on wall shear stress computations in atherosclerotic human coronary bifurcations.
abstract: The aim of this study was to determine if reliable patient-specific wall shear stress (WSS) can be computed when diameter-based scaling laws are used to impose the boundary conditions for computational fluid dynamics. This study focused on mildly diseased human coronary bifurcations since they are predilection sites for atherosclerosis. Eight patients scheduled for percutaneous coronary intervention were imaged with angiography. The velocity proximal and distal of a bifurcation was acquired with intravascular Doppler measurements. These measurements were used for inflow and outflow boundary conditions for the first set of WSS computations. For the second set of computations, absolute inflow and outflow ratios were derived from geometry-based scaling laws based on angiography data. Normalized WSS maps per segment were obtained by dividing the absolute WSS by the mean WSS value. Absolute and normalized WSS maps from the measured-approach and the scaled-approach were compared. A reasonable agreement was found between the measured and scaled inflows, with a median difference of 0.08 ml/s [-0.01; 0.20]. The measured and the scaled outflow ratios showed a good agreement: 1.5 percentage points [-19.0; 4.5]. Absolute WSS maps were sensitive to the inflow and outflow variations, and relatively large differences between the two approaches were observed. For normalized WSS maps, the results for the two approaches were equivalent. This study showed that normalized WSS can be obtained from angiography data alone by applying diameter-based scaling laws to define the boundary conditions. Caution should be taken when absolute WSS is assessed from computations using scaled boundary conditions.
authors.affiliation: Department of Biomedical Engineering, Thorax Center, Erasmus Medical Center, Rotterdam, The Netherlands;
authors.forename: Jelle T C
authors.initials: JT
authors.lastname: Schrauwen
authors.affiliation: Department of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, The Netherlands; and.
authors.forename: Janina C V
authors.initials: JC
authors.lastname: Schwarz
authors.affiliation: Department of Biomedical Engineering, Thorax Center, Erasmus Medical Center, Rotterdam, The Netherlands;
authors.forename: Jolanda J
authors.initials: JJ
authors.lastname: Wentzel
authors.affiliation: Department of Biomedical Engineering, Thorax Center, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands.
authors.forename: Antonius F W
authors.initials: AF
authors.lastname: van der Steen
authors.affiliation: Department of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, The Netherlands; and.
authors.forename: Maria
authors.identifier: 0000-0002-7034-5843
authors.initials: M
authors.lastname: Siebes
authors.affiliation: Department of Biomedical Engineering, Thorax Center, Erasmus Medical Center, Rotterdam, The Netherlands; f.gijsen@erasmusmc.nl.
authors.forename: Frank J H
authors.initials: FJ
authors.lastname: Gijsen
mesh_terms: D001783:Blood Flow Velocity; D003198:Computer Simulation; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D057446:Hydrodynamics; D008955:Models, Cardiovascular; D058226:Plaque, Atherosclerotic; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D018608:Ultrasonography, Doppler; D018084:Ultrasonography, Interventional / Q000379:methods*
keywords: CFD; boundary conditions; coronary bifurcation; scaling laws; shear stress