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Research Papers

Effect of Common Carotid Artery Inlet Length on Normal Carotid Bifurcation Hemodynamics

[+] Author and Article Information
Yiemeng Hoi, David A. Steinman

Biomedical Simulation Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada M5S 3G8

Bruce A. Wasserman

The Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, MD 21205

Edward G. Lakatta

Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 20892

J Biomech Eng 132(12), 121008 (Nov 09, 2010) (6 pages) doi:10.1115/1.4002800 History: Received September 09, 2010; Revised October 03, 2010; Posted October 15, 2010; Published November 09, 2010; Online November 09, 2010

Controversy exists regarding the suitability of fully developed versus measured inlet velocity profiles for image-based computational fluid dynamics (CFD) studies of carotid bifurcation hemodynamics. Here, we attempt to resolve this by investigating the impact of the reconstructed common carotid artery (CCA) inlet length on computed metrics of “disturbed” flow. Twelve normal carotid bifurcation geometries were reconstructed from contrast-enhanced angiograms acquired as part of the Vascular Aging—The Link That Bridges Age to Atherosclerosis study (VALIDATE). The right carotid artery lumen geometry was reconstructed from its brachiocephalic origin to well above the bifurcation, and the CCA was truncated objectively at locations one, three, five, and seven diameters proximal to where it flares into the bifurcation. Relative to the simulations carried out using the full CCA, models truncated at one CCA diameter strongly overestimated the amount of disturbed flow. Substantial improvement was offered by using three CCA diameters, with only minor further improvement using five CCA diameters. With seven CCA diameters, the amounts of disturbed flow agreed unambiguously with those predicted by the corresponding full-length models. Based on these findings, we recommend that image-based CFD models of the carotid bifurcation should incorporate at least three diameters of CCA length if fully developed velocity profiles are to be imposed at the inlet. The need for imposing measured inlet velocity profiles would seem to be relevant only for those cases where the CCA is severely truncated.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

Twelve carotid bifurcation models (cases A–M) reconstructed from CEMRA, shown in coronal and sagittal views. As labeled in panel A, shown also are the locations of the CCA0 origin, the CCA1 plane defining the beginning of the nonflared CCA, and the various cut planes used to truncate the CCA length.

Grahic Jump Location
Figure 2

Color-coded distributions of RRT for all 12 participants for the various CCA lengths indicated at the top row. Black contour lines on each surface identify the area exposed to RRT above its 80th percentile value, as described in Sec. 2. Grayscales (colors online) indicate the areas exposed above the 80th, 90th, and 95th percentile values. Geometries are clipped at the CCA3, ICA5, and ECA2 locations used to bind the surface for disturbed flow calculations.

Grahic Jump Location
Figure 3

Scatter plots of SA exposed to various disturbed flow indicators (WSS, OSI, and RRT), derived from the truncated models and compared against the corresponding SA from the full-length models. Colored lines are linear regressions through the respective colored data points. The black dotted line represents the line of unity.

Grahic Jump Location
Figure 4

Rank plots of SA exposed to various disturbed flow indicators (WSS, OSI, and RRT) as a function of the CCA length. The dashed lines separate SA into lower, middle, and upper tertiles according to the distributions of exposure levels found by Lee (14). Symbols denote the case identifier, and green, yellow, and red are used to highlight the cases (i.e., full-length models) falling into the lower, middle, and upper tertiles, respectively. Connecting lines identify adjacent pairs for which the tertile is different.

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