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TECHNICAL PAPERS: Fluids/Heat/Transport

# Blood Flow Dynamics in Saccular Aneurysm Models of the Basilar Artery

[+] Author and Article Information
Alvaro A. Valencia

Mechanical Engineering, Universidad de Chile, Casilla 2777, Santiago, Chilealvalenc@ing.uchile.cl

Mechanical Engineering, Universidad de Santiago de Chile, Casilla 10233, Santiago, Chileaguzman@usach.cl

Ender A. Finol

Institute for Complex Engineered Systems, Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890finole@cmu.edu

Cristina H. Amon

Mechanical Engineering, Biomedical Engineering, and Institute for Complex Engineered Systems, Carnegie Mellon University, Pittsburgh, PA 15213-3890camon@cmu.edu

J Biomech Eng 128(4), 516-526 (Feb 03, 2006) (11 pages) doi:10.1115/1.2205377 History: Received March 11, 2005; Revised February 03, 2006

## Abstract

Blood flow dynamics under physiologically realistic pulsatile conditions plays an important role in the growth, rupture, and surgical treatment of intracranial aneurysms. The temporal and spatial variations of wall pressure and wall shear stress in the aneurysm are hypothesized to be correlated with its continuous expansion and eventual rupture. In addition, the assessment of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils. This paper describes the flow dynamics in two representative models of a terminal aneurysm of the basilar artery under Newtonian and non-Newtonian fluid assumptions, and compares their hemodynamics with that of a healthy basilar artery. Virtual aneurysm models are investigated numerically, with geometric features defined by $β=0deg$ and $β=23.2deg$, where $β$ is the tilt angle of the aneurysm dome with respect to the basilar artery. The intra-aneurysmal pulsatile flow shows complex ring vortex structures for $β=0deg$ and single recirculation regions for $β=23.2deg$ during both systole and diastole. The pressure and shear stress on the aneurysm wall exhibit large temporal and spatial variations for both models. When compared to a non-Newtonian fluid, the symmetric aneurysm model $(β=0deg)$ exhibits a more unstable Newtonian flow dynamics, although with a lower peak wall shear stress than the asymmetric model $(β=23.2deg)$. The non-Newtonian fluid assumption yields more stable flows than a Newtonian fluid, for the same inlet flow rate. Both fluid modeling assumptions, however, lead to asymmetric oscillatory flows inside the aneurysm dome.

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## Figures

Figure 1

Model geometries (all dimensions in mm): (a) Healthy basilar artery model, (b) aneurysm model 1 – with β=0deg, (c) aneurysm model 2 – with β=0deg

Figure 2

Physiological waveform of mean inlet velocity (Um) in m/s

Figure 3

Representative computational grid used for aneurysm model 2 (β=23.2deg)

Figure 4

Axial velocity versus grid size for two instantaneous times at point P7

Figure 8

Wall shear stress (WSS) for model 1 (β=0deg) with a view from the top of the aneurysm: (a)t=0.1s and (b)t=0.8s, Newtonian fluid; (c)t=0.1s and (d)t=0.8s, non-Newtonian fluid

Figure 10

Flow-induced stresses in aneurysm model 1: (a) Relative wall pressure—pw and (b) wall shear stress—WSS at points P3 and P4 on the wall of model 1 (β=0deg) in the X-Z plane

Figure 11

Flow-induced stresses in aneurysm model 2: (a) Relative wall pressure—pw and (b) wall shear stress—WSS at points P5 and P6 on the wall of model 2 (β=23.2deg) in the Y-Z plane

Figure 12

Flow-induced stresses in the healthy basilar artery model: (a) Relative wall pressure −pw and (b) wall shear stress—WSS at points P1 and P2 on the wall of the healthy basilar artery bifurcation

Figure 13

Temporal evolution of WSS at point P3 in aneurysm model 1 for steady inlet flow rate

Figure 5

Velocity vectors for aneurysm model 1 (β=0deg) and non-Newtonian fluid color-coded with the z-component of the velocity for (a)t=0.1s and (c)t=0.8s at the aneurysm inlet, and color-coded with the velocity magnitude for (b)t=0.1s and (d)t=0.8s at the Y-Z plane of the aneurysm

Figure 6

Velocity vectors for aneurysm model 2 (β=23.2deg) and non-Newtonian fluid color-coded with the z-component of the velocity for (a)t=0.1s and (c)t=0.8s at the aneurysm inlet, and color-coded with the velocity magnitude for (b)t=0.1s and (d)t=0.8s at the Y-Z plane of the aneurysm

Figure 7

Velocity vectors for aneurysm model 1 (β=0deg) and Newtonian fluid, color-coded with the velocity magnitude for (a)t=0.1s and (b)t=0.8s

Figure 9

Wall shear stress (WSS) for model 2 (β=23.2deg) with a view from the top of the aneurysm: (a)t=0.1s and (b)t=0.8s, Newtonian fluid; (c)t=0.1s and (d)t=0.8s, non-Newtonian fluid

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