Date of Award

December 2016

Degree Type

Thesis

Degree Name

Master of Science

Department

Engineering

First Advisor

Anoop Dhingra

Second Advisor

Vitaliy Rayz

Committee Members

Guilherme Garcia

Keywords

Aneurysm, Basilar, CFD, Flow, Modeling, Simulation

Abstract

Computer simulation is a useful tool in the research and treatment of basilar aneurysms. Current technology allows researchers to create 3D models from cerebral vasculature in-vivo, allowing for the investigation of surgical options with minimal risk to the patient. The method used to construct these models overlooks smaller lateral arterial branches which are difficult to discern due to resolution limits of the imaging process. These lateral branches have minimal impact on the overall blood flow through the basilar artery, but they play a significant role in the health of the patient, so it is important to ensure sufficient blood will reach them after treatment is performed.

In order to simulate the flow through the basilar artery and its branches, these smaller vessels must be added to the model manually. These lateral branches vary widely in size, location, and quantity between patients, but the resulting blood flow patterns through the basilar artery are relatively consistent.

The purpose of this thesis is to gain a better understanding of how differences in the modeling of these lateral branches will affect the overall blood flow patterns both through the basilar artery and the branches themselves. The results of this investigation will help researchers to make more accurate models when simulating the flow through these lateral branches.

The study was performed through a series of simulations in which the geometric variables in these branches: length, size, quantity, and location were altered and compared. A second set of simulations was performed to further investigate the use of a constant resistance as a replacement for artery length.

The results of the study show that the flow resistance due to the length of an artery could be approximated using a constant pressure, but some wall length must be present in the model to avoid causing a flow disturbance. The location of the vessels did not appear to have a significant impact on the flow patterns. Increasing the number of arteries results in an overall increase in outlet area, which causes a reduction in blood velocity exiting the basilar artery. No other significant changes in the flow patterns were observed. Altering the size of the vessels had a similarly predictable change in flow distribution, with a greater increase in flow per area increase, which follows Poiseuille’s model for laminar flow through tubes.

The results from the second series of simulations verified that modifying the static distal pressure at an artery could accurately replace adjusting the artery length. These studies showed the importance of accounting for the flow distribution, the recirculation regions, and the flow mixing when determining this distal outlet pressure.

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