Computational Fluid Dynamics of Human Cerebral Circulation- A Study of Shear Stress in the Circle of Willis with and without Constructed Aneurysms
Typ
Examensarbete på kandidatnivå
Program
Publicerad
2019
Författare
Abass, Amir
Andersson, Carl
Berggren, Henrik
Ahlgren, Kajsa
Ignell, Victoria
Koivistoinen, Vilma
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
A cerebral aneurysm is a local enlargement of a weakened blood vessel wall in the brain. It is a
critical condition that causes several deaths yearly due to the fatal intracranial bleeding that a
rupture of an aneurysm can cause. This report investigates aneurysms with focus on their impact
on shear stress in blood vessels where aneurysms are often found. This is done with the aim to gain
further knowledge about the correlation between mechanical factors and aneurysm progression.
Throughout the report images of brains from two healthy patients, taken with magnetic resonance
imaging, serve as a fundamental basis of real-world representation of blood vessels in the human
brain. The scanned images were reconstructed into three-dimensional volumetric data to use for
simulations. A total of seven specific vascular geometries were chosen from the two brains. All
were selected in the Circle of Willis, a specific section in the lower central part of the brain. The
Circle of Willis is a domain particularly prone to the development of aneurysms. Since the images
originated from healthy patients the chosen geometries did not contain any aneurysms. Therefore
a modified copy of each selected geometry was created as well, with the difference being that they
contained a virtually inserted aneurysm.
The blood flow of the reconstructed vascular geometries was computed and simulated using the
Lattice Boltzmann method. It is a numerical method that recovers the Navier-Stokes continuity
and generates the velocity field within the chosen blood vessel geometries. The blood flow was
simulated in all seven pairs of blood vessels. With the acquisition of the velocity distribution
within the vessel, the corresponding distribution of shear stress was calculated. Results from
the simulations were compared between the cases with and without aneurysm with respect to
shear stress. The concluding result was that a global increase in shear stress was found for the
geometries with an aneurysm. This result suggests that the progression of one aneurysm could
lead to a weakened blood vessel that is likely to develop an increased number of aneurysms.
Beskrivning
Ämne/nyckelord
Lattice Boltzmann, Cerebral aneurysm, Cerebral circulation, CFD, Vascular system