Duan, Xinjie
(2016)
The Link between Hemodynamics and Wall Structure in Cerebral Aneurysms.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Intracranial aneurysms (IAs) are pathological enlargements of the walls of cerebral arteries. Rupture of aneurysms causes 80% of subarachnoid hemorrhages. It is generally accepted that the abnormal hemodynamics within the aneurysm sac can lead to a breakdown in the normal process of collagen renewal and remodeling leaving the aneurysm vulnerable to rupture. However, the link between hemodynamics and wall integrity, as well as the underlying mechanisms governing the aneurysm pathophysiology remain poorly understood.
To investigate the variability of wall structure and mechanical properties within the human unruptured aneurysms, we performed uniaxial mechanical testing on samples resected from aneurysm walls with simultaneous multiphoton microscopy imaging of collagen structure. Significant variations in collagen architecture and mechanical response were found in unruptured aneurysms. Factor of Safety (FoS) was used to quantitatively assess the structural integrity of aneurysms, and subcategorize the unruptured population.
In order to further improve the assessment of the structural integrity of the unruptured population, intramural stresses were obtained from FEA with patient-specific models and used for FoS estimation. In this case study, histological investigation of ECM suggests that aneurysms with high FoS are capable of bearing biaxial loading with collagen fibers in two main directions inside the wall and dispersed on the abluminal side. The robust IAs display a rich cell content that is distributed into distinct layers. The collagen architecture in these layers displays similar functional roles to the medial and adventitial layers of the control basilar artery.
To study the connection between aneurysmal hemodynamic conditions and the mechanical properties of the aneurysms wall, we constructed computational fluid dynamics models from 3DRA images. Statistically significant correlations between hemodynamic quantities and failure characteristics and high strain stiffness of the wall were found.
In order to assess the correlation between local hemodynamics and local wall structure, we developed a methodology for mapping the resected aneurysm sample onto a reconstruction of the lumen. Local collagen structure was accessed at multiple areas, and was correlated with the local hemodynamics. In the case study used to illustrate this methodology, high wall shear stress was found to be associated with sparse, inhomogeneous fiber architectures.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
15 June 2016 |
| Date Type: |
Publication |
| Defense Date: |
17 December 2015 |
| Approval Date: |
15 June 2016 |
| Submission Date: |
15 January 2016 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
142 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Mechanical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
cerebral aneurysm, remodeling, structural integrity, hemodynamics, rupture risk, correlation |
| Date Deposited: |
15 Jun 2016 19:19 |
| Last Modified: |
15 Nov 2016 14:31 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/26734 |
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