dc.description.abstract | Cerebral aneurysms are unstable localized dilations of an artery wall located in the
vasculature of the brain that are susceptible to rupture. Current treatments of aneurysms,
both surgical and endovascular, involve isolation of the weakened area of artery from the
rest of the vasculature. However, current filling methods do not result in optimal healing.
Therefore, we are developing an alternative filling method using shape memory polymer
(SMP) foams. This dissertation addresses multiple post processing methods and
characterization of these SMP foams. The goals for characterizations addressed include
1) microstructure, 2) radio-opacity, 3) biocompatibility, 4) mechanical reticulation, 5)
flow visualization via magnetic resonance imaging and 6) permeability measurements.
The microstructure of the SMP foams was imaged via micro-computed tomography
imaging methods at high resolution, 4 μm/voxel. At this resolution we were able to
resolve membranes, struts and obtain 3D models of the foam for computational fluid
dynamic simulations. Histogram data of average pore cells sizes in multiple axes were
also measured. It was shown that these materials are anisotropic and heterogeneous.
Increased radio-opacity via loading methods resulted in x-ray based visualization of
devices made of these materials during endovascular implantation. The addition of high-z
element particulates for radio-opacity resulted in a stronger or composite version of the
material.
It was shown that these shape memory polymer foams were biocompatible when
implanted in a porcine aneurysm model. The implants elicited healing, were completely
isolated from the parent vessel and covered with a complete endothelial cell layer at
ninety days.
A non-destructive mechanical reticulation device was made to puncture the
membranes of the foams and thereby increase flow permeation. The permeability, or
pressure drop induced by the samples was measured. Permeability results showed that
with the increased amount of mechanical reticulation resulted in increased permeability
of these materials. Flow visualization within the samples was achieved via MRI at sub
pore cell resolution.
All of this research aids in not only the understanding but also the development of
these materials as a viable medical device for the treatment of intracranial aneurysms and
other vascular applications. | en |