Characterization of Shape Memory Polymer Foam: Biocompatibility, Visualization and Hemodynamic Interactions

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