Computational and Experimental Evaluation of Actuating Shape Memory Polymer Foams in the Context of Aneurysm Treatment

Shape memory polymer foams may be used to treat vascular aneurysms through thermal actuation of the foam from a compacted to an expanded configuration within the aneurysm structure, thereby alleviating blood pressure on the weakened aneurysm walls and reducing potential for rupture. After delivery to the aneurysm site, fiber-delivered laser light absorbed by the foam structure is converted into thermal energy, and actuation of the foam results. Introduction of nonphysiological energy into the body during foam actuation necessitates an evaluation of potential thermal damage to nearby tissue. In the present investigation, the foam is idealized as a heat-dissipating, volumetrically static object centered in a straight tube of flowing water. Velocity profiles around the heat-dissipating device are acquired experimentally with particle image velocimetry. A computational fluid dynamics package is then used to predict the experimental velocity profiles and temperature distributions by numerical solution of the Navier-Stokes and energy equations, and agreement between the computational solution and experimental results is assessed. Discussion of this assessment, as well as several preliminary procedures leading up to the creation of the heat-dissipating device and critical analysis of the methods employed, is also given. PIV and CFD are found to be in reasonable agreement with one another. Using laser-induced fluorescence as a temperature measurement modality, which is discussed in the text insofar as the technique was attempted several times and failed, together with PIV and CFD provides a formidable array of techniques exists to characterize flow around a heated device