Design and Characterization of a Shape Memory Polymer Foam-coated Coil Neurovascular Embolization Device
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Standard endovascular treatment of intracranial saccular aneurysms has been shown to be an effective treatment method, but it remains marked by aneurysm recanalization despite continued development of new device technologies. Polyurethane-based shape memory polymer (SMP) foams are advantageous biomaterials for endovascular embolization applications, however previously developed devices utilizing SMP foam for neurovascular embolization treatment were limited by required catheter sizes, insufficient flexibility and radiopacity, and inconsistent device stability within the aneurysm sac. Solvent-stimulated actuation of hydrophobic SMP foams using DMSO and EtOH was shown to be an effective alternative shape memory trigger to direct heating. Dramatic decreases in Tg were observed with exposure to water, DMSO, and EtOH. Rapid shape recovery and volume swelling were observed for SMP foams in high concentrations of both DMSO and EtOH, as well as in decreased concentrations of EtOH. A SMP foam-over-wire (FOW) neurovascular embolization device was evaluated using in vitro and in vivo saccular aneurysm models as an initial prototype design. In vivo porcine aneurysms were successfully occluded using FOW devices with theoretical volume occlusion values greater than reported values for predicate devices and rapid, stable thrombus formation. FOW devices were successful in treating sidewall aneurysm models, though the study suggested a need to improve the deliverability and radiopacity of the devices and to evaluate the occlusion effectiveness in more clinically relevant aneurysm geometries. A SMP foam-coated coil (FCC) embolization device was designed and demonstrated clinician-familiar deliverability and use combined with large packing density and scaffolding capability of porous SMP foam. Excellent cytocompatibility is a promising early result in showing biocompatibility. FCC devices exhibited smooth delivery, but difficult packing in both benchtop and rabbit elastase aneurysm models highlights the need to improving device stiffness. However, though packing in rabbit aneurysms was poor, the tissue response suggests a desired healing process and a promising indication that the more effectively packed FCC devices will prompt stable, long-term tissue healing. Overall, the device designed through this work demonstrates excellent potential for improving long-term clinical outcomes for patients with intracranial saccular aneurysms, whether ruptured or unruptured.
Boyle, Anthony John (2016). Design and Characterization of a Shape Memory Polymer Foam-coated Coil Neurovascular Embolization Device. Doctoral dissertation, Texas A & M University. Available electronically from