Embolization with radiopaque microbeads of polyacrylonitrile hydrogel:: Evaluation in swine

PURPOSE: To perform in vitro and in vivo studies of radiopaque microbeads of polyacrylonitrile (PAN) hydrogel to evaluate their characteristics as embolic material. MATERIALS AND METHODS: PAN microbeads were analyzed in vitro for swelling in different concentrations of contrast material and saline solution and injected through various microcatheters. In three nonsurvival swine, various organs were embolized with PAN microbeads. In eight survival swine, the rete mirabile was embolized with PAN microbeads or polyvinyl alcohol particles. Follow-up angiograms were obtained regularly, and histopathologic analysis was performed at 1 and 6 months. RESULTS: The microbeads were black with a regular shape and smooth surface. They were easily visible in the syringe and easy to inject through the microcatheters. When wet, their diameters increased by 40%. The microbeads were sufficiently radiopaque to be visible in all vascular territories. Vascular occlusion was not permanent, and even when embolization was adequate, some revascularization was detected at 3 months. The microbeads were intact and still radiopaque at 6 months. Histopathologic examination demonstrated variable inflammatory reactions and foreign-body giant cell reaction and no angionecrosis or hemorrhage. CONCLUSION: Because PAN microbeads are biocompatible, radiopaque, and easy to handle during embolization procedures, they have potential as a therapeutic embolic agent.