Embolization with radiopaque microbeads of polyacrylonitrile hydrogel: Evaluation in swine

PURPOSE: To perform in vitro and in vivo studies of radiopaque microbeads o f polyacrylonitrile (PAN) hydrogel to evaluate their characteristics as emb olic material. MATERIALS AND METHODS: PAN microbeads were analyzed in vitro for swelling i n different concentrations of contrast material and saline solution and inj ected through various microcatheters. In three nonsurvival swine, various o rgans 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 mic rocatheters. When wet, their diameters increased by 40%. The microbeads wer e sufficiently radiopaque to be visible in all vascular territories. Vascul ar occlusion was not permanent, and even when embolization was adequate, so me revascularization was detected at 3 months. The microbeads were intact a nd still radiopaque at 6 months. Histopathologic examination demonstrated v ariable 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 therapeu tic embolic agent.