Evaluation of particulate embolic materials with MR imaging, scanning electron microscopy, and phase-contrast microscopy

PURPOSE: To analyze the properties and embolic effect of microfibrillar collagen (MFC), Gelfoam powder, and polyvinyl alcohol (PVA) materials that are used in embolization procedures in the head and neck. METHODS: The shape and surface of these embolic agents were examined with scanning electron microscopy and phase-contrast microscopy. The mean number of areas of T2- weighted high signal intensity was measured on MR images in a rat embolization model to estimate the embolic effect. RESULTS: By scanning electron microscopy and phase-contrast microscopy, MFC appears fibriform and has various sizes and an irregular surface. Gelfoam is of uniform size and has a smooth surface. PVA materials are granulated and have a rough surface. MFC is somewhat suspendable and its shape changes moderately after suspension. Gelfoam is very suspendable and its shape changes rapidly. PVA showed only mild swelling. The embolic effect of MFC was the lowest of the materials examined. Large PVA particles (250 to 500 μm) showed a lesser embolic effect than Gelfoam or small PVA particles (50 to 150 μm) or medium- sized PVA particles (150 to 250 μm). No significant differences were observed among the embolic effects of Gelfoam, small PVA particles (50 to 150 μm), and medium PVA particles (150 to 250 μm). CONCLUSIONS: MFC and large PVA particles (250 to 500 μm) should be used for embolization involving homogeneous and peripheral anatomy.