EVALUATION OF PARTICULATE EMBOLIC MATERIALS WITH MR-IMAGING, SCANNINGELECTRON-MICROSCOPY, AND PHASE-CONTRAST MICROSCOPY

PURPOSE: To analyze the properties and embolic effect of microfibrilla r collagen (MFC), Gelfoam powder, and polyvinyl alcohol (PVA) material s that are used in embolization procedures in the head and neck, METHO DS: The shape and surface of these embolic agents were examined with s canning electron microscopy and phase-contrast microscopy. The mean nu mber of areas of Ta-weighted high signal intensity was measured on MR images in a rat embolization model to estimate the embolic effect. RES ULTS: By scanning electron microscopy and phase-contrast microscopy, M FC appears fibriform and has various sizes and an irregular surface. G elfoam is of uniform size and has a smooth surface, PVA materials are granulated and have a rough surface. MFC is somewhat suspendable and i ts shape changes moderately after suspension, Gelfoam is very suspenda ble 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 mu m) showed a lesser embolic effect than Ge lfoam or small PVA particles (50 to 150 mu m) or medium-sized PVA part icles (150 to 250 mu m) No significant differences were observed among the embolic effects of Gelfoam, small PVA particles (50 to 150 mu m), and medium PVA particles (150 to 250 mu m). CONCLUSIONS: MFC and larg e PVA particles (250 to 500 mu m) should be used for embolization of v ascular anatomy involving potentially dangerous anastomoses. Gelfoam, PVA particles of 150- to 250-mu m diameter, and PVA particles of 50- t o 150-mu m diameter are adequate for embolization involving homogeneou s and peripheral anatomy.