title: Magnetite albumin microspheres: a new MR contrast material.
abstract: A superparamagnetic MR contrast agent was synthesized by incorporating 150-250-A particles of magnetite (Fe3O4, Fe2O3) in 1-5 microns human serum albumin microspheres. Magnetite albumin microspheres (MAM) target almost exclusively to the reticuloendothelial system after IV administration, are stable in vitro and in vivo, and possess a long shelf life. The agent has a large magnetic susceptibility effect that selectively reduces T2 with little effect on T1. Biodistribution studies that use a dose of 20 mg MAM/kg show prompt clearance from the blood pool with marked decrease in T2 for rat liver (40%) and spleen (45%) with a small decrease in liver (5%) and spleen (10%) T1 values. Pulmonary T1 and T2 decrease transiently over the first 24 hr, while no significant changes were observed in other tissues. Imaging of a rabbit VX2 tumor model resulted in a 200% increase in the contrast ratio of VX2 tumor to normal liver on T2-weighted and mixed T1-/T2-weighted pulse sequences after administration of contrast agent. The extreme potency, excellent targeting, and apparent lack of toxicity of this agent suggest that MAM probably will have a clinical application in detecting focal hepatic and splenic lesions.
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000378:metabolism / Q000633:toxicity; D052203:Ferrosoferric Oxide; D006801:Humans; D007501:Iron; D008114:Liver Neoplasms, Experimental / Q000175:diagnosis; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008863:Microspheres; D010087:Oxides; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D012709:Serum Albumin; D014018:Tissue Distribution
chemical_list: D003287:Contrast Media; D010087:Oxides; D012709:Serum Albumin; D007501:Iron; D052203:Ferrosoferric Oxide