| abstract |
A method of imaging a tumor by magnetic resonance imaging (MRI) of liver and/or spleen is provided which employes microspheres composed of a biodegradeable matrix material with a particulate superparamagnetic contrast agent therein. The microspheres have diameters of less than 1.5 microns, and the ferromagnetic contrast agent, such as magnetite, has a particle size below 300 Angstroms. The superparamagnetic microspheres when administered intravenously segregate through the reticuloendothelial system in the liver and spleen where they reduce the T 2 relaxation time to obtain improved MR imaging. In the T 2 or mixed T 1 and T 2 images obtained by the MRI examination, the normal liver and spleen tissues appear dark and the tumor appears light with distinct margins therebetween. |