Definition

A non-stoichiometric magnetite core of superparamagnetic iron oxide (SPIO) that can be used as part of contrast media to enhance magnetic resonance imaging (MRI). Upon administration, ferumoxides non-stoichiometric magnetite is taken up by and accumulates in phagocytic reticuloendothelial system (RES) cells of the liver (Kupffer cells). When exposed to a strong external magnetic field, ferumoxides non-stoichiometric magnetite exhibits enhanced T2 relaxation, resulting in signal loss in normal tissues (image darkening) on mid T1/T2 or strongly T2-weighted images. Tissues with decreased RES function such as metastases, primary liver cancer, cysts, various benign tumors and hyperplasia, retain their native signal intensity, consequently the contrast between normal tissue (with image darkening) and abnormal tissue is increased.