Differentiation between hemosiderin- and ferritin-bound brain iron using nuclear magnetic resonance and magnetic resonance imaging

MRI is an optimal clinical (research) tool to provide information on brain morphology and pathology and to detect metal ions that possess intrinsic ma gnetic properties. Non-heme iron is abundantly present in the brain in thre e different forms: "low molecular weight" complexes, iron bound to "medium mollecular weight complexes" metalloproteins such as transferrin, and "high molecular weight" complexes as ferritin and hemosiderin. The total amount and form of iron may differ in health and disease, and MRT. can possibly qu antify and monitor such changes. Ferritin-bound iron is the main storage fo rm of iron and is present predominantly in the extrapyramidal nuclei where its amounts normally increase as a function of age. Ferritin is water solub le and shortens both, T-1 and T-2 relaxation, with as result a signal chang e on the MR images. Hemosiderin, a degradation product of ferritin, is wate r-insoluble with a stronger T-2 shortening effect than ferritin. The larger cluster size of hemosiderin and its water-insolubility also explain a lack of significant T-1-shortening effect on T-1-weighted images. Using both in vitro specimens and intact brain tissue in vivo we demonstrate here that M RT may be able to distinguish between ferritin- and hemosiderin-bound iron.