Changes in N.m.r. Relaxation times of Iron Overloaded Mouse Tissue

The values of proton relaxation times (T^ and T2) of human or animal tissues play an important role in NMR imaging since the image contrast is mainly determined by these parameters. Based on T^ and T2 measurements of healthy and abnormal tissues pulse sequences can be proposed to improve the diagnosis of a specific disease. Many factors can effect relaxation rates such as the rate of water exchanges between compartments with different relaxation times, temperature and the presence of paramagnetic impurities in tissues. Several human diseases are accompanied by excessive iron accumulation, either spontaneous, as in idiopathic hemochromatosis, or transfusion induced, as in thalassemias or sickle cell anemia. In normal individuals, iron is stored mainly in reticuloendothelial (RE) cells; however, excessive iron can be located either in RE or parenchymal cells of several tissues, including the liver. RE iron overload may have toxic effects. Within the cells, iron is stored primarily inside ferritin molecules as hydrous ferric oxide-phosphate, a paramagnetic complex. Hemosiderin is the other paramagnetic iron storage molecule lack ing the protein coat that involves iron in ferritin (1).