[The value of nuclear magnetic resonance in the study of iron overload in thalassemia patients].

In patients with thalassemia treated by long-term chronic blood transfusions who survive beyond the first ten or twenty years of life but received no or inadequate chelating therapy during the first years, evaluation of iron overload and its consequences on tissues may prove an arduous task. MRI is a non-invasive means of measuring the amount of iron in the liver and the consequences of the iron overload on the heart and other tissues. For this purpose, MRI is more satisfactory than CT scan studies. In this investigation, 20 patients with thalassemia major underwent MRI. Multiple spin echos were used to allow determination of the transversal relaxation constant T2. This constant, expressed in ms, is related to the concentration of iron in the liver as in the following expression: (C) = 5 410/T2-110. MRI studies disclosed a discrepancy between the severity of hepatic hemosiderosis and development of decompensated iron overload cardiomyopathy. In a unique case, in which a heart transplant and two MRI studies were performed, the severe iron overload that failed to respond to several years of subcutaneous chelating therapy was more than halved by intensive intravenous chelation through a central catheter. MRI studies of the heart provide valuable morphologic and functional data. Although the amount of iron in the myocardium cannot as yet be quantified, modifications of the transversal relaxation time provide information on the severity of the overload and the presence of other myocardial alterations.