[Secondary hepatic hemochromatosis: diagnosis and quantification with 0.5 T magnetic resonance. Value and limitations].

Iron overload is a major cause of morbidity and mortality in thalassemia major patients. All chronic liver diseases may be associated with such endocrine symptoms as diabetes mellitus, testicular failure or hypothyroidism. We studied 15 thalassemic patients (12 men and 3 women; age range: 10-50 years, mean: 22.5 years). All patients received blood transfusions, but only some were treated with iron chelation. Seven patients were splenectomized. MRI was performed with an 0.5 T superconducting magnet, using SE T1- and T2-weighted and IR sequences. We used these data with Bloch's equation to calculate T1 and T2 values. Quantitative analysis was made by calculating signal intensity and relaxation times in 8 hepatic regions of interest: marked reduction in hepatic signal intensity and a negative relationship between T1 and serum ferritin (r = 0.646, p < 0.01) and between T2 and serum ferritin (r = 0.688, p < 0.01) were observed. Moreover, a negative relationship was found between hepatic signal intensity and aspartic aminotransferase (r = 0.524, p < 0.05). Our results confirm the value of MRI in the diagnosis and evaluation of hepatic iron overload but an accurate quantitative analysis can be made only when hepatic iron levels are between 1 and 2 mg/g of liver. Even though it is below statistical significance, the negative relationship between signal intensity and aspartic aminotransferase suggests that hepatic hemochromatosis can influence pituitary-thyroid axis and interfere with peripheral hormone metabolism.