Relationship between hepatic iron concentration and the SIR of liver to muscle with (A) T1-weighted images derived from GE pulse sequences and with (B) T2-weighted images derived from TSE pulse sequences. To facilitate assessment of the clinical use of magnetic resonance imaging as a means of measuring hepatic iron, hepatic iron concentration is plotted on a scale that encompasses the entire range typically found in patients with transfusional iron overload, from normal to more than 50 mg iron per gram liver, dry weight. The normal range is indicated by a gray band extending up to about 1.6 mg iron per gram liver, dry weight. A horizontal gray line at a concentration of 7 mg iron per gram liver, dry weight, indicates the upper limit of the “optimal” range in patients with transfusional iron overload.28 Another horizontal gray line at a concentration of 15 mg iron per gram liver, dry weight indicates a “threshold” for the development of cardiac disease and early death in patients with thalassemia major and transfusional iron overload.1