The Uses and Differences of R2 and R2* in the Determination of Iron Overload in Iron Loaded Thalassemia Patients

Abstract

Early attempts to use magnetic resonance imaging (MRI) for assessing iron overload in β-thalassemia (thal) patients began more than 20 years ago. With advances in MRI, more quantitative efforts focused on measuring transverse relaxation time rates (R2 and R2*) of the liver and/or myocardium. Recently, calibration curves of R2 and R2* were reported that allowed one to determine the absolute concentrations of iron in the liver, provided that R2 and R2* were determined with the same technique. The difficulty of obtaining sufficient myocardium biopsy samples has prevented similar calibration curves being reported for the myocardium. Preliminary data indicate that liver and myocardium R2* vs. R2 plots are similar over a large range of R2* and R2 values. Obviously, myocardium biopsy samples are needed to confirm whether myocardium R2* and R2 plots vs. iron concentration are similar to those published for the liver. The various methods for determining R2 and R2* are discussed. It is suggested to use both R2* and R2 for assessing iron overload in the liver and myocardium.