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.

Keywords:

• Magnetic resonance imaging (MRI)
• R₂
• R₂*
• T₂
• T₂*
• Iron-overload
• Thalassemia
• Chelation therapy
• Deferoxamine (DFO)
• Deferiprone (L1)

Notes

*Presented at the 16th International Conference on Chelation, Limassol, Cyprus, October 25–31, 2006.