On Using T2 to Assess Extrinsic Magnetic Field Inhomogeneity Effects Myocardial Siderosis on T2* Measurements in in Thalassemia

Magnetic resonance T-2* has been validated as a noninvasive means of assessing myocardial iron overload. However, the effect on myocardial T-2* of factors such as shimming, variations in capillary geometry, and susceptibility in relation to the effects of iron has not been fully clarified. Since T-2 is not affected by extrinsic magnetic field inhomogeneity and has different sensitivity to capillary geometry, investigation into the in vivo relationship between myocardial T-2* and T-2 measurements can shed light on this important issue. This study was performed in 136 thalassemia patients. The myocardial T-2 and T-2* thresholds for normality created identical no-iron-overload and iron-overloaded patient groups. In the no-iron group, there was no correlation between myocardial T-2 and T-2*. In the iron-overloaded patients, there was a linear correlation (R-2 = 0.89) between myocardial T-2* and T-2 measurements, which indicates that the iron deposition is the dominant factor in determining these two relaxation values in this scenario. Magn Reson Med 61: 501-506, 2009. (C) 2008 Wiley-Liss, Inc.