On using T 2 to assess extrinsic magnetic field inhomogeneity effects on T 2 * measurements in myocardial siderosis 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, 2009. © 2008 Wiley‐Liss, Inc.