Robust myocardial T 2 and T 2 * mapping at 3T using image‐based shimming

Purpose Intramyocardial hemorrhage and area at risk are both prognostic markers in acute myocardial infarction (AMI). Myocardial T 2 and T 2 * mapping have been used to detect such tissue changes at 1.5T but these techniques are challenging at 3.0T due to additional susceptibility variation. We studied T 2 and T 2 * myocardial mapping techniques at 3.0T on a system employing B 1 shimming and compared two different methods of B 0 shimming. Materials and Methods Fifteen volunteers and six AMI patients were scanned on a 3T system. Volume and image‐based (IB) B 0 shimming techniques were implemented. Single breath‐hold, multiecho gradient, and spin echo sequences were employed from which T 2 * and T 2 maps were calculated. Results In volunteers, there was no significant difference in mean values obtained with volume or IB shimming for T 2 mapping (39.1 ± 6.0 msec vs. 39.4 ± 6.1 msec; P  > 0.05) or for T 2 * mapping (24.2 ± 6.7 msec vs. 24.1 ± 5.2 msec; P  > 0.05). There were no significant regional differences in mean T 2 values between septal, anterior, and posterior segments with either shimming technique (all P  > 0.05); but there were significant regional differences in mean T 2 * values using volume shimming (27.8 ± 5.2 msec vs. 28.4 ± 5.8 msec vs. 15.9 ± 8.3 msec; P  < 0.05)—but not with IB shimming (25.7 ± 5.4 msec vs. 25.3 ± 5.9 msec vs. 18.7 ± 4.6 msec; P  > 0.05). Conclusion At 3.0T, cardiac T 2 mapping is robust. Although T 2 * mapping is prone to more regional heterogeneity this can be reduced by using IB instead of conventional volume B 0 shimming. J. Magn. Reson. Imaging 2015;41:1013–1020 . © 2014 Wiley Periodicals, Inc .