Robust Myocardial T2 and T2* Mapping at 3T Using Image-Based Shimming

PurposeIntramyocardial 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 MethodsFifteen 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. ResultsIn volunteers, there was no significant difference in mean values obtained with volume or IB shimming for T-2 mapping (39.16.0 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). ConclusionAt 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. (c) 2014 Wiley Periodicals, Inc.