Zaman Arshad, Higgins David M, Motwani Manish, Kidambi Ananth, Kouwenhoven Marc, Kozerke Sebastian, Greenwood John P, Plein Sven
Multidisciplinary Cardiovascular Research Centre, Division of Cardiovascular and Diabetes Research, Leeds Institute of Genetics, Health & Therapeutics, University of Leeds, Leeds, UK.
J Magn Reson Imaging. 2015 Apr;41(4):1013-20. doi: 10.1002/jmri.24636. Epub 2014 Apr 22.
Intramyocardial hemorrhage and area at risk are both prognostic markers in acute myocardial infarction (AMI). Myocardial T2 and T2 * 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 T2 and T2 * myocardial mapping techniques at 3.0T on a system employing B1 shimming and compared two different methods of B0 shimming.
Fifteen volunteers and six AMI patients were scanned on a 3T system. Volume and image-based (IB) B0 shimming techniques were implemented. Single breath-hold, multiecho gradient, and spin echo sequences were employed from which T2 * and T2 maps were calculated.
In volunteers, there was no significant difference in mean values obtained with volume or IB shimming for T2 mapping (39.1 ± 6.0 msec vs. 39.4 ± 6.1 msec; P > 0.05) or for T2 * mapping (24.2 ± 6.7 msec vs. 24.1 ± 5.2 msec; P > 0.05). There were no significant regional differences in mean T2 values between septal, anterior, and posterior segments with either shimming technique (all P > 0.05); but there were significant regional differences in mean T2 * 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).
At 3.0T, cardiac T2 mapping is robust. Although T2 * mapping is prone to more regional heterogeneity this can be reduced by using IB instead of conventional volume B0 shimming.
心肌内出血和危险区域均为急性心肌梗死（AMI）的预后标志物。心肌T2和T2成像已被用于在1.5T时检测此类组织变化，但由于额外的磁化率变化，这些技术在3.0T时具有挑战性。我们在采用B1匀场的系统上研究了3.0T时的T2和T2心肌成像技术，并比较了两种不同的B0匀场方法。
对15名志愿者和6名AMI患者在3T系统上进行扫描。实施了基于容积和基于图像（IB）的B0匀场技术。采用单次屏气、多回波梯度和自旋回波序列，从中计算T2*和T2图。
在志愿者中，采用容积或IB匀场获得的T2成像平均值（39.1±6.0毫秒对39.4±6.1毫秒；P>0.05）或T2成像平均值（24.2±6.7毫秒对24.1±5.2毫秒；P>0.05）无显著差异。两种匀场技术在间隔、前壁和后壁节段之间的平均T2值均无显著区域差异（所有P>0.05）；但采用容积匀场时平均T2值存在显著区域差异（27.8±5.2毫秒对28.4±5.8毫秒对15.9±8.毫秒；P<0.05），而采用IB匀场时则无差异（25.7±5.4毫秒对25.3±5.9毫秒对±4.6毫秒；P>0.05）。
在3.0T时，心脏T2成像稳定可靠。虽然T2*成像更容易出现区域异质性，但通过使用IB而非传统的容积B0匀场可以减少这种情况。
