Michaeli Shalom, Garwood Michael, Zhu Xiao-Hong, DelaBarre Lance, Andersen Peter, Adriany Gregor, Merkle Hellmut, Ugurbil Kamil, Chen Wei
Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota School of Medicine, Minneapolis, Minnesota 55455, USA.
Magn Reson Med. 2002 Apr;47(4):629-33. doi: 10.1002/mrm.10135.
Carr-Purcell and Hahn spin-echo (SE) measurements were used to estimate the apparent transverse relaxation time constant (T2) of water and metabolites in human brain at 4T and 7T. A significant reduction in the T2 values of proton resonances (water, N-acetylaspartate, and creatine/phosphocreatine) was observed with increasing magnetic field strength and was attributed mainly to increased dynamic dephasing due to increased local susceptibility gradients. At high field, signal loss resulting from T2 decay can be substantially reduced using a Carr-Purcell-type SE sequence.
采用卡-珀自旋回波（SE）测量技术，在4T和7T磁场强度下估算人脑内水和代谢物的表观横向弛豫时间常数（T2）。研究发现，随着磁场强度增加，质子共振（水、N-乙酰天门冬氨酸和肌酸/磷酸肌酸）的T2值显著降低，这主要归因于局部磁化率梯度增加导致的动态去相位增强。在高磁场下，使用卡-珀型SE序列可大幅减少因T2衰减导致的信号损失。
