COUPLING EFFECTS IN VOLUME SELECTIVE H-1 SPECTROSCOPY OF MAJOR BRAIN-METABOLITES
COUPLING EFFECTS IN VOLUME SELECTIVE H-1 SPECTROSCOPY OF MAJOR BRAIN-METABOLITES
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DOI：
10.1002/mrm.1910210111
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发表时间：
1991-09-01
影响因子：
3.3
通讯作者：
HENNIG, J
中科院分区：
文献类型：
--
作者：
ERNST, T;HENNIG, J
以弱耦合AX和A2X体系为例，讨论了压力和水蒸气顺序对偶合物质光谱的影响。如果将RF脉冲应用于反相磁化，则会出现与未耦合自旋相比的最大差异。在这种情况下，PRESS实验的自旋回波显示出对重聚焦翻转角度的修正依赖，这可能导致采集的信号衰减。在水蒸气光谱中，中程TMI的演化主要由零量子相干和纵向极化主导，其最大效率分别为25%和12.5%。当tm值变化时，零量子相干可能导致强调制。对人脑中重要的偶联代谢物，如谷氨酸、GABA、肌醇，特别是乳酸的光谱的影响被证明。观测到的调制似乎使回波时间超过50ms时光谱的量化变得相当困难。©1991学术出版社，Inc.
The effect of PRESS and STEAM sequences on the spectra of coupled substances are discussed using the examples of weakly coupled AX and A2X systems. Maximum differences compared to uncoupled spins occur if the RF pulses are applied to antiphase magnetization. In this case, the spin echo of the PRESS experiment shows a modified dependence on the refocusing flip angle, which may lead to an attenuation of the acquired signal. In STEAM spectroscopy the evolution within the middle interval tmis dominated by zero quantum coherences and longitudinal polarization, whose maximum efficiencies are 25 and 12.5%, respectively. Zero quantum coherences may lead to strong modulations when the tmvalue is varied. The effects on the spectra of important coupled metabolites of the human brain such as glutamate, GABA, inositol, and particularly lactate, are demonstrated. The observed modulations seem to make the quantification of the spectra rather difficult at echo times above 50 ms. © 1991 Academic Press, Inc.