WET, A T-1-INSENSITIVE AND B-1-INSENSITIVE WATER-SUPPRESSION METHOD FOR IN-VIVO LOCALIZED H-1-NMR SPECTROSCOPY
WET, A T-1-INSENSITIVE AND B-1-INSENSITIVE WATER-SUPPRESSION METHOD FOR IN-VIVO LOCALIZED H-1-NMR SPECTROSCOPY
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DOI：
10.1006/jmrb.1994.1048
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发表时间：
1994-05-01
期刊：
影响因子：
--
通讯作者：
TAYLOR, JS
中科院分区：
文献类型：
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作者：
OGG, RJ;KINGSLEY, PB;TAYLOR, JS
通过频率选择性射频脉冲和梯度移相脉冲的重复序列在H-1磁共振光谱期间抑制水信号需要使水磁化的纵向分量为零，因此受到T-1弛豫、RE脉冲翻转角（取决于B-1）和序列定时的影响。在体内应用中，样品内的T-1和B-1不均匀性可能导致空间不均匀的水抑制。一种改进的水抑制技术称为WET（通过T-1效应增强的水抑制），该技术是从在感兴趣的T-1和B-1范围上的纵向磁化的布洛赫方程分析开发的，该技术利用四个RF脉冲实现了T-1和B-1不敏感的抑制，每个RF脉冲具有数值优化的翻转角。一旦针对给定序列优化了翻转角度，就可以消除临床检查期间耗时的翻转角度调整。这种水抑制技术的特征在于相对于T-1的变化，B-1的变化，非共振效应，和部分饱和效应，并与类似的技术进行了比较。在1.5T下对50多名脑肿瘤患者进行的单体素光谱检查中，使用这种新技术实现了有效的水抑制。(C)1994年出版社出版。
Suppression of the water signal during H-1 magnetic resonance spectroscopy by repeated sequences of a frequency-selective radiofrequency pulse and a gradient dephasing pulse requires nulling of the longitudinal component of the water magnetization and is therefore affected by T-1 relaxation, RE-pulse flip angles (which depend on B-1), and sequence timing. In in vivo applications, T-1 and B-1 inhomogeneity within the sample may cause spatially inhomogeneous water suppression. An improved water-suppression technique called WET (water suppression enhanced through T-1 effects), developed from a Bloch equation analysis of the longitudinal magnetization over the T-1 and B-1 ranges of interest, achieves T-1- and B-1-insensitive suppression with four RF pulses, each having a numerically optimized flip angle. Once flip angles have been optimized for a given sequence, time-consuming flip-angle adjustments during clinical examinations are eliminated. This water-suppression technique was characterized with respect to T-1 variations, B-1 variations, off-resonance effects, and partial saturation effects and was compared to similar techniques. Effective water suppression has been achieved with this new technique in single-voxel spectroscopy examinations of more than 50 brain tumor patients at 1.5 T. (C) 1994 Academic Press, Inc.