Star-Lack J M, Spielman D M
Lucas MRS Imaging Center, Department of Radiology, Stanford University, Stanford, California 94305, USA.
Magn Reson Med. 2001 Dec;46(6):1233-7. doi: 10.1002/mrm.1321.
A zero-quantum (ZQ) filter offering single-shot lipid suppression and providing for simultaneous detection of the lactate methyl doublet (1.3 ppm) and nonoverlapping singlets including choline (Cho, 3.2 ppm) and creatine (Cr, 3.0 ppm) is described. Filtering is provided by soft mixing and reading pulses (RF(mix), RF(rd)) that are selective for the lactate methine quartet (4.1 ppm), Cho, and Cr resonances but exclude the 1.3 ppm lactate component and overlapping lipids. Surrounding RF(mix) and RF(rd) are magnetic field gradient pulses of equal magnitude but opposite signs to enable the rephasing of the zero-quantum lactate coherence and the creation of a stimulated echo for singlets within the pulse passbands. The sequence is designed to retain half the original lactate and singlet signal intensities. Theoretical predictions were confirmed experimentally at 1.5T using phantom acquisitions. The lipid suppression factor was measured to be over 10(3).
本文描述了一种零量子(ZQ)滤波器,它能够实现单次脂质抑制,并能同时检测乳酸甲酯双峰(1.3 ppm)以及包括胆碱(Cho,3.2 ppm)和肌酸(Cr,3.0 ppm)在内的不重叠单峰。滤波通过软混合和读取脉冲(RF(mix),RF(rd))实现,这些脉冲对乳酸次甲基四重峰(4.1 ppm)、Cho和Cr共振具有选择性,但排除了1.3 ppm的乳酸成分和重叠的脂质。围绕RF(mix)和RF(rd)的是大小相等但符号相反的磁场梯度脉冲,以实现零量子乳酸相干的重相,并在脉冲通带内为单峰创建受激回波。该序列设计为保留原始乳酸和单峰信号强度的一半。使用体模采集在1.5T下通过实验证实了理论预测。测得的脂质抑制因子超过10³。