Kaiser Lana G, Young Karl, Matson Gerald B
Northern California Institute for Research and Education, San Francisco, California, USA.
Magn Reson Med. 2007 Oct;58(4):813-8. doi: 10.1002/mrm.21407.
Unambiguous detection of gamma-amino butyric acid (GABA) in the human brain is hindered by low concentration and spectral overlap with other metabolites. The popular MEGA-PRESS (PRESS: point-resolved spectroscopic sequence) method allows spectral separation of GABA from other metabolites, but suffers from a significant signal-to-noise ratio (SNR) reduction due to the 4-compartment artifact. An alternative PRESS localization technique (PRESS+4) was investigated and compared to MEGA-PRESS using numerical simulations, phantom, and in vivo experiments. It was shown that while the MEGA-PRESS method suffers significant signal loss ( approximately equal 20% for the difference spectrum), GABA signal intensity in PRESS+4 is reduced by only 2% compared to the nonlocalized condition at 4T. The improved method retains important features of the popular MEGA-PRESS such as additional water suppression and macromolecular elimination as demonstrated in human brain experiments. This method is not limited to GABA J-difference editing, but can be applied in any PRESS-based experiments. It should prove particularly useful at higher field, where the 4-compartment artifact is especially detrimental.
人脑内γ-氨基丁酸（GABA）浓度较低且与其他代谢物存在光谱重叠，这阻碍了对其进行明确检测。常用的MEGA-PRESS（PRESS：点分辨光谱序列）方法能够实现GABA与其他代谢物的光谱分离，但由于四腔伪影，其信噪比（SNR）显著降低。研究了一种替代的PRESS定位技术（PRESS+4），并通过数值模拟、模型实验和体内实验将其与MEGA-PRESS进行比较。结果表明，MEGA-PRESS方法存在显著的信号损失（差异光谱约损失20%），而在4T场强下，与非定位情况相比，PRESS+4中的GABA信号强度仅降低了2%。改进后的方法保留了常用MEGA-PRESS的重要特性，如额外的水抑制和大分子消除，人脑实验已证明了这一点。该方法不仅限于GABA J-差异编辑，还可应用于任何基于PRESS的实验。在更高场强下，四腔伪影的影响尤为严重，该方法在这种情况下应会特别有用。
