Spectral simplification for resolved glutamate and glutamine measurement using a standard STEAM sequence with optimized timing parameters at 3, 4, 4.7, 7, and 9.4 T
Spectral simplification for resolved glutamate and glutamine measurement using a standard STEAM sequence with optimized timing parameters at 3, 4, 4.7, 7, and 9.4 T
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DOI：
10.1002/mrm.21463
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发表时间：
2008-02-01
影响因子：
3.3
通讯作者：
Yang, Yihong
中科院分区：
文献类型：
--
作者：
Yang, Shaolin;Hu, Jiani;Yang, Yihong
2.35 ppm 左右的谷氨酸 (Glu) 和 2.45 ppm 左右的谷氨酰胺 (Gin) 的 C4 多重质子共振通常在 MR 光谱中重叠，特别是在低场和中场强度 (1.54.7T) 下。引入了光谱简化方法，该方法使用具有优化脉冲间时序的标准 STEAM 定位序列来提供无障碍的 Glu 和 Gin 测量。基本思想是利用耦合自旋系统的响应对回波时间（TE）和混合时间（TM）的依赖性来找到最佳定时集（TE，TM），在该定时集上，Glu和Gin的C4“伪三重态”质子共振的外翼被显着抑制，同时保持中心峰。因此，光谱重叠得到解决，因为重叠仅存在于外翼处，并且由于化学位移的大约 0.1 ppm 差异，中心峰很容易分离。对 2.3-2.5 ppm 的 Glu、Gin 和其他重叠代谢物进行密度矩阵模拟，以预测最佳时间设置。模拟、模型和体内结果表明，Glu 和 Gin 的 C4 多重质子共振可以在 3T、4T 和 4.7T 下进行无障碍检测。为了简单起见，仅示出了 7T 和 9AT 下的模拟数据。
The C4 multiplet proton resonances of glutamate (Glu) around 2.35 ppm and glutamine (Gin) around 2.45 ppm usually overlap in MR spectra, particularly at low- and mid-field strengths (1.54.7T). A spectral simplification approach is introduced that provides unobstructed Glu and Gin measurement using a standard STEAM localization sequence with optimized interpulse timings. The underlying idea is to exploit the dependence of response of a coupled spin system on the echo time (TE) and mixing time (TM) to find an optimum timing set (TE, TM), at which the outer-wings of C4 "pseudo-triplet" proton resonances of Glu and Gin are significantly suppressed while the central peaks are maintained. The spectral overlap is thus resolved as the overlap exists exclusively at the outer-wings and the central peaks are readily separated due to the approximate 0.1-ppm difference in chemical shift. Density matrix simulation for Glu, Gin, and other overlapping metabolites at 2.3-2.5 ppm was conducted to predict the optimum timing sets. The simulated, phantom, and in vivo results demonstrated that the C4 multiplet proton resonances of Glu and Gin can be resolved for unobstructed detection at 3T, 4T, and 4.7T. For simplicity, only simulated data are illustrated at 7T and 9AT.