Glutamate is an important neurotransmitter. Although many studies have measured glutamate concentration in vivo using magnetic resonance spectroscopy (MRS), researchers have not reached a consensus on the accuracy of glutamate quantification at the field strength of 3 T. Besides, there is not an optimal MRS protocol for glutamate measurement. In this work, both simulation and phantom scans indicate that glutamate can be estimated with reasonable accuracy (<10% error on average) using the standard Point‐RESolved Spectroscopy (PRESS) technique with TE 30 ms; glutamine, however, is likely underestimated, which is also suggested by results from human scans using the same protocol. The phantom results show an underestimation of glutamate and glutamine for PRESS with long TE and MEGA‐PRESS off‐resonance spectra. Despite the underestimation, there is a high correlation between the measured values and the true values (r > 0.8). Our results suggest that the quantification of glutamate and glutamine is reliable but can be off by a scaling factor, depending on the imaging technique. The outputs from all three PRESS sequences (TE = 30, 68 and 80 ms) are also highly correlated with each other (r > 0.7) and moderately correlated (r > 0.5) with the results from the MEGA‐PRESS difference spectra with moderate to good shimming (linewidth < 16 Hz).

中文翻译：

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使用 PRESS 和 MEGA-PRESS 进行谷氨酸定量的研究

谷氨酸是一种重要的神经递质。尽管许多研究已经使用磁共振波谱 (MRS) 测量了体内谷氨酸浓度，但研究人员尚未就 3 T 场强下谷氨酸定量的准确性达成共识。此外，还没有用于谷氨酸测量的最佳 MRS 协议。在这项工作中，模拟和体模扫描均表明，使用 TE 30 ms 的标准点分辨光谱 (PRESS) 技术可以以合理的准确度（平均误差<10%）估计谷氨酸盐；然而，谷氨酰胺可能被低估了，使用相同方案的人体扫描结果也表明了这一点。幻像结果显示，对于具有长 TE 和 MEGA-PRESS 非共振光谱的 PRESS，谷氨酸盐和谷氨酰胺被低估了。尽管低估，r > 0.8）。我们的结果表明，谷氨酸和谷氨酰胺的量化是可靠的，但可能会因缩放因子而异，具体取决于成像技术。所有三个 PRESS 序列（TE = 30、68 和 80 ms）的输出也彼此高度相关 ( r > 0.7) 并与 MEGA-PRESS 差分光谱的结果中度相关 ( r > 0.5) 中度至良好的匀场（线宽 < 16 Hz）。