Department of Medical Physics, Uppsala University Hospital, Uppsala, Sweden.
Department of Neuroscience, Uppsala University, Uppsala, Sweden.
PLoS One. 2021 Jan 15;16(1):e0240641. doi: 10.1371/journal.pone.0240641. eCollection 2021.
γ-Aminobutyric acid (GABA) is a primary inhibitory neurotransmitter in the human brain. It has been shown that altered GABA concentration plays an important role in a variety of psychiatric and neurological disorders. The main purpose of this study was to propose a combination of PRESS and MEGA-PRESS acquisitions for absolute GABA quantification and to compare GABA estimations obtained using total choline (tCho), total creatine (tCr), and total N-acetyl aspartate (tNAA) as the internal concentration references with water referenced quantification. The second aim was to demonstrate the fitting approach of MEGA-PRESS spectra with QuasarX algorithm using a basis set of GABA, glutamate, glutamine, and NAA in vitro spectra. Thirteen volunteers were scanned with the MEGA-PRESS sequence at 3T. Interleaved water referencing was used for quantification, B0 drift correction and to update the carrier frequency of RF pulses in real time. Reference metabolite concentrations were acquired using a PRESS sequence with short TE (30 ms) and long TR (5000 ms). Absolute concentration were corrected for cerebrospinal fluid, gray and white matter water fractions and relaxation effects. Water referenced GABA estimations were significantly higher compared to the values obtained by metabolite references. We conclude that QuasarX algorithm together with the basis set of in vitro spectra improves reliability of GABA+ fitting. The proposed GABA quantification method with PRESS and MEGA-PRESS acquisitions enables the utilization of tCho, tCr, and tNAA as internal concentration references. The use of different concentration references have a good potential to improve the reliability of GABA estimation.
γ-氨基丁酸（GABA）是人类大脑中的主要抑制性神经递质。已经表明，改变 GABA 浓度在各种精神和神经疾病中起着重要作用。本研究的主要目的是提出 PRESS 和 MEGA-PRESS 采集的组合，用于绝对 GABA 定量，并比较使用总胆碱（tCho）、总肌酸（tCr）和总 N-乙酰天冬氨酸（tNAA）作为内部浓度参考物与水参考定量获得的 GABA 估计值。第二个目的是使用 QuasarX 算法展示 MEGA-PRESS 谱与体外 GABA、谷氨酸、谷氨酰胺和 NAA 光谱的拟合方法。13 名志愿者在 3T 下用 MEGA-PRESS 序列进行扫描。使用水参考进行定量、B0 漂移校正和实时更新 RF 脉冲的载波频率。使用具有短 TE（30ms）和长 TR（5000ms）的 PRESS 序列获取参考代谢物浓度。绝对浓度校正了脑脊液、灰质和白质水分数和弛豫效应。与代谢物参考获得的值相比，水参考 GABA 估计值显著更高。我们得出结论，QuasarX 算法与体外光谱的基础集一起提高了 GABA+拟合的可靠性。使用 PRESS 和 MEGA-PRESS 采集的 GABA 定量方法可以利用 tCho、tCr 和 tNAA 作为内部浓度参考。使用不同的浓度参考物具有提高 GABA 估计可靠性的良好潜力。
