Estimation of metabolic changes during neuronal activation represents a challenge for in vivo MRS, especially for metabolites with low concentration and signal overlap, such as lactate. In this work, we aimed to evaluate the feasibility of detecting lactate during brain activation using a long T E (144 ms) semi-LASER sequence at 7 T. 1 H spectra were acquired on healthy volunteers ( N = 6 ) during a paradigm with 15 min of visual stimulation. Outer-volume signals were further attenuated by the use of saturation slabs, and macromolecular signals in the vicinity of the inverted lactate peak were individually fitted with simulated Lorentzian peaks. All spectra were free of artefacts and highly reproducible across subjects. Lactate was accurately quantified with an average Cramér-Rao lower bound of 8%. Statistically significant ( P < 0 . 05 , one-tailed t -test) increases in lactate ( ∼ 10%) and glutamate ( ∼ 3%) levels during stimulation were detected in the visual cortex. Lactate and glutamate changes were consistent with previous measurements. We demonstrated that quantification of a clear and non-contaminated lactate peak obtained with a long TE sequence has the potential of improving the accuracy of functional MRS studies targeting non-oxidative reaction pathways.

中文翻译：

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在7 T下使用长TE semi-LASER序列在视觉刺激期间测量脑乳酸。

估计神经元活化过程中的代谢变化代表了体内MRS的挑战，特别是对于浓度低且信号重叠的代谢物（如乳酸）而言。在这项工作中，我们旨在评估在7 T时使用长TE（144 ms）半LASER序列在大脑激活过程中检测乳酸的可行性。在健康志愿者（N = 6）的范例中，使用15个样本获得了1 H光谱分钟的视觉刺激。外体积信号通过使用饱和平板进一步衰减，并且倒乳酸峰附近的大分子信号分别与模拟的洛伦兹峰拟合。所有光谱均无伪像，并且在整个受试者中具有很高的可重复性。乳酸的准确定量平均Cramér-Rao下限为8％。具有统计意义（P <0. 05，在视觉皮层中检测到刺激期间，乳酸（〜10％）的单尾t检验）和谷氨酸（〜3％）的水平增加。乳酸和谷氨酸的变化与以前的测量结果一致。我们证明了量化与一个长的TE序列获得的清晰和无污染的乳酸峰有潜力提高针对非氧化反应途径的功能性MRS研究的准确性。