Localized proton MRS of the human hippocampus: Metabolite concentrations and relaxation times

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Abstract
Absolute concentrations and proton relaxation times of major metabolites in the human hippocampus were determined with use of fully relaxed, short‐echo time STEAM localization sequences at 2.0 T (20 normal adults). Mean metabolite concentrations were 7.6 ± 0.9 mM for total N‐acetylaspartate (tNAA), 6.9 ± 0.8 mM for total creatine (tCr), 2.1 ± 0.3 mM for choline‐containing compounds (Cho), and 6.2 ± 0.9 mM for myo‐inositol (Ins). The observation of relatively low tNAA and high Cho and Ins levels compared with cortical gray and white matter corresponds to a lower neuronal density and higher glial density than in the neocortex, in agreement with histologic findings. The data do not support a lateralization of metabolites. T1 and T2 relaxation times were in the range of 1400–1730 and 140–330 msec, respectively, similar to those in other brain regions. Magn Reson Med 41:204‐207, 1999.