Purpose To assess volumetric proton MR spectroscopic imaging of the human brain on multi-vendor MRI instruments. Methods Echo-planar spectroscopic imaging (EPSI) was developed on instruments from three manufacturers, with matched specifications and acquisition protocols that accounted for differences in sampling performance, RF power, and data formats. Inter-site reproducibility was evaluated for signal-normalized maps of N-acetylaspartate (NAA), Creatine (Cre) and Choline using phantom and human subject measurements. Comparative analyses included metrics for spectral quality, spatial coverage, and mean values in atlas-registered brain regions. Results Inter-site differences for phantom measurements were under 1.7% for individual metabolites and 0.2% for ratio measurements. Spatial uniformity ranged from 79% to 91%. The human studies found differences of mean values in the temporal lobe, but good agreement in other white-matter regions, with maximum differences relative to their mean of under 3.2%. For NAA/Cre, the maximum difference was 1.8%. In grey-matter a significant difference was observed for frontal lobe NAA. Primary causes of inter-site differences were attributed to shim quality, B0 drift, and accuracy of RF excitation. Correlation coefficients for measurements at each site were over 0.60, indicating good reliability. Conclusion A volumetric intensity-normalized MRSI acquisition can be implemented in a comparable manner across multi-vendor MR instruments.

Knowledge of physiological aging in healthy human brain is increasingly important for neuroscientific research and clinical diagnosis. To investigate neuronal decline in normal aging brain eighty-one healthy subjects aged between 20 to 70 years were studied with MRI and whole-brain 1H-MR spectroscopic imaging. Concentrations of brain metabolites N-acetyl-aspartate (NAA), choline (Cho), total creatine (tCr), myo-inositol (mI), and glutamine+glutamate (Glx) in ratios to internal water, and the fractional volumes of brain tissue were estimated simultaneously in eight cerebral lobes and in cerebellum. Results demonstrated that an age-related decrease in gray matter volume was the largest contribution to changes in brain volume. Both lobar NAA and the fractional volume of gray matter (FVGM) decreased with age in all cerebral lobes, indicating that the decreased NAA was predominantly associated with decreased gray matter volume and neuronal density or metabolic activity. In cerebral white matter Cho, tCr, and mI increased with age in association with increased fractional volume, showing altered cellular membrane turn-over, energy metabolism, and glial activity in human aging white matter. In cerebellum tCr increased while brain tissue volume decreased with age, showing difference to cerebral aging. The observed age-related metabolic and microstructural variations suggest that physiological neuronal decline in aging human brain is associated with a reduction of gray matter volume and neuronal density, in combination with cellular aging in white matter indicated by microstructural alterations and altered energy metabolism in the cerebellum.

Purpose A feasibility study of a short TE EPSI that trades off sensitivity, compared with other short-TE methods, to achieve whole brain coverage, using inversion recovery and spatial oversampling to control lipid bleeding. Methods Twenty subjects were scanned to examine inter-subject variance. One subject was scanned 5 times to examine intra-subject reproducibility. Data were analyzed to determine coefficients of variance (COV) and intra-class correlation coefficient (ICC) for N–acetylaspartate (NAA), total creatine (tCr), choline (Cho), glutamine/glutamate (Glx) and myo-inositol (ml). Regional metabolite concentrations were derived by using multi-voxel analysis based on lobar level anatomic regions. Results For whole brain mean values the intra-subject COVs were 14%, 15%, and 20% for NAA, tCr, and Cho respectively, and 31% for Glx and ml. The inter-subject COVs were up to 6% higher. For regional distributions the intra-subject COVs were ≤ 5% for NAA, tCr, Cho, ≤ 9% for Glx, and ≤15% for ml, with about 6% higher inter-subject COVs. The ICCs of 5 metabolites were ≥ 0.7, indicating the reliability of the measurements. Conclusion The present EPSI method enables estimation of the whole brain metabolite distributions including Glx and ml with small voxel size, and a reasonable scan time and reproducibility.