Longitudinal inter‐ and intra‐individual human brain metabolic quantification over 3 years with proton MR spectroscopy at 3 T

The longitudinal repeatability of proton MR spectroscopy (1H‐MRS) in the healthy human brain at high fields over long periods is not established. Therefore, we assessed the inter‐ and intra‐subject repeatability of 1H‐MRS in an approach suited for diffuse pathologies in 10 individuals, at 3T, annually for 3 years. Spectra from 480 voxels over 360 cm3 (∼30%) of the brain, were individually phased, frequency‐aligned, and summed into one average spectrum. This dramatically increases metabolites' signal‐to‐noise‐ratios while maintaining narrow linewidths that improve quantification precision. The resulting concentrations of the N‐acetylaspartate, creatine, choline, and myo‐inositol are: 8.9 ± 0.8, 5.9 ± 0.6, 1.4 ± 0.1, and 4.5 ± 0.5 mM (mean ± standard‐deviation). the inter‐subject coefficients of variation are 8.7%, 10.2%, 10.7%, and 11.8%; and the longitudinal (intra‐subject) coefficients of variation are lower still: 6.6%, 6.8%, 6.8%, and 10%, much better than the 35%, 44%, 55%, and 62% intra‐voxel coefficients of variation. The biological and nonbiological components of the summed spectra coefficients of variation had similar contributions to the overall variance. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.