Reproducibility of the Whole-Brain N-Acetylaspartate Level across Institutions, MR Scanners, and Field Strengths

Sample whole-head ¹H-MR spectroscopy spectra from each of the MR imaging instruments used, with institution and field strength indicated. Although all the proton metabolites can be seen in the spectrum, note that because it was acquired in a whole-head, nonlocalized fashion, only the NAA peak is implicitly localized to the brain. The area of the NAA peak of the subject S_S, was integrated in each subject as shown and converted into absolute millimoles, Q_NAA, by comparing with the NAA peak area, S_R, in a reference phantom of known concentration as described by Eq. 1. Note the excellent signal-to-noise ratio of this short acquisition and the nearly total elimination of the skull’s lipid signals from obscuring the spectrum.