Reproducibility of 1H-MRS in vivo.

The current study sought to investigate the reproducibility of a quantitative spectroscopic examination, using rigorous positioning guidelines and automated spectral fitting for measuring the cerebral metabolites N-acetylaspartate (NAA), creatine (Cre), choline (Cho), and myo-inositol (ml). Ten subjects were studied in three sessions to determine the variability associated with measurement of metabolites in normal-appearing occipitoparietal white matter, using short echo STEAM spectroscopy. A careful relocalization protocol based on local landmarks identified on thin-slice images was used. No changes in mean metabolite concentrations for each subject between sessions were found, confirming relocalization. Mean coefficients of variation in measurement of NAA, Cre, Cho, and ml were 3.30, 4.33, 5.30, and 8.10, respectively. These data suggest that changes in metabolite concentrations as small as 12% can be confidently discerned in an individual subject over time. The implication of these results to study design is discussed.