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The reliability of a single-voxel, localized proton magnetic resonance spectroscopy protocol suitable for clinical studies was investigated by means of in vitro, single-subject in vivo and multi-subject in vivo examinations of healthy adults aged from 19 to 67 years. The study was performed at 1.5 T using a standard quadrature head coil and a single voxel PRESS sequence (in vitro TR/TE = 1500/30 ms, in vivo TR/TE=2000/35 ms). Eighty-four in vitro and 30 single-subject examinations were statistically evaluated after quantification, including the calculation of the coefficients of variations (CV) for choline (Cho), creatine (Cr), myo-inositol (mI), lactate (Lac), N-acetyl-aspartate (NAA) and unresolved glutamine, glutamate and GABA (Glx). The CVs for absolute concentrations of the main metabolites Cho, Cr and NAA, ranged from 3.3% (3.8) to 4.0% (6.4%) (the in vivo results are given in brackets). Multi-subject CVs of absolute concentrations for Cho, Cr and NAA ranged from 7.6% to 15.0%. CVs of relative in vivo concentrations were found to be higher than CVs of absolute concentrations. Due to the better reproducibility of intra-individual absolute in vivo concentrations, cross-over studies using institutional units are recommended.
Schirmer et al. (Tue,) studied this question.