Short TE single‐voxel 1H‐MR spectroscopy of hippocampal structures in healthy adults at 1.5 Tesla—how reproducible are the results?

The purpose of our study was to evaluate inter‐ and intra‐subject variability and scan–rescan reproducibility of single‐voxel 1H‐MR spectroscopy (1H‐MRS) in hippocampal structures at 1.5 T field strength. Thirty healthy adults were studied bilaterally by optimized, standardized short echo time single‐voxel 1H‐MRS (PRESS, TE=30 ms, TR=3000 ms, oblique voxel orientation, voxel size 2 cm3). Spectral analysis and absolute metabolite quantitation of N‐acetylaspartate+N‐acetylaspartyl‐glutamate (tNAA), choline (Cho), creatine (Cr), total glutamate plus glutamine (Glu+Gln) and myo‐inositol (Ins) were carried out by LCModel. Inter‐ and intra‐individual reproducibility of these metabolite values were investigated by calculation of mean, standard deviation, coefficient of variation (CV), and by analysis of variance for repeated measurements. The smallest CV in intersubject variability was obtained for tNAA, followed by Cr, Cho, Ins and Glu+Gln. The results of the analysis of variance for repeated measures in inter‐subject variability showed a marginal effect of scan repetition for Cr (p=0.063) and Glu+Gln (p=0.082); the rescan of both metabolites showed slightly higher concentrations. No statistical significant effect of scan repetition was seen for tNAA (p=0.913), Cho (p=0.857), and Ins (p=0.826). Rescan led to the same results and gave proof of good reproducibility. Scan–rescan testing in one subject showed comparable results: tNAA (CV=4.8%), followed by Cr, Ins, Glu+Gln and Cho (all CV above 10%). Copyright © 2005 John Wiley & Sons, Ltd.