Interindividual, repositioning, and time-of-day effects on single voxel proton MR spectroscopy of the anterior cingulate cortex.

PURPOSE: To measure interindividual, repositioning, and time-of-day effects of single voxel PRESS (Point RESolved Spectroscopy) proton magnetic resonance spectroscopy ((1)H-MRS) acquisition of the anterior cingulate cortex (AC) in healthy human subjects. MATERIALS AND METHODS: AC (1)H-MRS measurements were performed in 15 healthy adult volunteers using a short echo PRESS sequence (GE Healthcare 3 Tesla, TE/TR = 30/2500 ms, 192 acquisitions, 6 cm(3) voxels). For each individual, a total of eight spectra were obtained during two identical scanning sessions separated by 3.5 h. In each, two consecutive AC spectra were acquired. After the first two scans, the subject left the scanner, then immediately returned for repositioning and acquisition of two more consecutive spectra. The subject then left the imaging centre to return 3.5 h later for a repeated procedure. Spectroscopic postprocessing was done using LCmodel. Interindividual, repositioning and time-of-day effects were measured using restricted maximum likelihood (REML) models of variance components analysis, where response variables were levels of creatine/phosphocreatine (Cr), N-acetyl-aspartate (NAA), myo-inositol (mI), choline (Cho), and the glutamate-glutamine complex (Glx). RESULTS: Interindividual effects were markedly higher than time-of-day and repositioning effects for all metabolites. CONCLUSION: Our findings show that (1)H-MRS measurements of the AC are sensitive to interindividual differences, while time of day and repositioning are markedly less important.