Purpose: The aim of the study was to develop and validate a new localized (1)H MRS pulse sequence and automated post-processing software for the quantification of brain Glutamate (Glu) in clinical conditions at 7.0T in order to get reliable and reproducible results for acute intervention studies.
Methods: Here we describe a new localized proton MRS method "Fully Automated MacrOmolecUle Suppressed Single Voxel Glutamate Spectroscopy (FAMOUS SVGS)" for measuring Glu. FAMOUS SVGS method consists of a new pulse sequence with optimized switchable water, metabolites and outer volume suppression modules, as well as a frequency selective inversion pulse and automated post-processing of the five spectra obtained. FAMOUS SVGS method was first validated with glutamate phantoms and then validated with test-retest repeatability studies in the occipital cortex of five normal volunteers at 7.0T.
Results: Glutamate concentrations estimated from phantoms with FAMOUS SVGS method correlated well with actual concentrations. Test-retest repeatability studies in human brain in vivo yielded less than 0.3 mM intra-subject variations in Glu concentrations.
Conclusions: FAMOUS SVGS method enables Glu quantification in vivo at 7.0T with test-retest variability of less than 0.3 mM. We expect that we can reliably measure ≥0.5 mM change in glutamate due to any acute intervention.
Keywords: Glutamate quantification; Single voxel 1H MRS.