Reliable gamma aminobutyric acid measurement using optimized PRESS at 3 T.

Gamma aminobutyric acid (GABA) is the most important inhibitory neurotransmitter in the central nervous system and there is strong interest in noninvasive measurement of GABA levels to assess GABAergic dysfunction in a number of psychiatric and neurological diseases. GABA detection by proton MR spectroscopy is challenging due to its low concentration as well as its strong overlap with more highly concentrated metabolites; therefore, editing techniques are typically required. In this study, the parameters of a standard point resolved spectroscopy (PRESS) sequence were optimized through repeated simulations to reliably and simultaneously detect GABA and glutamate at 3 T. Experimental validation of the optimized sequence parameters of echo time (TE1)=15 ms and TE=105 ms and careful postprocessing with realignment yielded reliable GABA estimates in the anterior cingulate cortex and precuneus region with test-retest coefficient of variation of 10.4%. The achieved reproducibitilty was thus similar to published MEGA-PRESS data despite smaller voxels and shorter scan time in this study. In conclusion, the optimized sequence parameters reported here allow reliable GABA estimation without additional hardware or software adaptation on clinical scanners.