AUTHOR=Marsman Anouk , Boer Vincent O. , Luijten Peter R. , Hulshoff Pol Hilleke E. , Klomp Dennis W. J. , Mandl René C. W. 

TITLE=Detection of Glutamate Alterations in the Human Brain Using 1H-MRS: Comparison of STEAM and sLASER at 7 T

JOURNAL=Frontiers in Psychiatry

VOLUME=Volume 8 - 2017

YEAR=2017

URL=https://www.frontiersin.org/journals/psychiatry/articles/10.3389/fpsyt.2017.00060

DOI=10.3389/fpsyt.2017.00060

ISSN=1664-0640

ABSTRACT=Purpose: To assess reproducibility of glutamate measurement in the human brain by two short TE 1H-MRS sequences (STEAM and sLASER) at 7T.  Reliable assessment of glutamate is important when studying a variety of neurological and neuropsychiatric disorders. At 7T, the glutamate signal can be separated from the glutamine signal and hence more accurately measured as compared to lower field strengths. A sLASER sequence has been developed for 7T, using field focusing at short TE resulting in twice as much signal as can be obtained using STEAM, and improved localization accuracy due to a decreased chemical shift artifact. 
Materials and Methods: Eight subjects were scanned twice using  both STEAM and sLASER. Data was acquired from the frontal and occipital brain region. Subsequently,  intraclass correlations (ICC) were computed for the estimated metabolite concentrations. 
Results: sLASER has higher ICC’s for glutamate concentration as compared to STEAM in both the frontal and occipital VOI, which is probably due to the higher sensitivity and localization accuracy. 
Conclusion: We conclude that sLASER 1H-MRS at 7T is a reliable method to obtain reproducible measures of glutamate levels in the human brain at such high accuracy that individual variability, even between age-matched subjects, is measured.