• Tamar M van Veenendaal, Walter H Backes, Frank C G van Bussel, Edden Richard A E RAE Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, 601 N Caroline St, Baltimore, MD 21287, USA; F.M. Kirb, Nicolaas A J Puts, Albert P Aldenkamp, and Jansen Jacobus F A JFA Departments of Radiology and Nuclear Medicine, Maastricht University Medical Center, P.O. Box 5800, 6202, AZ, Maastricht, The Netherlands; School f.
• Departments of Radiology and Nuclear Medicine, Maastricht University Medical Center, P.O. Box 5800, 6202, AZ, Maastricht, The Netherlands; School for Mental Health and Neuroscience, Maastricht University, P.O. Box 616, 6200, MD, Maastricht, The Netherlands.
• Magn Reson Imaging. 2018 May 1; 48: 107-114.

PurposeWhile PRESS is often employed to measure glutamate concentrations, MEGA-PRESS enables simultaneous Glx (glutamate and glutamine) and GABA measurements. This study aimed to compare validation, repeatability, and concordance of different approaches for glutamate quantification at 3T to aid future studies in their selection of the appropriate sequence and quantification method.Materials And MethodsNine phantoms with different glutamate and glutamine concentrations and five healthy participants were scanned twice to assess respectively the validation and repeatability of measurements with PRESS and MEGA-PRESS. To assess concordance between the different methods, results from 95 human participants were compared. PRESS, MEGA-PRESS (i.e. difference), and the MEGA-PRESS OFF spectra were analyzed with both LCModel and Gannet.ResultsIn vitro, excellent agreement was shown between actual and measured glutamate concentrations for all measurements (r>0.98). In vivo CVs were better for PRESS (2.9%) than MEGA-PRESS (4.9%) and MEGA-PRESS OFF (4.2%). However, the concordance between the sequences was low (PRESS and MEGA-PRESS OFF, r=0.3) to modest (MEGA-PRESS versus MEGA-PRESS OFF, r=0.8).ConclusionBoth PRESS and MEGA-PRESS can be employed to measure in vivo glutamate concentrations, although PRESS shows a better repeatability. Comparisons between in vivo glutamate measures of different sequences however need to be interpreted cautiously.Copyright © 2018 Elsevier Inc. All rights reserved.

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