Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

Hendriks, A.D., Fracasso, A. , Arteaga de Castro, C.S., Gosselink, M.W.J.M., Luijten, P.R., Petridou, N. and Klomp, D.W.J. (2018) Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T. NMR in Biomedicine, 31(4), e3890. (doi: 10.1002/nbm.3890) (PMID:29442388) (PMCID:PMC5887933)

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The combination of functional MRI (fMRI) and MRS is a promising approach to relate BOLD imaging to neuronal metabolism, especially at high field strength. However, typical scan times for GABA edited spectroscopy are of the order of 6-30 min, which is long compared with functional changes observed with fMRI. The aim of this study is to reduce scan time and increase GABA sensitivity for edited spectroscopy in the human visual cortex, by enlarging the volume of activated tissue in the primary visual cortex. A dedicated setup at 7 T for combined fMRI and GABA MRS is developed. This setup consists of a half volume multi-transmit coil with a large screen for visual cortex activation, two high density receive arrays and an optimized single-voxel MEGA-sLASER sequence with macromolecular suppression for signal acquisition. The coil setup performance as well as the GABA measurement speed, SNR, and stability were evaluated. A 2.2-fold gain of the average SNR for GABA detection was obtained, as compared with a conventional 7 T setup. This was achieved by increasing the viewing angle of the participant with respect to the visual stimulus, thereby activating almost the entire primary visual cortex, allowing larger spectroscopy measurement volumes and resulting in an improved GABA SNR. Fewer than 16 signal averages, lasting 1 min 23 s in total, were needed for the GABA fit method to become stable, as demonstrated in three participants. The stability of the measurement setup was sufficient to detect GABA with an accuracy of 5, as determined with a GABA phantom. In vivo, larger variations in GABA concentration are found: 14-25. Overall, the results bring functional GABA detections at a temporal resolution closer to the physiological time scale of BOLD cortex activation.

Item Type:Articles
Additional Information:This work was supported in part by the Netherlands Organization for Scientific Research (NWO) Vidi Grant 13339 (Petridou).
Keywords:Amino acids, chemical activation, ferromagnetic resonance, magnetic resonance imaging, signal processing, aminobutyric acids, functional MRI (fMRI), half volume coil, high field strengths, MEGA-sLASER, primary visual cortex, spectroscopy measurements, visual cortexes, functional neuroimaging.
Glasgow Author(s) Enlighten ID:Fracasso, Dr Alessio
Authors: Hendriks, A.D., Fracasso, A., Arteaga de Castro, C.S., Gosselink, M.W.J.M., Luijten, P.R., Petridou, N., and Klomp, D.W.J.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:NMR in Biomedicine
ISSN (Online):1099-1492
Published Online:14 February 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in NMR in Biomedicine 31(4): e3890
Publisher Policy:Reproduced under a Creative Commons License

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