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Metabolite‐cycled STEAM and semi‐LASER localization for MR spectroscopy of the human brain at 9.4T
Author(s) -
Giapitzakis IoannisAngelos,
Shao Tingting,
Avdievich Nikolai,
Mekle Ralf,
Kreis Roland,
Henning Anke
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26873
Subject(s) - laser , nuclear magnetic resonance , voxel , laser linewidth , chemistry , metabolite , spectroscopy , analytical chemistry (journal) , materials science , optics , physics , chromatography , computer science , biochemistry , quantum mechanics , artificial intelligence
Purpose Metabolite cycling (MC) is an MRS technique for the simultaneous acquisition of water and metabolite spectra that avoids chemical exchange saturation transfer effects and for which water may serve as a reference signal or contain additional information in functional or diffusion studies. Here, MC was developed for human investigations at ultrahigh field. Methods MC‐STEAM and MC‐semi‐LASER are introduced at 9.4T with an optimized inversion pulse and elaborate coil setup. Experimental and simulation results are given for the implementation of adiabatic inversion pulses for MC. The two techniques are compared, and the effect of frequency and phase correction based on the MC water spectra is evaluated. Finally, absolute quantification of metabolites is performed. Results The proposed coil configuration results in a maximumB 1 +of 48 μΤ in a voxel within the occipital lobe. Frequency and phase correction of single acquisitions improve signal‐to‐noise ratio (SNR) and linewidth, leading to high‐resolution spectra. The improvement of SNR of N‐acetylaspartate (SNR NAA ) for frequency aligned data, acquired with MC‐STEAM and MC‐semi‐LASER, are 37% and 30%, respectively ( P < 0.05). Moreover, a doubling of the SNR NAA for MC‐semi‐LASER in comparison with MC‐STEAM is observed ( P < 0.05). Concentration levels for 18 metabolites from the human occipital lobe are reported, as acquired with both MC‐STEAM and MC‐semi‐LASER. Conclusion This work introduces a novel methodology for single‐voxel MRS on a 9.4T whole‐body scanner and highlights the advantages of semi‐LASER compared to STEAM in terms of excitation profile. In comparison with MC‐STEAM, MC‐semi‐LASER yields spectra with higher SNR. Magn Reson Med 79:1841–1850, 2018. © 2017 International Society for Magnetic Resonance in Medicine.