title: Investigating brain metabolism at high fields using localized 13C NMR spectroscopy without 1H decoupling.
abstract: Most in vivo 13C NMR spectroscopy studies in the brain have been performed using 1H decoupling during acquisition. Decoupling imposes significant constraints on the experimental setup (particularly for human studies at high magnetic field) in order to stay within safety limits for power deposition. We show here that incorporation of the 13C label from 13C-labeled glucose into brain amino acids can be monitored accurately using localized 13C NMR spectroscopy without the application of 1H decoupling. Using LCModel quantification with prior knowledge of one-bond and multiple-bond J(CH) coupling constants, the uncertainty on metabolites concentrations was only 35% to 91% higher (depending on the carbon resonance of interest) in undecoupled spectra compared to decoupled spectra in the rat brain at 9.4 Tesla. Although less sensitive, 13C NMR without decoupling dramatically reduces experimental constraints on coil setup and pulse sequence design required to keep power deposition within safety guidelines. This opens the prospect of safely measuring 13C NMR spectra in humans at varied brain locations (not only the occipital lobe) and at very high magnetic fields above 4 Tesla.
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA. dinesh@cmrr.umn.edu
authors.forename: Dinesh Kumar
authors.initials: DK
authors.lastname: Deelchand
authors.forename: Kâmil
authors.initials: K
authors.lastname: Uğurbil
authors.forename: Pierre-Gilles
authors.initials: PG
authors.lastname: Henry
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002247:Carbon Isotopes; D005240:Feasibility Studies; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009010:Monte Carlo Method; D051381:Rats; D012815:Signal Processing, Computer-Assisted
chemical_list: D002247:Carbon Isotopes; D005973:Glutamine; D001224:Aspartic Acid; D018698:Glutamic Acid