title: Elucidation of the downfield spectrum of human brain at 7 T using multiple inversion recovery delays and echo times.
abstract: To characterize the downfield spectrum at 5-10 ppm in the human brain at a high magnetic field of 7 T. Knowledge of relaxation parameters is of interest for spectroscopy as well as chemical exchange-dependent saturation transfer experiments.
  
  
  
  Water-suppressed spectra were recorded as echo time and inversion time series in healthy volunteers to investigate T2and T1values of downfield peaks in gray matter at 7T. The spectra were fitted in a two-dimensional fashion to a heuristic model of a series of Voigt lines, and the relaxation times were obtained for 12 peaks of interest.
  
  
  
  The mean T2values averaged over the volunteers ranged from 24 to 158 ms, whereas the mean T1values ranged from 0.22 to 2.40 s. Spectra of specific inversion and echo times revealed superposition of the amide peaks of N-acetylaspartate with short T2and an inhomogeneously broadened component with longer T2.
  
  
  
  T2values were shorter than expected for most peaks, whereas T1values had a very wide range; shorter relaxation times for some peaks suggests the presence of macromolecules. Most of the larger peaks seemed to be composed of overlapping components, because the Gaussian widths in the Voigt line shape descriptions were larger than expected based on field inhomogeneities. Magn Reson Med 78:11-19, 2016. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Radiology, Neuroradiology, and Nuclear Medicine, University of Bern, Bern, Switzerland.|Department of Clinical Research, University of Bern, Bern, Switzerland.|Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.|Institute for Biomedical Engineering, UZH and ETH Zurich, Zurich, Switzerland.
authors.forename: Nicole D
authors.initials: ND
authors.lastname: Fichtner
authors.affiliation: Institute for Biomedical Engineering, UZH and ETH Zurich, Zurich, Switzerland.|Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Henning
authors.affiliation: Institute for Biomedical Engineering, UZH and ETH Zurich, Zurich, Switzerland.
authors.forename: Niklaus
authors.initials: N
authors.lastname: Zoelch
authors.affiliation: Department of Radiology, Neuroradiology, and Nuclear Medicine, University of Bern, Bern, Switzerland.|Department of Clinical Research, University of Bern, Bern, Switzerland.
authors.forename: Chris
authors.initials: C
authors.lastname: Boesch
authors.affiliation: Department of Radiology, Neuroradiology, and Nuclear Medicine, University of Bern, Bern, Switzerland.|Department of Clinical Research, University of Bern, Bern, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: Kreis
mesh_terms: D000465:Algorithms; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis; D001704:Biopolymers / Q000032:analysis*; D001923:Brain Chemistry; D003198:Computer Simulation; D066128:Gray Matter / Q000737:chemistry*; D006801:Humans; D008956:Models, Chemical; D008959:Models, Neurological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
chemical_list: D001704:Biopolymers; D001224:Aspartic Acid; C000179:N-acetylaspartate
keywords: 7 T; T1 relaxation time; T2 relaxation time; human brain; metabolites; proton MR spectroscopy