title: Is the macromolecule signal tissue-specific in healthy human brain? A (1)H MRS study at 7 Tesla in the occipital lobe.
abstract: OBJECTIVE
  The macromolecule signal plays a key role in the precision and the accuracy of the metabolite quantification in short-TE (1) H MR spectroscopy. Macromolecules have been reported at 1.5 Tesla (T) to depend on the cerebral studied region and to be age specific. As metabolite concentrations vary locally, information about the profile of the macromolecule signal in different tissues may be of crucial importance.
  
  
  METHODS
  The aim of this study was to investigate, at 7T for healthy subjects, the neurochemical profile differences provided by macromolecule signal measured in two different tissues in the occipital lobe, predominantly composed of white matter tissue or of grey matter tissue.
  
  
  RESULTS
  White matter-rich macromolecule signal was relatively lower than the gray matter-rich macromolecule signal from 1.5 to 1.8 ppm and from 2.3 to 2.5 ppm with mean difference over these regions of 7% and 12% (relative to the reference peak at 0.9 ppm), respectively. The neurochemical profiles, when using either of the two macromolecule signals, were similar for 11 reliably quantified metabolites (CRLB < 20%) with relatively small concentration differences (< 0.3 μmol/g), except Glu (± 0.8 μmol/g).
  
  
  CONCLUSIONS
  Given the small quantification differences, we conclude that a general macromolecule baseline provides a sufficiently accurate neurochemical profile in occipital lobe at 7T in healthy human brain.
authors.affiliation: Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédèrale de Lausanne, Lausanne, Switzerland.
authors.forename: Benoît
authors.initials: B
authors.lastname: Schaller
authors.forename: Lijing
authors.initials: L
authors.lastname: Xin
authors.forename: Rolf
authors.initials: R
authors.lastname: Gruetter
mesh_terms: D000328:Adult; D001921:Brain / Q000378:metabolism*; D005260:Female; D066128:Gray Matter / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances / Q000378:metabolism*; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009778:Occipital Lobe / Q000378:metabolism*; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D066127:White Matter / Q000378:metabolism*; D055815:Young Adult
chemical_list: D046911:Macromolecular Substances; D018377:Neurotransmitter Agents
keywords: 7T; In vivo 1H MRS; healthy human brain; macromolecule signal; metabolite quantification; neurochemical profile