title: Whole-brain quantitative mapping of metabolites using short echo three-dimensional proton MRSI.
abstract: BACKGROUND
  To improve the extent over which whole brain quantitative three-dimensional (3D) magnetic resonance spectroscopic imaging (MRSI) maps can be obtained and be used to explore brain metabolism in a population of healthy volunteers.
  
  
  METHODS
  Two short echo time (20 ms) acquisitions of 3D echo planar spectroscopic imaging at two orientations, one in the anterior commissure-posterior commissure (AC-PC) plane and the second tilted in the AC-PC +15° plane were obtained at 3 Tesla in a group of 10 healthy volunteers. B1 (+) , B1 (-) , and B0 correction procedures and normalization of metabolite signals with quantitative water proton density measurements were performed. A combination of the two spatially normalized 3D-MRSI, using a weighted mean based on the pixel wise standard deviation metabolic maps of each orientation obtained from the whole group, provided metabolite maps for each subject allowing regional metabolic profiles of all parcels of the automated anatomical labeling (AAL) atlas to be obtained.
  
  
  RESULTS
  The combined metabolite maps derived from the two acquisitions reduced the regional intersubject variance. The numbers of AAL regions showing N-acetyl aspartate (NAA) SD/Mean ratios lower than 30% increased from 17 in the AC-PC orientation and 41 in the AC-PC+15° orientation, to a value of 76 regions of 116 for the combined NAA maps. Quantitatively, regional differences in absolute metabolite concentrations (mM) over the whole brain were depicted such as in the GM of frontal lobes (cNAA = 10.03 + 1.71; cCho = 1.78 ± 0.55; cCr = 7.29 ± 1.69; cmIns = 5.30 ± 2.67) and in cerebellum (cNAA = 5.28 ± 1.77; cCho = 1.60 ± 0.41; cCr = 6.95 ± 2.15; cmIns = 3.60 ± 0.74).
  
  
  CONCLUSIONS
  A double-angulation acquisition enables improved metabolic characterization over a wide volume of the brain.
authors.affiliation: CRMBM, Aix-Marseille Université, CNRS 7339, Marseille, France.|APHM, CHU Timone, Pôle d'Imagerie, CEMEREM, Marseille, France.
authors.forename: Angèle
authors.initials: A
authors.lastname: Lecocq
authors.affiliation: CRMBM, Aix-Marseille Université, CNRS 7339, Marseille, France.|APHM, CHU Timone, Pôle d'Imagerie, CEMEREM, Marseille, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Le Fur
authors.affiliation: Department of radiology, Miller School of Medicine, University of Miami, Miami, Florida, USA.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Maudsley
authors.affiliation: CRMBM, Aix-Marseille Université, CNRS 7339, Marseille, France.|APHM, CHU Timone, Pôle d'Imagerie, CEMEREM, Marseille, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Le Troter
authors.affiliation: Department of radiology, Miller School of Medicine, University of Miami, Miami, Florida, USA.
authors.forename: Sulaiman
authors.initials: S
authors.lastname: Sheriff
authors.affiliation: Department of radiology, Miller School of Medicine, University of Miami, Miami, Florida, USA.|Department of Radiology, University of Calgary, Calgary, AB, Canada.
authors.forename: Mohamad
authors.initials: M
authors.lastname: Sabati
authors.affiliation: CRMBM, Aix-Marseille Université, CNRS 7339, Marseille, France.|APHM, CHU Timone, Pôle d'Imagerie, CEMEREM, Marseille, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Donnadieu
authors.affiliation: CRMBM, Aix-Marseille Université, CNRS 7339, Marseille, France.|APHM, CHU Timone, Pôle d'Imagerie, CEMEREM, Marseille, France.
authors.forename: Sylviane
authors.initials: S
authors.lastname: Confort-Gouny
authors.affiliation: CRMBM, Aix-Marseille Université, CNRS 7339, Marseille, France.|APHM, CHU Timone, Pôle d'Imagerie, CEMEREM, Marseille, France.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Cozzone
authors.affiliation: CRMBM, Aix-Marseille Université, CNRS 7339, Marseille, France.|APHM, CHU Timone, Pôle d'Imagerie, CEMEREM, Marseille, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Guye
authors.affiliation: CRMBM, Aix-Marseille Université, CNRS 7339, Marseille, France.|APHM, CHU Timone, Pôle d'Imagerie, CEMEREM, Marseille, France.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Ranjeva
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D057054:Molecular Imaging / Q000379:methods; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D055815:Young Adult
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate
keywords: MRSI; metabolite maps; proton MR spectroscopy; template; whole brain