title: Proton spectroscopic imaging of brain metabolites in basal ganglia of healthy older adults.
abstract: OBJECTIVE
  We sought to measure brain metabolite levels in healthy older people.
  
  
  METHODS
  Spectroscopic imaging at the level of the basal ganglia was applied in 40 participants aged 73-74 years. Levels of the metabolites N-acetyl aspartate (NAA), choline, and creatine were determined in "institutional units" (IU) corrected for T1 and T2 relaxation effects. Structural imaging enabled determination of grey matter (GM), white matter (WM), and cerebrospinal fluid content. ANOVA analysis was carried out for voxels satisfying quality criteria.
  
  
  RESULTS
  Creatine levels were greater in GM than WM (57 vs. 44 IU, p < 0.001), whereas choline and NAA levels were greater in WM than GM [13 vs. 10 IU (p < 0.001) and 76 versus 70 IU (p = 0.03), respectively]. The ratio of NAA/cre was greater in WM than GM (2.1 vs. 1.4, p = 0.001) as was that of cho/cre (0.32 vs. 0.16, p < 0.001). A low voxel yield was due to brain atrophy and the difficulties of shimming over an extended region of brain.
  
  
  CONCLUSIONS
  This study addresses the current lack of information on brain metabolite levels in older adults. The normal features of ageing result in a substantial loss of reliable voxels and should be taken into account when planning studies. Improvements in shimming are also required before the methods can be applied more widely.
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Chancellor's Building, Edinburgh, EH16 4SB, UK.
authors.forename: Jehill
authors.initials: J
authors.lastname: Parikh
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Thrippleton
authors.forename: Catherine
authors.initials: C
authors.lastname: Murray
authors.forename: Paul A
authors.initials: PA
authors.lastname: Armitage
authors.forename: Bridget A
authors.initials: BA
authors.lastname: Harris
authors.forename: Peter J D
authors.initials: PJ
authors.lastname: Andrews
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Wardlaw
authors.forename: John M
authors.initials: JM
authors.lastname: Starr
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Deary
authors.forename: Ian
authors.initials: I
authors.lastname: Marshall
mesh_terms: D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001479:Basal Ganglia / Q000033:anatomy & histology / Q000378:metabolism*; D002794:Choline / Q000378:metabolism*; D003401:Creatine / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / 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
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline