title: Intraindividual variability of striatal (1)H-MRS brain metabolite measurements at 3 T.
abstract: OBJECTIVE
  To measure possible positional and diurnal physiological effects on brain metabolites in single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) measurements of the right and left striatum.
  
  
  METHODS
  (1)H-MRS measurements were performed in 10 healthy adult volunteers using a short echo PRESS sequence (TE=30 ms, TR=3000 ms). Each individual was scanned during both morning and afternoon hours. Regions of interest were right and left striatum. To control for systematic drift in scanner performance, (1)H-MRS measurements of a standard phantom solution were also acquired. Statistical analysis was performed using a repeated measures analysis of variance that included three within-subject factors: metabolite (N-acetyl-aspartate [NAA] or creatine [Cr]), laterality (left or right caudate) and time (morning or afternoon).
  
  
  RESULTS
  A significant interaction (P<.016) between time of day and metabolite levels was observed. Further exploration of this finding revealed a significant difference between morning and afternoon levels of NAA (P<.044) but not Cr. In addition, no significant morning-to-afternoon differences were observed for the (1)H-MRS phantom measurements.
  
  
  CONCLUSIONS
  Systematic variation due to scanner performance does not account for the changes observed in repeated measurements of striatal NAA levels. This difference may be accounted for by either repositioning effects or circadian physiological effects. Further studies are required to learn whether time of day standardization of (1)H-MRS acquisitions may contribute to improved reproducibility of measurements.
authors.affiliation: Psychiatry Research Unit, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.
authors.forename: Noam
authors.initials: N
authors.lastname: Soreni
authors.forename: Michael D
authors.initials: MD
authors.lastname: Noseworthy
authors.forename: Toni
authors.initials: T
authors.lastname: Cormier
authors.forename: Wendy K
authors.initials: WK
authors.lastname: Oakden
authors.forename: Sonya
authors.initials: S
authors.lastname: Bells
authors.forename: Russell
authors.initials: R
authors.lastname: Schachar
mesh_terms: D000704:Analysis of Variance; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D003287:Contrast Media; D003401:Creatine / Q000378:metabolism*; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D015203:Reproducibility of Results
chemical_list: D003287:Contrast Media; D001224:Aspartic Acid; C000179:N-acetylaspartate; D019786:Gadolinium DTPA; D003401:Creatine