title: Estimation of metabolite T1 relaxation times using tissue specific analysis, signal averaging and bootstrapping from magnetic resonance spectroscopic imaging data.
abstract: OBJECTIVE
  A novel method of estimating metabolite T1 relaxation times using MR spectroscopic imaging (MRSI) is proposed. As opposed to conventional single-voxel metabolite T1 estimation methods, this method investigates regional and gray matter (GM)/white matter (WM) differences in metabolite T1 by taking advantage of the spatial distribution information provided by MRSI.
  
  
  METHODS
  The method, validated by Monte Carlo studies, involves a voxel averaging to preserve the GM/WM distribution, a non-linear least squares fit of the metabolite T1 and an estimation of its standard error by bootstrapping. It was applied in vivo to estimate the T1 of N-acetyl compounds (NAA), choline, creatine and myo-inositol in eight normal volunteers, at 1.5 T, using a short echo time 2D-MRSI slice located above the ventricles.
  
  
  RESULTS
  WM-T 1,NAA was significantly (P < 0.05) longer in anterior regions compared to posterior regions of the brain. The anterior region showed a trend of a longer WM T1 compared to GM for NAA, creatine and myo-Inositol. Lastly, accounting for the bootstrapped standard error estimate in a group mean T1 calculation yielded a more accurate T1 estimation.
  
  
  CONCLUSIONS
  The method successfully measured in vivo metabolite T1 using MRSI and can now be applied to diseased brain.
authors.affiliation: Department of Neurology, University of California, 185 Berry Street, Box 0946, San Francisco, CA 94107, USA.
authors.forename: H
authors.initials: H
authors.lastname: Ratiney
authors.forename: S M
authors.initials: SM
authors.lastname: Noworolski
authors.forename: M
authors.initials: M
authors.lastname: Sdika
authors.forename: R
authors.initials: R
authors.lastname: Srinivasan
authors.forename: R G
authors.initials: RG
authors.lastname: Henry
authors.forename: S J
authors.initials: SJ
authors.lastname: Nelson
authors.forename: D
authors.initials: D
authors.lastname: Pelletier
mesh_terms: D000328:Adult; D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D012815:Signal Processing, Computer-Assisted; D014018:Tissue Distribution
chemical_list: D009419:Nerve Tissue Proteins