title: Effect of Carr-Purcell refocusing pulse trains on transverse relaxation times of metabolites in rat brain at 9.4 Tesla.
abstract: OBJECTIVE
  To investigate the effect of Carr-Purcell (CP) pulse trains on transverse relaxation times, T2, of tissue water and metabolites (both noncoupled and J-coupled spins) in the rat brain at 9.4 Tesla (T) using LASER, CP-LASER, and T2ρ-LASER sequences.
  
  
  METHODS
  Proton NMR spectra were measured in rat brain in vivo at 9.4T. Spectra were acquired at multiple echo times ranging from 18 to 402 ms. All spectra were analyzed using LCModel with simulated basis sets. Signals of metabolites as a function of echo time were fitted using a mono-exponential function to determine their T2 relaxation times.
  
  
  RESULTS
  Measured T2 s for tissue water and all metabolites were significantly longer with CP-LASER and T2ρ-LASER compared with LASER. The T2 increased by a factor of ∼ 1.3 for noncoupled and weakly coupled spins (e.g., N-acetylaspartate and total creatine) and by a factor of ∼ 2 (e.g., glutamine and taurine) to ∼ 4 (e.g., glutamate and myo-inositol) for strongly coupled spins.
  
  
  CONCLUSIONS
  Application of a CP pulse train results in a larger increase in T2 relaxation times for strongly coupled spins than for noncoupled (singlet) and weakly coupled spins. This needs to be taken into account when correcting for T2 relaxation in CP-like sequences such as LASER.
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Dinesh Kumar
authors.initials: DK
authors.lastname: Deelchand
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Pierre-Gilles
authors.initials: PG
authors.lastname: Henry
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Marjańska
mesh_terms: D000465:Algorithms; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D057054:Molecular Imaging / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D014018:Tissue Distribution
keywords: CP pulse train; LASER; LCModel; T2; brain