title: In vivo chlorine and sodium MRI of rat brain at 21.1 T.
abstract: OBJECTIVE
  MR imaging of low-gamma nuclei at the ultrahigh magnetic field of 21.1 T provides a new opportunity for understanding a variety of biological processes. Among these, chlorine and sodium are attracting attention for their involvement in brain function and cancer development.
  
  
  METHODS
  MRI of (35)Cl and (23)Na were performed and relaxation times were measured in vivo in normal rat (n = 3) and in rat with glioma (n = 3) at 21.1 T. The concentrations of both nuclei were evaluated using the center-out back-projection method.
  
  
  RESULTS
  T 1 relaxation curve of chlorine in normal rat head was fitted by bi-exponential function (T 1a = 4.8 ms (0.7) T 1b = 24.4 ± 7 ms (0.3) and compared with sodium (T 1 = 41.4 ms). Free induction decays (FID) of chlorine and sodium in vivo were bi-exponential with similar rapidly decaying components of [Formula: see text] ms and [Formula: see text] ms, respectively. Effects of small acquisition matrix and bi-exponential FIDs were assessed for quantification of chlorine (33.2 mM) and sodium (44.4 mM) in rat brain.
  
  
  CONCLUSIONS
  The study modeled a dramatic effect of the bi-exponential decay on MRI results. The revealed increased chlorine concentration in glioma (~1.5 times) relative to a normal brain correlates with the hypothesis asserting the importance of chlorine for tumor progression.
authors.affiliation: National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, FL, 32310-4005, USA, schepkin@magnet.fsu.edu.
authors.forename: Victor D
authors.initials: VD
authors.lastname: Schepkin
authors.forename: Malathy
authors.initials: M
authors.lastname: Elumalai
authors.forename: Jason A
authors.initials: JA
authors.lastname: Kitchen
authors.forename: Chunqi
authors.initials: C
authors.lastname: Qian
authors.forename: Peter L
authors.initials: PL
authors.lastname: Gor'kov
authors.forename: William W
authors.initials: WW
authors.lastname: Brey
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000473:pathology*; D002713:Chlorine / Q000737:chemistry*; D018450:Disease Progression; D004867:Equipment Design; D005910:Glioma / Q000473:pathology*; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051381:Rats; D012964:Sodium / Q000737:chemistry*
chemical_list: D002713:Chlorine; D012964:Sodium