title: (17)O relaxation times in the rat brain at 16.4 tesla.
abstract: OBJECTIVE
  Measurement of the cerebral metabolic rate of oxygen (CMRO2 ) by means of direct imaging of the (17) O signal can be a valuable tool in neuroscientific research. However, knowledge of the longitudinal and transverse relaxation times of different brain tissue types is required, which is difficult to obtain because of the low sensitivity of natural abundance H2 (17) O measurements.
  
  
  METHODS
  Using the improved sensitivity at a field strength of 16.4 Tesla, relaxation time measurements in the rat brain were performed in vivo and postmortem with relatively high spatial resolutions, using a chemical shift imaging sequence.
  
  
  RESULTS
  In vivo relaxation times of rat brain were found to be T1 = 6.84 ± 0.67 ms and T2 * = 1.77 ± 0.04 ms. Postmortem H2 (17) O relaxometry at enriched concentrations after inhalation of (17) O2 showed similar T2 * values for gray matter (1.87 ± 0.04 ms) and white matter, significantly longer than muscle (1.27 ± 0.05 ms) and shorter than cerebrospinal fluid (2.30 ± 0.16 ms).
  
  
  CONCLUSIONS
  Relaxation times of brain H2 (17) O were measured for the first time in vivo in different types of tissues with high spatial resolution. Because the relaxation times of H2 (17) O are expected to be independent of field strength, our results should help in optimizing the acquisition parameters for experiments also at other MRI field strengths.
authors.affiliation: High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.|Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Hannes M
authors.initials: HM
authors.lastname: Wiesner
authors.affiliation: High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Dávid Z
authors.initials: DZ
authors.lastname: Balla
authors.affiliation: High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Shajan
authors.affiliation: High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.|Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Kâmil
authors.initials: K
authors.lastname: Uğurbil
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.affiliation: Maastricht Brain Imaging Center (M-BIC), Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands.
authors.forename: Kâmil
authors.initials: K
authors.lastname: Uludağ
authors.affiliation: High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Pohmann
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D005740:Gases; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging; D008297:Male; D010103:Oxygen Isotopes / Q000737:chemistry*; D019047:Phantoms, Imaging; D011522:Protons; D051381:Rats; D017208:Rats, Wistar; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D005740:Gases; D010103:Oxygen Isotopes; D011522:Protons; D014867:Water
keywords: H217O; MRSI; X-Nuclei; brain water distribution; natural abundance oxygen-17; quadrupolar relaxation; quantification; relaxation times; spectroscopic imaging; ultra-high field