title: Relaxation and exchange dynamics of hyperpolarized 129Xe in human blood.
abstract: OBJECTIVE
  (129) Xe-blood NMR was performed over the full blood oxygenation range to evaluate (129) Xe relaxation and exchange dynamics in human blood.
  
  
  METHODS
  Hyperpolarized (129) Xe was equilibrated with blood and isolated plasma, and NMR was performed at 1.5 T.
  
  
  RESULTS
  The (129) Xe relaxation rate was found to increase nonlinearly with decreasing blood oxygenation. Three constants were extrapolated: rsO2 =  11.1, a "relaxivity index" characterizing the rate of change of (129) Xe relaxation as a function of blood oxygenation, and 1/T1oHb  =  0.13 s(-1) and 1/T1dHb = 0.42 s(-1) , the (129) Xe relaxation rates in oxygenated blood and deoxygenated blood, respectively. In addition, rate constants, ka =  0.022 ms(-1) and kb =  0.062 ms(-1) , were determined for xenon diffusing between red blood cells (RBCs) and plasma (hematocrit  =  48%). The (129) Xe-O2 relaxivity in plasma, rO2 = 0.075 s(-1) mM(-1) , and the (129) Xe relaxation rate in isolated plasma (without dissolved O2 ), 1/T1,b0 = 0.046 s(-1) , were also calculated. Finally, intrinsic (129) Xe-RBC relaxation rates, 1/T1,aoHb = 0.19 s(-1) and 1/T1,adHb = 0.84 s(-1) , in oxygenated blood and deoxygenated blood, respectively, were calculated.
  
  
  CONCLUSIONS
  The relaxation and exchange analysis performed in this study should provide a sound experimental basis upon which to design future MR experiments for dissolved xenon transport from the lungs to distal tissues.
authors.affiliation: Unit of Academic Radiology, Department of Cardiovascular Science, University of Sheffield, Sheffield, South Yorkshire, UK.
authors.forename: Graham
authors.initials: G
authors.lastname: Norquay
authors.affiliation: Unit of Academic Radiology, Department of Cardiovascular Science, University of Sheffield, Sheffield, South Yorkshire, UK.
authors.forename: General
authors.initials: G
authors.lastname: Leung
authors.affiliation: Unit of Academic Radiology, Department of Cardiovascular Science, University of Sheffield, Sheffield, South Yorkshire, UK.
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Stewart
authors.affiliation: Department of Oncology, University of Sheffield, Sheffield, South Yorkshire, UK.
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Tozer
authors.affiliation: Unit of Academic Radiology, Department of Cardiovascular Science, University of Sheffield, Sheffield, South Yorkshire, UK.|GE Healthcare, Amersham, Buckinghamshire, UK.
authors.forename: Jan
authors.initials: J
authors.lastname: Wolber
authors.affiliation: Unit of Academic Radiology, Department of Cardiovascular Science, University of Sheffield, Sheffield, South Yorkshire, UK.
authors.forename: Jim M
authors.initials: JM
authors.lastname: Wild
mesh_terms: D000327:Adsorption; D001774:Blood Chemical Analysis / Q000379:methods*; D003198:Computer Simulation; D003287:Contrast Media / Q000737:chemistry; D004058:Diffusion; D004912:Erythrocytes / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D008279:Magnetic Resonance Imaging; D008954:Models, Biological; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D010949:Plasma / Q000737:chemistry*; D019275:Radiopharmaceuticals / Q000737:chemistry; D014979:Xenon Isotopes / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D014979:Xenon Isotopes; D010100:Oxygen
keywords: 129Xe spectroscopy; T1 relaxation; blood; chemical exchange; hyperpolarized gases