title: The effect of dissolved oxygen on the susceptibility of blood.
abstract: OBJECTIVE
  It has been predicted that, during hyperoxia, excess O2 dissolved in arterial blood will significantly alter the blood's magnetic susceptibility. This would confound the interpretation of the hyperoxia-induced blood oxygenation level-dependent signal as arising solely from changes in deoxyhemoglobin. This study, therefore, aimed to determine how dissolved O2 affects the susceptibility of blood.
  
  
  METHODS
  We present a comprehensive model for the effect of dissolved O2 on the susceptibility of blood and compare it with another recently published model, referred to here as the ideal gas model (IGM). For validation, distilled water and samples of bovine plasma were oxygenated over a range of hyperoxic O2 concentrations and their susceptibilities were determined using multiecho gradient echo phase imaging.
  
  
  RESULTS
  In distilled water and plasma, the measured changes in susceptibility were very linear, with identical slopes of 0.062 ppb/mm Hg of O2. This change was dramatically less than previously predicted using the IGM and was close to that predicted by our model. The primary source of error in the IGM is the overestimation of the volume fraction occupied by dissolved O2.
  
  
  CONCLUSIONS
  Under most physiological conditions, the susceptibility of dissolved O2 can be disregarded in MRI studies employing hyperoxia.
authors.affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.|Department of Radiology and Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Avery J L
authors.initials: AJ
authors.lastname: Berman
authors.affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
authors.forename: Yuhan
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Institut de génie biomédical, Département de physiologie, Université de Montréal, Montréal, Québec, Canada.|Unité de neuroimagerie fonctionelle, Centre de recherche de l'institut de gériatrie de Montréal, Montreal, Quebec, Canada.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Hoge
authors.affiliation: Department of Radiology and Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Pike
mesh_terms: D000818:Animals; D001774:Blood Chemical Analysis; D002417:Cattle; D003198:Computer Simulation; D017097:Electric Impedance; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008422:Materials Testing; D008955:Models, Cardiovascular; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D010949:Plasma / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D010100:Oxygen
keywords: BOLD; blood; dissolved O2; hyperoxia; susceptibility