title: Noninvasive oxygen partial pressure measurement of human body fluids in vivo using magnetic resonance imaging.
abstract: OBJECTIVE
  The oxygen partial pressure (pO2) of human body fluids reflects the oxygenation status of surrounding tissues. All existing fluid pO2 measurements are invasive, requiring either microelectrode/optode placement or fluid removal. The purpose of this study is to develop a noninvasive magnetic resonance imaging method to measure the pO2 of human body fluids.
  
  
  METHODS
  We developed an imaging paradigm that exploits the paramagnetism of molecular oxygen to create quantitative images of fluid oxygenation. A single-shot fast spin echo pulse sequence was modified to minimize artifacts from motion, fluid flow, and partial volume. Longitudinal relaxation rate (R1 = 1/T1) was measured with a time-efficient nonequilibrium saturation recovery method and correlated with pO2 measured in phantoms.
  
  
  RESULTS
  pO2 images of human and fetal cerebrospinal fluid, bladder urine, and vitreous humor are presented and quantitative oxygenation levels are compared with prior literature estimates, where available. Significant pO2 increases are shown in cerebrospinal fluid and vitreous following 100% oxygen inhalation. Potential errors due to temperature, fluid flow, and partial volume are discussed.
  
  
  CONCLUSIONS
  Noninvasive measurements of human body fluid pO2 in vivo are presented, which yield reasonable values based on prior literature estimates. This rapid imaging-based measurement of fluid oxygenation may provide insight into normal physiology as well as changes due to disease or during treatment.
authors.affiliation: University of California, San Francisco, 505 Parnassus Avenue, San Francisco, California 94143-0628, USA. Greg.Zaharchuk@radiology.ucsf.edu
authors.forename: Greg
authors.initials: G
authors.lastname: Zaharchuk
authors.forename: Reed F
authors.initials: RF
authors.lastname: Busse
authors.forename: Guy
authors.initials: G
authors.lastname: Rosenthal
authors.forename: Geoffery T
authors.initials: GT
authors.lastname: Manley
authors.forename: Orit A
authors.initials: OA
authors.lastname: Glenn
authors.forename: William P
authors.initials: WP
authors.lastname: Dillon
mesh_terms: D000328:Adult; D001826:Body Fluids / Q000378:metabolism*; D002555:Cerebrospinal Fluid / Q000378:metabolism; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010313:Partial Pressure; D019047:Phantoms, Imaging; D011247:Pregnancy; D001743:Urinary Bladder / Q000378:metabolism; D014822:Vitreous Body / Q000378:metabolism
chemical_list: D010100:Oxygen