title: BOLD MRI in the brain of fetal sheep at 3T during experimental hypoxia.
abstract: OBJECTIVE
  To calculate regional fetal brain oxygen saturation (sO2) during hypoxia in sheep.
  
  
  METHODS
  Eight pregnant ewes were examined at a 3T MR-scanner using blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) to measure signal intensity changes of the fetal brain during a control period and a period of induced hypoxia. Regions of interest were placed in the fetal cerebrum to assess ΔR2* from GRE signal intensity plateaus (S(control), S(hypoxia)) and the relation between ΔR2* and ΔpO2 was analyzed. A probe was placed surgically in the fetal brain to directly measure local pO2 as a reference standard. Baseline and hypoxic pO2 values were recorded and compared (ΔpO2).
  
  
  RESULTS
  Mean fetal brain pO2 decreased from 14.3 mmHg (95% confidence interval [CI]: 10-19) to 3.4 mmHg (95% CI: 2-5) during hypoxia (mean ΔpO2 = 10.9 mmHg and ΔR2* = -5s(-1)). A significant correlation between ΔR2* and ΔpO2 was noted (r = 0.93, P < 0.001), and conversion of pO2 into sO2 resulted in a linear regression coefficient of (-0.14 ± 0.01)s(-1)/% (r(2) = 0.91).
  
  
  CONCLUSIONS
  Measured fetal brain BOLD-MRI was compared and converted to pO2, followed by calculation of cerebral sO2.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Medical Center, Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Bjoern P
authors.initials: BP
authors.lastname: Schoennagel
authors.forename: Jin
authors.initials: J
authors.lastname: Yamamura
authors.forename: Roland
authors.initials: R
authors.lastname: Fischer
authors.forename: Manuela
authors.initials: M
authors.lastname: Tavares de Sousa
authors.forename: Marcela
authors.initials: M
authors.lastname: Weyhmiller
authors.forename: Moritz
authors.initials: M
authors.lastname: Birkelbach
authors.forename: Hendrik
authors.initials: H
authors.lastname: Kooijman
authors.forename: Gerhard
authors.initials: G
authors.lastname: Adam
authors.forename: Ulrike
authors.initials: U
authors.lastname: Wedegaertner
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology*; D005260:Female; D005311:Fetal Hypoxia / Q000473:pathology*; D005333:Fetus; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011247:Pregnancy
keywords: BOLD; MRI; brain; fetal sheep; hypoxia; oxygenation