title: R1 and R2 * changes in the human placenta in response to maternal oxygen challenge.
abstract: OBJECTIVE
  Pregnancy complications such as preeclampsia and fetal growth restriction are sometimes thought to be caused by placental abnormalities associated with reduced oxygenation. Oxygen-enhanced MRI (R1 contrast) and BOLD MRI (R2 * contrast) have the potential to noninvasively investigate this oxygen environment at a range of gestational ages.
  
  
  METHODS
  Scanning was carried out at 1.5 T under maternal air and oxygen breathing in a single placental slice in 14 healthy pregnant subjects of gestational ages 21-37 weeks. We report R1 changes using a respiratory-triggered inversion recovery-turbo spin-echo sequence, which is sensitive to changes in PO2 , and R2 * changes using a breathhold multiple gradient-recalled echo sequence sensitive to changes in oxygen saturation.
  
  
  RESULTS
  Significant R1 increases (P < 0.005, paired t-test) and R2 * decreases (P < 0.0001, paired t-test) between air and oxygen breathing were demonstrated. ΔR1 decreased with gestational age (P < 0.0005, r = -0.835, Pearson correlation test). No significant effect of gestational age on R2 * change was observed.
  
  
  CONCLUSIONS
  The results demonstrate the feasibility of non-invasive investigation of placental oxygenation using MRI and the sensitivity of R1 oxygen-enhanced MRI to gestational age. The techniques have the potential to provide unique noninvasive biomarkers in compromised pregnancies.
authors.affiliation: Centre for Imaging Sciences, Faculty of Medical and Human Sciences, University of Manchester, Manchester, UK; The University of Manchester Biomedical Imaging Institute, University of Manchester, Manchester, UK.
authors.forename: Isaac
authors.initials: I
authors.lastname: Huen
authors.forename: David M
authors.initials: DM
authors.lastname: Morris
authors.forename: Caroline
authors.initials: C
authors.lastname: Wright
authors.forename: Geoff J M
authors.initials: GJ
authors.lastname: Parker
authors.forename: Colin P
authors.initials: CP
authors.lastname: Sibley
authors.forename: Edward D
authors.initials: ED
authors.lastname: Johnstone
authors.forename: Josephine H
authors.initials: JH
authors.lastname: Naish
mesh_terms: D000280:Administration, Inhalation; D015415:Biomarkers / Q000378:metabolism; D003287:Contrast Media / Q000008:administration & dosage / Q000493:pharmacokinetics; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000008:administration & dosage / Q000493:pharmacokinetics*; D010920:Placenta / Q000033:anatomy & histology / Q000378:metabolism*; D011247:Pregnancy / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D003287:Contrast Media; D010100:Oxygen
keywords: biomarker; effective transverse relaxation rate; longitudinal relaxation rate; oxygen; placenta; pregnancy