title: Comparing oxygen-sensitive MRI (BOLD R2*) with oxygen electrode measurements: a pilot study in men with prostate cancer.
abstract: OBJECTIVE
  To explore the relationship between oxygen-sensitive Magnetic Resonance Imaging (MRI) and oxygen measurements in prostate cancer.
  
  
  METHODS
  Nine men underwent MRI examinations followed by needle oxygen measurements of tumor bearing region within prostate gland and five men further consented to biopsy. Median pO2 and hypoxic fraction < 5 mm Hg (HP5) were derived. Biopsies were immunostained for Carbonic Anhydrase IX (CA IX), Hypoxia Inducible Factor-1 (HIF 1) and Glucose Transporter-1 (GLUT 1). Corresponding Regions-of-Interest (ROI) were delineated on T2-weighted (T2w) MRI by two observers. Median R2* was calculated for each ROI. Spearman correlation was calculated between R2* and HP5/pO2.
  
  
  RESULTS
  MRI quality evaluation resulted in exclusion of 4/18 ROI due to motion (n = 2) and rectal air susceptibility artifact (n = 2). Quality of remaining data was validated by concordance of R2* with T2w, indices and with secondary observer R2* (r = 0.94, p = 0.005). Correlation was observed between R2* and HP5 (r = 0.76, p = 0.02) and a trend was noted between R2* and pO2 (r = -0.66, p = 0.07). GLUT 1 and HIF 1 were expressed in all patients, and CA IX was expressed in one patient with high HP5 (77%) and low pO2 (1.4 mm Hg).
  
  
  CONCLUSIONS
  MRI using R2* quantification is a promising tool for non-invasive imaging of prostate cancer hypoxia.
authors.affiliation: Department of Radiation Oncology, University Health Network, Princess Margaret Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Supriya
authors.initials: S
authors.lastname: Chopra
authors.forename: Warren D
authors.initials: WD
authors.lastname: Foltz
authors.forename: Michael F
authors.initials: MF
authors.lastname: Milosevic
authors.forename: Ants
authors.initials: A
authors.lastname: Toi
authors.forename: Robert G
authors.initials: RG
authors.lastname: Bristow
authors.forename: Cynthia
authors.initials: C
authors.lastname: Ménard
authors.forename: Masoom A
authors.initials: MA
authors.lastname: Haider
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D001706:Biopsy; D015687:Cell Hypoxia; D015331:Cohort Studies; D004566:Electrodes; D006801:Humans; D007120:Immunochemistry; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010865:Pilot Projects; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D011786:Quality Control; D015203:Reproducibility of Results; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; D010100:Oxygen