title: Cerebrospinal fluid signal intensity increase on FLAIR MR images in patients under general anesthesia: the role of supplemental O2.
abstract: OBJECTIVE
  To determine whether increased cerebrospinal fluid (CSF) signal intensity is seen on fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images in patients under general anesthesia and to investigate the cause of these changes.
  
  
  METHODS
  MR images from nine examinations performed in eight patients under general anesthesia were reviewed retrospectively. In phantom experiments, T1 measurements obtained with several inhaled anesthetic agents and propofol dissolved in saline were compared with those obtained with either 100% O2 or room air. To confirm phantom experiment results, a healthy volunteer underwent sequential FLAIR imaging while breathing high-flow 100% O2.
  
  
  RESULTS
  Of the nine examinations performed with patients under general anesthesia, eight had resultant images that showed increased CSF signal intensity within the basal cisterns and sulci over the cerebral convexities. Anesthetic phantom measurements showed T1 shortening only when the agent was administered with high concentrations of oxygen. In the healthy volunteer, images obtained before and during administration of 100% O2 demonstrated increased CSF signal intensity after O2 administration; this was identical to the changes observed in patients under anesthesia.
  
  
  CONCLUSIONS
  The paramagnetic effects of supplemental O2 administration result in shortened CSF T1. Radiologists should be aware of this phenomenon to avoid attributing increased CSF signal intensity on FLAIR images to abnormal CSF properties such as hemorrhage or elevated protein content.
authors.affiliation: Department of Radiology, University of Washington, Box 357115, 1959 NE Pacific St, Seattle, WA 98195-7115, USA.
authors.forename: A V
authors.initials: AV
authors.lastname: Deliganis
authors.forename: D J
authors.initials: DJ
authors.lastname: Fisher
authors.forename: A M
authors.initials: AM
authors.lastname: Lam
authors.forename: K R
authors.initials: KR
authors.lastname: Maravilla
mesh_terms: D000293:Adolescent; D000328:Adult; D000768:Anesthesia, General; D002555:Cerebrospinal Fluid; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage*; D019047:Phantoms, Imaging; D012189:Retrospective Studies
chemical_list: D010100:Oxygen