title: Analysing the response in R2* relaxation rate of intracranial tumours to hyperoxic and hypercapnic respiratory challenges: initial results.
abstract: OBJECTIVE
  To investigate the response in R2* relaxation rate of human intracranial tumours during hyperoxic and hypercapnic respiratory challenges.
  
  
  METHODS
  In seven patients with different intracranial tumours, cerebral R2* changes during carbogen and CO(2)/air inhalation were monitored at 3 T using a dynamic multigradient-echo sequence of high temporal and spatial resolution. The R2* time series of each voxel was tested for significant change. Regions of interest were analysed with respect to response amplitude and velocity.
  
  
  RESULTS
  The tumours showed heterogeneous R2* responses with large interindividual variability. In the 'contrast-enhancing' area of five patients and in the 'non-tumoral' tissue most voxels showed a decrease in R2* for carbogen. For the 'contrast-enhancing' area of two patients hardly any responses were found. In areas of 'necrosis' and perifocal 'oedema' typically voxels with R2* increase and no response were found for both gases. For tissue responding to CO(2)/air, the R2* changes were of the same order of magnitude as those for carbogen. The response kinetic was generally attenuated in tumoral tissue.
  
  
  CONCLUSIONS
  The spatially resolved determination of R2* changes reveals the individual heterogeneous response characteristic of intracranial human tumours during hyperoxic and hypercapnic respiratory challenges.
authors.affiliation: Department of Radiology, University of Bonn, Sigmund-Freud-Straße 25, 53105 Bonn, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Müller
authors.forename: S
authors.initials: S
authors.lastname: Remmele
authors.forename: I
authors.initials: I
authors.lastname: Wenningmann
authors.forename: H
authors.initials: H
authors.lastname: Clusmann
authors.forename: F
authors.initials: F
authors.lastname: Träber
authors.forename: S
authors.initials: S
authors.lastname: Flacke
authors.forename: R
authors.initials: R
authors.lastname: König
authors.forename: J
authors.initials: J
authors.lastname: Gieseke
authors.forename: W A
authors.initials: WA
authors.lastname: Willinek
authors.forename: H H
authors.initials: HH
authors.lastname: Schild
authors.forename: P
authors.initials: P
authors.lastname: Mürtz
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001932:Brain Neoplasms / Q000473:pathology*; D002245:Carbon Dioxide / Q000737:chemistry; D005260:Female; D006801:Humans; D006935:Hypercapnia; D018496:Hyperoxia; D007700:Kinetics; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000737:chemistry; D012119:Respiration; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; C011700:carbogen; D010100:Oxygen