title: Intracranial tumor response to respiratory challenges at 3.0 T: impact of different methods to quantify changes in the MR relaxation rate R2*.
abstract: OBJECTIVE
  To compare two DeltaR2* quantification methods for analyzing the response of intracranial tumors to different breathing gases. The determination of changes in the magnetic resonance imaging (MRI) relaxation rate R2* (DeltaR2*), induced by hyperoxic and hypercapnic respiratory challenges, enables the noninvasive assessment of blood oxygenation changes and vasoreactivity.
  
  
  METHODS
  Sixteen patients with various intracranial tumors were examined at 3.0 T. The response to respiratory challenges was registered using a dynamic multigradient-echo sequence with high temporal and spatial resolution. At each dynamic step, DeltaR2* was derived in two different ways: 1) by subtraction of R2* values obtained from monoexponential decay functions, 2) by computing DeltaR2* echo-wise from signal intensity ratios. The sensitivity for detection of responding voxels and the behavior of the "global" response were investigated.
  
  
  RESULTS
  Significantly more responding voxels (about 4%) were found for method (1). The "global" response was independent from the chosen quantification method but showed slightly larger changes (about 6%) when DeltaR2* was derived from method (1).
  
  
  CONCLUSIONS
  Similar results were observed for the two methods, with a slightly higher detection sensitivity of responding voxels when DeltaR2* was obtained from monoexponential approximation.
authors.affiliation: Department of Radiology, University of Bonn, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Müller
authors.forename: Stefanie
authors.initials: S
authors.lastname: Remmele
authors.forename: Ingobert
authors.initials: I
authors.lastname: Wenningmann
authors.forename: Hans
authors.initials: H
authors.lastname: Clusmann
authors.forename: Frank
authors.initials: F
authors.lastname: Träber
authors.forename: Sebastian
authors.initials: S
authors.lastname: Flacke
authors.forename: Roy
authors.initials: R
authors.lastname: König
authors.forename: Jürgen
authors.initials: J
authors.lastname: Gieseke
authors.forename: Winfried A
authors.initials: WA
authors.lastname: Willinek
authors.forename: Hans H
authors.initials: HH
authors.lastname: Schild
authors.forename: Petra
authors.initials: P
authors.lastname: Mürtz
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000378:metabolism / Q000473:pathology; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000556:secondary; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000378:metabolism; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D006935:Hypercapnia / Q000378:metabolism*; D018496:Hyperoxia / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008228:Lymphoma, Non-Hodgkin / Q000378:metabolism / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008579:Meningioma / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage / Q000378:metabolism; D012119:Respiration; D012680:Sensitivity and Specificity
chemical_list: D002245:Carbon Dioxide; C011700:carbogen; D010100:Oxygen