title: Imaging the effects of oxygen saturation changes in voluntary apnea and hyperventilation on susceptibility-weighted imaging.
abstract: OBJECTIVE
  Cerebrovascular oxygenation changes during respiratory challenges have clinically important implications for brain function, including cerebral autoregulation and the rate of brain metabolism. SWI is sensitive to venous oxygenation level by exploitation of the magnetic susceptibility of deoxygenated blood. We assessed cerebral venous blood oxygenation changes during simple voluntary breath-holding (apnea) and hyperventilation by use of SWI at 3T.
  
  
  METHODS
  We performed SWI scans (3T; acquisition time of 1 minute, 28 seconds; centered on the anterior commissure and the posterior commissure) on 10 healthy male volunteers during baseline breathing as well as during simple voluntary hyperventilation and apnea challenges. The hyperventilation and apnea tasks were separated by a 5-minute resting period. SWI venograms were generated, and the signal changes on SWI before and after the respiratory stress tasks were compared by means of a paired Student t test.
  
  
  RESULTS
  Changes in venous vasculature visibility caused by the respiratory challenges were directly visualized on the SWI venograms. The venogram segmentation results showed that voluntary apnea decreased the mean venous blood voxel number by 1.6% (P < .0001), and hyperventilation increased the mean venous blood voxel number by 2.7% (P < .0001). These results can be explained by blood CO2 changes secondary to the respiratory challenges, which can alter cerebrovascular tone and cerebral blood flow and ultimately affect venous oxygen levels.
  
  
  CONCLUSIONS
  These results highlight the sensitivity of SWI to simple and noninvasive respiratory challenges and its potential utility in assessing cerebral hemodynamics and vasomotor responses.
authors.affiliation: From the Department of Radiology (K.C., R.I.G., Y.G.), Center for Biomedical Imaging, New York University School of Medicine, New York, New York.
authors.forename: K
authors.initials: K
authors.lastname: Chang
authors.affiliation: Division of Biology (S.B.), Caltech, Pasadena, California.
authors.forename: S
authors.initials: S
authors.lastname: Barnes
authors.affiliation: Department of Radiology (E.M.H.), Wayne State University School of Medicine, Detroit, Michigan.
authors.forename: E M
authors.initials: EM
authors.lastname: Haacke
authors.affiliation: From the Department of Radiology (K.C., R.I.G., Y.G.), Center for Biomedical Imaging, New York University School of Medicine, New York, New York.
authors.forename: R I
authors.initials: RI
authors.lastname: Grossman
authors.affiliation: From the Department of Radiology (K.C., R.I.G., Y.G.), Center for Biomedical Imaging, New York University School of Medicine, New York, New York yulin.ge@nyumc.org.
authors.forename: Y
authors.initials: Y
authors.lastname: Ge
mesh_terms: D000328:Adult; D001049:Apnea / Q000378:metabolism* / Q000473:pathology; D062485:Breath Holding; D002550:Cerebral Veins / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D006985:Hyperventilation / Q000378:metabolism* / Q000473:pathology; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000097:blood*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014836:Volition
chemical_list: D010100:Oxygen