title: Hyperpolarized (3) He and (129) Xe MRI: differences in asthma before bronchodilation.
abstract: OBJECTIVE
  To compare hyperpolarized helium-3 ((3) He) and xenon-129 ((129) Xe) MRI in asthmatics before and after salbutamol inhalation.
  
  
  METHODS
  Seven asthmatics provided written informed consent and underwent spirometry, plethysmography, and MRI before and after salbutamol inhalation. (3) He and (129) Xe ventilation defect percent (VDP) and ventilation coefficient of variation (COV) were measured. To characterize the airways spatially related to ventilation defects, wall area percent (WA%) and lumen area (LA) were evaluated for two subjects who had thoracic x-ray computed tomography (CT) acquired 1 year before MRI.
  
  
  RESULTS
  Before salbutamol inhalation, (129) Xe VDP (8 ± 5%) was significantly greater than (3) He VDP (6 ± 5%, P = 0.003). Post-salbutamol, there was a significant improvement in both (129) Xe (5 ± 4%, P < 0.0001) and (3) He (4 ± 3%, P = 0.001) VDP, and the improvement in (129) Xe VDP was significantly greater (P = 0.008). (129) Xe MRI COV (Pre: 0.309 ± 0.028, Post: 0.296 ± 0.036) was significantly greater than (3) He MRI COV (Pre: 0.282 ± 0.018, Post: 0.269 ± 0.024), pre- (P < 0.0001) and post-salbutamol (P < 0.0001) and the decrease in COV post-salbutamol was significant ((129) Xe, P = 0.002; (3) He, P < 0.0001). For a single asthmatic, a sub-segmental (129) Xe MRI ventilation defect that was visible only before salbutamol inhalation but not visible using (3) He MRI was spatially related to a remodeled fourth generation sub-segmental airway (WA% = 78%, LA = 2.9 mm(2) ).
  
  
  CONCLUSIONS
  In asthma, hyperpolarized (129) Xe MRI may help reveal ventilation abnormalities before bronchodilation that are not observed using hyperpolarized (3) He MRI.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, Canada; Department of Medical Biophysics, The University of Western Ontario, London, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Svenningsen
authors.forename: Miranda
authors.initials: M
authors.lastname: Kirby
authors.forename: Danielle
authors.initials: D
authors.lastname: Starr
authors.forename: Del
authors.initials: D
authors.lastname: Leary
authors.forename: Andrew
authors.initials: A
authors.lastname: Wheatley
authors.forename: Geoffrey N
authors.initials: GN
authors.lastname: Maksym
authors.forename: David G
authors.initials: DG
authors.lastname: McCormack
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000420:Albuterol / Q000008:administration & dosage*; D001249:Asthma / Q000188:drug therapy* / Q000473:pathology*; D001993:Bronchodilator Agents / Q000008:administration & dosage; D003287:Contrast Media; D005260:Female; D006371:Helium; D006801:Humans; D007554:Isotopes; D008168:Lung / Q000187:drug effects / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D014979:Xenon Isotopes; D055815:Young Adult
chemical_list: D001993:Bronchodilator Agents; D003287:Contrast Media; D007554:Isotopes; D019275:Radiopharmaceuticals; D014979:Xenon Isotopes; D006371:Helium; D000420:Albuterol
keywords: airway obstruction; bronchodilator; functional imaging; gas distribution; ventilation defect