title: The variability of regional airflow obstruction within the lungs of patients with asthma: assessment with hyperpolarized helium-3 magnetic resonance imaging.
abstract: BACKGROUND
  It is unknown whether focal changes of airflow obstruction within the lungs of patients with asthma vary or are fixed in location with time or repeated bronchoconstriction. With hyperpolarized helium-3 magnetic resonance (H(3)HeMR) imaging, the airspaces are depicted and focal areas of airflow obstruction are shown as "ventilation defects."
  
  
  OBJECTIVE
  To investigate the regional changes of airflow obstruction with time and repeated bronchoconstriction.
  
  
  METHODS
  H(3)HeMR and spirometry were performed before (pre) and immediately after (post) methacholine challenge in 10 young patients with asthma on 2 days that were 7-476 days (mean, 185.3 +/- 37.2 days) apart. Pair-wise image comparisons were performed to determine the change in location of ventilation defects within the lung and their change in size.
  
  
  RESULTS
  When comparing premethacholine versus premethacholine and postmethacholine versus post-methacholine images of the 2 days, 41% +/- 10% and 69% +/- 5% (P = .017) of defects, respectively, were in the same location, and of those, 69% +/- 12% and 43% +/- 5% (P = .022), respectively, did not change size. Comparing premethacholine versus postmethacholine images, 58% +/- 9% of defects were in the same location on day 1 and 73% +/- 7% (P = .088) on day 2. On both days, the percent increase in defect number from premethacholine to postmethacholine was much greater than the percent decrease in spirometric values (P < .001).
  
  
  CONCLUSIONS
  Many of the ventilation defects persisted or recurred in the same location with time or repeated bronchoconstriction, suggesting that the regional changes of airflow obstruction are relatively fixed within the lung.
  
  
  CONCLUSIONS
  The findings give new insight into the regional airflow variability within the lungs of patients with asthma.
authors.affiliation: Department of Radiology, University of Virginia, Charlottesville, VA 22908, USA. delange@virginia.edu
authors.forename: Eduard E
authors.initials: EE
authors.lastname: de Lange
authors.forename: Talissa A
authors.initials: TA
authors.lastname: Altes
authors.forename: James T
authors.initials: JT
authors.lastname: Patrie
authors.forename: Jaywant
authors.initials: J
authors.lastname: Parmar
authors.forename: James R
authors.initials: JR
authors.lastname: Brookeman
authors.forename: John P
authors.initials: JP
authors.lastname: Mugler
authors.forename: Thomas A E
authors.initials: TA
authors.lastname: Platts-Mills
mesh_terms: D000328:Adult; D000402:Airway Obstruction / Q000503:physiopathology*; D001249:Asthma / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D005260:Female; D006371:Helium; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D016210:Methacholine Chloride / Q000494:pharmacology; D008875:Middle Aged; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D013147:Spirometry
chemical_list: D016085:Bronchoconstrictor Agents; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D016210:Methacholine Chloride; D006371:Helium