title: Ventilation heterogeneity in ex-smokers without airflow limitation.
abstract: OBJECTIVE
  Hyperpolarized (3)He magnetic resonance imaging (MRI) ventilation abnormalities are visible in ex-smokers without airflow limitation, but the clinical relevance of this is not well-understood. Our objective was to phenotype healthy ex-smokers with normal and abnormally elevated ventilation defect percent (VDP).
  
  
  METHODS
  Sixty ex-smokers without airflow limitation provided written informed consent to (3)He MRI, computed tomography (CT), and pulmonary function tests in a single visit. (3)He MRI VDP and apparent diffusion coefficients (ADCs) were measured for whole-lung and each lung lobe as were CT measurements of emphysema (relative area [RA] with attenuation ≤-950 HU, RA950) and airway morphology (wall area percent [WA%], lumen area [LA] and LA normalized to body surface area [LA/BSA]).
  
  
  RESULTS
  In 42 ex-smokers, there was abnormally elevated VDP and no significant differences for pulmonary function, RA950, or airway measurements compared to 18 ex-smokers with normal VDP. Ex-smokers with abnormally elevated VDP reported significantly greater (3)He ADC in the apical lung (right upper lobe [RUL], P = .02; right middle lobe [RML], P = .04; and left upper lobe [LUL], P = .009). Whole lung (r = 0.40, P = .001) and lobar VDP (RUL, r = 0.32, P = .01; RML, r = 0.46, P = .002; right lower lobe [RLL], r = 0.38, P = .003; LUL, r = 0.35, P = .006; and left lower lobe, r = 0.37, P = .004) correlated with regional (3)He ADC. Although whole-lung VDP and CT airway morphology measurements were not correlated, regional VDP was correlated with RUL LA (r = -0.37, P = .004), LA/BSA (r = -0.42, P = .0008), RLL WA% (r = 0.28, P = .03), LA (r = -0.28, P = .03), and LA/BSA (r = -0.37, P = .004).
  
  
  CONCLUSIONS
  Abnormally elevated VDP in ex-smokers without airflow limitation was coincident with very mild emphysema detected using MRI and regional airway remodeling detected using CT representing a subclinical obstructive lung disease phenotype.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, 1151 Richmond St N, London, ON, Canada N6A 5B7; Department of Medical Biophysics, The University of Western Ontario, London, Canada.
authors.forename: Damien
authors.initials: D
authors.lastname: Pike
authors.affiliation: James Hogg Research Centre, St. Paul's Hospital, University of British Columbia, Vancouver, Canada.
authors.forename: Miranda
authors.initials: M
authors.lastname: Kirby
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, 1151 Richmond St N, London, ON, Canada N6A 5B7; Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Canada.
authors.forename: Fumin
authors.initials: F
authors.lastname: Guo
authors.affiliation: Division of Respirology, Department of Medicine, The University of Western Ontario, London, Canada.
authors.forename: David G
authors.initials: DG
authors.lastname: McCormack
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, 1151 Richmond St N, London, ON, Canada N6A 5B7; Department of Medical Biophysics, The University of Western Ontario, London, Canada; Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Canada. Electronic address: gparraga@robarts.ca.
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
mesh_terms: D000368:Aged; D004646:Emphysema / Q000503:physiopathology*; D005260:Female; D006371:Helium; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007554:Isotopes; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology; D012123:Pulmonary Ventilation; D019275:Radiopharmaceuticals; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012907:Smoking / Q000503:physiopathology*; D016540:Smoking Cessation
chemical_list: D007554:Isotopes; D019275:Radiopharmaceuticals; D006371:Helium
keywords: Hyperpolarized (3)He magnetic resonance imaging; airways disease; computed tomography; emphysema