title: Regional Heterogeneity of Chronic Obstructive Pulmonary Disease Phenotypes: Pulmonary (3)He Magnetic Resonance Imaging and Computed Tomography.
abstract: Pulmonary ventilation may be visualized and measured using hyperpolarized (3)He magnetic resonance imaging (MRI) while emphysema and its distribution can be quantified using thoracic computed tomography (CT). Our objective was to phenotype ex-smokers with COPD based on the apical-to-basal distribution of ventilation abnormalities and emphysema to better understand how these phenotypes change regionally as COPD progresses. We evaluated 100 COPD ex-smokers who provided written informed consent and underwent spirometry, CT and (3)He MRI. (3)He MRI ventilation imaging was used to quantify the ventilation defect percent (VDP) for whole-lung and individual lung lobes. Regional VDP was used to generate the apical-lung (AL)-to-basal-lung (BL) difference (ΔVDP); a positive ΔVDP indicated AL-predominant and negative ΔVDP indicated BL-predominant ventilation defects. Emphysema was quantified using the relative-area-of-the-lung ≤-950HU (RA950) of the CT density histogram for whole-lung and individual lung lobes. The AL-to-BL RA950 difference (ΔRA950) was generated with a positive ΔRA950 indicating AL-predominant emphysema and a negative ΔRA950 indicating BL-predominant emphysema. Seventy-two ex-smokers reported BL-predominant MRI ventilation defects and 71 reported AL-predominant CT emphysema. BL-predominant ventilation defects (AL/BL: GOLD I = 18%/82%, GOLD II = 24%/76%) and AL-predominant emphysema (AL/BL: GOLD I = 84%/16%, GOLD II = 72%/28%) were the major phenotypes in mild-moderate COPD. In severe COPD there was a more uniform distribution for ventilation defects (AL/BL: GOLD III = 40%/60%, GOLD IV = 43%/57%) and emphysema (AL/BL: GOLD III = 64%/36%, GOLD IV = 43%/57%). Basal-lung ventilation defects predominated in mild-moderate GOLD grades, and a more homogeneous distribution of ventilation defects was observed in more advanced grade COPD; these differences suggest that over time, regional ventilation abnormalities become more homogenously distributed during disease progression.
authors.affiliation: a Robarts Research Institute, The University of Western Ontario , London , Canada.|b Department of Medical Biophysics , The University of Western Ontario , London , Canada.
authors.forename: Damien
authors.initials: D
authors.lastname: Pike
authors.affiliation: c 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: a Robarts Research Institute, The University of Western Ontario , London , Canada.|b Department of Medical Biophysics , The University of Western Ontario , London , Canada.
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Eddy
authors.affiliation: a Robarts Research Institute, The University of Western Ontario , London , Canada.|d Graduate Program in Biomedical Engineering, The University of Western Ontario , London , Canada.
authors.forename: Fumin
authors.initials: F
authors.lastname: Guo
authors.affiliation: a Robarts Research Institute, The University of Western Ontario , London , Canada.|b Department of Medical Biophysics , The University of Western Ontario , London , Canada.
authors.forename: Dante P I
authors.initials: DP
authors.lastname: Capaldi
authors.affiliation: a Robarts Research Institute, The University of Western Ontario , London , Canada.
authors.forename: Alexei
authors.initials: A
authors.lastname: Ouriadov
authors.affiliation: e 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: a Robarts Research Institute, The University of Western Ontario , London , Canada.|b Department of Medical Biophysics , The University of Western Ontario , London , Canada.|d Graduate Program in Biomedical Engineering, The University of Western Ontario , London , Canada.
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D004646:Emphysema / Q000000981:diagnostic imaging*; D005260:Female; D005541:Forced Expiratory Volume; D006371:Helium; D006801:Humans; D007554:Isotopes; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D010991:Plethysmography; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012123:Pulmonary Ventilation; D012115:Residual Volume; D016540:Smoking Cessation; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D007554:Isotopes; D006371:Helium; C000615206:Helium-3
keywords: Airways disease; COPD; computed tomography; emphysema; magnetic resonance imaging; phenotypes