title: Pulmonary MRI morphometry modeling of airspace enlargement in chronic obstructive pulmonary disease and alpha-1 antitrypsin deficiency.
abstract: OBJECTIVE
  We generated lung morphometry measurements using single-breath diffusion-weighted MRI and three different acinar duct models in healthy participants and patients with emphysema stemming from chronic obstructive lung disease (COPD) and alpha-1 antitrypsin deficiency (AATD).
  
  
  METHODS
  Single-breath-inhaled3He MRI with five diffusion sensitizations (b-value = 0, 1.6, 3.2, 4.8, and 6.4 s/cm2) was used, and signal intensities were fit using a cylindrical and single-compartment acinar-duct model to estimate MRI-derived mean linear intercept (Lm) and surface-to-volume ratio (S/V). A stretched exponential model was also developed to estimate the mean airway length and Lm.
  
  
  RESULTS
  We evaluated 42 participants, including 15 elderly never-smokers (69 ± 5 years), 12 ex-smokers without COPD (67 ± 11 years), 9 COPD ex-smokers (80 ± 6 years), and 6 AATD patients (59 ± 6 years). In the never- and ex-smokers, the diffusing capacity of the lung for carbon monoxide (DLCO) and computed tomography relative area of less than -950 Hounsfield units (RA950) were normal, but these were abnormal in the COPD and AATD patients, which is reflective of emphysema. Although cylindrical and stretched-exponential-model estimates of Lmand S/V were not significantly different, the single-compartment-model estimates were significantly different (P < 0.05) for the never- and ex-smoker subgroups. All models estimated significantly worse Lmand S/V in the AATD and COPD subgroups compared with the never- and ex-smokers without emphysema.
  
  
  CONCLUSIONS
  Differences in airspace enlargement may be estimated using Lmand S/V, generated using MRI and a stretched-exponential or cylindrical model of the acinar ducts. Magn Reson Med 79:439-448, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Robarts Research Institute, London, Canada.|Department of Medical Biophysics, the University of Western Ontario, London, Canada.
authors.forename: Alexei
authors.initials: A
authors.lastname: Ouriadov
authors.affiliation: Robarts Research Institute, London, Canada.|Department of Medical Biophysics, the University of Western Ontario, London, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Lessard
authors.affiliation: Robarts Research Institute, London, Canada.|Department of Medical Biophysics, the University of Western Ontario, London, Canada.
authors.forename: Khadija
authors.initials: K
authors.lastname: Sheikh
authors.affiliation: Robarts Research Institute, London, Canada.|Department of Medical Biophysics, 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; D003198:Computer Simulation; D004058:Diffusion; D004646:Emphysema / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging*; D012119:Respiration; D012907:Smoking; D014057:Tomography, X-Ray Computed; D019896:alpha 1-Antitrypsin Deficiency / Q000000981:diagnostic imaging*
chemical_list: D010100:Oxygen
keywords: COPD; alpha-1 antitrypsin deficiency; hyperpolarized gas; lung; morphometry