Pulmonary MRI morphometry modeling of airspace enlargement in chronic obstructive pulmonary disease and alpha-1 antitrypsin deficiency.

PurposeWe 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). MethodsSingle-breath-inhaled He-3 MRI with five diffusion sensitizations (b-value=0, 1.6, 3.2, 4.8, and 6.4 s/cm(2)) was used, and signal intensities were fit using a cylindrical and single-compartment acinar-duct model to estimate MRI-derived mean linear intercept (L-m) and surface-to-volume ratio (S/V). A stretched exponential model was also developed to estimate the mean airway length and L-m. ResultsWe evaluated 42 participants, including 15 elderly never-smokers (695 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 (RA(950)) 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 L-m and 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 L-m and S/V in the AATD and COPD subgroups compared with the never- and ex-smokers without emphysema. ConclusionsDifferences in airspace enlargement may be estimated using L-m and S/V, generated using MRI and a stretched-exponential or cylindrical model of the acinar ducts. Magn Reson Med 79:439-448, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.