Noninvasive Quantification Of Alveolar Morphometry In Elderly Never-And Ex-Smokers

Diffusion-weighted magnetic resonance imaging (MRI) provides a way to generate in vivo lung images with contrast sensitive to the molecular displacement of inhaled gas at subcellular length scales. Here, we aimed to evaluate hyperpolarized 3 He MRI estimates of the alveolar dimensions in 38 healthy elderly never-smokers (73 +/- 6 years, 15 males) and 21 elderly ex-smokers (70 +/- 10 years, 14 males) with (n = 8, 77 +/- 6 years) and without emphysema (n = 13, 65 +/- 10 years). The ex-smoker and never-smoker subgroups were significantly different for FEV1/FVC (P = 0.0001) and DLCO (P = 0.009); while ex-smokers with emphysema reported significantly diminished FEV1/FVC (P = 0.02) and a trend toward lower DLCO (P = 0.05) than ex-smokers without emphysema. MRI apparent diffusion coefficients (ADC) and CT measurements of emphysema (relative area-CT density histogram, RA950) were significantly different (P = 0.001 and P = 0.007) for never-smoker and exsmoker subgroups. In never-smokers, the MRI estimate of mean linear intercept (260 +/- 27 lm) was significantly elevated as compared to the results previously reported in younger never-smokers (210 +/- 30 lm), and trended smaller than in the age-matched ex-smokers (320 +/- 72 lm, P = 0.06) evaluated here. Never-smokers also reported significantly smaller internal (220 +/- 24 lm, P = 0.01) acinar radius but greater alveolar sheath thickness (120 +/- 4 lm, P < 0.0001) than ex-smokers. Never-smokers were also significantly different than ex-smokers without emphysema for alveolar sheath thickness but not ADC, while ex-smokers with emphysema reported significantly different ADC but not alveolar sheath thickness compared to ex-smokers without CT evidence of emphysema. Differences in alveolar measurements in never-and ex-smokers demonstrate the sensitivity of MRI measurements to the different effects of smoking and aging on acinar morphometry.