Electronic Thesis and Dissertation Repository


Master of Science


Medical Biophysics


Dr. Grace Parraga


Diffusion-weighted noble gas pulmonary magnetic resonance imaging (MRI) provides in vivo images with a contrast uniquely sensitive to molecular displacement at cellular and sub-cellular length scales. We estimated the external airway radius (R) and internal airway radius (r) of the alveolar dimensions to evaluate potential differences in acinar duct morphometries in healthy older never-smokers and compared those with a group of ex-smokers. The acinar duct and alveolar MRI morphometry results were within the physiologically-valid range of parameters. Estimated values of internal (r) and external (R) airway radius as well as alveolar sheath (h) and mean linear intercept (Lm) for individual subjects were similar with low variance. Results showed that MRI measurements of lung air space size in healthy older never-smokers were elevated compared to previous results reported in younger never-smokers, and lower than in age-matched ex-smokers (p<.05). Specifically, older never-smokers had significantly lower external and internal airway radius and mean linear intercept, but higher alveolar sheath thickness, alveolar density and surface area-to-volume ratio than ex-smokers (p<.05). Such results are compatible with the senile emphysematous changes to healthy parenchyma that accompany aging. These results demonstrate the potential MRI has with regards to replacing histology and lung stereology as the gold standard for measuring pulmonary acinus microstructure.