Examining lung microstructure using 19F MR diffusion imaging in COPD patients

Abstract

To examine the time-dependent diffusion of fluorinated (19 F) gas in human lungs for determination of surface-to-volume ratio in comparison to results from hyperpolarized 129 Xe and lung function testing in healthy volunteers and patients with chronic obstructive pulmonary disease. Diffusion of fluorinated gas in the short-time regime was measured using multiple gradient-echo sequences with a single pair of trapezoidal gradient pulses. Pulmonary surface-to-volume ratio was calculated using a first-order approximation of the time-dependent diffusion in a study with 20 healthy volunteers and 22 patients with chronic obstructive pulmonary disease. The repeatability after 7 days as well as the correlation with hyperpolarized 129 Xe diffusion MRI and lung function testing was analyzed. Using 19 F diffusion MRI, the median surface-to-volume ratio is significantly decreased in chronic obstructive pulmonary disease patients (S/V=126 cm-1 [87-144 cm-1 ]) compared with healthy volunteers (S/V=164 cm-1 [160-84 cm-1 ], p< 0.0001). No significant difference was found between measurements within 7 days for healthy (p= 0.88, median coefficient of variation=4.3%) and diseased subjects (p= 0.58, median coefficient of variation= 6.7%). Linear correlations were found with S/V from 129 Xe diffusion MRI (r= 0.85, p= 0.001) and the forced expiratory volume in 1 second (r= 0.68, p< 0.0001). Examination of lung microstructure using time-dependent diffusion measurement of inhaled 19 F is feasible, repeatable, and correlates with established measurements.