MR imaging of diffusion of (3)He gas in healthy and diseased lungs.

Hyperpolarized (3)He gas MRI was used to form maps of the effective diffusivity of gas in human lungs. Images of diffusion as well as spin density are presented from a study of 11 healthy volunteers and 5 patients with severe emphysema. The effective rate of diffusion, D(e), of the gas is reduced by the alveolar walls; tissue destruction in emphysema is hypothesized to result in larger D(e). Indeed, the mean value of D(e) in the emphysematous lungs is found here to be about 2.5 times that of healthy lungs, although still smaller than the unrestricted diffusivity of (3)He in free air. Histograms of D(e) values across coronal slices are presented. The results are discussed in terms of spatial variations, variations among individuals, healthy and diseased, and variations due to changes in lung volume. Magn Reson Med 44:174-179, 2000.