Jacob, R. E., K. R. Minard, G. Laicher and C. Timchalk (2008). "3D He-3 diffusion MRI as a local in vivo morphometric tool to evaluate emphysematous rat lungs." Journal of Applied Physiology 105(4): 1291-1300.
In this work, we investigate He-3 magnetic resonance imaging as a noninvasive morphometric tool to assess emphysematous disease state on a local level. Emphysema was induced intratracheally in rats with 25 U/100 g body wt of porcine pancreatic elastase dissolved in 200 mu l saline. Rats were then paired with saline-dosed controls. Nine three-dimensional (3D) He-3 diffusion-weighted images were acquired at 1, 2, or 3 wk postdose, after which the lungs were harvested and prepared for histological analysis. Recently introduced indexes sensitive to the heterogeneity of the air space size distribution were calculated. These indexes, D-1 and D-2, were derived from the moments of the mean equivalent airway diameters. Averaged over the entire lung, it is shown that the average 3He diffusivity (D-ave) correlates well with histology (R = 0.85, P < 0.0001). By matching small (0.046 cm(2)) regions in 3He images with corresponding regions in histological slices, Dave correlates significantly with both D-1 and D-2 (R = 0.88 and R = 0.90, respectively, with P < 0.0001). It is concluded that 3He MRI is a viable noninvasive morphometric tool for localized in vivo emphysema assessment.
