2021_For_FigShare.xlsx

Here, using energy-subtractive synchrotron radiation tomography, we measured, the distribution of an inert gas (Xe) in the <i>in vivo</i> rabbit lung during Xe washin breathing maneuvers. The effects of convective flow rate, diffusion, and cardiac motion were also assessed. Fractal analysis of resulting gas concentration and tissue-density maps revealed that fractal dimension was always smaller for Xe than for tissue density, and that only for the gas, a length scale existed where fractal dimension approached unity. The length scale where this occurred was seen to correspond to that of a rabbit acinus, the terminal structure comprising only alveolated airways.