Simulating Helium-3 Diffusion in the Lung: Comparing the “Cylinder-Model” with Simulated 3D Alveolar Ducts

S. Fichele, M. N. Paley, N. Woodhouse, Z. Said, P. D. Griffiths, E. J. van Beek, J. M. Wild Academic Unit of Radiology, University of Sheffield, Sheffield, United Kingdom Introduction: Devising a complete analytical theory that describes Helium-3 diffusion in lung tissue is difficult. The most recent attempt makes the approximation that each alveolar duct can be treated as a smooth walled, infinitely long cylinder, for which the diffusion equation can be solved [1]. In this case diffusion is considered anisotropic, and is categorized by two components; one along the principle axis, DL, and the other transverse, DT. The results from the transverse component can be used to predict the average radii of the alveolar ducts for which in-vivo experiments have yielded plausible results.