Niels Buhl1,2, Sune Nrhj Jespersen2
1Department of Physics & Astronomy, Aarhus University, Aarhus, Denmark; 2Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark
We present an analytical treatment of long time scale diffusion weighted MRI of the human lung. Diffusion in the airways of the lung is modeled as diffusion on a network of connected line segments, with the relative position of each line segment given by the symmetric branching geometry. Within this model we are able to average the time dependent diffusion coefficient over all airways of the acinar region. The theory is in good agreement with published 3He long time scale measurements, provided the latter may be treated as roughly satisfying the Gaussian phase approximation.