AN ANALYTICAL MODEL OF RESTRICTED DIFFUSION IN BOVINE OPTIC-NERVE

An analytical model of restricted diffusion in bovine optic nerve is p resented. The nerve tissue model is composed of two different objects: prolate ellipsoids (axons) and spheres (glial cells) surrounded by pa rtially permeable membranes. The free diffusion coefficients of intrac ellular and extracellular water may differ. Analytical formulas for si gnal loss due to diffusion in the pulsed gradient spin echo (PGSE) exp eriment for this tissue model are derived. The model is fitted to expe rimental data for bovine optic nerve. The obtained model parameters ar e shown to be reasonable. The model describes all of the characteristi cs of the PGSE data: anisotropy, upward curvature of decay curves, and diffusion time dependence. The validity and sensitivity of the model are also discussed.