An Analytical Model of Diffusion and Exchange of Water in White Matter from Diffusion-MRI and Its Application in Measuring Axon Radii

Wenjin Zhou¹, David H. Laidlaw¹

We present an analytical model of diffusion and water exchange in white matter to estimate axon radii. Direct measurement of important biomarkers such as the axon radii, density, and permeability are important for early detection of diseases. We use a model with two compartments between which there is exchange of water molecules. Our analytical formulas examine the derivation of axonal parameters that affect the signal attenuation of diffusion-MRI experiments. The model is fitted to Monte Carlo simulation data. The parameters recovered are compared with ground truth from simulation and prove the feasibility of recovering underlying axonal radii using the model.