The Extracellular Diffusion Weighted Signal Predicts Axon Diameter Distribution Parameters

Hubert Martinus Fonteijn¹, Matt G. Hall¹, Daniel C. Alexander¹

The estimation of axon diameter distribution parameters remains a big challenge for diffusion-weighted imaging. Generally, only intracellular diffusion is considered to be influenced by axon diameter. Extracellular diffusion on the other hand is considered to be approximately Gaussian in the long diffusion time limit and to be independent of axon diameter. In this abstract, we perform Monte Carlo simulations of diffusion in the extracellular compartment for a wide range of diffusion times and we construct a non-parametric model of extracellular diffusion using Gaussian Process Regression. We then show that axon diameter distribution parameters can be estimated from this model.