Abstract #0602

Coarse-graining with time-dependent diffusion reveals signatures of demyelination and axonal loss

Ricardo Coronado-Leija^1,2, Hong-Hsi Lee^3,4, Els Fieremans^1,2, and Dmitry S. Novikov^1,2

¹Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States, ²Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States, ³Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States, ⁴Harvard Medical School, Boston, MA, United States

Synopsis

Keywords: Simulation/Validation, Diffusion/other diffusion imaging techniques

Motivation: Time-dependent diffusion $$$D(t)$$$ is sensitive to brain microstructure. Using Monte Carlo (MC) simulations, $$$D(t)$$$ has been shown to provide information about structural changes caused by pathological conditions.

Goal(s): To establish the relation between the parameters of $$$D(t)$$$ and the extra-axonal space geometry.

Approach: We solve the Fick-Jacobs equation in the effective medium framework, connect $$$D(t)$$$ to correlations of density and local diffusivity, and validate with Monte-Carlo simulations.

Results: Time-dependence of $$$D(t)$$$ is quantitatively related to geometric characteristics of axonal packing, demyelination and axonal loss.

Impact: By coarse-graining the extra-axonal space, time-dependent diffusion explores the geometry relevant for demyelination and axonal loss, enabling quantifying axonal microstructure.

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