Abstract #1566

The Effect of Beading and Permeable Axons on Water Diffusion Properties: A Monte Carlo Simulation of Axonal Degeneration and Its Effect on DTI and Q-Space Contrasts

Jonathan Andrew David Farrell^1,2, Bennett A. Landman^3,4, Jiangyang Zhang¹, Seth A. Smith^5,6, Daniel S. Reich^1,7, Peter A. Calabresi⁸, Peter C.M. van Zijl^1,2

¹Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States; ²Kennedy Krieger Institute, F.M. Kirby Research Center for Functional Brain Imaging, Baltimore, MD, United States; ³Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States; ⁴Electrical Engineering, Vanderbilt University, Nashville, TN, United States; ⁵Dept. of Radiology, Vanderbilt University, Nashville, TN, United States; ⁶Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States; ⁷Neuroimmunology Branch (NINDS), National Institutes of Health, Bethesda, MD, United States; ⁸Dept. of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Axonal injury can produce constrictions and enlargements (beading) of axon membranes and increase their permeability. Here we investigate the effect of these morphological parameters on diffusion properties measured with diffusion tensor and q-space imaging. Degenerating axons are modeled as the union of cylinders and spheres of varying radii. Using Monte Carlo simulations, with intra- and extra-cellular compartments, we show that beading and increased permeability can act in concert to produce increased perpendicular diffusion. However, while parallel diffusion is decreased by beading, non-Gaussian behavior is mitigated by increased permeability. This study may aid the development of contrasts specific for axonal injury.