(ISMRM 2024) Quantifying changes of axonal shape in traumatic brain injury with time-dependent diffusion
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Abstract #0304

Quantifying changes of axonal shape in traumatic brain injury with time-dependent diffusion

Ali Abdollahzadeh1,2, Ricardo Coronado-Leija1,2, Hong-Hsi Lee3, Alejandra Sierra4, Els Fieremans1,2, and Dmitry S. Novikov1,2
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, New York University Grossman School of Medicine, New York, NY, United States, 3Department of Radiology, Harvard Medical School, Boston, MA, United States, 4A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland

Synopsis

Keywords: Microstructure, Modelling, Axons, Diffusion, Validation, TBI, Segmentation, Electron microscopy

Motivation: Interpreting diffusion MRI (dMRI) in terms of brain tissue micro-geometry.

Goal(s): To identify cellular features that govern diffusion measurements among myriads of parameters specifying tissue microstructure.

Approach: We found how axonal micro-geometry is manifested in a dMRI measurement by analytically solving the diffusion equation in a tube with a randomly varying cross-section.

Results: We identify a specific power-law approach of the time-dependent diffusion coefficient along the axon to its long-time limit. The average inverse cross-section and the variance of long-range cross-sectional fluctuations govern the diffusive dynamics. We quantify changes in these non-trivial geometrical features, associated with axonal beading, in a rat TBI model.

Impact: Beading is a characteristic feature of numerous neurodegenerative diseases triggered by different pathological conditions and injuries. Here, we detect geometrical changes in the axonal micro-geometry, accessible via the along-tract diffusivity from the diffusion tensor using clinically feasible diffusion weightings.

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Keywords

diffusioncrossgammatortuosityaxons