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Abstract #3884

Microscopic kurtosis tensor invariants and DDE 4-fold angular modulation in human brain diffusion MRI

Santiago Coelho1,2, 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 (CAI2R), Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States

Synopsis

Keywords: Microstructure, Microstructure, Double Diffusion Encoding

Motivation: dMRI signal at moderate diffusion-weightings $$$\sim\,b^2$$$ has contributions from intrinsic (microstructural) kurtosis, and from heterogeneity of compartments.

Goal(s): To separate all kurtosis sources and provide a complete set of tensor invariants for a most general distribution of non-Gaussian compartments.

Approach: We decompose double diffusion encoding (DDE) signal into irreducible spherical tensor components via harmonic analysis on the rotation group manifold, a 3-dimensional sphere $$$\mathbb{S}^3$$$.

Results: We find a complete set of 18(covariances) + 12(microscopic-kurtosis)=33 independent rotational invariants at $$$b^2$$$ level.

Impact: We observe for the first time a 4-fold angular modulation of double diffusion encoding signal in the human brain in vivo. This validates the presence of higher-order tensor anisotropies in brain microstructure, which we fully quantify at the $$$b^2$$$ level.

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