Abstract #0254

Revealing diffusion time-dependence and exchange effect in the in vivo human brain gray matter by using high gradient diffusion MRI

Hong Hsi Lee^1,2, Jonas L Olesen^3,4, Qiyuan Tian^1,2, Gabriel Ramos Llorden^1,2, Sune N Jespersen^3,4, and Susie Y Huang^1,2

¹Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ²Department of Radiology, Harvard Medical School, Boston, MA, United States, ³Center of Functionally Integrative Neuroscience (CFIN) and MINDLab, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark, ⁴Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark

Synopsis

The characteristic signal time-dependence in the brain gray matter indicates a significant exchange effect, modeled by an extension of the Kärger exchange model. Here we perform in vivo diffusion measurements with varying time scales (21-40 ms) up to high b-values (≤22 ms/µm²) in a healthy subject on an HCP scanner, and observe the signal time-dependence in frontal lobe, temporal lobe, and limbic system. The estimated residence time is 2-7 ms in the brain gray matter, suggesting that diffusion in neurite and extra-cellular space is coarse-grained at clinical diffusion time scale.

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