Revealing diffusion time-dependence and exchange effect in the in vivo human brain gray matter by using high gradient diffusion MRI
Hong Hsi Lee1,2, Jonas L Olesen3,4, Qiyuan Tian1,2, Gabriel Ramos Llorden1,2, Sune N Jespersen3,4, and Susie Y Huang1,2
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
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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