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Abstract #0252

Breaking the power law scaling of the dMRI signal on the Connectom scanner reveals its sensitivity to axon diameters

Jelle Veraart1, Els Fieremans1, Umesh Rudrapatna2, Derek K Jones2, and Dmitry S Novikov1

1Center for Biomedical Imaging, NYU School of Medicine, New York, NY, United States, 2CUBRIC, Cardiff University, Cardiff, United Kingdom

We demonstrate that in vivo diffusion MRI becomes sensitive to intra-axonal properties such as the inner axon diameters, when diffusion weightings in the range $$$b\sim7,000-25000\,\mathrm{s/mm^2}$$$ are achieved on the Human Connectom scanner (using gradients of 300mT/m). By analyzing the diffusion-weighted signal in the human white matter as a function of $$$b$$$, we observe significant deviations from the $$$b^{-1/2}$$$ scaling associated with the conventional “stick” model of infinitely-narrow axons. Our estimated effective MR diameters, heavily weighted by the tail of the axon diameter distribution, agree well with those calculated from histology histograms available from literature.

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