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Noninvasive quantification of axon radii using diffusion MRI
Veraart, Jelle Nunes, Daniel Rudrapatna, Umesh Fieremans, Els Jones, Derek K. Novikov, Dmitry S. Shemesh, Noam
Veraart, Jelle
Nunes, Daniel
Rudrapatna, Umesh
Fieremans, Els
Jones, Derek K.
Novikov, Dmitry S.
Shemesh, Noam
Abstract
Axon caliber plays a crucial role in determining conduction velocity and, consequently, in the timing and synchronization of neural activation. Noninvasive measurement of axon radii could have significant impact on the understanding of healthy and diseased neural processes. Until now, accurate axon radius mapping has eluded in vivo neuroimaging, mainly due to a lack of sensitivity of the MRI signal to micron-sized axons. Here, we show how – when confounding factors such as extra-axonal water and axonal orientation dispersion are eliminated – heavily diffusion-weighted MRI signals become sensitive to axon radii. However, diffusion MRI is only capable of estimating a single metric, the effective radius, representing the entire axon radius distribution within a voxel that emphasizes the larger axons. Our findings, both in rodents and humans, enable noninvasive mapping of critical information on axon radii, as well as resolve the long-standing debate on whether axon radii can be quantified.
Keywords
Date
2020
Type
Journal article
Journal
eLife
Book
Volume
9
Issue
Page Range
1-27
Article Number
ACU Department
Collections
Relation URI
Source URL
Event URL
Open Access Status
Published as ‘gold’ (paid) open access
License
CC BY 4.0
File Access
Open