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Nonivasive quantification of axon radii using diffusion MRI.

Authors
  • Veraart, Jelle1, 2, 3
  • Nunes, Daniel1
  • Rudrapatna, Umesh4
  • Fieremans, Els2
  • Jones, Derek K4, 5
  • Novikov, Dmitry S2
  • Shemesh, Noam1
  • 1 Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal. , (Portugal)
  • 2 Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, United States. , (United States)
  • 3 imec-Vision Lab, Department of Physics, University of Antwerp, Antwerp, Belgium. , (Belgium)
  • 4 CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom. , (United Kingdom)
  • 5 Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia. , (Australia)
Type
Published Article
Journal
eLife
Publisher
"eLife Sciences Organisation, Ltd."
Publication Date
Feb 12, 2020
Volume
9
Identifiers
DOI: 10.7554/eLife.49855
PMID: 32048987
Source
Medline
Keywords
Language
English
License
Unknown

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. © 2020, Veraart et al.

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