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The importance of axonal undulation in diffusion MR measurements: a Monte Carlo simulation study.

Nilsson, Markus LU ; Lätt, Jimmy LU ; Ståhlberg, Freddy LU ; van Westen, Danielle LU and Hagslätt, Håkan (2012) In NMR in Biomedicine 25. p.795-805
Abstract
Many axons follow wave-like undulating courses. This is a general feature of extracranial nerve segments, but is also found in some intracranial nervous tissue. The importance of axonal undulation has previously been considered, for example, in the context of biomechanics, where it has been shown that posture affects undulation properties. However, the importance of axonal undulation in the context of diffusion MR measurements has not been investigated. Using an analytical model and Monte Carlo simulations of water diffusion, this study compared undulating and straight axons in terms of diffusion propagators, diffusion-weighted signal intensities and parameters derived from diffusion tensor imaging, such as the mean diffusivity (MD), the... (More)
Many axons follow wave-like undulating courses. This is a general feature of extracranial nerve segments, but is also found in some intracranial nervous tissue. The importance of axonal undulation has previously been considered, for example, in the context of biomechanics, where it has been shown that posture affects undulation properties. However, the importance of axonal undulation in the context of diffusion MR measurements has not been investigated. Using an analytical model and Monte Carlo simulations of water diffusion, this study compared undulating and straight axons in terms of diffusion propagators, diffusion-weighted signal intensities and parameters derived from diffusion tensor imaging, such as the mean diffusivity (MD), the eigenvalues and the fractional anisotropy (FA). All parameters were strongly affected by the presence of undulation. The diffusivity perpendicular to the undulating axons increased with the undulation amplitude, thus resembling that of straight axons with larger diameters. Consequently, models assuming straight axons for the estimation of the axon diameter from diffusion MR measurements might overestimate the diameter if undulation is present. FA decreased from approximately 0.7 to 0.5 when axonal undulation was introduced into the simulation model structure. Our results indicate that axonal undulation may play a role in diffusion measurements when investigating, for example, the optic and sciatic nerves and the spinal cord. The simulations also demonstrate that the stretching or compression of neuronal tissue comprising undulating axons alters the observed water diffusivity, suggesting that posture may be of importance for the outcome of diffusion MRI measurements. Copyright © 2011 John Wiley & Sons, Ltd. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
NMR in Biomedicine
volume
25
pages
795 - 805
publisher
John Wiley & Sons
external identifiers
  • wos:000302617600011
  • pmid:22020832
  • scopus:84859639709
ISSN
0952-3480
DOI
10.1002/nbm.1795
language
English
LU publication?
yes
id
43dcf1ad-4e61-43e0-9f6e-97837f4b6cc7 (old id 2200277)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/22020832?dopt=Abstract
date added to LUP
2011-11-02 12:35:55
date last changed
2017-08-27 05:42:58
@article{43dcf1ad-4e61-43e0-9f6e-97837f4b6cc7,
  abstract     = {Many axons follow wave-like undulating courses. This is a general feature of extracranial nerve segments, but is also found in some intracranial nervous tissue. The importance of axonal undulation has previously been considered, for example, in the context of biomechanics, where it has been shown that posture affects undulation properties. However, the importance of axonal undulation in the context of diffusion MR measurements has not been investigated. Using an analytical model and Monte Carlo simulations of water diffusion, this study compared undulating and straight axons in terms of diffusion propagators, diffusion-weighted signal intensities and parameters derived from diffusion tensor imaging, such as the mean diffusivity (MD), the eigenvalues and the fractional anisotropy (FA). All parameters were strongly affected by the presence of undulation. The diffusivity perpendicular to the undulating axons increased with the undulation amplitude, thus resembling that of straight axons with larger diameters. Consequently, models assuming straight axons for the estimation of the axon diameter from diffusion MR measurements might overestimate the diameter if undulation is present. FA decreased from approximately 0.7 to 0.5 when axonal undulation was introduced into the simulation model structure. Our results indicate that axonal undulation may play a role in diffusion measurements when investigating, for example, the optic and sciatic nerves and the spinal cord. The simulations also demonstrate that the stretching or compression of neuronal tissue comprising undulating axons alters the observed water diffusivity, suggesting that posture may be of importance for the outcome of diffusion MRI measurements. Copyright © 2011 John Wiley & Sons, Ltd.},
  author       = {Nilsson, Markus and Lätt, Jimmy and Ståhlberg, Freddy and van Westen, Danielle and Hagslätt, Håkan},
  issn         = {0952-3480},
  language     = {eng},
  pages        = {795--805},
  publisher    = {John Wiley & Sons},
  series       = {NMR in Biomedicine},
  title        = {The importance of axonal undulation in diffusion MR measurements: a Monte Carlo simulation study.},
  url          = {http://dx.doi.org/10.1002/nbm.1795},
  volume       = {25},
  year         = {2012},
}