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On the effects of a varied diffusion time in vivo: is the diffusion in white matter restricted?

Nilsson, Markus LU ; Lätt, Jimmy LU ; Nordh, Emil LU ; Wirestam, Ronnie LU ; Ståhlberg, Freddy LU and Brockstedt, Sara LU (2009) In Magnetic Resonance Imaging 27(2008 Jul 25). p.176-187
Abstract
The aim of this work was to study the diffusion-related signal attenuation curves (signal-vs.-b curves) measured perpendicular and parallel to the neuronal fibers of the corticospinal tract in vivo and to determine whether effects of restricted diffusion could be observed when varying the diffusion time (T(D)). A biexponential model and a two-compartment model including exchange according to the Kärger formalism were employed to analyze the signal-vs.-b curves. To validate the two-compartment model, restricted diffusion with exchange was simulated for uniformly sized cylinders, using different diameters and exchange times. The model was shown to retrieve the simulated parameters well, also when the short gradient pulse approximation was... (More)
The aim of this work was to study the diffusion-related signal attenuation curves (signal-vs.-b curves) measured perpendicular and parallel to the neuronal fibers of the corticospinal tract in vivo and to determine whether effects of restricted diffusion could be observed when varying the diffusion time (T(D)). A biexponential model and a two-compartment model including exchange according to the Kärger formalism were employed to analyze the signal-vs.-b curves. To validate the two-compartment model, restricted diffusion with exchange was simulated for uniformly sized cylinders, using different diameters and exchange times. The model was shown to retrieve the simulated parameters well, also when the short gradient pulse approximation was not met. The in vivo measurements performed perpendicular to the tracts, using b values up to 28000 s/mm(2) and T(D) values between 64 and 256 ms, did not show the effects of restricted diffusion as expected from previous ex vivo studies. The applied two-compartment model yielded an average axonal diameter of about 4 mum and an intracellular exchange time of about 300 ms, but did not fit statistically well to the data. In conclusion, this study indicates that if the diffusion is modeled as two compartments, of which one is restricted, exchange must be included in the model. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Magnetic Resonance Imaging
volume
27
issue
2008 Jul 25
pages
176 - 187
publisher
Elsevier
external identifiers
  • wos:000263533300004
  • pmid:18657924
  • scopus:59249099382
ISSN
1873-5894
DOI
10.1016/j.mri.2008.06.003
language
English
LU publication?
yes
id
df1e7770-9487-4f9d-b38c-05ba4dd266ed (old id 1180819)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/18657924?dopt=Abstract
date added to LUP
2008-08-07 11:27:12
date last changed
2017-08-13 04:33:58
@article{df1e7770-9487-4f9d-b38c-05ba4dd266ed,
  abstract     = {The aim of this work was to study the diffusion-related signal attenuation curves (signal-vs.-b curves) measured perpendicular and parallel to the neuronal fibers of the corticospinal tract in vivo and to determine whether effects of restricted diffusion could be observed when varying the diffusion time (T(D)). A biexponential model and a two-compartment model including exchange according to the Kärger formalism were employed to analyze the signal-vs.-b curves. To validate the two-compartment model, restricted diffusion with exchange was simulated for uniformly sized cylinders, using different diameters and exchange times. The model was shown to retrieve the simulated parameters well, also when the short gradient pulse approximation was not met. The in vivo measurements performed perpendicular to the tracts, using b values up to 28000 s/mm(2) and T(D) values between 64 and 256 ms, did not show the effects of restricted diffusion as expected from previous ex vivo studies. The applied two-compartment model yielded an average axonal diameter of about 4 mum and an intracellular exchange time of about 300 ms, but did not fit statistically well to the data. In conclusion, this study indicates that if the diffusion is modeled as two compartments, of which one is restricted, exchange must be included in the model.},
  author       = {Nilsson, Markus and Lätt, Jimmy and Nordh, Emil and Wirestam, Ronnie and Ståhlberg, Freddy and Brockstedt, Sara},
  issn         = {1873-5894},
  language     = {eng},
  number       = {2008 Jul 25},
  pages        = {176--187},
  publisher    = {Elsevier},
  series       = {Magnetic Resonance Imaging},
  title        = {On the effects of a varied diffusion time in vivo: is the diffusion in white matter restricted?},
  url          = {http://dx.doi.org/10.1016/j.mri.2008.06.003},
  volume       = {27},
  year         = {2009},
}