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Resolution limit of cylinder diameter estimation by diffusion MRI : The impact of gradient waveform and orientation dispersion

Nilsson, Markus LU ; Lasič, Samo; Drobnjak, Ivana; Topgaard, Daniel LU and Westin, Carl-Fredrik (2017) In NMR in Biomedicine 30(7).
Abstract

Diffusion MRI has been proposed as a non-invasive technique for axonal diameter mapping. However, accurate estimation of small diameters requires strong gradients, which is a challenge for the transition of the technique from preclinical to clinical MRI scanners, since these have weaker gradients. In this work, we develop a framework to estimate the lower bound for accurate diameter estimation, which we refer to as the resolution limit. We analyse only the contribution from the intra-axonal space and assume that axons can be represented by impermeable cylinders. To address the growing interest in using techniques for diffusion encoding that go beyond the conventional single diffusion encoding (SDE) sequence, we present a generalised... (More)

Diffusion MRI has been proposed as a non-invasive technique for axonal diameter mapping. However, accurate estimation of small diameters requires strong gradients, which is a challenge for the transition of the technique from preclinical to clinical MRI scanners, since these have weaker gradients. In this work, we develop a framework to estimate the lower bound for accurate diameter estimation, which we refer to as the resolution limit. We analyse only the contribution from the intra-axonal space and assume that axons can be represented by impermeable cylinders. To address the growing interest in using techniques for diffusion encoding that go beyond the conventional single diffusion encoding (SDE) sequence, we present a generalised analysis capable of predicting the resolution limit regardless of the gradient waveform. Using this framework, waveforms were optimised to minimise the resolution limit. The results show that, for parallel cylinders, the SDE experiment is optimal in terms of yielding the lowest possible resolution limit. In the presence of orientation dispersion, diffusion encoding sequences with square-wave oscillating gradients were optimal. The resolution limit for standard clinical MRI scanners (maximum gradient strength 60-80mT/m) was found to be between 4 and 8μm, depending on the noise levels and the level of orientation dispersion. For scanners with a maximum gradient strength of 300mT/m, the limit was reduced to between 2 and 5μm.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Axon diameter, Diffusion imaging, Double diffusion encoding, Microstructure, Oscillating diffusion encoding, Q-trajectory encoding, Resolution limit, Single diffusion encoding
in
NMR in Biomedicine
volume
30
issue
7
publisher
John Wiley & Sons
external identifiers
  • scopus:85016442509
  • wos:000405325100001
ISSN
0952-3480
DOI
10.1002/nbm.3711
language
English
LU publication?
yes
id
a94f24bc-4af8-4a54-b514-473e0ce02c93
date added to LUP
2017-04-19 10:58:40
date last changed
2018-05-27 04:41:28
@article{a94f24bc-4af8-4a54-b514-473e0ce02c93,
  abstract     = {<p>Diffusion MRI has been proposed as a non-invasive technique for axonal diameter mapping. However, accurate estimation of small diameters requires strong gradients, which is a challenge for the transition of the technique from preclinical to clinical MRI scanners, since these have weaker gradients. In this work, we develop a framework to estimate the lower bound for accurate diameter estimation, which we refer to as the resolution limit. We analyse only the contribution from the intra-axonal space and assume that axons can be represented by impermeable cylinders. To address the growing interest in using techniques for diffusion encoding that go beyond the conventional single diffusion encoding (SDE) sequence, we present a generalised analysis capable of predicting the resolution limit regardless of the gradient waveform. Using this framework, waveforms were optimised to minimise the resolution limit. The results show that, for parallel cylinders, the SDE experiment is optimal in terms of yielding the lowest possible resolution limit. In the presence of orientation dispersion, diffusion encoding sequences with square-wave oscillating gradients were optimal. The resolution limit for standard clinical MRI scanners (maximum gradient strength 60-80mT/m) was found to be between 4 and 8μm, depending on the noise levels and the level of orientation dispersion. For scanners with a maximum gradient strength of 300mT/m, the limit was reduced to between 2 and 5μm.</p>},
  articleno    = {e3711},
  author       = {Nilsson, Markus and Lasič, Samo and Drobnjak, Ivana and Topgaard, Daniel and Westin, Carl-Fredrik},
  issn         = {0952-3480},
  keyword      = {Axon diameter,Diffusion imaging,Double diffusion encoding,Microstructure,Oscillating diffusion encoding,Q-trajectory encoding,Resolution limit,Single diffusion encoding},
  language     = {eng},
  number       = {7},
  publisher    = {John Wiley & Sons},
  series       = {NMR in Biomedicine},
  title        = {Resolution limit of cylinder diameter estimation by diffusion MRI : The impact of gradient waveform and orientation dispersion},
  url          = {http://dx.doi.org/10.1002/nbm.3711},
  volume       = {30},
  year         = {2017},
}