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Motion-compensated b-tensor encoding for in vivo cardiac diffusion-weighted imaging

Lasič, Samo ; Szczepankiewicz, Filip LU ; Dall'Armellina, Erica ; Das, Arka ; Kelly, Christopher ; Plein, Sven ; Schneider, Jürgen E. ; Nilsson, Markus LU and Teh, Irvin (2020) In NMR in Biomedicine 33(2).
Abstract

Motion is a major confound in diffusion-weighted imaging (DWI) in the body, and it is a common cause of image artefacts. The effects are particularly severe in cardiac applications, due to the nonrigid cyclical deformation of the myocardium. Spin echo-based DWI commonly employs gradient moment-nulling techniques to desensitise the acquisition to velocity and acceleration, ie, nulling gradient moments up to the 2nd order (M2-nulled). However, current M2-nulled DWI scans are limited to encode diffusion along a single direction at a time. We propose a method for designing b-tensors of arbitrary shapes, including planar, spherical, prolate and oblate tensors, while nulling gradient moments up to the 2nd order and beyond. The design strategy... (More)

Motion is a major confound in diffusion-weighted imaging (DWI) in the body, and it is a common cause of image artefacts. The effects are particularly severe in cardiac applications, due to the nonrigid cyclical deformation of the myocardium. Spin echo-based DWI commonly employs gradient moment-nulling techniques to desensitise the acquisition to velocity and acceleration, ie, nulling gradient moments up to the 2nd order (M2-nulled). However, current M2-nulled DWI scans are limited to encode diffusion along a single direction at a time. We propose a method for designing b-tensors of arbitrary shapes, including planar, spherical, prolate and oblate tensors, while nulling gradient moments up to the 2nd order and beyond. The design strategy comprises initialising the diffusion encoding gradients in two encoding blocks about the refocusing pulse, followed by appropriate scaling and rotation, which further enables nulling undesired effects of concomitant gradients. Proof-of-concept assessment of in vivo mean diffusivity (MD) was performed using linear and spherical tensor encoding (LTE and STE, respectively) in the hearts of five healthy volunteers. The results of the M2-nulled STE showed that (a) the sequence was robust to cardiac motion, and (b) MD was higher than that acquired using standard M2-nulled LTE, where diffusion-weighting was applied in three orthogonal directions, which may be attributed to the presence of restricted diffusion and microscopic diffusion anisotropy. Provided adequate signal-to-noise ratio, STE could significantly shorten estimation of MD compared with the conventional LTE approach. Importantly, our theoretical analysis and the proposed gradient waveform design may be useful in microstructure imaging beyond diffusion tensor imaging where the effects of motion must be suppressed.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
acceleration nulling, b-tensor encoding, cardiac MRI, concomitant field, isotropic diffusion weighting, motion compensation, velocity nulling
in
NMR in Biomedicine
volume
33
issue
2
article number
e4213
publisher
John Wiley & Sons
external identifiers
  • pmid:31765063
  • scopus:85075461821
ISSN
0952-3480
DOI
10.1002/nbm.4213
language
English
LU publication?
yes
id
f72a01c2-9040-477a-8ffe-0dfda027ce58
date added to LUP
2019-12-10 08:57:28
date last changed
2020-02-10 16:35:45
@article{f72a01c2-9040-477a-8ffe-0dfda027ce58,
  abstract     = {<p>Motion is a major confound in diffusion-weighted imaging (DWI) in the body, and it is a common cause of image artefacts. The effects are particularly severe in cardiac applications, due to the nonrigid cyclical deformation of the myocardium. Spin echo-based DWI commonly employs gradient moment-nulling techniques to desensitise the acquisition to velocity and acceleration, ie, nulling gradient moments up to the 2nd order (M2-nulled). However, current M2-nulled DWI scans are limited to encode diffusion along a single direction at a time. We propose a method for designing b-tensors of arbitrary shapes, including planar, spherical, prolate and oblate tensors, while nulling gradient moments up to the 2nd order and beyond. The design strategy comprises initialising the diffusion encoding gradients in two encoding blocks about the refocusing pulse, followed by appropriate scaling and rotation, which further enables nulling undesired effects of concomitant gradients. Proof-of-concept assessment of in vivo mean diffusivity (MD) was performed using linear and spherical tensor encoding (LTE and STE, respectively) in the hearts of five healthy volunteers. The results of the M2-nulled STE showed that (a) the sequence was robust to cardiac motion, and (b) MD was higher than that acquired using standard M2-nulled LTE, where diffusion-weighting was applied in three orthogonal directions, which may be attributed to the presence of restricted diffusion and microscopic diffusion anisotropy. Provided adequate signal-to-noise ratio, STE could significantly shorten estimation of MD compared with the conventional LTE approach. Importantly, our theoretical analysis and the proposed gradient waveform design may be useful in microstructure imaging beyond diffusion tensor imaging where the effects of motion must be suppressed.</p>},
  author       = {Lasič, Samo and Szczepankiewicz, Filip and Dall'Armellina, Erica and Das, Arka and Kelly, Christopher and Plein, Sven and Schneider, Jürgen E. and Nilsson, Markus and Teh, Irvin},
  issn         = {0952-3480},
  language     = {eng},
  number       = {2},
  publisher    = {John Wiley & Sons},
  series       = {NMR in Biomedicine},
  title        = {Motion-compensated b-tensor encoding for in vivo cardiac diffusion-weighted imaging},
  url          = {http://dx.doi.org/10.1002/nbm.4213},
  doi          = {10.1002/nbm.4213},
  volume       = {33},
  year         = {2020},
}