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Diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding

Diffusion MRI classically uses gradient fields that vary linearly in space to encode the diffusion of water molecules in the signal magnitude by tempering its intensity. In spin ensembles, a presumably equal number of particles move in positive and negative direction, resulting in approximately zero...

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Detalles Bibliográficos
Autores principales: Wochner, Pamela, Schneider, Torben, Stockmann, Jason, Lee, Jack, Sinkus, Ralph
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10062566/
https://www.ncbi.nlm.nih.gov/pubmed/36996066
http://dx.doi.org/10.1371/journal.pone.0281332
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author Wochner, Pamela
Schneider, Torben
Stockmann, Jason
Lee, Jack
Sinkus, Ralph
author_facet Wochner, Pamela
Schneider, Torben
Stockmann, Jason
Lee, Jack
Sinkus, Ralph
author_sort Wochner, Pamela
collection PubMed
description Diffusion MRI classically uses gradient fields that vary linearly in space to encode the diffusion of water molecules in the signal magnitude by tempering its intensity. In spin ensembles, a presumably equal number of particles move in positive and negative direction, resulting in approximately zero change in net phase. Hence, in classical diffusion weighted MRI with a linear gradient field, the phase does not carry any information as the incoherent motion of the spins only impacts the magnitude of the signal. Conversely, when the linear gradient field is replaced with one that varies quadratically over space, the diffusion of water molecules in anisotropic media does give rise to a change in net phase and preserves large portion of the signal around the saddle point of the gradient field. In this work, the phase evolution of anisotropic fibre phantoms in the presence of quadratic gradient fields was studied in Monte Carlo simulations and diffusion MRI experiments. The simulations confirm the dependence of the phase change on the degree of anisotropy of the media and the diffusion weighting, as predicted by the derived analytic model. First MR experiments show a phase change depending on the diffusion time in an anisotropic synthetic fibre phantom, and approximately zero phase change for the experiment repeated in an isotropic agar phantom. As predicted by the analytic model, an increase of the diffusion time by approximately a factor of two leads to an increase of approximately a factor of two in the signal phase.
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spelling pubmed-100625662023-03-31 Diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding Wochner, Pamela Schneider, Torben Stockmann, Jason Lee, Jack Sinkus, Ralph PLoS One Research Article Diffusion MRI classically uses gradient fields that vary linearly in space to encode the diffusion of water molecules in the signal magnitude by tempering its intensity. In spin ensembles, a presumably equal number of particles move in positive and negative direction, resulting in approximately zero change in net phase. Hence, in classical diffusion weighted MRI with a linear gradient field, the phase does not carry any information as the incoherent motion of the spins only impacts the magnitude of the signal. Conversely, when the linear gradient field is replaced with one that varies quadratically over space, the diffusion of water molecules in anisotropic media does give rise to a change in net phase and preserves large portion of the signal around the saddle point of the gradient field. In this work, the phase evolution of anisotropic fibre phantoms in the presence of quadratic gradient fields was studied in Monte Carlo simulations and diffusion MRI experiments. The simulations confirm the dependence of the phase change on the degree of anisotropy of the media and the diffusion weighting, as predicted by the derived analytic model. First MR experiments show a phase change depending on the diffusion time in an anisotropic synthetic fibre phantom, and approximately zero phase change for the experiment repeated in an isotropic agar phantom. As predicted by the analytic model, an increase of the diffusion time by approximately a factor of two leads to an increase of approximately a factor of two in the signal phase. Public Library of Science 2023-03-30 /pmc/articles/PMC10062566/ /pubmed/36996066 http://dx.doi.org/10.1371/journal.pone.0281332 Text en © 2023 Wochner et al https://creativecommons.org/licenses/by/4.0/This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Wochner, Pamela
Schneider, Torben
Stockmann, Jason
Lee, Jack
Sinkus, Ralph
Diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding
title Diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding
title_full Diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding
title_fullStr Diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding
title_full_unstemmed Diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding
title_short Diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding
title_sort diffusion phase-imaging in anisotropic media using non-linear gradients for diffusion encoding
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10062566/
https://www.ncbi.nlm.nih.gov/pubmed/36996066
http://dx.doi.org/10.1371/journal.pone.0281332
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