Anisotropy in "isotropic diffusion" measurements due to nongaussian diffusion

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Anisotropy in "isotropic diffusion" measurements due to nongaussian diffusion. / Jespersen, Sune Nørhøj; Olesen, Jonas Lynge; Ianuş, Andrada; Shemesh, Noam.

In: arXiv preprint, 06.12.2017.

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@article{055a15af7a0a4cea92526a2f36dd03d5,
title = "Anisotropy in {"}isotropic diffusion{"} measurements due to nongaussian diffusion",
abstract = "Designing novel diffusion-weighted NMR and MRI pulse sequences aiming to probe tissue microstructure with techniques extending beyond the conventional Stejskal-Tanner family is currently of broad interest. One such technique, multidimensional diffusion MRI, has been recently proposed to afford model-free decomposition of diffusion signal kurtosis into terms originating from either ensemble variance of isotropic diffusivity or microscopic diffusion anisotropy. This ability rests on the assumption that diffusion can be described as a sum of multiple Gaussian compartments, but this is often not strictly fulfilled. Nevertheless, the effects of nongaussian diffusion has not been considered in detail so far. Here we analyze and demonstrate at least two significant consequences of deviations from the multiple Gaussian compartments systems. First, anisotropic compartments lead to anisotropic time dependence of the diffusion tensors, which causes the measured isotropic diffusivity to depend on gradient frame orientation. In turn, this conflates orientation dispersion with ensemble variance in isotropic diffusivity. Second, additional contributions to the apparent variance in isotropic diffusivity arise due to intracompartmental kurtosis, regardless of diffusion weighting. These will likewise depend on gradient frame orientation. We illustrate the potential importance of these confounds with analytical expressions, numerical simulations and experiments in spinal cord.",
keywords = "physics.bio-ph",
author = "Jespersen, {Sune N{\o}rh{\o}j} and Olesen, {Jonas Lynge} and Andrada Ianuş and Noam Shemesh",
note = "22 pages, 7 figures",
year = "2017",
month = "12",
day = "6",
language = "English",
journal = "arXiv preprint",

}

RIS

TY - JOUR

T1 - Anisotropy in "isotropic diffusion" measurements due to nongaussian diffusion

AU - Jespersen,Sune Nørhøj

AU - Olesen,Jonas Lynge

AU - Ianuş,Andrada

AU - Shemesh,Noam

N1 - 22 pages, 7 figures

PY - 2017/12/6

Y1 - 2017/12/6

N2 - Designing novel diffusion-weighted NMR and MRI pulse sequences aiming to probe tissue microstructure with techniques extending beyond the conventional Stejskal-Tanner family is currently of broad interest. One such technique, multidimensional diffusion MRI, has been recently proposed to afford model-free decomposition of diffusion signal kurtosis into terms originating from either ensemble variance of isotropic diffusivity or microscopic diffusion anisotropy. This ability rests on the assumption that diffusion can be described as a sum of multiple Gaussian compartments, but this is often not strictly fulfilled. Nevertheless, the effects of nongaussian diffusion has not been considered in detail so far. Here we analyze and demonstrate at least two significant consequences of deviations from the multiple Gaussian compartments systems. First, anisotropic compartments lead to anisotropic time dependence of the diffusion tensors, which causes the measured isotropic diffusivity to depend on gradient frame orientation. In turn, this conflates orientation dispersion with ensemble variance in isotropic diffusivity. Second, additional contributions to the apparent variance in isotropic diffusivity arise due to intracompartmental kurtosis, regardless of diffusion weighting. These will likewise depend on gradient frame orientation. We illustrate the potential importance of these confounds with analytical expressions, numerical simulations and experiments in spinal cord.

AB - Designing novel diffusion-weighted NMR and MRI pulse sequences aiming to probe tissue microstructure with techniques extending beyond the conventional Stejskal-Tanner family is currently of broad interest. One such technique, multidimensional diffusion MRI, has been recently proposed to afford model-free decomposition of diffusion signal kurtosis into terms originating from either ensemble variance of isotropic diffusivity or microscopic diffusion anisotropy. This ability rests on the assumption that diffusion can be described as a sum of multiple Gaussian compartments, but this is often not strictly fulfilled. Nevertheless, the effects of nongaussian diffusion has not been considered in detail so far. Here we analyze and demonstrate at least two significant consequences of deviations from the multiple Gaussian compartments systems. First, anisotropic compartments lead to anisotropic time dependence of the diffusion tensors, which causes the measured isotropic diffusivity to depend on gradient frame orientation. In turn, this conflates orientation dispersion with ensemble variance in isotropic diffusivity. Second, additional contributions to the apparent variance in isotropic diffusivity arise due to intracompartmental kurtosis, regardless of diffusion weighting. These will likewise depend on gradient frame orientation. We illustrate the potential importance of these confounds with analytical expressions, numerical simulations and experiments in spinal cord.

KW - physics.bio-ph

M3 - Journal article

JO - arXiv preprint

T2 - arXiv preprint

JF - arXiv preprint

ER -