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- doi: 10.1016/j.mri.2021.11.012
- issn: 0730-725X
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info:eu-repo/semantics/altIdentifier/urn/urn:nbn:ch:serval-BIB_CD032BC9286C4
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M. Pizzolato et al., « Axonal T2 estimation using the spherical variance of the strongly diffusion-weighted MRI signal. », Serveur académique Lausannois, ID : 10.1016/j.mri.2021.11.012
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In magnetic resonance imaging, the application of a strong diffusion weighting suppresses the signal contributions from the less diffusion-restricted constituents of the brain's white matter, thus enabling the estimation of the transverse relaxation time T 2 that arises from the more diffusion-restricted constituents such as the axons. However, the presence of cell nuclei and vacuoles can confound the estimation of the axonal T 2 , as diffusion within those structures is also restricted, causing the corresponding signal to survive the strong diffusion weighting. We devise an estimator of the axonal T 2 based on the directional spherical variance of the strongly diffusion-weighted signal. The spherical variance T 2 estimates are insensitive to the presence of isotropic contributions to the signal like those provided by cell nuclei and vacuoles. We show that with a strong diffusion weighting these estimates differ from those obtained using the directional spherical mean of the signal which contains both axonal and isotropically-restricted contributions. Our findings hint at the presence of an MRI-visible isotropically-restricted contribution to the signal in the white matter ex vivo fixed tissue (monkey) at 7T, and do not allow us to discard such a possibility also for in vivo human data collected with a clinical 3T system.