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Tim Bjørn Dyrby

Publications associées (20)

Pore size estimation in axon-mimicking microfibers with diffusion-relaxation MRI

Jean-Philippe Thiran, Erick Jorge Canales Rodriguez, Marco Pizzolato, Muhamed Barakovic, Tim Bjørn Dyrby

Purpose: This study aims to evaluate two distinct approaches for fiber radius estimation using diffusion-relaxation MRI data acquired in biomimetic microfiber phantoms that mimic hollow axons. The methods considered are the spherical mean power-law approac ...
Hoboken2024

Axial and radial axonal diffusivities and radii from single encoding strongly diffusion-weighted MRI

Erick Jorge Canales Rodriguez, Marco Pizzolato, Tim Bjørn Dyrby

We enable the estimation of the per-axon axial diffusivity from single encoding, strongly diffusion-weighted, pulsed gradient spin echo data. Additionally, we improve the estimation of the per-axon radial diffusivity compared to estimates based on spherica ...
ELSEVIER2023

Does powder averaging remove dispersion bias in diffusion MRI diameter estimates within real 3D axonal architectures?

Marco Pizzolato, Tim Bjørn Dyrby

Noninvasive estimation of axon diameter with diffusion MRI holds the potential to investigate the dynamic properties of the brain network and pathology of neurodegenerative diseases. Recent studies use powder averaging to account for complex white matter a ...
ACADEMIC PRESS INC ELSEVIER SCIENCE2022

Axon morphology is modulated by the local environment and impacts the noninvasive investigation of its structure-function relationship

Jean-Philippe Thiran, Tim Bjørn Dyrby

Axonal conduction velocity, which ensures efficient function of the brain network, is related to axon diameter. Noninvasive, in vivo axon diameter estimates can be made with diffusion magnetic resonance imaging, but the technique requires three-dimensional ...
NATL ACAD SCIENCES2020

On the cortical connectivity in the macaque brain: A comparison of diffusion tractography and histological tracing data

Jean-Philippe Thiran, Gabriel Girard, Maxime Descoteaux, Giorgio Innocenti, Tim Bjørn Dyrby

Diffusion-weighted magnetic resonance imaging (DW-MRI) tractography is a non-invasive tool to probe neural connections and the structure of the white matter. It has been applied successfully in studies of neurological disorders and normal connectivity. Rec ...
2020

Diversity of Cortico-descending Projections: Histological and Diffusion MRI Characterization in the Monkey

Jean-Philippe Thiran, Graham Knott, Maxime Descoteaux, Giorgio Innocenti, Tim Bjørn Dyrby

The axonal composition of cortical projections originating in premotor, supplementary motor (SMA), primary motor (a4), somatosensory and parietal areas and descending towards the brain stem and spinal cord was characterized in the monkey with histological ...
OXFORD UNIV PRESS INC2019

ActiveAx(ADD): Toward non-parametric and orientationally invariant axon diameter distribution mapping using PGSE

Jean-Philippe Thiran, David Paul Roger Romascano, Alessandro Daducci, Muhamed Barakovic, Tim Bjørn Dyrby

Purpose Non-invasive axon diameter distribution (ADD) mapping using diffusion MRI is an ill-posed problem. Current ADD mapping methods require knowledge of axon orientation before performing the acquisition. Instead, ActiveAx uses a 3D sampling scheme to e ...
2019

HOTmix: characterizing hindered diffusion using a mixture of generalized higher order tensors

Jean-Philippe Thiran, Erick Jorge Canales Rodriguez, Gabriel Girard, David Paul Roger Romascano, Marco Pizzolato, Jonathan Rafael Patino Lopez, Alessandro Daducci, Muhamed Barakovic, Gaëtan Olivier D Rensonnet, Tim Bjørn Dyrby

We present HOTmix, a new model to describe the diffusion MRI signal for molecules undergoing hindered diffusion. HOTmix is based on a mixture of generalized higher order tensors, explicitly incorporating the diffusion sequence’s time-dependent parameters. ...
2019

Topological principles and developmental algorithms might refine diffusion tractography

Jean-Philippe Thiran, Gabriel Girard, Alessandro Daducci, Maxime Descoteaux, Giorgio Innocenti, Tim Bjørn Dyrby

The identification and reconstruction of axonal pathways in the living brain or “ex-vivo” is promising a revolution in connectivity studies bridging the gap from animal to human neuroanatomy with extensions to brain structural–functional correlates. Unfort ...
2019

Limits to anatomical accuracy of diffusion tractography using modern approaches

Jean-Philippe Thiran, Erick Jorge Canales Rodriguez, Gabriel Girard, David Paul Roger Romascano, Elda Fischi Gomez, Marco Pizzolato, Alessandro Daducci, Muhamed Barakovic, Maxime Descoteaux, Gaëtan Olivier D Rensonnet, Alice Philippa Bates, Tim Bjørn Dyrby, Chao Huang

Diffusion MRI fiber tractography is widely used to probe the structural connectivity of the brain, with a range of applications in both clinical and basic neuroscience. Despite widespread use, tractography has well-known pitfalls that limits the anatomical ...
2018

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