Publications by Tim Bjørn Dyrby

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

Jean-Philippe Thiran, Muhamed Barakovic, Erick Jorge Canales Rodriguez, Marco Pizzolato, 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 ...

Wiley2024

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

Editorial: Computational Neuroimage Analysis Tools for Brain (Diseases) Biomarkers

Meritxell Bach Cuadra, Tim Bjørn Dyrby

FRONTIERS MEDIA SA2022

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

Jean-Philippe Thiran, Giorgio Innocenti, Gabriel Girard, Maxime Descoteaux, 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

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

Jean-Philippe Thiran, Jonathan Rafael Patino Lopez, 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 ...

National Academy of Sciences2020

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

Jean-Philippe Thiran, Graham Knott, Giorgio Innocenti, Maxime Descoteaux, 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

Topological principles and developmental algorithms might refine diffusion tractography

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

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, Jonathan Rafael Patino Lopez, 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 ...

Wiley2020

Validation strategies for the interpretation of microstructure imaging using diffusion MRI

Giorgio Innocenti, Tim Bjørn Dyrby

Extracting microanatomical information beyond the image resolution of MRI would provide valuable tools for diagnostics and neuroscientific research. A number of mathematical models already suggest microstructural interpretations of diffusion MRI (dMRI) dat ...

2018

Voxel size matters: big voxels are required to generate realistic extra-axonal dMRI signals from Monte Carlo simulations

Jean-Philippe Thiran, David Paul Roger Romascano, Alessandro Daducci, Muhamed Barakovic, Ileana Ozana Jelescu, Jonathan Rafael Patino Lopez, Tim Bjørn Dyrby

2018

Non-parametric axon diameter distribution mapping with PGSE: reconstruction of uni- and multimodal distributions

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

2018

The Crossed Projection to the Striatum in Two Species of Monkey and in Humans: Behavioral and Evolutionary Significance

Giorgio Innocenti, Tim Bjørn Dyrby

The corpus callosum establishes the anatomical continuity between the 2 hemispheres and coordinates their activity. Using histological tracing, single axon reconstructions, and diffusion tractography, we describe a callosal projection to n caudatus and put ...

Oxford University Press2017

Orientation invariant and non-parametric Axon Diameter Distribution mapping using PGSE and regularized discrete linear modeling

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

Axon Diameter Distributions (ADDs) change during brain development and are altered in several brain pathologies. Mapping ADDs non-invasively using dMRI could provide a useful biomarker, but existing methods are either parametric, orientation dependent, sur ...

2017

Reducing acquisition time for axon diameter mapping using global optimization in the spatial-angular-microstructure space

Jean-Philippe Thiran, Yves Wiaux, David Paul Roger Romascano, Alessandro Daducci, Anna Auria Rasclosa, Erick Jorge Canales Rodriguez, Tim Bjørn Dyrby

State-of-the-art microstructure imaging methods usually fit biophysical models to the diffusion MRI data on a voxel-by-voxel basis using non-linear procedures that require both long acquisitions and processing time. We recently introduced AMICO, a framewor ...

2016

Reducing acquisition time for microstructure imaging with spatially-regularized global optimization

Jean-Philippe Thiran, Yves Wiaux, David Paul Roger Romascano, Alessandro Daducci, Anna Auria Rasclosa, Erick Jorge Canales Rodriguez, Tim Bjørn Dyrby

Microstructure imaging with diffusion MRI (dMRI) is usually based on fitting models to the data using voxelwise nonlinear procedures that (i) are time consuming and (ii) need long acquisitions. Recently, we introduced the AMICO framework to accelerate the ...

2016

Accelerated Microstructure Imaging via Convex Optimization (AMICO) from diffusion MRI data

Jean-Philippe Thiran, Alessandro Daducci, Hui Zhang, Erick Jorge Canales Rodriguez, Tim Bjørn Dyrby

Microstructure imaging from diffusion magnetic resonance (MR) data represents an invaluable tool to study non-invasively the morphology of tissues and to provide a biological insight into their microstructural organization. In recent years, a variety of bi ...

Elsevier2015

Accelerated Microstructure Imaging via Convex Optimization (AMICO) in crossing fibers

Jean-Philippe Thiran, Yves Wiaux, Alessandro Daducci, Anna Auria Rasclosa, Erick Jorge Canales Rodriguez, Tim Bjørn Dyrby

Mapping the local microstructure properties of the tissue in the brain is crucial to understand any pathological condition from a biological perspective. In recent years, microstructure-imaging techniques aimed at extracting such precious information by us ...

2015