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Beyond BOLD: Quantitative functional MRI without vascular proxy exploiting dynamic microstructure changes at neuronal level

English title Beyond BOLD: Quantitative functional MRI without vascular proxy exploiting dynamic microstructure changes at neuronal level
Applicant Jelescu Ileana
Number 190882
Funding scheme Spark
Research institution Module de recherche en technologies d'IRM EPFL - SB - CIBM-AIT
Institution of higher education EPF Lausanne - EPFL
Main discipline Other disciplines of Physics
Start/End 01.02.2020 - 31.05.2021
Approved amount 101'583.00
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All Disciplines (4)

Discipline
Other disciplines of Physics
Neurophysiology and Brain Research
Electrical Engineering
Biophysics

Keywords (7)

neurovascular coupling; functional connectivity; quantitative fMRI; diffusion fMRI; dynamic microstructure; functional MRI; non-BOLD fMRI

Lay Summary (French)

Lead
L’imagerie par résonance magnétique fonctionnelle (IRMf) permet de détecter l’activité du cerveau, par exemple quelles régions du cerveau sont utilisées pour une certaine tâche, ou quelles sont les régions qui communiquent entre elles quand vous ne pensez « à rien ». Cependant la technique utilisée jusqu’à maintenant pour l’IRMf, appelée BOLD (Blood Oxygenation Level Dependent, en anglais) est une technique indirecte qui détecte une demande plus importante en oxygène de la région activée, et non directement l’activité des neurones.
Lay summary
Dans cette étude, nous nous intéressons à une technique d’IRMf, appelée IRMf de diffusion, qui permettrait d’être directement sensible à l’activité des neurones, et non à la quantité d’oxygène dans le sang. Cette technique est fondée sur le fait que l'activité neuronale se traduit également par des modifications microstructurelles transitoires des neurones (e.g. gonflement cellulaire) auxquelles la diffusion des molécules d'eau est sensible.

Notre objectif est de déterminer si on peut obtenir un contraste fonctionnel en diffusion qui soit fondamentalement différent du BOLD et détectable à l'échelle de l'individu. Pour cela, nous utilisons une séquence IRM qui élimine un maximum de sources de contraste BOLD, et nous nous intéressons aux différences de connectivité fonctionnelle entre dfMRI et BOLD ainsi qu'à la dépendance en champ magnétique.

La validation d'une technique d'IRM fonctionnelle directement sensible à l'activité des neurones permettra, contrairement au contraste BOLD, de distinguer entre une affection neuronale ou vasculaire dans le cas de pathologies. De manière générale, l'IRMf de diffusion pourrait révolutionner les études sur le fonctionnement normal et dysfonctionnement du cerveau en proposant un contraste fonctionnel beaucoup plus "précis" que le contraste BOLD.
Direct link to Lay Summary Last update: 06.01.2020

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Beyond BOLD: in search of genuine diffusion fMRI contrast in human brain
Olszowy Wiktor, Diao Yujian, Jelescu Ileana O (2021), Beyond BOLD: in search of genuine diffusion fMRI contrast in human brain, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA.

Datasets

diffusion_fMRI

Author Olszowy, Wiktor; Jelescu, Ileana
Publication date 31.05.2021
Persistent Identifier (PID) https://openneuro.org/datasets/ds003676/versions/1.0.0
Repository OpenNeuro


Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
2021 Annual Meeting of the International Society for Magnetic Resonance in Medicine Talk given at a conference Beyond BOLD: in search of genuine diffusion fMRI contrast in human brain 15.05.2021 Virtual Meeting (Covid), Canada Olszowy Wiktor; Jelescu Ileana;
2020 Annual Meeting of the European Society for Magnetic Resonance in Medicine and Biology Talk given at a conference Does water diffusion increase or decrease following stimulation? 30.09.2020 Virtual meeting (Covid), Spain Jelescu Ileana; Olszowy Wiktor;


Awards

Title Year
"Best Diffusion Methods Abstract" award of the ISMRM Diffusion Study Group 2021
"Magna cum Laude" Merit Award of the ISMRM 2021

Abstract

Functional MRI (fMRI) has become an invaluable tool for neuroscience and is nearly omnipresent in studies of healthy and diseased brain. The major drawback of fMRI - in its currently most widespread implementation - is that the contrast stems from changes in venous blood oxygenation underlying neural activity, also known as BOLD (Blood Oxygenation Level Dependent) signal, instead of direct neural activity. This reliance on neurovascular coupling implies BOLD fMRI intrinsically suffers from poor spatial and temporal specificity to neuronal activation, and is challenging to quantify and compare to EEG or electrophysiology measurements. Diffusion fMRI (dfMRI) was proposed as a non-BOLD technique that overcomes these limitations: it relies on dynamic microstructural changes driven by neural activity, such as cell swelling, to induce changes in the diffusivity of water molecules on-site. Since the method has been proposed, a body of conflicting evidence has been published. Several studies have shown improved temporal and spatial specificity to neural activity in dfMRI compared to BOLD. Others have on the contrary shown that the so-called dfMRI signal was in fact contaminated by residual BOLD signal. The sensitivity of the method to detect physiological levels of brain activity has also been questioned. Studies on both sides suffered however from experimental shortcomings, leaving the debate open. Here, we propose to assert the existence - or absence - of genuine diffusion fMRI contrast detectable in the human brain at the individual level. Our approach consists in the following: a) The implementation of a diffusion fMRI acquisition that suppresses the main sources of residual BOLD contamination. b) Comparing not only task response but also resting-state functional connectivity estimated from dfMRI and BOLD fMRI acquisitions. c) Examining the effect of field strength on dfMRI. Should genuine diffusion fMRI contrast be detectable in the human brain on a clinical scanner, this will open the way for an accessible fMRI method which does not rely on neurovascular coupling but which is directly sensitive to neural activity. The availability of such a technique is becoming critical to separate between altered neuronal activity and vascular impairment and advance the understanding of neurodegenerative diseases. Diffusion fMRI can therefore revolutionize our ability to characterize both normal brain function and disease.
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