Estimating axon radius using diffusion-relaxation MRI: calibrating a surface-based relaxation model with histology.
Details
Serval ID
serval:BIB_2971ED6B2DF4
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Estimating axon radius using diffusion-relaxation MRI: calibrating a surface-based relaxation model with histology.
Journal
Frontiers in neuroscience
ISSN
1662-4548 (Print)
ISSN-L
1662-453X
Publication state
Published
Issued date
2023
Peer-reviewed
Oui
Volume
17
Pages
1209521
Language
english
Notes
Publication types: Journal Article
Publication Status: epublish
Publication Status: epublish
Abstract
Axon radius is a potential biomarker for brain diseases and a crucial tissue microstructure parameter that determines the speed of action potentials. Diffusion MRI (dMRI) allows non-invasive estimation of axon radius, but accurately estimating the radius of axons in the human brain is challenging. Most axons in the brain have a radius below one micrometer, which falls below the sensitivity limit of dMRI signals even when using the most advanced human MRI scanners. Therefore, new MRI methods that are sensitive to small axon radii are needed. In this proof-of-concept investigation, we examine whether a surface-based axonal relaxation process could mediate a relationship between intra-axonal T <sub>2</sub> and T <sub>1</sub> times and inner axon radius, as measured using postmortem histology. A unique in vivo human diffusion-T <sub>1</sub> -T <sub>2</sub> relaxation dataset was acquired on a 3T MRI scanner with ultra-strong diffusion gradients, using a strong diffusion-weighting (i.e., b = 6,000 s/mm <sup>2</sup> ) and multiple inversion and echo times. A second reduced diffusion-T <sub>2</sub> dataset was collected at various echo times to evaluate the model further. The intra-axonal relaxation times were estimated by fitting a diffusion-relaxation model to the orientation-averaged spherical mean signals. Our analysis revealed that the proposed surface-based relaxation model effectively explains the relationship between the estimated relaxation times and the histological axon radius measured in various corpus callosum regions. Using these histological values, we developed a novel calibration approach to predict axon radius in other areas of the corpus callosum. Notably, the predicted radii and those determined from histological measurements were in close agreement.
Keywords
T1 relaxation, T2 relaxation, axon radius, brain, diffusion MRI, histology
Pubmed
Web of science
Open Access
Yes
Create date
19/09/2023 11:29
Last modification date
25/01/2024 7:32