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Updated: May 9, 2025
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In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging
Published on: September 2, 2016
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Evaluation of diffusion time-dependent changes in radial diffusivity as a surrogate for axon diameter.
Hannah E Alderson1,2, Mark D Does1,2,3,4, Elizabeth B Hutchinson5
1Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
Magnetic Resonance in Medicine
|April 28, 2025
Summary
Diffusion time (τ) in MRI is a reliable and simple method for estimating axon diameter in ex vivo spinal cords. This finding holds true irrespective of myelin content variations, offering a valuable tool for neuroscience research.
Area of Science:
- Neuroscience
- Biophysics
- Medical Imaging
Background:
- Axon diameter is a critical parameter in neuroscience.
- Current methods for measuring axon diameter are often invasive or complex.
- Diffusion MRI offers a non-invasive potential for estimating microstructural properties.
Purpose of the Study:
- To investigate the relationship between diffusion time (τ) in MRI and axon diameter.
- To determine if τ can serve as a simple estimate of axon diameter.
- To assess the influence of myelin content on this estimation.
Main Methods:
- Ex vivo ferret spinal cords were utilized for imaging.
- Magnetic Resonance Imaging (MRI) and scanning electron microscopy (SEM) were employed.
- Region-of-interest analysis compared MRI-derived τ with SEM-derived area-weighted mean axon diameter (d).
Main Results:
- A strong linear correlation was observed between diffusion time (τ) and axon diameter (d).
- Negative correlations were found between myelin water fraction and τ.
- Negative correlations were also observed between bound pool fraction and τ.
Conclusions:
- Diffusion time (τ) is a robust and simple estimator of axon size in ex vivo spinal cord tissue.
- This estimation is independent of variations in myelin content, as confirmed by quantitative MRI.
- The findings support the use of diffusion time MRI for non-invasive axon diameter assessment.
