Scan-rescan repeatability of axonal imaging metrics using high-gradient diffusion MRI and statistical implications...

Area of Science:

• Neuroimaging
• Biophysics
• Neuroscience

Background:

• Diffusion MRI is increasingly used for mapping axon diameter in the living brain.
• High gradient strengths enhance the precision of these measurements.
• Assessing the consistency of axon diameter estimates is crucial for neurobiological studies.

Purpose of the Study:

• To evaluate the scan-rescan repeatability of axon diameter index estimation using high-gradient diffusion MRI.
• To determine the implications of this consistency for designing neurobiological studies.
• To make high-gradient diffusion MRI data publicly available.

Main Methods:

• Diffusion MRI data were acquired using gradient strengths up to 300 mT/m on a 3T Connectom system.
• The spherical mean technique (SMT) was used for axon diameter index estimation.
• Statistical power analyses were performed on data from 15 healthy adults.

Main Results:

• High repeatability was observed for voxel-wise restricted volume fraction and tract-wise axon diameter index.
• Region of interest analysis showed a Pearson's correlation coefficient of r=0.72 for axon diameter index between scans.
• Sample sizes of less than 15 individuals were sufficient for detecting a 10% effect size in most white matter regions.

Conclusions:

• High-gradient diffusion MRI provides repeatable axon diameter index estimates in the human brain.
• The findings support the use of this technique for neurobiological studies with modest sample sizes.
• Publicly sharing the acquired data will advance open science in neuroimaging research.