Scan-Rescan Repeatability of Axon Diameter Mapping Metrics from Ultra-High-Gradient Diffusion MRI on the Connectome 2.0 Scanner

Motivation: Enhancing MRI reliability improves understanding of brain microstructure and disorders Goal(s): This study aims to evaluate the reliability and repeatability of ultra-high-gradient diffusion MRI metrics, specifically focusing on the axon diameter index and restricted volume fraction. Approach: Using a 3T Connectome2.0 scanner, five healthy adults participated in two scanning sessions to assess the scan-rescan reliability of axonal microstructural metrics. Results: The findings revealed high correlation coefficients for fractional anisotropy and restricted volume fraction (r=0.96), with the axon diameter index showing improved correlation compared to the original Connectome scanner. These results confirm that ultra-high-gradient diffusion MRI provides robust scan-rescan reliability for assessing axonal microstructure. Impact: This research enhances the understanding of diffusion-MRI metrics' reliability, enabling more accurate studies of brain microstructure. It supports further investigation into neurobiological differences across populations and potential clinical applications.