The variability of diffusion-relaxation multidimensional MRI estimates in the human brain

Motivation: Multidimensional (MD)-MRI provides valuable subvoxel information. However, its experimental variability has never been investigated. Goal(s): Assessing the variability of MD-MRI estimates is essential for adaptation to clinical research and widespread use. Approach: Ten healthy participants were each scanned twice, using a 40-minute 2-mm3 resolution diffusion-relaxation MD-MRI protocol. Agreement, reliability, and repeatability were assessed using Bland-Altman plots, intraclass correlation coefficient, and test-retest variability, respectively. Results: We demonstrated a good to excellent reliability in the quantification of first- and second-order diffusion parameters. Our findings guide further improvement to the protocol and encourage the use of this MD-MRI framework in clinical research. Impact: Multidimensional MRI is crucial for investigating tissue microstructure, brain connectivity, and pathology. Here we present an in vivo variability study that shows strong agreement, reliability, and repeatability, especially for diffusion parameters, providing a way forward for clinical research.