Comparative Systematic Analysis of Gray Matter Biophysical Models on a Public Dataset

Area of Science:

• Neuroimaging
• Diffusion MRI (dMRI)
• Biophysical modeling

Background:

• Gray matter (GM) microstructure characterization is advancing with biophysical diffusion models.
• NEXI, SMEX, SANDI, and SANDIX models account for soma contributions and inter-compartment exchange.
• Comparative evaluation of these advanced GM diffusion models is needed.

Purpose of the Study:

• To comparatively evaluate four advanced gray matter diffusion models: NEXI, SMEX, SANDI, and SANDIX.
• Assess model performance using a human in vivo dataset.
• Analyze goodness of fit, anatomical patterns, and consistency.

Main Methods:

• Utilized the Connectome Diffusion Microstructure Dataset (CDMD) with two diffusion times.
• Estimated cortical microstructure metrics in 26 healthy subjects using the Gray Matter Swiss Knife toolbox.
• Evaluated goodness of fit, anatomical patterns, and consistency with prior research.

Main Results:

• All four models yielded GM parameter estimates consistent with previous studies.
• NEXI and SMEX demonstrated similar cortical patterns and regional distributions across diffusion times.
• NEXI provided the best goodness of fit, followed by SMEX, SANDIX, and SANDI, which showed high dependence on diffusion time and fitting algorithm.

Conclusions:

• Estimating exchange models from two diffusion times is feasible.
• Model selection involves trade-offs between biological specificity, complexity, and fitting robustness.
• Findings guide the choice of GM diffusion models for clinical and research applications.