# Characterization of neurite and soma organization in the brain and spinal cord with diffusion MRI

Kurt G. Schilling, Marco Palombo, Atlee A. Witt, Kristin P. O’Grady, Marco Pizzolato, Bennett A. Landman, Seth A. Smith

Imaging Neuroscience · 2025 · Article

https://doi.org/10.1162/imag.a.111

## Summary

A shared 3T diffusion MRI protocol characterizes brain and spinal cord microstructure using DTI, Standard Model Imaging, and SANDI. The study evaluates image quality, tissue contrast, and repeatability across the neuroaxis. It establishes the feasibility of combined measurements while identifying greater reproducibility and partial volume challenges in the cord.

## Study overview

Brain and spinal cord microstructure are often studied separately despite their close anatomical and functional relationships. This work implements a clinically feasible 3T diffusion protocol that supports diffusion tensor imaging, Standard Model Imaging, and Soma and Neurite Density Imaging across both structures. The authors evaluate image quality, regional contrasts, and reproducibility, including the first assessment of SMI and SANDI in the spinal cord reported by the study. Most model-derived metrics show repeatability comparable to DTI, although spinal cord contrasts and reproducibility are generally weaker than in the brain. The protocol offers a harmonized basis for studies across the central nervous system.

## Findings / topics

- Evaluates DTI, SMI, and SANDI in both brain and spinal cord.
- Most SMI and SANDI metrics have reproducibility comparable to DTI.
- Cord measurements face greater partial volume and preprocessing challenges.

## Resources

- [Original work](https://direct.mit.edu/imag/article/doi/10.1162/IMAG.a.111/132048/Characterization-of-neurite-and-soma-organization)
- [PDF](https://pmc.ncbi.nlm.nih.gov/articles/PMC12365691/pdf/imag-3-111.pdf)
- [Open full text](https://pmc.ncbi.nlm.nih.gov/articles/PMC12365691/)

Lab page: https://www.microstructure-connectivity-lab.com/publications/neurite-soma-brain-cord/

This is a research summary, not the full article.