Schilling, Kurt G., Palombo, Marco, Witt, Atlee A., O’Grady, Kristin P., Pizzolato, Marco, Landman, Bennett Allan, & Smith, Seth A. (2025). Characterization of neurite and soma organization in the brain and spinal cord with diffusion MRI. Imaging Neuroscience, 3, IMAG.a.111. https://doi.org/10.1162/IMAG.a.111
The central nervous system [CNS], which includes the brain and spinal cord, is made up of white and gray matter and is responsible for sensory, motor, and cognitive functions. Advanced diffusion MRI (dMRI) techniques provide a way to study the structure of the CNS without invasive procedures, but most research has focused on either the brain or the spinal cord alone. In this study, we used a clinically practical dMRI protocol on a 3T scanner to examine the microstructure of both neurites and somas in the brain and spinal cord at the same time. The protocol allowed us to apply Diffusion Tensor Imaging (DTI), Standard Model Imaging (SMI), and Soma and Neurite Density Imaging (SANDI). This is the first time SMI and SANDI have been tested in the spinal cord, as well as in both the cord and brain simultaneously.
Our findings show that we were able to achieve high image quality, even with high diffusion weightings, and that the measurements from SMI and SANDI were reproducible in ways similar to DTI, with only a few exceptions. We also found biologically meaningful contrasts between and within white and gray matter regions. However, reproducibility and contrast were lower in the spinal cord compared to the brain, partly due to partial volume effects and image preprocessing challenges. Overall, this study introduces a unified method for imaging both the brain and spinal cord, opening new opportunities to study CNS diseases and identify biomarkers of structural integrity across the entire neuroaxis.
Fig. 1.
The brain and spinal cord are composed of highly organized white matter pathways, with varying neuronal densities, diameters, and orientations, as well as gray matter regions with varying cell densities and distributions. Created in BioRender. https://BioRender.com/s48o463