Age-related alterations in soma and neurite fraction obtained from high-gradient diffusion MRI data across the lifespan

We studied alterations in soma and neurite signal fractions with age based on Soma And Neurite Density imaging (SANDI) in 43 healthy adults across the lifespan using multi-shell dMRI measurements acquired on the MGH Connectome scanner. We observed decreases in soma fraction with age in all cortical lobes, especially in the frontal lobe. The neurite fraction predominantly decreased with age in the genu of corpus callous. These results suggest a regionally selective aging effect on changes in compartmental composition within the brain, potentially reflecting alterations in microstructure associated with neurodegeneration.