Experimental investigation of a simple estimate of axon size

Motivation: Changes in radial diffusivity with diffusion time have been suggested to correlate with axon diameter but has not yet been experimentally evaluated with MRI and histology. Goal(s): This work aims to experimentally compare diffusion-time difference in radial diffusivity with histology measures of axon diameter. Approach: Diffusion time dependent radial diffusivity and axon diameter were measured in ex vivo spinal cords via MRI and scanning electron microscopy acquisitions, respectively. Results: Diffusion-time difference in radial diffusivity showed a strong linear correlation (r = 0.923) with histology derived estimates of mean axon diameter in ex vivo ferret spinal cord. Impact: Diffusion time difference in radial diffusivity is shown in this work to correlate well with histology derived axon diameter. Importantly, it is straightforward to measure and therefore provides a simple estimate of axon diameter.