Recent
diffusion-weighted imaging techniques have enabled the inference of axon
diameter, a valuable neuroanatomical measure1,2. Current techniques fit a cylindrical model of axons to the acquired
signal, primarily in the transverse direction. Despite many improvements,
sensitivity to small axons is difficult to achieve, primarily due to the scanner’s
physical limitations. Even with a strong gradient strength system such as the connectome scanner and high SNR, the minimum
resolvable axon diameters are greater than 2μm, which accounts for only a small
proportion of axons in the human brain. Here we utilize Neuman’s cylindrical
model3, and generalize it to the geocentric direction in the longitudinal plane
of axons (Figure 1) to decrease the minimum axon diameter resolvable with a
given scanner.
