A new approach to structural integrity assessment based on axial and radial diffusivities

Funct Neurol. 2012 Apr-Jun;27(2):85-90.


This study describes a method for performing diffusivity measures along and across a specific direction, derived from white matter in healthy controls. The diffusion tensor (DT) assigns a principal eigenvector (v₁) and eigenvalue (axial diffusivity, d(ax)) to each voxel. The average of the second and third eigenvalues is the radial diffusivity, d(rad) v₁ may be affected by pathology, therefore when comparing d(ax) and d(rad) in patients one has to consider the direction of the measurement and underlying anatomy. Here we created a representative super-DT dataset, DT(ref), whose eigenvector, v(1,ref), was considered the most likely direction of diffusivity per voxel. We defined the projected axial diffusivity, d(p-ax), as the projection of individual DTs along v(1,ref) and the projected radial diffusivity, d(p-rad), as the average of the projections along the second and third eigenvectors of DT(ref). The projected diffusivities are promising new parameters for studying white matter pathology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anisotropy
  • Brain / physiology*
  • Diffusion Tensor Imaging
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nerve Fibers, Myelinated / physiology*