anisotropy
Directional dependence of tissue properties, particularly in white matter tracts where water diffusion is restricted along fiber bundles.
Full Definition
In neuroimaging, anisotropy refers to the directional dependence of physical properties within brain tissue. This is most commonly measured in diffusion tensor imaging (DTI) where water molecules diffuse preferentially along white matter fiber tracts rather than perpendicular to them. Fractional anisotropy (FA) is a key metric derived from DTI data that quantifies the degree of directional restriction in diffusion. High anisotropy values typically indicate well-organized white matter tracts, while low values may suggest tissue damage or less organized regions like gray matter.
Usage
Usage note: Often abbreviated as FA when referring to fractional anisotropy measurements.
In Context
- "The anisotropy maps revealed decreased white matter integrity in the corpus callosum." — DTI research paper
- "Fractional anisotropy values were significantly reduced in patients with multiple sclerosis." — Clinical neuroimaging report