Entropy

Entropy is a mathematical measure of dissimilarity which can be applied to a neighborhood of voxels. MATLAB has the function entropyfilt. The following is how to perform the analysis:

% Read the volume

V = spm_vol( filename );

Y = spm_read_vols( V );

radius = 2;   % radius of sphere in voxels over which to estimate entropy

S = strel( 'sphere', radius) ;

% Do the entropy calculaton

Ye = entropyfilt( Y, S.Neighborhood );

% Save as new volume

Example with FA at 1.5 mm3