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
| FA |
|
|---|---|
| Default (9 voxel neighborhood) |
|
| Sphere radius 2 (5 voxel/7.5mm diameter) |
|
| Sphere radius 3 (7 voxel/10.5mm diameter) |
|
| Sphere radius 4 (9 voxel/13.5mm diameter) |
|
| Sphere radius 5 (11 voxel/16.5mm diameter) |
|
