InSPIRE utility to automatically deform a 3D monomodal image

This program automatically registers mono-modal 3D images. Please down other relevant files to run.

The algorithm of Demons involves:
1. find the difference at each voxel
position using the fixed image as the reference, the delta=movingimage -
fixedimage (3D, minus in matlab does it element by element.
2. Once it is established the location where the local deformation occur (i.e. there is
%more intensity than expected by using the fixedimage reference), calculate
%the downhill grad in x-, y- and z-directions, get the resultant downhill
gradient (this the the steepest slope to decent the hill).
3. this direction is that of a 'stream' flowing prependicularly to the contours of the
'encergy' (L2 normal in this case) hill, use a step factor to multiply
%this to get the actual actionable stepX (in x-, y- and z-directions) size.
4. then simply compute the new voxel position by taking a step for each
%voxel.
5. simply assign the intensity of the movingimage at (newX, newY,
%newZ) as that at this same coordinate on the fixedimage.
6. repeat until reach the max number of allowed iterations or a stopping criterion.
%Intuitive interpretation of Demons: In the above algorithm, Demons could be seen as a
force pushing the contour of iso-intensity out (like the riddles created
by throwing a stone into the pond). Eventually, the energy (i.e. the square
of the difference) is dissipated by repeatedly calculating the delta energy and smoothing
the delta.