Discrete computation
of the local volume variation (Prima et al.)
For more details on this operator look at: "S. Prima, J.-P. Thirion, G.
Subsol, and N. Roberts. Automatic Analysis of Normal Brain Dissymmetry
of Males and Females in MR Images. In W.M. Wells, A. Colchester, and S.
Delp, editors, the First International Conference on Medical Image Computing
and Computer-Assisted Intervention, MICCAI'98, volume 1496 of Lecture Notes
in Computer Science, pages 770-779, Boston, USA, October 1998."
