OPT: fixed usage (size in voxel instead of mm) and fixed estimation of radius (forgot to add +1 on positive side of matrix)
OPT: fixed usage (size in voxel instead of mm) and fixed estimation of radius (forgot to add +1 on positive side of matrix)

Former-commit-id: bd14d4b92b51246ee23dfd686be6ac9deb809dab [formerly a727e2054c7b16f89aa3bb848cf388f9527b059c]
Former-commit-id: 121badb8f5054fb06e0f39473bf764422c1eabb9
Former-commit-id: 462c6b3a8a8b88539bc9df1148157b5792ca3aef
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox