Fig. 2.
Neighborhood volumes defined as a series of concentric shells around voxel location xi for voxel i∈𝒯. Schematic view of a 2D grid with individual voxels shown as dark grey dots. Concentric shells are constructed that are centered at xi. The largest radius is defined as R. All radii are defined as rj=jR/M, with M as the maximal number of shells. A neighborhood volume Vj(xi)={k∈𝒯:rj−1<|xk−xi|≤rj} is defined as all voxels that fall into a concentric shell defined by two radii, rj−1 and rj with rj−1<rj. As an example, the neighborhood shell V10(xi) is shown in light grey, defined as the set of voxels located between radii r9 and r10.