Fig. 2.
A toy example simulating tissue deterioration to illustrate the behaviour of the continuum from local to global mass-balancing. (I) Input image example; each of the regions (A,B,C,D) has various random amounts of white pixels removed, representing tissue deterioration. (II) Suppose that there is a disease (a) corresponding to tissue loss in regions A+B+C+D, a disease (b) corresponding to tissue loss in regions C+D, and a disease (c) corresponding to tissue loss in region D. Here we display the correlation of each disease with the mass allocation OTF at each voxel, and we do this for various choices of ca. The results illustrate that global mass-balancing leads to stronger correlations compared to local mass-balancing for tissue loss over a large region. However, if only a local region is affected as in (c) and there is confounding (i.e. uncorrelated) tissue loss in other regions, the correlation strength decreases compared to the more local approaches.