1. A computer system comprising: at least one processor; and memory, wherein said computer system is configured for: receiving a first image of a region of interest, said first image having been taken at a first time, and said region of interest being associated with a particular anatomical structure, where a boundary defines said region of interest in said first image; dividing said region of interest into a plurality of volumetric sub-regions of interest, said plurality of volumetric sub-regions of interest defined by radial spokes emanating from a center of mass of said region of interest and said boundary of said region of interest; receiving a second image of said region of interest, said second image having been taken at a second time; registering said first image with said second image to create a new, third image in which said region of interest in said third image at least approximates a size and shape of said region of interest in said first image, but in which said region of interest in said third image has been repositioned with respect to said region of interest in said first image to reflect a change in orientation of said anatomical structure between said first image and said second image, where registering said first image with said second image comprises: identifying at least a particular one of said plurality of volumetric sub-regions of interest within said region of interest in said first image; identifying said particular one volumetric sub-region of interest within said region of interest in said second image; and mapping said particular one volumetric sub-region of interest in said first image to said particular one volumetric sub-region of interest in said second image; and using said second and third images to assess a change in said region of interest between said first time and said second time.