1. A computer-implemented method for image processing, the method comprising: receiving a first medical image from a data storage device, said first medical image comprising a plurality of image voxels and representing a plurality of tissue regions of a subject; automatically determining a reference value based on said first medical image, said reference value capable of providing a range of background level of voxel intensity values within at least one non-disease tissue region of said subject; generating a disease threshold based on the reference value; identifying portions of the medical image corresponding to disease-tissue regions according to said disease threshold, each of said portions comprising a plurality of connected image voxels in said medical image; and entering data encoding said disease-tissue regions into a database for subsequent comparisons, wherein said identifying portions of the medical image comprises: generating a map comprising spatial locations of candidate disease tissue regions in the medical image; and iteratively identifying disease objects in the medical image based on said map, and wherein said iteratively identifying comprises: providing a ranking of said candidate disease tissue regions according to voxel intensity values of target voxels corresponding to said candidate disease tissue regions; and if the voxel intensity value of the highest ranking target voxel is greater than said disease threshold, growing a disease object around the target voxel's spatial location in the first medical image according to a user-selectable criterion; identifying a portion of the first medical image at the spatial locations of said disease object, said portion comprising a plurality of connected image voxels; subsequently remove spatial locations of said disease object from said map.