Patent ID: 7359542

Claim:
A method of detecting suspected anomalous shadows, comprising: obtaining a difference image representing a difference between two images, which have been obtained of a same subject at different photographing times, by subjecting said two images to an interimage process to obtain the difference between said two images, obtaining a processed difference image by subjecting the obtained difference image to an image process wherein an actual difference between the two images on which said difference image is based is enhanced relative to artifacts appearing due to misalignment of a position of a structural element of the subject on one of the two images from a corresponding position of the structural element on the other of the two images, and detecting the actual difference between the two images from the processed difference image as suspected anomalous shadows, wherein the image process is an image process that suppresses the artifacts more than the actual difference between the two images on which the difference image is based, and wherein the image process for suppressing the artifacts relative to the actual difference between the two images is a process based on a morphology process employing structuring elements that are larger than the artifacts while smaller than the actual difference; wherein the image process further comprises separating the difference image into a high-density image formed from portions of the difference image having a density equal to or higher than a predetermined density and a low-density image formed from portions having a density less than the predetermined density, applying said morphology process to both the high-density and low-density images, and combining the high-density and low-density images after the morphology process is applied.