A method implemented on at least one device each of which has at least one processor and storage, the method comprising: designating a first image of an object as a reference image, the reference image comprising at least a reference feature point and a reference structure; obtaining a second image of the object, the second image comprising a feature point and a structure, the feature point corresponding to the reference feature point of the reference image, the structure corresponding to the reference structure of the reference image, wherein the first image and the second image are lung images taken at different times; performing a first registration with the second image to obtain a first registered image, the first registration comprising an affine transformation performed on the second image, the first registered image comprising the feature point and the structure; performing a second registration with the first registered image to obtain a second registered image, the second registration comprising aligning the structure in the first registered image with the reference structure in the reference image, the second registered image comprising the feature point; performing a third registration with the second registered image to obtain a third registered image, the third registration comprising aligning the feature point in the second registered image with the reference feature point in the reference image, the feature point including a point with the highest gray level or a point designating a positioning of one or more ribs; and subtracting the third registered image from the reference image to obtain a subtraction image comprising the feature point or the structure, wherein the first image and the second image are preprocessed based on an optimal Hough template obtained based on a value of a gravity center of the Hough template so as to locate the one or more ribs within the first image and the second image. designating a first image of an object as a reference image, the reference image comprising at least a reference feature point and a reference structure; obtaining a second image of the object, the second image comprising a feature point and a structure, the feature point corresponding to the reference feature point of the reference image, the structure corresponding to the reference structure of the reference image, wherein the first image and the second image are lung images taken at different times; performing a first registration with the second image to obtain a first registered image, the first registration comprising an affine transformation performed on the second image, the first registered image comprising the feature point and the structure; performing a second registration with the first registered image to obtain a second registered image, the second registration comprising aligning the structure in the first registered image with the reference structure in the reference image, the second registered image comprising the feature point; performing a third registration with the second registered image to obtain a third registered image, the third registration comprising aligning the feature point in the second registered image with the reference feature point in the reference image, the feature point including a point with the highest gray level or a point designating a positioning of one or more ribs; and subtracting the third registered image from the reference image to obtain a subtraction image comprising the feature point or the structure, wherein the first image and the second image are preprocessed based on an optimal Hough template obtained based on a value of a gravity center of the Hough template so as to locate the one or more ribs within the first image and the second image. <EOS>