1. A method for acquiring and processing a medical image for a human body or an animal body, wherein the medical image is obtained from a first point of a target whose medical image is to be generated to a second point opposite the first point and the medical image is a sum of images obtained in regions (wherein a region comprising the first point is a first region, a region comprising the second point is an n-th region, an image corresponding to the first region is defined to be a first sectional image, and an image corresponding to the n-th region is defined to be an n-th sectional image) obtained by dividing a region between the first point and the second point n times (wherein n>2, n is a positive integer greater than 2), Wherein defining that sequentially obtaining the first sectional image to the n-th sectional image from the first region to the n-th region or sequentially obtaining the n-th sectional image to the first sectional image from the n-th region to the first region is sequential sectional-image acquisition, the method comprising: obtaining the first to n-th sectional images of the first to n-th regions through non-sequential sectional-image acquisition starting from one of the first to n-th regions; sequentially arranging the obtained first to n-th sectional images; and registering the medical image with a second medical image of the target whose medical image is to be generated, wherein more time is needed in obtaining the medical image than in obtaining the second medical image; wherein in obtaining the first to n-th sectional images through non- sequential sectional-image acquisition, after p-th to q-th sectional images including a primary interest region or a region having a movement (wherein p is an integer, 1≦p<n, q is an integer, and p≦q<n) are obtained, remaining sectional images are obtained.