1. A method for tracking image sections which represent indicator body parts of a body in a process sequence of images, wherein changes in the position of the indicator body parts are used as an indicator for changes in the position of a treatment body part of the body which is to be treated using a treatment beam, said method comprising the following steps: providing advance image data which describe an advance sequence of images representing a result of an advance analysis of the body; providing process image data which describe the process sequence of images, wherein the process sequence of images represents a result of a process analysis of the body which is performed after the advance analysis; determining, on the basis of the advance image data, sub-images which undergo similar changes in position in the advance sequence; extracting, on the basis of the process image data and the determined sub-images, image sections from the images of the process sequence which have an image content which corresponds to the image content of the determined sub-images; and tracking the extracted image sections in the process sequence.