1. A method for registering a two-dimensional image data set, generated using fan-shaped imaging rays, in the medical field, comprising the following steps: processing the two-dimensional image data on the basis of a spatial transformation function which describes a spatial relative position between points which have been imaged using a fan-shaped imaging ray, and the imaging apparatus used for imaging; and processing the two-dimensional image data on the basis of an imaging transformation function which describes an imaging function of the imaging apparatus used for generating the two-dimensional image data set, which describes a spatial relationship between the actual spatial position of imaged points and their imaging location in a recording.