1. A method for segmenting a body structure image data set produced from a medical imaging method, comprising: using a reference data set to define delineated body structures in the body structure image data set; and ascertaining an overall mapping function that substantially maps a reference data set onto the body structure image data set, wherein the overall mapping function comprises a portion that includes a dissection of the body structure image data set into structural parts and their individual rearrangement, and a portion which includes a global deformation and/or shift of the body structures.