1. A method for modifying a first data set, which is called the target data set and represents the contour of an anatomical object, the method comprising the steps of: matching a second data set, which is called the template data set and comprises a template for the modification and a template of the object, to the target data set such that the object template in the template data set matches the object in the target data set, thereby also adapting the modification template; applying the adapted modification template to the target data set; characterized by: the step of correcting a border between the object and the adapted modification template in order to close a gap between the object and the adapted modification template.