The invention relates to a method for post-processing a 3D image data set of a vessel structure of a human or animal body, in which a 2D DSA (Digital Subtraction Angiography) of the vessel structure is recorded and registered with the 3D image data set. The 2D DSA is compared with a corresponding projection image computed from the 3D data set and this is changed, e.g. by changing the segmentation parameters, to adapt it to the 2D DSA. This enables the outstanding local resolution of the 2D DSA to be used for improving the 3D image data set.