A mammography installation or a mammography system allows x-ray projections of the breasts for at least one 3D volume image to be calculated with and without a contrast agent progression, and without repositioning of the patient within an examination cycle. A single target having a specified pattern of bright and dark areas in placed in front of the monitor in the detection areas of the radar and the camera. The opposed cutting teeth of the cutting bars may be arranged symmetrically, asymmetrically or anti-symmetrically.