1. An angiography system for an angiographic examination on an examination object of a patient, comprising: an x-ray emitter attached to an end of a C-arm; an x-ray detector attached to another end of the C-arm; a patient support couch for supporting the patient; a system control unit; and a monitor, wherein the system control unit is configured to: obtain a reference image that is adjusted to a current geometric setting of the C-arm, register the reference image the current geometric setting of the C-arm, segment the examination object in the reference image if necessary, generate a mask image from the reference image with image regions lying within the segmentation being artificially contrasted without administrating contrast agent, subtract the mask image from fluoroscopy live images acquired by the angiography system, and generate a roadmap image from the subtraction, and wherein the roadmap image is displayed on the monitor.