An operating method for an X-ray machine is disclosed for carrying out a preliminary examination by using a contrast agent, in the case of which a number of heartbeats are determined within a time interval between a first instant of a contrast agent administration and a second instant of a maximum in a concentration of the contrast agent. An operating method for the X-ray machine is also disclosed for carrying out a main examination by using a contrast agent, in the case of which the scanning of the examination region is not started until the number of heartbeats coincides with a preset value such that the scanning is performed at a high concentration of the contrast agent inside the examination region, without the need to adapt the value to the heart rate currently present.