An operating method is disclosed for an X-ray machine for examining a patient by using a contrast agent in the case of which a preliminary examination is carried out for determining a contrast agent curve in the case of which a series of attenuation values relating to defined scanning instants are acquired at a set scanning position, the contrast agent curve being determined on the basis of the attenuation values, and being stored for a follow-up examination. The contrast agent curve can be loaded during a follow-up examination and need not be determined anew, and so a reduction is attained in the contrast agent used, the applied radiation dose and the examination time. The contrast agent curve can, furthermore, be adapted to the examination situation currently present by taking account of biosignals.
