The x-ray appts. has an x-ray generator (1), an x-ray tube (2) and an image amplifier television monitor chain (4...7) comprising an x-ray image amplifier (4), a television camera (5) and a monitor (7). The output signals from the television camera (5) are fed to a regulating circuit (6) for the x-ray generator (1) and a stop plate (8) lying in the path of the x-ray beam. Pref. the regulating circuit (6) has a data reduction stage for combining a number of image points of the x-ray image and a threshold stage for contour identification by comparing the measured values of each image zone with a given threshold value.
