Abstract: An X-ray system includes an X-ray generator for operating an X-ray tube (1) having a cathode which can be heated by a filament current (I.sub.h), a continuation (5, 57) which is operative in an exposure mode so as to boost the filament current to a boost value (I.sub.b), and a continuation which is also operative in the exposure mode so as to decrease the filament current and to switch on the tube voltage (U). The time elapsing until the start of exposure is reduced in that the X-ray generator has a special mode in which the filament current is boosted to the boost value (I.sub.b) while the tube voltage (U) is switched on, circuitry (4, 6) is provided for measuring the tube current flowing in the special mode. A memory (8) is provided for storing the temporal variation of the measured tube current, or a value (I.sub.cor) derived therefrom, and the control unit (5, 57) is operative for deriving the boost time from the temporal variation stored in the memory (8).

Abstract: In X-ray generators comprising a converter for generating the high-voltage for an X-ray tube, substantial dose fluctuations are liable to occur from one exposure to another of series involving a fixed exposure time due to supply voltage fluctuations or fluctuations in the object absorption. These dose fluctuations are more pronounced as the exposure time is shorter and as the converter frequency is lower. These fluctuations are reduced by terminating a series of exposures each time after the same number of converter alternations when the deviation between the actual value and the reference value of the dose or the dose rate is smaller than a predetermined value.

Abstract: The invention relates to a circuit arrangement useful in an X-ray diagnostic apparatus for supervising the loading of an X-ray tube. A first signal which is dependent on the anode temperature controls an indication and/or a blocking device. A second signal is formed which corresponds to the maximum temperature (T.sub.max) minus a value (.DELTA. T) which is dependent on the exposure load to be expected. The two signals are compared with each other and the indication or blocking device is released if the temperature (T.sub.i) represented by the first signal is lower than the temperature (T.sub.max -.DELTA. T) represented by the second signal.