X-Ray diagnostic installation for radiography and fluoroscopy

An X-ray diagnostic installation for radiography and fluoroscopy comprising:

• an X-ray tube, a television installation for the transmission of the X-ray image, focus size control means for controlling the size of the focus of the X-ray tube, and dose rate means for generating at least one output value during fluoroscopy, said focus size control means comprising at least one control electrode (5, 6) for determining the focus size via the electrode potential, a control voltage generator (15) connected with the control electrode for controlling the electrode potential, and a control circuit (13) connected with said control voltage generator (15), said control circuit having storage means (22, 23) for storing said fluoroscopy output value, the maximum load for said X-ray tube, and selected radiography values, said control circuit further having an arithmatic unit connected to said storage means for computing an electrode potential based on the contents of said storage means for operating said control voltage generator for establishing a focus size during radiography which is substantially the smallest the value in combined dependence upon said output value, said maximum load of the X-ray tube (1), and said selected radiography values, and an operating console (17) connected to said control circuit (13) having an adjustment means (18) for manual selection of said radiography values.