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New PRIMICON pick-up tube for multimode x-ray TV cameras

A typical radiological TV imaging system includes an X-ray generator, an X-ray image intensifier tube which produces a visible image, an optical lens, a pick-up tube working in a TV camera, and finally an image processing device followed by an image display. The PRIMICON pick-up tubes are already well tried in various radiological systems (general fluoroscopy, digital fluoroscopy, digital subtraction angiography (DSA)) In which they provide their image performance features: high resolution, and excellent contrast and large dynamic range. Another important image feature is the time response of the pick-up tube, named lag. In general fluoroscopic mode, high lag is needed to integrate the noise caused by the low X-ray dose. On the contrary, in digital fluoroscopic mode or DSA mode, low lag is required to pick-up images with moving contents. Consequently, as standard pick-up tubes have a fixed amount of lag, two TV cameras must be used if the system has to operate in the three modes described above. Due to a special design of its photoconductive layer, the new PRIMICON tube features variable lag, the amount of lag being controlled by the combination of the signal current level and of the light bias rating. The necessary light source is located close to the optical path in front of the tube's faceplate. So this new tube (referenced Th 9957) is suited either to general fluoroscopic mode (12 % lag is got with 100 nA signal current and no light bias) or the digital fluoroscopic or DSA modes (2% lag is got with 1500 nA signal current and 100 nA light bias). As a conclusion, the new PRIMICON pick-up tube enables multirnode TV cameras to be realized, which bring substantial benefits in radiological systems - system design is simpler, - system use is easier, - system maintenance is alleviated and fewer spare components are needed.