Patent ID: 6356617
Filing Date: 2002-03-12
Classification: A61B

Abstract:
Device for digital subtraction angiography in the energy subtraction mode,with a monochromator (1) for generating two monochromatic X-ray beams (E1, E2); with a safety system (8) with very rapid beam shutters; with a line scan device driven by a hydraulics system on which is mounted a stool (9) which can be moved up and down for positioning a patient; with a two-line detector (3); with a computer system (6) for control of the system, data acquisition and image processing; characterized in that the detector (3) is formed by two locally resolving ionization chambers (31, 32) which are filled with an ionization gas and have a certain number of anode strips (311, 312); in that a common drift cathode (313) is used for both ionization chambers (31, 32); in that to each ionization chamber (31, 32) is connected a separate detection circuit (51, 52) each with an electronic circuit (50) for each anode strip (311, 312), which operate linearly as a signal converter between 0 volt and 175 volt; in that each electronic circuit (50) has at its input an operational amplifier (OPA), to the negative input of which the input signal from the anode strips (311, 312) is applied, while the positive input is earthed; in that the output of the operational amplifier (OPA) is connected via a first resistance (R1) to the emitter of a transistor (T) at the base of which lies a constant voltage source (S) and the collector of which is connected via a point (P) and a fourth resistance (R4) to the input of an analogue/digital converter (ADC); in that the fourth resistance (R4) is greater than 20 M&OHgr;; in that a direct voltage is applied to the point (P) via a third resistance (R3); in that a second resistance (R2) which passes the input signal current (is) finally to the analogue/digital converter (ADC) lies between the input of the operational amplifier (OPA) and the point (P); and in that the outputs of all the electronic circuits (50) are transmitted as bit words via a bus system (511, 512) to the computer system (6).