X-ray sensor signal processor and X-ray computed tomography system using the same

Claim 1

An X-ray CT apparatus comprising: an accelerator for emitting X-rays in a form of pulses of repetitive periods; a scanner for rotating or moving up and down an object to be inspected to which X-rays emitted from said accelerator are radiated; a plurality of X-ray sensors for detecting X-rays obtained after passing through said object to be inspected; an X-ray sensor signal processing circuit for processing output signals from said plurality of X-ray sensors; a CT controller for reconstructing a sectional transparent image of said object to be inspected on the basis of said output signals of said X-ray sensors; a first capacitor for removing a DC current component of a dark current from each of the output signals of said X-ray sensors, said first capacitor being located at a first stage circuit of said X-ray sensor signal processing circuit; and an integration circuit comprising an operational amplifier, a resistor connected to said operational amplifier in parallel, and a second capacitor, said integration circuit being located at said first stage circuit of said X-ray sensor signal processing circuit; wherein in said integration circuit, a current signal obtained after removal of said DC current component by said first capacitor flows into said second capacitor, so that electric charges are stored in said second capacitor and integrated, and as an output signal of said integration circuit, a voltage signal proportional to a number of average photons of said X-rays is obtained after integration of output to an AD converter; wherein said integration circuit outputs said output signal according to a time constant determined by said resistor and said second capacitor; and wherein said output signal of said integration circuit is held by said time constant until said output signal of said integration circuit is converted by said AD converter, and a value for said time constant is set which allows said output signal of said integration circuit to become zero between an emission of X-rays from said accelerator and a next emission of the X-rays from said accelerator.