Abstract: A radiation detection circuit integrates output currents of a plurality of X-ray CT scanner radiation detectors, which are combinations of scintillators and photodiodes, during a short period to convert them to charge information in order to collect data for reproducing a tomogram. A current amplifier is connected to the output terminal of the photo-diode, and an output current of the current amplifier is charged in an integration capacitor. In this manner, the radiation detection circuit enables reduction of the measurement period.

Abstract: An integral-type small signal input circuit having a Miller integrator is adapted to perform cyclically an integrating operation, a resetting operation and an input offset current compensating operation. An input offset current compensation circuit which forms a feedback circuit of the amplifier in the Miller integrator is arranged to supply a compensation current to the amplifier for canceling the input offset current during the compensating operation and to supply the held compensation current to the amplifier during the integrating operation. During the compensation period, a low-pass filter which blocks sinusoidal noise components in the input signal is connected to the input of the integrator so that the held compensation current is not affected by the noise components.