In an X-ray imaging apparatus, a detection panel has monitor pixels for monitoring X-rays. A signal processor samples a dose signal of a dose per unit time of X-rays according to an output of the monitor pixels. A start detector checks whether irradiation of X-rays is started according to a result of comparison between the dose signal and a start threshold. An AEC device acquires cumulative dose from a start time of the start of irradiation of X-rays until acquisition time after a predetermined time according to the dose signal. According to the cumulative dose, a predicted time point of a reach of the cumulative dose to a target dose is estimated. A stop signal is transmitted to a radiation source controller at the predicted time point, to stop the irradiation of X-rays.

Three semiconductor detectors are installed at positions where incidence of radiation on a scintillation detector is not blocked, at equal intervals centered on a central axis of the scintillation detector and at equal angles with respect to a plane which is at a right angle to the central axis. An energy compensation factor is determined on the basis of an average pulse height value obtained from a second pulse height spectrum obtained by analog voltage pulses which are output from these semiconductor detectors, and energy characteristics of a high-range dose rate obtained by a direct-current voltage which is output from the scintillation detector are compensated for.

Three semiconductor detectors are installed at positions where incidence of radiation on a scintillation detector is not blocked, at equal intervals centered on a central axis of the scintillation detector and at equal angles with respect to a plane which is at a right angle to the central axis. An energy compensation factor is determined on the basis of an average pulse height value obtained from a second pulse height spectrum obtained by analog voltage pulses which are output from these semiconductor detectors, and energy characteristics of a high-range dose rate obtained by a direct-current voltage which is output from the scintillation detector are compensated for.

An apparatus and method are provided to correct for time-walk errors during photon detections (e.g., detecting gamma rays). A time-walk correction is determined using measurements of energy (or charge) that apply different time windows, enabling corrections accounting for variations in the ratio between fast and slow components in the detected pulse. For example, one time window can be used to integrate the leading end of the pulse, thereby predominantly measuring the fast component, while a second window is used to integrate a trailing end of the pulse to predominantly measure the slow component. Alternatively or additionally, low-pass and high-pass filters may select the slow and fast components, respectively. The time-walk correction is a function of multiple measurements representing different components (e.g., fast and slow) of the pulse shape.