A Count-Rate Recovery Method for Photon Counting X-ray Detectors Using Scintillator/SiPM

Previously, we developed a photon counting detector for X-ray fluoroscopic imaging using a scintillation detector unit and an MVT digitizer. Due to the dead time in the detection channels, the counts will be lost when working in a high count-rate condition. To avoid the streak artifacts in the image, we normally adopt a low X-ray dose when imaging with the detector. However, a low X-ray dose always means a worse imaging signal-to-noise ratio (SNR) or longer imaging time. In this work, we model the response of the detector as a paralyzable processing and set up an X-ray imaging system with the detectors for validation. By analyzing the measured count rate of the detector when setting the X-ray tube’s voltage at 120 kV and varying the current from 0.1 mA to 1.2 mA, we estimated the dead time of each channel in the detector to be (112±11) ns. Having the dead time and the paralyzable response model, the lost counts therefore could be recovered according to the measured value. Typically, we measure the count rate of channel 81 to be 2.97 Mcps/pixel and recover it to be 6.20 Mcps/pixel when setting the X-ray tube’s voltage and current at 120 kV and 0.8 mA respectively. An image of the step phantom is further obtained and the streak artifacts in the image are gone after the count-rate recovery and uniformity calibration.