15 Mcps photon-counting X-ray computed tomography system using a ZnO-MPPC detector and its application to gadolinium imaging

15 Mcps photon-counting X-ray computed tomography (CT) system is a first-generation type and consists of an X-ray generator, a turntable, a translation stage, a two-stage controller, a detector consisting of a 2 mm-thick zinc-oxide (ZnO) single-crystal scintillator and an MPPC (multipixel photon counter) module, a counter card (CC), and a personal computer (PC). High-speed photon counting was carried out using the detector in the X-ray CT system. The maximum count rate was 15 Mcps (mega counts per second) at a tube voltage of 100 kV and a tube current of 1.95 mA. Tomography is accomplished by repeated translations and rotations of an object, and projection curves of the object are obtained by the translation. The pulses of the event signal from the module are counted by the CC in conjunction with the PC. The minimum exposure time for obtaining a tomogram was 15 min, and photon-counting CT was accomplished using gadolinium-based contrast media. - Highlights: ► We developed a first-generation 15 Mcps photon-counting X-ray computed tomography (CT) system. ► High-speed photon counting was carried out using a zinc-oxide (ZnO) single-crystal scintillator and an MPPC (multipixel photon counter) module in the X-ray CT system. ► Tomography is accomplished by repeated translations and rotations of an object. ► The minimum exposure time for obtaining a tomogram was 15 min. ► The photon-counting CT was accomplished using gadolinium-based contrast media.