6 Mcps photon-counting X-ray computed tomography system using a 25 mm/s-scan linear LSO–MPPC detector and its application to gadolinium imaging

6 Mcps photon counting was carried out using a detector consisting of a 1.0 mm-thick LSO [Lu 2(SiO 4)O] single-crystal scintillator and an MPPC (multipixel photon counter) module in an X-ray computed tomography (CT) system. The maximum count rate was 6 Mcps (mega counts per second) at a tube voltage of 100 kV and a tube current of 0.91 mA. Next, a photon-counting X-ray CT system consists of an X-ray generator, a turntable, a scan stage, a two-stage controller, the LSO–MPPC detector, a counter card (CC), and a personal computer (PC). Tomography is accomplished by repeated linear scans and rotations of an object, and projection curves of the object are obtained by the linear scan with a scan velocity of 25 mm/s. The pulses of the event signal from the module are counted by the CC in conjunction with the PC. The exposure time for obtaining a tomogram was 600 s at a scan step of 0.5 mm and a rotation step of 1.0°, and photon-counting CT was accomplished using gadolinium-based contrast media. ► 6 Mcps photon counting X-ray CT performed by repeated linear scans and rotations of an object. ► Detector consists of an LSO scintillator and an MPPC (multipixel photon counter) module. ► Projection curves of the object obtained by the linear scan with a velocity of 25 mm/s. ► Exposure time was 600 s. CT was carried out using gadolinium-based contrast media.