Dual-Energy Low-Scattering X-Ray Computed Tomography Using a Lutetium-Oxyorthosilicate Crystal and a Small Photomultiplier Tube

To perform low-dose low-scattering X-ray computed tomography (CT), we have constructed a dual-energy (DE) X-ray photon counter with a high-count-rate detector system and energy-range and -region selectors. The detector system consists of a lutetium-oxyorthosilicate (LSO) crystal, a small photomultiplier tube (sPMT), and a simple inverse amplifier for LSO-sPMT with a pulse-width extender. In DE-CT, both the X-ray source and the detector module are fixed, and the object on the turntable oscillates on the translation stage. Line beams for DE-CT are formed using a lead pinhole and a front tantalum (Ta) x-y slit placed just in front of the object. The scattering-photon count from the object is reduced using a back Ta slit. X-ray photons are detected using the detector system, and the event pulses are input to the two energy selectors. In DE-CT, the tube voltage and current were 60 kV and 1.0 mA, respectively. The energy range and region for soft and iodine-K-edge CT are 12-31 and beyond 35 (35-60) keV, respectively. The maximum count rate of DE-CT was 75 kilocounts per second, and the exposure time for tomography was 19.6 min at a total rotation angle of 360. Outlines of the objects were clearly visible by reducing scattering-photon counts.