Investigation of low-dose energy-dispersive x -ray computed tomography utilizing beam hardening

To realize novel energy-dispersive X-ray computed tomography (CT) and to reduce the incident dose for the object, we have developed a low-dose low-scattering CT scanner with high spatial resolutions using a room-temperature cadmium telluride (CdTe) detector. X-ray photons are absorbed by the CdTe crystal, and the electric charges flowing through the CdTe crystal are amplified using a current-to-voltage and voltage-to-voltage amplifiers. The first-generation CT is accomplished by repeated translations by the detector and rotations of the object, and the effective photon energy increases with increasing amplification factor of the digital amplifier at a constant maximum output voltage of 5.0 V. The tripleenergy computed tomography (TE-CT) is performed utilizing the beam hardening by the object. In the TE-CT, the scattering photon count is reduced using a 0.5-mm-diam pinhole behind the object, and the spatial resolution is improved by a 0.25-mm-diam pinhole. The exposure time for TE-CT was 9.8 min at a total rotation angle of 180°.