Dual-energy X-ray computed tomography system using a cadmium telluride detector and its application to gadolinium imaging

摘要

To obtain two tomograms with two different photon energy ranges simultaneously, we have performed dual-energy X-ray photon counting using a cadmium telluride (CdTe) detector, two comparators, two frequency-voltage converters (FVCs), and an analog digital converter (ADC). X-ray photons are detected using the CdTe detector with an energy resolution of 1% at 122 keV, and the event pulses from a shaping amplifier are sent to two comparators simultaneously to regulate two thresholds of photon energy. The logical pulses from a comparator are sent to an FVC consisting of two integrators, a microcomputer, and a voltage-voltage amplifier. The smoothed outputs from the two FVCs are input to the ADC to carry out dual-energy imaging. To observe contrast variations with changes in threshold energy, we performed energy-dispersive computed tomography utilizing the dual-energy photon counting at a tube voltage of 100 kV and a current of 8.7 μA. Two tomograms were obtained simultaneously at two energy ranges of 34.0-50.2 keV and 50.2-100 keV. The photon-count subtraction was carried out using a computer program. The maximum count rate was 5.4 kilocounts per second with energies of 10.0-100 keV, and the exposure time for tomography was 10 min.