Development of a large-area multilayer detector for single-shot dual-energy imaging

Abstract

We have developed a sandwich-like multilayer detector capable of imaging a large field of view for the purpose of dental computed tomography. Two detectors forming the sandwich detector are based on indirect-conversion flat-panel detector technology. This development employed a relatively thin Gd2O2S:Tb scintillator for the front-detector scintillator and a relatively thick CsI:Tl for the rear one. On the other hand, the same photodiode arrays based on complementary metal-oxide-semiconductor active pixel technology were used for both detector layers. While the substrate of the rear flat-panel detector was a conventional printed-circuit board (PCB), the front detector was realized onto a flexible PCB, which is then electrically connected to a separate corresponding PCB placed under the rear detector PCB. Imaging performance of each detector layer in the sandwich detector was evaluated in terms of large-area or zero-frequency signal and noise, modulation-transfer function, noise-power spectrum, and detective quantum efficiency. Compared to previous designs, the current design showed higher signal-to-noise ratio performances for which the scintillators used were mainly responsible. Demonstration dual-energy images obtained for a postmortem mouse supported the quantitative measurements.