Development of a high SNR data acquisition system for 16 channel x-ray detector module

Summary form only given. The major advantage of slip-ring technology in spiral CT is that it facilitates continuous rotation of the x-ray tube, so that volume data can be acquired from a patient quickly. Not only for such a fast scan, but also for dose reduction purposes, a high signal-to-noise ratio and fast data acquisition system are required. In this study, we have built a multi-channel photodetector and multi-channel data acquisition system for CT application. The detector module consisted of CdWO₄ crystal and Si photodiode in 16 channels. For the performance test of the preamplifier stage, both the transimpedance and switched integrator types are optimized for the photodetector modules. The switched integrator showed better noise performance in the limited bandwidth which is suitable for the current CT application. The control sequence for data acquisition and 20 bit ADC is designed with VHDL (very high speed integrated circuit hardware description language) and implemented on FPGA (field programmable gate array) chip. Our Si photodiode detector module coupled to CdWO₄ crystal showed a comparable signal with other commercially available photodiodes for CT. The switched integrator type showed higher SNR but narrower bandwidth compared to a transimpedance preamplifier. Digital hardware is designed by FPGA, so that the control signal could be redesigned without hardware alteration.