Evaluation of a novel photon-counting CT system using a 16-channel MPPC array for multicolor 3-D imaging

X-ray computed tomography (CT) has been widely used in the diagnostic imaging of the interior of the human body. However, the radiation dose of conventional CT typically amounts to 10 mSv. Under such environments, X-ray photons are severely piled-up; therefore, conventional CT acquires energy integrated images, and artifacts are formed by beam hardening. In contrast, a photon counting CT (PC-CT) system is anticipated to construct a low-dose and multi-color CT system. Recently, we proposed a novel PC-CT system using a multipixel photon counter (MPPC) coupled with a high-speed scintillator, which is cost effective and easy to assemble compared to other methods using CdZnTe device. In this paper, we report the results using an advanced CT system consisting of a 16-channel MPPC and scintillator array coupled with a newly developed large-scale integrated circuit (LSI) having an ultrafast signal processing capability. We present the performance of the photon-counting CT capability, such as the contrast of the obtained CT images compared with that of the current-mode CT, and we found that substantial reduction in radiation dose by an order of magnitude. In addition, we report the results of three-dimensional multicolor imaging to identify phantom materials.