Spectral Photon-Counting CT System Based on Si-PM Coupled with Novel Ceramic Scintillators

Abstract

X-ray computed tomography (CT) exhibits superior ability in visualizing the interior of the human body three-dimensionally for medical diagnosis. However, conventional CT requires a high-exposure dose per single scan and yields monochromatic CT images owing to loss of energy information. Hence, spectral photon counting CT (SPCCT) has been proposed as the next-generation X-ray CT. Whereas semiconductor-based SPCCT achieves superior results in in vivo imaging, the cost of the system is extremely high, and the readout circuit becomes overly complicated owing to the numerous channels involved. Therefore, to actualize a low-cost and simple system configuration, we propose a new SPCCT system that uses silicon photomultipliers/multipixel photon counters (MPPCs). To evaluate the potential of the MPPC-based system as SPCCT, we compare CT images acquired under the same conditions between a photodiode (PD), which is typically used in conventional CT, and an MPPC. Results indicate that the contrast-to-noise ratio of the obtained CT image using the MPPC improved by 12.6-fold compared with that using the PD, implying that the MPPC-based SPCCT system enables low-dose CT. Moreover, the 64-channel MPPC-based SPCCT system successfully reconstructs the color image and density maps of iodine, gadolinium, and gold using K-edge features. These results suggest the high potential of MPPC-based SPCCT for visualizing drug delivery systems.