Room: Room 207
Purpose: Photon counting detectors are promising technology in the next generation x-ray imaging system with higher spatial resolution and energy discriminating capabilities. In this study, we compared detectors of two materials (Cadmium Zinc Telluride (CZT) and Silicon), which are commonly used as photon counting detectors. Also, the image quality was evaluated for microcalcification detection.
Methods: In this study, we simulated the detectors of two materials with the same geometry using the Geant4 Application for Tomographic Emission (GATE). In order to compare the two materials, the image quality and Modulation Transfer Function (MTF) were compared according to the pixel size and detector thickness. The MTF representing the resolution characteristics in an x-ray imaging system was measured in accordance with IEC 62220-1-2 specifications. To evaluate image quality, we designed the breast phantom with microcalcifications embedded in various sizes (0.30mm, 0.27mm, 0.20mm, 0.16mm, and 0.13mm).
Results: According to the results, the MTF of CZT was higher than that of silicon, and the CNR value of CZT was about 1.05 times higher than that of silicon. Compared with CZT, the CNR value was relatively lower because of the more noise in the silicon material. In addition, the detector with smaller pixel pitch and thinner detector thickness showed better MTF results. The high atomic number of the materials gives a high quantum efficiency in comparison with silicon.
Conclusion: The results demonstrated that CZT is a promising semiconductor material in terms of system resolution and image quality. It has also shown that as the pixel size decreases, spatial resolution and contrast are improved. However, due to the problem of charge sharing, it is necessary to design an appropriate pixel size to balance these effects.
Funding Support, Disclosures, and Conflict of Interest: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2017R1A2B2001818).