ABSTRACT
This chapter focuses on the design choices, performance, and limitations of hybrid pixel detectors as photon-counting detectors (PCD) for X-ray imaging. It reviews properties and limitations of semiconductor sensors for PCDs. The chapter presents the rationale behind electronics design for PCDs and a review of designs. It discusses an outlook for future developments and challenges related to PCDs. Spectroscopic capabilities in PCDs can allow for new quantitative X-ray imaging modalities, such as K-edge X-ray imaging, where the dependence of X-ray attenuation on energy can lead to material identification. One significant effect limiting the performance of high-Z semiconductors in PCDs is charge trapping. Charge trapping also entails that X-rays interacting at different depths in the sensor produce a different amount of induced charge, due to the different fraction of charge trapped along the path to the electrodes. Several technological limitations represent a bottleneck in the development of large area and high count rate high-Z PCDs.
