Photon-Counting CT: Technology, Current and Potential Future Clinical Applications, and Overview of Approved Systems and Those in Various Stages of Research and Development

Abstract

Photon-counting CT (PCCT) has emerged as a transformative technology, with the potential to herald a new era of clinical capabilities. This review provides an overview of the current status and potential future developments of PCCT, including basic physics principles and technical implementation by different vendors, with special attention to applications that have not, to date, been emphasized in the literature. The technologic underpinnings that distinguish PCCT scanners from traditional energy-integrating detector (EID) CT scanners with dual-energy capability are discussed. The inherent challenges of PCCT and the innovative breakthroughs that have enabled key PCCT features, such as enhanced image resolution, material discrimination, and radiation dose efficiency, are reviewed. Two categories of clinical applications are considered: (a) applications that are possible with current-generation EID CT but may be improved with the higher spatial, temporal, and contrast resolution of PCCT (eg, CT angiographic vasculitis imaging with high spatial, contrast, and temporal resolution and ultra-high-spatial-resolution "opportunistic" osseous imaging) and (b) potential future applications that are not currently feasible with EID CT but that may become possible and practical with PCCT (eg, reduced need for serial follow-up imaging with advanced CT or MRI because of more complete, definitive imaging evaluation with PCCT at first presentation).