Photon-counting CT for Chest Imaging—What Have We Learned So Far?

CT imaging has advanced significantly, with dual-energy CT (DECT) marking a milestone by using 2 energy spectra for enhanced tissue characterization. The latest innovation is photon-counting detectors (PCD), which offer superior spatial resolution, contrast-to-noise ratio (CNR), and potential for reduced radiation dose compared with traditional energy-integrating detectors (EID). Photon-counting CT (PCD-CT), which directly counts individual photons using semiconductors, has important implications for chest imaging, especially for complex disease processes that benefit from imaging at higher spatial resolution. PCD-CT achieves improved spatial resolution by eliminating the blurring effects associated with EID scintillators. Enhanced CNR is achieved through energy discrimination and selective use of photon energies, which also helps to minimize electronic noise. PCD-CT facilitates significant radiation dose reduction, particularly valuable for patients who receive regular follow-ups, like in lung cancer screening. In addition, PCD-CT provides spectral capabilities in every scan, unlike DECT, which requires preselecting a specific spectral scan mode. In chest imaging, PCD-CT shows promise in detecting and definitively characterizing infectious diseases, interstitial lung disease, malignancies, and vascular conditions at low radiation doses, offering higher diagnostic accuracy and patient safety. Despite these advancements, challenges remain in optimizing spectral imaging and integrating PCD-CT into routine clinical workflows, necessitating ongoing research and development.