photoncountingCT

Photon-counting CT (PCCT) is an imaging modality that employs photon-counting detectors (PCDs) instead of conventional energy-integrating detectors. PCDs convert X-ray photons directly into electrical signals and count individual photons, typically using multiple energy thresholds to separate photons by energy. This enables spectral-like data acquisition without external dispersive materials and can reduce electronic noise, potentially improving image quality at low doses.

Compared with traditional CT detectors, PCCT offers higher intrinsic spatial resolution and improved dose efficiency, particularly at lower radiation levels. The energy discrimination enables material decomposition and multi-energy imaging, producing iodine maps, virtual non-contrast images, and, in some implementations, K-edge imaging. These capabilities allow quantitative tissue characterization and enhanced contrast separation.

Clinical applications span CT angiography, chest and lung imaging, abdominal and musculoskeletal studies, and perfusion-related assessments. The ability to distinguish materials and to visualize small vessels can improve lesion detection and characterization while potentially enabling reduced contrast medium doses in select protocols.

Deployment of PCCT is growing but still limited by cost, the need for new reconstruction algorithms, and larger data sizes that affect processing and storage. Operators require training to optimize energy thresholds and mitigate detector-related artifacts. Despite these challenges, several manufacturers have introduced commercial PCCT systems and clinical experience is expanding.

Ongoing research aims to further improve spatial resolution, spectral performance, dose efficiency, and artifact reduction. As experience accumulates and software ecosystems mature, photon-counting CT is expected to broaden clinical indications and potentially change imaging workflows through more quantitative, energy-resolved CT data.