Photon-counting CT (PCCT) uses semiconductor detectors to directly convert X-ray photons to electrical signals, the intensity of which is directly proportional to the energy of the individual photons. PCCT offers several advantages in cardiovascular imaging, including ultra-high-resolution (UHR) imaging, improved multi-energy capabilities, reduced noise and artifacts, and improved iodine signal and radiation dose efficiencies. UHR imaging enhances the assessment of small vessels, dense calcifications, and stents. Multienergy mode enhances the iodine signal, reduces artifacts, and allows for material separation and lesion characterization. In this article, we review PCCT technology, highlight the benefits of PCCT in cardiovascular imaging using case examples, and discuss its challenges.

Photon-counting detector (PCD) CT is a new CT technology utilizing a direct conversion X-ray detector, where incident X-ray photon energies are directly recorded as electronical signals. The design of the photon-counting detector itself facilitates improvements in spatial resolution (via smaller detector pixel design) and iodine signal (via count weighting) while still permitting multi-energy imaging. PCD-CT can eliminate electronic noise and reduce artifacts due to the use of energy thresholds. Improved dose efficiency is important for low dose CT and pediatric imaging. The ultra-high spatial resolution of PCD-CT design permits lower dose scanning for all body regions and is particularly helpful in identifying important imaging findings in thoracic and musculoskeletal CT. Improved iodine signal may be helpful for low contrast tasks in abdominal imaging. Virtual monoenergetic images and material classification will assist with numerous diagnostic tasks in abdominal, musculoskeletal, and cardiovascular imaging. Dual-source PCD-CT permits multi-energy CT images of the heart and coronary arteries at high temporal resolution. In this special review article, we review the clinical benefits of this technology across a wide variety of radiological subspecialties.