Photon-counting CT in cardiac imaging: multi-institutional guidance on technical principles, clinical evidence, and practical protocols.

Coronary CT angiography (CCTA) is recommended as a first-line test for evaluating suspected coronary artery disease in many patient cohorts. Photon-counting detector CT (PCD-CT) introduces direct energy discrimination, higher geometric dose efficiency, and ultrahigh spatial resolution compared to energy-integrating detector CT, enabling improved coronary lumen visualization and intrinsic spectral imaging. This multi-institutional guidance summarizes technical principles of PCD-CT relevant to cardiac imaging and synthesizes contemporary evidence across key applications: (1) CCTA protocol selection and reconstruction (including ultrahigh-resolution modes); (2) stent and heavily calcified plaque assessment; (3) coronary physiology using CT-derived fractional flow reserve; (4) structural heart evaluation including pre-TAVR planning; and (5) myocardial tissue characterization with late enhancement and extracellular volume mapping. We provide pragmatic protocol pathways and contrast-dose strategies, with compact tables that standardize scan modes, reconstruction kernels, iterative reconstruction levels, and spectral outputs.