Technical advances and clinical impact of photon-counting computed tomography angiography for peripheral artery disease.

Objective: Accurate cross-sectional imaging is essential for diagnosis, procedural planning, and postintervention surveillance in patients with peripheral artery disease (PAD). Conventional computed tomography angiography (CTA) is limited by calcium blooming, beam hardening, and reduced diagnostic accuracy in small and heavily calcified vessels. Photon-counting computed tomography angiography (PCCTA) represents a recent technological advancement with the potential to overcome these limitations. This review summarizes the technical principles of PCCTA and evaluates current evidence regarding its image quality, diagnostic performance, and clinical implications in PAD. Methods: A narrative review of peer-reviewed literature and scientific presentations was performed using MEDLINE, Scopus, and Google Scholar from database inception through October 22, 2025. Search terms included "photon-counting CT," "photon-counting computed tomography angiography," "peripheral artery disease," "below-the-knee angiography," and "ultra-high-resolution CT." Studies evaluating image quality, diagnostic accuracy, reconstruction techniques, and clinical applications of PCCTA in peripheral artery disease were included. Results: PCCTA utilizes energy-resolving detectors that directly count and bin individual X-ray photons, enabling true spectral imaging, reduced electronic noise, and smaller detector pixel sizes. These features result in improved spatial resolution, higher contrast-to-noise and signal-to-noise ratios, and marked reduction of calcium blooming and beam-hardening artifacts. Multiple cadaveric, phantom, and in vivo studies demonstrate superior visualization of infrapopliteal vessels and stented arterial segments compared with energy-integrating and dual-energy CT systems. Reported sensitivity, specificity, and accuracy for PCCTA stenosis grading in PAD imaging reach approximately 96%, 97%, and 97%, respectively, incrementally exceeding those of conventional and dual-energy CT techniques, particularly in heavily calcified and below-the-knee vasculature. Optimization strategies, including sharp reconstruction kernels, high iterative reconstruction levels, and submillimeter slice thickness, further enhance diagnostic confidence. PCCTA also allows for substantial reductions in iodine contrast volume and radiation dose while maintaining diagnostic image quality. Conclusions: PCCTA represents a significant advancement in lower extremity arterial imaging for PAD. Improved visualization of small, calcified, and stented vessels enhances diagnostic accuracy, procedural planning, and postintervention surveillance. Although widespread adoption is currently limited by cost and scanner availability, emerging evidence suggests PCCTA may redefine cross-sectional imaging in PAD and improve patient-specific treatment strategies. However, further large-scale, prospective research is needed to establish the diagnostic benefits this modality in the clinical space.