Iodine maps from photon-counting detector CT in thoracic imaging: a scoping review

Photon-counting detector CT (PCD-CT) acquires spectral data at every scan, enabling iodine map reconstruction without dedicated dual-energy protocols. This scoping review mapped the extent, characteristics, and findings of early clinical studies. Following the Joanna Briggs Institute framework and PRISMA-ScR reporting, MEDLINE, Embase, and Web of Science were searched through February 2026 for original clinical data on PCD-CT iodine maps in thoracic imaging. Two reviewers screened independently. Outcomes were prespecified as findings attributable to the iodine map, technical performance, or patient-level clinical impact. Ten single-center studies including 832 patients (722 with PCD-CT examinations; ≤ 696 unique after overlap; 2022–2025) were included; six were retrospective and six used prototype or pre-release post-processing software. Diagnostic accuracy against an external reference was 0.85–0.88 for chronic thromboembolic pulmonary hypertension (CTEPH), 96% for empyema, and 85% per-patient for late iodine enhancement; extracellular volume correlated with cardiac MRI at r = 0.88–0.96. PCD-CT used 13–26% lower doses than EID-DECT in acute pulmonary embolism and ~80% lower than SPECT/CT in CTEPH. In the only direct comparison, iodine map quality did not differ between PCD-CT and EID-DECT. No study reported patient-level clinical outcomes. Early evidence derives from small single-center cohorts, with substantial heterogeneity. The distinguishing PCD-CT contribution is the workflow advantage of generating iodine maps from every acquisition, including high-pitch protocols incompatible with conventional dual-energy, rather than superior accuracy. CTEPH perfusion assessment shows the most internally consistent evidence. Multicenter prospective studies with pre-specified clinical endpoints are needed before adoption. Question Iodine maps from PCD-CT are increasingly reported in thoracic imaging, but their clinical applications and remaining evidence gaps have not been systematically mapped. Findings Across 10 single-center studies in six thoracic indications, PCD-CT iodine maps showed favorable accuracy vs external references, with heterogeneous protocols and software. Relevance statement Early evidence supports PCD-CT iodine maps for thoracic imaging; multicenter studies with standardized protocols and patient-level endpoints are needed before routine adoption.