Detection and Characterization of Infundibula and Aneurysms: A Clinical Report–Based Comparison of PCD- and EID-CTA

BACKGROUND AND PURPOSE: Photon-counting detector CT angiography (PCD-CTA) offers higher spatial resolution than energy-integrating detector CTA (EID-CTA), but its impact on clinical reporting of arterial outpouchings in head/neck CTA is unknown. We compared paired EID-CTA and PCD-CTA reports for concordance in lesion detection and characterization (aneurysm vs infundibulum vs uncertain). MATERIALS AND METHODS: We retrospectively identified adults with paired head and neck PCD-CTA and prior EID-CTA within 2 years in which either report described an arterial outpouching. Exclusions included previously treated lesions and EID-CTA slice thickness >0.6 mm. PCD-CTA used 120 kV, 120×0.2 mm collimation, Hv56-3 kernel, and 0.2 mm slices. Lesions were categorized based on clinical reports as aneurysm, infundibulum, uncertain, pseudo-lesion, or not identified. Concordance was assessed per-lesion and per-patient. RESULTS: Twenty-nine patients (mean age 658±15 years; 72% female) with 42 outpouchings were included. Mean interval between scans was 320 days. Per-lesion concordance was 57% (24/42). Eight outpouchings (19%) reported on PCD-CTA were not described on EID-CTA, including 4 aneurysms, 3 infundibula, and 1 uncertain lesion. Of 9 EID-CTA uncertain lesions, PCD-CTA reclassified 6 (2 aneurysms, 2 infundibula, 2 pseudo-lesions (one from overlapping vessels and one from calcification). Of 24 EID-CTA aneurysms, 4 were reclassified on PCD-CTA (2 infundibula, 2 uncertain). Per-patient concordance was 48% (14/29); discordance was higher in multi-lesion (78%, 7/9) than single-lesion patients (40%, 8/20). CONCLUSIONS: PCD-CTA frequently detected/reported aneurysms and infundibula not seen or incompletely characterized on EID-CTA. Routine PCD-CTA for head/neck CTA may refine surveillance and treatment decisions for unruptured aneurysms while reducing unnecessary workup of infundibula and pseudo-lesions.