Photon-Counting CT-Angiography to Assess Intracranial Stents and Flow Diverters in Comparison to Digital Subtraction Angiography.

Purpose Photon-Counting Detector CT is characterized by enhanced image post-processing capabilities. The diagnostic accuracy of PCD-CT angiography (PCD-CTA) in assessing intracranial stents (ICS) and flow diverters (FD) has yet to be compared with digital subtraction angiography (DSA).Methods Retrospective analysis of all consecutive patients who underwent ICS or FD implantation between April 2023 and May 2024. Polyenergetic images, along with virtual monoenergetic imaging (VMI), pure lumen (PL) and iodine (IOD) reconstructions were assessed by three readers using a 5-point Likert scale and defined regions of interest (ROIs). A blinded analysis was performed to identify relevant lumen reduction. The diagnostic accuracy of PCD-CTA was compared to DSA by calculating the area under the receiver operating characteristic curve.Results A total of 18 patients (mean age 59 ± 13 years; 14 women) with 14 implanted ICS and 10 FD were analyzed. Across all pairwise comparisons, pooled VMI reconstructions demonstrated higher ratings and signal-to-noise ratios compared to IOD, PL and UHR reconstructions (p < 0.001 for all comparisons). In the pooled assessment of DSA of in-stent vessel lumen 18 (11%) of the 162 vessel segments and 6 (33%) of the 18 patients presented relevant narrowing of the in-stent vessel lumen. The sensitivity of PCD-CTA for detecting stenosis was 100% (18 of 18 in-stent vessel segments), while specificity was 89% (128/144 in-stent vessel segments). All readers reported a 100% negative predictive value (128/128 in-stent vessel segments).Conclusion Photon-Counting Detector CT might provide a reliable assessment of intracranial vessels following stent or flow diverter implantation comparable to DSA in many cases.