Diagnostic Performance of Photon-counting Detector CT Angiography in the Detection of Cerebral and Carotid Artery Stenosis

BACKGROUND AND PURPOSE: The diagnostic performance of ultra-high-resolution (UHR) photon-counting detector CT angiography (PCD-CTA) for evaluating cerebral and carotid artery stenosis remains unclear. This study aimed to compare UHR PCD-CTA with standard resolution (SR) CTA for stenosis assessment, using digital subtraction angiography (DSA) as the reference standard. MATERIALS AND METHODS: In this cohort study, participants with suspected cerebral and carotid artery stenosis, who were indicated for CTA examination were prospectively enrolled from September 2023 to April 2024. All participants were examined with a photon-counting CT scanner, and both UHR and SR CTA reconstructions were generated from the same raw data. The quantitative diameter stenosis (DS) was computed for each lesion by blinded independent reading. The correlation and agreement analyses were performed using DSA as the reference standard. Stenosis was graded into four categories (<30%, 30-50%, 50-70%, ≥70%), with categorical agreement assessed using weighted kappa statistics. RESULTS: Among 40 participants (age: 63.2 ± 9.2 years; 16 males), a total of 54 stenoses were recorded (DS: 44.1 ± 18.4%). Compared with SR CTA, UHR PCD-CTA demonstrated significantly stronger correlation (r=0.94 [95%CI: 0.90-0.97] vs. r=0.70 [95%CI: 0.54-0.82], P<.001) and agreement (mean difference: -0.00 ± 0.06 vs. 0.01 ± 0.14, variance difference test P<.001) with DSA in evaluating DS. Across four stenosis categories, UHR CTA demonstrated significantly higher overall accuracy (77.8% vs. 53.7%, P=.004) and stronger agreement with DSA (weighted κ = 0.79 vs. 0.53, P=.004) compared to SR CTA. In calcified lesions, UHR CTA remained significantly higher agreement with DSA than SR CTA (weighted κ = 0.76 vs. 0.35, P=.001). In lesions with small residual lumen (minimum lumen diameter≤2.0mm), UHR CTA showed no significant deviation from DSA (-0.02 ± 0.06, P=.10), whereas SR CTA significantly underestimated stenosis severity (-0.06 ± 0.12, P=.03). CONCLUSIONS: UHR PCD-CTA showed superior correlation and agreement with DSA compared with SR CTA in the assessment of cerebral and carotid artery stenosis, with particular advantages in calcified lesions and vessels with small residual lumen. These findings support its role as a reliable non-invasive tool for cerebrovascular stenosis assessment, with direct implications for clinical management and treatment decisions.