Assessing coronary in-stent restenosis using ultrahigh-resolution photon-counting detector CT: results from a two-center study

INTRODUCTION: To assess the diagnostic accuracy of ultrahigh-resolution (UHR) photon-counting detector (PCD)-CT for detecting obstructive and non-obstructive coronary in-stent restenosis (ISR), using invasive coronary angiography (ICA) as the reference. METHODS: Consecutive patients with coronary stents who underwent clinically indicated coronary CT angiography (CCTA) on a dual-source PCD-CT were retrospectively identified from two academic centers. All UHR scans were reconstructed at 0.2 mm and 0.4 mm slice thickness, the latter served as an energy-integrating detector CT-like proxy. Series were assessed for the presence of non-obstructive (<50%) and obstructive (≥50%) ISR, with diagnostic accuracy validated against ICA in the overall cohort and in a sub-analysis of stents < 3 mm in diameter. RESULTS: Fifty patients (16.0% women; 70.9 ± 10.8 years) with 106 coronary stents were included. ICA identified 17 non-obstructive and 27 obstructive ISR. Non-obstructive ISR was detected in 10 stents on 0.2 mm UHR and 14 on 0.4 mm EID-like standard-resolution reconstructions.Obstructive ISR was described in 26 (0.2 mm) vs. 32 (0.4 mm) stents, respectively. The proportion of evaluable stents increased from 91.5% based on 0.4 mm to 99.1% with 0.2 mm UHR. Compared with standard-resolution images, 0.2-mm UHR improved non-obstructive ISR sensitivity (90.5%vs82.9%), specificity (100.0%vs78.5%), and accuracy (96.2%vs80.2%); and in obstructive ISR, specificity (98.7%vs82.3%), positive predictive value (96.3%vs64.1%), and accuracy (98.1%vs84.9%). Thin-slice UHR achieved higher accuracy in small-caliber stents (<3mm), for both non-obstructive (94.1vs73.5%) and obstructive ISR (94.1%vs79.4%). CONCLUSION: UHR PCD-CT demonstrated excellent diagnostic accuracy and significant improvements in ISR detection compared to the quasi-standard reconstructions, including non-obstructive and small-caliber stent ISR.