Abstract: Objective To evaluate the diagnostic accuracy of ultra-high-resolution coronary computed tomography angiography (CCTA) using photon-counting CT (PCCT) in elderly patients with coronary artery disease (CAD). Methods A retrospective analysis was conducted on 57 patients (mean age 70.9±6.4 years, 43 males) who underwent both ultra-high-resolution PCCT-CCTA and invasive coronary angiography (ICA) at Geriatric Hospital of Nanjing Medical University from July 2024 to January 2025. With ICA as the gold standard, the consistency between PCCT-CCTA and ICA was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. The diagnostic performance (sensitivity, specificity, accuracy) of CCTA reconstructions at 0.2 mm, 0.4 mm, and 0.8 mm slice thickness was calculated, with stenosis ≥50% considered hemodynamically significant. Results ICC analysis indicated excellent consistency between CCTA and ICA at the 0.2 mm segment-level (ICC=0.98, 95%CI: 0.97－0.98). Bland-Altman analysis showed a mean bias of －0.44%, with 95% limits of consistency ranging from －12.39% to 11.52%. The diagnostic performance of CCTA exhibited an inverse relationship with slice thickness. The 0.2 mm reconstruction demonstrated superior diagnostic performance at both the segment level and vessel level. Conclusions In elderly CAD patients, CCTA based on photon-counting CT shows high consistency with ICA for quantifying coronary artery stenosis. The Ultra-high-resolution reconstruction mode (0.2 mm) provides superior diagnostic accuracy, which could be used as a reliable noninvasive imaging method for coronary stenosis evaluation.

Key words: aged, coronary artery disease, photon-counting CT, coronary CT angiography, invasive coronary angiography, diagnostic accuracy