Introduction:
Invasive coronary angiography (ICA) remains the gold standard for diagnosing significant coronary artery stenosis (>70%) in patients with acute coronary syndrome (ACS). However, ICA provides limited information on plaque morphology and vessel wall composition. Intravascular imaging modalities such as optical coherence tomography (OCT) allow detailed assessment of plaque structure and vessel characteristics, but they are invasive and restricted to the interrogated vessel segment. Non-invasive coronary computed tomography angiography (CCTA) enables plaque visualization, yet image quality is often impaired in patients with extensive calcification or coronary stents. Photon-counting computed tomography (PCCT) is an emerging detector technology offering superior spatial resolution, reduced noise, and improved material differentiation compared to conventional CT. These advances may enable accurate non-invasive evaluation of coronary stenosis and plaque morphology, potentially overcoming current CCTA limitations. The present study aimed to assess the diagnostic accuracy of PCCT for coronary artery stenosis and plaque characterization using ICA and OCT as reference standards.
Methods:
This ongoing prospective single-center pilot study enrolls clinically stable patients with suspected ACS classified as low- to intermediate-risk non-ST-elevation myocardial infarction or unstable angina prior to planned ICA within 24–72 hours. Recruitment started in January 2025 and continues beyond October 2025. All patients underwent PCCT before ICA, and OCT was performed during ICA where feasible. Stenosis severity is assessed per segment, per vessel, and per patient according to the Coronary Artery Disease – Reporting and Data System (CAD-RADS 2.0) and quantitatively compared with ICA. Plaque characterization includes classification by composition and evaluation of high-risk features (positive remodeling, spotty calcification, napkin-ring sign, and low-attenuation plaque), with comparisons performed between PCCT and ICA for stenosis assessment and between PCCT and OCT for plaque morphology.
Results:
Preliminary data include 39 participants (mean age 69.2 ± 11.0 years; 71.8% male). OCT was performed in 17 cases (43.6%). On a patient-based analysis, PCCT correctly identified all patients with hemodynamically relevant coronary stenoses, yielding a sensitivity of 100%. Negative predictive values (NPVs) were consistently high (>95%). Correlation of plaque morphology between PCCT and OCT is ongoing. Further analyses will include segment-based evaluations and comprehensive statistical validation using dedicated analysis software in collaboration with expert readers.
Conclusion:
Preliminary findings indicate that PCCT provides promising diagnostic performance for the non-invasive assessment of coronary artery stenosis in patients with suspected ACS. The high NPV suggests that PCCT may reliably exclude hemodynamically relevant stenoses. Ongoing analyses will address PCCT–OCT correlations for high-risk plaque features and explore the potential of PCCT for comprehensive non-invasive plaque characterization. The study is expected to be completed by April 2026, and additional biobanking will support future translational and mechanistic investigations.
