Comparison of false positive rates and radiation exposure in dual-source vs. photon-counting cardiac CT for detecting severe coronary stenosis: a retrospective cohort study

Background Cardiac computed tomography angiography (CCTA) is a key non-invasive tool for assessing coronary artery disease (CAD). The 2024 European Society of Cardiology (ESC) guidelines highlight its growing role, particularly for patients with low to moderate pre-test probability. However, its high sensitivity can lead to false positive (FP) findings, resulting in unnecessary invasive coronary angiographies (ICA). Photon-counting computed tomography (PC-CT) offers potential benefits over standard dual-source CT (DS-CT), including improved resolution, enhanced contrast, and lower radiation exposure. This study compares DS-CT and PC-CT in terms of FP rates and radiation dose. Purpose This study aims to compare false positive rates and radiation exposure between DS-CT and PC-CT in detecting severe coronary stenosis. By assessing diagnostic accuracy and radiation dose, we seek to determine whether PC-CT offers advantages over DS-CT in clinical practice. Methods This retrospective cohort study included consecutive patients between 2019 and 2024 who underwent CCTA for suspected CAD with a positive finding for severe coronary stenosis. Patients who had ICA at the same institution within three months of CCTA were included. A positive CCTA result was defined as 70–99% stenosis in a major coronary artery or bypass graft, left main artery stenosis of 50% or more, three-vessel disease with stenosis of 70% or more, or chronic total occlusion. Significant stenosis on ICA was defined as at least 50% stenosis in the left main coronary artery, at least 70% stenosis in a major coronary artery or bypass graft, or stenosis between 30–70% with physiological significance (FFR ≤0.8 or iFR ≤0.89). False positive rates between DS-CT and PC-CT were compared using chi-square tests, while radiation exposure was assessed by dose-length product (DLP, mGy×cm). A binomial logistic regression model evaluated differences between imaging techniques. Baseline characteristics, including BMI and calcium score, were similar between groups. Results 261 patients met the inclusion criteria, of which 141 (54.0%) underwent DS-CT and 120 (46.0%) underwent PC-CT. The FP rate was higher in DS-CT (40/141, 15.3%) compared to PC-CT (20/120, 7.7%) (p=0.025). Radiation exposure, measured as DLP, was significantly lower in PC-CT compared to DS-CT. The mean DLP for PC-CT was 271 mGy×cm (range: 50–1386), whereas for DS-CT, the mean DLP was 402 mGy×cm (range: 27–1974). This difference was statistically significant (p=0.031), indicating a substantial reduction in radiation dose with PC-CT. Conclusion PC-CT demonstrated a lower false positive rate and significantly reduced radiation exposure compared to DS-CT in the assessment of high-degree coronary stenosis. These findings suggest that PC-CT may improve the diagnostic specificity of CCTA while minimizing radiation exposure, making it a valuable advancement in non-invasive coronary imaging.