Stability of spectral results in cardiac dual-source photon-counting CT

Objective: Evaluate stability of spectral results at different heart rates, acquisition modes, and cardiac phases in first-generation clinical dual-source photon-counting CT (PCCT). Materials and Methods: A cardiac motion simulator with a coronary stenosis mimicking a 50% eccentric calcium plaque was scanned with a first-generation dual-source PCCT at five different heart rates (0, 60, 70, 80, 100 bpm). Scans were performed at 120 kVp with the three available cardiac scan modes (high pitch prospectively ECG-triggered spiral, prospectively ECG-triggered axial, retrospectively ECG-gated spiral). Subsequently, virtual monoenergetic images at 50, 70, and 150 keV and iodine density maps were reconstructed at both diastole and systole to investigate the effect of the cardiac phase. Full width half max (FWHM) of the stenosis, Dice score (DSC) for the stenosed region, and eccentricity of the non-stenosed region were analyzed. Results: FWHM exhibited average differences from the static FWHM across cardiac phase and heart rates of -0.20, -0.28, and -0.15 mm at VMI 150 keV for high pitch prospectively ECG-triggered spiral, prospectively ECG-triggered axial, and retrospectively ECG-gated spiral scans, respectively. DSC demonstrated similarity among parameters with standard deviations of 0.08, 0.09, 0.11, and 0.08 for VMI 50, 70, and 150 keV, and iodine density maps, respectively, with larger differences present at systole and with high pitch scans. Similarly, eccentricity illustrated small differences across heart rate and acquisition mode for each spectral result. Conclusions: Consistency of spectral results at different heart rates and acquisition modes for different cardiac phase demonstrates the added benefit of spectral results from PCCT to dual-source CT to further increase confidence in quantification and advance cardiovascular diagnostics.