Optimizing coronary CT angiography with spectral dual-layer CT: motion-compensated virtual monoenergetic imaging achieves 50% contrast dose reduction in a phantom study.

Reduced contrast media (CM) dose at elevated heart rates (HRs) poses a challenge for coronary artery disease (CAD) assessment. Using a dynamic phantom, we evaluated the performance of a vendor-specific coronary motion-compensated reconstruction (MCR) at various simulated HRs and reduced CM dose in low virtual monoenergetic images (VMIs) from coronary computed tomography angiography (CCTA). A clinical CCTA protocol was used to image a 5-mm artificial coronary artery, filled with 100% (400 Hounsfield units (HU)) and 50% CM dose, using a robotic arm for translation at six velocities (0-50 mm/s, 10 mm/s steps). Conventional images and VMIs (40-70 keV, 10 keV steps) were reconstructed without and with MCR. The study evaluated the MCR influence on motion area and contrast-to-noise ratio (CNR) of the resulting segmented arteries (motion area), with the static conventional reconstructed artery at 100% CM dose as the reference, and non-overlapping 95% confidence intervals with the reference indicating significant differences. At 50% CM dose, motion area increased significantly (up to 50%) at elevated velocities (≥ 30 mm/s) without MCR, while no significant variations were observed with MCR. Additionally, without MCR, VMIs exhibited significant CNR decreases (up to 65%) at velocities ≥ 30 mm/s. Only the combination of MCR and 40 keV VMI achieved CNR comparable to the reference, regardless of HR. The combination of MCR with low VMIs enables 50% CM dose reduction, with similar motion area and CNR when compared to conventional CCTA with 100% CM dose. These parameter settings can potentially be used to optimize low CM dose CCTA at higher HRs.