Abstract: Objective: We compared image quality from a low-iodine-load coronary computed tomography angiography (CCTA) protocol with that from a standard protocol using spectral CT virtual monoenergetic imaging (VMI), while maintaining a similar iodine delivery rate (IDR). Methods: In this prospective trial, we randomized 80 patients into low-dose (LD, n=40; 45 mL, 370 mgI/mL) or standard-dose (SD, n=40; 70 mL, 300 mgI/mL) CCTA protocols with near-identical IDRs. All underwent dual-layer spectral CT. Conventional images (CI) and 40-80 keV VMI series were reconstructed. Two radiologists performed objective (CT values, noise, SNR, CNR) and subjective analyses using non-parametric tests. Results: The optimal energy window was determined to be 40−50 keV, where the contrast-to-noise ratio (CNR) peaked. In both groups, low-energy VMI yielded significantly better image quality (higher CNR/SNR, lower noise) than CI. While the SD group had higher CT values on CI, their CNR and SNR were not significantly different from those from the LD group. Crucially, at the optimal 50 keV window, no significant differences between LD and SD groups were found in any objective or subjective image quality metrics. Conclusion: If a similar IDR is maintained, a low-iodine-load CCTA protocol combined with optimized VMI can achieve comparable diagnostic image quality to that obtained with a standard-load protocol, supporting its use for safer CCTA examinations.