[en] Purpose: To identify the benefits in image contrast enhancement using gold nanoparticles (AuNPs) compared to conventional iodinated contrast media. Materials and methods: Gold nanoparticles and iodinated contrast media were evaluated for contrast enhancement at various X-ray tube potentials in an imaging phantom. Iopromide and AuNP suspension were equalized according to molar concentration of radiopaque element (0.5077 Mol/L). Contrast-to-noise ratio is used to quantify contrast enhancement. Both projectional radiographic (40-80 kVp) and computed tomography (CT) (80-140kVp) imaging modalities were examined. Results and conclusions: Findings indicate 89% improvement in CNR at low energies near the mammographic range (40 kVp). However, as expected no significant difference in enhancement was observed at potentials commonly used for angiography (around 80 kVp) probably due to the k-edge influence for iodine. At the highest energies typically available in computed tomography, significant improvement in contrast enhancement using gold nanoparticles is obtained, 114% greater CNR than that produced by iodine at 140 kVp. Experimental findings for 70-120 kVp spectra correlate well with the theoretical calculations based on linear attenuation coefficients. Superior attenuation of gold nanoparticles at low and high kVp potentials support their further (pre)clinical evaluation.