Abstract: Objective: To explore the diagnostic value of dual-energy computed tomography (DECT) combined with standardized iodine concentration (NIC) for assessing the degree of lower-extremity artery stent stenosis. Methods: A retrospective study was conducted on 32 patients with 48 stents who underwent dual-energy lower-extremity CTA at our hospital between January 2020 and June 2024. All patients underwent DSA within one week of CTA. Dual-energy data were reconstructed into five sets of virtual monochromatic images from 50～90 keV with 10 keV intervals, along with one set of optimum contrast (OCM) images. The CT, SD, CNR, SNR, and NIC values within the stent lumen were measured and compared, and subjective image quality evaluations were performed. The diagnostic accuracy of DECT for lumen stenosis rate and in-stent restenosis (ISR) was evaluated using DSA as the gold standard. Results: The SNR and CNR values were highest at 50 keV, gradually decreasing as the monochromatic energy level increased. The SNR and CNR values of the OCM and 60 keV groups were slightly lower than those of the 50 keV group, though were not significantly different. There were significant differences in the subjective evaluation scores among the six groups. The OCM (4.23±0.89) and 60 keV (4.19±0.64) groups had the highest scores but were not significantly different. Compared with DSA, DECT had moderate consistency in diagnosing lumen stenosis rate and ISR (kappa=0.563 and 0.654, respectively). DECT combined with NIC showed good consistency in ISR diagnosis (kappa=0.830). The NIC values were 1.02±0.14 for no significant stenosis, 0.73±0.14 for ISR, and 0.18±0.09 for occlusive lesions. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the combined diagnosis were 94.11%, 85.71%, 94.11%, 85.71%, and 91.66%, respectively. Conclusion: DECT reconstructed at 60 keV and OCM images were best for assessing lower-extremity artery stent stenosis. Combining quantitative analysis with NIC can improve the accuracy of grading stent lumen stenosis and judging ISR, which has high diagnostic value.