Abstract: Objective: This study aimed to compare and analyze the effects of different keV values of dual-source computed tomography (CT) noise-optimized virtual monoenergetic imaging (VMI+) on the quality of portal vein imaging in patients with portal hypertension and to determine the optimal keV value for VMI+. Methods: Postprocessing was performed on portal venous phase images of 37 patients with portal hypertension who underwent dual-source CT. The VMI+ technique was used to reconstruct nine groups of monoenergetic images at 40, 45, 50, 55, 60, 65, 70, 75, and 80 keV. Compared with the standard mixed images automatically generated with a linear blending coefficient of 0.6 (M-0.6), the CT values and standard deviation of the main portal vein (MPV) and liver parenchyma were measured for each group of images. The signal-to-noise ratio (SNR) of the MPV and the contrast-to-noise ratio (CNR) with the liver parenchyma were calculated. On the maximum intensity projection images of the portal venous phase, the luminal diameters of the MPV, splenic vein (SPV), left branch of the portal vein (IHLPV), and right branch of the portal vein (IHRPV) were measured, and the number of detected cases of diseased vessels in each image group was recorded. Objective evaluation was conducted using analysis of variance. Subjective evaluation was performed by two deputy chief radiologists who used a five-point scale to assess the contrast effect of the MPV against the background liver parenchyma and the overall image quality in the 10 groups of images. Results: The CT value, SNR, CNR of the MPV, and subjective image scores measured for the 40 ~ 65 keV portal vein groups were higher than those for the M-0.6 group, and the difference was statistically significant. The CT value, SNR, CNR of the MPV, and subjective image scores measured for 70 keV images were similar to those of the M-0.6 group, with no statistical difference. The CT value, SNR, CNR of the MPV, and subjective image scores measured for the 75 and 80 keV groups were lower than those for the M-0.6 group, and the difference was statistically significant. The diameters of the MPV, IHLPV, IHRPV, and SPV were the same among all the groups, and the same number of pathological vessels were detected, with no statistical significance. Among them, the 40 keV group had the highest CT values, SNR, and CNR of the MPV among all 10 groups. Conclusion: The application of VMI+ technology (40 ~ 65 keV) in dual-source CT significantly improves the portal-vein image quality of patients with portal hypertension, which is beneficial for displaying portal vein vessels. The optimal monoenergetic energy level is 40 keV.