Objective To explore the impact of Mono technology and resolution parameter in Mono+ technology on image quality with the goal of providing reference for the appropriate selection of these post-processing parameters in virtual monoenergetic images (VMI).

Methods The data included a computed tomography (CT) quality control phantom scanned in energy mode and portal venous phase data of contrast-enhanced upper abdomen energy CT scan of a sample patient. Mono and Mono+ technologies with different resolution parameters (1–10) and a default setting of 2 were used to reconstruct 70 keV VMIs. The noise power spectrum (NPS) was employed to analyze the image noise characteristics of both phantom and patient. The CT value, standard deviation (SD), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the liver parenchyma, and edge rise slope (ERS) between the liver parenchyma and portal vein were measured and calculated in the sample patient.

Results The NPS curves of the phantom showed that image noise was most pronounced with Mono technology and gradually increased with higher resolution parameters in Mono+ technology. The NPS curves for the patient exhibited a trend similar to that of the phantom. The average and peak spatial frequency values of NPS curves did not differ significantly and CT values of the liver parenchyma remained stable across different reconstruction techniques. However, the SD values of the liver parenchyma were lower at lower resolution parameters in Mono+ technology, corresponding to relatively higher SNR and CNR values. The ERS value between the liver parenchyma and portal vein was the lowest when the resolution parameter in Mono+ technology was 2. The ERS gradually increased as resolution increased.

Conclusion Mono+ technology can reduce image noise compared to Mono technology without significantly altering image texture. The increased resolution in Mono+ technology can improve image sharpness at the expense of higher image noise. Optimized SNR and CNR values can be obtained using the default resolution parameter settings of Mono+ technology, but the corresponding ERS may be low.