Objective To compare the image quality and radiation dose of conventional images obtained from single-source computed tomography (CT) scans with those of polyenergetic imaging (PEI) and virtual monoenergetic imaging (VMI) obtained from the dual-source upper abdominal contrast-enhanced CT scans of the same patients.

Methods Patients who underwent upper abdominal contrast-enhanced CT examinations using both single-source (120 kVp) and dual-source (70/150Sn kVp) protocols were retrospectively screened considering the change in the scanning protocol between November 2024 and March 2025. During this interval, no surgical procedures were performed, and there was no significant change in the patient's condition. Associated with the portal venous phase were conventional 120 kVp PEI images (CON) from a single-source CT scan as well as 120 kVp equivalent PEI images (MIX) and 70-keV VMI images from a dual-source CT scan. To calculate the signal-to-noise ratio (SNR), CT values in Hounsfield units (HU) and their standard deviations (SD) were measured at six anatomical sites, including the liver, spleen, abdominal aorta, portal vein, psoas major muscle, and anterior abdominal subcutaneous fat. The contrast-to-noise ratio (CNR) was calculated using the CT value and SD of the anterior abdominal subcutaneous fat as background noise. Subjective image quality was evaluated using a 5-point Likert scale to assess image noise, clarity, sharpness, and contrast. The scan radiation dose was recorded and the size-specific dose estimate (SSDE) was calculated. The differences in image quality and radiation dose among the different groups were compared.

Results The study included 34 patients with mean age±standard deviation of (68.1±10.8) years, of which 28 were male (82.4%). The average interval±standard deviation between the two examinations was (75.6±28.0) days. Objective measurements revealed significant differences in the SNR values of the abdominal aorta and portal vein among the different imaging groups, with higher SNR values in the MIX and VMI groups than in the CON group. No significant differences in the CNR values were observed for the liver, spleen, abdominal aorta, portal vein, or psoas major muscle among the different imaging groups. Subjective evaluations showed that all the images received scores above the requirements for clinical diagnostic use. No significant differences in image clarity were observed between the different imaging groups (P=0.519). Image noise was lower in the CON group than in the MIX and VMI groups. Image sharpness was lower in the VMI group than in the CON and MIX groups (P=0.003 and P=0.009, respectively), but image contrast was higher in the VMI group than in the CON and MIX groups. The SSDE of dual-source CT scans was significantly lower than that of the single-source CT scans.

Conclusion The comparison study on the same individuals eliminated the potential influence of individual differences and further confirmed that 120 kVp equivalent PEI images and 70keV VMI can reduce the radiation dose with image quality comparable to those of 120 kVp conventional PEI images. This study underscores the necessity of dual-source scanning and VMI reconstruction for contrast-enhanced CT of the upper abdomen.