Effects of High-concentration contrast material and low-voltage CT on contrast for multiphasic CT of the upper abdomen: comparison using the simulation with virtual monochromatic imaging obtained by fast-switch kVp dual-energy CT

OBJECTIVE: The purpose of this study was to compare the effects of high-concentration contrast material and low-voltage CT simulated by virtual monochromatic (VM) imaging on contrast enhancement at multiphasic CT of the upper abdomen. METHODS: This study included 72 patients who underwent CT during early arterial (EAP), late arterial and portal venous phases after 300-mgI/ml (Group A; 34 patients) or 350-mg/ml (Group B; 38 patients) contrast-material injection at the same volumetric rate (0.067 mL/sec/kg). VM images were generated at 50 and 65 keV. Contrast-to-noise ratios (CNRs) of aorta, portal vein, and liver parenchyma were calculated and statistically compared. RESULTS: Mean CNRs for 50-keV VM images were significantly higher than 65-keV VM images of each organ at any phases (p < 0.05), except for hepatic parenchyma in EAP. Aortic CNRs in EAP on 65- and 50-keV images of Group B were significantly higher than Group A (p <0.05, respectively). Aortic CNR on 50-keV images of Group A and on 65-keV images of Group B were 11% and 21% higher than 65-keV images of Group A, respectively. CONCLUSIONS: Low-voltage CT simulated by VM image improved contrast enhancement through any phases, while high-concentration contrast material increased only arterial contrast in EAP more effectively.