Comparison of different injection forms in CT examination of the upper abdomen

Background: The optimal technique for administration of intravenous contrast medium in computed tomography (CT) remains controversial. Therefore, we analyzed the influence of variable-rate injection protocols. Methods: A double-blind, parallel-group study was conducted in 60 patients studied with the same helical CT contrast-enhanced protocol. Patients were randomly distributed into three groups: monophasic (123 mL at 2.5 mL/s), biphasic (123 mL, 60 mL at 1.5 mL/s and then 63 mL at 2.5 mL/s), and sigmoid (0.6 mL/s ending at 2.5 mL/s). Contrast-enhancement efficacy was evaluated by attenuation coefficient measurements. Results: The monophasic injection protocol produced a statistically higher liver, inferior vena cava, and portal enhancement than did the low–high biphasic and sigmoid protocols. The biphasic protocol produced a statistically higher enhancement in the superior aorta. The enhancement obtained with the monophasic protocol was always higher than or equal to those obtained with the biphasic protocol in all measurement protocols except in the superior aorta and the aortic bifurcation. Conclusions: A monophasic injection produces better parenchymal and venous enhancement. When arterial enhancement is important, a low–high biphasic protocol can be used. A sigmoid protocol, with the parameters used in our series, is significantly less effective.