Abdominal vascular and visceral parenchymal contrast enhancement in MDCT: effects of injection duration

To evaluate and compare the effect of short and long injection durations on aortic, pancreatic and hepatic enhancement in abdominal MDCT.

Triphasic contrast-enhanced CT images (16-MDCT, 1.25-mm collimation, 5-mm thickness, 6.1-s acquisition time for each phase) were obtained with 2 mL/kg injection of 300 mgI/mL iodine contrast material in 116 patients. Patients were prospectively randomized into two groups: one receiving contrast medium for 25-s injection duration and the other for 35-s injection duration. In both groups, triphasic scans were initiated 5, 15, and 40s after the completion of contrast injection for the first, second and third phases, respectively. CT values (HU) in the abdominal aorta, liver, spleen, pancreas, splenic and superior mesenteric arteries, and veins (splenic, superior mesenteric, portal, and hepatic) were measured. Quantitative and qualitative analysis for the degree of contrast enhancement between the two groups in various organs was compared at each scan phase.

The aortic and arterial enhancements in the first-phase scan were higher for the 25-s group than those of the 35-s group (P<.001). Hepatic enhancement was higher for the 35-s group in the first (P<.001) and second (P<.01) phases, but no difference in the third-phase. No difference was found between the groups for the pancreatic enhancement at any phases. Qualitative results were in good agreement with quantitative results.

Contrast administration with shorter injection duration increased peak aortic and arterial enhancement and contributed to improvement in the quality of CT angiograms, but for the solid abdominal organs 35-s protocol is recommended.