Effect of contrast concentration on abdominal enhancement in the rabbit: Spiral computed tomography evaluation

Rationale and Objectives.: We examined the effect of varying the concentration of a nonionic iodinated contrast agent on hepatic and abdominal vascular enhancement using spiral computed tomography (CT) scanning. Methods.: Spiral CT scans of 10 New Zealand male rabbits were obtained after intravenous injection of 240 mg I/ml iohexol and 350 mg I/ml iohexol injected at a rate of 2 ml/sec. Each animal was studied at both concentrations using four different contrast volumes: 2.3, 1.7, 1.1, and 0.57 ml/kg. Enhancement values of the aorta, hepatic veins, inferior vena cava, and hepatic parenchyma were measured using a region-of-interest cursor. Results.: At all contrast doses, equal volumes of contrast iohexol-350 resulted in statistically higher hepatic (p ≤ .003, paired Student's t test) as well as vascular (p < .04) enhancement compared with iohexol-240. The slopes and intercepts of the enhancement curves for iohexol-350 and iohexol-240 were not statistically different (p >> .05) when enhancement was plotted as a function of total grams of iodine administered. Conclusion.: With spiral CT scanning, appropriate contrast doses and relative costs per dose of iohexol should be considered on the basis of total iodine load administered rather than total volume administered.