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 less than or equal to .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 much greater than .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.