DOSE REQUIREMENTS FOR A NONIONIC CONTRAST AGENT FOR SPIRAL COMPUTED-TOMOGRAPHY OF THE LIVER IN RABBITS

RATIONALE AND OBJECTIVES. The purpose of this study was to determine the relationship between intravenous dose of a nonionic contrast agent and hepatic enhancement using spiral computed tomography. METHODS. The enhancement of the liver, hepatic vein, inferior vena cava, and aorta was evaluated in the New Zealand male rabbit after intravenous injection of iohexol, 300 mg iodine (I)/mL, at 2 mL/sec. Spiral computed tomography scans of 10 animals were evaluated at each of nine different contrast doses (857, 771, 686, 600, 514, 429, 343, 257, and 171 mg I/kg) for a total of 90 spiral scans. RESULTS. Hepatic attenuation was linearly proportional to the contrast dose over the range of doses examined. The average change in attenuation of the liver from the first to the last scanned portion of the liver ranged from 0 to 7 Hounsfield Units (HU) (standard deviation ranging from 4 to 11 HU). Hepatic venous enhancement was greater than that of the liver for doses greater than 171 mg I/mL. The aortocaval difference in enhancement was greater than 10 HU in all cases. CONCLUSION. A dose of 429 mg I/kg, providing an average hepatic enhancement greater than 30 HU, is predicted to be the lower dose limit for hepatic parenchymal enhancement using spiral computed tomography.