Aortic and hepatic peak enhancement at CT: effect of contrast medium injection rate--pharmacokinetic analysis and experimental porcine model.

Abstract

To investigate the effect of injection rate of contrast medium on aortic and hepatic peak enhancement at computed tomography. Early pharmacokinetics of contrast enhancement was analyzed theoretically and simulated with a compartment model. Contrast enhancement curves were generated from the model at different injection rates (0.5-10.0 mL/sec). Time-enhancement curves were measured. The effect of contrast medium injection rate on the time and magnitude of peak enhancement was evaluated and validated empirically in pigs. Theoretic predictions and experimental results were in good agreement. Time to aortic peak enhancement was the sum of injection duration and bolus transfer time of contrast medium from the injection site to the aorta. Time to hepatic peak enhancement was the sum of injection duration and time to equilibrium. The magnitude of peak enhancement increased with the injection rate, but the increase was different in the aorta and liver. Use of injection rates above 2 mL/sec did not substantially increase hepatic peak enhancement but helped increase the magnitude of arterial enhancement and temporal separation of arterial and venous phases of enhancement for dual-phase spiral CT.