Operation of bolus tracking system for prediction of aortic peak enhancement at multidetector row computed tomography: pharmacokinetic analysis and clinical study

Abstract

The present study was performed to identify the theoretical background for optimal use of the bolus tracking system by analyzing the changes in the initial slope of the aortic time-enhancement curve (TEC). We calculated the contrast medium aortic arrival time (TAR), the time to reach the trigger threshold (effective TAR), the slope of the linear equation of the enhancement unit (enhancement rate), and the time to peak aortic enhancement from the TECs of the pharmacokinetic analysis and retrospective clinical study. In the pharmacokinetic analysis, the enhancement rate-simulated under conditions of injection duration 30 s and iodine load per body weight 500 mg/kg-was 27.1 HU/s. In the clinical study, the enhancement rate was 27.9 +/- 3.0 HU/s. A correlation was found between the TAR and the enhancement rate, indicating that enhancement rates decrease with increasing TAR. It took 22.7 +/- 0.5 s to reach maximum enhancement of the aorta from the trigger threshold of an increase of 100 HU and injection duration at 30 s. We found that cardiac output differences are strongly dependent on the TAR and that most of the differences disappeared during the phase until effective TAR.