Aortic and hepatic contrast medium enhancement at CT. Part I. Prediction with a computer model

To develop a physiologic model of contrast medium enhancement by incorporating available physiologic data and contrast medium pharmacokinetics and to predict organ-specific contrast medium enhancement at computed tomography (CT) with various contrast medium injection protocols in patients of variable height and weight.

A computer-based, compartmental model of the cardiovascular system was generated by using human physiologic parameters and more than 100 differential equations to describe the transport of contrast medium. Blood volume, extracellular fluid volume, and regional blood flow were estimated from available data. Local structures were modeled mathematically to describe the distribution and dispersion of intravascularly administered iodinated contrast medium. A global model was formed by integrating regional circulation parameters with the models of local structures. Aortic and hepatic CT contrast-enhancement curves were simulated for three protocols and were compared with mean enhancement curves in three groups of 25-28 patients (80 patients total; 28 in one group, 25 in one group, and 27 in one group) receiving the same protocols. The percent difference in maximum enhancement between the simulated and empiric curves and the enhancement difference index (sum of the area difference between the simulated and empiric curves divided by the total area under the empiric curve) were computed.

The simulated and empiric enhancement curves closely agreed in maximum enhancement (the mean percent difference in the aorta was 7.4%; liver, 4.8%) and in variation over time (mean enhancement difference index in the aorta was 11.6%; liver, 12.7%).

A computer-based, physiologic model that may help predict organ-specific CT contrast medium enhancement for different injection protocols was developed. Such a physiologic model may have many clinical applications.