AORTIC AND HEPATIC CONTRAST-MEDIUM ENHANCEMENT AT CT PART-I - PREDICTION WITH A COMPUTER-MODEL

PURPOSE: To develop a physiologic model contrast medium enhancement by incorporating available physiologic data and contrast medium pharmaco kinetics and to predict organ-specific contrast medium enhancement at computed tomography (CT) with various contrast medium injection protoc ols in patients of variable height and weight. MATERIALS AND METHODS: A computer-based, compartmental model of the cardiovascular system was generated by using human physiologic parameters and more than 100 dif ferential equations to describe the transport of contrast medium. Bloo d volume, extracellular fluid volume, and regional blood flow were est imated from available data. Local structures were modeled mathematical ly to describe the distribution and dispersion of intravascularly admi nistered iodinated contrast medium. A global model was formed by integ rating regional circulation parameters with the models of local struct ures. 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, 2 5 in one group, and 27 in one group) receiving the same protocols. The percent difference in maximum enhancement between the simulated and e mpiric curves and the enhancement difference index (sum of the area di fference between the simulated and empiric curves divided by the total area under the empiric curve) were computed. RESULTS: The simulated a nd empiric enhancement-curves closely agreed in maximum enhancement (t he mean percent difference in the aorta was 7.4%; liver, 4.8%) and in variation over time (mean enhancement difference index in the aorta wa s 11.6%; liver, 12.7%). CONCLUSION: A computer-based, physiologic mode l that may help predict organ-specific CT contrast medium enhancement for different injection protocols was developed. Such a physiologic mo del may have many clinical applications.