CONTRAST ENHANCEMENT

Abstract

Our objective was to quantitatively demonstrate the superiority of intraarterial compared with intravenous injection of contrast media for the detection of malignant neoplasms by dynamic CT scanning and to describe contrast media uptake in tissue by a mathematical model. X-ray absorption values of malignant and normal tissues were measured by dynamic CT scanning following intraarterial and intravenous injection of contrast media in 4 rabbits with V2 carcinomas and in 2 humans with 4 liver metastases. X-ray absorption increased rapidly following injection, with maximum X-ray absorption and contrast enhancement of malignancies occurring during the first 30 seconds. Some lesions became isodense within a few minutes. The rabbit V2 carcinomas' X-ray absorption values increased 178 and 21 Hounsfield units following intraarterial and intravenous injection, respectively. X-ray absorption values for the 4 human metastases increased 117, 22, 385, and 369 Hounsfield units, respectively, following intraarterial injection, and 23, 16, 21, and 27 Hounsfield units, respectively, following intravenous injection. A simplified mathematical model is presented in which contrast media concentration in a tissue (C) is determined by C=CP(VD/VT)(1-e-tQ/VD) where CP is the plasma contrast media concentration, VD is the distribution volume of the contrast media in the tissue, VT is the total tissue volume, t is time, and Q is the plasma flow to the tissue. Dynamic CT data were then used to calculate values Q/VD for the tissues studied. For the time periods which were studied, the data fit the model. Intraarterial injection of contrast media gives quantitatively improved X-ray absorption and contrast enhancement of malignant tissues when compared with intravenous injection. The model presented is useful for understanding X-ray absorption patterns following either intraarterial or intravenous injection in terms of a few simple variables, and may be useful in tissue characterization. Supported by NIH grants CA 24879 and CA 05838, and the Eckstrom Trust.