Application of pharmacokinetics to electron-beam tomography of the abdomen

Rationale and Objectives. The purpose of this study was to evalute the phar macokinetics of abdominal time-attenuation curves obtained at electron-beam tomography. Materials and Methods. Computed tomographic enhancement data of the aorta, portal vein, vena cava, liver, spleen, and pancreas were obtained in 25 pat ients after injection of 50 mL of contrast medium. These data were used to calculate pharmacokinetic parameters such as half-lives, mean residence tim es, and areas under the curve with a computer program. Results, Maximal enhancement was observed in the aorta 24 seconds +/- 5 (me an +/- standard deviation) after starting the injection of contrast medium (178 HU +/- 56), in the portal vein after 42 seconds +/- 14 (60 HU +/- 17), in the vena cava after 35 seconds +/- 7 (66 HU +/- 23), in the liver after 58 seconds +/- 15 (24 HU +/- 6), in the spleen after 35 seconds +/- 12 (42 HU +/- 16), and in the pancreas after 39 seconds +/- 15 (42 HU +/- 10). Ha lf-lives of the last phase observed were 108 seconds +/- 123 in the aorta, 33 seconds +/- 30 in the portal vein, 49 seconds +/- 40 in the vena cava, 5 0 seconds +/- 54 in the liver, 62 seconds +/- 33 in the spleen, and 22 seco nds +/- 27 in the pancreas. The computer program allowed for excellent fitt ing curves to the measured attenuation values and for subsequent calculatio n of pharmacokinetic parameters. New dosage regimens also could be simulate d successfully. Conclusion. The pharmacokinetic parameters evaluated might be useful in the optimization of dosing and scanning parameters of the abdomen for ultrafas t and helical CT.