Multiphasic injection method for uniform prolonged vascular enhancement atCT angiography: Pharmacokinetic analysis and experimental porcine model

PURPOSE: To determine if multiphasic injection provides uniform, prolonged vascular contrast medium enhancement at computed tomographic (CT) angiograp hy. MATERIALS AND METHODS: With a computer-based, compartmental model of the ca rdiovascular system, theoretic analysis was performed to estimate an inject ion algorithm for uniform, prolonged vascular enhancement. For algorithm va lidation, four pigs were scanned after intravenous injection of 50 or 70 mL of contrast medium (282 mg of iodine per milliliter). Uni-, bi-, and multi phasic injection schemes were tested. In most cases, the initial injection rate was 2 mL/sec. In each CT study, 27 dynamic images were acquired every 2 seconds at a fixed mid-abdominal aortic level. Time-enhancement curves we re calculated. injection duration, peak aortic enhancement, and enhancement uniformity (duration of enhancement achieved within 90% of the peak [90% D CE]) were evaluated. RESULTS: Theoretic and experimental results agreed well. Compared with unip hasic injection, biphasic injection resulted in more prolonged enhancement but generated two enhancement peaks with a valley between, and multiphasic injection yielded more uniform and prolonged enhancement. With 50- and 70-m L multiphasic injections, respectively, injection duration increased by 32% and 51%, peak enhancement decreased by 19% and 18%, and 90% DCE increased by 81% and 94%. CONCLUSION: Uniform, prolonged vascular enhancement, which is desirable for CT angiography and essential for steady-state quantification of blood volu me in organs, can be achieved with multiphasic injection.