PROLONGATION AND OPTIMIZATION OF DOPPLER ENHANCEMENT WITH A MICROBUBBLE US CONTRAST AGENT BY USING CONTINUOUS-INFUSION - PRELIMINARY EXPERIENCE

PURPOSE: To investigate whether continuous infusion of echo-enhancing contrast agent for up to 15 minutes can provide uniform and prolonged enhancement. MATERIALS AND METHODS: Six volunteers each received one b olus and three infusions of a microbubble contrast agent over 6-15 min utes at (a) a standard rate (mean, 2.08 mL/min), (b) a fast rate at tw ice the standard rate, and (c) a slow rate at half the standard rate. Spectral Doppler intensitometry of the femoral artery was performed fo r all infusions. Spectral Doppler ultrasound (US) scans of the femoral artery and color Doppler US scans of the carotid artery were subjecti vely assessed. RESULTS: All infusions provided-an equilibrium plateau of constant prolonged enhancement starting after 2 minutes and lasting until the end of the infusion. Enhancement at the plateau was +13 dB (slow rate), +17.1 dB (standard rate), and +18.3 dB (fast rate) compar ed with baseline. Saturation artifacts with infusions were markedly fe wer than those with bolus injections. Dose effectiveness (duration of enhancement that measured at least 7.5 dB per gram of contrast agent) was markedly improved with the infusions, from 0.8 min/g for the bolus to 2.6 min/g for the slow infusion. CONCLUSION: Continuous infusion o f the microbubble contrast agent provided prolonged and uniform enhanc ement of Doppler signals and improved image quality by minimizing satu ration artifacts.