Comparison of different perfluorocarbons as ultrasound contrast agents

RATIONALE AND OBJECTIVES. The sonographic properties of Fluosol 20% (F20), which was recently approved for clinical use as an oxygen carrier for coronary angioplasty, were compared to those of perflubron emulsion, which is still in clinical testing. METHODS. Contrast agents were evaluated in 21 normal rabbits divided into three groups of seven rabbits each. All rabbits received 2.7 g/kg of perfluorocarbon (PFC). One group received 2.7 ml/kg of an experimental formulation of perflubron emulsion AF0102, which contains 1 g of PFC in 1 ml of emulsion (P100), the other received 13.5ml/kg of F20 (1 ml has 0.2g of PFC), and the third received 13.5ml/kg of P100 diluted to a 20% concentration (P20). All rabbits were scanned by a blinded sonographer before, during, and immediately after infusion, and then again at 30 minutes and 48 hours. Doppler enhancement, echogenicity of inferior vena cava lumen, echogenic enhancement of perfused tissues, and reticuloendothelial organs were assessed. RESULTS. P100 and P20 had nearly identical sonographic properties at all points. During their vascular phase they enhanced Doppler signal, filled the lumen of the IVC and hepatic veins with flowing echogenic reflectors, and enhanced perfused tissues. F20 had no detectable sonographic effect during its vascular phase. All three emulsions enhanced the liver relative to kidney to a similar degree at 48 hours. CONCLUSIONS. Because RE enhancement was similar for F20, P100, and P20, and because P100 and P20 had similar properties during the vascular phase, the lack of vascular effect of F20 could not be due to the different PFCs used in these agents, or due to the difference in the dilution or volume. The most likely cause for the observed sonographic behavior of F20 and P100 is the difference in emulsion formulation.