In vivo evaluation of a new ultrasound contrast agent

An ultrasound contrast agent (EchoGen; Sonus Pharmaceuticals, Bothell, WA) was evaluated in vivo. The agent changes at body temperature from non-echogenic submicron liquid droplets to echogenic gas microbubbles (1-2 μm*) capable of traversing the pulmonary and capillary circulations. IV injections were given to 5 woodchucks, 4 dogs and 12 rabbits (dose: 0.05-0.8 ml/kg). Color Doppler, color amplitude and B-mode images were acquired from kidneys and vessels. A segmental branch of the renal artery was ligated providing a model of ischemia. Increased flow signal intensities were observed for 2-3 minutes. Normal vessels and the area of ischemia were visualized using both color modes. An in vivo dose response curve was calculated. The curve was nonlinear with 18.7 dB maximum enhancement. Parenchymal enhancement was observed, and uptake and washout curves generated. Enhancement lasted 20 minutes. Ischemia was also seen using B-mode. In conclusion, EchoGen produces vascular and parenchymal enhancement. Ischemia was seen with all imaging modes