In vitro and in vivo characterization of a new surfactant stabilized ultrasound contrast media

Quantitative characterization of a new ultrasound contrast media ST68 has been performed, ST68 is a sonicated mixture of nonionic surfactants (Span-type and Tween-type), consisting of stabilized microbubbles with a mean diameter of 3.8 μm and a concentration of 7.1×10⁸ bubbles/mL. In vitro a pulsatile flow system was used to acquire digitized RF A-lines. The acoustic properties of ST68, as a function of time, frequency and dose, were calculated. Backscatter changed nonlinearly with dose; maximum was 12.5 dB±1.0 dB for a 0.4 mL dose. Attenuation reached approximately 22.5 dB/cm for dosages above 0.4 mL. In vivo intravenous injections were given to three rabbits (dosage: 0.01-0.23 mL/kg). A clear increase in flow signal intensity was observed for 1-2 minutes. An in vivo dose response curve was calculated from the audio signals of a 10 MHz cuff transducer placed around the distal aorta. Maximum enhancement was 18.3 dB±3.13 dB for a 0.13 mL/kg dose. In conclusion, ST68 is capable of producing marked vascular enhancement. Its acoustic properties have been characterized in vitro and in vivo