QUANTITATIVE ACOUSTIC CHARACTERIZATION OF A NEW SURFACTANT-BASED ULTRASOUND CONTRAST AGENT

The acoustic properties of a new ultrasound contrast agent, ST68, have been investigated, ST68 is a sonicated mixture of nonionic surfactant s (Span-type and Tween-type) consisting of stabilized microbubbles wit h a mean diameter of 3.8 mu m and a concentration of 7.1 x 10(8) bubbl es/mL. A pulsatile Bow system was used to acquire data in vitro. The a coustic properties of ST68, as a function of time, frequency and dose, were calculated, Enhancement changed nonlinearly with contrast agent dose; maximum was 13.1 dB +/- 1.0 dB for a dose of 0.30 mu L/mL of sus pending medium, Attenuation reached approximately 11 dB/cm for dosages above 0.27 mu L/mL and for frequencies between 2.5 and 6.0 MHz. In vi vo, IV injections of ST68 were given to 4 rabbits (doses from 0.01 to 0.23 mL/kg). A clear increase in Bow signal intensity was observed for 1 to 2 min, An in vivo dose-response curve was calculated from audio Doppler signals obtained with a 10-MHz cuff transducer placed around t he distal aorta, Maximum enhancement was 18.3 dB +/- 3.13 dB for a 0.1 3 mL/kg dose, Moreover, ST68 appears to follow a simple relationship b etween in vivo enhancement and dose, In conclusion, ST68 is capable of producing marked vascular enhancement, Its acoustic properties have b een characterized ill vitro and in vivo. (C) 1997 World Federation for Ultrasound in Medicine & Biology.