EXPERIMENTAL-STUDY OF STABILITY OF A CONTRAST AGENT IN AN ULTRASOUND FIELD

Attenuation coefficient and phase velocity measurements and direct opt ical observations showed that microbubbles of a contrast agent (Albune x (R)) in 5% bovine albumin solution were not stable under ultrasonic irradiation. When the concentration of Albunex (R) was 0.41 mu L/mL an d a 2.5-MHz phased array transducer of a Hewlett-Packard ultrasound im aging system (Model 77020AC) was used as the ultrasound source (the co mpression and rarefaction peak pressure amplitudes were, respectively, equal to 2 MPa and 1 MPa, the repetition frequency was 2.64 kHz), the attenuation coefficient at 2.5 MHz dropped from 40 dB/cm to 16 dB/cm after 2 min of continuous insonification. Under a static condition, it was shown by direct optical observations that the microbubbles shrank and aggregated to form clusters or were destroyed under insonificatio n; pressure amplitude was estimated to be 0.5 MPa, frequency = 2.44 MH z, and the pulse repetition frequency was 5 kHz. (C) 1998 World Federa tion for Ultrasound in Medicine & Biology.