Environmental influences on the new surfactant-stabilized bubbles, ST68, we
re investigated. We have developed a new surfactant-based contrast agent ST
68, which is prepared by insonating buffered mixtures of Span 60 and Tween
80 in the presence of either air, PFC, or SF, gas, The effect of dilution,
shear, and sonication on size distribution of ST68 showed that PFC-containi
ng bubbles (ST68-PFC) were most stable. ST68-PFC bubbles lasted more than 1
5 min with similar to 30 dB backscatter enhancement in degassed phosphate-b
uffered saline, (pH 7.4), and air bubbles lasted similar to 3 s, suggesting
the effects of diffusion. Additionally, it was found that the ionic streng
th of the suspending medium (for example, PBS), did not have any effect on
ST68 bubbles containing SF, or PFC, but had a dramatic impact on bubbles co
ntaining air. (C) 2000 World Federation for Ultrasound in Medicine & Biolog
y.