Comparison of air and perfluorocarbon filled microbubbles for ultrasound contrast studies

Abstract

To evaluate the impact of different gasses on contrast studies a new contrast agent ST68 (US patent 5,352,436) was produced with either air (ST68-Air) or perfluorocarbon (ST68-PFC) filled microbubbles. ST68 was administrated to 11 rabbits. In 4 animals a qualitative comparison of duration and degree of enhancement was performed. ST68-PFC produced greater vascular enhancement than did ST68-PFC. Also, the former achieved gray scale enhancement - unlike the latter. Enhancement with ST68-PFC lasted over 8 minutes, while ST68-Air lasted less than 2 minutes. Quantitative dose-responses (averaged over 5 injections) were calculated, via spectral power analysis, using data from 7 rabbits and a 10 MHz cuff-transducer placed around the distal aorta. Maximum enhancement with ST68-Air was 18.3 dB for a 0.13 ml/kg dose, while ST68-PFC produced 26.1 dB of enhancement for a 0.1 ml/kg dose. In conclusion, perfluorocarbon filled microbubbles appear to be superior to air filled ones for use in an ultrasound contrast agent.