Development of a novel method for synthesis of a polymeric ultrasound contrast agent

Medical ultrasound is a highly valuable diagnostic tool, especially when compared with other imaging modalities. It is a noninvasive, real-time, portable, extremely safe method compared with X-ray and inexpensive relative to magnetic resonance imaging. However, ultrasound is limited in its ability to distinguish between diseased and normal tissue. This limitation has led to the development of contrast agents. We have produced novel poly (lactic-co-glycolic) acid air-filled microcapsules that work well as ultrasound contrast agents, giving up to 24 and 25 dB enhancement when insonated in the medical imaging range at 5 and 7.5 MHz, respectively. The capsules were fabricated by modifying a double emulsion method to encapsulate camphor in the oil phase and ammonium carbonate in the aqueous phase, and later sublime the encapsulated material, leaving voids capable of being filled with a gas in their place. The role of the surfactant, poly vinyl alcohol, solution temperature, was studied and found to play an important role in the morphology of the capsules, altering their acoustic response. (C) 2003 Wiley Periodicals, Inc.