Abstract
In the following study, gas filled microbubbles encapsulated in a polymer shell were characterised for use as contrast agents, as compared to commercially available contrast agents such as Definity microbubbles. The lifetime of these nested microparticles was also explored. It was found that even with changing the contrast agent due to the enclosure in a polymer shell, the acoustic response using Definity microbubbles and nested microparticles can be matched by simply varying the starting concentrations, and there is no change in their behaviour as a contrast agent. The results also indicate the ability of the nested microparticles to provide contrast steadily for up to 1·5 h.