The preparation and application of microbubble contrast agent combining ultrasound imaging and magnetic resonance imaging

Encapsulated gas microbubbles are well known as ultrasound contrast agents (UCAs) for medical ultrasound (US) imaging. With the development of shell materials and preparation technologies, the application of microbubbles has been enormously popular in molecular imaging, drug delivery and targeted therapy, etc. The objective of this study is to develop Fe3O4 nanoparticle-inclusion microbubble construct. The in vitro US imaging experiment indicates that the Fe3O4 nanoparticle-inclusion microbubbles have higher US enhancement than those without Fe3O4 nanoparticle-inclusion. According to the microbubble dynamic theory, the acoustic scattering properties can be quantified by scattering cross-section of the shell. The scattering study on Fe3O4 nanoparticle-inclusion microbubbles of different concentration shows that within a certain range of concentration, the scattering cross-section of microbubble increases with the addition of Fe3O4 nanoparticles. When exceeding the concentration range, the ultrasonic characteristic of microbubbles is damped. On the other hand, since Fe3O4 nanoparticles can also serve as the Magnetic Resonance Imaging (MRI) contrast agent, they can be potentially used as contrast agents for the double-modality (MRI and US) clinical studies. However, it is important to control the concentration of Fe3O4 nanoparticles in the shell in order to realize the combined functions of US and MRI.