Use of Microbubbles as Ultrasound Contrast Agents for Molecular Imaging

Abstract

The field of ultrasound contrast imaging has been literally bursting in the last decade. It becomes clear that ultrasonography which already plays a pivotal role in clinical diagnostics will become essential to health care management with the rise of ultrasound molecular imaging [6]. Technical breakthrough together with enhanced image processing greatly improved spatial resolution and dynamic range of ultrasound imaging. Ultrasound contrast agents (UCA) for medical imaging have been rapidly translated from exploratory research to clinical application [12]. The next generation of targeted contrast agents (TCA) is currently intensively investigated by numerous research groups. They will open a new era where diagnostics is not only based on pathophysiological signs but also on the molecular signature of a disease [2]. TCA are formulations generating signal enhancement, typically gas-filled microbubbles for ultrasound imaging, which are capable of specific binding to a site of interest. This is usually achieved by coupling a targeting ligand onto the surface of the microbubble. Three types of microbubbles are successively used for the different development stages of targeting projects: non-targeted naked microbubbles, streptavidin-bearing microbubbles and ligand-decorated microbubbles (Fig. 2.1).