Ultrasound molecular imaging by targeted microbubble contrast agents

Ultrasound contrast agents are based on the physical resonating behavior of bubbles with diameter of few microns, microbubbles, when those undergone ultrasound beam. Microbubbles, once introduced in the body intravenously, increase the backscatter from blood improving contrast image such that the macro and micro-circulation can be both visualized in order to asses organ function and to characterize tumors vascolarity. Recently, phenomena associated to resonating microbubbles such as "cavitation", "microstreaming" and "sonoporation" have suggested that ultrasound contrast agent may be induced, deliberately by the ultrasonographer, to interact with the endothelial cells and that the interaction may further be driven if microbubbles are specifically targeted for intravascular molecules: either by modifying the shell of microbubbles or by attaching on the shell specific ligands: i.e. peptides, proteins and antibody. This features have opened new scenarios since microbubbles can be seen, not only, as media to improve generically contrast vascular image, but also as media to record physiological process undergoing into the vascular constrain as well as to release a healing payload, carried by microbubbles, to the surrounding tissues. Therefore, ultrasound contrast media may further place ultrasonography among therapeutic modality as much as advances in ligands and bubbles biochemistry as well as advances in US probes technology will be provided. A concise overview of the current understandings on ultrasound contras media is hereafter presented.