Ultrasound contrast agents are based on the physical resonating behavior of bubbles with a diameter of few microns, i.e. microbubbles, when they undergo ultrasound beams. Microbubbles, once introduced in the body intravenously, increase the blood backscatter improving contrast in images, so that both the macro- and microcirculation can be visuallized in order to asses organ function and to characterize tumors vascolarity. Recently, the analysis of phenomena associated with resonating microbubbles such as "cavitation", "microstreaming" and "sonoporation", has suggested that ultrasound contrast agents may be induced, intentionally 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. These features have opened new scenarios, since microbubbles can be seen, not only, as media to improve generically contrast vascular image, but also 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 (US) among the therapeutic modalities as much as advances in ligands and bubbles biochemistry as soon as advances in US probes technology will be provided. A concise overview of the current understandings on ultrasound contrast media is hereafter presented.
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