Applications of acoustic droplet vaporization in diagnostic and therapeutic ultrasound.

Abstract

Micron- and nano-sized colloids are being studied in diagnostic and therapeutic applications of ultrasound (US). Unlike clinically utilized microbubbles, emulsions possess unique physiochemical properties that could translate into distinct, clinical benefits beyond conventional contrast agents. Droplets, composed of a superheated liquid, can be phase transitioned into bubbles using US, a process known as acoustic droplet vaporization (ADV). Droplets, transpulmonary in size, transition into bubbles upon ADV and can reach diameters that occlude capillaries and arrest blood flow in the vascular bed. Examples of ADV in diagnostic and therapeutic applications will be presented. First, ADV has been used in phase aberration correction in transcranial US imaging. Second, ADV-generated microbubbles can reduce and occlude renal perfusion in vivo. Third, the effects of thermal therapy using high-intensity focused ultrasound (HIFU) has been enhanced and controlled more effectively using ADV. Fourth, ADV has been utilized as a release mechanism for therapeutic agents that are incorporated into the emulsion. In all applications, the physiochemical properties of the droplets coupled with the spatial and temporal control afforded by ADV-generated microbubbles are crucial to the success of each ADV development. [This work was supported in part by NIH Grant 5R01EB000281.]