Ultrasound imaging of perfluoropentane nanodroplets after microwave-exposure

Nanodroplets (NDs) are smart agents used across a wide range of industrial and biomedical applications. Targeted activation of NDs, whereby the liquid core of NDs is vaporized to form gaseous microbubbles (MBs), can be achieved by directing external energy toward NDs, such as thermal, ultrasound and electromagnetic energy. In this study, a microwave-based ND activation by an ultrawide-band microwave antenna is proposed. The experiments were designed to investigate and visualize the effect of microwave (MW) exposure on lipid-shell perfluoropentane (PFP) using high frame rate ultrasound imaging. Ultrasound imaging of a dual-channel agar phantom containing degassed phosphate-buffered saline (PBS) as a control and MW-exposed NDs shows increased backscatter intensity in MW-exposed NDs compared to degassed PBS with an intensity increase of approximately 8.4±2.4 dB. These results suggest that MW exposure may trigger vaporization of PFP NDs.