An in vitro study of phase shift nano-emulsion in focused ultrasound surgery: Its potential for enhancing ultrasound-mediated hyperthermia

Focused ultrasound surgery (FUS) is a noninvasive medical treatment for solid tumors by using ultrasound-mediated hyperthermia. The objectives of this study are to develop and characterize a submicron agent to yield higher thermal doses and eventual lead to a more efficient FUS protocol. The submicron agent, named as phase shift nano-emulsion (PSNE) in our study, consists of dodecafluoropentane liquid core enclosed with albumin shell. The liquid droplets have a diameter around 200 nm. In our study, we presented that PSNE could be vaporized using microsecond acoustic pulses in tissue-mimicking gel phantoms with a high degree of spatial and temporal control. During FUS, the resulting bubbles were driven by ultrasound and effectively increased the heat deposition. A needle thermocouple was used to measure this enhancement and a significant temperature rise was recorded after triggering the vaporization. The results from our in vitro study show a promising potential of PSNE for enhancing ultrasound-mediated hyperthermia during FUS treatment.