The application of phase‐shift nanoemulsion in high‐intensity focused ultrasound‐mediated heating and its potential in monitoring lesion formation.

Abstract

Phase‐shift nanoemulsion (PSNE) consists of dodecafluoropentane nanodroplets stabilized with phospholipid monolayer shell. These nanodroplets are pressure sensitive and can be vaporized into gas bubbles by a short ultrasound pulse (t<50 ms), provided the pressure exceeds a well‐defined threshold. This property provides means of on‐site and on‐demand nucleation by applying PSNE into high‐intensity focused ultrasound. In this study, the bubble‐enhanced lesion formation with the presence of PNSE in albumin‐containing gel phantom was investigated. The results demonstrated that the onset of bubble‐related heating could be well controlled by choosing the vaporization time and the bubble location was confined at the HIFU focal region. By acoustically driving the vaporized bubbles, localized bubble‐enhanced heating and a significant reduction of 71.9% in acoustic power were achieved. Furthermore, the vaporized bubbles can be monitored with B‐mode ultrasound due to the huge difference between gas and tissue. By comparing the optical image of lesion and ultrasound image of bubble cloud, a good correlation in location and shape between lesion and bubble cloud was observed. The correlation suggests that the bubble‐enhanced heating is localized at the region of bubble cloud. By monitoring cavitation activity, the spatial information of lesion formation could be provided during HIFU treatment.