Effects of vaporized phase-shift nanoemulsion on high-intensity focused ultrasound-mediated heating and lesion formation in gel phantom.

Abstract

In this study, we demonstrate the feasibility of using a phase-shift nanoemulsion (PSNE) as nuclei for bubble-enhanced heating and lesion formation during high-intensity focused ultrasound (HIFU) thermal ablation. In our experiments, different concentrations of PSNE (5%–15%) uniformly distributed throughout gel phantoms made from acrylamide and albumin were sonicated with a 1.1 MHz HIFU transducer. The PNSE at the transducer focus were first vaporized into bubbles and then acoustically driven with continuous wave HIFU at different amplitudes. Bubble-enhanced heating resulted in albumin denaturation and lesion formation. HIFU-mediated heating was conducted with and without vaporized PSNE, and the lesion size and location relative to the transducer focus were measured after HIFU exposure. In the presence of vaporized PSNE, lesions were formed more rapidly and reached a larger volume compared with no vaporized PSNE. We also noted that lesions formed due to bubble-enhanced heating were more often prefocal due to backscattering from the bubble cloud. Our results show that these effects were more pronounced at higher PSNE concentrations. Finally, a comparison between the effects of pulsed and cw exposure on cavitation activity and lesion shape was investigated.