Acceleration of ultrasound thermal therapy by patterned acoustic droplet vaporization

Abstract

One application of acoustic droplet vaporization (ADV), a method of converting biocompatible microdroplets into microbubbles, is to enhance locally high intensity focused ultrasound (HIFU) therapy. Two objectives are pursued here: (1) the controlled creation of a bubble trench prior to HIFU using ADV and (2) use of the trench for increasing ablation volumes, lowering acoustic powers, and decreasing therapy duration. Thermally responsive phantoms were made with perfluorocarbon emulsion. Compound lesions were formed in a laboratory setting and a clinical magnetic resonance imaging (MRI)-guided HIFU system. Linear and spiral patterned compound lesions were generated in trenches. A larger fraction of the HIFU beam is contained to increase the generation of heat. Using the laboratory system, a 90 mm linear length spiral trench was formed in 30 s with mechanical beam steering. Comparatively, the clinical HIFU system formed a 19.9 mm linear length spiral trench in approximately 1 s with electronic beam steering. Lesions were imaged optically and with MRI. A uniform thermal ablation volume of 3.25 mL was achieved in 55.4 s (4-times faster than standard clinical HIFU and 14-times larger volume versus sum of individual lesions). Single lesions showed a 400% volume increase.

<div>Low-intensity focused ultrasound (LIFU)-induced acoustic droplet vaporization in phase-transition perfluoropentane nanodroplets modified by folate for ultrasound molecular imaging</div>

“…31 US generated many advantageous effects, including cavitation effect, mechanical effect, and heating effect, which efficiently promoted the phase-transition process of nanodroplets. 32 HIFU has been reported to induce ADV in PFC nanodroplets in many studies, 16,29,33 which can synergistically enhance the therapeutic efficiency of HIFU ablation on tumor. Clinically used US imaging system has also been induced to activate droplet vaporization by increasing MI, but it could not accurately control the ADV area and it may be induced in the whole sonication scope.…”

Materials Chemistry of Nanoultrasonic Biomedicine

“…The generation of PFH MBs after NIR irradiation significantly enhanced the positive contrast of US imaging in PFH@PLGA/Fe 3 O 4 group (Figure a 2 ‐a 17 ). Comparatively, ADV is regarded as the mostly explored approach to realize MBs generation from nanosized droplets . We recently achieved the ADV process based on the thermal effect of HIFU .…”

Micron-sized PFOB liquid core droplets stabilized with tailored-made perfluorinated surfactants as a new class of endovascular sono-sensitizers for focused ultrasound thermotherapy

“…[33][34][35] The second are micron-sized droplets (MSD) which are restrained to the vasculature (endo-vascular). They can be used for enhancing thermal ablation in highly perfused tumours 15,36 and as well for embolotherapy as they generate micro-bubbles able to occlude small capillary vessels. 23,37 In order to reduce the potential side effects ascribed to HIFU therapy when adapting it to highly perfused tumours, we report the use of perfluorooctylbromide (PFOB)-filled MSD to reduce the ultrasound exposure time and energy required for tumour ablation.…”