- Oral presentation
- Open Access
Direct nanodroplet and microbubble comparison for high intensity focused ultrasound ablation enhancement and safety
© Moyer et al; licensee BioMed Central Ltd. 2015
Published: 30 June 2015
High intensity focused ultrasound (HIFU) surgery often requires hours of ablation in order to treat an entire tumor. Both perfluorocarbon gaseous microbubbles and vaporized liquid droplets are known enhancers of HIFU thermal ablation. Microbubbles, however, often lead to surface or skin lesions. Furthermore, they have a relatively short half-life in vivo (minutes) rendering them insufficiently stable for an entire HIFU surgery, which can last several hours. Many droplet formulations require very high pressures to activate. Our aim was to design an agent that could shorten ablation procedures without sacrificing safety. We designed and investigated a perfluorocarbon nanodroplet composed of a 1:1 ratio of dodecafluoropentane and decafluorobutane. These are tuned to change phase and activate at only 2 MPa peak negative pressure with common HIFU pulse lengths, enabling focused and targeted activation. Additionally, they are stable at body temperature.
Two lipid-shelled agents, microbubbles (2.1 +/-0.5 micron diameter) and nanodroplets (240 +/-65 nm diameter), were manufactured in-house. Effective circulation time of the nanodroplets was investigated in vivo. HIFU-induced temperature rises were measured as a function of the time after the injection of the agent occurred and were compared to controls wherein no agent was injected. HIFU (1 MHz, 4.06 MPa, CW, 15 seconds) was applied in vivo to rat livers 5, 15 or 95 minutes after agent injection, and any thermal enhancement was detected simultaneously by MR thermometry.
Results and conclusions
Funding was provided by the Focused Ultrasound Foundation, the NIH-NIGMS SPIRE Fellowship to LCP and NSF DMR #1122483. The authors would like to thank Jeremy Gatesman and Gina Wimer for veterinary assistance.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.