Acoustic cavitation can occur in therapeutic applications of high-amplitude focused ultrasound. Studying acoustic cavitation has been challenging, because the onset of nucleation is unpredictable. We hypothesized that acoustic cavitation can be forced to occur at a specific location using a laser to nucleate a microcavity in a pre-established ultrasound field. In this paper we describe a scientific instrument that is dedicated to this outcome, combining a focused ultrasound transducer with a pulsed laser. We present high-speed photographic observations of laser-induced cavitation and laser-nucleated acoustic cavitation, at frame rates of 0.5106 frames per second, from laser pulses of energy above and below the optical breakdown threshold, respectively. Acoustic recordings demonstrated inertial cavitation can be controllably introduced to the ultrasound focus. This technique will contribute to the understanding of cavitation evolution in focused ultrasound including for potential therapeutic applications.
Bibliographical noteFunding Information:
This work has been supported by European Union (EU) FP7 [Grant No. 230674 (Nanoporation)], Deutsche Forschungsgemeinschaft (DFG) Emmy Noether Programme (Grant No. 38355133), and Engineering and Physical Sciences Research Council (United Kingdom) [EPSRC(GB)] (Grant Nos. EP/G01213X/1 and EP/F037025/1). Bjoern Gerold has been supported by an EPSRC DTA award. David McGloin is supported by the Royal Society. We are very grateful to EPSRC loan pool, notably to Adrian Walker, for ongoing access to high-speed imaging devices; to Javier Grinfeld, Yoav Medan, Oleg Prus, and Alex Volovick, all from InSightec Ltd, Tirat Carmel, Israel, for ongoing technical support; and Joyce Joy for ultrasound calibration measurements.