Laser-nucleated acoustic cavitation in focused ultrasound

Abstract

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 0.5×10(6) 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.

Ultrasound Activated Nano-Encapsulated Targeted Drug Delivery and Tumour Cell Poration

“…To investigate the cavitation phenomenon in more details than a clinical MRgFUS system allows, we have developed an experimental set-up (Gerold et al 2011 ) , which makes possible observation of the fi rst stages of the cavitation cloud formation in the high-speed regime. We have observed laser-nucleated acoustic cavitation with high speed cameras, at frame rates between 0.5 and 3 million frames per second.…”

Validity of the Keller-Miksis equation for “non-stable” cavitation and the acoustic emissions generated

“…The laser pulse, triggered to be incident ∼ 5 cycles into a 65-cycle burst of HIFU, generated the cavitation activity reported below in free-field driving conditions [7].…”

Validity of the Keller-Miksis equation for “non-stable” cavitation and the acoustic emissions generated

“…1 (a). We employ the laser-nucleation technique [7], to precisely initiate cavitation activity relative to the NH tip, and in the HIFU focus. HIFU is generated via a single element piezoceramic transducer (H-149, Sonic Concepts, USA), connected to a power amplifier (2100L, Electronic and Innovation, USA) and a waveform generator (DG4102, Rigol Technologies, China).…”