Spatiotemporal evolution of cavitation dynamics exhibited by flowing microbubbles during ultrasound exposure.

Journal article

Ultrasound and microbubble-based therapies utilize cavitation to generate bioeffects, yet cavitation dynamics during individual pulses and across consecutive pulses remain poorly understood under physiologically relevant flow conditions. SonoVue(®) microbubbles were made to flow (fluid velocity: 10-40 mm/s) through a vessel in a tissue-mimicking material and were exposed to ultrasound [frequency: 0.5 MHz, peak-rarefactional pressure (PRP): 150-1200 kPa, pulse length: 1-100,000 cycles, pulse repetition frequency (PRF): 1-50 Hz, number of pulses: 10-250]. Radiated emissions were captured on a linear array, and passive acoustic mapping was used to spatiotemporally resolve cavitation events. At low PRPs, stable cavitation was maintained throughout several pulses, thus generating a steady rise in energy with low upstream spatial bias within the focal volume. At high PRPs, inertial cavitation was concentrated in the first 6.3 ± 1.3 ms of a pulse, followed by an energy reduction and high upstream bias. Multiple pulses at PRFs below a flow-dependent critical rate (PRF(crit)) produced predictable and consistent cavitation dynamics. Above the PRF(crit), energy generated was unpredictable and spatially biased. In conclusion, key parameters in microbubble-seeded flow conditions were matched with specific types, magnitudes, distributions, and durations of cavitation; this may help in understanding empirically observed in vivo phenomena and guide future pulse sequence designs.

Authors: Choi, J; Coussios, C

• Publication status: Published
• Journal: Journal of the Acoustical Society of America
• Volume: 132
• Issue: 5
• Pages: 3538-3549
• Publication date: 2012-11-01
• DOI: 10.1121/1.4756926
• EISSN: 1520-8524
• ISSN: 0001-4966
• Language: English
• Keywords: Pressure; Contrast Media; Phospholipids; Sulfur Hexafluoride; Microbubbles; Transducers, Pressure; Equipment Design; Models, Theoretical; Ultrasonics; Time Factors