Dependence of inertial cavitation induced by high intensity focused ultrasound on transducer F-number and nonlinear waveform distortion.
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Date
2018-09-01ICR Author
Author
Khokhlova, T
Rosnitskiy, P
Hunter, C
Maxwell, A
Kreider, W
Ter Haar, G
Costa, M
Sapozhnikov, O
Khokhlova, V
Type
Journal Article
Metadata
Show full item recordAbstract
Pulsed high intensity focused ultrasound was shown to enhance chemotherapeutic drug uptake in tumor tissue through inertial cavitation, which is commonly assumed to require peak rarefactional pressures to exceed a certain threshold. However, recent studies have indicated that inertial cavitation activity also correlates with the presence of shocks at the focus. The shock front amplitude and corresponding peak negative pressure (p -) in the focal waveform are primarily determined by the transducer F-number: less focused transducers produce shocks at lower p -. Here, the dependence of inertial cavitation activity on the transducer F-number was investigated in agarose gel by monitoring broadband noise emissions with a coaxial passive cavitation detector (PCD) during pulsed exposures (pulse duration 1 ms, pulse repetition frequency 1 Hz) with p- varying within 1-15 MPa. Three 1.5 MHz transducers with the same aperture, but different focal distances (F-numbers 0.77, 1.02, 1.52) were used. PCD signals were processed to extract cavitation probability, persistence, and mean noise level. At the same p -, all metrics indicated enhanced cavitation activity at higher F-numbers; specifically, cavitation probability reached 100% when shocks formed at the focus. These results provide further evidence supporting the excitation of inertial cavitation at reduced p - by waveforms with nonlinear distortion and shocks.
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Subject
Oscillometry
Transducers
Models, Biological
Ultrasonic Waves
Research team
Therapeutic Ultrasound
Language
eng
License start date
2018-09
Citation
The Journal of the Acoustical Society of America, 2018, 144 (3), pp. 1160 - ?
Publisher
ACOUSTICAL SOC AMER AMER INST PHYSICS