Dependence of inertial cavitation induced by high intensity focused ultrasound on transducer F-number and nonlinear waveform distortion.
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ICR Authors
Authors
Khokhlova, T
Rosnitskiy, P
Hunter, C
Maxwell, A
Kreider, W
Ter Haar, G
Costa, M
Sapozhnikov, O
Khokhlova, V
Rosnitskiy, P
Hunter, C
Maxwell, A
Kreider, W
Ter Haar, G
Costa, M
Sapozhnikov, O
Khokhlova, V
Document Type
Journal Article
Date
2018-09-01
Date Accepted
Date Available
Abstract
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.
Citation
The Journal of the Acoustical Society of America, 2018, 144 (3), pp. 1160 - ?
Source Title
Publisher
ACOUSTICAL SOC AMER AMER INST PHYSICS
ISSN
0001-4966
eISSN
1520-8524
Collections
Research Team
Therapeutic Ultrasound