Dependence of inertial cavitation induced by high intensity focused ultrasound on transducer F-number and nonlinear waveform distortion

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 act...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2018-09, Vol.144 (3), p.1160-1169
Main Authors: Khokhlova, Tatiana, Rosnitskiy, Pavel, Hunter, Christopher, Maxwell, Adam, Kreider, Wayne, ter Haar, Gail, Costa, Marcia, Sapozhnikov, Oleg, Khokhlova, Vera
Format: Article
Language:English
Subjects:
Biomedical Acoustics
Models, Biological
Oscillometry - instrumentation
Oscillometry - methods
Transducers
Ultrasonic Waves
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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.
ISSN:0001-4966
1520-8524
DOI:10.1121/1.5052260