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Title: Numerical study of a confocal ultrasonic setup for creation of cavitation

Abstract

Acoustic cavitation is used for various therapeutic applications such as local enhancement of drug delivery, histotripsy or hyperthermia. One of the utmost important parameter for cavitation creation is the rarefaction pressure. The typical magnitude of the rarefaction pressure required to initiate cavitation from gas dissolved in tissue is beyond the range of the megapascal. Because nonlinear effects need to be taken into account, a numerical simulator based on the Westervelt equation was used to study the pressure waveform and the acoustic field generated by a setup for creation of cavitation consisting of two high intensity focused ultrasound transducers mounted confocally. At constant acoustic power, simulations with only one and both transducers from the confocal setup showed that the distortion of the pressure waveform due to the combined effects of nonlinearity and diffraction is less pronounced when both confocal transducers are used. Consequently, the confocal setup generates a greater peak negative pressure at focus which is more favorable for cavitation initiation. Comparison between the confocal setup and a single transducer with the same total emitting surface puts in evidence the role of the spatial separation of the two beams. Furthermore, it has been previously shown that the location of the peakmore » negative pressure created by a single transducer shifts from focus towards the transducers in the presence of nonlinear effects. The simulator was used to study a configuration where the acoustical axes of transducers intersect on the peak negative pressure instead of the geometrical focus. For a representative confocal setup, namely moderate nonlinear effects, a 2% increase of the peak negative pressure and 8% decrease of the peak positive pressure resulted from this configuration. These differences tend to increase by increasing nonlinear effects. Although the optimal position of the transducers varies with the nonlinear regimen, the intersection point remains the location of the peak negative pressure in any case. Thus, unlike the location of the peak negative pressure for a single transducer can shift by a few millimeters, the focal point of a confocal device is independent of the power. This point is particularly important for therapeutic applications, frequently requiring high spatial accuracy. An experiment conducted shows that cavitation creation can be achieved easier with confocal ultrasound.« less

Authors:
; ;  [1]; ;  [1]
  1. Inserm, U1032, LabTau, Lyon, F-69003 (France)
Publication Date:
OSTI Identifier:
22492628
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 1685; Journal Issue: 1; Conference: 20. international symposium on nonlinear acoustics, Ecully (France), 29 Jun - 3 Jul 2015, 2. international sonic boom forum, Ecully (France), 29 Jun - 3 Jul 2015; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 42 ENGINEERING; ANIMAL TISSUES; CAVITATION; COMPARATIVE EVALUATIONS; DIFFRACTION; HYPERTHERMIA; NONLINEAR PROBLEMS; NUMERICAL ANALYSIS; PEAKS; SIMULATION; SIMULATORS; TRANSDUCERS; ULTRASONIC WAVES; WAVE FORMS

Citation Formats

Lafond, Maxime, Chavrier, Françoise, Prieur, Fabrice, Université de Lyon, Lyon, F-69003, Université Lyon 1, Lyon, F-69003, Mestas, Jean-Louis, Lafon, Cyril, Université de Lyon, Lyon, F-69003, Université Lyon 1, Lyon, F-69003, and Caviskills SAS, Vaulx-En-Velin, F-69120. Numerical study of a confocal ultrasonic setup for creation of cavitation. United States: N. p., 2015. Web. doi:10.1063/1.4934399.
Lafond, Maxime, Chavrier, Françoise, Prieur, Fabrice, Université de Lyon, Lyon, F-69003, Université Lyon 1, Lyon, F-69003, Mestas, Jean-Louis, Lafon, Cyril, Université de Lyon, Lyon, F-69003, Université Lyon 1, Lyon, F-69003, & Caviskills SAS, Vaulx-En-Velin, F-69120. Numerical study of a confocal ultrasonic setup for creation of cavitation. United States. https://doi.org/10.1063/1.4934399
Lafond, Maxime, Chavrier, Françoise, Prieur, Fabrice, Université de Lyon, Lyon, F-69003, Université Lyon 1, Lyon, F-69003, Mestas, Jean-Louis, Lafon, Cyril, Université de Lyon, Lyon, F-69003, Université Lyon 1, Lyon, F-69003, and Caviskills SAS, Vaulx-En-Velin, F-69120. 2015. "Numerical study of a confocal ultrasonic setup for creation of cavitation". United States. https://doi.org/10.1063/1.4934399.
@article{osti_22492628,
title = {Numerical study of a confocal ultrasonic setup for creation of cavitation},
author = {Lafond, Maxime and Chavrier, Françoise and Prieur, Fabrice and Université de Lyon, Lyon, F-69003 and Université Lyon 1, Lyon, F-69003 and Mestas, Jean-Louis and Lafon, Cyril and Université de Lyon, Lyon, F-69003 and Université Lyon 1, Lyon, F-69003 and Caviskills SAS, Vaulx-En-Velin, F-69120},
abstractNote = {Acoustic cavitation is used for various therapeutic applications such as local enhancement of drug delivery, histotripsy or hyperthermia. One of the utmost important parameter for cavitation creation is the rarefaction pressure. The typical magnitude of the rarefaction pressure required to initiate cavitation from gas dissolved in tissue is beyond the range of the megapascal. Because nonlinear effects need to be taken into account, a numerical simulator based on the Westervelt equation was used to study the pressure waveform and the acoustic field generated by a setup for creation of cavitation consisting of two high intensity focused ultrasound transducers mounted confocally. At constant acoustic power, simulations with only one and both transducers from the confocal setup showed that the distortion of the pressure waveform due to the combined effects of nonlinearity and diffraction is less pronounced when both confocal transducers are used. Consequently, the confocal setup generates a greater peak negative pressure at focus which is more favorable for cavitation initiation. Comparison between the confocal setup and a single transducer with the same total emitting surface puts in evidence the role of the spatial separation of the two beams. Furthermore, it has been previously shown that the location of the peak negative pressure created by a single transducer shifts from focus towards the transducers in the presence of nonlinear effects. The simulator was used to study a configuration where the acoustical axes of transducers intersect on the peak negative pressure instead of the geometrical focus. For a representative confocal setup, namely moderate nonlinear effects, a 2% increase of the peak negative pressure and 8% decrease of the peak positive pressure resulted from this configuration. These differences tend to increase by increasing nonlinear effects. Although the optimal position of the transducers varies with the nonlinear regimen, the intersection point remains the location of the peak negative pressure in any case. Thus, unlike the location of the peak negative pressure for a single transducer can shift by a few millimeters, the focal point of a confocal device is independent of the power. This point is particularly important for therapeutic applications, frequently requiring high spatial accuracy. An experiment conducted shows that cavitation creation can be achieved easier with confocal ultrasound.},
doi = {10.1063/1.4934399},
url = {https://www.osti.gov/biblio/22492628}, journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 1685,
place = {United States},
year = {Wed Oct 28 00:00:00 EDT 2015},
month = {Wed Oct 28 00:00:00 EDT 2015}
}