Effects of lamb wave in therapeutic ultrasound transducer by vibration analysis

Kenji Otsu, Yasuhiro Kaneshima, Shin Yoshizawa, Shin Ichiro Umemura

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

A typical single-element High Intensity Focused Ultrasound (HIFU) transducer has a spherical shell in order to focus the acoustic energy onto the focal spot. In a prototype PZT transducer we constructed, a mode of plate wave propagation in the shell was experimentally observed in addition to the uniform thickness vibration mode. Such an unwanted wave component may deform the ultrasonic power deposition pattern, which can potentially influence the therapeutic effects. In this study, we analyzed the vibrating behavior of a spherical piezoelectric transducer in two ways: by the reconstruction of the sound source distribution from a measured pressure field and by a numerical simulation of vibration based on a Finite Element Method (FEM). In the two-dimensional Fourier analysis performed in both time and space domain, the radial wavenumber spectrum showed a high peak, second to the highest peak corresponding to the uniform vibration. This corresponds to the waves propagating from the circumference towards the center of the spherical transducer like a symmetric mode of leaky Lamb waves. The leaked waves propagate at a constant angle with the shell surface in water and form a relatively large lobe on the axis at the nearside of the geometric focus. This nearside lobe, also observed in the measurement, may cause additional near field heating of tissues.

Original languageEnglish
Title of host publication6th World Congress of Biomechanics, WCB 2010 - In Conjunction with 14th International Conference on Biomedical Engineering, ICBME and 5th Asia Pacific Conference on Biomechanics, APBiomech
Pages1640-1643
Number of pages4
DOIs
Publication statusPublished - 2010 Oct 22
Event6th World Congress of Biomechanics, WCB 2010 - In Conjunction with 14th International Conference on Biomedical Engineering, ICBME and 5th Asia Pacific Conference on Biomechanics, APBiomech - Singapore, Singapore
Duration: 2010 Aug 12010 Aug 6

Publication series

NameIFMBE Proceedings
Volume31 IFMBE
ISSN (Print)1680-0737

Other

Other6th World Congress of Biomechanics, WCB 2010 - In Conjunction with 14th International Conference on Biomedical Engineering, ICBME and 5th Asia Pacific Conference on Biomechanics, APBiomech
CountrySingapore
CitySingapore
Period10/8/110/8/6

Keywords

  • High Intensity Focused Ultrasound
  • Lamb wave
  • PZT
  • acoustic field
  • transducer

ASJC Scopus subject areas

  • Bioengineering
  • Biomedical Engineering

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