Multiple-frequency phased array patterns for therapeutic ultrasound

John R. Ballard, Dalong Liu, Andrew J. Casper, Yayun Wan, Mohamed Almekkawy, Emad S Ebbini

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

Abstract

Modern transducer technology allows for the design and implementation of therapeutic arrays with relatively wide bandwidths (>50%) and low cross coupling between elements. We present results from a 3.5 MHz, 64-element prototype designed for small-animal and superficial therapeutic HIFU applications (Imasonic, Inc.) This transducer has a 58% 6-dB fractional BW average on its elements allowing for therapeutic output in the frequency range of 2.7 - 4.6 MHz. We present a simulation/experimental study to evaluate and optimize the focusing capabilities of the phased array prototype when excited by multiple-frequency components. Preliminary results have shown that multiple-frequency excitation may be beneficial in enhancing the therapeutic effects of HIFU beams. A multiple-focus pattern synthesis algorithm for arrays excited by multiple-frequency signals has been developed and tested using linear pressure field simulations. The algorithm maintains the precise phase relationship between the frequency components at each focal spot to achieve a desirable outcome. Hydrophone measurements to validate the approach show that nonlinear effects at the focal location are more prominent with the frequency mixing compared to conventional single frequency excitation. An in vitro study of lesion formation in freshly excised porcine liver was investigated.

Original languageEnglish (US)
Title of host publication11th International Symposium on Therapeutic Ultrasound
Pages9-13
Number of pages5
DOIs
StatePublished - Dec 1 2012
Event11th International Symposium on Therapeutic Ultrasound, ISTU 2011 - New York, NY, United States
Duration: Apr 11 2011Apr 13 2011

Publication series

NameAIP Conference Proceedings
Volume1481
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

Other11th International Symposium on Therapeutic Ultrasound, ISTU 2011
CountryUnited States
CityNew York, NY
Period4/11/114/13/11

Keywords

  • Cavitation
  • Multiple-focus Synthesis
  • Phased Arrays
  • Thermal Therapy

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  • Cite this

    Ballard, J. R., Liu, D., Casper, A. J., Wan, Y., Almekkawy, M., & Ebbini, E. S. (2012). Multiple-frequency phased array patterns for therapeutic ultrasound. In 11th International Symposium on Therapeutic Ultrasound (pp. 9-13). (AIP Conference Proceedings; Vol. 1481). https://doi.org/10.1063/1.4757302