Design of HIFU Transducers to Generate Specific Nonlinear Ultrasound Fields

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From: Physics Procedia(Vol. 87)
Publisher: Elsevier B.V.
Document Type: Author abstract; Report
Length: 332 words

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Abstract :

To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1016/j.phpro.2016.12.020 Byline: Vera A. Khokhlova [vera@acs366.phys.msu.ru] (a,b,*), Petr V. Yuldashev (b), Pavel B. Rosnitskiy (b), Adam D. Maxwell (a), Wayne Kreider (a), Michael R. Bailey (a), Oleg A. Sapozhnikov (a,b) Keywords HIFU; nonlinear waves; shocks; transducer design; boiling histotripsy Abstract Various clinical applications of high intensity focused ultrasound (HIFU) have different requirements on the pressure level and degree of nonlinear waveform distortion at the focus. Applications that utilize nonlinear waves with developed shocks are of growing interest, for example, for mechanical disintegration as well as for accelerated thermal ablation oftissue. In this work, an inverse problem of determining transducer parameters to enable formation of shockswith desired amplitude at the focus is solved. The solution was obtained by performing multipledirect simulations of the parabolic Khokhlov--Zabolotskaya--Kuznetsov (KZK) equation for various parameters of the source. It is shown that results obtained within the parabolic approximation can be used to describe the focal region of single element spherical sourcesas well as complex transducer arrays. It is also demonstrated that the focal pressure level at which fully developed shocksare formed mainly depends on the focusing angle of the source and only slightly depends on its aperture and operating frequency. Using the simulation results, a 256-element HIFU array operating at 1.5 MHz frequency was designed for a specific application of boiling-histotripsy that relies on the presence of 90-100 MPa shocks at the focus. The size of the array elements and focusing angle of the array were chosen to satisfy technical limitations on the intensity at the array elements and desired shock amplitudes in the focal waveform. Focus steering capabilities of the array were analysed using an open-source T-Array software developed at Moscow State University. Author Affiliation: (a) CIMU, Applied Physics Laboratory, University of Washington, Seattle, WA (b) LIMU, M.V. Lomonosov Moscow State University, Moscow, Russia * Corresponding author. Tel.: +7-495-939-2952; fax: +7-495-939-2952. (footnote)[white star] Peer-review under responsibility of the Ultrasonic Industry Association.

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Gale Document Number: GALE|A519365153