Non-linear Transform of Energy in Strongly Focused Finite-Amplitude Ultrasound
Abstract:This paper studies the non-linear effect of a high intensity focused ultrasound (HIFU) field by solving the spheroidal beam equation (SBE), using a frequency domain method. The spheroidal beam equation is a parabolic equation and has been shown to have a specific application to a wider aperture angle HIFU transducer. The linear and non-linear SBE's are solved to predict the HIFU field with half-aperture angles of (10°, 20°, 30° and 40°). The KZK equations with various aperture angles are also solved for a comparison. The HIFU fields in water and tissue are studied and the influences of the aperture angle and source pressure level on the heat deposition distribution are discussed. Because of the non-linear effect, a high source pressure level shifts the focal position, and the non-linear heat deposition is evidently larger than the linear one at focus. However, the volume of the focal region given by the non-linear theory is much smaller than that given by the linear theory. Furthermore, a wider opening of the transducer enhances the non-linear characteristics; a wider aperture angle makes a contribution to the non-linear characteristics of the focus field, and a higher source pressure level has a similar effect.
Document Type: Research Article
Publication date: November 1, 2005
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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