Experimental characterization of high-intensity focused airborne ultrasound fields.

High-intensity focused airborne ultrasound fields are increasingly applied in various technical fields, for example, to generate haptic feedback during gesture interaction. Reliable measurement data of sound pressure levels are required to assess potential health hazards to users. Such ultrasound fields pose special challenges for a quantitative characterization.

Heating of Polymer Films Induced by HIFU: Study of Acoustic and Thermal Effects.

This article presents the study of the thermal and acoustic effects occurring in polymer samples of different thicknesses receiving high-intensity focused ultrasound (HIFU). Whereas the heating mechanisms in polymer plates immersed in water are well known, the physical mechanisms enabling the heating of polymer films using a solid waveguide transducer remain not fully understood. A coupled acoustothermal finite-element simulation is conducted to model the sound field and the heat generation inside polymer samples of different thicknesses.

Thermal properties and changes of acoustic parameters in an egg white phantom during heating and coagulation by high intensity focused ultrasound.

A polyacrylamide phantom containing egg white has been proposed previously as an adequate tissue-mimicking material for high intensity focused ultrasound (HIFU) application. In this work, we report on measurements of egg white phantom thermal conductivity and specific heat capacity. We measured changes in acoustical properties which occurred during the heating and the coagulation process.

Modeling of interaction between therapeutic ultrasound propagation and cavitation bubbles.

In medical applications of high intense focused ultrasound the mechanism of interaction between ultrasound waves and cavitation bubbles is responsible for several therapeutic effects as well as for undesired side effects. Based on a two-phase continuum approach for bubbly liquids, in this paper a numerical model is presented to simulate these interactions. The numerical results demonstrate the influence of the cavitation bubble cloud on ultrasound propagation.

Full wave modeling of therapeutic ultrasound: efficient time-domain implementation of the frequency power-law attenuation.

For the simulation of therapeutic ultrasound applications, a method including frequency-dependent attenuation effects directly in the time domain is highly desirable. This paper describes an efficient numerical time-domain implementation of the power-law attenuation model presented by Szabo [Szabo, J. Acoust.

Reduction of tissue injury in shock-wave lithotripsy by using an acoustic diode.

An acoustic diode (AD) was constructed of two acoustic transparent membranes with good initial contact to allow the transmission of the positive pressure of lithotripter shock wave at an almost unaltered level, yet attenuate significantly its negative pressure, was fabricated. It was evaluated systematically on a Dornier HM-3 lithotripter to assess its application potential to reduce vascular injury without compromising stone fragmentation efficiency during shock-wave lithotripsy. By inserting the AD, the maximum compressive pressure, maximum tensile pressure and tensile duration of the lithotripter shock wave were formed to drop from 49.

Full-wave modeling of therapeutic ultrasound: nonlinear ultrasound propagation in ideal fluids.

The number of applications of high-intense, focused ultrasound for therapeutic purposes is growing. Besides established applications like lithotripsy, new applications like ultrasound in orthopedics or for the treatment of tumors arise. Therefore, new devices have to be developed which provide pressure waveforms and distributions in the focal zone specifically for the application.