Numerical Simulation Of HIFU Soumd And Temperature Fields

In this paper, numerical calculation is based on the Westervelt nonlinear acoustic wave equation and the Pennes bioheat equation with the method of finite difference time domain in oblate spheroidl coordinate system. In order to avoid a direct difference to the equation would lead to too much time layer, a method of the reference was amended to difference the equations in this paper. And a complete derivation.is gived to the method. Numerical results show that the method has an approximate result compare with the others, It also has a wide applied scope and simpler program.Different aperture examples are displayed for the amplitudes of sound pressure along and across the beam axis and the influence of parameters such as attenuation , velocity of sound on focusing sound are studied. And The temperature field of HIFU is numerical simulated in this paper. The results were the following:In such cases the geometric focal length, the larger circular aperture, the longer the focal length. Characteristics of focal regions are different for various medium. If the attenuation coefficient increases, the focus moves toward the sound source and the focal region shorten. If the velocity of sound increase,the focal distance will increase, and the pressure will de decrease.The results of this paper is helpful not only for the calculation of the sound and temperature fields of circular concave sound source, but also for the design of the HIFU thermotherapy plan and the circular concave high-intensity focused ultrasound transducer , especially for the large diameter transducer.