Behavior of propagation and heating due to absorption of ultrasound in medium

Recently, ultrasound waves have been put to practical use not only in diagnostic equipment but also in thermotherapy that uses the effect of ultrasound waves in a living body. The analysis of temperature rise due to the absorption of ultrasound in a soft tissue medium is an important analyzing object for the clarification of the effect of ultrasound waves in biological tissues and the estimation of medium constants. Three-dimensional simulations by the finite-difference time-domain (FDTD) method which used the equations that considers the absorption attenuation based on acoustic basic equations (ABEs) and the Westervelt equation have been performed. The consistency between the ABEs and the Westervelt equation is confirmed. The results of temperature measurement that uses glycerin as the absorbing medium of ultrasound are compared with those of FDTD simulation. The temperature distribution obtained by FDTD simulation almost corresponds to that obtained by experiment.