Application of the parabolic equation method to medical ultrasonics

The application of the parabolic equation (PE) method is extended to hypert hermia and imaging problems in medical ultrasonics. It is shown that the PE provides an accurate solution of the acoustic field generated by a pre-foc used array through an inhomogeneous medium. To investigate hyperthermia the rapy, the PE is coupled with the heat equation. Simulations provide evidenc e that this interaction defocuses the acoustic field and degrades the effic iency of the hyperthermia treatment, We propose a procedure to maintain the focus in the zone of interest using two arrays and phase-conjugation invar iance properties. For medical imaging, an algorithm is developed to move th e focal spot of a linear array in any direction using a frequency shift in a time-reversal mirror (TRM). Simulations demonstrate that the proposed alg orithm can be applied to an inhomogeneous medium in the presence of an aber rating layer without the knowledge of the medium properties. (C)2000 Elsevi er Science B.V. All rights reserved.