The advantages of focusing in parametric sources

The generation of a low frequency wave in fluids is possible as a consequence of parametric radiation provided that the two primary frequencies are set close to each other. In this theoretical study, the radiation patterns of primary waves versus the radiation axis were plotted. Similarly, the results for the case of focusing were presented. In each case, distributions of the difference-frequency (low-frequency) waves were investigated. Simple analytic formulations of Novikov et al. [1] for the case of a Gaussian amplitude shaded source are adopted. The source dimensions and frequency ranges were selected to be proper for practical therapeutic applications. Finally, it was attempted to present an "efficiency" measure for the parametric focusing sources in biomedical studies

A NONINVASIVE FOCAL FIELD INTENSITY ESTIMATION METHOD USING FINITE-AMPLITUDE EFFECTS IN ULTRASOUND HYPERTHERMIA

A method for noninvasive in situ estimation of intensity in ultrasound hyperthermia is presented. The method employs the nonlinear theory of sound propagation in a focused ultrasound hyperthermia system in order to determine the focal field intensity, where the sound intensity levels are relatively high in the focal volume