Optimization of operating frequency of acoustic transducers for obtaining maximum temperature in HIFU based therapeutic ablation

High intensity Focus Ultrasound therapy relies on acoustic power absorbed by tissue. Acoustic absorption is a function of frequency: while a relatively lower frequency allows the beam to propagate farther in the tissue, the absorption, and, hence, the heat generated at the focal point is poor. At higher frequencies, on the other hand, tissue at the focal point is capable of absorbing most of the incoming acoustic energy, but loss along the propagation path significantly reduces the strength of the received signal. One figure of merit for finding the optimal frequency is the spatial peak of the acoustic power absorption density. In this paper, we analyze the same problem with the figure of merit taken as the peak temperature at the focal point and show that this may lead to a different frequency at which this value is maximized.