Simulation of automatic selection in multi-target medium using time reversal mirror

In high intensity focused ultrasound (HIFU) therapy, the focusing of acoustic waves in inhomogeneous media is a common and difficult problem to solve. The focusing can be strongly degraded by sound speed variation and density variation from geometrical distortion. The time reverse mirror is a solution to this problem when the target is a reflective one, even when the location of the target is unknown. The iterative time reversal mirror is also used to automatically select the strongest target in a multi-target medium. To simulate the acoustic fields of iterative time reversal mirror and evaluate its convergence, the FEM time-dependent model is used. Three cases of time reversal process in multi-target medium are presented. It is shown that in these three cases, the iterative time reversal process has the ability to focus on the strongest target. And the effectiveness of convergence is discussed in these three cases.