Self focusing on extended objects with time reversal mirror, applications to lithotripsy

The objective is to focus an ultrasound beam on a target during lithotripsy. We propose to study the concept of a piezoelectric shock wave generator in which the focal zone is moved electronically to track the stone. For this purpose, we use the autofocusing property of time reversal mirrors (TRM) to track in real time a gall bladder or kidney stone embedded in its surrounding medium. We show that TRM allows us to obtain a sharp focusing on one bright point of the stone. The time of flight profile is then determined and used in a minimization method to calculate the spatial coordinates of the stone