Generation of very high‐pressure pulse using time reversal in a solid waveguide: Application to lithotripsy Free

The use of a piezoelectric transducers array has opened the possibility of electronic steering and focusing the beam to track the stone. However, due to the limited pressure delivered by each transducer (typically 10 bars), the number of transducers needed to reach the focus an amplitude of the order of 1000 bars is typically of some hundred of elements. Here, we present a new solution that combines the use of the time reversal method with a small number of transducers that generate low‐amplitude waveforms in a solid waveguide to obtain the shock wave of very high amplitude in tissues located at the front of the waveguide. We use the fact that, due to time reversal invariance, for every burst of ultrasound diverging from a source and reflected by the boundaries of the waveguide, there exists in theory a set of waves that retraces all of these complex paths and converges in synchrony, at the original source. As the temporal dispersion of the waveguide increases, the time reversed wave is temporally recompressed with a stronger amplitude amplification. Such an effect allows a very high spatio‐temporal recompression to be reached and to obtain a small number of transducers the amplitude needed to break stones.