Confocal lens focused piezoelectric lithotripter

Usually, piezoelectric lithotripters consist of a high quantity of small flat piezoelectric discs tied to a spherical structure, where the focus is the geometric center of the sphere. The small diameter of the ceramics compared to the distance to the focus of the lithotripter means that only a fraction of the surface pressure will arrive to the focus, and also results in a very small focal diameter. This work focus on the evaluation of a new type of piezoelectric lithotripter with similar dimensions of a commercial lithotripter and composed of either 3 or 4 large lens focused piezoelectric transducers with focal pressure up to 25 MPa each, set either in a confocal C-shape or confocal ring-shape. Each transducer is made with a 92 mm diameter flat piezoelectric ceramic disc of 220, 300, or 400 kHz thickness frequency and the acoustic lens shape was calculated using finite element optimization in order to maximize its focusing capability. Comparison of artificial stone comminution efficiency depending on the frequency, pressure, and the setup of the piezoelectric transducers were made and compared to commercially available lithotripters. [Work supported by an industrial grant from EDAP-TMS.]Usually, piezoelectric lithotripters consist of a high quantity of small flat piezoelectric discs tied to a spherical structure, where the focus is the geometric center of the sphere. The small diameter of the ceramics compared to the distance to the focus of the lithotripter means that only a fraction of the surface pressure will arrive to the focus, and also results in a very small focal diameter. This work focus on the evaluation of a new type of piezoelectric lithotripter with similar dimensions of a commercial lithotripter and composed of either 3 or 4 large lens focused piezoelectric transducers with focal pressure up to 25 MPa each, set either in a confocal C-shape or confocal ring-shape. Each transducer is made with a 92 mm diameter flat piezoelectric ceramic disc of 220, 300, or 400 kHz thickness frequency and the acoustic lens shape was calculated using finite element optimization in order to maximize its focusing capability. Comparison of artificial stone comminution efficiency depending on the...