Chilibon I., Wevers M., Lafaut J.

This paper presents a study for the efficiency improvement of a modified extracorporeal shock wave lithotripter (ESWL) system utilized for disintegration of renal calculi. When a shock wave generated by an extracorporeal shock wave lithotripter (ESWL) interacts with a solid, it creates cavitation bubbles at the interface between the solid and the surrounding liquid. The implosion of the cavitation bubbles plays an important role in the disintegration of renal calculi. The stresses generated at bubble implo-sion are larger than those generated during incidence of the primary shock wave. The ElectroMagnetic Acoustic Source of a Lithostar lithotripter initiates the incident shock waves into the water, and an ul-trasound transducer, centered into the extracorporeal shock wave lithotripter system provides an im-portant role by enhancing the cavitation effects of the bubbles in the target fragmentation. Lithostar generates transient cavitation bubbles, which grow by the ultrasound waves to their maximum sizes and then collapse violently on the target surface inducing material damage. The underwater piezoelec-tric sandwich transducer is supplied by IWATSU SG-4511 Function/Pulse Generator and converts the electrical signals in mechanical vibrations, which are propagated into the water tank towards the Cal-cium-silicate target. The transducer exhibits low resonance frequency, tunable energy and broad-bandwidth. Underwater shock waves received by PVDF sensor (Poly-Vinyl Difluoride) are converted in electrical signals and displayed by LeCroy 9310 AM oscilloscope. Using an experimental modified ESWL system we revealed an improvement of cavitation such as: size increasing of cavitation bubbles, better directivity of acoustic field, and shorter period for material tar-get fragmentation.