DESIGN AND CHARACTERIZATION OF A SHOCK-WAVE GENERATOR USING CANALIZEDELECTRICAL-DISCHARGE - APPLICATION TO LITHOTRIPSY

During, recent years, much work has focused on breaking urinary and bi liary stones using extracorporeal shock wave devices. Up to now, in te rms of fragmentation efficacy, the ''electrohydraulic'' principle is t he gold standard. In an electrohydraulic shock wave generator, a plasm a is created by a high-voltage electrical discharge between two underw ater electrodes. This kind of shock wave generator has a significant d rawback because of the large variations of pressure pulses. Moreover, the wear of the electrodes is considerable, leading to nonconstant ele ctrical discharge conditions all along the treatment. A new method to canalize the plasma between the electrodes, using highly conductive li quid, was investigated. Based on this principle a new spark plug was d esigned. This paper deals with the description and the characterizatio n of this new type of spark plug. The electrical and geometrical param eters are presented. Measurements of the focal point pressure amplitud e, of the spatial pressure distribution using different voltage settin gs, are reported. The acoustic energy in the focal zone is computed. W e show that using this principle, the wear of the electrodes has been tremendously reduced. A comparison of in vitro results with other shoc k wave technologies shows that this new spark plug represents a signif icant breakthrough in terms of stone fragmentation efficacy. This spar k plug is not only useful in the medical field, but it should also be of great interest to laboratories.