Device to Improve the Efficiency of Extracorporeal Lithotripters

The design and construction of autonomous electronic instrumentation to generate fast high voltage discharges (6 to 10 kV) on a piezoelectric crystal array, in order to produce underwater shock waves, is described. If properly focused, hundreds of these shock waves are capable of destroying renal and ureteral calculi. This clinical treatment, developed more than 20 years ago, is known as extracorporeal shock wave lithotripsy (ESWL). In contrast to standard devices, our system produces two, rather than just one, shock waves with an adjustable delay between 50 and 950 sec. The objective is to enhance cavitation-induced damage to the kidney stone without increasing tissue trauma. Kidney-stone model fragmentation tests, obtained with the novel system, were compared to those achieved with a conventional piezoelectric shock wave generator, showing a 20% increase in fragmentation efficiency. Initial in vivo studies with animals have shown reduced tissue trauma.