First in vitro experiments using a new reflector to concentrate shock waves for extracorporeal shock wave lithotripsy

Abstract

Electrohydraulic lithotripters to perform extracorporeal shock wave lithotripsy (ESWL) treatments use symmetrical reflectors in order to concentrate the energy generated in one of their foci (F1). The new reflector presented here was designed in an attempt to increase the efficiency of ESWL. It is obtained by combining sectors of two rotationally symmetric ellipsoidal reflectors with different separations between their foci F1 and F2. These sectors are joined together in such a way that the F1 foci coincide, creating a separation between the F2 foci. The purpose is to temporally and spatially dephase the shock wave generated at F1. This is achieved because the initial shock wave is divided, by reflection, into two shock fronts converging toward two, rather than one, F2 foci. Pressure measurements, and in vitro experiments using kidney-stone models and dog kidneys, indicate that the new design could be more efficient in breaking up renal stones, without producing more tissue damage. The performance of the new reflector was compared with one having the geometry of a Dornier HM3 (nonmodified) reflector. Both reflectors were installed separately in an electrohydraulic experimental shock wave generator (MEXILIT II). [Work supported by DGAPA IN502694, UNAM.]