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AbstractThe generation of blast wave in extracorporeal shock wave lithotripor (ESWL) takes advantage of the high-volt capacitor to release electricity and to generate electric arc between two electrodes. This arc heats the water around electrodes quickly and generates blast wave owing to the water volume expansion as well as the evaporated water bubbles. The blast wave generated at the first focus of a truncated ellipsoidal reflector will focus at the second focus which is the position of human calculus through reflection. The high pressure induced by shock wave focusing is the energy source of calculus fragmentation.The use of water as medium for lithotriptors is due to the fact that the sound impedance of water is nearly the same as that of human tissue. Thus water and tissue are viewed as the same medium. When a blast wave generated in water which has good acoustic contact with human tissue, only a little reflection occurs at the interface. The purpose of this study is to investigate the phenomena of blast wave focusing in water and the influence of different output settings on the maximum pressure caused by shock wave focusing on the lithotriptor LM 9200.Experiments were conducted mainly by using a pressure transducer and an oscilloscope and a PC based data acquisition system. It was found that the output voltage setting has great influence on the maximum pressure, the gasdynamic focus, and life time of the spark plug used.
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