Mechanism of fragmentation of urinary stones by underwater shock wave.

The focusing of an underwater shock wave, generated by an underwater microexplosion, has been studied by several methods, such as holography, pressure measurement and pressure print. It has been shown that the shock wave could be focused within the range of a few millimeters and with an amplitude of 1 kbar. The acoustic impedances of various kinds of urinary stones were measured by the original graphical method using holographic interferrometry. The process of breaking a stone by a focused underwater shock wave was observed with high-speed cinematography. It was supposed that the main mechanism of breaking the stone is the tensile stress at the solid-water acoustic interface.