High-speed photographic evaluation of endoscopic lithotripsy devices.

Shock-wave generation and bubble formation occurring during endoscopic lithotripsy were studied using high-speed photography for various devices: a pulsed-dye laser, a Q-switched Nd:YAG laser and an electrohydraulic (EHL) apparatus. The three devices investigated generated gas bubbles that rapidly expanded and decayed. The maximal size of these bubbles was 5-8 mm for the pulsed-dye laser, 6 mm for the Q-switched Nd:YAG laser and up to 14 mm for the EHL device. The bubble size appeared to be governed mainly by the energy per pulse delivered by the lithotripsy device. The shock-wave pattern depended strongly on the type of device used; the 25-ns Q-switched Nd:YAG laser pulse generated a single pressure step, whereas the 1.5-microseconds pulsed-dye laser produced a train of shock fronts.