[Destruction of urinary calculi using laser beams. Experimental principles and in vitro studies]

Despite recent therapeutic advances, urinary stone disease is still a main problem in urology. We investigated lithotrypsy of urinary calculi by the use of a Neodymium-YAG-laser. Application of laser power up to 88 W with a continuous wave laser and with a high power pulsed laser (220 microseconds/24,5 mJ to 10 ms/20 J) only lead to melting or burning of the stones. Irradiation with a Q-switched laser (12 ns/13,6 mJ) beam resulted in a burst of stone parts without complete fragmentation of the calculus, whereas the use of a Q-switched laser (12 ns/13,6 mJ) with an optomechanical coupler generated stress waves, which disintegrated stones into small parts. All experiments have been carried out in vitro. A possible technical application of the methods in vivo is discussed.