In vitro destruction of urinary calculi by laser-induced stress waves

A new, nonsurgical technique is proposed for the destruction of urinary calculi. This technique exploits recent advances in laser-fusion research in the generation of shock waves from high-intensity pulsed lasers and the principles evolved from extensive military research on fragmentation resulting from the interactions of shock waves on solids. In the in vitro experiments reported here, stress waves were generated by irradiating a thin film confined between glass and metal substrates with a high-intensity pulsed laser. It was shown that a nominal 2-J, Q-switched Ruby or Nd-glass laser is easily capable of producing stress waves of up to 10-kbar peak pressure and that the rise time of the stress pulse is on the order of the laser pulse duration. Urinary calculi (kidney or bladder stones) of different sizes, shapes, colors, hardnesses, and composition were fragmented by laser-induced shock waves into sizes quite capable of being passed spontaneously. Critical laser parameters have been determined, and the associated threshold pressure for the destruction of the hardest types of urinary stones has been measured. The possible application of this technique to in situ destruction of urinary calculi is described.