This equipment disintegrates kidney stones by means of shock waves. The particles of stone are then excreted in the urine.
The patient lies in large stainless-steel bath of water. As the human body is largely water, the waves are barely attenuated on passing through the skin. The patient is positioned so that the kidney is at one focus of an ellipsoidal reflector. Two cameras assist in positioning.
A spark discharge at the second focus emits shock waves, which are focused onto the stone in the kidney. The waves produce tension at the surface of the stone, which disintegrates from the outside inwards. The number of sparks depends on the size of the stone; it usually requires between 500 and 5000 per stone.