[Extracorporeal shockwave destruction of urinary calculi after ultrasonic localization]

Shock waves generated by an underwater spark gap discharge, focused by an ellipsoid can destroy most urinary stones extracorporeally. A device were stones are localized by ultrasound and where the ellipsoid itself could move to be positioned in the adequate position would obviate the need for a very expensive two fluoroscopes localisation system, and patient positioning device. A regular ultrasound probe was fixed on a multijointed metallic arm. From the measurements of the angles of every point it was possible to calculate the exact coordinates X, Y, Z, of the probe. This system, thought not extremely flexible allows to perform ultrasound examination of a kidney in the bathtub and localisation of stones in vivo in good conditions. When the stone was seen on the screen, the angles given to the joints were automatically recorded and the coordinates of the stone were instantly calculated with a personal computer. The computer program was able to calculate the displacement of the ellipsoid necessary to adjust its focal point on the X, Y, Z coordinates. The ellipsoid moved through a simple 3 motors system. Destruction of the stone was performed by shock waves. Progression of the disintegration was followed by plain X-rays performed in the bath tube with a portable X-ray apparatus. This device was tested in 7 dogs with stones surgically implanted in the renal pelvis. In every case, the stone was localised and disintegrated in fragments of the order of one millimeter using 700 to 2 000.(ABSTRACT TRUNCATED AT 250 WORDS)