Ultrasound stone localisation for extracorporeal shock wave lithotripsy

An extracorporeal shock wave lithotriptor using an ultrasound scan head pantograph location system has been designed. The shock wave ellipsoid reflector position is adjusted to the stone with a computer assisted positioning device. Seven dogs with stones implanted into the renal pelvis were treated and stone fragmentation occurred in all cases. Subsequently, 45 patients with stones were treated. The stones ranged in size from 5 to 29 mm (mean 16). Radio-opaque as well as poorly opaque or radiolucent stones were treated and fragmentation was achieved in 85% of cases. An additional endoscopic procedure was performed in four cases. No fragmentation occurred in four patients. Further shock wave treatment was necessary in two patients who presented with stones larger than 2 cm. Both radio-opaque and poorly opaque stones can be treated with this system. Ultrasound localisation and the ellipsoid positioning device avoid the need for expensive fluoroscopic equipment and a hydraulic patient positioning system.