a lithotripter for treating calculi has a housing formed by a first sub - housing with an opening with a membrane for contacting the patient , a second sub - housing composed of two parts with the first of the two parts forming a cylindrical bearing with the first sub - housing to allow rotation around an axis , a second part being mounted for pivotal movement on an axis extending perpendicular to the axis of rotation . the second housing part supports the source of the shockwave to create a shockwave on a central axis and includes a focussing arrangement mounted on the second part for focussing the shockwave on the central axis . to locate the calculus or stone , two scanning heads having sector scanning planes are mounted at a predetermined angle on the focus arrangement . to locate the stone , the second housing part is rotated to locate the stone in one of the scan planes , and then the second housing part is pivoted to move the second scan plane onto the stone .