Capacitance hydrophones for pressure determination in lithotripsy

Capacitance hydrophones have been designed and applied for pressure measurements of shock waves in lithotripsy. Their working principle, properties, and design are discussed. Formulae are given, permitting the determination of pressures and calibration of hydrophones from electric measurements. Examples of comparative measurements with electrodynamic and PVDF hydrophones are presented, confirming the correctness of obtained peak pressure values. The hydrophones are characterized by high durability, small controlled nonlinearity, and a wide frequency band. However, they cause distortions in the shape of the overshoot of the measured shock wave pulses and their application is limited to measurements in the focal region.