A Robust Hydrophone for Evaluation of Lithotriptors

A polymeric membrane style hydrophone is commonly used to calibrate lithotriptors. This commercially available device has a fast rise time and acceptable sensitivity but a very short life span. We propose a new style of hydrophone here that overcomes the longevity problem and yields superior sensitivity. The design employs a spot poled ceramic active element backed by a matched acoustic impedance. This hydrophone will be able to measure pressures as high as 100 MPa for thousands of shocks without any serious degradation in sensitivity or pulse shape. Furthermore, such a hydrophone is expected to reproduce negative (rarefactional) pressure faithfully. Moreover, the proposed technique will gain the benefit of having well defined and potentially very small (less than 0.5 mm diameter) active areas. The new hydrophone is also expected to be used as a versatile tool in precisely mapping the acoustic fields generated by a wide range of therapeutic and diagnostic transducers in common use. Thus the proposed low cost device will have great commercial potential.