Modelling and numerical simulations of in-air reverberation images for fault detection in medical ultrasonic transducers: A feasibility study

A simplified two-dimensional finite element model which simulates the in-air reverberation image produced by medical ultrasonic transducers has been developed. the model simulates a linear array consisting of 128 pzt-5a crystals,a tungsten-epoxy backing layer,an araldite matching layer,and a perspex lens layer. the thickness of the crystal layer is chosen to simulate pulses centered at 4 mhz. the model is used to investigate whether changes in the electromechanical properties of the individual transducer layers (backing layer,crystal layer,matching layer,and lens layer) have an effect on the simulated in-air reverberation image generated. changes in the electromechanical properties are designed to simulate typical medical transducer faults such as crystal drop-out,lens delamination,and deterioration in piezoelectric efficiency. the simulations demonstrate that fault-related changes in transducer behaviour can be observed in the simulated in-air reverberation image pattern. this exploratory approach may help to provide insight into deterioration in transducer performance and help with early detection of faults. © 2015 w. kochański et al.