Ultrasonic transducers: design, construction and applications

In the last twenty years or so applications of ultrasound have increased enormously. This is true of both industrial and medical applications. Indeed, in the medical field, ultrasound is now the most used imaging modality, having pushed X–ray imaging into second place in the last year, according to information from one of the major medical imaging companies. The tremendous strides that have been made in medical ultrasound owe much to the application of image processing and microelectronics technology. However, the ultrasound transducer is almost always the limiting factor in extracting better performance from an imaging system. This being so, it is appropriate to concentrate on the design of ultrasound transducers if improvements are to be obtained. If the physical limitations to the extraction of information using ultrasound are examined, then it is seen that there is still tremendous scope for improvement in terms of the materials used for ultrasound transducers and in the overall design of their structure. This accounts for the very considerable research effort worldwide. In this paper we begin by reviewing some fundamental aspects of ultrasound and then consider the design aspects of single–element and multi–element ultrasound transducers. Finally, some indications of application areas for such transducers are provided, together with a brief review of very recent developments.