Ultrasound Transducers for Pulse-Echo Medical Imaging

The transducer is probably the single most important component of any ultrasonic imaging system. A basic introduction to the problems and paradoxes of transducer design is given. After introducing the piezoelectric equations and discussing important transducer material such as lead zirconate titanate and polyvinylidene difluoride, the techniques for modeling the electromechanical impulse response are reviewed. Quarter-wave matching and short pulse techniques are discussed. The prediction of the ultrasound field of plane, spherical, and conical transducers is reviewed with emphasis on the spatio-temporal impulse response technique. Finally, the use of the above approaches is illustrated in a very practical fashion for three interesting transducer geometries: 1) a split aperture device with two focal lengths, 2) a five-element annular array, and 3) a 37.5 degree conical/annular array hybrid transducer.