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.

Ultrasound Transducers for Pulse-Echo Medical Imaging

Transient fields of concave annular arrays.

On etudie comment les effets de la diffraction accentuent les limitations dans les mesures utilisant la methode par echo-impulsion et comment ces limitations peuvent etre surmontees pour des transducteurs avec ou sans focalisation

Diffraction Effects in Pulse-Echo Measurement

The conical scanner: a two transducer ultrasound scatter imaging technique.

The generation and detection of US and some fundamental physics of US propagation are summarised. Interactions with and effects on biological materials are described and pulse-echo, Doppler and other diagnostic methods and therapeutic and surgical methods are reviewed.

https://iopscience.iop.org/article/10.1088/0031-9155/22/4/001/pdf

Ultrasonics in medicine and biology.

The exact impulse response of field parameters for any field point on or off axis for the case where a circular disc radiator face is subjected to a displacement step corresponding to a velocity impulse is reviewed. By convolution, the transient field pattern for any arbitrary motion of the disc can be obtained. The exact response for a half-sine monopulse is computed. An approximate representation of the transient pressure response to the velocity impulse input at the disc is derived, and it is shown to correspond to the replica pulses described previously. The regions of validity of the approximation are quite limited and the replica pulses are displaced in time from the positions formerly attributed to them. The displaced replica approximation is applied to an examination of the structure of the near field for continuous sinusoidal excitation and a plot of positions of extrema is produced. It is shown that this approximation gives good agreement with the exact values and is superior to the previous published approach in this regard. For short sinusoidal pulses the effect of pulse length on the field pattern, and of field point on the time history of a transient wave are shown. When the excitation is a short sinusoidal pulse the effect of the pulse length and field point position on the field pattern and wave shape are demonstrated.

L. Bess

Papers

Near field transient radiation patterns for circular pistons