Transducer Theory

Understanding transducer theory as well as function is vital in performing clinical ultrasound tests on patients. A transducer can be defined as any device that converts one form of energy into another. Transducers are not just something used in the ultrasound world. There are many different kinds of transducers in the world. Some examples of transducers that we come in contact with in the real world are microphones, speakers, lasers etc. (Miele).

Transducers used in a clinical setting are quiet complicated. “However, they share many of their design characteristics with simple, single crystal, unfocused probes.” Describing the components of a simple probe often helps people understand transducer characteristics as well as function. A basic ultrasound transducer has a case, a cylindrical tube that protects the internal components of the transducer. The electrical shield is a barrier which lines the inside of the case. This shield aids in prevention of electrical noise from interfering with diagnostic images. The acoustic insulator is also a barrier. However the insulator isolates the components of the transducer from the case. One of the most important parts of the transducer is the piezoelectric crystal itself which is involved in energy conversion. One of the more obvious components of a simple probe is the wire. The wire provides an electrical connection between PZT or active element and the actual ultrasound system. The last two components that I am going to talk about are the more important ones, the matching layer and the backing layer. The matching layer is at the face of the transducer in front of the PZT. “The matching layer is designed with impedance between that of the active element in the skin.” The ideal mat...

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...er than the natural focus is called the far field, far zone or Fraunhofer zone (Miele).

There are many different types of transducers. I am going to briefly talk about one, the linear switched array probe. This probe is used for vascular 2D imaging, Doppler and color Doppler. This probe as you may know from using it creates a rectangular image. It is a great probe for vascular because it creates a wide linear image in the near field. On the downside we are unable to steer this transducer. That is why, “most linear transducers produced now are phased linear and not switched linear arrays” (Miele).

In conclusion, a transducer can be simplistically defined as anything which converts one form of energy to another form of energy. As I said before knowledge of transducer theory as well as function is necessary for anyone to successful in the field of ultrasound.