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Chapter 6

MEDRADSC 2Z03 Chapter Notes - Chapter 6: Piezoelectricity, Ultrasonic Transducer, University Of Manchester


Department
Medical Radiation Sciences
Course Code
MEDRADSC 2Z03
Professor
Dawn Danko
Chapter
6

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Production of Sound
The face of an ultrasound transducer is made of a piezoelectric material.
When a voltage is applied across this material, it is deformed.
By alternating the polarity of the voltage, the piezoelectric material expands and
contracts.
This causes the production of mechanical pressure waves, which are transmitted
into the body as sound.
The returning echoes compress the material, which in turn causes the generation
of tiny voltages.
These voltages are then sent to the image processor to generate an image.
In real time ultrasound, this process of a short burst of sound followed by the reception of
the echo is repeated multiple times each second – intervals between pulses are often
between 0.1 and 1 msec.
Early ultrasound transducers were composed of a single piezoelectric element.
Current technology now delivers a new generation of transducers, designed with
piezoelectric material sliced into multiple discrete elements, each with its own set
of electrodes.
The advantage of having multiple elements is that their firing can be precisely
timed, allowing the beam to be electronically manipulated, to allow steerage of
the beam, for example.
Figure 1, below, is a diagrammatic representation of a curved transducer.
Figure 1: Elements in a curved transducer
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