How it works
The ultrasound scanner sends out a pulse of ultrasound through a transducer at a frequency typically in the range 3 to 5 MHz for usual systems. The transducer is placed on the abdomen of the pregnant woman and the pulse of ultrasound is send through the tissue and into the womb. The sound is reflected by structures including muscles, internal organs etc. The reflected sound is captured by several individual piezo elements, then analyzed and results displayed on a screen as an image of the baby inside. The most common systems utilize a linear sensor, providing a “slice” image. Using beamforming techniques, it is possible to determine where the reflected sound comes from and thereby locate the structures in the plane.
Which piezo elements can be used for an ultrasonic scanner?
Devices for medical imaging are usually fitted with a linear array containing for example 16, 32 or 64 monolayer piezo elements, controlled individually. Softer ceramics tend to be preferred for their low quality factor, providing a large bandwidth. The individual elements are relatively small and operate at low power, high frequency. A transducer can for example be built out of thin plates of our NCE51 material, providing a resonance in thickness mode at 4MHz.