Piezoelectric Effect in Ultrasound
Hopefully you have already heard about Piezoelectric Element or Effect. 'Piezo' is derived from the Greek piezo or piezein (πιÎζειν), which means to squeeze or press. The piezoelectric material is the material that produces diagnostic ultrasound.
Piezoelectric materials may be naturally occurring, such as quartz and tourmaline, or man-made. The piezoelectric material that is commonly used in current ultrasound transducers is a man-made ceramic called 'lead zirconate titanate' (PZT). The PZT is the actual transducer inside the scan-head. It may also be referred to as the crystal, the element, or simply, the transducer.
Now what are the properties of this Piezoelectric Element? Piezoelectric Element has two interesting properties:
1. It changes shape when electricity is applied to it.
2. It generates electricity when pressure is applied to it.
Actually this is the mechanism we use in an ultrasound machine. When electricity is applied to a transducer through a cable, Piezoelectric crystals change their shape. Thus a vibration or sound is generated. This sound or vibration travels through the patient's body. When it is reflected from different types of tissues, it comes back to the transducer and produces a pressure over the Piezoelectric materials. Now Piezoelectric materials generate electricity as pressure was applied to it. The machine converts this electrical energy to an image. Then we can see the image of the patient's organs on our monitor.
So in short, this is the mechanism we use in an ultrasound device.
References:
1. EXAMINATION REVIEW FOR ULTRASOUND: SONOGRAPHIC PRINCIPLES & INSTRUMENTATION (SPI) by Steven M. Penny, Traci B. Fox, Cathy Herring Godwin
2. Wikipedia.org
3. Manual of diagnostic Ultrasound; edited by P.E.S. Palmer (World Health Organization)