Ultrasound Transducers

Describe the design on the machine and how their component parts work to produce an image.

First used in medicine in the 1950s, Ultrasound is today used across a variety of fields. Using high frequency sound pulse with no radiation risk, Ultrasound is considered a safer application of imaging. Modern ultrasound equipment is based on some of the same principles used in first devices.(Chan, and Perlas, 2011) Based on the pulse-echo principle, ultrasound pulses are created by transducers, directed into patients’ bodies as narrow beams which are reflected off tissues, returned along the same path as the original pulses and detected as echoes.

Transducer

An ultrasound machine’s main components are the probes; named as transducers these devices convert energy from one form to another - in Ultrasound converting electrical energy into sound.(Ball and Moore, 2008) Easton(2009) states transducers come in different shapes, sizes and frequencies. There are three main types of transducers: Linear-array, used in vascular and musculoskeletal applications; Curvilinear-array, used for abdominal and obstetric scanning and Phased-array, usually used in cardiac scanning.(Gibbs et al, 2009)

Design of Transducer

Transducers contain the crystal lead zirconate titanate, designed and fitted into the probe in thin, rectangular slabs referred to as elements. A conducting layer of silver covers the front and back faces of each element forming electrodes and having electrical leads attached where the alternating voltage is applied.(Fairhead and Whittingham, 2012)

Based on the piezoelectric effect, the transducer’s function is to emit short pulses and receive echoes of the pulse, a process repeated “over a sequence of directions to cover a 2D sectional fie...

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...and around the sides, generated by a powerful cryogenic electromagnet. Spinning protons, forming the nucleus of hydrogen atoms, have magnetic properties causing the protons in the body to align with the magnetic field in the same direction. We know from Ball and Moore (2008) that hydrogen is found in great volume in body tissues. The protons, exposed to short pulses of radiofrequency, disturb the alignment and cause the protons to flip from longitudinal to transverse plane. When hydrogen protons re-align and relax back to their original position they emit a small, weak radio signal, which is detected by either an antenna or coil. The radio signals are analysed by a computer, determining spatial distribution and chemical bonds of hydrogen atom. This generates an image, displayed as a two-dimensional grey-scale slice image.(Easton, 2009; Ball and Price, 1995)