Ultrasound imaging
Ultrasound imaging creates a picture of something that cannot be seen directly, such as an unborn baby in the womb (a foetus), or faults and defects inside metals.
These uses rely on what happens when ultrasound waves meet the boundary between two different materials.
Medical uses of ultrasound
The best known example of the use of ultrasound is medical imaging, to 'see' inside a body.
An ultrasound scanner is simply run over the skin to obtain an image of what's inside.
The scanner probe has a built-in sensor that directs ultrasound pulses down into the body.
- Some of the ultrasound waves are reflected at a boundary, for example, the boundary between muscle and bone;
- the time taken for the waves to leave a source and return to the detector is measured;
- the depth of the boundary can be determined using distance = speed of sound in the material multiplied by the time taken.
The probe receives the reflected waves and a computer connected to the scanner uses them to draw an image on a screen.
Advantages of using ultrasound in medicine
- Ultrasound waves pass through tissue without causing harm, unlike x-rays which can damage DNA inside cells.
- Ultrasound equipment is relatively cheap, portable and easy to use.
- Images of internal organs can be seen without having to operate on patients.
