Ultrasound - Basics
| What does "Ultrasound" mean? |
Ultra = High or extreme
Ultrasound = sound waves above the frequency detectable by human ears |
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| Physiology |
Ultrasound or ultrasonography
is a medical imaging technique that uses high frequency sound
waves and their echoes. It is used to form an image of organs
or tissue inside the body non-invasively. The technique is similar
to the echolocation used by bats, whales and dolphins.
Ultrasound is also used as a physiotherapy treatment where the sound waves are used to warm muscle tissue deep inside the body. |
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| How it works |
The ultrasound machine transmits high-frequency (1 to 5 MHz)
sound pulses into the body using a probe. The probe has special
crystals that generate the sound waves and also detect sound
waves reflected.
When the sound waves hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone) some of the sound waves are reflected back to the probe and the rest travel on further until they reach another boundary and are reflected back. The reflected waves are detected by the probe and relayed to the machine. The machine calculates the distance from the probe to the tissue or organ (boundaries) using the speed of sound in tissue (1,540 m/s) and the time of each echo's return (usually in the order of millionths of a second). The machine displays the distances and intensities of the echoes on the screen and forms a two dimensional image like the one shown below. |
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| Picture of equipment |
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