Ultrasound is simply sound that has a very high frequency.
Humans are not able to hear ultrasound, though some animals can hear them.
Sounds with frequencies above 20 000 hertz are called ultrasounds.Ultrasound is used for examining soft tissue inside the body.
Parts of the body that may be examined include muscles and unborn babies.
Blood flow can also be monitored using ultrasound.Modern ultrasound equipment can produce 3D images The images so far have been of static images, ultrasound captures movement.
This baby is so pleased to see you it’s waving!Ultrasound is very safe. There is no firm evidence that it does any harm to the body (or the baby in the case of pregnancy scans).
X-rays are potentially dangerous, particularly to young children and pregnant women (they damage the unborn baby).Medical ultrasound systems use very high frequencies – several megahertz (mega means million or 106).
A sound is a wave it has all the usual wave properties (reflection, refraction, diffraction). Ultrasound imaging makes use of the fact that sound can be reflected.
The idea is just like that used in radar and sonar.
A thin layer of jelly is placed between the probe and the skin to make sure all the sound enters the body.
The probe contains a transmitter and a receiver.
A pulse of ultrasound is sent out by the transmitter.
The pulse is reflected from a surface and returns to the receiver.The ultrasound machine measures how long it takes for the pulse to return
Colour enhancement to show blood flow
Digital files for examination on computers
Millions of sound waves are transmitted every second.
As the waves reflected at different times, the computer in the ultrasound machine calculates how far the wave travelled before being reflected (using d=vt).
Using this information the computer builds up an image of the inside of the patient.
Ultrasound is sound with a frequency above 20 000 Hz. If you have just said that it is a sound we cannot hear, that is not quite accurate enough.
Ultrasound can be used for examining soft tissue inside the body. For example, muscle, the heart and unborn babies.
The following are ultrasound frequencies:
23 000 Hz, 36 kHz, 4 MHz, 0.58 MHz, 600 000 Hz
Ultrasound does not have any damaging effect on the body. It is entirely safe to use, even on very young foetuses. X-rays are harmful, particularly on young and unborn children.
Most of the problems involving ultrasound need you to use v=d/t or v=fl
Things to look out for:
Units- time will often be in milliseconds (ms). Take care not to get this confused with metres per second (m/s or ms-1). and distances may be in mm or cm
There will often be an echo (or reflection involved. This means that you will need to think carefully about the times and distances involved.
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