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As the name suggests, ultrasound uses sound waves to make an image of the inside of the body. These sound waves are given off by a transducer (a type of microphone) which is placed on your skin. When the waves reach the different densities/textures of the tissues and organs inside your body, they are echoed back to the transducer. The instrument uses these echoes to construct a picture or image of these tissues and organs and this is shown on a screen for the operator to see. You may also be able to see the screen, but the scans are rather difficult to interpret, and it may just look a bit like changing patterns of black and white static.
This section gives you more detail about the physical principles underlying the ultrasound scanning technique. You don’t have to know this in order to understand what will happen in the scanning room or to understand your scan result, but if you are interested, read on: How Does the Ultrasound Scanning Technique Work?
At the time of your scan, you may be shown into a cubicle and asked to remove your outer clothing and to put on a hospital gown depending on the part of the body that is to be scanned. Then you will be asked to lie down on the scanning bed next to the ultrasound instrument. The ultrasonographer (the ultrasound scanning technician) will place a gel on your skin on the area to be scanned. The gel helps to eliminate any interference between your skin and the transducer. The transducer will be moved back and forth over the area being scanned and a constantly changing picture will be transmitted back to the instrument and shown on the TV monitor on the ultrasound machine. Most ultrasound scans take about half an hour.
Unlike CT and nuclear medicine, ultrasound does not use ionising radiation. It is considered a very safe technique although there is some caution over the use of pulsed Doppler ultrasound in pregnant women.