An ultrasound scan, sometimes called a sonogram, is a procedure that uses high-frequency sound waves to create an image of part of the inside of the body. They can be used to monitor an unborn baby, diagnose a condition, or guide a surgeon during certain procedures.
Most ultrasound scans last between 15 and 45 minutes. They usually take place in a hospital radiology department and are performed either by a radiologist or a sonographer.
How Ultrasound Scans Work
A small device called an ultrasound probe is used, which gives off high-frequency sound waves. You can't hear these sound waves, but when they bounce off different parts of the body, they create "echoes" that are picked up by the probe and turned into a moving image. This image is displayed on a monitor while the scan is carried out.
Before an Ultrasound Scan
Before having some types of ultrasound scan, you may be asked to follow certain instructions to help improve the quality of the images produced. For example, you may be advised to drink water and not go to the toilet until after the scan, or avoid eating for several hours before the scan (this may be needed before a scan of your digestive system, including the liver and gallbladder)
Depending on the area of your body being examined, the hospital may ask you to remove some clothing and wear a hospital gown.
If you need a sedative to help you relax, this will be given through a small tube into the back of your hand or into your arm. In some cases, you may also be given an injection of a harmless substance called a contrast agent before the scan, as this can make the images clearer.