Ultrasound scans

Ultrasound is an important scanning technique as it does not use radiation and is therefore a very safe method of finding out what is going on inside the body. 

How it works

Ultrasound uses sound waves to make an image because different tissues reflect these sounds in different ways (though the human ear cannot hear these sounds). These sound waves are recorded and turned into an image by a computer.

If your Great Ormond Street Hospital (GOSH) doctor needs to find out what is happening in your body, an ultrasound can create an image of your organs. They are often used during pregnancy as they can create clear pictures of the baby without using radiation which could harm the baby. It is particularly good for showing organs that are filled with liquid such as the bladder and the gallbladder (these do not show up well on x-rays). Ultrasound cannot show organs which are behind bone such as the brain and heart.

Sometimes ultrasound is used at a high frequency as a treatment by physiotherapists to warm tissues and to assist with treatments. It can be used to help arthritis and fractures.

What happens

This will all depend on which part of the body you need scanned. You will probably have to wear a gown and lie on a couch and you may be asked not to eat or drink beforehand.

The person performing the scan will either be a doctor (radiologist) or a radiographer who is trained in ultrasound. They will place some gel on the body part (this is used to help the microphone move smoothly making it easier to pick up the sound waves). They will then move the microphone around over the body part and the image will show up on the computer screen.

It is painless; you should only feel a slight press of the microphone.

Ultrasound scans usually take between 10 and 30 minutes.


The person who performed your scan will have a look at the images and write a report for your doctor. This may take a few days.

Compiled by:
Great Ormond Street Hospital
Last review date:
October 2016