This is a way to get a picture of your liver. A tiny amount of a radioactive chemical is injected into a vein in your arm. The chemical collects in the liver, especially where there is more cell activity, and gives out gamma rays. This collection process takes time, so you may be asked to wait for an hour or two.

Then you will be asked to lie still on a couch while the gamma rays are detected by a gamma camera. From it, a computer builds up a colour picture of activity hot spots in your liver. This may take up to 20 minutes. You may have to wait for a further few hours if a second picture is needed.

The chemicals used are regarded as safe, and will pass out of your body in your urine. The dose of radiation you receive is usually equal to two or three normal X-rays.