A radioisotope scan (also known as a nuclear medicine test) uses a small amount of radioactivity to produce pictures on a special camera. The radioactive dose is usually injected into a vein in your hand or arm. The radioactivity circulating in your body emits radiation (gamma rays) which are detected by a ‘gamma camera‘ and leave an image on the computer. From that computer image the doctor working in the area will draw conclusions and write a report which will be given to you or your doctor. It contains very useful information about a disease process in the body and is also used to know about any organ under study.
How does a radionuclide scan work?
A radionuclide (sometimes called a radioisotope or isotope) is a chemical which emits a type of radioactivity called gamma rays. A tiny amount of radionuclide is put into the body, usually by an injection into a vein.
There are different types of radionuclides. Different ones tend to collect or concentrate in different organs or tissues. So, the radionuclide used depends on which part of the body is to be scanned. For example, if radioactive iodine is injected into a vein it is quickly taken up into the tissues of the thyroid gland. So, it is used to scan the thyroid gland.
Cells which are most ‘active’ in the target tissue or organ will take up more of the radionuclide. So, active parts of the tissue will emit more gamma rays than less active or inactive parts.
Gamma rays are similar to X-rays. The gamma rays which are emitted from inside the body are detected by the gamma camera, are converted into an electrical signal, and sent to a computer. The computer builds a picture by converting the differing intensities of radioactivity emitted into different colors or shades of grey.
What preparation do I need?
Usually you don’t need much of anything. Your doctor/ reception of the hospital should give you specific information (if any) to help you prepare for these tests. As these tests involve a small amount of radiation, pregnant women should not have them. Let your doctor know if you are, or think you could be, pregnant. You should also let your doctor know if you are breast-feeding. For some types of scan, you may be asked to have lots to drink to help to flush the radionuclide from your body or help in better accumulation of isotope in the body organs like skeletal system.
What happens during a radionuclide scan?
Depending on the type of scan you have, you either swallow a small quantity of radionuclide, or it is injected into a vein in your arm. It then takes some time for the radionuclide to travel to the target organ or tissue, and to be ‘taken’ into the active cells. You will not need to remove any of your clothes for the examination, but you will be asked to remove any metal objects as this may interfere with the scan. So, after receiving the radionuclide you may have to wait for a few hours. You may be able to go out and come back to the scanning room later in the day.
When it is time to do the scanning, you lie on a couch while the gamma camera detects the gamma rays coming from your body. The computer turns the information into a picture. You need to lie as still as possible whilst each picture is taken. During the scan you are not shut down in a metal tube.
The number of pictures taken, and the time interval between each picture, varies depending on what is being scanned. Sometimes only one picture is needed. However, for some scans (such as bone scans or heart scans), two or more pictures are needed.
Are there any side effects?
There are no side effects. Radiation received by the human body during a nuclear medicine scan is not dangerous. It is comparatively, less harmful than an ordinary x-ray examination.
Can I continue with my tablets?
Yes. You can continue to take all your tablets or medication as normal. If you have any worries at all please contact your GP.
Can I bring someone with me?
A relative, partner or close friend is welcome to accompany you to your radioisotope scan. Once the test is over you may eat and drink as normal. The procedure will not affect your ability to drive or operate machinery.