Note: the information below is a general guide only. The arrangements, and the way tests are performed, may vary between different hospitals. Always follow the instructions given by your doctor or local hospital.
What is a gallium scan?
A gallium scan is a type of radionuclide or isotope scan. In a gallium scan a tiny amount of radionuclide is put into the body, by an injection into a vein. The radionuclide is a chemical which emits a type of radioactivity called gamma rays. The gamma rays are detected by a special camera. The camera creates pictures of specific tissues in the body after the radionuclide makes them visible. For more information on radionuclide scans see separate leaflet called ‘Radionuclide Scan’).
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. The body treats gallium a bit like iron. This means it tends to concentrate in areas where there is inflammation, infection or rapid cell division. Rapid cell division can sometimes be an indication of cancer.
How does a gallium scan work?
The first part of the test involves an injection of a chemical called gallium citrate into the bloodstream. Gallium citrate behaves rather like iron and some of it attaches to proteins in your blood, particularly to the protein called transferrin. It then circulates around your body with your blood, and begins to collect in different parts of your body. The gallium will naturally concentrate in areas where there is inflammation or where white blood cells have collected. It can take several days for the gallium to build up, which is why the second part of the scan is done a few days later.
Gallium emits gamma rays, a type of radioactive wave. Gamma rays are similar to X-rays and are detected by a device called a gamma camera. 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 colours or shades of grey.
For example, areas of the target organ or tissue which emit lots of gamma rays may be shown as red spots (‘hot spots’) on the picture on the computer monitor. Areas which emit low levels of gamma rays may be shown as blue (‘cold spots’). Various other colours may be used for in between levels of gamma rays emitted.
What happens during a gallium scan?
The test is normally done in two parts. In the first part you will receive an injection of the gallium citrate, usually into your arm. This may be a little uncomfortable as the needle is inserted but after that you will normally feel no effects. Usually, you can go home after the injection to allow the gallium to work its way around your body.
The second part of the test involves coming back to hospital for the scan. Depending on your hospital, and the reason for doing the test, you may be asked to return for the scans to be done one day, two days, or three days after the injection.
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 (so it is not blurred). Some pictures can take 20 minutes or more to expose. The camera does not produce any radiation, so you are not exposed to any additional radiation while the scan is being done.
The number of pictures taken, and the time interval between each picture, varies depending on what is being scanned. So, the whole process can take several hours.
What is a gallium scan used for?
A gallium scan can be used to:
- Detect the source of an infection that is causing a fever (called a fever of unknown origin).
- Find an abscess or certain infections, especially in the bones.
- Monitor the response to antibiotic treatment.
- Diagnose inflammatory conditions such as pulmonary fibrosis or sarcoidosis.
- Detect certain types of cancer (such as lymphoma). A gallium scan also may be done to see if cancer has spread (metastasised) to other areas of the body, or to watch how well a cancer treatment is working.
What should I do to prepare for a gallium scan?
Usually very little. Your local hospital should give you information to help you prepare for the test. As a gallium scan involves a small amount of radiation, pregnant women should not have it done. 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. You may be asked to stop breast-feeding for a certain length of time before and after the test.
If pictures of your abdomen (tummy) are needed you may be given some laxative tablets before the scan. These tablets will make you go the toilet. This helps to make the pictures clearer. If you need these tablets you will be given them by hospital staff. You will also be given advice about when to take them.
What can I expect after a gallium scan?
Radionuclide scans such as a gallium scan do not generally cause any after-effects. Through the natural process of radioactive decay, the small amount of radioactive chemical in your body will lose its radioactivity over time. It may also pass out of your body through your urine or stool (faeces) during the first few hours or days following the test. You may be instructed to take special precautions when urinating, to flush the toilet twice and to wash your hands thoroughly.
If you have contact with children or pregnant women you should let your doctor know. Although the levels of radiation used in the scan are small, your doctor may advise special precautions. Your hospital should give you more advice on this.
If you are travelling abroad in the three months after your scan, ask your doctor for further advice. Ports and airports have very sensitive radiation detectors which may pick up tiny amounts of radioactivity remaining after your scan. Usually, it is possible for your hospital to provide you with a letter that you can show to officials at ports or airports.
Are there any side-effects or complications from a gallium scan?
The term ‘radioactivity’ may sound alarming. But, the radioactive chemicals used in radionuclide scans such as a gallium scan are considered to be safe, and they leave the body quickly in the urine. The dose of radiation that your body receives is very small. In many cases, the level of radiation involved is not much different to a series of a few normal X-rays. However:
- As with any other types of radiation (such as X-ray), there is a small risk that the gamma rays may affect an unborn child. So, tell your doctor if you are pregnant or if you may be pregnant.
- Rarely, some people have an allergic reaction to the injected chemical.
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