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A gallium scan is a special type of imaging study, or x-ray test. The test involves injecting a radioactive material called gallium into the bloodstream. Special x-ray cameras can then take pictures of the gallium inside the body.

Gallium is preferentially taken up by neutrophils, macrophages, bacteria and some tumors. It is useful in identification of infection and tumors.

Who is a candidate for the test?

A gallium scan is usually used to look for an infection or cancer. In most cases, this test is used because blood tests or regular x-rays are abnormal or unclear.

Common candidates for a gallium scan include:

• someone who has had a fever for a long time without a known cause, also called a fever of unknown origin. In this case, the gallium scan is used to locate a small area of infection or cancer that has not yet been detected.
• a person suspected of having a bone infection, also called osteomyelitis
• someone with suspected lung disease. For instance, sarcoidosis is a condition that occurs for unknown reasons. This condition can cause inflammation in the lungs that can be detected with a gallium scan. Lung infections, such as pneumonia, can also be detected by a gallium scan.
• an individual with known cancer, usually a blood cancer called lymphoma

How is the test performed?

To perform this test, gallium must be injected into a person's vein. Usually, an intravenous line (IV) is placed to make the injection easier. An IV is a thin tube that is inserted through the skin and into a vein, usually in the hand or forearm. Once the IV is in place, the gallium is injected through the IV tube.

After the injection, a waiting period is needed to allow the gallium time to concentrate in any abnormal areas before the x-ray pictures are taken. This waiting period may range from 4 to 72 hours, depending on the suspected condition.

The person having the test can go home, or back to the hospital room if in the hospital, and return at the given time. Gallium does not produce discomfort. Once the waiting time is over, a special x-ray camera is used to take pictures. This camera detects the gallium inside the person's body. The pictures do not hurt; however, the person must hold still while the pictures are taken.

After the pictures are taken, which usually takes about 30 minutes, the test is over. In many cases, more than one set of pictures must be taken at different times, sometimes a full day apart. A person will be informed if this is required.

What is involved in preparation for the test?

Normally, no special preparation is required. Jewelry and other items that may interfere with the pictures must be removed. In some cases, a person will be asked to take a laxative or have an enema to clean out the bowels before the test. Any woman who is or may be pregnant or is breastfeeding should tell the x-ray staff. This is because the gallium is radioactive and could harm an unborn or breastfeeding child.

What do the test results mean?

• an infection
• an active disease causing inflammation, such as sarcoidosis in the lungs
• a cancer, such as the blood cancer lymphoma

The healthcare professional who ordered the test will discuss the results and what they mean.