Gallium Scan

A gallium scan is a nuclear medicine test that uses a special camera to take pictures of specific tissues in the body after a radioactive tracer (radionuclide or radioisotope) makes them visible. Each type of tissue that may be scanned (including bones, organs, glands, and blood vessels) uses a different radioactive compound as a tracer. The radioactivity of different tracers decreases over a period of usually hours, days, or weeks. The tracer remains in the body temporarily before it is eliminated as waste, usually in the urine or stool (feces).

During a gallium scan, the tracer (radioactive gallium citrate) is injected into a vein in the arm. It travels through the bloodstream and into the body's tissues, primarily the bones, liver, intestine, and areas of tissue where inflammation or a buildup of white blood cells (WBCs) is present. It usually takes the tracer a few days to accumulate in these areas, so in most cases a scan is done at 2 days and repeated at 3 days after the tracer is injected. Areas where the tracer accumulates in higher-than-normal amounts show up as bright or "hot" spots in the pictures. The problem areas may be caused by infection, certain inflammatory diseases, or a tumor.

A gallium scan is done to:

• Detect the source of an infection that is causing a fever (called a fever of unknown origin).
• Detect 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 determine whether cancer has spread (metastasized) to other areas of the body, or to monitor the effectiveness of cancer treatment.

Before the gallium scan, tell your doctor if:

• You are or might be pregnant.
• You are breast-feeding. If you will no longer be breast-feeding after the test, you will be asked to stop breast-feeding 2 weeks before the test so that the radioactive tracer will not accumulate in your breast tissue. If you will continue to breast-feed after the test, it is recommended that you not use your breast milk for 4 weeks after a gallium scan, since the tracer can be passed to your baby. Some doctors may recommend that you stop breast-feeding completely after this scan.
• Within the past 4 days, you have had an X-ray test using barium contrast material (such as a barium enema) or have taken a medicine (such as Pepto-Bismol) that contains bismuth. Barium and bismuth can interfere with test results.

Gallium accumulates in the large intestine (colon) before being eliminated in the stool. You may need to take a laxative the night before the scan and have an enema 1 to 2 hours before the scan to prevent the gallium in your colon from interfering with pictures of the area being studied.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

A gallium scan is usually done by a nuclear medicine technologist. The scan pictures are usually interpreted by a radiologist or nuclear medicine specialist.

The technologist cleans the site on your arm where the radioactive tracer will be injected. A small amount of the radioactive tracer is then injected. You will need to return between 24 and 96 hours later for the diagnostic scans. Gallium scans are usually done at 48 hours and repeated at 72 hours after the tracer is injected.

When you come in for the scan, you will need to remove any jewelry that might interfere with the scan. You may need to take off all or most of your clothes, depending on which area is being examined (you may be allowed to keep on your underwear if it does not interfere with the test). You will be given a cloth or paper covering to use during the test.

You will lie on your back on a table, and a large scanning camera will be positioned closely above you. After the radioactive tracer is injected, the camera will scan for radiation released by the tracer and produce pictures of the tracer in your tissues. The camera may move slowly above and around your body. The camera does not produce any radiation, so you are not exposed to any additional radiation while the scan is being done.

You may be asked to move into different positions so the area of interest can be viewed from other angles. You need to lie very still during each scan to avoid blurring the pictures. You may be asked to hold your breath briefly during some of the scans.

Each scan may take about 60 to 90 minutes.

You may feel nothing at all from the needle puncture when the tracer is injected, or you may feel a brief sting or pinch as the needle goes through the skin. Otherwise, a gallium scan is usually painless. You may find it difficult to remain still during the scan. Ask for a pillow or blanket to make yourself as comfortable as possible before the scan begins.

There is always a slight risk of damage to cells or tissue from being exposed to any radiation, including the low level of radiation released by the radioactive tracer used for this test.

Allergic reactions to the radioactive tracer are rare. Most of the tracer will be eliminated from your body (through your urine or stool) within 4 days. The amount of radiation is so small that it is not a risk for people to come in contact with you following the test.

Occasionally, some soreness or swelling may develop at the injection site. These symptoms can usually be relieved by applying moist, warm compresses to your arm.

A gallium scan is a nuclear medicine test that uses a special camera to take pictures of certain tissues in the body after a radioactive tracer (radionuclide or radioisotope) makes them visible. The results of a gallium scan are usually available within 2 days after the scans are completed.

Factors that can interfere with your test and the accuracy of the results include:

• Pregnancy. A gallium scan is not usually done during pregnancy because the radiation could damage the developing baby (fetus).
• Barium and bismuth. If a gallium scan is needed, it should be done before any tests that use barium (such as a barium enema).
• The inability to remain still during the test.

• A gallium scan is used for specific types of cancers, mainly of the lymph nodes, bones, or bone marrow. A normal scan does not exclude the possibility of cancer, because some types of cancer do not show up on a gallium scan. A gallium scan also cannot determine whether a tumor is cancerous (malignant) or noncancerous (benign).
• The results of a gallium scan should be interpreted along with the results of other tests, such as a physical examination, blood tests, and X-rays. In many cases, results obtained from a magnetic resonance imaging (MRI) or positron emission tomography (PET) may be as accurate as the results obtained from a gallium scan. For more information, see the medical tests Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET).
• If other nuclear scanning tests need to be done, these tests should be scheduled before a gallium scan because the gallium tracer stays in the body longer than other tracer compounds.

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.