Test Overview

A bone scan is a nuclear scanning test that identifies new areas of bone growth or breakdown. It can be done to evaluate damage to the bones, detect cancer that has spread (metastasized) to the bones, and monitor conditions that can affect the bones (including infection and trauma). A bone scan can often detect a problem days to months earlier than a regular X-ray test.

For a bone scan, a radioactive tracer substance is injected into a vein in the arm. The tracer then travels through the bloodstream and into the bones. A special camera (gamma) takes pictures of the tracer in the bones. This helps show cell activity and function in the bones. Areas that absorb little or no amount of tracer appear as dark or "cold" spots, which may indicate a lack of blood supply to the bone (bone infarction) or the presence of certain types of cancer. Areas of rapid bone growth or repair absorb increased amounts of the tracer and show up as bright or "hot" spots in the pictures. Hot spots may indicate the presence of a tumor, a fracture, or an infection.

A bone scan may be done on the entire body or just a part of it.

Why It Is Done

A bone scan is done to:

• Determine whether a cancer from another area, such as the breast, lung, kidney, thyroid gland, or prostate gland, has spread (metastasized) to the bone. See an illustration of a bone scan showing the spread of cancer.
• Help diagnose the cause or location of unexplained bone pain, such as ongoing low back pain. A bone scan may be done initially to help determine the location of an abnormal bone in complex bone structures such as the foot or spine. Follow-up evaluation then may be done with a computed tomography (CT) scan or magnetic resonance imaging (MRI).
• Help diagnose broken bones, such as a hip fracture or a stress fracture, not clearly seen on X-ray.
• Detect damage to the bones caused by infection or other conditions, such as Paget's disease.

How To Prepare

Before the bone scan, tell your doctor if you:

• Are or might be pregnant.
• You are breast-feeding. Use formula (discard your breast milk) for 1 to 2 days after the scan until the radioactive tracer has been eliminated from your body.
• 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 medication (such as Pepto-Bismol) that contains bismuth. Barium and bismuth can interfere with test results.

You may wish to limit your fluids for up to 4 hours before the test because you will be asked to drink extra fluids after the radioactive tracer is injected. You will empty your bladder right before the scan.

You usually have to wait 1 to 3 hours after the radioactive tracer is injected before your bone scan is done. Therefore, you may want to bring some reading materials or a project to pass the time during this waiting period. For some types of bone scans, pictures are taken during the tracer injection, immediately afterward, and then 3 to 5 hours after the injection.

You may be asked to sign a consent form before the test. 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 mean. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?) .

How It Is Done

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

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.

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.

It takes 1 to 3 hours for the tracer to have enough tracer in lthem for pictures to be taken with the gamma camera. During this time you may be asked to drink 4 to 6 glasses of water to help eliminate in your urine any of the radioactive substance that does not collect in your bones. Just before the scan begins, you will usually be asked to empty your bladder to prevent any radioactive urine from blocking the view of your pelvic bones during the scan.

You will lie on your back on a table and a large scanning camera will be positioned closely above you. It may move slowly above and around your body, scanning for radiation released by the tracer and producing pictures as the tracer moves into your bones. 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.

A bone scan takes about 1 hour.

How It Feels

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 bone 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.

The test may be uncomfortable if you are having joint or bone pain. Try to relax by breathing slowly and deeply.

Risks

Allergic reactions to the radioactive tracer are rare. Most of the tracer will be eliminated from your body (through your urine or stool) within a day, so be sure to promptly flush the toilet and thoroughly wash your hands with soap and water. 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.

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.

Results

A bone scan is a nuclear scanning test that identifies new areas of bone growth or breakdown. The results of a bone scan are usually available within 2 days.

What Affects the Test

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

• Pregnancy. A bone scan is not usually done during pregnancy because the radiation could damage the developing baby (fetus).
• Barium and bismuth. If a bone 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 full bladder, which can block the view of the pelvic bones.

What To Think About

• A bone scan does not distinguish between normal and abnormal bone growth by itself. Therefore, bone scan results must be interpreted along with your symptoms and the results of X-ray tests. In addition, other tests, such as computed tomography (CT), magnetic resonance imaging (MRI), blood tests, or a biopsies may also be needed to further evaluate abnormal bone scan results.
• Some types of cancer or diseases cannot be identified on a bone scan.

References

Other Works Consulted

• 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.

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