A bone scan is a test that can find damage to the bones, find cancer that has spread to the bones, and watch problems such as infection and trauma to the bones. A bone scan can often find a problem days to months earlier than a regular X-ray test.
During a bone scan, a radioactive substance called a tracer is injected into a vein in your arm. The tracer travels through your bloodstream and into your bones. Then a special camera takes pictures of the tracer in your bones.
Areas that absorb little or no amount of tracer appear as dark or "cold" spots. This could show a lack of blood supply to the bone or certain types of cancer.
Areas of fast bone growth or repair absorb more tracer and show up as bright or "hot" spots in the pictures. Hot spots may point to problems such as arthritis, a tumor, a fracture, or an infection.
Why It Is Done
A bone scan is done to:
- Find bone cancer or determine whether cancer from another area, such as the breast, lung, kidney, thyroid gland, or prostate gland, has spread (metastasized) to the bone.
- Help diagnose the cause or location of unexplained bone pain, such as ongoing low back pain. A bone scan may be done first 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.
- Find 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 breastfeeding. The radioactive tracer used in this test can get into your breast milk. Do not breastfeed your baby for 1 or 2 days after this test. During this time, you can give your baby breast milk you stored before the test, or you can give formula. Discard the breast milk you pump in the 1 or 2 days after the test.
- 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.
You will be asked to drink extra fluids after the tracer is injected. You will empty your bladder right before the scan.
You probably will have to wait 1 to 3 hours after the tracer is injected before your bone scan is done. So you may want to bring something to read or a project to pass the time. For some types of bone scans, pictures are taken during the tracer injection, right afterward, and then 3 to 5 hours after the injection.
You may be asked to sign a consent form.
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
You will need to remove any jewelry that might get in the way of the scan. You may need to take off all or most of your clothes. You will be given a cloth or paper covering to use during the test.
Your arm will be cleaned where the tracer will be injected. A small amount of the tracer is injected.
It takes about 2 to 5 hours for the tracer to bind to your bone so that pictures can be taken with a special camera. During this time, you may be asked to drink 4 to 6 glasses of water so your body can wash out the tracer that does not collect in your bones. Just before the scan begins, you will probably 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 a table, with a large scanning camera above you. It may move slowly above, below, and around your body, scanning for radiation released by the tracer and producing pictures. The camera does not produce any radiation.
You may be asked to move into different positions. 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 when the tracer is injected, or you may feel a brief sting or pinch. The bone scan is usually painless. You may find it hard 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.
Allergic reactions to the tracer are very rare.
You may have some soreness or swelling where the needle went in. These symptoms can usually be relieved by applying moist, warm compresses to your arm.
Anytime you're exposed to radiation, there's a small chance of damage to cells or tissue. That's the case even with the low-level radioactive tracer used for this test. But the chance of damage is very low compared with the benefits of the test.
Most of the tracer will leave your body through your urine or stool within a day. So be sure to flush the toilet right after you use it, and wash your hands well with soap and water. The amount of radiation in the tracer is very small. This means it isn't a risk for people to be around you after the test.
The results of a bone scan are usually available within 2 days.
The radioactive tracer is evenly spread among the bones. No areas of too much or too little tracer are seen.
The tracer has accumulated in certain areas of the bone, indicating one or more "hot" spots. Hot spots may be caused by a fracture that is healing, bone cancer, a bone infection (osteomyelitis), arthritis, or a disease of abnormal bone metabolism (such as Paget's disease).
Certain areas of the bone lack the presence of tracer, indicating one or more "cold" spots. Cold spots may be caused by a certain type of cancer (such as multiple myeloma) or lack of blood supply to the bone (bone infarction).
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Pregnancy. A bone scan is not usually done during pregnancy, because the radiation could damage the developing baby (fetus).
- Barium. 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. So bone scan results must be interpreted along with your symptoms and the results of X-ray tests. In addition, other tests such as a CT scan, an MRI, blood tests, or a biopsy may also be needed to further evaluate abnormal bone scan results.
- Some types of cancer or diseases cannot be identified on a bone scan.
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.