Bone scan
A bone scan is a 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).
During a bone scan, a small amount of radioactive substance (radionuclide) is injected into the bloodstream. A camera takes pictures of the location of the radioactive substance in the bone. 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 abnormal bone collect a lot of the radioactive substance and show up as "hot" spots on the picture. Hot spots may mean problems such as arthritis, a tumor, a fracture, or an infection. A bone scan can often detect a problem days to months earlier than a regular X-ray test.
Why is a bone scan 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 is a bone scan 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.
How do you prepare for a bone scan?
If you are breastfeeding, you may want to pump enough breast milk before the test to get through 1 to 2 days of feeding. The radioactive tracer used in this test can get into your breast milk and is not good for the baby.
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.
What do the results of a bone scan mean?
The results of a bone scan are usually available within 2 days.
Normal: | The radioactive tracer is evenly spread among the bones. No areas of too much or too little tracer are seen. |
|---|---|
Abnormal: | The tracer collects in certain areas of the bone, showing 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, showing 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). |
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