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.