A bone scan is a test that detects areas of increased or decreased bone metabolism (turnover). The test is performed to identify abnormal processes involving the bone such as tumor, infection, or fracture.

A radiotracer (bone-seeking radionuclide) is injected into the bloodstream through a vein. As it decays, the radiotracer emits gamma radiation, which is detected by a camera that slowly scans your body. The camera captures images of how much radiotracer collects in the bones.

If a bone scan is performed to evaluate possible fracture or infection, images will be performed shortly after the radiotracer injection, as well as after a 3-hour delay, when the tracer has collected in the bones. This is called a 3-phase bone scan.

To evaluate metastatic bone disease, images are obtained only after the 3-hour delay. Information from the camera is recorded in a computer, which then processes the data and creates an image.

The scanning part of the test will last about an hour and may require moving to various positions.

You must remove jewelry and other metal objects. You may be asked to wear a hospital gown.

There is a small amount of pain when the needle is inserted. During the scan there is no pain. You must remain still during the examination, and you will be instructed when to change positions by the technologist.

You may experience some discomfort due to lying still for a prolonged period of time.

Detecting areas of abnormal bone metabolism is valuable in determining whether there is associated tumor, fracture, infection (osteomyelitis), or an underlying metabolic disorder.

Normal distribution areas appear uniform and gray throughout all the bones in your body.

There should be no areas of asymmetric increased or decreased distribution of the radionuclide. "Hot spots" are areas where there is increased bone uptake (accumulation) of the radiotracer; these appear black. "Cold spots" are areas where there is less uptake of the radiotracer. These appear light or white.

If you are pregnant or nursing, the test may be postponed to prevent exposing the fetus to radiation.

The amount of radioactivity in the injection is very small, and virtually all activity is gone from the body within 2-3 days. Although it is extremely rare with bone scanning agents, a person may develop rash, swelling, or anaphylaxis (severe allergic response).

There is a slight risk of infection or bleeding with any intravenous injection.

Some abnormalities that may be identified on radionuclide bone scans include:

• Tumors that have spread from other parts of the body to the bone (metastatic disease)
• Primary bone tumors
• Fractures
• Bone infections (osteomyelitis)
• Degenerative diseases of the bones, such as arthritis
• Rickets
• Fibrous dysplasia
• Paget's disease
• Avascular necrosis
• Radiation changes

It is important to understand that bone scan findings must be correlated with other imaging studies, in addition to clinical information. You should always discuss the significance of abnormal findings with your health care provider.