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 (a bone-seeking radioactive material) is injected into vein, so it travels through the bloodstream. As the material wears away, it gives off radiation. This radiation is detected by a camera that slowly scans your body. The camera takes pictures of how much radiotracer collects in the bones.

If a bone scan is done to see if you have a bone infection, images will be taken shortly after the radioactive material is injected, as well as 3 to 4 hours later, when it has collected in the bones. This is called a 3-phase bone scan.

To evaluate metastatic bone disease, images are taken only after the 3 to 4 hour delay.

The scanning part of the test will last about 1 hour and may require you to change 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.

This test can help determine whether there is bone tumor, fracture, infection (osteomyelitis), or metabolic disorder.

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

The images should show that the radioactive material has been evenly distributed throughout the body. There should be no areas of increased or decreased distribution. "Hot spots" are areas where there is an increased accumulation of the radioactive material. "Cold spots" are areas that have taken up less of the radioactive material.

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.