A bone scan is an imaging test that shows areas of increased or decreased bone turnover (metabolism).

A bone scan involves injecting a radioactive material (radiotracer) into a vein. The substance travels through the bloodstream. As it 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 and again 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.

A bone scan is used to identify abnormal processes involving the bone such as:

• Bone tumor
• Fracture
• Infection (osteomyelitis)
• Metabolic disorders

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 developing baby to radiation.

The amount of radiation injected into your vein is very small, and nearly all radiation is gone from the body within 2-3 days.

Risks related to the bone radiotracer are rare, but may include:

• Anaphylaxis (severe allergic response)
• Rash
• Swelling

There is a slight risk of infection or bleeding when the needle is inserted into a vein.

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

• Arthritis and other degenerative diseases of the bones
• Avascular necrosis
• Bone infections (osteomyelitis)
• Bone tumors
• Fibrous dysplasia
• Fractures
• Paget's disease
• Radiation changes
• Rickets
• Tumors that have spread from other parts of the body to the bone (metastatic disease)

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