A bone scan is a test to help find the cause of your back pain. It can be done to find damage to the bones, find cancer that has spread to the bones, and watch problems such as infection and trauma to the bones. A bone scan can often find a problem days to months earlier than a regular X-ray test.

For a bone scan, a radioactive substance is injected into a vein in your arm. This substance, called a tracer, travels through your bloodstream and into your bones. This could take several hours.

A special camera takes pictures of the tracer in your bones. 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 fast bone growth or repair absorb more tracer and show up as bright or "hot" spots in the pictures. Hot spots may point to problems such as arthritis, a tumor, a fracture, or an infection.

Why It Is Done

A bone scan is done to:

• Find bone cancer or 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 a picture 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 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.