A bone scan is an imaging test that safely uses a very small amount of radioactive dye to help diagnose problems with your bones.
This test reveals problems with bone metabolism. The normal process of bone metabolism includes how bones are broken down and how they rebuild themselves. Bone metabolism also involves the bone’s response to fractures, infections, bone cancer, and cancer that has spread to the bone from other areas of the body (metastatic cancer).
Your bones are living organs. Bones provide structure for the body and protect the organs of the body. The bones of the body can be injured or broken and new bone formation is part of the healing process.
Some bones (mainly flat ones) house bone marrow. Bone marrow is the spongy material that is responsible for the production of red blood cells, white blood cells, and platelets. Red blood cells carry oxygen to all parts of the body, white blood cells help the body fight infections, and platelets assist in blood clotting.
The bone scan is a good method of viewing and documenting abnormal metabolic activity in the bony structure of the body.
During your bone scan, a radioactive dye will be injected and then you will be monitored for several hours. Don’t worry though—the amount of radiation used in the dye is very small and nearly all of it is released from the body within two to three days.
Your doctor may order a bone scan if he or she suspects you could have a condition that affects your bones, such as a cancer, infection, or fracture. It can also help your doctor find the cause of any unexplained bone pain you may be having.
According to the Mayo Clinic, bone scans can reveal bone problems associated with the following conditions:
- avascular necrosis (or impaired blood supply to the bone which can result in death of the bone)
- bone cancers
- cancer that has spread to the bone from other body organs or tissue
- fibrous dysplasia (a condition where bones becomes thin)
- Paget’s disease of the bone (a disease that has an abnormal amount of bone breakdown and repair leading to bone deformities)
A bone scan carries no more risk than conventional X-rays. The tracers in the radioactive dye used in a bone scan produce very little radiation exposure. Even the risk of allergic reaction to the tracers is low.
You may feel a slight discomfort at the injection site and sitting still during the test can be uncomfortable for some people.
The greater risk is to pregnant or nursing women. Tell your doctor if you are pregnant, believe you could be pregnant, or are nursing a newborn. You may need to wait to have the test.
A bone scan requires no special preparation. Immediately before the scan, your doctor will ask you to take off any metal jewelry and remove any body piercings you might have.
The actual screening procedure takes about an hour. If you think you’ll have problems sitting for that extended period of time, your doctor may give you a mild sedative to help you relax.
The procedure begins with an injection of radioactive dye in your arm. The dye is then allowed to work its way through the body for the next two to four hours. Depending on the reason for the bone scan, your doctor may begin imaging immediately.
While the dye works through your body, you may be free to leave the radiology department. Your doctor will recommend you drink plenty of fluids during this time.
The dye finds spots in the bone that are damaged because the bone’s cells naturally gravitate to areas that need repair. This is the bones’ attempt to fix the problems on their own. The dye’s radioactive tracers follow these cells.
After enough time has passed, the technician will use a special camera to scan the bones. The damaged areas—where the dye has gravitated—appear as dark spots on the imaging.
Your doctor may repeat the injection and imaging process if the first round was not conclusive. He or she may also order a single-photon emission computed tomography (SPECT). This is similar to a bone scan, except the imaging process creates 3-D images of your bones. This would be necessary if your doctor needs to see deeper into your bones or for places that are not very clear in two-dimensional images.
There are no side effects from bone scans or precautions to take after the procedure. Most of the radioactive tracer is eliminated from your body within 24 hours but small amounts remain for as long as three days.
While the test can help find problems in bone metabolism, it doesn’t necessarily uncover the reason for them. If there were any abnormalities, you may have to undergo more tests to determine their cause. Your doctor will explain your options and help guide you through the process.