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By Mayo Clinic staffA bone scan falls under the category of nuclear medicine procedures, which means that it uses tiny amounts of radioactive materials called tracers (radionuclides). These tracers accumulate in certain organs and tissues, such as bones. Once introduced into the body, tracers emit a type of radiation called gamma waves, which are detected by a special camera. This camera produces images that are interpreted by radiologists or nuclear medicine specialists.
In a sense, a nuclear procedure such as a bone scan is the opposite of a standard X-ray examination. An X-ray passes radiation into or through your body to create an image on film placed on the other side of your body. In a nuclear scan, the source of radiation is inside your body and travels to the surface, where a camera detects it.
A bone scan can be divided into two basic parts:
- The injection. You will receive an injection of tracers into a vein in your arm, and depending on the reason your doctor orders the scan, images of the injection may be taken immediately. You'll then wait between two and four hours to allow the tracers to circulate and be absorbed by your bones. You may be allowed to leave the radiology department during this time. Your doctor will ask you to drink extra water to remove unabsorbed radioactive material from your system.
- The scan. During the scan, you'll be asked to lie still on a table while a machine with an arm-like device supporting the gamma camera passes over your body to record the pattern of tracer absorption by your bones. This is painless. A scan of your entire skeleton takes as long as 60 minutes. Scanning a limited area of your body takes less time.
In some cases, your doctor might order a three-phase bone scan, which includes a series of images taken at different times. A number of images are taken as the tracer is injected, then shortly after the injection, and again three to four hours later.
For certain conditions your doctor might also order additional images called single-photon emission computerized tomography (SPECT). This can help analyze conditions that are especially deep in your bone or in places that are difficult to see with static or two-dimensional (planar) images. The additional SPECT images take approximately 30 minutes.
After the test
Once inside your body, the tracers don't remain active for long. The radioactivity is eliminated within two days. You should feel no side effects after the procedure, and no aftercare is necessary.