Before the test, patients may be required to remove their clothing and wear an examination gown. All jewelry and other metallic objects must be removed so they do not interfere with the test. Pregnant women should inform physicians of their condition prior to the test because it may be harmful due to radiation exposure to the unborn child.

Patients may wish to limit fluid intake or urinate prior to the bone scan because they will be required to drink fluids during the test. Patients may be required to sign a consent form before the test can be performed.

A bone scan is usually performed by a nuclear medicine technologist in the radiology department of a hospital or an outpatient x-ray center. The patient usually sits or lies down while a radioactive substance (called a radiotracer or bone–seeking radionuclide) is injected through a vein in the arm. The amount injected is small and is not harmful to the patient.

For most bone scans, a patient must wait between three and four hours after the injection to allow the radionuclides to circulate through the body. During this time, the individual drinks several glasses of water to urinate frequently, which removes unabsorbed radioactive material from the body. The patient is permitted to move about freely during the waiting period.

Before the scan, the patient is instructed to urinate to ensure that the radioactive substance is not concentrated in the bladder. The individual lies on the back and may be repositioned to the side or stomach during the test. It is important for the patient to remain still during the procedure unless instructed to move.

During the scan, a machine with an arm–like device supporting the gamma camera passes over the body and records images of the radioactive material absorbed in the bones. This procedure does not cause discomfort and usually lasts between 30 and 60 minutes.

Sometimes a specific type of bone scan, called a triple–phase or three–stage bone scan, is performed. During this procedure, the scanning is performed at different times after the radioactive material is injected into the body. For instance, scanning may occur immediately after the injection, 20 minutes after injection and then two to four hours later.

In some cases, a type of radionuclide imaging scan called single-photon emission computed tomography (SPECT) may be performed to study a particular part of the body, such as the hips, lower back or jaw. This test may help a physician identify a problem more accurately.

After the test is completed, patients are instructed to drink plenty of fluids to ensure that any remaining radioactive substance exits the body. Radioactivity usually disappears within one to three days. Patients should not experience discomfort after the test. Women who are breastfeeding may be required to avoid nursing for 24 hours after the test.

The results of the scan are usually available within a few days or weeks. In general, the scan may reveal:

• Normal distribution. Areas where the radioactive substance has been distributed normally will appear uniform and gray throughout all the bones in the body.
  
  
• Hot spots. Areas where there is increased accumulation of the radioactive substance appear black on the scan. Hot spots may be caused by a fracture, bone cancer, infection, arthritis or other diseases such as Paget’s disease.
  
  
• Cold spots. Areas where there is a lack of radioactive substance appear light or white on the scan. Cold spots may be caused by a certain type of cancer (multiple myeloma) or lack of blood supply to the bone.