A bone scan is a test in which a radioactive material, called a “tracer,” is injected into a patient’s blood stream, where it will bind to bones. Once the tracer is absorbed, a special camera known as a “gamma” is used to take pictures of the bones. The test shows areas of new or rapid bone growth, which is usually indicative of a problem in adults.
Bone scans capture pictures of the entire skeleton, which makes them useful when physicians aren’t quite sure where the problem is located. Bone scans do not capture images of soft tissue, so they are not a good tool for evaluating if the patient has pinched nerves, sciatica, prolapsed discs or a degenerative spine. Instead, physicians use bone scans to rule out small fractures, bone cancer or infection. A bone scan may also be helpful in detecting facet disease or osteoarthritis.
Bone scan procedure
If your physician orders a bone scan, the first thing you’ll want to do is tell him or her if you are pregnant or breast-feeding, as the radioactive material injected during the tests can interfere with these conditions. You should also tell the physician if you have recently taken Pepto-Bismol or another substance that contains bismuth, or if you’ve recently had any kind of test involving a barium contrast (such as a barium enema). This is because these substances can create inaccurate test results.
When you arrive for your test procedure, you’ll be injected with a small amount of the radioactive tracer. Sometimes, a picture will be taken right away, but only in certain cases. Whether an initial picture is taken at the time of injection or not, you’ll need to wait two to three hours for the tracer to be fully absorbed into your bones. During this time, you’ll be asked to drink lots of water and urinate as much as possible. This helps flush any excess tracer fluid out of your body as quickly as possible. Right before the imaging begins, you’ll be asked to empty your bladder a final time.
Before the images are taken, you’ll be asked to remove jewelry, dentures and most of your clothes. You’ll be given a cloth to cover yourself during the test. Since the test requires you to lie as still as possible, you may also wish to request a pillow to make yourself comfortable. Once you are lying on the table, the camera is positioned over you, attached to an arm that moves the camera around. The camera does not emit any radiation of its own; it simply reads the radiation given off by the tracer material in your bones. The scan takes about an hour and is completely painless.
After the test is complete, you’ll be allowed to go home. The radioactive tracer will be completely eliminated from your body within two days.
What the bone scan shows
The tracer material is brought into your bones through blood flow. Therefore, areas with lots of blood flow absorb lots of the tracer, resulting in dark “hot spots” on the scan. Areas with little or no blood flow, on the other hand, look very light on the scan due to low absorption of the tracer.
Low blood flow can indicate a blockage from a tumor or other obstruction. Areas of very high blood flow tend to be areas where lots of growth is taking place, which could mean cancer or some other disorder. However, the scan itself cannot distinguish healthy growth from abnormal growth, so other tests, such as a CT scans, dermatome maps, an X-ray, or MRI scan will likely be ordered if the bone scan results are abnormal.