Bone scan is a nuclear medicine test done to evaluate cancer, infections, arthritis and other conditions throughout the skeleton. The test images the entire skeleton. The test involves the injection of tiny amounts of radioactive materials into your vein. This is followed by imaging with a camera 2-4 hours later.
The test is painless and no special preparation is needed. There are no complications and the radioactive material is eliminated in the days after the test. The test is usually not done on pregnant patients because of radiation exposure concerns.
The injected radiopharmaceutical is usually Tc 99m methylene diphosphonate. The radiopharmaceutical binds to areas of bone that have increased blood flow and bone turnover. Common reasons for bone scans include cancer, arthritis, infections, bone lesions amongst others. The test is performed by a technician and read by a radiology doctor.
The most common reason I see in practice is determining the extent of cancer spread to the bones, response after cancer treatment and to monitor cancer progression. Cancer to the bones most commonly looks like a hot spot. Bone scan is good at telling us where bone turnover is high by showing us a hot spot. However, there are many abnormalities that can cause high bone turnover in addition to cancer.
Treatment response following chemotherapy for cancer is another indication for bone scan. These patients are followed to see if the spread of cancer to the bones is responding to the treatment. Some cancers like multiple myeloma are not as good for diagnosing and monitoring with bone scan. Others like prostate cancer are followed routinely.
Other indications I see are for imaging arthritis. This is to see the extent of arthritis throughout the body. Arthritis will look like hot spots around the joints. The type of arthritis will need to be imaged further with x rays. Infections are imaged with bone scans, but these indications usually require more phases of imaging (triple phase bone scan).
Bone scan is a very sensitive test for detecting abnormalities. Many abnormalities will show up as hot spots. Unfortunately, the test is not very good at telling us what the abnormalities are. You may need additional imaging for any abnormalities detected. X-ray, CT or MRI may be needed following identification of an abnormality.
Bone scan is a fairly quick time proven way to image the entire skeleton. It is painless and has no complications. Most commonly, I see this test being done for cancer. There are many less commonly performed indications as well. Your clinical doctor will often correlate the results of the test with his findings to arrive at the best diagnosis and treatment.