by Dr. Gary Farr on 22 April 2002
What is a Bone Scan?
A bone scan is sometimes performed to rule out an inflammatory process (such as a tumor or infection) or an occult fracture (small fracture not seen on an x-ray).
A bone scan is performed by injecting a small amount of radioactive marker into an intravenous line (IV). Three hours later the patient is placed through a scanner and the radioactive marker will be concentrated in any region where there is high bone turnover.
A bone scan is a highly sensitive test to pick up tumors, infections, or very small fractures because these conditions all result in high bone turnover. It can also be used to determine if a compression fracture of the vertebral body is old or new, as an old fracture will not light up and a new one will.
Bone scans, however, cannot distinguish what a lesion represents, and therefore cannot differentiate between a tumor, an infection or a fracture. Therefore, this type of imaging study usually needs to be followed by a CT scan and/or MRI scan to better characterize the lesion.
The results of the test reveal 'hot' and 'cold' spots. Hot spots appear darker on the image and denote an area of high tracer uptake, possibly indicating an abnormality (e.g. infection). Cold spots appear light and indicate the bone absorbed less of the tracing element. 
In many departments, the bone scan is one of the most commonly performed nuclear medicine diagnostic procedure. X-rays, CT scans and MRI examinations evaluate the structure of the bone. In contrast, a bone scan evaluates the functional aspect of the bone diseases. This is very useful in the early diagnosis of a stress fracture when the changes in bone architecture have not taken place yet, but the bone scan is frequently abnormal at that stage. This provides the physician an opportunity to make the diagnosis early, thereby expediting treatment.
When is a bone scan useful?
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There are a variety of situations when a bone scan would be useful. These include but are not limited to,
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Diagnosis of bone infection, known as osteomyelitis.
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Diagnosis of stress injuries, such as a stress fracture and shin splints.
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In patients with cancer, to determine whether the cancer has spread to the bone or not. Therapeutic options in these patients are often determined by whether or not the cancer has involved the bones. Bone scanning is particularly useful because it is possible to evaluate the entire skeleton with a single examination.
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In the evaluation of unexplained bone pain.
How long does it take to perform a bone scan?
When you come to nuclear medicine department, you will receive an injection of a radioactive compound (such as Technetium-99m MDP or Technetium-99m HDP). In certain situations (such as for diagnosis of osteomyelitis), imaging is performed at the time of injection. Otherwise, you can leave the department soon after the injection, and you will be asked to return two hours later for imaging. This is done to allow time for the injected compound to localize in the bones. Depending on the type of information desired, it takes 30 to 90 minutes to perform the scan. When you come to the department you will be provided with the information that will include, based on the information desired by your referring physician, an estimate of how long it will take to perform the scan.
While performing the bone scan, side effects are not common, and when encountered are usually mild, such as nausea and vomiting. If you are pregnant, suspect you may be, or are a nursing mother, please discuss this with your physician before scheduling the test.
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How does a patient prepare for Bone scanning, and how is it performed? |
There is no preparation prior to a bone scan. If you are taking any medications routinely, you can continue to do so on the day of the bone scan procedure. Unless you are having another procedure that requires you to avoid food, you can have your regular meals before coming to the department. You will be encouraged to drink plenty of fluids (water, soft drinks, juices etc) between the time of injection and the scan which typically will be performed 2-3 hours later. You will also be asked to empty your bladder frequently.
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