A bone scan, also known as bone scintigraphy, is a non-invasive nuclear medicine test used to evaluate the entire skeleton for abnormalities in the bones.
The most basic radiology test to assess the health of bones is the X-Ray; however, with infections and cancer, it is often useful to obtain "functional imaging" to evaluate the bones. Functional imaging can measure the rate of bone metabolism, which can be elevated with infections, fractures, and certain cancers. It is important to understand that without talking to the patient and knowing the medical history, the results of a bone scan can be very difficult to interpret. For example, old bone injuries can show up on the scan as an abnormal finding.
What is this test used for?
Bones scans are a type of nuclear medicine scan, meaning a scan that uses a radioactive substance to diagnose or evaluate the body.
Bone scans should not be confused with a DEXA, or bone density, scan, which is a type of X-ray used to detect osteoporosis.
A bone scan can evaluate the rate of metabolism of bones throughout the body. In infections, fractures, and cancer, as the body attempts to repair the problem, osteoblasts create more bone; it is this new bone activity that is detected on the bone scan.
A bone scan may be used when cancer is first diagnosed to determine if the cancer has spread to the bone.
How is this test performed?
Bone scans are generally an outpatient procedure. An intravenous line is placed and an injection of a radioactive material, typically Technitium-99m-MDP, is given. The injection of the material does not hurt and the amount of radiation is very small.
Bone scans detect the rate of bone deposition by osteoblasts because they take up the radioactive material that is injected.
Two to three hours after the infusion is given, a scan is performed.
The scanner is a special type of camera that detects gamma rays, which are a type of radiation emitted by the injection. Bone fractures, bone infections, and cancer in bones all show up as increased activity in the bones.
During the scan, the patient will lie on a flat table. The scan will evaluate the whole body of the patient at once, which can take up to an hour.
An image is created based on how many Gamma rays reach the detector. The computer then processes this to create a picture of the patient. Any areas with increased bone activity show up as a dark spot on the image (see example below).
If you are pregnant or nursing, you should notify your doctor prior to the scan.
Example of a bone scan result. Multiple areas of concern are seen in this patient's bones.
How do I prepare for a bone scan?
Typically, no preparation is needed.
How do I interpret the results of a bone scan report?
Following the scan, the images are processed by a computer and read by a nuclear medicine radiologist. The radiologist then generates a report for the medical professional that ordered the scan.
The report generally states the patient's name, date of birth, and indication (reason for the bone scan) at the top of the report. Radiology reports follow a standard outline, regardless of where they are obtained. Radiologists report both normal and abnormal findings in a very systematic approach. For this reason, it is very important to discuss the results with your doctor.
The first paragraph typically includes the specific technical information involved in obtaining the scan (i.e. how much Technitium was given, whether the whole body was scanned, etc).
The middle paragraphs generally describe the findings, both normal and abnormal. The terminology is often medically oriented and can be difficult to interpret.
The final paragraph is typically a summary of the findings, often generated to answer the question posed by the ordering physician.