What a Bone Scan Shows
A bone scan (also called bone scintigraphy) is a nuclear medicine imaging test that evaluates the metabolic activity of bones throughout the body. It detects areas where bone is being broken down or rebuilt at an abnormal rate, which can indicate a range of conditions including cancer spread to bones, fractures (including stress fractures that may not show on X-rays), bone infections, and certain metabolic bone diseases.
How a Bone Scan Works
A small amount of a radioactive tracer called technetium-99m MDP is injected into a vein. This tracer is attracted to areas of active bone metabolism. After a waiting period of 2 to 4 hours (during which you can go about normal activities and are encouraged to drink water), you return for the scan. A gamma camera captures images of your entire skeleton, showing where the tracer has concentrated.
Areas of increased tracer uptake (called “hot spots”) appear brighter on the images. These represent regions of heightened bone activity. The pattern and location of these hot spots help the nuclear medicine physician determine the likely cause.
Common Reasons for a Bone Scan
Cancer metastasis: Many cancers, including breast, prostate, and lung cancers, can spread to bones. A bone scan can detect these metastases across the entire skeleton in a single examination, often before they cause symptoms or become visible on X-rays.
Unexplained bone pain: When a patient has bone pain that does not have a clear explanation, a bone scan can help identify the cause by highlighting areas of abnormal bone activity.
Fractures: Stress fractures and other occult fractures (not visible on standard X-rays) can be detected on a bone scan because the healing process involves increased bone metabolism.
Bone infection (osteomyelitis): Infection in bone causes a strong metabolic response that shows up clearly on a bone scan.
Joint conditions: While not the primary purpose, bone scans can show patterns of increased activity in joints affected by arthritis or other inflammatory conditions.
Preparation and the Scan Day
No special preparation is usually required for a bone scan. You can eat normally, take your regular medications, and continue your usual activities before the appointment. After the tracer injection, you will be asked to drink plenty of water during the waiting period to help the tracer distribute properly and to flush excess tracer through the kidneys.
The scan itself takes approximately 30 to 45 minutes. You lie on a table while the gamma camera moves slowly over your body, capturing images from different angles. The procedure is painless.
Understanding the Results
The nuclear medicine physician analyses the images and provides a report to your referring doctor. Hot spots on a bone scan are not automatically cancer. Many benign conditions cause increased bone uptake, including arthritis, healing fractures, and normal areas of higher activity (like joints and growth plates in younger patients).
The location, pattern, and intensity of the hot spots, combined with your clinical history, help determine the most likely diagnosis. In some cases, additional imaging such as CT, MRI, or a PET CT scan may be recommended for further evaluation of specific findings.
Your doctor will discuss the results with you and explain what they mean for your specific situation and treatment plan.