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Bone scan
Definition
A bone scan is an imaging test that shows areas of increased or decreased bone turnover (metabolism).
Alternative Names
Scintigraphy - bone
How the Test is Performed
A bone scan involves injecting a radioactive material (radiotracer) into a vein. The substance travels through your blood to the bones and organs. As it wears off, it gives off a little bit of radiation. This radiation is detected by a camera that slowly scans your body. The camera takes pictures of how much radiotracer collects in the bones.
If a bone scan is done to see if you have a bone infection, images may be taken shortly after the radioactive material is injected and again 3 to 4 hours later, when it has collected in the bones. This is called a 3-phase bone scan.
To evaluate metastatic bone disease, images are taken only after the 3 to 4 hour delay.
The scanning part of the test will last about 1 hour. The scanner's camera may move above and around you. You may need to change positions.
You will probably be asked to drink extra water after you receive the radiotracer to keep the material from collecting in your bladder.
How to Prepare for the Test
You must remove jewelry and other metal objects. You may be asked to wear a hospital gown.
Tell your doctor if you are or may be pregnant.
Do not take any medicine with bismuth in it, such as Pepto-Bismol, for 4 days before the test.
How the Test Will Feel
There is a small amount of pain when the needle is inserted. During the scan there is no pain. You must remain still during the examination, and you will be instructed when to change positions by the technologist.
You may experience some discomfort due to lying still for a prolonged period of time.
Why the Test is Performed
A bone scan is used to:
- Diagnose a bone tumor or cancer
- Determine if a cancer that began elsewhere in your body has spread to the bones; common cancers that spread to the bones include breast, lung, prostate, thyroid, and kidney.
- Diagnose a fracture, when it cannot be seen on a regular x-ray (most commonly hip fractures, stress fractures in the feet or legs, or spine fractures)
- Diagnose a bone infection (osteomyelitis)
- Diagnose or determine the cause of bone pain, when no other cause has been identified
- Evaluate metabolic disorders, such as osteomalacia, renal osteodystrophy, primary hyperparathyroidism, osteoporosis, complex regional pain syndrome, and Paget's disease
Normal Results
Test results are considered normal if the radiotracer moves evenly throughout all the bones in your body.
What Abnormal Results Mean
The images should show that the radioactive material has been evenly distributed throughout the body. There should be no areas of increased or decreased distribution. "Hot spots" are areas where there is an increased accumulation of the radioactive material. "Cold spots" are areas that have taken up less of the radioactive material.
Risks
If you are pregnant or nursing, the test may be postponed to prevent exposing the developing baby to radiation. If you must have the test while breastfeeding, you should pump and throw away the breast milk for the next 2 days.
The amount of radiation injected into your vein is very small, and nearly all radiation is gone from the body within 2 - 3 days. The radiotracer that is used exposes you to a very small amount of radiation. The risk is probably no greater than with routine or conventional x-rays.
Risks related to the bone radiotracer are rare, but may include:
- Anaphylaxis (severe allergic response)
- Rash
- Swelling
There is a slight risk of infection or bleeding when the needle is inserted into a vein.
Considerations
Some abnormalities that may be identified on radionuclide bone scans include:
- Arthritis and other degenerative diseases of the bones
- Avascular necrosis
- Bone infections (osteomyelitis)
- Bone tumors
- Fibrous dysplasia
- Fractures
- Paget's disease
- Radiation changes
- Rickets
- Tumors that have spread from other parts of the body to the bone (metastatic disease)
It is important to understand that bone scan findings must be compared with other imaging studies, in addition to clinical information. You should always discuss the significance of abnormal findings with your health care provider.
References
Coleman RE, Holen I. Bone metastases. In: Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, McKena WG, eds. Clinical Oncology. 4th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 57
Lerner A, Antman KH. Primary and metastatic malignant bone lesions.In: Goldman L, Schafer AI, eds.Cecil Medicine. 24th ed.Philadelphia,PA: Saunders Elsevier; 2011:chap 208.
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
