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bone scan





An imaging test that shows areas of increased or decreased bone turnover. A bone scan involves injecting a radioactive material (radiotracer) into a vein. The substance travels through the bloodstream to the bones and organs. As it wears away, it gives off radiation, which is detected by a camera that slowly scans the patient's body. The camera takes pictures of how much radiotracer collects in the bones.

If a bone scan is done to see if there is 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 (see metastais), images are taken only after the 3 to 4 hour delay.

The scanning part of the test lasts about 1 hour. The scanner's camera may move above and around the patient, so there is no need for him or her to change positions.


Why a bone scan is performed

A bone scan is used to:
  • Diagnose a bone tumor or bone cancer.
  • Determine if a cancer that began elsewhere in the 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.

Results of a bone scan

Test results are considered normal if the radiotracer moves evenly throughout all the bones in your body. 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

Related categories

   • HEALTH AND DISEASE
   • MEDICAL TESTS