Bone scans are a nuclear medicine (scintigraphic) study that makes use of Technetium 99m (commonly Tc99m-methylene diphosphonate (MDP)) as the active agent.
The study has three phases which follow intravenous injection of the tracer. Sometimes a fourth (delayed/delayed) phase is performed.
- malignancy: detection and follow-up of skeletal metastases
- detection of radiographically occult fractures, e.g. stress or insufficiency fractures
- reflex sympathetic dystrophy
- hip joint prosthesis: evaluation for infection or loosening
- Paget's disease
- remove metal objects
- void immediately before study
Tracer dose and route of administration
Tc99m diphosphonate is administered intravenously, at a dose of 20 mCi.
- 2-to-5 second images are obtained for 60 seconds after injection
- demonstrates perfusion and characterises the blood flow to a particular area
Blood pool phase
- the blood-pool image is obtained 5 minutes after injection
- demonstrates the blood pool, not the blood flow
- inflammation causes capillary dilatation and increased blood flow
If the study is going to be a triphasic bone scan, a third phase is added.
- the bone image is obtained 2-4 hours later
- urinary excretion has decreased the amount of the radionuclide in soft tissue
- mechanism of uptake is not uncertainly known
- degree of uptake depends on blood flow and rate of new bone formation
- obtained 24 hours after injection as a static image
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- 3. Alazraki N, Dries D, Datz F et-al. Value of a 24-hour image (four-phase bone scan) in assessing osteomyelitis in patients with peripheral vascular disease. J. Nucl. Med. 1985;26 (7): 711-7. Pubmed citation