Bone scan

Dr Jeremy Jones et al.

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. 

Clinical indications

Patient preparation

  • hydration
  • remove metal objects
  • void immediately before study

Tracer dose and route of administration

Tc99m diphosphonate is administered intravenously, at a dose of 20 mCi.

Phases

Flow phase
  • 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.

Delayed phase
  • 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
Delayed/delayed
  • obtained 24 hours after injection as a static image

See also

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