bone scintigraphy

Bone scintigraphy (a.k.a. bone scans) are a nuclear medicine (scintigraphic) study that makes use of technetium-99m (commonly Tc-99m-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

  • optimal hydration
  • remove metal objects
  • void immediately before study

Tracer dose and route of administration

Tc-99m diphosphonate is administered intravenously, at a dose of 740 Mbq (20 mCi) in adults.

Phases (kinetic modelling)

Flow phase
  • 2-to-5 second images are obtained for 60 seconds after injection
  • demonstrates perfusion
  • characterizes blood flow to a particular area
Blood pool phase
  • obtained 5 minutes after injection
  • demonstrates the blood pool (balance between plasma and interstitium), 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
  • obtained 2-4 hours later
  • urinary excretion has decreased the amount of the radionuclide in soft tissue
  • mechanism of uptake is not known with certainty, although it has been proposed that the radiotracer attaches to hydroxyapatite crystals (chemisorption)
  • 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