Skelettszintigraphie
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
- malignancy: detection and follow-up of skeletal metastases
- detection of radiographically occult fractures, e.g. stress or insufficiency fractures
- osteomyelitis
- reflex sympathetic dystrophy
- hip joint prosthesis: evaluation for infection or loosening
- Paget disease
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
Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Skelettszintigraphie: