IMPROVING SPECIFICITY OF RADIONUCLIDE STUDIES

Question 1

what is this phase of the triphasic technetium scan?

(intravascular) - seconds

Series of rapid 2-5 sec images over the first min as the tracer passes through vascular
compartment

so tracer is intravascular (radionuclide angiogram)

Answer 1

Dynamic, intravascular

Question 2

what is this phase of the triphasic technetium scan?

(extravascular) - minutes

After 5 min only 20-30% of the tracer remains in the intravascular compartment

Images acquired after 5-15 min

Reflects the tracer redistribution into the ECF and therefore relative hyperemia (increased circulatory flow in some areas)

Answer 2

blood-pool, extravascular

Question 3

what is this phase of the triphasic technetium scan?

(in bone) - hours

After 4 hours about 55-60% of initial dose of tracer is in bone (rest has been secreted)

Reflects relative bone turnover

Answer 3

Static, bone

Question 4

retained ECF tracer equals?

Answer 4

unwanted background noise

Question 5

what is this phase of the triphasic technetium scan?

not routinely required

Uptake in Lamellar bone (mature) ends at about 4 hours but continues for woven bone (immature) seen in things like OM and bone tumors

Will also get a higher lesion to background ratio

Answer 5

(24 hr.) Delay