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RadiopharmaceuticalRadiopharmaceutical
Tc-99m diphosphonate Tc-99m diphosphonate 140 KeV; T1/2 6 hrs140 KeV; T1/2 6 hrs Excreted by glomerular filtration in kidneysExcreted by glomerular filtration in kidneys
– 40% by 4 hrs; 80% by 24 hrs (in normals)40% by 4 hrs; 80% by 24 hrs (in normals) Normal renal function clears soft tissue activity, Normal renal function clears soft tissue activity,
which improves image quality b/c of improved which improves image quality b/c of improved target/backgroundtarget/background
3-4 hrs after injection is a good compromise 3-4 hrs after injection is a good compromise between remaining radioactivity and background between remaining radioactivity and background reductionreduction
The Bone ScanThe Bone Scan
Is a map of osteoblastic activity in Is a map of osteoblastic activity in response to a variety of conditionsresponse to a variety of conditions
Complements anatomic studiesComplements anatomic studies Blood flow is required to deliver the Blood flow is required to deliver the
radiopharmaceutical to the radiopharmaceutical to the extracellular space around osteoblastsextracellular space around osteoblasts
Osteoclastic function not measured by Osteoclastic function not measured by bone scanbone scan
Three-Phase Bone ScanThree-Phase Bone Scan
Early arterial flow seconds after injectionEarly arterial flow seconds after injection Increased blood pool a few minutes Increased blood pool a few minutes
before bone labeling beginsbefore bone labeling begins Intense delayed labeling >3 hrs after Intense delayed labeling >3 hrs after
injectioninjection Requires several days before Requires several days before
developmentdevelopment Radiographic changes may not be seen Radiographic changes may not be seen
for 10-14 daysfor 10-14 days
Three-Phase DDxThree-Phase DDx
OsteomyelitisOsteomyelitis RSD (aka Complex Regional Pain RSD (aka Complex Regional Pain
Syndrome)Syndrome) Trauma/FractureTrauma/Fracture Cellulitis (2-phase +)Cellulitis (2-phase +)
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