2. Radiopharmaceutical Tc-99m diphosphonate Tc-99m diphosphonate 140 KeV; T1/2 6 hrs 140 KeV; T1/2 6 hrs Excreted by glomerular filtration in kidneys Excreted by glomerular filtration in kidneys –40% by 4 hrs; 80% by 24 hrs (in normals) Normal renal function clears soft tissue activity, which improves image quality b/c of improved target/background Normal renal function clears soft tissue activity, which improves image quality b/c of improved target/background 3-4 hrs after injection is a good compromise between remaining radioactivity and background reduction 3-4 hrs after injection is a good compromise between remaining radioactivity and background reduction

3. The Bone Scan Is a map of osteoblastic activity in response to a variety of conditions Is a map of osteoblastic activity in response to a variety of conditions Complements anatomic studies Complements anatomic studies Blood flow is required to deliver the radiopharmaceutical to the extracellular space around osteoblasts Blood flow is required to deliver the radiopharmaceutical to the extracellular space around osteoblasts Osteoclastic function not measured by bone scan Osteoclastic function not measured by bone scan

4. Three-Phase Bone Scan Early arterial flow seconds after injection Early arterial flow seconds after injection Increased blood pool a few minutes before bone labeling begins Increased blood pool a few minutes before bone labeling begins Intense delayed labeling >3 hrs after injection Intense delayed labeling >3 hrs after injection Requires several days before development Requires several days before development Radiographic changes may not be seen for 10-14 days Radiographic changes may not be seen for 10-14 days

5. Three-Phase DDx Osteomyelitis Osteomyelitis RSD (aka Complex Regional Pain Syndrome) RSD (aka Complex Regional Pain Syndrome) Trauma/Fracture Trauma/Fracture Cellulitis (2-phase +) Cellulitis (2-phase +)