Radiopharmaceutical

1
(No Transcript)
2
Radiopharmaceutical

• Tc-99m diphosphonate
• 140 KeV T1/2 6 hrs
• 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
• 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
• Complements anatomic studies
• Blood flow is required to deliver the
  radiopharmaceutical to the extracellular space
  around osteoblasts
• Osteoclastic function not measured by bone scan

4
Three-Phase Bone Scan

• Early arterial flow seconds after injection
• Increased blood pool a few minutes before bone
  labeling begins
• Intense delayed labeling gt3 hrs after injection
• Requires several days before development
• Radiographic changes may not be seen for 10-14
  days

5
Three-Phase DDx

• Osteomyelitis
• RSD (aka Complex Regional Pain Syndrome)
• Trauma/Fracture
• Cellulitis (2-phase )