In a whole-body bone scan using Tc-99m MDP, areas of increased radiotracer uptake ('hot spots') are seen in the lumbar vertebrae of an elderly male with known prostate cancer. This is most likely due to:

• A Osteolytic metastases with active bone destruction
• B Degenerative disc disease at those levels
• C Osteoblastic metastases with reactive new bone formation ✓
• D Fracture callus formation

Explanation

Tc-99m MDP bone scans detect osteoblastic activity — areas of new bone formation show increased tracer uptake. Prostate cancer characteristically produces osteoblastic (sclerotic) bone metastases, which generate intense reactive bone formation, producing hot spots. Pure osteolytic metastases (as in myeloma, renal cell carcinoma) may show cold spots or normal scans because there is insufficient osteoblastic response to take up MDP. Degenerative disease also produces hot spots but has a characteristic pattern (facet joints, discovertebral junction).

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.