This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Imaging and basics in Ohopedics, Subject name: Orthopaedics
Most sensitive investigation for early bone infections is: 
Select and explain. 
A. X-ray, B. CT scan, C. Bone scan, D. USG
C: Bone scan
Answer: C: Bone scan 
Explanation: MRI can pick up marrow changes in metaphysis. (Best radiological investigation for Osteomyelitis and Tuberculosis). Bone scan is next in preference to MRI to pick up infections by picking osteoblastic activity at the site of infection. It is highly sensitive but low specificity. Culture and growth of organism is most definitive diagnostic modality for Osteomyelitis. MRI(6-8 hrs) > Bone Scan(12-24hrs) > X-Ray(>24hrs)