Which imaging modality uses a radioactive substance to assess bone activity?

• A. Bone scan
• B. Cholesterol test
• C. Complete blood count
• D. Calcium test

Answer: (A)

Bone scan uses a radioactive tracer to visualize bone metabolism. After injection, the tracer collects in areas of active bone turnover, so regions with increased osteoblastic activity light up on the scan as “hot spots.” This makes it useful for detecting fractures, infection, malignancy, or other causes of abnormal bone activity, often sooner than plain X-rays. The other options are blood tests that assess substances like cholesterol, blood cell counts, or calcium levels, and they do not image bone activity or use radioactive materials.