A radioactive tracer used for medical diagnosis should ideally have
- A. a long half life and emit alpha particles
- B. a short half life and emit gamma rays that escape the body for detection
- C. a very long half life and emit beta particles
- D. no radiation at all
Explanation
Gamma radiation escapes the body so an external camera can detect it, and a short half life means the activity falls quickly once the scan is done, limiting the patient's dose. Technetium 99m, with a six hour half life, is the workhorse of nuclear medicine for exactly these reasons. Alpha emitters would deposit all their energy inside the tissue and be detected by nothing.