Which term describes a radioactive compound used for diagnostic imaging or therapy?

• A. Radionuclide
• B. Radiopharmaceutical
• C. Tracer
• D. Isotope

Answer: (B)

In nuclear medicine, the term for a radioactive compound used for diagnostic imaging or therapy is radiopharmaceutical. This category combines a radionuclide with a pharmaceutical form that targets specific tissues or processes, so it can be used to image the body with modalities like PET or SPECT, or to deliver therapeutic radiation to a disease site. A radionuclide by itself isn’t a complete drug—it’s just the radioactive component. A tracer is a broader label for substances used to study biological processes, and an isotope refers to the nuclear type of an element, not its medical application. Radiopharmaceuticals are the standard term for the actual medical agents designed for both imaging and treatment.