In nuclear medicine, radiopharmaceuticals visualize which aspect of an organ?

• A. Anatomy
• B. Physiology or function at the molecular level
• C. Size
• D. Blood supply

Answer: (B)

Radiopharmaceutical imaging targets how tissues work at the cellular level, not just what they look like. The tracer’s distribution reflects underlying physiological processes—glucose use, receptor expression, transport and enzyme activity—so the resulting images map molecular function rather than static structure. For example, PET tracers like FDG track glucose metabolism, highlighting how actively cells are functioning. Other tracers can show receptor activity or perfusion, all illustrating physiology rather than merely anatomy or size.