Which imaging modality is specifically designed to visualize metabolic processes in tissues using radioactive tracers?

• A. MRI
• B. CT
• C. PET
• D. Ultrasound

Answer: (C)

Measuring metabolic activity in tissues with radioactive tracers is what PET imaging does best. In PET, a radiotracer such as fluorodeoxyglucose behaves like glucose, so tissues with higher metabolic rates—like many cancers, active brain regions, or inflamed areas—take up more tracer. As the tracer decays, positrons are emitted and annihilate with electrons, producing pairs of gamma photons that detectors around the body pick up to create a map of metabolic activity. This functional information focuses on how tissues are using energy, rather than just how they look anatomically, making PET distinct from MRI, CT, or Ultrasound. PET is often fused with CT or MRI to match metabolic patterns to precise anatomy.