Which imaging modality visualizes metabolic processes using radioactive tracers?

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

Answer: (D)

Visualizing metabolic processes with radioactive tracers is what PET imaging does. In PET, a biologically active molecule, often a glucose analog like FDG, is labeled with a radioactive tracer. Tissues with high metabolic activity take up more tracer, and the scanner detects the emitted radiation to create images that reflect metabolic activity rather than just structure. This makes PET particularly useful for spotting cancers, evaluating brain function, or assessing heart muscle viability. Other imaging methods—MRI, CT, and ultrasound—primarily depict anatomy or tissue structure: MRI uses magnetic fields to differentiate soft tissues, CT uses X-ray density, and ultrasound uses sound waves to visualize organs and motion. Therefore, the modality that visualizes metabolic processes using radioactive tracers is PET.