Which imaging modality uses radioactive tracers to measure metabolic activity?

Which imaging modality uses radioactive tracers to measure metabolic activity?

• A. Magnetic Resonance Imaging
• B. Ultrasonography
• C. Radiography
• D. Positron Emission Tomography

Answer: (D)

Measuring metabolic activity with radioactive tracers is the hallmark of positron emission tomography. In PET, a tracer such as FDG is injected and taken up by tissues in proportion to their metabolic rate. The tracer emits positrons that collide with electrons, producing gamma photons that the scanner detects to generate an image showing where metabolism is highest. This functional information helps identify areas like cancer or inflamed tissue, where glucose use is elevated. Other imaging methods rely on structural information rather than metabolic activity: MRI uses magnetic fields to image anatomy (and can show some functional changes with special techniques but not via radioactive tracers), ultrasonography uses sound waves, and radiography uses X-rays to visualize structure. So the modality that uses radioactive tracers to measure metabolic activity is PET.

Measuring metabolic activity with radioactive tracers is the hallmark of positron emission tomography. In PET, a tracer such as FDG is injected and taken up by tissues in proportion to their metabolic rate. The tracer emits positrons that collide with electrons, producing gamma photons that the scanner detects to generate an image showing where metabolism is highest. This functional information helps identify areas like cancer or inflamed tissue, where glucose use is elevated. Other imaging methods rely on structural information rather than metabolic activity: MRI uses magnetic fields to image anatomy (and can show some functional changes with special techniques but not via radioactive tracers), ultrasonography uses sound waves, and radiography uses X-rays to visualize structure. So the modality that uses radioactive tracers to measure metabolic activity is PET.