Positron emission tomography (PET) is the imaging technique that detects brain function by measuring metabolic activity. It uses radiolabeled tracers, typically glucose analogs, to visualize areas of increased neuronal activity based on glucose uptake. This functional imaging allows assessment of brain metabolism and blood flow, providing crucial information for diagnosing tumors, epilepsy, and neurodegenerative diseases. Unlike CT or MRI, which primarily show anatomical details, PET specifically highlights physiological and biochemical processes in the brain. This makes it invaluable for understanding brain function in clinical and research settings.

Reference: Neuroanatomy, Richard S. Snell, 7th Edition.