What is Positron emission tomography?
Positron emission tomography (PET) is a neuroimaging technique that uses radioactive tracers to measure specific biochemical processes in the brain, including glucose metabolism, blood flow, receptor density, and neurotransmitter activity.
How it works
PET works by injecting a radioactive tracer that is absorbed by metabolically active tissue. The tracer emits positrons that produce detectable gamma rays. Different tracers measure different processes: FDG-PET measures glucose metabolism (a proxy for neural activity), while specialized tracers can image specific receptor types (dopamine D2 receptors, serotonin transporters) or neurotransmitter release. PET’s unique advantage over fMRI is its ability to measure specific neurochemical processes; its limitations include radiation exposure, lower spatial and temporal resolution, and high cost.
Applied example
PET imaging of dopamine receptors in people with addiction reveals reduced D2 receptor availability in the striatum, providing direct neurochemical evidence that chronic substance use alters the brain’s reward system. This finding helped establish addiction as a brain disorder rather than a moral failing.
Why it matters
PET provides unique access to the brain’s neurochemistry, revealing the molecular processes that underlie cognition, motivation, and psychiatric illness in ways that other imaging methods cannot.
