PET Scan
Definition
Imaging metabolism itself — a radioactive sugar tracer lights up hungry tissues like tumors on the scan.
Technical definition
Positron Emission Tomography: an FDG tracer emits positrons; the annihilation gamma pairs, detected in coincidence, map tracer concentration.
Example
Cancer staging uses PET — tumors guzzle glucose, so they blaze bright against quieter healthy tissue.
Common confusion
PET shows function (what is active), not anatomy (what is where) — which is why PET is fused with CT: one maps activity, the other maps structure.