Positron Emission Tomography (PET) has the unique ability to show functional processes as they occur in the body. PET detects photons emitted from a short-lived radioactive sugar analogue called F18 or FDG. When this drug is injected, it emits photons that are detected by the PET scanner and allows the construction of a 3-D image of the body's glucose metabolism. This is important because most cancerous tumors have a high glucose metabolic activity.
The resulting 3-D images can be used to find normal and abnormal processes, providing doctors with information about the body's biochemistry that can't be seen any other way.