How Does a PET Scan Work?

PET scanners work by detecting the radiation given off by an injected radioactive drug known as a tracer. In most PET scans, the tracer used is fluorodeoxyglucose (FDG), similar to a naturally occurring glucose. 

The tracer collects in areas of the body with higher levels of biochemical or metabolic activity. By analysing the areas where the radiotracer does and does not build-up, it's possible to determine how specific body functions are working.