What chemical is in the injection for pet scans?

Radioactive glucose: Radioactive glucose, which sounds scary but is safe!

F18-FDG: Different pet tracers exist for positron emitting scans (pet) scans. The most widely used for oncologic purpose is f18-fdg (fluorine-18-fludeoxyglucose) which is a modified glucose (fdg) attached to a radionuclide (f18) that emits gamma photons of 511 kev (energy) and has a physical half-life of 110 minutes.

Generally F-18: The p in pet stands for positron - all isotopes used in pet have to be positron emitters. The most common isotope used in pet today is f-18 fluorine. It has an half life of 110 minutes, and is most frequently chemically incorporated with glucose as f-18 fluorodeoxyglucose, or f-18 fdg, which distributes in cells based on glucose metabolism (or consumption).

Pet tracers: There are different types of pet scans (for heart, brain, or oncologic purposes) but most common is for oncologic purpose which uses F18-FDG (fluorodeoxyglucose) which is radiolabeled glucose. This is why your sugar is checked before scan as high sugar could compete with tracer for uptake. The tracer itself will expose you to some radiation but you should not feel any effects from tracer.