PhysicsCode 9702
PET scanning
What this topic asks you to be able to do
- understand that a tracer is, in essence, a substance in which radioactive nuclei are present, and that it may be put into the body and then absorbed by the tissue under investigation
- recall that a PET scan, short for positron emission tomography, uses a tracer that undergoes β+ decay
- understand that a particle and its antiparticle annihilate when they interact, with mass–energy and momentum both conserved in the process
- explain that during PET scanning, positrons released as the tracer decays are destroyed through annihilation upon encountering electrons in the tissue, which yields two gamma-ray photons moving in opposite directions
- work out the energy carried by each gamma-ray photon released when an electron-positron pair is annihilated
- understand that gamma-ray photons produced by an annihilation event leave the body, where detectors can pick them up, and that processing their arrival times creates an image showing the concentration of tracer in the tissue