Annihilation of Antimatter
Positron Electron Tomography

Example:             e⁺ +e^- --> g+ g  (photon + photon)

Experiment:

• ²²Na nucleus (in salt) is unstable,
• 
        emitting positrons
• positron finds an electron in NaCl crystal
• annihilation produces 2 back-to-back gamma rays

Application:

• ingested radioactive salt is rapidly metabolized,
• 
         concentrated by breast cancer
• trace back 2 gamma rays to source
• 
  with < 1mm accuracy, before tumor metastasizes

physicists can also annihilate two particles of tremendous energies to create new, massive particles