Current status of real-time imaging of antiproton annihilation in biological targets

Following a successful pioneering study of the biological effects of antimatter ( the AD-4/ACE experiment at CERN), the use of antiprotons in clinical radiotherapy became a very serious possibility. A major part of any future radiotherapy using antiprotons will be real-time imaging of antiproton annihilation in biological targets. In principle, real-time imaging is possible thanks to the secondary particles, neutral pions and charger pions, produced by the annihilation of antiprotons in the cells they come to a stop in.Neutral pions decay dominantly and almost instantaneously into a photon pair, and one approach to real-time imaging is based on the detection of these high-energy gammas. An alternative is based on the detection of charged pions, which have lifetimes almost a billion times longer than neutral pions. This paper is a brief review of this field of research, from the first real-time imaging achieved by the AD-4/ACE experiment in 2004 to the present day.