Particle radiotherapy: historical developments and current status.

The current status of particle radiotherapy from a historical perspective is presented. This is done with a personal view and contains personal references and memories during the development of particle radiotherapy. The particles covered are fast neutrons, neutron capture therapy, protons, helium ions, pions and heavy ions. International cooperation in the development of the field of particle therapy, its impact on radiobiology and conventional radiotherapy, and some personal reflections and conclusions are also presented briefly.