History of hadron therapy accelerators

•We describe the history of hadron therapy accelerators from the first cyclotrons.•We give examples of the hadrontherapy machines that have treated most patients.•The difference between carbon ion accelerators and proton accelerator is presented.•We discuss thoroughly the present challenges related to novel acceleration techniques.

In the last 60 years, hadron therapy has made great advances passing from a stage of pure research to a well-established treatment modality for solid tumours. In this paper the history of hadron therapy accelerators is reviewed, starting from the first cyclotrons used in the thirties for neutron therapy and passing to more modern and flexible machines used nowadays. The technical developments have been accompanied by clinical studies that allowed the selection of the tumours which are more sensitive to this type of radiotherapy. This paper aims at giving a review of the origin and the present status of hadron therapy accelerators, describing the technological basis and the continuous development of this application to medicine of instruments developed for fundamental science. At the end the present challenges are reviewed.