The proton therapy
Protons have advantageous ballistic properties (see figure below). But to achieve the high precision that these properties allow, there is a need for technologies that are both advanced (proton accelerator, a radioprotective shield) and sophisticated (systems for treatment planning, beam configuration and positioning).
Proton therapy can be used for treatments requiring very high precision, such as choroid melanoma and certain intracranial tumors. Proton therapy was in the experimental phase until the end of the 1980s. Since 1990, several dedicated hospital centers have been built or are planned, principally in Japan and the United States.