Recent developments for the delivery of proton and ion beam therapy have been
significant, and a number of technological solutions now exist for the creation
and utilisation of these particles for the treatment of cancer. In this paper
we review the historical development of particle accelerators used for external
beam radiotherapy and discuss the more recent progress towards more capable and
cost-effective sources of particles.Comment: 53 pages, 13 figures. Submitted to International Journal of Modern
Physics
