Particle therapy is the expanding radiotherapy treatment option of choice for cancer. Its cost, however, is currently hindering its worldwide expansion. Also, the ideal application of particle therapy is restricted by a series of unsolved technical challenges. Both the cost and technical limitations are directly traceable to dependence on legacy accelerators and their associated treatment possibilities. This chapter is written to address these needs. Firstly, a technical overview is presented of photon and particle therapy for cancer tumours. Secondly, the underlying limitations of the existing legacy systems are identified, especially those related to accelerators, and suggestions are made for current and future developments to address these shortcomings. The legacy systems referred to here are of the slow scanning variety using large, circular accelerators. This paper also attempts to make a scientific comparison of the various types of accelerators currently used or being developed for particle therapy. The following procedure is pursued to perform a comparison between various types of accelerators: (1) The parameters which are pertinent to particle therapy accelerators (‘specified parameters’) are identified from clinical efficiency and overall cost considerations. (2) The range and values of ‘specified parameters’ associated with each type of particle therapy accelerator are identified. (3) A comparison is made on the best match between the various types of accelerators for each of the ‘specified parameters,’ i.e., the best in class accelerator, when compared to each criterion. (4) Based on this match, an overall conclusion is made on the type of accelerator which best fits the needs for particle therapy.
