Medical Accelerators for Hadrontherapy with Protons and Carbon Ions ( With an Introduction to the Physical Advantage of Heavy Charged-Particle Radiation )

Hadrontherapy is ideally suited to treat tumours that are deep-seated, located close to critical organs and respond poorly to conventional photon or electron radiotherapy. The use of proton and carbon ion beams for therapy will not only improve the tumour control probability for certain malignant diseases, but also reduce long-term complications in the surrounding healthy tissue. Therapy using protons and carbon-ions for deep seated, but also for superficial and semi-deep seated tumours is still mainly confined to experimental facilities that parasitically use the accelerators and beam lines of scientific research centres [1]. In this paper, emphasis is put on basic physical concepts describing interactions of photons and ions in matter such as the Linear Energy Transfer (LET), attenuation, range-dose profiles and multiple scattering. Biological concepts are touched in order to explain the importance of cell survival and the Relative Biological Effectiveness (RBE) of charged particles. Latest developments on the technical design for accelerator, beam transfer and beam delivery systems are explained, using recent results of the Proton Ion Medical Machine Study (PIMMS) at CERN as an example. Finally, patient statistics and an overview of existing treatment centres provide the conclusions and an outlook towards possible future developments and scenarios.