Radiobiological Effects of Highly Charged Ions

The radiobiological effects of highly-charged-ion beams are of interest for tumortherapy and for radioprotection in space. In tumor therapy, high-energy protons and carbon ions exhibit an inverse dose profile, i.e. an increase of energy deposition with penetration depth. This allows a greater tumor dose for protons and carbon ions than for photons. In addition, for the heavier carbon ions, this increase in dose is potentiated by a greater relative biological efficiency (RBE). On the other hand, the greater RBE of particles is the concern of space-radioprotection because the radiation burden of the cosmic galactic radiation consists of heavy charged particles from protons to iron ions. In this paper, the physical and biological basis of particle radiotherapy and its present status will be presented. For space radioprotection, the particle spectrum will be given and the risk of cancer induction and long-term genetic mutation will be discussed. In contrast to the cell inactivation problem for