The use of heavy charged particles in the radiation therapy of tumors

Beams of heavy charged particles like carbon or oxygen ions represent the ultimate tool of external radiotherapy of deep-seated tumors.Small range and lateral scattering and the increase of the energy deposition with penetration depth are the physical basis for a more efficient tumor targeting. High biological efficiency in the tumor is the perequisite for a successful treatment of tumors radioresistant to sparsely ionizing radiation.The possibility to perform target-conform irradiation and to control the achieved actual distribution using PET techniques guarantees that biological highly efficient stopping particles can be restricted to the tumor volume only.Although the physical and radiobiological properties of ion beams are very favorable for therapy, the necessity to produce these particles in an accelerator has restricted the general application of heavy ions up to now.Presently, the heavy ion accelerator SIS at GSI is the only source of heavy ion beams sufficient in enrgy and intensity for therapy in Europe.Therefore,a therapy unit is presently under construction at GSI at which the techniques and radiobiological advantages of particle beams in radiotherapy will be examined.