Medical physics aspects of radiotherapy with ions.
In December 1997, a radiotherapy facility for carbon ions began clinical operation at GSI and 230 patients were treated there until mid 2004. It is the first facility that established beam scanning and active energy variation for the beam delivery of ions. The work is performed in collaboration with the University of Heidelberg and the German Cancer Research Center (DKFZ). The medical physics aspects of the project, like beam delivery, dosimetry of ions beams and virtual therapy planning will be presented together with the latest clinical results. An outlook on the design and status of the hospital based ion facility, that is currently being built in Heidelberg, will be given.