At the new heavy ion tumor therapy facility of the Gesellschaft fur Schweri
onenforschung at Darmstadt positron emission tomography (PET) has been impl
emented for in-beam and in-situ therapy control, i.e. during the tumor irra
diation. The components necessary for this dedicated PET-imaging and their
integration into the framework of therapy planning and quality assurance of
heavy ion cancer treatments are presented. Results of the first applicatio
n of this PET-method to patient treatments are reported.