  Radiotherapy is one of the main methods in the successful treatment of
cancer. The tumor is irradiated with photons or charged particles (e.g.
protons), and in the case of massive charged particles, the treatment results
in less unnecessary dose outside the tumor and therefore less side effects for
the patient and a faster recovery. However, the dose planning of hadron therapy
is calculated from photon CT measurements, which results in large uncertainties
in the planning and therefore in a necessary enlargement of the treatment area.
This uncertainty can be reduced by performing the CT scan using protons. The
current contribution shows the development of a sampling calorimeter for proton
CT measurements and describes the state of the project.
