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Abstract

This thesis investigates uncertainties emerging from CT data to stopping power ratio (SPR) cali- bration and characterizes the potential of dual energy CT (DECT) as an alternative for treatment planning in ion radiotherapy. The robustness of the stoichiometric calibration was tested for variations of the initial CT number measurements. Based on the results, it is suggested to use higher X-ray tube voltages and include more dense materials in the initial CT scan. Complementarily, the separation of electron density and effective atomic number with DECT helps to resolve tissues with uncommon compositions: In a first patient (head and neck case), DECT-predicted SPR were found to differ by 2 % in the ventricles and by 5-8 % in the petrous part of the temporal bone compared to single energy CT (SECT) predictions. On the other hand, verification of DECT-based SPR prediction for tissue surrogates showed excellent agreement of (0.6±0.3) % with measurements, and noise levels of DECT-based SPR predictions were found to be elevated by only 0.2-0.4 pp compared to SECT. Both DECT contrasts were further exploited for Monte-Carlo-based dose planning and improved tissue decomposition. A validation of DECT-predicted SPR in absolute terms with a reference method, such as heavy ion CT, would help to translate the presented potential benefits of DECT to its future clinical application in ion radiotherapy.