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Abstract

Magnetic resonance (MR)-guided radiotherapy (MRgRT) enables new treatment procedures such as online treatment plan adaption based on daily imaging of the patient. This allows for the delivery of high radiation doses to the tumor while optimally sparing surrounding healthy tissue. However, such complex workflows require thorough quality assurance including dedicated end-to-end tests to validate the feasibility and overall accuracy of each specific treatment workflow. In this thesis, end-to-end tests for online adaptive MRgRT in presence of inter-fractional anatomy changes were developed. For this, a standardized protocol for 3D polymer gel (PG) dosimetry and new anthropomorphic materials simulating the image contrast of real patients in computed tomography and MR imaging were developed. These methods were validated resulting in uncertainties < 5 % for PG dose measurements and < 3.5 % for the imaging parameters of the phantom materials. Finally, two end-to-end tests were developed and implemented at a 0.35 T MRgRT device using (i) a highly reproducible geometric phantom and (ii) an anthropomorphic and deformable pelvis phantom. These tests resulted in Gamma-index passing rates (3 %⁄ 3 mm) of 93.1 % (i) and 98.9 % (ii) for the PG-filled targets and demonstrated the feasibility of online adapted MRgRT in presence of inter-fractional anatomical changes.