This thesis deals with the topic of the integration of magnetic resonance imaging technology in modern clinical practice of radiotherapy; explores its potential to increase treatment precision, efficiency and patient outcomes. The thesis shows how MRI is used from simulation to the implementation of radiotherapy in real time. MRI registration with CT is described, followed by quality assurance with special emphasis on geometric distortion. The introduction describes the application of MRI for radiotherapy planning, then the role during treatment; functional imaging techniques are presented and the role of MRI for movement control is described. Dosimetric requirements and techniques used to replace CT are covered, as well as imaging verification of the radiation field in real time. The first results obtained on MRI-linear accelerators are presented, where the technical challenges and the current status of the MRI-linear accelerator are covered. At the end of the thesis, the future role of magnetic resonance imaging in radiotherapy is considered, and conclusions are drawn based on the analysis and results of various professional articles dealing with the same topic.