Amsterdam UMC is an academic hospital where high level research is applied in practice. One of the outpatient clinics of location VUmc is the radiotherapy department. Radiotherapy utilises X-ray radiation to damage cancer cells. During their treatment period, cancer patients visit the department once a day to receive a radiotherapy treatment. Before the radiotherapy treatment can start an extended preparation process is executed. Improving the patient order flow in the radiotherapy preparation process is the subject of this research. The preparation process is a complex process: Many different process steps are necessary to prepare the radiotherapy of a patient. Due to the presence of a waiting queue before each of the process steps, the flow is restricted and errors occur in the corresponding information flow. Often, the reason is the limited insight in the other process step. No overarching control is available to control the flow between the different sections. Interventions occur, but does not rely on organized control structure. The available control is only taking into account the own process step. The fact that the radiotherapy department is too much functionally organised is the main reason for the existence of these problems. The functional design is a requirement for the radiotherapy system. However, within the outline of the functional design, improvements are possible. These improvements have to create an improved flow of patients with a transparent and coordinated execution. The main solution for the problem is the design of control structure based on the matrix organisation theory. The functional control structure remains and a patient order control structure is designed. The functional control structure is elaborated by the measure of the length of the waiting queue of the previous process step. The patient order control structure controls the flow of the patient orders throughout the preparation process. This control is executed on the basis of the date of the start of the radiotherapy treatment. The start of the radiotherapy treatment is the end of the preparation process. This date is determined earlier in the process and the different process step due times will be adapted according to that date. ewline The solution is able to improve the transparency in the department. The patient order progress is monitored during the preparation process and the different process steps will have more insight in the upcoming flow. Especially the patient order control structure is able to coordinate the flow based on the determining of the date of the start of the treatment in an earlier phase. For the examination of the effect of the proposed patient order control structure, a simulation model is built. The simulation model shows the positive effect on the flow of the patient orders through the department: The variation in the waiting queue length is reduced, the variation in the process time is reduced and the variation in the number of patients who will start their treatment on a certain day is reduced.