The measurement and comparison of dosimetry parameters of Orion (4 MV) lineer accelerators after magnetron changes

OBJECTIVES: Orion 5 (GE) model linear accelerator at our department was installed in 1998. Magnetrons have been replaced because of different technical problems up to now since installation. But any deviation from the original setting could have caused specific changes in the beam parameters. Therefore, we measured and evaluated the beam parameters for the possible changes in the values following magnetron replacements. METHODS: The measurements were performed for quality index (TPR20/10), percentage depth dose (PDD), beam profiles for open fields, out-put, wedge out-put factors. The measurement data were compared with the standard values and the ones used. RESULTS: Adjusted TPR20/10 values were found to be changing within at most 0.6% with BJR Sup. 25 data and PDD, out-put, dose profiles and wedge filter transmissions were found to be changing within at most 2% with BJR Supplement 25 data. CONCLUSION: The results of the measurements performed following all magnetron replacements were found to be not exactly the same but within acceptable limits.