Quality control and quality assurance for units that produce ionizing radiation for radiotherapy, summarizes, archives, and currently dates the performance of these units of irradiation by comparison to the parameters since the time of commissioning. Siemens ONCOR Impression is an advanced linear accelerator that can be used for routine clinical applications as well as for complex and advanced treatments such as stereotaxic radiosurgery. The linear accelerator enables the production of two clinical photon beams with energies 6 MV and 7 MV as well as beams of electrons with energies from 6 MeV to 18 MeV. Quality control of a linear accelerator consists on dosimetric, mechanical and safety checks based on international standards and departmental decisions. This work presents the daily dosimetric measurements of the flattened filter 6MV photon beam with the Octavius 729 matrix detector. Data were collected over a 12-month period and results obtained by daily measurements showed that the output of linac (dose), the uniformity and symmetry of the 6 MV photonic beam were within 2% to 3 % from reference values in compliance with recommendations of AAPM 142. The output mean value was 1.55 ± 0.01 Gy, the flatness mean value was 109.44 ± 0.28 % and 109.56 ± 0.45 % in TG and LR profiles and the mean symmetry value was 102.07 ± 0.53 % and 101.69 ± 1.09 % in TG and LR profiles.

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