No abstract available

No abstract available

[en] Full text: It is known that a high precision in radiotherapy is essential to ensure a successful radiation treatment. To reach this goal it is necessary to detect and minimise many errors, which can be done through a periodic program of quality control, not only internal checks but also participating in external audits that attempt to control the absorbed dose delivered and detect any source of error, coming from the machine itself or from human mistakes. Under the frame of the International Quality Assurance Network for Dosimetry in Radiotherapy proposed by the International Atomic Energy Agency, a National External Audit Group (EAG) has been created in our country, composed by the Secondary Standard Dosimetry Laboratory (SSDL), 2 Medical Physics and 1 Medical Radiotherapist. The SSDL and one of the Medical Physics belong to the National Atomic Energy Agency, meanwhile the rest of the group belong to the National Pediatric Hospital ^Prof. J.P.Garrahan^. This EAG performs external audits to Radiation Therapy Centres with a thermoluminescence system, which is checked periodically by the IAEA. The audits are performed to the ⁶⁰ Co γ-ray and high energy X-ray beams that are being used for medical application in the whole country. The SSDL is the responsible of the thermoluminescence measurements; deviation of the absorbed dose determined by the TLD system from the one informed by the Responsible of the Center within the interval ± 5% are considered acceptable while deviations out of this interval require the intervention of the Medical Physic Group and the Radiotherapist in order to determine the cause of the discrepancies. In 1997, 4 audits performed in reference conditions were carried out 68 ⁶⁰Co units participated in the audits, 61 of them with deviation within the acceptable interval in their first participation, meanwhile 1 got this deviation in repeated audits, after the follow up performed by the Medical Physic Group. Regarding high energy X-ray beams (between 4 and 15MV), 36 of 38 units got this deviation in their first participation, and 2 improved the deviation in repeated audits. The thermoluminescence dosimetry system allows to check not only the reference conditions but many parameters of the radiation beam: different field sizes, use of wedges, points out of the central axis. These results show the importance of having periodic external audits in order to ensure a safe and successful radiation treatment. (author)