No abstract available

[en] Risk assessment deals with processes, barriers and risk levels to unveil the fragility and weakness and to point out mechanisms that should be implemented to strength an activity. The objective of this work is to investigate the most important aspects for radiological protection of patients, public in general and workers. These results were obtained from the application of the System of Evaluation of Risk in Radiation Therapy (SEVRRA), a software tool developed by the Ibero-American Forum of Radiological and Nuclear Regulatory Agencies - FORO with the purpose of facilitating the evaluation of the risk level on radiotherapy. Data has been collected from a group of twenty Brazilian radiation therapy facilities, which have performed the survey for weakness and strength in terms of initiating events and barriers preventing accidental sequences. It was observed that some of the initiating events occur with high-risk level for majority of facilities. It is related to the absence of some barriers proposed by SEVRRA. The attention is focused on these barriers once its presence would reduce the facilities global risk level. The present investigation reinforces the need to strength the mechanisms that guarantee the effectiveness of such barriers in radiotherapy procedures. The results also show that some radiation therapy accidents around the world could be prevented or mitigated if some kind of risk analysis would have been performed. SEVRRA works as a fundamental tool in the task of identifying national difficulties or weakness and to promote advances in the safety field for the regulation on radiotherapy. (author)

[en] The Monte Carlo Modelling Expert Group (MCMEG) is an expert network specializing in Monte Carlo radiation transport and the modelling and simulation applied to the radiation protection and dosimetry research field. In the first inter-comparison the group launched an exercise to model and simulate a 6 MV LINAC photon beam using several Monte Carlo codes. Experimental measurements carried out in the National Cancer Institute (INCA) in Rio de Janeiro, Brazil, were used to validate the models and simulated results. Now, the group has launched a second inter-comparison exercise for modeling and simulating a radiotherapy treatment planning for prostate cancer. The goal is obtained the dose distribution in the target organ and the neighboring organs. Validation of the computational models were carried out using experimental measurements performed with an Alderson phantom in a hospital in BH/MG, Brazil. This paper reports in detail the modeling process using MCNPx, MCNP6, EGSnrc and Penelope Monte Carlo codes, the source and tally descriptions, the validation processes and the results.

[en] Risk assessment deals with processes, accident-initiating events, barriers and risk ratings to unveil the fragility and weakness of some processes; within this study, specifically related to radiation therapy facilities. Barriers are technical or organizational safety measures put in place to avoid, prevent, detect, control, reduce or mitigate the consequences of an accident once an initiating event has occurred. In this work, radiological risk analysis was performed for a set of 20 Brazilian radiotherapy facilities making use of the freeware sevrra risk-management software. The objective of this study was to define parameters that could be useful in creating an overall risk profile. This profile would be helpful for establishing priorities for decision making and support a risk-informed regulatory process. The most relevant missing barriers in facilities were identified according to three parameters: the ‘importance index’, ‘impacted facilities index’ and the ‘barrier-effectiveness index’. Barriers such as ‘in vivo dosimetry in the first treatment session’, ‘weekly in vivo dosimetry to detect errors in the dose delivering process’, ‘annual external audit for the control of reference dose rate’ and ‘independent verification of calibration by various medical physicists with a different dosimetry equipment’ were found to be the most effective in reducing the risk level of the facilities. The present investigation reinforces the need to strengthen the mechanisms that guarantee the effectiveness of such barriers in radiation therapy procedures. (paper)