Precautions in the interpretation of results when applying the risk matrix technique in brachitherapy HDR

The objective of this work is to present the precautions to be taken in the application and interpretation of the results of the Risk Matrix technique to HDR brachytherapy facilities. To this end, the risk analysis of three HDR brachytherapy facilities was performed, with two computer applications based on the Risk Matrix technique (TECDOC-1685). The first application used was SEVRRA and the second a developed tool (spreadsheet). The results showed discrepancies between the risk profile given by the SEVRRA tool and the obtained with the tool developed. It was systematically observed that the percentage of events At high risk with SEVRRA it was below the percentage obtained with the tool developed. The discrepancies that exceed 5% of events are due to the robustness of some functions of Safety in SEVRRA are inconsistent with those defined by the methodology. The two tools allow to identify the measures to be adopted by the facilities, however, the measures are not sufficient to become consistent with the risk acceptability criteria defined in the methodology. It is concluded that the Risk Matrix technique is useful for assessing the safety of brachytherapy facilities, provided that precaution is taken in adapting it to the particular conditions of an institution, regulatory entities must take into account to issue or not the operation authorization that the risk acceptability criteria do not take into account the risk profiles inherent to the practice.