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.

Radiation therapy is a complex treatment modality involving several technological and professional resources as well as a large number of attributions of these professionals with a high degree of interdependence. Thus there are many possibilities of failure in the treatment process that may lead to an accidental exposure. So regulatory agencies have established guidelines in their regulations in order to prevent accidental exposures through security analysis planning and risk management. The System of EValuation of Risk in RAdiotherapy, also known as SEVRRA, is based on the risk matrix methodology and allows the risk assessment of radiation therapy facilities in a prescriptive way, highlighting events leading to high-risk levels and severe consequences for individuals. With SEVRRA it is also possible to establish an importance analysis of the barriers proposed to avoid or mitigate such events.This work aimed to demonstrate the application of SEVRRA for the risk management of radiation therapy facilities. The risk profile of the facility was determined by identifying the highest risk level events, and the barriers of greater impact for the overall risk level. After implementing some missing barriers in the original facility profile, it was achieved a reduction from 31% to 8% in the number of events leading to high-risk level, showing the effectiveness of SEVRRA for the risk management in radiation therapy facilities.

No abstract

991. Introdução IGRT, acrônimo de image guided radiotherapy, radioterapia guiada por imagem, tem como principais aplicações os tratamentos que requerem extrema precisão de localização, como radiocirurgia estereotática (SRS), radioterapia estereotática de corpo (SBRT) e radioterapia de intensidade modulada (IMRT).A IGRT foi um passo importante na evolução tecnológica da radioterapia, pois trouxe a possibilidade de uma verificação mais cuidadosa da região a ser irradiada, com dispositivos como ultrassom, tomografia computadorizada (CT) de kilo ou mega voltagem (kV ou MV), Cone beam kV ou MV e alta frequência realizados diariamente na sala de tratamento antes do procedimento radioterápico. As imagens tridimensionais de alta resolução obtidas são comparadas, ResumoA radioterapia é uma modalidade de tratamento em constante evolução que procura atingir o seguinte objetivo: irradiar, com precisão cada vez maior, o alvo, poupando ao máximo as estruturas vizinhas. Para alcançar esse objetivo em tratamentos complexos como radioterapia de intensidade modulada (IMRT), radiocirurgia estereotática (SRS) e radioterapia estereotática de corpo (SBRT), surgiu a radioterapia guiada por imagem (image guided radiotherapy -IGRT). Neste artigo, são descritos os princípios de funcionamento e as características dos seguintes principais dispositivos utilizados: Electronic portal imaging, Cone beam, ExacTrac e Calypso. Como todo o sistema que executa procedimentos que envolvem pacientes, os dispositivos de IGRT também precisam ser submetidos a testes de controle de qualidade que garantam a segurança dos pacientes e a precisão dos tratamentos. Para os diferentes dispositivos apresentamos testes com foco na geometria, na qualidade da imagem, no sistema de operação e na segurança. Também são apresentadas a frequência recomendada e a tolerância aceitável. Palavras-chave: radioterapia; controle de qualidade; radioterapia guiada por imagem. AbstractRadiation therapy is a constantly evolving treatment modality seeking to achieve the following goal: to irradiate with increasing precision the target, saving the neighboring structures to the maximum extent. To achieve this goal in complex treatments such as intensity-modulated radiation therapy (IMRT), stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT), image-guided radiation therapy (IGRT) has emerged. This article describes the operating principles, features of the following main devices used: Electronic portal Imaging, Cone beam, ExacTrac and Calypso. Like any system that performs procedures involving patients, IGRT devices also need to undergo quality control tests to ensure patient safety and accuracy of treatments. For the different devices tests with focus on geometry, image quality, operating system and safety are presented. The recommended frequency and acceptable tolerance are also given.