Safety evaluations by means of the method use of the risk matrix in radiotherapy treatments

The quality of a radiotherapy treatment is linked to multidisciplinary factors that need to be taken into account in combined form whenever an evaluation of the safety is carried out. Knowing the accidents happened in this area, and to guarantee their prevention, the causes and sequences that could behave to them should be controlled, for what is necessary to make periodic evaluations of the same one. Our objective was to carry out the safety evaluation to the treatment process of a radiotherapy service and to identify the causes and consequences that can cause these accidental exposures, for patients, worker or people, from the equipment installation until the treatment completion. The method of Risk Matrices was used, by means the SEVRRA system carried out by the Comision Nacional de Seguridad Nuclear y Salvaguardias of Mexico; this system allows to carry out a combined analysis of the occurrence frequency of the event initiator, the probability of human errors or barrier failures and the graveness of the consequences, facilitating the identification of the associated risk to the radiotherapy procedures. The method establishes priorities for the risk administration and identifies the main causes that could cause accidental exposures; also allows preventing the accidents occurrence using risk criterions that take into account the probability and magnitude of the potential exposures. This method, although does not allow to quantify numerically the risk, makes possible to classify it in levels, what is enough to establish priorities, without carrying out risks analysis but precise but more expensive. As a result we obtained that for the Co60 77% of the treatments, is realized with low or half risk and 23% with high risk; the work load that is elevated in our case, intervenes directly in 46 initiators, in second and third place, the non realization of a portal image in the first treatment section and in the weekly continuation, as a consequences reducer, but these are not events with catastrophic consequences, except the related with the manual planning of treatments. Of all the events that were analyzed only one had incidence for the worker. For the Linac only 7% represents the high risk, and it does not have relationship with events of serious or catastrophic consequences; not to have the dosimetry in vivo is the barrier that more contributes it, either in the first treatment session or in the weekly continuation, the other of more influence is not to have a programmed maintenance program as frequency reducer. We can conclude that the safety evaluation to the service was carried out and were identified the main causes that could cause accidental exposures, also we continue working on the vulnerable points related with the treatment that it offers, in order to diminish the initiators with high risk and to guarantee that those that were evaluated with half risk do not evolve to the superior category. The work demonstrated that the human errors are the main cause that can unchain an accidental sequence of high risk. (Author)