THERP and HEART integrated methodology for human error assessment

Medical errors are one of the leading causes of death and injury in radiation therapy administration as reported in the literature. This point out an overall deficiency in management allowing patient treatment in the absence of suitable quality assurance processes. Clinical records of major accidental exposure events in radiotherapy show that there is a combination of factors contributing to the accident such as deficient staff training, lack of independent checks, lack of quality control procedures, and absence of overall supervision. Another finding is that training generally addresses only normal situations and does not prepare radiotherapy staff for unusual situations, resulting in a lack of a 'safety culture'. In this respect, obviously, it is very important to perform risk analysis to suitably deal with hazards related to human factor with the aim to improve safety standards and to overcome this weakness in all steps of a radiation therapy process. In this paper a new fuzzy assessment model is proposed to evaluate the human factors by using the THERP methodology, a well-known tool based on fault-tree approach for evaluating the probability of errors. Moreover some case study relevant to accidental events leading to potential radiological over-exposure of patients during various radiation treatments are examined by using the proposed new approach to test the validity of the method over the whole range of possible circumstances. The critical analysis of the obtained results allows to provide recommendations and suggestions regarding safety equipment and procedures which can be adopted to reduce the occurrence of accidents. Therefore, the method seems able to solve some problems in conventional Human Error Assessment applications and improve the safety and quality of processes where human errors are the most important cause of accidents.