[A Human Factors Study Using VTA for Incident Cases in Radiotherapy].

In recent years, workload has increased with higher precision of radiotherapy. Although both efficiency and thoroughness of treatment are crucial, in such conditions, human error is easy to occur. In this study, five incident cases that occurred in four facilities were studied and analyzed from the viewpoint of human factors that contribute to errors using variation tree analysis. We also analyzed resilience (the ability to return to one's original state even if the system deviates from a stable state), which has attracted attention in recent safety research. There were potential factors represented by patient factors in all cases. These factors caused deviations from standard operations, and incidents occurred due to unfamiliar situations and operations. Furthermore, in four of the five cases, the cause of the incident was a resilience action or judgment that was deemed to have required "some sort of ingenuity or adjustment." It was found that human error occurred due to multiple simultaneous occurrences of potential factors, i.e., patient and human factors such as high workload, impatience, and work interruptions. A reduction in human errors can be achieved by avoiding time pressure and multitasking, creating work environment and working conditions that make resilience work well, revising ambiguous rules and procedures, and promoting standardized working methods.