PurposeThe purpose of this study was to qualitatively, compare, and understand why perceptions of errors in radiation therapy differ from actual reported errors. MethodsThe qualitative study consisted of one-on-one semi-structured interviews that were conducted with three radiation therapists and two medical physicists. Eight interview questions were based on the discrepancies that existed between perceptions and actual error reports from a survey administered in 2010. Interviews were voice recorded and transcribed followed by three independent thematic analyses. Saturated themes were those that were shared across all respondents. Interpretation of these results was based on the literature of perception psychology in an attempt to understand why such perceptions existed or differed from actual reports. ResultsThe thematic analyses revealed that workload, documentation, motives, continuing education, and expectations were recurring themes. The effects of workload were attributed to the psychology of attention and an overburdened filtration process. It is common to find irrelevant distracters or stressors functioning as noise, which make it more difficult to identify and attend to important information. Many forms of stress such as workload, personal, or environmental can function as noise hindering the filtration process, which has been positively associated with therapist burnout. Respondents shared views on redundancy and consistency of documentation. In the literature, adaptation has been shown to play a major role in the formation and alteration of perceptions. Habituation is a form of adaptation that refers to a lessened degree of sensitivity to any one continuous stimulus. Adapting to an environment with a persistent stimulus can result in a passive frame of mind effectively dismissing the redundant stimulus. It is apparent that with redundant documentation, staff members may find themselves habituated with the process of continually transcribing from one document to the next and therefore, making documentation more prone to error. Motives were found as a common theme when respondents were asked to explain why treatment delivery was the area perceived to be where most errors occur, when in reality this was not true. Respondents expressed the onus of responsibility on therapists at the treatment delivery level. The driving force for this perception is the psychological effect of an individual's motives and the physical consequences of errors at the treatment delivery level. Bolus was perceived to be a greater error than it actually is. From the perspective of the “self-fulfilling prophecy” theory by Robert K. Merton, it would state that radiation therapy staff perceived bolus to be a common error because they expected it to be a common error. Expectations of bolus indicated were its subjectivity of placement, the uncertainty of its error, and its lack of an active interlock system. ConclusionsEmergent themes from this study have shown the implications and value of a qualitative approach in providing detail rich information and insight for further research of radiation therapy error analysis. Specifically, referencing the literature of perception psychology, we were able to theorize why therapists perceive certain errors to be more common than others and what factors may influence these perceptions. Future large scale studies in radiation therapy of this nature would benefit the field in helping to create reflective policies and procedures to ultimately minimize human errors and broaden our approach to error analysis.