Probability of Human Errors in Operation of Treatment Planning System (TPS)

Abstract

To prevent the unexpected human errors occurred in various stages, the cooperation of all of the staffs is necessary. In our hospital, the robust QA program to prevent the human errors in operation of the treatment planning systems (TPS-stage) has been implemented and used for a long time. A large number of the treatment plans were analyzed to reveal the event and error frequency. Additionally, the possible causes of the errors and possible effective countermeasures were considered. In our hospital, the treatment plans made mostly by radiation oncologists are checked by two medical physicists using a chart check implemented in an electronic health record system. If the physicist detects the errors in TPS-stage, the detector completes the near-incident and incident report, and these reports are submitted to monthly radiation safety conference. All of the staffs involved in radiation therapy attend the conference and information of the new errors and the possible countermeasures will be informed to all the staffs. The 5513 treatment plans between May 2007 and December 2011 were checked before the treatments. Of the 5513 treatment plans, all of the 376 errors were detected before the actual delivery of irradiation. Average error probability of 7% was obtained. That means that, approximately 7 out of 100 treatment plans have something wrong in the TPS-stage: Table shows the errors with a higher probability. “MLC/Jaw” is one relating to mis-setting the field size with the collimator jaws and multi-leaf collimators (MLC). “Dose/fraction” is one relating to mis-setting dose and fraction, e.g., prescribed dose is not equal to the sum of dose of each field. “Isocenter/Reference point” is one relating to mis-locations of isocenter and reference point (not ICRU prescription, etc). Some examples of countermeasures are the feedback of these results to the planner to prevent the errors, the training for the staffs, and the utilizing manual describing the pit-falls in the operation of the TPS. It is more important to establish the system of completely detecting the unexpected errors by “Robust QA program”. The errors in the TPS-stage should be shared with not only the radiation oncologists as planners, but also with medical physicists and radiation technologists, and the other staffs involved in radiation therapy, which lead to create “safety culture” in the department.Poster Viewing Abstract 3456; TableClassification of the 372 errors in 5513 treatment plansErrorProbabilityNumber of eventsJaw/MLC1.5%83Machine ID1.2%65Dose/fraction0.9%49Isocenter/Reference point0.8%42Bolus0.2%12Algorithm0.2%11Heterogeneity correction0.2%10Others1.8%100Total6.7%372 Open table in a new tab