SU-E-T-599: Patient Safety Enhancements Through a Study of R&V System Override Data




Record and verify (R&V) software systems include safety checks that compare actual machine parameters with prescribed values for a patient's treatment, such as treatment couch position, linac, energy, and MUs. The therapist is warned of a mismatch with a pop-up and prompted to approve an override in order to continue without changes. Override approval is often legitimate, but the pop-up can also genuinely indicate a problem that would Result in the wrong treatment. When there are numerous pop-up warnings, human nature leads us to approve any override without careful reading, undermining the effectiveness of the safety mechanism.


Override data was collected from our R&V system for all patients treated between October 8 and 29, 2012, on four linacs and entered into a spreadsheet. Additional data collected included treatment technique, disease site, immobilization, time, linac, and whether localization images were obtained. Data were analyzed using spreadsheet tools to reveal trends, patterns and associations that might suggest appropriate process changes that could decrease the total number of overrides.


76 out of 113 patients had overrides. Out of the 944 treatments, 599 override items were generated. The majority were due to couch positions. 74 of the 84 overrides on a linac equipped with a 6D couch were due to the use of the rotational corrections and the fact that the 6D couch control does not communicate with the R&V system; translations required to rotate the couch appear to the R&V system as translations outside the tolerance range.


Many findings were interesting but did not suggest a process change. Proposed process changes include creating site-specific instead of just technique-specific tolerance tables for couch shifts. Proposed improvements to the vendor are to facilitate direct communication between the 6D couch and the R&V system to eliminate those override warnings related to lack of communication.