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Root Cause Analysis for a Wrong Isocenter Error

N Cao

N Cao*, P Sponseller, F Yang, E Kim, E Ford, University of Washington, Department of Radiation Oncology, Seattle, WA


SU-E-T-288 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: This study is to explore root cause analysis (RCA) in the context of a departmental incident reporting system through a case report of a wrong isocenter. RCA of this incident provides a means to undercover and address underlying causal factors to prevent such an event in the future.

Methods: The wrong isocenter error was detected on port films, making it a near-miss, but the potential impact was severe. Following the modified London Protocol for RCA, we interviewed all the staff involved, including the simulation and treatment therapists, the dosimetrist, the physicist and the physician. A timeline of events leading up to the incident and its discovery was created. We then generated a list of care delivery problems and associated contributing factors. Finally, solutions were identified to address the contributing factors and prevent future recurrences of such an incident.

Results: Though not obvious at the outset of this RCA, the main care delivery problem turned out to be a misidentification of the ball-bearing (BB) location on the treatment planning CT. A metal wire used to mark a drain site was identified as an isocenter mark rather than the BB on the AP surface as intended. Contributing factors include: 1)no policy implemented regarding the location of BBs and metal wire; 2)wires with similar diameter and feature as BBs in CT images; 3)lack of communication when confusion and uncertainties exist. A solution was chosen to help visualize the drain site. When drain site needs to be marked, a marker different from the regular wire will be used (e.g. plastic washer).

Conclusion: Through RCA of an incorrect isocenter placement case, we identified the causal factors and also proposed solutions. RCA is a crucial tool for incident learning. This case study serves as valuable guidance for this particular problem and for RCA more generally.

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