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A Risk Bias Weighted Approach to FMEA for An Adaptive Radiation Therapy Workflow

N Islam1*, R Lalonde1, S Jang1, M Huq1, (1) UPMC Hillman Cancer Center and University of Pittsburgh School of Medicine, Pittsburgh, PA


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Radiation Therapy techniques present new challenges when developing effective quality assurance procedures. The failure modes (FM) in the workflow of Varian’s Ethos Adaptive Radiation Therapy platform have been analyzed by considering evaluator experience and risk bias.

Methods: workflow for Ethos was outlined and potential FMs were identified. A Failure Modes and Effects Analysis (FMEA) approach that incorporates the experience and risk bias of evaluators was applied. The risk bias of evaluators was assessed by considering the particular role of the individual in the clinic and relative experience level. Each FMEA evaluator provided: (1) Score of occurrence (O), severity (S), and detectability (D), (2) Self-assessment of Experience level and Risk Bias. The final risk priority number (RPN) for each FM is calculated using O, S, D while factoring in evaluator specific weighting factors corresponding to experience and risk bias. The data collected in this study is prospective and in preparation for future commissioning of Ethos.

Results: total of 8 steps were identified in the Ethos workflow which included auto-contouring, deformable registration, dose calculation, adaptive plan generation and quality assurance. Furthermore, 22 potential causes of failures and effects were identified at various stages of the workflow. Data was collected from FMEA team members in order to calculate experience and risk bias weighted RPN values for each FM. Weighted RPN values ranged from 32.7 – 1412.7, while conventional RPN ranged from 15 – 743. The relative rank of FMs were compared between weighted RPN approach and conventional RPN.

Conclusion: experience and risk bias weighted approach to FMEA provides a more comprehensive evaluation compared to conventional FMEA. The process map outlining the Ethos adaptive radiation therapy workflow with the potential FM RPNs will be valuable when commissioning adaptive radiation therapy technologies and implementing quality management procedures that mitigate potential FMs.

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Funding Support, Disclosures, and Conflict of Interest: This work is supported by Varian Medical Systems.


Quality Control, Risk, Radiation Therapy


TH- External Beam- Photons: adaptive therapy

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