ESTRO 2023 - Abstract Book

S2075

Digital Posters

ESTRO 2023

PO-2307 Applying a System-Theoretic Accident Modeling Process (STAMP) to an Incident in Proton RT

D. Eijssen 1 , S. Schouenberg 1 , N. Silvis 2

1 Maastro Clinic, Limburg, Maastricht, The Netherlands; 2 VU Amsterdam, Noord Holland, Amsterdam, The Netherlands

Purpose or Objective System Theoretic Accident Modeling Process (STAMP), is a new safety analysis method that approaches safety based on systems- and control theory, instead of the traditional reliability theory. The novelty consists in the graphical modeling of the process as a system, in which controllers interact with controlled processes in terms of control actions and feedback. In this holistic view, safety becomes an emerging system property, guarded by safety constraints. In STAMP, accidents happen because the safety constraints were violated, and the controllers that could prevent the accident did not act properly. Accidents are seen as caused not by individual hardware-, software- or human component faults, but by control flaws, be they safety constraints violations or their inexistence. As any other accident analysis methods, STAMP aims to go beyond finding a root cause for an accident and assigning blame. Instead, it tries to understand why accidents happen, and thus learn how to design more robust systems in the future. STAMP promises to better understand modern accidents causality and to discover interesting system hazards, using tools such as Systems Theoretic Process Analysis (STPA), and Causal Analysis based on STamp (CAST). Radiation therapy process is practiced in a complex socio-technical system, and therefore in our opinion very suitable to be analyzed using STAMP. What is the added value of STAMP compared to PRISMA when analyzing a proton incident? Materials and Methods In an attempt to add a contribution to this meager body of knowledge of using STAMP in RT the proton incident is re- analyzed, this time by using STAMP-CAST.

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Narrative description of the incident

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Modeling the RT process using safety control structures

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Analyze each component in the loss

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Identify control structure flaws

Create a safety improvement plan

Results We learned that STAMP found the same major root causes and issues like the PRISMA method. Most important, in our analysis, software emerged as an actor that can prevent but also harm and contribute to an accident. We compared the STAMP recommendation with the recommendation from PRISMA. STAMP could formulate some new recommendations, especially towards players outside the organization. In some cases PRISMA analysis issued more specific safety-related recommendations. STAMP only recommended to dare to speak up. STAMP differs especially in the first modelling phase to detect hazards. Conclusion To start with, we concluded that the main problems and recommendation were similar. To summarize, we believe that STAMP is a useful incident analysis method that can be used along with other method such as FTA or FMEA, especially in large RT organizations or new RT processes without a sound safety management policy. However, the graphical modeling step is still perceived as cumbersome by RT practitioners and this reduces its chances to be adopted. More effort is needed to assist practitioners with the first step of graphical modeling with control structures.

PO-2308 Failure Mode and Effects Analysis for Improving the quality of treatment Planning In Radiotherapy

S. Huang 1 , C. Chang 1 , J. Tsai 1 , W. Chuang 1 , C. Kuo 1 , L. Chen 1 , M. Li 1

1 Shuang Ho Hospital, Taipei Medical University, Radiation Oncology, New Taipei City, Taiwan

Purpose or Objective The purpose of this study is to use the failure mode and effects analysis (FMEA) to identify high-risk failure modes of the treatment planning process and to promote the medical quality and patient safety by improving the planning compliance rate in radiotherapy. Materials and Methods Retrospective analysis was applied to treatment plans in 2020-2022. A process map of the treatment planning including a major process tree and subprocess steps was generated based on the guidelines in TG-100 report. Five major treatment planning process steps were (I) planning parameters, (II) plan quality, (III) image parameters, (IV) MOSAIQ management, and (V) chart documents. Errors detected during or after the PTPCR were identified to failure modes (FMs) in each process step. A risk priority number (RPN=O × S × D) was assigned to each FM by the five physicists based on tabulated scoring system (Table 1) for the frequency of occurrence (O), the severity (S), and the detectability (D) of errors, each on a scale of 1 to 10. The planning compliance rate (= the number of plans without errors the total number of plans × 100%) was calculated