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Analyzing the Safety Implications of a Brachytherapy Process Improvement Project Utilizing a Novel System-Theory-Based Hazard-Analysis Technique

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A Tang

A Tang1*, A Samost1 , A Viswanathan2 , R Cormack2 , A Damato2 , (1) Massachusetts Institute of Technology, Cambridge, Massachusetts, (2) Dana-Farber Cancer Institute - Brigham and Women's Hospital, Boston, MA.


WE-G-BRA-7 (Wednesday, July 15, 2015) 4:30 PM - 6:00 PM Room: Ballroom A

To investigate the hazards in cervical-cancer HDR brachytherapy using a novel hazard- analysis technique, System Theoretic Process Analysis (STPA). The applicability and benefit of STPA to the field of radiation oncology is demonstrated.

We analyzed the tandem and ring HDR procedure through observations, discussions with physicists and physicians, and the use of a previously developed process map. Controllers and their respective control actions were identified and arranged into a hierarchical control model of the system, modeling the workflow from applicator insertion through initiating treatment delivery. We then used the STPA process to identify potentially unsafe control actions. Scenarios were then generated from the identified unsafe control actions and used to develop recommendations for system safety constraints.

10 controllers were identified and included in the final model. From these controllers 32 potentially unsafe control actions were identified, leading to more than 120 potential accident scenarios, including both clinical errors (e.g., using outdated imaging studies for planning), and managerial-based incidents (e.g., unsafe equipment, budget, or staffing decisions). Constraints identified from those scenarios include common themes, such as the need for appropriate feedback to give the controllers an adequate mental model to maintain safe boundaries of operations. As an example, one finding was that the likelihood of the potential accident scenario of the applicator breaking during insertion might be reduced by establishing a feedback loop of equipment-usage metrics and equipment-failure reports to the management controller.

The utility of STPA in analyzing system hazards in a clinical brachytherapy system was demonstrated. This technique, rooted in system theory, identified scenarios both technical/clinical and managerial in nature. These results suggest that STPA can be successfully used to analyze safety in brachytherapy and may prove to be an alternative to other hazard analysis techniques.

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