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Safety-Oriented Design of In-House Software for Translating New Techniques From Research to Clinical Practice: A Case Study Using a Model-Based 4DCT Protocol

D O'Connell1*, D Thomas2 , J Lewis3 , N Agazaryan4 , M Cao5 , S Tenn6 , P Lee7 , D Low8 , (1) University of California Los Angeles, Los Angeles, CA, (2) University of Colorado, Denver, CO, (3) UCLA School of Medicine, Boston, MA, (4) UCLA School of Medicine, Los Angeles, CA, (5) UCLA School of Medicine, Los Angeles, CA, (6) UCLA, Torrance, CA, (7) UCLA, Los Angeles, California, (8) UCLA, Los Angeles, CA


(Tuesday, 7/31/2018) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 5

Purpose: In-house software is commonly employed to implement new imaging and therapy techniques before commercial solutions are available. Risk analysis methods, as detailed in the TG-100 report of the AAPM, provide a framework for quality management of processes but offer little guidance on software design. In this work, we examine a model-based 4DCT protocol using the TG-100 approach and describe additional methods for promoting safety of the associated in-house software.

Methods: To implement a previously published model-based 4DCT protocol, in-house software was necessary for tasks such as synchronizing a respiratory signal to images, deformable image registration, model parameter fitting, and interfacing with a treatment planning system. A process map was generated detailing the workflow. Failure modes and effects analysis (FMEA) and fault tree analysis (FTA) were performed to identify critical steps and guide quality interventions. Software system safety was addressed through writing ‘use cases’, narratives that characterize the behavior of the software, for all major operations to elicit safety requirements. Safety requirements were codified using the easy approach to requirements syntax (EARS) to ensure testability and eliminate ambiguity.

Results: 61 failure modes were identified and assigned risk priority numbers using FMEA. The highest risk failure modes were addressed by integrating a comprehensive reporting and logging system. Use cases and resulting safety requirements informed the design of needed in-house software as well as a suite of tests performed during the image generation process.

Conclusion: TG-100 methods were used to construct a process-level quality management program for a 4DCT imaging protocol. Two supplemental tools from the field of requirements engineering facilitated elicitation and codification of safety requirements that informed the design and testing of in-house software necessary to implement the protocol. These general tools can be applied to promote safety when in-house software is needed to bring new techniques to the clinic.


Not Applicable / None Entered.



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