title: Application of systems and control theory-based hazard analysis to radiation oncology.
abstract: OBJECTIVE
  Both humans and software are notoriously challenging to account for in traditional hazard analysis models. The purpose of this work is to investigate and demonstrate the application of a new, extended accident causality model, called systems theoretic accident model and processes (STAMP), to radiation oncology. Specifically, a hazard analysis technique based on STAMP, system-theoretic process analysis (STPA), is used to perform a hazard analysis.
  
  
  METHODS
  The STPA procedure starts with the definition of high-level accidents for radiation oncology at the medical center and the hazards leading to those accidents. From there, the hierarchical safety control structure of the radiation oncology clinic is modeled, i.e., the controls that are used to prevent accidents and provide effective treatment. Using STPA, unsafe control actions (behaviors) are identified that can lead to the hazards as well as causal scenarios that can lead to the identified unsafe control. This information can be used to eliminate or mitigate potential hazards. The STPA procedure is demonstrated on a new online adaptive cranial radiosurgery procedure that omits the CT simulation step and uses CBCT for localization, planning, and surface imaging system during treatment.
  
  
  RESULTS
  The STPA procedure generated a comprehensive set of causal scenarios that are traced back to system hazards and accidents. Ten control loops were created for the new SRS procedure, which covered the areas of hospital and department management, treatment design and delivery, and vendor service. Eighty three unsafe control actions were identified as well as 472 causal scenarios that could lead to those unsafe control actions.
  
  
  CONCLUSIONS
  STPA provides a method for understanding the role of management decisions and hospital operations on system safety and generating process design requirements to prevent hazards and accidents. The interaction of people, hardware, and software is highlighted. The method of STPA produces results that can be used to improve safety and prevent accidents and warrants further investigation.
authors.affiliation: Department of Radiation Medicine and Applied Sciences, UC San Diego, 3385 Health Sciences Drive, La Jolla, California 92093.
authors.forename: Todd
authors.initials: T
authors.lastname: Pawlicki
authors.affiliation: Engineering Systems Division, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02142.
authors.forename: Aubrey
authors.initials: A
authors.lastname: Samost
authors.affiliation: Department of Radiation Medicine and Applied Sciences, UC San Diego, 3385 Health Sciences Drive, La Jolla, California 92093.
authors.forename: Derek W
authors.initials: DW
authors.lastname: Brown
authors.affiliation: Department of Radiation Medicine and Applied Sciences, UC San Diego, 3385 Health Sciences Drive, La Jolla, California 92093.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Manger
authors.affiliation: Department of Radiation Medicine and Applied Sciences, UC San Diego, 3385 Health Sciences Drive, La Jolla, California 92093.
authors.forename: Gwe-Ya
authors.initials: GY
authors.lastname: Kim
authors.affiliation: Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02142.
authors.forename: Nancy G
authors.initials: NG
authors.lastname: Leveson
mesh_terms: D006801:Humans; D018787:Radiation Oncology / Q000379:methods*; D017751:Safety Management / Q000379:methods*