Click here to


Are you sure ?

Yes, do it No, cancel

A System Theoretic Process Analysis for High-Dose Rate Tandem and Ovoid Brachytherapy

A Pegram*, A Yock, Vanderbilt University Medical Center, Nashville, TN.


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: To perform risk analysis on a high-dose rate brachytherapy (HDR) tandem and ovoid treatment by implementing system theoretic process analysis (STPA) methodology.

Methods: STPA was performed to evaluate a current HDR brachytherapy tandem and ovoid treatment process. Types of accidents to be avoided in the process along with hazards that could lead to these accidents were identified. Constraint requirements were created to ensure these hazards were avoided. The control structure of the procedure was analyzed at multiple orders of complexity, from high-order structures comprising broad controllers and broad control actions, e.g. “Planning� and “Delivers Treatment Plan,� respectively, to low-order structures comprising specific controllers and control actions, e.g. “Medical Physicist� and “Turns Console Key.� Control actions from all control structures were analyzed using four conditions wherein they would be considered unsafe: providing control action causes a hazard, not providing a control action causes a hazard, incorrect timing of control action causes a hazard, and stopping a control action too soon or too late causes a hazard. Causal factors and control flaws were identified by interpreting the hazardous scenarios arising from the unsafe control actions.

Results: The four types of accidents identified in this STPA included patient overdose, patient under dose, excessive personnel exposure, and excessive public exposure. Fifteen hazards were identified, and used to establish 8 safety constraints. The control structure analysis resulted in 196 unsafe scenarios. These unsafe scenarios provided insight into the control flaws and causal factors to be considered when establishing and improving upon the safety of an HDR tandem and ovoid protocol.

Conclusion: With STPA, it was possible to analyze the components and interactions of an HDR tandem and ovoid treatment. STPA elucidated potential points of failure within the system that were not already clearly addressed and validated much of the current safety protocol.


Risk, Brachytherapy, HDR


TH- Brachytherapy: GYN brachytherapy

Contact Email