Which failures do patient-specific quality assurance systems need to catch?

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Developing a quantitative framework for evaluating radiotherapy treatment verification systems.
• Identifying potential failure modes with the greatest risk to patient treatment quality and safety.

Purpose of the Study:

• Create a database of radiotherapy failure modes detectable by patient-specific quality assurance (PSQA).
• Determine the relative importance of these failure modes for maximizing treatment quality.

Main Methods:

• Conducted a failure-mode-and-effects analysis (FMEA) on 394 error reports, categorized into 33 failure modes.
• Assessed severity (S), occurrence (O), and detectability (D) for each failure mode.
• Analyzed risk priority number (RPN = O*S*D), O*S, and severity rankings to prioritize failure modes.

Main Results:

• Five failure modes ranked highest in both RPN and O*S analyses, primarily involving treatment planning system (TPS) commissioning and patient model errors.
• Highest RPN modes included TPS algorithm limitations and commissioning errors (MLC, output factor, PDD/TMR, off-axis factor).
• Severity analysis highlighted MLC sequence deletion, collision, and TPS isocenter errors as critical.

Conclusions:

• A prioritized list of failure modes critical for PSQA detection has been developed.
• The findings underscore the need for diverse treatment verification systems in PSQA to detect a wide range of errors.
• PSQA is crucial for detecting top-quartile failure modes, preventing undetected errors and optimizing clinical workflows.