Author: Victoria Noelle Bry, Tamara Egan, Eric C. Ford, Angelia Landers, Juergen Meyer 👨🔬
Affiliation: Fred Hutch Cancer Center, University of Washington, Department of Radiation Oncology, Fred Hutchinson Cancer Center, University of Washington, University of Washington 🌍
Purpose: Surface guided radiation therapy (SGRT) can improve patient safety, however, its complex integration may expose processes to increased risk of error. This work identifies potential failures for its use at a single institution.
Methods: Physicists and therapists performed a failure modes and effects analysis (FMEA) on clinic workflows using Elekta linacs and C-RAD SGRT. A process map defined scope of use, encompassing 4DCT, tattoo-free setup, deep-inspiration breath hold (DIBH), and real-time monitoring for all SBRT patients (excluding SRS). Team members identified failure modes for each process step and scored according to AAPM TG-100 based on Severity(S), Occurrence(O) and Detectability(D) to determine Risk Priority Number (RPN=S*O*D). The top five RPN-ranked failures were analyzed to determine additional safety checks and mitigation strategies.
Results: 38 failure modes were identified, and the top 5 RPN-scores ranged between 138-203. The top two potential failure modes identified were (1) incorrect breath hold imaging using Cone-Beam CT, as there is no gating interface to imaging systems on linac platforms, for either Elekta or Varian, requiring a technical solution by the vendors or therapists to manually monitor compliance and (2) accepting or setting incorrect baselines for DIBH treatments leading to incorrect breath hold depths. Potential causes were related to lack of technical integration into existing workflows causing human error and variability in chest versus abdominal breathing resulting in different respiratory baselines for DIBH patients. Variability can be minimized through improved coaching, adherence to procedures, and thorough training of therapists. Mitigation strategies implemented include reinforcement of protocols for the radiotherapy team and additional physics checks to monitor changes in respiratory trace or system overrides.
Conclusion: This study highlights complexity of implementing SGRT by identifying risks across workflows. Top failures identified were attributed to lack of gating between SGRT and linac imaging systems and variability in patients' respiratory baselines.