TABLE 1.
Cohort 1 failure modes and effects analysis (FMEA) results, showing average O, S, D, and risk priority number (RPN) scores
| Process step | Potential failure mode | Potential cause of failure | Occurrence (O) | Potential effects of failure | Severity (S) | Detection methods‐current controls | Detectability (D) | RPN = (O) (S)(D) | Recommended action |
|---|---|---|---|---|---|---|---|---|---|
| Set up with FB DICOM surface | Patient within SGRT tolerance but not positioned correctly | SGRT tolerance too wide due to incorrect site or tolerances adjusted at linac | 4.7 | Treatment not delivered accurately | 7.2 | Immobilization, table tolerances, SSDs, physics pretreatment QA, imaging | 2.8 | 95 |
Establish protocol: physics review FB versus DIBH AP SSDs per patient and adjust tolerances as needed prior to start date Checklist: create Aria Encounter to aid in process |
| Patient within SGRT tolerance but not positioned correctly | SGRT fooled: not enough landmarks in ROI | 5.0 | Treatment not delivered accurately | 6.7 | Immobilization, table tolerances, SSDs, physics pretreatment QA, imaging | 3.3 | 111 | Checklist: create therapist daily Aria Encounter to verify ROI; add to physics weekly encounter to verify ROI | |
| Pull up correct SGRT surface (DICOM or VRT) | Use DICOM mistakenly instead of VRT surface | Imaging form not updated from DICOM; patient moved to other linac | 5.7 | Treatment not delivered accurately | 5.8 | Imaging form, imaging | 3.0 | 99 |
Computerization: map network drive and train therapists how to move files between linacs Checklist: create log to track which patients moved and if images taken |
| Capture new VRT surface if shifts from imaging | Patient moves or breathes during process | Patient discomfort | 5.2 | Treatment not delivered accurately | 5.3 | SGRT, visual inspection of patient, imaging | 4.2 | 115 | Establish protocol: change imaging policy to require one therapist to watch patient while the other captures VRT surface; take verification port after all shifts to verify VRT surface |
| Daily bolus surface captured during DIBH | Patient moves or breathes during process | Patient discomfort | 4.7 | Treatment not delivered accurately | 5.2 | SGRT, visual inspection of patient, imaging | 4.0 | 96 | Barrier: investigate using rigid bolus to avoid daily VRT captures |
| Bolus capture taken with incorrect surface chosen (DIBH or FB) | Labels incorrect or confusing | 4.0 | Treatment not delivered accurately | 5.7 | Dates and appearances of SGRT surfaces | 4.2 | 94 |
Labels: standardize labeling and order of appearance in SGRT; standardize plan order on linac console Checklist: physics to check coincidence of shifts and imaging form changes during weekly QA |
|
| Bolus capture taken with incorrect surface chosen (DIBH or FB) | Lack of attention | 4.7 | Treatment not delivered accurately | 5.5 | Dates and appearances of SGRT surfaces | 4.3 | 111 |
Barrier: investigate using rigid bolus to avoid daily VRT captures Checklist: create therapist daily Aria Encounter to verify ROI |
Abbreviations: AP, anterior‐posterior; DIBH, deep inspiration breath‐hold; DICOM, surface created from treatment planning CT; FB, free breathing; QA, quality assurance; ROI, region of interest; SGRT, surface‐guided radiation therapy; SSD, source surface distance; VRT, vision RT generated surface.