FMEA of manual and automated methods for commissioning a radiotherapy treatment planning system.

PURPOSE

To evaluate the level of risk involved in treatment planning system (TPS) commissioning using a manual test procedure, and to compare the associated process-based risk to that of an automated commissioning process (ACP) by performing an in-depth failure modes and effects analysis (FMEA).

METHODS

The authors collaborated to determine the potential failure modes of the TPS commissioning process using (a) approaches involving manual data measurement, modeling, and validation tests and (b) an automated process utilizing application programming interface (API) scripting, preloaded, and premodeled standard radiation beam data, digital heterogeneous phantom, and an automated commissioning test suite (ACTS). The severity (S), occurrence (O), and detectability (D) were scored for each failure mode and the risk priority numbers (RPN) were derived based on TG-100 scale. Failure modes were then analyzed and ranked based on RPN. The total number of failure modes, RPN scores and the top 10 failure modes with highest risk were described and cross-compared between the two approaches. RPN reduction analysis is also presented and used as another quantifiable metric to evaluate the proposed approach.

RESULTS

The FMEA of a MTP resulted in 47 failure modes with an RPN of 161 and S of 6.7. The highest risk process of "Measurement Equipment Selection" resulted in an RPN of 640. The FMEA of an ACP resulted in 36 failure modes with an RPN of 73 and S of 6.7. The highest risk process of "EPID Calibration" resulted in an RPN of 576.

CONCLUSIONS

An FMEA of treatment planning commissioning tests using automation and standardization via API scripting, preloaded, and pre-modeled standard beam data, and digital phantoms suggests that errors and risks may be reduced through the use of an ACP.