Failure modes and effects analysis applied to high-dose-rate brachytherapy treatment planning

To apply failure modes and effects analysis to high-dose-rate treatment planning to identify the most likely and significant sources of error in the process.

We have made a list of 25 failure modes grouped into six categories (imaging, catheter reconstruction, dwell position activity, dose points/normalization, optimization/dose, and evaluation). Each mode was rated on a one to five scale for severity, likelihood of occurrence, and probability of escaping detection. An overall ranking was formed from the product of the three scores. The authors assigned scores independently and the resulting rankings were averaged. We also analyzed 44 reported medical events related to high-dose-rate treatment planning listed on the Nuclear Regulatory Commission Web site and compared them with our own rankings.

Failure modes associated with image sets, catheter reconstruction, indexer length, and incorrect dose points had the highest ranking in our analysis (scores higher than 20). The most often cited failure modes in the Nuclear Regulatory Commission reports examined were indexer length (20/44) and incorrect dose points (6/44). Several of our high-ranking modes are not associated with reported events.

It is a useful exercise to identify failure modes locally and analyze the efficacy of the local quality assurance program. Comparison with nationally reported failures can help direct the local analysis, but the absence or small number of reports for failure modes with a high score may be owing to low detectability. Such modes obviously cannot be ignored.