Failure modes and effects analysis of total skin electron irradiation technique

Total skin electron irradiation (TSEI) is a radiotherapy technique which consists of an homogeneous body surface irradiation by electrons. This treatment requires very strict technical and dosimetric conditions, requiring the implementation of multiple controls. Recently, the Task Group 100 report of the AAPM has recommended adapting the quality assurance program of the facility to the risks of their processes.

A multidisciplinary team evaluated the potential failure modes (FMs) of every process step, regardless of the management tools applied in the installation. For every FM, occurrence (O), severity (S) and detectability (D) by consensus was evaluated, which resulted in the risk priority number (RPN), which permitted the ranking of the FMs. Subsequently, all the management tools used, related to the TSEI process, were examined and the FMs were reevaluated, to analyze the effectiveness of these tools and to propose new management tools to cover the greater risk FMs.

361 FMs were identified, 103 of which had RPN ≥80, initially, and 41 had S ≥ 8. Taking this into account the quality management tools FMs were reevaluated and only 30 FMs had RPN ≥80. The study of these 30 FMs emphasized that the FMs that involved greater risk were related to the diffuser screen placement and the patient's position during treatment.

The quality assurance program of the facility has been adapted to the risk of this treatment process, following the guidelines proposed by the TG-100. However, clinical experience continually reveals new FMs, so the need for periodic risk analysis is required.