Table 3.
Application of failure mode and effects analysis for the preplanning imaging and volume determination stage in tomotherapy. Failure modes having an assigned are reported
| Subprocess | No | Potential Failure Mode | Potential Causes of Failure | Potential Effects of Failure | O | S | D | RPN |
|---|---|---|---|---|---|---|---|---|
| VIII Positioning/alignment of the patient on the CT couch on the basis of the laser | 1 | Wrong definition of the isocenter | Inadequate CT laser alignment | Systematic shift of the patient position | 4 | 8 | 3 | 96 |
| X Reference markers positioning to indicate previous treatment fields | 2 | Missing marker positions | Lack of attention or incomplete compilation of the RT record | Previous treatment not taken into consideration/suboptimal planning | 4 | 6 | 3 | 96 |
| XXIII Registration of possible other images from different techniques and check of consistency | 3 | Wrong registration | Consistency not verified | Wrong PTV and OAR definition | 3 | 7 | 5 | 105 |
| XXIV Definition of the GTVs and/or CTVs contour on the basis of the anatomical and/or functional information (BTV) | 4 | Wrong CTV definition | Lack of attention/inadequate skill | Wrong dose distribution | 3 | 7 | 5 | 105 |
| XXV Definition of ITV in the case of 4D CT acquisition | 5 | Incorrect ITV construction | Lack of attention/inadequate skill | Wrong PTV | 3 | 6 | 5 | 90 |
| XXVI Automatic contour of the OAR | 6 | Missing OAR definition | Lack of attention/inadequate skill | Unintended normal tissue irradiation | 3 | 8 | 5 | 120 |
| XXVII Manual contour of the OAR | 7 | Missing OAR definition | Lack of attention/inadequate skill | Unintended normal tissue irradiation | 3 | 8 | 5 | 120 |
| XXVIII Defnition of the planning structure at risk through automatic expansion of OAR | 8 | Wrong expansion | Lack of attention/inadequate skill | Unintended normal tissue irradiation | 3 | 5 | 6 | 96 |
| XXIX Automatic expansion with definition of the CTVs and PTVs margins | 9 | Wrong expansion | Lack of attention/inadequate skill | Unintended normal tissue irradiation | 3 | 5 | 6 | 96 |
| XXX Definition and contouring of overlapping regions | 10 | Wrong/missed definition | Lack of attention/inadequate skill or not detailed information on previous treatment | Unintended normal tissue irradiation or wrong dose distribution | 4 | 7 | 5 | 140 |