Table 1 Application of failure mode and effects analysis for the treatment planning stage in proton beam radiotherapy
Sub-process | Potential failure mode |
|---|---|
(III) Manual correction of external contour | Lack of removal of metallic skin markers |
(V) Localization of the origin of coordinates identified by lasers | Incorrect localization of the origin of coordinates identified by lasers (small amount, 1–2 mm) |
Incorrect localization of the origin of coordinates identified by lasers (large amount) | |
(VIII) Transfer of definitive isocenter coordinates to movable lasers if different from the origin of coordinates | Lack of information transfer (no virtual simulation) |
Wrong data transfer | |
Overwrite of file data | |
(XI) Target selection and dose prescription setting for each target (dose prescription type - point or volume, mean, median, minimum, - total dose, - fractionation scheme) | Incomplete target selection |
Wrong target selection | |
Wrong target dose prescription | |
(XIII) Assignment of targets to the field | Incomplete or wrong target assignment |
(XIV) Field isocenter position setting | Incorrect isocenter definition |
(XV - XVI) Selection of field direction (gantry angle and couch rotation) | Improper selection of gantry angle/couch rotation: tissue interfaces lying parallel to beam direction, when otherwise avoidable (i.e. when more robust alternative geometry would be feasible) |
Improper selection of gantry angle/couch rotation: not reachable position (potential collision or movement limitations) | |
(XVII) Setting of pencil beam parameters: | Â |
- Full Width Half Maximum (FWHM) | Improper selection of beam parameters: FWHM, scanning or energy step too low in relationship to the PTV volume |
- scanning step in the transversal plane | |
- energy step | |
- passive elements (range shifter and ripple filter) | |
(XVIII) Selection of the physical and biological database for dose calculation | Selection of unapproved (i.e. not validated for clinical practice, for experimental use only) database. |
(XX) Setting of the optimization modality (SFUD, IMPT) | Improper setting of the cost function parameters |
Improper selection of optimization modality rather than IMPT | |
(XXVII) Evaluation of the best plan | Improper selection of the best plan among the competing calculated onces in terms of optimal trade-off between plan quality (PTV dose coverage versus OAR sparing) and robustness |
(XXVIII) Creation of set-up fields and calculation of DRRs | Wrong definition of field isocenter (large amount) |
Improper selection of parameters for DRR calculation | |
(XXXI) Selection of the phantom for the verification plan | Improper phantom selection |