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Table 2 Discription of 10-point scales used to derive values of probability, severity, and detectability for each failure mode

From: Evaluation and improvement the safety of total marrow irradiation with helical tomotherapy using repeat failure mode and effects analysis

RankOccurence(O)Severity(S)Detectability(D)
1Very low;
less than 2%
No effectVery easy to detect; alomost never miss
2Inconvenience;
discomfort or distress
3Low;
approximately 5%
Easy to detect, double check should be performed
4Minor dosimetric error;
approximately 5%
5ModerateLimited toxicity or underdose; 10% dose difference with insufficient accutacyModerate, a “lucky catch”
6Medium; occasional failureVery difficult to detect a subtle error in mechanical position or highly unusual situation, e.g., treatment table auto setup error
7Serious toxicity or underdose; 20% dose difference, wrong site irradiation
8High;
repeated failures
9Very serious toxicity; patient injury or deathAlmost impossible to detect
10Inevitable