Table 2.

Failure modes that are treatment machine dependent

No.	Step	Potential failure modes	Potential causes of failure	Potential effects of failure	Machine	Notes and examples of causes and failures
13	Frame cap/adapter test	Distorted frame adapter	1. Lack of standardized procedures 2. Personnel omission	Inconvenience (staff and patient)	Perfexion	The frame adapter for Perfexion is bad but not found out before a treatment. Treatment can not proceed.
65	Frame adapter attachment	Frame adapter not attached properly	1. Inadequate training/orientation 2. Personnel omission	Inconvenience Inaccurate dose delivery	Perfexion	On the Perfexion, the frame adaptor should be attached properly. Failure to do so may result in an interruption in the treatment process or an imperfect dose delivery. Elekta has a field notice about this.
59	Chart finish‐up	Unnoticed plugged pattern	1. Miscommunication 2. Lack of standard procedures.	Very wrong dose Very wrong dose distribution Very wrong volume	4C	A plug pattern is used on 4C but the hard copy does not show it, either because of an incorrect printout selection or a breakdown of the printer. Treatment proceeded without the plug pattern.
72	Final check	Wrong plug pattern	1. Personnel omission 2. Lack of double check	Wrong dose distribution	4C	The plug pattern is not put in correctly on 4C.
73	Final check	Inserts/Plugs not secured	1. Personnel omission 2. Lack of double check	Interrupted treatment	4C	An insert or plug is not firmly attached to a helmet. The insert/plug drops during a treatment. Cause the treatment to stop.
82	Treatment monitoring	Poor choice of treatment sequence	Poor user choice	Ineffective treatment process	4C	On 4C, when multiple helmets, multiple Gamma angles, high/low docking are involved, it is necessary to figure out a treatment sequence that minimizes the treatment time.
12	Frame positioning/fixation	Inappropriate frame placement	1. Lack of training/experience 2. Miscommunication	Inconvenience (staff and patient)	Both	The stereotactic frame is not shifted correctly when treating a peripheral lesion. A collision with the helmets (on the 4C) or the source cap (on the Perfexion) is reported from the planning system. Frame and imaging need to be repeated.
67	Lock patient	Incorrect patient setup	Personnel omission	Very wrong dose distribution	Both	Patient setup with wrong stereotactic coordinates in the trunnion mode. Patient setup at a wrong Gamma angle. On the Perfexion treatment can not start with a wrong Gamma angle.
68	Lock patient	Patient head position not firmly fixed	1. Bad equipment 2. Personnel omission	Wrong dose distribution	Both	It is good practice to check if the patient head is fixed properly before a treatment. Equipment failure, untighten or loose screws may cause unsecured patient head position. This is more important for the trunnion mode on the 4C.
78	Treatment monitoring	Treated shots not recorded correctly	1. Lack of standard procedure 2. Procedure not followed 3. Personnel omission	Very wrong dose Very wrong dose distribution	Both	Delivered shots are not followed closely and recorded correctly on the treatment copy. Cause confusion in the shots that have been delivered. This happens more likely on 4C with trunnion shots.