MAUDE Adverse Event Report: ELEKTA LTD PRECISE SERIES LINAC; ACCELERATOR, LINEAR, MEDICAL

Device Problem Calibration Error (1078)

Patient Problem Underdose (2542)

Event Date 04/28/2015

Event Type  Injury  

Event Description

The customer reported that the y2 diaphragm was out of position by 2.5 cm, causing mistreatments.The linac system reported a correlation error and this was followed-up by a service visit to to re-correlate the diaphragm 3-potentiometer system, however the hospital physicist was not present at the time.Subsequently the therapist reported a 2.5 cm shift in the diaphragm offset.This was noticed when a port film was taken after 7 patients had been treated clinically.The calibration of the diaphragm y2 offset was found to be incorrect, and was adjusted with the hospital physicist in attendance.The customer reported mistreatments occurring on (b)(6) 2015 between 9:30am and 11:30am.The y2 (iec1217) diaphragm was out of position by 2.5cm (into field) which resulted in under-dosing seven patients.These involved three vmat treatments and four static field treatments.These could not be replanned for to make up for the under-dose.The customer did run the plans on their phantom prior to the recalibration, so they know exactly what was delivered.

Manufacturer Narrative

The manufacturer reviewed the system rmx logs and audit trail, but this did not yield any evidence of qa testing after the correlation.It was not possible to replicate a diaphragm offset error when saving mlc calibrations.A sudden and large change could be explained by the act of re-learning the correlation, this appears to have re-defined the relationship between the coarse potentiometer and the fine potentiometer which is used for positional readout, resulting in the system referring to the fine-b wiper voltage instead of the fine-a wiper and vice-versa.This incident would be detectable if the accepted practice of performing machine qa following servicing had been applied.The customer's system has been returned to a correct calibrated state for clinical use.The manufacturer's investigation is ongoing.

Manufacturer Narrative

The manufacturer concluded in their final investigation report that they reviewed the system rmx logs and audit trail, but this did not yield any evidence of qa testing after the correlation.This incident would be detectable if the accepted practice of performing machine qa following servicing had been applied.The customer's system has been returned to a correct calibrated state for clinical use.It was not possible to replicate a diaphragm offset error when saving mlc calibrations.A sudden and large change could be explained by the act of re-learning the correlation, this appears to have re-defined the relationship between the coarse potentiometer and the fine potentiometer which is used for positional readout, resulting in the system referring to the fine-b wiper voltage instead of the fine-a wiper and vice-versa.The error of -2.5cm was introduced to the system as a result of two associative events.The source of the error is hardware / software - the basic likelihood is therefore occasional.Following the service activity, a post-service check (performed by fse) and qa check (performed by hospital) should be carried out as procedure and recommendation in prior to the machine returning to the clinical operation.If performance checks are carried out, such error in y2 diaphragm position would be easily detected before any mistreatment happens.As two human errors are introduced to the machine maintenance procedure.The likelihood is reduced from occasional to improbable.Typical case (imrt / vmat hyperfractionated delivery) - moderate x improbable (= acceptable).Service engineer checks at handover should reduce the risk of error when passing control of equipment.Physics qa should confirm that equipment is approved for clinical use.Worst case (srs / hypofractionated delivery) - major x improbable (= tolerable).Mitigations as above, the addition of extra patient-specific qa checks would be unlikely to further reduce the risk of un-detected mis-calibration, as these are done ahead of treatment.On-line kv imaging is used for patient positioning, so the mv field size would be unlikely to be checked during setup.The manufacturer is investigating the options available to ensure this error could not lead to a clinical mistreatment again.They are not aware of similar incidents with this type of medical device with a similar root cause.

Event Description

The customer reported that the y2 diaphragm was out of position by 2.5 cm, causing mistreatments.The linac system reported a correlation error and this was followed-up by a service visit to re-correlate the diaphragm 3-potentiometer system, however the hospital physicist was not present at the time.Subsequently the therapist reported a 2.5 cm shift in the diaphragm offset.This was noticed when a port film was taken after 7 patients had been treated clinically.The calibration of the diaphragm y2 offset was found to be incorrect, and was adjusted with the hospital physicist in attendance.The customer reported mistreatments occurring on (b)(6) 2015 between 9:30am and 11:30am.The y2 (iec1217) diaphragm was out of position by 2.5cm (into field) which resulted in under-dosing seven patients.These involved three vmat treatments and four static field treatments.These could not be replanned for to make up for the under-dose.The customer did run the plans on their phantom prior to the recalibration so they know exactly what was delivered.

• Brand Name: PRECISE SERIES LINAC
• Type of Device: ACCELERATOR, LINEAR, MEDICAL
• Manufacturer (Section D): ELEKTA LTD; linac house; fleming way; crawley, west sussex RH10 9RR; UK RH10 9RR
• Manufacturer (Section G): ELEKTA LTD; linac house; fleming way; crawley, west sussex RH10 9RR; UK RH10 9RR
• Manufacturer Contact: gpms ; linac house; fleming way; crawley, west sussex RH10 -9RR ; UK RH10 9RR
• MDR Report Key: 4800876
• MDR Text Key: 5921341
• Report Number: 9617016-2015-00007
• Device Sequence Number: 1
• Product Code: IYE
• Combination Product (y/n): N
• Reporter Country Code: US
• PMA/PMN Number: K051932
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: Other,Health Professional,User Facility,health professional
• Reporter Occupation: Health Professional
• Remedial Action: Modification/Adjustment
• Type of Report: Initial
• Report Date: 09/01/2015

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 05/28/2015
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: No
• Device Operator: Health Professional
• Was Device Available for Evaluation?: Yes
• Is the Reporter a Health Professional?: Yes
• Date Manufacturer Received: 04/29/2015
• Was Device Evaluated by Manufacturer?: Yes
• Is the Device Single Use?: No
• Is This a Reprocessed and Reused Single-Use Device?: No
• Type of Device Usage: Reuse
• Patient Sequence Number: 1
• Patient Outcome(s): Other