It was reported to siemens by the siemens service engineer that they were sent to the customer facility to replace a malfunctioning waveguide.After replacement of the waveguide, the service engineer observed that the machine softpots were turned in a way that instead of a 300mu/min dose rate, a dose rate of 360mu/min was being released.After dosimetry calibration of the system by the siemens service engineer, the customer also performed an absolute dosimetry calibration.It was observed that the customer's approach and procedure to perform an absolute dosimetry calibration is not in accordance with siemens' recommendations.Based on the customer's calibration, it is assumed that the dose applied for 6mv is 20% too high and 10% too high for 10mv.It cannot be excluded that patients have been treated by the customer under these conditions received a 20% higher dose than prescribed and recorded in the treatment records.It is unknown to siemens how many patients were treated with a higher dose and for how long the customer's incorrect calibration had been used.Although no mistreatment or injury to patients, staff or service has been reported by the customer, the potential mistreatment risk to patients treated with the incorrect total dose, in a worst-case scenario, has a deviation of 20% for 6mv.The reported event occurred in turkey.
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The event was reported by a siemens field service engineer.Siemens has conducted a detailed technical investigation of the reported event.The root cause is that the customer used a non-siemens approved calibration method.The system instructions for use (ifu) in the physics primer section (t2-000.621.28.05.02, page 17) states the following: "monitor 1 is calibrated to the absolute dose which is usually set at 1cgy/mu for a 10cm x 10cm field size at the appropriate energy depth of dmax (depth of maximum ionization) and at the standard source-to-surface distance (ssd).Note: dose output and dose rate calibration are accomplished by the site physicist in the research mode of the b-softpot page".The customer is responsible for the correct calibration of the system.No mistreatment or injury of a person has been reported by the customer.If additional information becomes available regarding this event, siemens will submit a supplemental report.
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