H6 updated h10 updated: the investigation was completed by conducting a thorough evaluation of the product and the reported information.The customer reported that field a1.1 was treated outside of the tolerance position.This did not prompt the user to override the couch position and no indicator was shown that this was treated outside of the 1.0 tolerance in mosaiq.The investigation found that from the logs files field a1.1 has a prescribed couch angle of 355.0, and the tolerance defined in mosaiq is 1.0 degree for couch angle.Couch positions and other parameters must be either within tolerance or overridden before the sequencer can proceed to a ready state for treatment delivery.For the treatment of field a1.1, a ready state was entered, and the couch positions were not shown to have been overridden.According to the historic treatment record, the beam was delivered with the couch angle at 357.0 and outside the 1.0 tolerance.Further investigation have found that there might be rare occasions where the couch angle stops in a position that lies at the edge of the defined tolerance.This makes it possible for couch angle to be seen within tolerance prior to beam on and then seen as out of tolerance after beam on starts if the couch angle was teetering between 356 and 357.In-house testing was performed by elekta with an emulator, and the couch angle was appropriately flagged in mosaiq when out of tolerance and cleared while actual couch angles were within tolerance.The customer also tried to create scenarios where mosaiq would fail to display an out of tolerance flag for a couch angle known to be out of tolerance, but the deliberate attempts were unsuccessful.The customer has a 1.0-degree tolerance defined for couch angle in mosaiq while the linac has a tolerance of 2.0 degrees for couch angle.It is recommended that the linac tolerance for couch angle also be defined to match the 1.0-degree tolerance in mosaiq since mosaiq doesn't do verification or interrupt the beam while the beam is on.Only the user and the linac can stop treatment once it is started.There was no product malfunction, all subsystems are working as designed and intended.The treatment parameters were within the tolerances specified by the controlling subsystem during each work flow step.There was no actual mistreatment.
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