Unique identifier (udi) #: (b)(4).A full analysis of the logs and of the patient folder has been performed.The ten electrodes have been implanted with an inaccuracy superior to 2 mm at their entry point.The different deviations of the electrodes do not allow to identify a trend.One of the possible explanation to the deviations that have been observed is that the registration performed was not sufficiently accurate.This can be due to the fact that a 3t mri was used as 3d reference for the laser registration (which is not recommended in the ifus due to the risk of distortion of the image) or to the fact that the user did not recollect a point with the robot arm after he adjusted its position on the image.The user also validated the laser registration although an insufficient number of points matched.Finally, the numerical results of the verification showed that three of the eight verified points had an error distance exceeding the threshold and triggered a warning message.Because the verification screenshots were not available, it is impossible to confirm that the verification was performed correctly which would have ensured that the registration was accurate.However, it is not possible to conclude that the incorrect registration caused the deviations at the entry point of the ten electrodes.Based on the investigation performed, the technical root cause of the event was determined to be use error - use of a 3t mri as reference.
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This was an issue that was brought up by surgeon regarding using mri for laser registration.This site along with the company representative have been using the mri images to register patients for seeg.The surgeon brought up that his bolts were displaced vertically relative to his plan.During the post op scan, he would see that the bolt was placed a few mm away from where he initially planned.All bolts appear to be placed with this error.The surgeon requested more information into why this error is occurring.He is aware that our company does not recommend using mr for laser registration, but he would like to know why his accuracy is affected regardless.If needed, he will switch to using a ct.
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