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  • Electromagnetic Frameless Stereotaxy (EMFS) for Intraoperative MRI – First Report

    Final Number:

    Teresa Kathryn Withers MD; Brendan Davis

    Study Design:
    Clinical Trial

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2016 Annual Meeting - Late Breaking Science

    Introduction: Electromagnetic stereotaxy was adapted as a new technique to allow intraoperative MRI capabilities without the need for cranial fixation to the table. To the best of our knowledge, this has not previously been undertaken and there are no reports in the current literature. Stereotactic localisation has been used to increase safety and planning for complex cranial operations. Intraoperative MRI (iMRI) using a pinning system allows the data to be updated during the procedure so that the data sets remain current thus increasing accuracy, safety and clinical outcomes. However, there are some operations where pinning in a clamp is not desired. This includes transphenoidal surgery, ventriculo-peritoneal shunts, paediatric patients and neuro-endoscopic procedures. We have successfully pioneered a new technique of using electromagnetic (EM) stereotaxy in conjunction with iMRI.

    Methods: Validation of the EM systems safety with the MRI was completed by the manufacturer. There were no anticipated problems in using the patient tracker suckers in conjunction with the Intraoperative MRI system. The technique was validated without complication and then utilised with consent on a case series of transphenoidal operations without the requirement of pinning the head for the procedure.

    Results: The procedures were completed successfully and safely without the need for head fixation. Electromagnetic Stereotaxis allowed accurate localisation and re-registration after an intraoperative scan in all cases. There was no image degradation. The use of the Electromagnetic Stereotaxis provides a safe and cost effective technique as an alternative to using iMRI head fixation.

    Conclusions: Frameless EM Stereotaxy allows safe, reliable and accurate non-invasive surgical navigation in conjunction with iMRI.

    Patient Care: This new technique demonstrates the safe use of Frameless EM Stereotaxy with intraoperative MRI. The ability to reposition the patient intra-operatively and the ability to operate without pinning provides the opportunity to maximise tumour clearance.

    Learning Objectives: By the conclusion of this session participants will identify that Frameless EM Sterotaxy is MRI compatible and allows re-registration during surgery without image degradation.

    References: Advanced cranial navigation. Mert A, Gan LS, Knosp E, Sutherland GR, Wolfsberger S. Neurosurgery. 2013 Jan;72 Suppl 1:43-53. Intraoperative computed tomography registration and electromagnetic neuronavigation for transsphenoidal pituitary surgery: accuracy and time effectiveness. Eboli P, Shafa B, Mayberg M. J Neurosurg. 2011 Feb;114(2):329-35.

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