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  • Accuracy of Patient Registration: Avoiding Use of Multiple Bone Fiducials

    Final Number:

    David J. Donahue MD; Laurie Bailey MD; M. Scott Perry MD; John Honeycutt MD

    Study Design:

    Subject Category:

    Meeting: 2018 ASSFN Biennial Meeting

    Introduction: RATIONALE: Although the robot can be registered to the patient using surface landmark identification, we have come to prefer the accuracy provided by 5 “bone fiducials” affixed to the skull, which entails 9 scalp wounds entailed by 4 Leksell pins plus the 5 fiducials. We reasoned that employing the 4 pins securing the Leksell frame to the skull as fiducial points would obviate 4 of the bone fiducials without compromising accuracy..

    Methods: We quantified localization error,defined as the euclidian distance between planned entry/target points and actual entry/target points, for each SEEG electrode trajectory associated with either Leksell Pin (LP) or “traditional” bone fiducial (BF) registration in the manner described by Gonzalez-Martinez et al.1 Target-point and entry-point errors of 70 consecutive LP-defined trajectories were compared to those seen for 95 consecutive BF-defined trajectories.

    Results: Point errors were seen in 92 FP trajectories and in 67 LP trajectories. Target-point errors (TPE) for the LP group (median = 1.8mm, range 0 – 5.8) were similar to the BF group (median = 1.6 mm, range 0 – 7.8) with a mean difference of -.178t(163) = -1.541, p=.125, (90% CI, -0.369 to 0.013). Likewise, entry-point errors (EPE) for the LP group (median = 1.2, range 0 – 3.2) were similar to the BF group (median = 0.9mm, range 0 – 4.7) with a mean difference of -0.016 t(163) = -0.078, p=.938 (90% CI, -0.347 to 0.315).. Only one of the 67 LP entry-point errors exceeded 3.0 mm; 2 of the 95 BF entry-point errors exceeded 3.0mm.

    Conclusions: The techniques appear equally accurate, but the LP bone fiducial renders placement of 4 bone fiducials unnecessary, potentially reducing OR time and patient discomfort

    Patient Care: Decrease patient discomfort; shorten operative time

    Learning Objectives: Simplify an established technique for stereotactically placing SEEG leads

    References: Gonzalez-Martinez J et al. Technique, Results, and Complications Related to Robot-Assisted Stereoelectroencephalography Neurosurgery 78:2;169-180 (2016).

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