Abstracts

Rationale: Stereoelectrooencephalography (SEEG) is a neurosurgical procedure in which multiple electrodes (typically 8-14) are placed in the brain to identify the epileptogenic zone. Electrode trajectories are pre-planned to measure electrophysiological activity from key anatomical targets and to avoid blood vessels to prevent haemorrhage. The surgical implantation should conform to the pre-planned trajectories to ensure patient safety and recording from desired targets. The current standard of care for electrode implantation is either a stereotactic frame-based or frameless approach. Robotic systems (Neuromate, ROSA) have been shown to increase the speed and accuracy of SEEG implantation. However, there have been no prospective comparisons of different implantation techniques. In this work we use a skull phantom to compare a novel robotic system (iSYS1) to frameless implantation. Methods: Three patients who had previously undergone electrode implantation (21 electrodes) were selected to represent a range of targets and drilling angles. Skull models for each patient were constructed by intensity thresholding of a CT scan. The models were 3D printed (3D Systems Inc., High Wycombe, UK) with bone fiducials in-situ using a commercially available realistic bone-like substitute (Duraform PA) and covered with a synthetic skin substitute.Two neurosurgeons performed electrode implantation on patients using a frameless technique and corresponding phantoms using a robotic technique. For frameless implantation the patient is registered to the StealthStation® S7® system (Medtronic Inc.) using bone fiducials.  Using the Vertek probe the mechanical arm and precision aiming device are aligned to the pre-planned trajectories.A reducing tube guides the drilling of the trajectory through the skull and the placement of the electrode bolt. The robotic implantation is similarly performed, however, the mechanical arm is replaced by the iSYS1 robotic trajectory guidance system (Medizintechnik Gmbh) that automatically aligns the pre-planned trajectories with a series of iterative steps. The iSYS1 has a working channel through which reducing tubes are placed to allow drilling and insertion of the electrode bolt.Following implantation the skulls underwent a CT scan and the planned and actual (implanted) bolt trajectories were compared for entry point, entry angle, and projected target point as shown in Figure 1. Measures were compared using a student’s paired t-test (2-tailed) in SPSS 24. Results: As shown in Table 1 we found that using the iSYS1 trajectory guidance system implantation entry point accuracies were significantly improved (p Conclusions: We used anatomically accurate patient specific skull phantoms to recreate SEEG electrode implantations to perform preclinical testing for a novel micro-guided robotic system (iSYS1). Entry point accuracy was statistically improved (p Funding: This publication represents in part independent research commissioned by the Health Innovation Challenge Fund (WT106882), a parallel funding partnership between the Wellcome Trust and the Department of Health, and the National Institute for Health Research University College London Hospitals Biomedical Research Centre (NIHR BRC UCLH/UCL High Impact Initiative). We are grateful to the Wolfson Foundation and the Epilepsy Society for supporting the Epilepsy Society MRI scanner. This work was undertaken at University College London Hospitals, which received a proportion of funding from the Department of Health's NIHR BRC funding scheme.