Assessing the Long-term Stability of Chronic Wireless Floating Microelectrodes in the Visual Cortex of Human Participants
Katarina Stephan1, John C. Collins3, Astrid Jiang5, Carmen Pons4, Philip R. Troyk2, Vernon Towle6
1Department of Biomedical Engineering, 2Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, 3Department of Radiology, 4Department of Neurosurgery, The University of Chicago, 5Department of Neuroscience, Johns Hopkins University, 6Department of Neurology, University of Chicago
Objective:
To develop and apply a reproducible image-based methodology of the positional stability of the wireless floating microelectrode arrays (WFMAs) of the Intracortical Visual Prosthesis (ICVP) implanted in the visual cortex of two human participants with blindness.
Background:
Quantifying the stability of the implanted electrodes is essential to the long-term viability and safety of the chronically implanted systems. The ICVP uniquely avoids surface and cabled arrays, which are known in the literature to lose positional integrity in the primate brain. Each WFMA contains 16 stimulating electrodes inserted into the parenchyma. Although quantitative evidence of electrode stability in humans is limited, the stability of penetrating WFMAs in canine cortices has demonstrated no histological evidence of migration. Using preoperative MRI and serial, post-operative CT scans, electrode migration can be quantitatively monitored.
Design/Methods:
Two participants with blindness were implanted with WFMAs in the right dorsolateral occipital cortex: Participant 1 (53-year-old male) received 25 implanted WFMAs; Participant 2 (65-year-old male) received 32 implanted WFMAs. Preprocessing and cortical surface reconstruction were performed using FreeSurfer v.8.1.0. Co-registration of the preoperative MRI and serial CT scans (0 days to 3 years for Participant 1; 0 days to 6 months for Participant 2) was performed using MATLAB 2021b and iELVis repository. Electrode localization and displacement were quantified using 3D Slicer v.5.8.1.
Results:
Anatomical preoperative MRI scans and postoperative CT scans were obtained for each participant at defined time intervals. Image preprocessing and co-registration using MATLAB 2021b/iELVis repository was implemented in both participants. Electrode localization and longitudinal analysis is in progress to quantify positional stability.
Conclusions:
This study establishes a reproducible image-based method for evaluating WFMA stability in individuals implanted with the ICVP system. Upon completion of the analysis, this approach will provide quantitative data for the viability and safety of the wireless penetrating arrays for the chronic implantation of the cortical visual prosthesis.
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