title: In vivo monitoring of glial scar proliferation on chronically implanted neural electrodes by fiber optical coherence tomography.
abstract: In neural prosthetics and stereotactic neurosurgery, intracortical electrodes are often utilized for delivering therapeutic electrical pulses, and recording neural electrophysiological signals. Unfortunately, neuroinflammation impairs the neuron-electrode-interface by developing a compact glial encapsulation around the implants in long term. At present, analyzing this immune reaction is only feasible with post-mortem histology; currently no means for specific in vivo monitoring exist and most applicable imaging modalities can not provide information in deep brain regions. Optical coherence tomography (OCT) is a well established imaging modality for in vivo studies, providing cellular resolution and up to 1.2 mm imaging depth in brain tissue. A fiber based spectral domain OCT was shown to be capable of minimally invasive brain imaging. In the present study, we propose to use a fiber based spectral domain OCT to monitor the progression of the tissue's immune response through scar encapsulation progress in a rat animal model. A fine fiber catheter was implanted in rat brain together with a flexible polyimide microelectrode in sight both of which acts as a foreign body and induces the brain tissue immune reaction. OCT signals were collected from animals up to 12 weeks after implantation and thus gliotic scarring in vivo monitored for that time. Preliminary data showed a significant enhancement of the OCT backscattering signal during the first 3 weeks after implantation, and increased attenuation factor of the sampled tissue due to the glial scar formation.
authors.affiliation: Neuroelectronic Systems, Department of General Neurosurgery, University Medical Center Freiburg Freiburg, Germany.
authors.forename: Yijing
authors.initials: Y
authors.lastname: Xie
authors.affiliation: Neuroelectronic Systems, Department of General Neurosurgery, University Medical Center Freiburg Freiburg, Germany.
authors.forename: Nadja
authors.initials: N
authors.lastname: Martini
authors.affiliation: Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering(IMTEK), University of Freiburg Freiburg, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Hassler
authors.affiliation: Neuroelectronic Systems, Department of General Neurosurgery, University Medical Center Freiburg Freiburg, Germany.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Kirch
authors.affiliation: Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering(IMTEK), University of Freiburg Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Stieglitz
authors.affiliation: Gisela and Erwin Sick Chair of Micro-optics, Department of Microsystems Engineering(IMTEK), University of Freiburg Freiburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Seifert
authors.affiliation: Neuroelectronic Systems, Department of General Neurosurgery, University Medical Center Freiburg Freiburg, Germany.
authors.forename: Ulrich G
authors.initials: UG
authors.lastname: Hofmann
keywords: chronic implants; fiber catheter; flexible microelectrodes; foreign body reaction; optical coherence tomography