title: Development of an implantable flexible probe for simultaneous near-infrared spectroscopy and electrocorticography.
abstract: A combination of near-infrared spectroscopy (NIRS) and electrocorticography (ECoG) provides beneficial information on cortical activity from different aspects. Integration of such multimodal measurement capability into a single apparatus and the direct measurement of cortical activity during chronic subdural implantation may be a powerful means for clinical diagnosis and neuroscience. However, an optical fiber-based NIRS probe cannot be miniaturized for implantation into the brain, and the light-scattering effect of ECoG electrodes in NIRS measurements is unknown. We describe here the development of a flexible probe, small enough for chronic subdural implantation, for simultaneous NIRS and ECoG. Two light-emitting diodes of different wavelengths and two photodiodes were mounted on a polyimide-based flexible substrate, and ECoG electrodes were formed with a design minimizing artifacts in NIRS recording. The fabricated probe measured ECoGs at sufficient spatial resolution and submicromolar changes in hemoglobin concentrations in in vivo experiments with acute implantation into a rat. Comparison of measured changes in hemoglobin concentrations for different source-detector distances reveals the reliability of the measured values and the practicality of the simulation model. The proposed intracranial multimodality probe may provide beneficial evidence for pre- and intrasurgical assessment of neurosurgery and reveal the interaction of electrophysiology and hemodynamics at high spatial resolution without artifacts due to scalp blood flow.
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Yamakawa
authors.forename: Takano
authors.initials: T
authors.lastname: Inoue
authors.forename: Yeting
authors.initials: Y
authors.lastname: He
authors.forename: Masami
authors.initials: M
authors.lastname: Fujii
authors.forename: Michiyasu
authors.initials: M
authors.lastname: Suzuki
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Niwayama
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply / Q000502:physiology; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D018496:Hyperoxia; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D059629:Signal-To-Noise Ratio; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation* / Q000379:methods