Development of an implantable flexible probe for simultaneous near-infrared spectroscopy and electrocorticography

IEEE Trans Biomed Eng. 2014 Feb;61(2):388-95. doi: 10.1109/TBME.2013.2279888.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / blood supply
  • Brain / physiology
  • Electrodes, Implanted
  • Electroencephalography / instrumentation*
  • Electroencephalography / methods
  • Equipment Design
  • Hyperoxia
  • Male
  • Rats
  • Rats, Sprague-Dawley
  • Signal-To-Noise Ratio
  • Spectroscopy, Near-Infrared / instrumentation*
  • Spectroscopy, Near-Infrared / methods