Non-Invasive, Real Time Monitoring of Event-Related Optical Signal (EROS) and Visual Evoked Potential (VEP) During Visual Stimulation

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Conference Proceeding

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Purpose: To determine the feasibility of an fNIRS and visual evoked potential (VEP) dual modal visual cortex monitoring apparatus for clinical functional studies.

Methods: The apparatus consists of a frequency domain tissue spectrometer, fiber optical components, gold plated cup electrodes and amplifiers, and the head resting/sensor mounting mechanism.Two rubber sensor pads are placed on both sides of in ion for simultaneous monitoring of two hemispheres. Multi–layer analytical model and Monte Carlo simulation are used to optimize the design of the optical sensor head. Sensor positions areadjustable for maximum EROS. A flash light and a quadrant grid CRT are used as visual stimulators. The stimulation frequency is set to be 8Hz for 30 seconds followed by 30 seconds of resting period. Optical and electrical signals during multiple stimulation cycles are recorded by a laptop computer with a data acquisition card and a Labview program.

Results: Sensitivity analysis based on the multi–layer analytical model predicts the optimal source–detector separations where the sensor is the most sensitive to the cortex activity. Preliminary tests on healthy subjects demonstrated the capability to capture the optical signal change introduced by visual stimulation. Further clinical validation is pending on institute review board approval.

Conclusions: The preliminary test has demonstrated the technicalfeasibility. The advantages of this system are high flexibility, portability, low cost and biochemical specificity. Moreover,patients and children who might not stand the confined environment of functional magnetic resonance imaging (fMRI) experiments can be repetitively examined by this system.


Abstract of paper presented at the Association for Research in Vision and Ophthalmology's annual meeting in 2006.