Development of a High Density Neuroimaging System Using Functional Near-Infrared Spectroscopy

The progress in the field of neuroscience is critical in our rapidly aging society as the fatality rate due to brain degenerative diseases is rising. Recently, functional near-infrared spectroscopy (fNIRS) has established its application in measuring the blood chromophores' concentration changes during an activity. In this developmental study, we have introduced our lab-developed fNIRS system that is able to compute the concentration changes in oxy-hemoglobin and deoxy-hemoglobin from the optical NIR light signals. We have employed 128 dual wavelength light emitting diodes (LEDs) of 735 nm and 850 nm in the designed system. LED driving circuit was designed by using serial peripheral interface based output expansion chips. A single photodiode (PD) was used for measuring the NIR light intensity received after passing through the brain tissue and getting absorbed and scattered in the process. Our system uses a battery for supplying power to the system. A wireless communication module was interfaced with the system for transferring the fNIRS data to our developed software running on a host computer. The software is capable of displaying the real-time data and record it for future processing. To test the functionality of the system, a phantom brain model was used. The LED and PD were attached to the phantom and multiple combinations of LEDs were tested to provide robust data. Our lab-developed fNIRS system showed the acquired intensity values for both wavelengths which corresponds to hemoglobin changes in 128 channels.