Multi-channel Near-Infrared Spectroscopy (NIRS) system for noninvasive monitoring of brain activity

Near Infrared Spectroscopy is a noninvasive optical method to monitor hemodynamic activity in tissue using light in the range of 600 to 900nm. Various techniques and devices have been developed to utilize this method in a variety of medical fields such as, neuroscience, monitoring of newborn brain, muscle physiology and brain computer interface (BCI). In this paper we present design and implementation of a dual wavelength, multi-channel, continuous wave near infrared brain imager. The aim of this design is to produce a miniaturized, affordable, negligibly intrusive system that can monitor hemodynamic response of prefrontal cortex activity. The system consists of a sensor pad, a control board, a battery, and a data acquisition (DAQ) card. DAQ card acquires and digitize data and sends it to a computer for displaying the temporal and spatial information in real time as concentration changes in oxy-hemoglobin (HbO₂) and deoxy-hemoglobin (Hb). In addition the DAQ provides control signals to the control board. To test the system performance, experiments have been conducted with a static phantom that simulates optical properties of human brain tissue and changes in Hb and HbO₂ concentrations.