Water correction algorithm to increase the signal strength of oxy and deoxy-hemoglobin in near-infrared spectroscopy signals

In the wake of recent advances in the field of neuroscience, near-infrared spectroscopy (NIRS) has been widely used to measure the concentration changes in the blood chromophores during mental activity. NIRS system can be constructed low cost, portable and easy to use. Given that approximately 80% of blood chromophores are water, it is particularly important to the effect of water concentration change on measurement data. In the present study, we developed a wireless NIRS system that detects not only the concentration changes of oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) during mental activity but also that of water (H₂O); additionally, it implements a water-correction algorithm that improves the HbO and HbR signal strengths manifest during an arithmetic task. The system comprises a microcontroller, an optical probe, tri-wavelength light emitting diodes (LEDs), photodiodes, a WiFi communication module and a battery. System functionality was tested by means of arterial occlusion and arithmetic-task experiments, performed with healthy male subjects.