Multichannel Signal Processing Method for Disturbance Cancelation in Brain Function Measurements Using Near-Infrared Spectroscopy

Cancellation of Superficial Blood Flow in Brain Function Measurements Using Near-Infrared Spectroscopy

In brain function measurement by near-infrared spectroscopy, reduction of signal fluctuation caused by the superficial blood flow is necessary. We proposed an equilateral-triangle-type sensor arrangement for cancelling superficial blood flow using short-distance detectors placed at the center of the triangle. We applied the independent components analysis (ICA) for this equilateral triangle configuration to improve the correction effect. We measured the change in blood volume caused by the motion artifacts according to the posture change and analyzed the correction effect of the ICA. It is shown that the ICA is more effective than simple subtraction and has small dependence on the measurement conditions and is applicable to this equilateral triangle configuration.

Cancellation Method of Signal Fluctuations in Brain Function Measurements Using Near-Infrared Spectroscopy

To estimate brain activity, it is important to improve the accuracy of brain function measurements by using near-infrared spectroscopy. The detection of signals is vital for correcting any disturbances or changes in the skin blood volume. We developed a cancellation method for brain probes placed on the scalp in the configuration of an equilateral triangle. In this configuration, 12 types of target signals were detected between the vertices, and 6 types of correction signals were detected between the vertices and the center of the triangle. We measured the changes in the blood volume resulting from the specific postural changes of the subject and applied the correction method using three calculation methods. The measured results showed that the correction signals were effective in reducing the disturbances. The correction was based on the cross-correlation coefficient and the amplitude ratio of signals.