Suppression of superficial hemodynamic changes using a depth-selective filter in near-infrared spectroscopy measurements

Herein, we introduce a depth-selective filter to our recently developed equilateral-triangle probe arrangement to suppress the influence of skin-blood-flow changes on cerebral-blood flow in near-infrared spectroscopy (NIRS) brain-function measurements. The effect of the filter was evaluated by both simulations and experiments. According to the simulations, the influence of the absorption-coefficient perturbations in the superficial layer below the triangle's vertex can be successfully reduced using the filter. We found that applying the new filter process to experiments performed using a system containing an equilateral-triangle sensor arrangement can help in successfully reducing the influence of blood-flow variations accompanying postural changes. Thus, it is valuable to obtain topographic images using this depth-selective filter, and the equilateral-triangle sensor arrangement is suitable for enhancing the filter effect.