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Examination and Analysis of the Influence of Near-Infrared Light Absorption by Hair Melanin on fNIRS Signal

Authors :

Elmira Baghaeifar¹ Sina Shamekhi²

1- دانشگاه صنعتی تبریز 2- دانشگاه صنعتی تبریز

Keywords :

Functional near-infrared spectroscopy،Melanin،Impact of skin and hair characteristics،Signal processing.

Abstract :

In recent years, the use of functional near-infrared spectroscopy (fNIRS) technology has increased despite its limitations and weaknesses. However, further studies are still needed to assess the quality of the signals it produces. fNIRS utilizes near-infrared (NIR) wavelengths, which are known to be absorbed significantly by melanin, oxygenated hemoglobin (HbO), and deoxygenated hemoglobin (HbR). This presents a challenge for researchers employing fNIRS technology. In this study, we examined the average signal power feature, which changes in proportion to the absorption profile of various chromophores, to analyze how factors such as hair color, length, and density affect fNIRS signals. Due to abnormal data distributions within each group, confirmed by the Anderson-Darling test, we employed the Wilcoxon statistical test to compare group similarities. The p-values obtained from the Wilcoxon test revealed significant differences between the groups: those with dark versus light hair, varying hair densities, and different hair lengths. Our results indicated a decrease in the mean power of HbO, HbR, and optical density (OD) signals in individuals with dark hair, high hair density, and long hair length. Furthermore, we found that hair length and density had a more pronounced effect on the average signal power.