Near-infrared spectroscopy system for quantitative characterization of four biomarkers in biotissue oxygenation

Abstract

Near infrared spectroscopy (NIRS) is a valuable tool for noninvasive and quantitative analysis of biotissue, particularly within the spectral range of 670 to 1000 nm due to the inherent transparency. This technique facilitates the assessment of crucial chromophores including deoxyhemoglobin (Hb), oxyhemoglobin (HbO2) and the oxidized state of cytochrome c oxidase (CCO), enabling real-time evaluation of oxygenation and metabolism in human brain and other tissues in vivo. However, the influence of light scattering within tissues and its consequential impact on the accurate quantification of Hb, HbO2, and CCO concentrations were neglected in NIRS measurements. We have developed a portable real-time 4-wavelenght NIRS system to measure the variations in Hb, HbO2, and CCO concentrations, along with concurrent tracking of alterations in biotissue light-scattering characteristics. These measurements were conducted across various modes of respiration and blood circulation in vivo. It is shown that a more precise assessment of the contribution attributable to scattered light does play a significant role in the light absorption of Hb, HbO2 and CCO. Consequently, the precision of quantifying vital biomarker concentration shifts through NIRS technology is markedly enhanced. The assimilation of scattered light data enriches the understanding of oxygenation processes within tissue, thus augmenting the depth and breadth of insights attainable through NIRS studies conducted in vivo. By bridging the gap between light scattering and chromophore absorption, the realm of heightened accuracy and comprehensive physiological interpretation can be achieved.