Tissue Optics Basis And Application In Non-Invasive Sensing Of Blood Glucose Concentration With Near-Infrared Spectroscopy

Noninvasive sensing of blood glucose concentration with near-infrared spectroscopy has attracted world wide interest and is of great practical importance. However, a valid noninvasive method for glucose sensing doesn't come into clinical realization yet. The reasons lie in the facts of complexity in human tissue, week glucose specific signal compared with strong background noise, the variance between individuals, and the dependence on time, etc. This thesis aims at setting up light migrating models in skin, analyzing the influence of difference between individuals on selecting the proper source-detector separation, through investigating tissue optics problems relating to glucose sensing. As the final goal of this thesis, floating-reference method, which is expected to realize maximal sensitivity of glucose and depress the negative effect of internal noise, was derived and verified.Principle of glucose sensing and its relating analyzing procedure were firstly discussed, and the necessity and importance for studying light propagation in complex medium were emphasized. Systemic analysis was further carried out to uncover the internal relation among changes in glucose concentration, optical properties of skin, and diffuse reflectance. Both light scattering model for single micro particle and light transportation model in three-layered skin were constructed. The probability function was proposed, which integrated analytical characteristic of transportation equation and statistics of random walk method. Optical properties of skin tissue from 1100nm to 1700nm were determined through a comparison investigation.The statistical properties of diffused light and selection of source-detector separation for optical probe used in glucose sensing were synthetically analyzed. According to the actual necessity for blood glucose sensing, path length and penetration depth of diffuse light were studied respectively. Based on this, measurement sensitivity and ratio of effective photon, which have close relation with glucose sensing, were subsequently studied. Limit resolution concentration for glucose measurement was derived under the full consideration of measurement sensitivity, effective signal-to-noise ratio and measurement limiting condition. The influence of difference in optical properties and skin thickness on limit resolution concentration was discussed in detail, which made a solid foundation for designing...