The Basic Experimental Study On Floating-reference Method In Non-Invasive Sensing Of Blood Glucose Concentration With Near-Infrared Spectroscopy

Diabetes and its complications are major threats to human beings. Since the noninvasive blood glucose detecting technique has many advantages such as free from pain and no risk of infection, it brings great improvements in pain relief and thus glucose-concentration monitoring in real time.Near infrared spectroscopy is one of the most promising methods for the application of noninvasive sensing of blood glucose concentration and also it has attracted world wide interest and is of great practical importance. However, a valid noninvasive method for glucose sensing does not come into clinical application. The main reasons lie in the facts of complexity in human tissue, the weakness of the glucose signal compared with strong background noise, the variance between individuals, and the dependence on time, etc. In this thesis, based on the analysis of the propagation of the light in the tissue, a novel method, floating reference method, is proposed. This method use reference point and measuring point to realize the maximal sensitivity and can eliminate the background variation of human body.Based on the measurement principle of the noninvasive blood glucose concentration with NIR spectroscopy, this thesis analyzes the noise factors that affect the precision and realization of it. Basing on the previous work of our team, a part of the noise could be eliminated, while the most important part of the noise, the complex background variation of human body, could not be eliminated until now. In order to eliminate the complex background variation of human body, we analyzed the light energy sensitivity to variation of the glucose concentration along different source-detectors separation, and proposed floating reference method. This method used two special points, reference point where the sensitivity to the glucose concentration is zero and measurement point where the sensitivity to the glucose concentration is maximal. Using the diffusion theory under infinit condition, we educed the existing condition of the reference point and the measurement point. Basing on the educed equation, we established the double-fibers experimental system and validated the existence of the reference point in Intralipid-10%. Aiming at validating the feasibility of floating reference method in human body, we performed Monte Carlo simulation on three-layer model of human skin. The result of the simulation present that two prerequisites of the floating reference method applied to human body were obtained. The first one was that the floating poison was influenced little by the glucose concentration, which could be considered unchangeable. The second one was that the position of the floating point was also influenced little by the variance of the wavelength, which could also be considered unchangeable. Both of the conditions may provide strong guarantee for our next work.The main creative content of the thesis includes: the existing condition of the measurement point and the reference point in the floating reference method under infinite condition, was educed; validation of the floating point existence by establishing the double-fiber moving experimental device and validation of the feasible prerequisite of the floating reference method; simulation of the applying prerequisite of the floating reference point method used in the three-layer skin model. All of the work ensured the favorable development of the future work.