Research On The Basic Issues In Non-invasive Blood Glucose Measurement Based On Mid-infrared Spectroscopy

Diabetes mellitus, which menaced humankind's health, is a fateful disease.In order to reduce the incidences of diabetes coexisted diseases, blood glucose must be measuredopportunely and frequently. Therefore, there is an important practical significance to measureblood glucose non-invasively and continuously.Mid-infrared (MIR) spectroscopy gives more distinct absorption bands of each moleculeand there is little disturbance between different absorption peaks. The studies on the bloodglucose determination non-invasively using MIR spectra of human skin have undertaken a fewyears, but there is no breakthrough in the results. The main problems of the method are: a)there is insufficient study of certain issues such as interactions between light and tissue, glucosesource and glucose levels in tissue and in blood. Furthermore, the means of improving analysisaccuracy effectively are limited. b) Human skin is a complex, time-varying system, its spectrumis susceptible to some physical or chemical factors, and spectral information will directly affectthe reliability and robustness of the calibration model. c) Glucose absorption signal is very weakand brings great difficulties for extraction effective information.The study of this paper is focused on the basic issues in non-invasive blood glucosemeasurement based on MIR spectroscopy, and main contents are as follow:1) The physical model of blood glucose determination non-invasively using MIR spectra ofhuman skin was derived from analyzing the interactions between MIR and biological tissues, thesources of abosorption information related to blood glucose in the spectra of human skin and therelationship between the glucose comes from interstitial fluid (ISF) and blood glucose,theresults shows that epidermal ISF can be substituted for the blood to determine blood glucoselevel.Compared with the blood, ISF are relatively simple,it's easier to measurement glucose inISF based on MIR spectroscopy.2) Different calibration methods were discussed and a few calibration models were abtainedto determine glucose in ISF. PLSR can get better results.3)The effects of skin pretreatment on spectra of human skin were studied.the results showsthat optical path-length variartion is the main reason for the spectra change and the chancecorrelations between path-lengths and glucose concentrations will lead to PLSR calibrationmodels with relatively poor accuracy and robustness.Multiple Scatter Correction or StandardNormal Variate can be used to correct path-length efficiently.4) A method was introduced to evaluate the interference of stratum corneum (SC), spectra collecting opportunity and contact pressure. in addition to this,there was no correlation betweenATR-FTIR spectra of skin and blood glucose concentrations in OGTT.It is concluded that ISFcannot easily penetrate into SC.5) The systerm of non-invasive blood glucose measurement based on MIR spectroscopywas designed and certain approachs were emphasized to improve S/N of the spectra.