Existence And Application Of Glucose Iso-diffuse-reflectance Wavelength In The Scattering Medium

Non-invasive blood glucose detection, with its advantages of painlessness andconvenience, makes it possible for the real-time monitoring of blood glucose, whichplays a significant role in reducing complications and improving life quality of thediabetes patients. Reference wavelength method has been put forward by our groupfor the correction of large background shift in the NIR non-invasive glucosemeasurement, and iso-absorptive wavelength has been proved exist in the pureabsorbing medium. This study, based on the previous results, focuses on the existence,influence factors and application of glucose iso-diffuse-reflectance wavelengths(reference wavelength) in different scattering medium at different source-distanceseparations, which provides evidence for the further application of floating referencemethod at multiple wavelengths and source-detector separations.In this paper, the iso-diffuse-reflectance wavelengths of glucose in differentscattering medium, at different source-detector separations are derived by the diffuseequation, verified by the Monte Carlo simulation and phantom experiments and theirproperties also explored. Conclusions can be made that the iso-diffuse-reflectancewavelengths exist within certain range of source-detector separations, and changewith the absorption and scattering coefficients. Some wavelengths, like1135nm,1185nm,1300nm and1370nm are proved less sensitive to the absorption coefficientvariation by Monte Carlo simulation, while the existence properties parallel along thesource-detector separation when the scattering coefficient changes. Also, wavelengths,at about1140nm-1150nm,1190nm-1200nm, and1300nm-1310nm are proved lesssensitive to different levels of SNR by both Monte Carlo simulation and phantomexperiments.Furthermore, correction method based on the iso-diffuse-reflectance wavelengthmethod is put forward and applied before the PLS modeling. According to the results,the glucose iso-diffuse-reflectance wavelength in the5%intralipid existing at about1300nm provides the most effective correction. The PLS modeling of experimentaltests by the iso-diffuse-reflectance wavelength correction method, compared withsimply background subtraction method, indicates that the background shift can begreatly reduced. The RMSEC and RMSEP of PLS models by iso-diffuse-reflectancewavelength correction method decline respectively by52.3%and54.0%in asingle-day experiment. Also, the RMSEC and RMSEP by iso-diffuse-reflectance wavelength correction method reduce respectively by26.1%and31.4%in a multi-dayexperiment. Both prediction models indicate high linear correlation between thecorrected spectra and glucose concentrations with R-squares of0.99.This study improves the prediction accuracy of glucose concentration in thescattering medium, which may contribute to the further application of floatingreference method at multiple wavelengths and source-detector separations.