Non-invasive Blood Glucose Measurement Method

The variation of measurement conditions is one of the major interfering factors that affect the accuracy of non-invasive blood glucose sensing in near-infrared(NIR)diffuse reflectance.In NIR,the temperature variation as the main interference affects the diffuse reflectance,thus affecting the accuracy of blood glucose sensing consequently.By analyzing the existing methods to restrain temperature variations,a measurement method based on temperature-insensitive radial distance by NIR diffuse reflectance is proposed,that is,the radial distance,whose diffuse reflectance is insensitive to temperature variations,is chosen to collect spectrum.In this paper,the feasibility and effectiveness of the measurement method are studied by among theoretical deduction,in vitro experiment,and Monte Carlo simulation,synthetically.Firstly,the relationship between variations of diffuse reflectance caused by temperature variations and radial distance is analyzed,and an assumption of the existence of temperature-insensitive radial distances in scattering medium is proposed.Accordingly,the NIR diffuse reflectance measurement method based on temperature-insensitive radial distance and its feasibility is proposed,and the function of the temperature-insensitive radial distance in scattering medium is deduced based on the solution of diffuse equation in infinite medium.Based on the effect of temperature on optical parameters of the 3% Intralipid solution,the temperature insensitive radial distance was calculated approximately.The result shows the existence of temperature-insensitive radial distances in scattering medium and it is wavelength-dependent.Secondly,a multi-radial distance diffuse reflectance detection system of six light sources(1050,1219,1314,1409,1550 and 1600 nm)was built to measure the diffuse reflectance of 3% Intralipid solution at eight radial distances(0.48,0.76,1.04,1.32,1.60,1.88,2.16 and 2.44 mm)from 35 to 40 ?.The result shows that the measurement method based on temperature-insensitive radial distance satisfies its feasible conditions.Further,the effect of the measurement method on eliminating the influence of temperature variation was evaluated by randomly matching the sample temperature.The result shows that the method based on temperature-insensitive radial distance can significantly reduce the influence of temperature change in NIR diffuse reflectance and improve the prediction accuracy of the model.Finally,based on the influence of temperature on the absorption coefficient and reduced scattering coefficient of human tissue,a Monte Carlo simulation of human skin model was performed.The result shows that there is the temperature-insensitive radial distance in human body tissue from 1000 to 1440 nm,the variation information of glucose can be detected at the temperature-insensitive distance,and the influence of glucose concentration variations on the radial distance can be ignored.Further,when tissue temperature changes,the correlation between spectral information at a temperature-insensitive radial distance and glucose concentration is significantly better than other radial distances.At the same time,the multivariate regression model established by the spectrum of temperature-insensitive radial distance is obviously better than other radial distances,which is almost close to the situation of constant temperature.