Fundamental Study On The Feasibility Of Earlobe Site For Non-invasive Blood Glucose Sensing With Near-infrared Spectroscopy

The application of near infrared spectroscopy analysis in human blood glucosesensing is of great measurement potential and practical significance. For human body,choosing an appropriate measurement site can enhance the accuracy on near-infraredsensing. The earlobe has many advantages for its affluent blood flow, and itsconvenience for the attachment of the optical sensing probe. So the earlobe site isconvenient to use. In this dissertation, the feasibility of the earlobe as themeasurement site on near-infrared blood glucose sensing is studied.Based on the physiological structures of the intended studying site earlobe andother common measurement sites such as the fingertip, palm and the forearm, analysisis done from the skin layer thickness aspect and the correlation of the blood glucoseconcentration of each site. Then OGTT experiments are conducted. The results showthat the change of the blood glucose level in earlobe capillary is in general the same asthe changing trend of it in the forearm venous whole blood and the fingertip capillarywhole blood. The correlation coefficients are both above0.8. It is indicated that fromthe physiological perspective the earlobe is feasible to be a measurement site in bloodglucose sensing.Using the Monte-Carlo simulation method, the simulations based on the earlobefive-layered skin model in both high glucose concentration level and in human bodyglucose level are done. The results show that the positional floating reference pointexistsin this model, and it is affected by individual variances more significantly underthe high glucose concentration level than in human body glucose level.The resultscould guide the specification of the range of the light source fiber and the detectorfiber. The distribution of the earlobe transmission light and the influence of theindividual variance on earlobe transmission light are analyzed based on the simulationresults according to the earlobe structural features. And the intensity of transmissionlight and the diffuse reflected light is compared in radial direction. It is demonstratedthat the earlobe transmission light has a great application potential.Finally, based on the Monte-Carlo simulation data of the earlobe five-layeredskin model and the phantom experiments’ data on a two-fiber spatial resolutiondiffuse reflected light detection system, a series of PLS modeling are conducted. Theresults show that using the earlobe transmission light at radial position1.9mm canachieve the same modeling results using the spectrum correction method. Thuspreliminarily verify the feasibility of choosing earlobe as the measurement site fornon-invasive blood glucose sensing and its bright application prospect.