In Vivo Validation Of Floating Reference Position And Its Preliminary Application On Non-Invasive Blood Glucose Sensing By Near-Infrared Spectroscopy

One of the main challenges in the noninvasive sensing of blood glucose by nearinfrared(NIR)spectroscopy is the background variations from light source drift,sweating,position,temperature and contacting pressure change at the human-machine interface.Reference measurement based on position is one of the promising methods for clinical application in non-invasive blood glucose measurement by diffused reflectance spectroscopy.The homogenous interference can be eliminated by differential measurement between the spectra collected at the detection position and the reference position locates near the detection position which contains the same background variations.This thesis summarized the progresses about the study of floating reference measurement method by our group and analyzes the main problems and solutions to apply this method during in vivo measurement.The existence and distribution of the floating reference position is verified and the effectiveness of floating reference measurement method based on differential processing for in vivo application is validated.The methods to eliminate the influence of these factors are proposed according to the characteristics of different background interference factors.In this paper,a pressure adaptive auxiliary spectral acquisition and positioning device is designed to reduce the influence of position change and pressure change.The floating reference position may vary with different individuals.Individual difference is simulated by changing the thickness of epidermis and dermis.Monte Carlo(MC)simulation is used to study the variation of floating reference positions of different wavelengths and different people.Then the fiber probe is designed and the SLD-based experiment system is built.After evaluating the accuracy of the system,in vivo OGTT experiments are conducted to validate the existence of floating reference position.For the influence on sensitivity caused by differential calculation,MC and intralipid experiment are conducted to compare the sensitivity between single position sensing and differential calculation of two positions.First of all,the differential sensitivity of any two positions in a three-layer model is studied by MC,the results show that the position with highest sensitivity locates at the floating reference position.Then intralipid solution experiment is conducted to validate the differential sensitivity of any two positions.Result shows that the reference positions with highest differential sensitivity are close to the floating reference positions.At last,clinical experiments validated the effectiveness of the floating reference position based differential measurement method for eliminating the influence of light source drift and sweating.We designed a probe for in vivo experiment depending on the previous study and analyzed the detection precision of the experiment system.The theory of differential measurement was deduced based on a simplified physical model of in vivo measurement.After the validation of this theory through Intralipid experiment,preliminary clinical experiments were conducted and results showed that the accuracy of in vivo measurement can be significantly improved through this method.