Abstract

This chapter reviews in vivo noninvasive monitoring of blood glucose by near-infrared (NIR) diffuse-reflectance (DR) spectroscopy. The NIR spectra of human forearm were measured in vivo by use of an NIR system equipped with a pair of illuminating and detecting optical fibers newly developed by our group. The optical geometry of the fibers enables the NIR measurements selectively from dermis tissue and reduces the interference noise arising from the stratum corneum. Oral glucose intake experiments were performed with six subjects (including single type I diabetes) whose NIR skin spectra were measured at the forearm. Partial least square regression (PLSR) analysis was carried out for the NIR data and calibration models were built for each subject individually. We also developed new chemometrics algorithms and data pre-treatment methods that are useful for the blood glucose assay. In the former part of this review, first the importance of in vivo noninvasive monitoring of blood glucose by NIR measurement is described, and then the NIR system we developed for the in vivo measurement is outlined. Following these the results of NIR spectral measurements and calibration models for blood glucose assay are explained. In the latter part of this review, new chemometrics algorithms for wavelength and sample selections and those for removing interference components are introduced and their applications to the in vivo NIR spectra of human skin are described.