Noninvasive blood glucose assay using a newly developed near-infrared system

Near-Infrared Spectroscopy—Its Versatility in Analytical Chemistry

“…4·4·1 In vivo non-invasive measurement of blood glucose by near-infrared diffuse-reflectance spectroscopy NIR spectroscopy has been known to have a potential for realizing noninvasive blood glucose monitoring, and NIR noninvasive blood glucose assay has been investigated extensively for many years. [67][68][69][70][71][72][73][74][75][76][77][78] Robinson et al 71 and Muller et al 72 used a shorter wavelength NIR region, i.e. the region between 800 and 1300 nm (or 1350 nm for Muller et al 72 ) for finger DR spectra measurements.…”

“…To overcome the difficulties mentioned above, Maruo et al 76,77 developed a new NIR system that can detect very weak glucose signals in human tissue, and realize a noninvasive blood glucose measurement. The region of 1300 to 1900 nm was chosen for the NIR measurements.…”

“…Figure 17 illustrates the developed NIR system for non-invasive blood glucose measurements. 76 The system consists of a tungsten halogen lamp (150 W), an optical fiber bundle, switching device for selecting a light path, a flat field-type grating, a 256 In GaAs photodiode array sensor extended to a cut-off 2100 nm, a 16-bit A/D converter and a signal processor. For more details about the developed system, Fig.…”

“…18 shows the concept of a blood glucose measurement and a schematic diagram of the cross-section of human skin tissue. 76 It consists of three layers, i.e. the epidermis, dermis and subcutaneous tissue.…”

“…The developed system has two optical fibers to obtain the dermis spectra selectively. 76 One set of optical fibers is attached to the skin surface vertically; the skin surface is illuminated by the measuring light through the inlet optical fiber, and the scattering light is collected by the detecting fiber. When one chooses an adequate fiber distance, it becomes possible to control the penetration depth of the measuring light.…”