Noninvasive in vivo glucose sensing on human subjects using mid-infrared light.

Mid-infrared quantum cascade laser spectroscopy is used to noninvasively predict blood glucose concentrations of three healthy human subjects in vivo. We utilize a hollow-core fiber based optical setup for light delivery and collection along with a broadly tunable quantum cascade laser to obtain spectra from human subjects and use standard chemo-metric techniques (namely partial least squares regression) for prediction analysis. Throughout a glucose concentration range of 80-160 mg/dL, we achieve clinically accurate predictions 84% of the time, on average.

In vitro measurements of physiological glucose concentrations in biological fluids using mid-infrared light.

Mid-infrared transmission spectroscopy using broadband mid-infrared or Quantum Cascade laser sources is used to predict glucose concentrations of aqueous and serum solutions containing physiologically relevant amounts of glucose (50-400 mg/dL). We employ partial least squares regression to generate a calibration model using a subset of the spectra taken and to predict concentrations from new spectra. Clinically accurate measurements with respect to a Clarke error grid were made for concentrations as low as 30 mg/dL, regardless of background solvent.

In vivo measurement of mid-infrared light scattering from human skin.

Two mid-infrared light sources, a broadband source from a Fourier Transform Infrared Spectrometer (FTIR) and a pulsed Quantum Cascade (QC) Laser, are used to measure angle-resolved backscattering in vivo from human skin across a broad spectral range. Scattering profiles measured using the FTIR suggest limited penetration of the light into the skin, with most of the light interacting with the stratum corneum layer of the epidermis. Scattering profiles from the QC laser show modulation patterns with angle suggesting interaction with scattering centers in the skin.