Abstract: A method for classifying live subjects according to optical thickness of the skin is based on noninvasive, near-infrared reflectance measurements on skin tissue. An indicator of skin optical thickness is derived through analysis of the water, fat, and protein marker bands in the near infrared spectrum. The skin thickness indicator may then be used to evaluate the suitability of the subject for calibration on a standardized set of optical probes. The optical probes in the standardized set are designed to cover a range of penetration depths by varying the distance distribution between illuminator and detector fibers on each probe tip.

Abstract: A method for classifying live subjects according to optical thickness of the skin is based on noninvasive, near-infrared reflectance measurements on skin tissue. An indicator of skin optical thickness is derived through analysis of the water, fat, and protein marker bands in the near infrared spectrum. The skin thickness indicator may then be used to evaluate the suitability of the subject for calibration on a standardized set of optical probes. The optical probes in the standardized set are designed to cover a range of penetration depths by varying the distance distribution between illuminator and detector fibers on each probe tip.

Abstract: A method and apparatus for minimizing confounding effects in a noninvasive in-vivo spectral measurement caused by fluctuations in tissue state monitors a selected tissue state parameter spectroscopically and maintains the selected parameter within a target range, at which spectral effects attributable to the changes in the selected parameter are minimized. The invention includes both active and passive control. A preferred embodiment of the invention provides a method and apparatus for minimizing the confounding effects in near IR spectral measurements attributable to shifts in skin temperature at a tissue measurement site. Spectroscopic monitoring of skin temperature at the measurement site provides near-instantaneous temperature readings by eliminating thermal time constants. A thermistor positioned at the measurement site provides active control. The spectrometer and the temperature control device are incorporated into a single instrument for noninvasive measurement of blood glucose concentration.

Abstract: A non-invasive system for characterizing and classifying the state and structure of a tissue sample operates on a near infrared absorbance spectrum of in vivo tissue. A method that uses near-infrared spectral measurements to characterize and classify the state and structure of tissue sampled based on absorbance features related to fat in adipose tissue is provided. Also provided is a method of estimating skin fold thickness. The approach provides information about sources of tissue variability and is therefore useful for establishing the general category of the tissue structure. Categorization of subjects on the basis of the determination is suitable for further spectral analysis and the measurement of biological and chemical compounds, such as blood analytes. The invention further provides a method of estimating percent body fat based on a skin fold thickness estimate.

Abstract: A method and apparatus for minimizing confounding effects in a noninvasive in-vivo spectral measurement caused by fluctuations in tissue state monitors a selected tissue state parameter spectroscopically and maintains the selected parameter within a target range, at which spectral effects attributable to the changes in the selected parameter are minimized. The invention includes means for both active and passive control.