Noninvasive glucose determination by oscillating thermal gradient spectrometry

Several noninvasive measurement approaches for the determination of blood glucose levels have been pursued over the past two decades. There is worldwide recognition that an unobtrusive and noninvasive measurement technique will better enable the patient with diabetes to obtain information for appropriate disease management. Many challenges have so far prevented any noninvasive technology from meeting the requirements. In this article, we describe a novel optical technology that when applied to the human body, provides both the sensitivity and the specificity required for acceptance. For human tissue, specific wavelength bands in the mid- infrared (IR) region offer predominantly single component absorbances and thus, provide the basis for the required specificity of an in vivo determination of glucose. It is highly desirable to utilize these bands for the development of a practical spectroscopic technique. The use of mid-IR absorbance bands requires a methodology that accommodates relatively short optical transmission pathlengths. Thermal gradient spectroscopy is one suitable methodology. We describe the utilization of optical phenomena, which arise during a thermal gradient, in the development of a practical instrument. The prototype apparatus is described and results obtained from aqueous samples and tissue phantom studies are presented. Furthermore, a mathematical derivation is presented in the Appendix, that defines the relationship between the optical signals produced and the properties of the tissue under analysis.