Specular reflection vs. backscattering for transdermal OCT-based glucose monitoring with an implantable sensor system

Alexander I. Kholodnykh, Ralph Ballerstadt, Adam Boretsky, Colton Evans, Ashok Gowda, Roger McNichols, Massoud Motamedi

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The reliability of optical techniques for non-invasive monitoring of glucose can be significantly improved by the deployment of a subcutaneous implantable sensor that can closely track the changes in the local concentration of glucose in skin. We have developed a novel implantable sensor that can track glucose-induced changes in the optical turbidity of the implant. In this sensor, optical turbidity decreases significantly with increased glucose concentrations. We performed comparative measurements by optical coherence tomography (OCT) used to monitor backscattering or specular reflection originated from specific structures within the sensor and by collimated light transmission measurement technique to measure the changes in light attenuation as function of glucose concentration within the sensor as well as when the sensor was implanted in phantom media or in tissue samples. These measurements showed that glucose-induced changes in the transmission values derived from OCT monitoring of the sensor turbidity differed up two times from those obtained by collimated transparency measurement (CTM) technique. These results were used to determine the values for scattering coefficients of tissue and the sensor and to estimate the relative loss in sensor sensitivity as a function of implantation depth in tissue. The results suggest that the implantable sensor can be placed in turbid medium such as skin up to an optical depth of 12 mean free paths (mfp), one could expect. For a turbid medium such as skin with a scattering coefficient (μs) of 10mm-1, this would result in geometrical depth of implantation at 1.2 mm beneath the tissue where sensor sensitivity of 50% or higher is expected. The study demonstrates that it could be feasible to engineer a novel optical sensor for glucose monitoring that can be implanted under the skin while providing a high degree of sensitivity and specificity for noninvasive glucose monitoring.

Original languageEnglish (US)
Title of host publicationOptical Diagnostics and Sensing VIII
StatePublished - 2008
EventOptical Diagnostics and Sensing VIII - San Jose, CA, United States
Duration: Jan 21 2008Jan 23 2008

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


OtherOptical Diagnostics and Sensing VIII
Country/TerritoryUnited States
CitySan Jose, CA


  • Biosensors
  • Glucose sensing
  • Optical tomography
  • Scattering

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging


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