Towards Accurate Dielectric Property Retrieval of Biological Tissues for Blood Glucose Monitoring

Tuba Yilmaz, Robert Foster, Yang Hao
  • IEEE Transactions on Microwave Theory and Techniques, December 2014, Institute of Electrical & Electronics Engineers (IEEE)
  • DOI: 10.1109/tmtt.2014.2365019

Dielectric spectroscopy with a spiral resonator

What is it about?

Tracking changes in blood glucose levels is important for diabetics, as well as for healthy subjects (e.g., first responders, astronauts, military personnel). One method involves looking for changes in the dielectric properties (permittivity) of body tissue, and mapping those changes to changes in blood glucose levels. Microwave resonators can be used for this purpose, but determining the permittivity can be challenging, particularly with complex resonator geometries required to make compact devices. Our paper shows how numerical techniques can be applied to accurately determine the permittivity when no closed-form (analytic) equation exists (as with complex geometries). A spiral resonator is used as an example.

Why is it important?

As well as demonstrating, for the first time, the use of numerical techniques to establish a relationship between measurable resonator parameters (e.g., shift in resonant frequency) and the permittivity of the sample above the resonator, this paper investigates a number of error sources that degrade accuracy in dielectric spectroscopy measurements. The technique is general and not limited to body tissue measurements, but the application to blood glucose monitoring could assist researchers around the world in making wearable, non-invasive, continuous blood glucose monitoring a reality,.


Dr Robert N Foster
University of Birmingham

Tracking changes in blood glucose levels without the use of needles (i.e., a non-invasive solution) is something of a "holy grail" for researchers around the world. There are a number of non-invasive methods that have been tried, with little or no commercial success as yet. One promising method is dielectric spectroscopy, which measures changes in the permittivity of body tissues; however, simple relationships between sample (body) permittivity and resonator properties are only available for the simplest of resonator geometries. Inspired by this need, we looked at whether the use of numerical methods could bridge the gap, as well as the sources of error within the method to determine accuracy issues. The technique could be used for any application of dielectric spectroscopy in principle, but the possibilities for blood glucose tracking are particularly exciting.

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The following have contributed to this page: Dr Robert N Foster