Inside view

17 July 2012

Non-invasive testing

At the University of Greenwich we have been working on several projects in the field of wireless medical instrumentation, such as wireless pulse monitors, wireless oxygen saturation monitors and applications of Bio-RFID in remote healthcare and disaster search and rescue operations. We hope that the work presented in this issue of Electronics Letters can help diabetes sufferers by removing the need for invasive blood sugar level testing.

Blood patterns

To determine the change in blood glucose concentration within the body, the user would take the calibrated device and insert their finger into the test chamber. Inside the chamber an electric field is established with a frequency of approximately 2 GHz, which will bounce around inside the chamber and create a specific pattern of reflections within the chamber that can be measured externally. When the user places their finger inside this field, the pattern of reflections changes owing to the physical properties of their finger, and our device measures those changes, looking specifically at a frequency found to be influenced primarily by blood sugar concentration. Through calibration, the change in the reflections at this specific frequency can be converted into a reading for changes in blood sugar concentration.

Limiting to improve

The inspiration for the current research was actually based on the need for more limitation in current thinking. Most medical research companies have been spending time trying to develop a ‘one size fits all’ device that anyone could use at any time to measure blood sugar. The concept in our research was to take a more simple approach, a smaller step forward but one that would still radically improve the lives of diabetes sufferers and be achievable in a much shorter time scale. The problem of everyone’s bodies being slightly different were sidestepped by allowing a certain amount of calibration using traditional methods, even if this in the early stages was done once a day it would still reduce the need for painful invasive techniques by up to 75%.

Constant vigilance

The current methods of blood glucose testing use a drop of blood placed on a consumable test strip.  The test strip, in conjunction with a small handheld electronic device, calculates the blood sugar level in that drop of blood. The problem with this is that once removed from the body the concentration of glucose in the blood drop will no longer change over time, the blood within the body will change, and at times rapidly. By measuring the blood whilst still inside the body the blood remains part of the system, therefore changes can be continuously tracked (in real time if wearing the device as a monitor), allowing the user much more information and for those struggling with controlling their diabetes potentially lifesaving information.

Furthermore, the concentration of glucose in the blood varies throughout the body, but the information of most importance is that of arterial blood glucose level, and this will not be the same as the test site. However, there will be a direct correlation between glucose levels at the test site and of the arterial levels, which is known as compartmentalisation, and using the finger as a test site reduces the need for compartmentalisation.

The future

The experiment we have conducted proves the principle that changes in glucose concentration will provide a measureable change in the electric field of a microwave cavity – this is a significant first step but more research is required to create a working prototype.  If the technology was refined and expanded and used in conjunction with a small MRI device to measure the volume of the blood being analysed (automatic calibration), there is potential for a full blood test to be carried out non-invasively and in real time in the next 50 years.

The Letter presenting the results on which this article is based can be found on the IET Digital Library.

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Cover of Electronics Letters, volume 50, issue 21

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