Far-Infrared Technique Noninvasively Measures Blood Glucose

A light-based method for measuring blood glucose may give diabetes patients the daily monitoring they need without the pain and infection risk of conventional metering.

Researchers from Tohoku University's Graduate School of Biomedical Engineering, led by professor Yuji Matsuura, have developed a noninvasive method of measuring blood glucose using far-infrared (FIR) light.

Researchers have developed a method of measuring blood glucose using far-infrared light. Courtesy of Yuji Matsuura.
A previously suggested method for glucose measurement using near-infrared (NIR) light works on the premise that such light of specific wavelengths is selectively absorbed by glucose in the blood. However, accurate and stable measurement using this method has proven difficult because the NIR light is not only weakly absorbed by glucose, but also by water, protein and hemoglobin, the researchers said.

In contrast, FIR light with wavelengths of around 10 μm is strongly absorbed by glucose, making it possible, in theory, for patients to get more sensitive and accurate measurements. However, researchers face the problem that FIR light penetrates only a few microns beyond the skin's surface, which makes the detection of blood glucose difficult.

Using a small prism, it is possible to irradiate the oral mucosa of inner lips. Courtesy of Yuji Matsuura.
The Tohoku team’s measurement technique employs a small prism attached to the ends of flexible, hollow optical fibers to radiate FIR light, allowing irradiation of the oral mucosa of inner lips that, unlike skin, have no thick horny layer.

Results from experiments show blood glucose levels sensitively detected and accurately measured with a less than 20 percent margin of error, which Matsuura said is good enough for clinical use.

Diabetes is a serious problem that affects millions of people worldwide. By combining the new method with FIR lasers that have recently been developed, Matsuura said compact and low-cost blood glucose measurement systems could soon be widely used in clinical fields.