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Dielectric Properties of Water Solutions with Small Content of
Glucose in the Millimeter Wave Band and the Determination of
Glucose in Blood
B. M. Garin, V. V. Meriakri, E. E. Chigrai, M. P. Parkhomenko, and M. G. Akat’eva
Kotel’nikov Institute of Radio Engineering and Electronics RAS, Fryazino Branch
Fryazino, Moscow Region 141190, Russia
Abstract— The dielectric properties of 0.9% NaCl in water with small content of sugar and
glucose, as well as of human skin, were measured in the millimeter (MM) waves range.
The measurement methods were chosen so that one could use them for the nondestructive control of glucose content (i.e., measurement only reflection of an electromagnetic wave, without
penetrating into the medium). To determine ε0 and ε00 , of lossy materials one usually measures
the power reflection coefficient and the phase of the reflected wave with the help of sophisticated
and expensive network vector analyzers. We developed a sufficiently simple method and scheme,
which consists in measuring the minimum of the power reflection coefficient R(f ) = Rmin (fmin )
and its frequency fmin in the cases of corresponding to this minimum from the following structures: a specially chosen plane-parallel matching plate made of a low-loss dielectric or resonator —
a medium under measurement with high losses (solution, blood, skin). This method was realized
in the MM waves range. Dielectric properties of glucose solutions in water and in a 0.9% NaCl
solution (physiological solution) have been measured. Also was measured dielectric properties os
human skin. The values of ε0 and ε00 have been measured near the elbow joint in the frequency
range from 30 to 80 GHz. Above 40 GHz, these data have been obtained for the first time,
whereas, at frequencies of 30–40 GHz, the values of ε00 obtained in our experiments are higher
than those available in the literature. Our method allows a real-time noninvasive determination
of glucose content in blood by measuring reflection on skin. We established a clear correlation
between glucose content W and the measured value of reflection coefficient as W increases after
an oral glucose tolerance test (OGTT) on an empty stomach. The functions Rmin (W ) show similar but individual behavior for each test person. It was established a correlation between glucose
content W after OGTT and the properties of skin. The results of the measurements described can
be used to implement real-time, including noninvasive, measurements of small glucose (sugar)
content in water, physiological solution, and blood.
1. INTRODUCTION
Investigations of the dielectric properties of sugar in water solutions, as well as blood imitators
and blood, in the millimeter (MM) wave range allow one to obtain valuable information on the
possibility of real-time control of glucose concentration in blood using MM waves. which is of huge
interest for diabetics [1, 2]. These investigations are also of interest for other applications such as
determination content of water solutions [3].
2. RESULTS AND DISCUSSION
Investigations of the dielectric properties of glucose in water solutions, as well as blood imitators and
blood, in the millimeter (MM) wave range allow one to obtain valuable information on the possibility
of real-time control of glucose concentration in blood using MM waves. These investigations are also
of interest for other applications such as determination content of water solutions. We investigated
using methods described in [4] dielectric properties of glucose solutions in blood imitator (0.9%
NaCl in water). Results are presented in Table 1.
Also we investigated dielectric properties of skin in the MM region. Table 2 presents results for
forearm, joint at frequencies from 30 to 80 GHz. Above 40 GHz, these data have been obtained for
the first time, whereas, at frequencies of 30–40 GHz, the values of ε00 obtained in our experiments
are higher than those available in the literature [5].
For measurements dependence of reflection from skin on glucose content we used the matching
insert consisting of the resonant cavity based on rectangular waveguide. (Fig. 3.) Directional
coupler measures the reflection coefficient R of the cavity back wall of which is the object of study
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Table 1: Dielectric properties of glucose solutions in blood imitator.
Table 2: Dielectric properties of skin in the MM region.
(in our case the skin). Operating frequency ranged from 30 to 35 GHz. The dimensions of the walls
of the waveguide a = 7, 2 mm, b = 3, 4 mm. The ratio of the calculations was found to be 0.31. The
size of a diaphragm was 2.28 mm. Fig. 1 presents measurement set up.
The series of experiments show a correlation between glucose content W and Rmin in the region
where W increases after taking glucose on an empty stomach at frequencies of about 40 and 60 GHz.
At the same time just as in [6], where the measurements were carried out in the infrared band, it
is needed individual calibration for different persons. Based on this series of measurements were
constructed plots, which shows how changes in time module of the reflection coefficient as a function
of time elapsed since the adoption of sugar. Fig. 2 presents typical dependences for three different
persons. It is evident that this changes are in good accordance with usual “sugar curve” within
one hour, which have one maximum and practically the same values for t = 0 and t = tmax .
Figure 3 presents comparison of dependences on time obtained with our noninvasive sensor and
standard optical invasive sensor for two different persons.
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Figure 1: Set up for measurement of reflection from skin.
Figure 2: The reflection coefficient as a function of
time after OGTT.
Figure 3: Comparison dependences on time obtained
with our noninvasive sensor and standard optical invasive sensor.
Note that in the afternoon (after 3–4 p.m.), a variation in R for close values of W was much
greater than that before the noon. This fact indicates to certain physiological changes in skin at
the depth d that are associated with physical activity, which were pointed out also in [6].
3. CONCLUSIONS
The values of ε0 and ε00 have been measured near the elbow joint in the frequency range from
30 to 80 GHz. Above 40 GHz, these data have been obtained for the first time. The series of
experiments show correlation between glucose content W and reflection coefficient on skin R in the
region where W increases after OGTT. It has been established that during OGTT dependences of
reflection coefficients from noninvasive resonator sensor have the same shape but different values
for different persons.
ACKNOWLEDGMENT
The work was supported by the Program of the Physical Science Department of the Russian
Academy of Sciences “Modern problems of Radiophysics” (Project “Terra-6”).
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