RU2718258C1 - Method of non-invasive determination of blood glucose concentration - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: method for non-invasive blood glucose measurement involves the following actions. Blood-containing area of the human body is exposed to near-infrared light at a selected wavelength, light transmitted through the body portion is received, and its intensity is measured. Taking into account known factors of light absorption by components at the given wavelength, dependency of this light intensity on concentrations of components contained in blood is made. Measurement of intensity is repeated at different wavelengths of near-infrared light, wherein number of wavelengths on which measurements are taken is equal to the number of blood components. Analogously there is plotted dependence of measured light intensity on concentration. System is composed of all obtained equations and solved relative to the desired concentration of glucose. Additional measurements of light intensities are carried out, namely, additional measurements are taken at additionally selected wavelengths and repeated measurements at all selected wavelengths are performed. Dependences of intensity of the received light on concentrations of blood components are calculated with due allowance for known light absorption coefficients at each i-th wavelength for each absorbing component in the form of

for each i-th wavelength, on which measurements were taken, for N blood components and solving system of equations relative to desired concentration of glucose.

EFFECT: technical result consists in improvement of accuracy of measuring intensity of received light, based on which glucose concentration is determined.

1 cl

Description

A non-invasive method for determining the concentration of glucose in the blood relates to measurements for diagnostic purposes and is intended for non-invasive determination of the amount of glucose in the blood of a person.

A known method of non-invasive determination of blood glucose based on infrared spectroscopy (Optical methods for non-invasive determination of blood glucose // Medical equipment. 2011. No. 6. P. 29-33). The method involves transmitting monochromatic radiation through an object (lips, tongue, wings of the nose, cheeks, fingers, etc.), registering the transmitted radiation with a detector, processing the measurement results using a microcontroller, and also outputting the received data to a display.

The disadvantage of this method is that the method does not take into account that radiation is absorbed not only by glucose, but also by other absorbers: water, melanin and other components contained in the blood and human tissues. Moreover, data on the absorption of radiation at a certain wavelength is not enough to determine the glucose concentration, since it is necessary to determine for what proportion of the absorbed radiation glucose is responsible. There is no data for such a determination in measurements at a specific wavelength. Therefore, the accuracy of measurements by this method is extremely small.

A known method (RF Patent No. 2574571, publ. 02/10/2016, bull. No. 4) non-invasively determine the concentration of glucose in the blood, including irradiating a portion of human tissue with light near the infrared wavelength range, receiving diffusely reflected tissue light, converting the received optical radiation into electrical signal and determining the concentration of glucose in the blood based on the received electrical signal. Biological tissue is irradiated alternately in five subranges of the near infrared region of the spectrum, and the determination of glucose concentration in the blood is obtained using experimentally obtained calibration curves. In this method, the need to regularly obtain experimental calibration curves virtually eliminates the possibility of creating an individual application device based on this method, which is its drawback. In addition, the number of absorbing components in human biological tissue can be quite large, and five measurements in different sub-bands of wavelengths may not be enough to calculate the glucose concentration

The closest analogue of the proposed method is a method ("Non-invasive determination of the concentration of glucose in the blood using a polychromatic light source with a controlled spectrum" // Biomedical Radioelectronics, No. 8, 2016), which includes irradiating a blood-containing area of the human body with light from the near infrared spectrum, receiving light passing through this site, measuring its intensity and determining the concentration of glucose in the blood based on the received intensity. For measurement at each wavelength, a dependence of the concentrations of the components that make up the blood on the intensity is calculated taking into account the known coefficients of light absorption at this wavelength for each absorbing component.

In accordance with the method, measurements are made on the number N of wavelengths equal to the number of blood components within the spectral range, and for each of the measurements, a dependence with N unknowns is compiled. To measure at the i-th wavelength of the spectral range, you can write the equation:

where k _ij are the known coefficients of light absorption at the i-th wavelength for the j-th absorbing component, x _j is the unknown concentration for the j-th absorbing component, and I _i is the result of measuring the intensity of the absorbed light at the i-th wavelength, where i = 1 ... N.

As a result, you can get a system of N linear equations with N unknowns, which can be quickly solved with the help of not too complicated software. One solution to this system of equations will be the concentration of glucose in the blood.

The disadvantage of this method is the low accuracy of determining the concentration of glucose associated with a high error in measuring the intensity of absorbed light, which leads to a high probability of convergence of the system of linear equations.

The objective of the present invention is to improve the accuracy of non-invasive determination of glucose concentration in human blood.

The technical result consists in increasing the accuracy of measuring the intensity of the received light, on the basis of which the glucose concentration is determined.

для каждой i-ой длины волны, на которой проводились измерения, для N компонентов крови и решают систему уравнений относительно искомой концентрации глюкозы.The technical result is achieved due to the fact that the method of non-invasive determination of the concentration of glucose in the blood provides for the following steps. The blood-containing part of the human body is irradiated with light from the near infrared region at the selected wavelength, the light transmitted through this part of the body is received and its intensity is measured. Taking into account the known coefficients of light absorption by the components at a given wavelength, the dependence of this light intensity on the concentrations of the components contained in the blood is made up. The intensity measurement is repeated at different wavelengths of light of the near infrared region, while the number of wavelengths at which measurements are taken is equal to the number of blood components. Similarly, the measured light intensity is a function of concentration. They compose a system from all the equations obtained and solve it with respect to the desired glucose concentration. Additional measurements of light intensities are carried out, namely, additional measurements are carried out at additionally selected wavelengths and repeated measurements are taken at all selected wavelengths. The dependences of the received light intensity on the concentrations of blood components are compiled taking into account the known light absorption coefficients at each i-th wavelength for each absorbing component in the form

for each i-th wavelength at which measurements were made, for the N components of the blood, a system of equations is solved for the desired glucose concentration.

The achievement of the technical result is due to a decrease in the influence of the error in measuring the intensity by increasing the number of wavelengths at which measurements are made, as well as an increase in the number of measurements of light intensity at each wavelength, that is, by obtaining additional values of the intensities of the absorbed light. These actions make it possible to obtain additional relationships between the concentrations of absorbing blood components and the measured intensities at each wavelength.

The invention consists in the following. At various wavelengths of the near infrared range within the range of 700 ... 1100 nm, a blood-containing area of the body (earlobe) is irradiated, light transmitted through this area is received, and the intensity of the received radiation is measured. The number of wavelengths corresponds to the number N of components that absorb radiation. Next, additional wavelengths are selected and the actions of irradiation and reception of light are repeated, thus obtaining additional intensity measurements. Then, in the same way, repeated measurements are carried out at each of the selected wavelengths and additional values of light intensity are obtained. If measurements are taken at M wavelengths within the spectral range, then for each of the measurements, one can write an equation with M unknowns. The spectral characteristics of all absorbing components (glucose, water, melanin, other impurities contained in the blood and tissues) are well known.

For each of the wavelengths, the equation is compiled:

where k _ij are the known coefficients of light absorption at the i-th wavelength for the j-th absorbing component (reference values), x _j is the unknown concentration for the j-th absorbing component, where i = 1 ... M, I ₀ is the known light intensity irradiation, I is the intensity of the received light.

Further, the equations compiled for each measurement are compiled into the system. As a result, you can get a system of M linear equations with M unknowns, one of the solutions to this system of equations is the concentration of glucose in the blood.

Carrying out additional measurements to obtain the values of the intensities of the absorbed light ensures the convergence of the system of equations. This system of equations can be solved by the Gauss method, which provides for the sequential exclusion of unknowns with a parallel reduction in the number of analyzed equations, relative to the concentrations of absorbing components, among which the concentration of glucose in the blood is also determined. The solution of the system of equations by the Gauss method is most appropriate, since it gives the best results in cases where the components have substantially different spectral absorption characteristics. The use of such a solution method ensures the convergence of the system of equations, and, therefore, the accuracy of determining the concentration of glucose in the blood

The method can be implemented as follows. The wavelength of the infrared range is selected, from a source of infrared light, the radiation of the selected wavelength is transmitted through the light guide to the radiation input device in the blood-containing part of the body (earlobe) of a person. As such a device, for example, a clip fixed to the earlobe can be used. As a light source, a universal source of polychrome optical radiation can be used (RF Patent No. 2287736, Bull. 32, November 20, 2006), which is software-controlled and allows you to quickly switch wavelengths for a large number of measurements. The light that passed through the body section through the fiber enters the processing device, the spectrometer, where its intensity is measured. Taking into account the known light absorption coefficients, each component compiles the dependence of the measured intensity on the concentrations of blood components according to the formula (2). After repeating the measuring steps in accordance with the formula, a system of equations is obtained that can be solved by the Gauss method and one of the solutions of which is the desired glucose concentration.

Thus, using the proposed method, an increase in the accuracy of measuring the concentration of glucose in the blood is achieved.

Claims (1)

A non-invasive method for determining the concentration of glucose in the blood, in which the blood-containing part of the human body is irradiated with light from the near infrared region at a selected wavelength, the light transmitted through this part of the body is received, its intensity is measured, and, taking into account the known light absorption coefficients, the components at this wavelength make up the dependence this light intensity from the concentrations of the components contained in the blood, repeat the measurement of the intensity at different wavelengths of light near infrared region ty, while the number of wavelengths at which measurements are made is equal to the number of blood components, similarly make up the dependence of the measured light intensity on concentrations, make up the system from all the equations obtained and solve it with respect to the desired glucose concentration, characterized in that additional light intensity measurements are carried out namely, they carry out additional measurements at additionally selected wavelengths and perform repeated measurements at all selected wavelengths, make up the dependencies ensivnosti received light on the concentrations of blood components based on known light absorption coefficients in each i-th wavelength for each component of the absorbent in the form of

for each ith wavelength at which measurements were taken, for the N blood components, a system of equations is solved for the desired glucose concentration.