CC BY
8УДК 616.053.(035.3)
AN INTEGRATED MULTI-FREQUENCY METHOD FOR ESTIMATING BODY
COMPOSITION
RAHiMOV RAHiM MOHAMMED
Department of Engineering Physics and Electronics, Faculty of Energy and Automation, Azerbaijan Technical University, Baku, Azerbaijan
GADiR GAFAROV ARZU
Department of Engineering Physics and Electronics, Faculty of Energy and Automation, Azerbaijan Technical University, Baku, Azerbaijan
Abstract: To measure the impedance of a specific body segment, the current and measuring electrodes must be positioned accordingly. The main structural element of the biological system is the cell, which consists of the cytoplasm and the membrane surrounding it. The cell membrane acts as a barrier between the intracellular fluid and the extracellular fluid. In our proposed method, the frequency ratio is in the range of 3:4:5. This means that if we take the high frequency as 500kHz then 3 other frequencies should be taken 166kHz, 41kHz and 8kHz.
Key words: Bioimpedance analysis, electrical conductivity, body segment impedance, multi-frequency method
The integrated multi-frequency method is performed by the integrated single-frequency method with the same position of the electrodes, but measurements are made at several frequencies. The main purpose of the multi-frequency method is to estimate the volume of water (VOW) and the composition of extra-tissue fluid (ETF) in the human body more reliably than the single-frequency method allows. At the moment, it is not possible to specify VOW and ETF measurement frequencies that can be called generally accepted. To assess VOW, the probing current must freely enter the cells through the membranes. For this, the frequency should be as high as possible. At the same time, with increasing frequency, errors caused by parasitic capacitances increase, radiation of electromagnetic waves into the surrounding space increases, and the solution of some other technical issues becomes complicated. A frequency of 500 kHz is used in many commercial and research instruments. However, even at this frequency, the effect of cell membrane capacitance is not completely eliminated. ETF volume estimation should be performed at the lowest possible frequency so that alternating current does not penetrate cells through cell membrane capacitances and therefore intracellular fluid does not contribute to overall conductance. Many bioimpedance analyzers use a frequency of 5 kHz. With a further decrease in frequency, the impedances of the skin contacts of the electrodes increase rapidly, which complicates the measurements and leads to an increase in errors. Recall that in an ideal situation, to estimate the volume of VOW, it is necessary to measure the impedance at an infinitely high frequency, and to estimate the volume of ETF, it is necessary to measure the impedance at a frequency equal to zero. Such measurements are not possible. Estimates of object resistance at zero and infinitely high frequencies are obtained using the bioimpedance spectroscopy (BIS) method. In a standard device, the active and reactive components of the impedance are measured at multiple frequencies in the range of 5-500 kHz. The number of different frequencies should be at least 15-20 [14], and their sequence should be described by at least approximately a logarithmic law. In this example, the number of frequencies is 31. Measurement results are shown in square form. Then, based on these results, an approximation of the Cole model described by the formula is found [4, 7, 8, 15].
E 5
60 40 20 0 -20 40 ■60
.,1-..,........
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ину 5 ......
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zz 1 ™ 1. •• zzzzz. - —•■ ~ .......... ••1
.WO 4i Ml 420 440 460 4K0 54NI 520 540 560 K. Ohm
Figure 1. Approximation of the impedance spectrum according to the Cole model
The hodograph plot for the Cole model appears as a semicircle. The crosses on the hodograph indicate the positions of the points for the same frequencies at which the measurements were made. The resistances R0 and Rm correspond to the points of intersection with the axis of the active resistance R of the approximate hodograph, since the reactance of any passive circuit at zero and infinitely high frequencies is zero (Fig. 1).
Calculations with series and parallel equivalent circuits and measurement at 50 kHz with measurements at 50 kHz or 5 kHz or 500 kHz estimated from approximate resistance values at zero and infinitely high frequencies, including the mixture model, were investigated. For VOW and ETF, regression equations in their simplest form (kDT2/R) + const were used for each of the compared methods. The equations for VOW had the same form, but at 50 kHz, reactance was used instead of active resistance, when measuring at 500 kHz, the combination of active resistances at 5 kHz and 500 kHz was taken as resistance.
Measurements were performed on volunteers using the same Xitron Technologies bioimpedance spectrometer. Deuterium dilution was used as the reference method for VOW, NaBr dilution was used for ETF, and the tissue fluid (TIF) value was determined as the difference between VOW and ETF.
In our proposed method, the frequency values should be in the range of 3:4:5. This means that if we take the high frequency as 500kHz then 3 other frequencies should be taken 166kHz, 41kHz and 8kHz. It can be concluded that the 4-frequency method with measurements at 8kHz, 41kHz, 166kHz and 500kHz and the Cole fit method provide better accuracy than the other methods. The deterioration of the reliability of the estimates obtained at a frequency of 50 kHz is explained by the violation of the VOW / ETF ratio during impacts.
The main structural element of the biological system is the cell, which consists of the cytoplasm and the membrane surrounding it. The cell membrane acts as a barrier between the intracellular fluid and the extracellular fluid. From a technical point of view, it can be said that the electrical resistance of the biological system changes depending on the cell structure, that is, the physical-chemical exchange between the internal environment of the cell and its external environment. Depending on the research methodology (determination of body mass index, fat ratio, dry muscle ratio in the bioimpedance analyzer), the resistance of biological system elements is determined. Apparently, electrical resistance is a diagnostic information carrier for a biological system [2, 9, 10].
As we mentioned, depending on the research methodology (measurement of the electrical conductivity of the biological system), both constant and alternating current can be used as a stable source in the measurement circuit. Each form of current will produce unique biophysical effects in a
Impact Factor: SJIF 2019 - 5.11 TE^HHK^ ^YKH
2020 - 5.497
2021 - 5.81
biological system [1, 2, 9]. It is appropriate to use those biophysical effects in the study of the properties of the biological system. It is preferable to use an alternating current source as a stable source, especially if the phenomenon of polarization is taken into account. When applied from a low-frequency alternating current source, the probe current does not enter the cell membrane and flows through the circuit in proportion to the resistance of the extracellular fluid. When a high-frequency current source is used, the probe current will flow through the circuit depending on the resistance of the cell membrane and extracellular fluid. Electrical modeling is used to calculate the probe current and electrical conductivity of the seed based on the structure of the biological system. When a low-frequency current flows through the tissue, this process is modeled by a resistor, and when a high-frequency current flows, the cell membrane is modeled by capacitance, and the intracellular and extracellular fluid are modeled by resistors. The mentioned model is shown in the figure below (fig. 2).
Figure 2. RC circuit model for determining the electrical resistance of a biological system
Here, Rx is the extracellular fluid resistance, Rd is the intracellular fluid resistance, Cm is the membrane capacitance, and Z is the complex resistance [4].
As is known, the impedance of the biological tissue changes depending on the probe current of different frequencies. The law of variation of working voltage with angular frequency and small amplitude is as follows.
AV = Vm sin Mt = Vm sin(2nft) (1)
Under the influence of internal voltage, the current will be expelled from the circuit with a certain phase shift. The law of variation of the probing current will be as follows.
AI = Im sin(2nft - 9) (2)
Equations (1) and (2) can be used to determine the complex resistance expression of a biological object.
Z = Vm/j eJe (3)
lm
Equation (4) can be obtained using the Euler equations of equation (3).
Z =
= ejut-Kut-e) = e}0 = C0SQ + isin0
(4)
J ej(ut-e)
z0 = ml\ if we accept, we can write as follows.
lm
z(w) = z0cosd + isind (5)
If we look at the model in Figure 2, we can see that by determining the voltages Vz and Va and the ratio of the current flowing through the circuit, the complex resistance can be calculated. Assume
Impact Factor: SJIF 2019 - 5.11 TE^HHK^ ^Y^
2020 - 5.497
2021 - 5.81
that the current flowing through Zx and Ra is equal to each other (lx = Ia). Then we can determine the ratio of voltages Vz and Vawith the following expression.
Vz IZX Zx
Va IRa Ra
(6)
Based on expression (6), we can define the following expression.
Vz \Vz\A(p1 Vz
x ava a\va\Ay2 ava
With the help of this equation, the bioimpedance of the biological tissue can be determined
[5,6].
Conculision
In bioimpedance analysis, the active and reactive impedances of the human body or its segments are measured at different frequencies. Based on them, body structure characteristics such as fat, cellular and skeletal muscle mass, volume and distribution of body water are calculated. The widespread use of body mass index (BMI) is due to the simplicity and availability of measurements. Numerous studies have shown that deviation of BMI from normal values is associated with increased risk of morbidity and mortality. A relationship between relative mortality risk and BMI has been established. Electrical modeling is used to calculate the probe current and electrical conductivity of the seed based on the structure of the biological system. When a low-frequency current flows through the tissue, this process is modeled by a resistor, and when a high-frequency current flows, the cell membrane is modeled by capacitance, and the intracellular and extracellular fluid are modeled by resistors. In our proposed method, the values of the frequency should be in the range of 3:4:5. This means that if we take the high frequency of 500 kHz, then 3 other frequencies should be taken: 166 kHz, 41 kHz and 8 kHz. It can be concluded that 8 kHz, 41 kHz, 166 kHz and 500 kHz. The 4-frequency method with measurements at , and the Cole fit method provide better accuracy than the other methods.
REFERENCE
1. Gafarov GA Acupuncture research methods Journal of Applied Biotechnology and Bioengineering: 2020;7(6): Pages. 276-278.
2. Gafarov Gadir Biologically Active Points Studies, applications and technical possibilities LAP LAMBERT Academic Publishing ISBN: 978-620-5-48911-6 pp. 68, 2022.
3. Anna Dubiel Bioelectrical impedance analysis in medicine. World Scientific News 125 (2019) 127138.
4. Xiue Gao, Jia Tang Human Bioelectrical impedance Measuring Method Based onPrinciple of Multi-frequency and Multi-segment. 2011 International Conference on Advances in Engineering, Procedia Engineering 24 (2011) 459 - 4631877.
5. Luo, Y.-F. A Multi-Frequency Electrical Impedance Spectroscopy Technique of Artificial Neural Network-Based for the Static State of Charge. Energies 2021, 14, 2526.
6. Sermin Sengun, Atilla Uslu, Salih Aydin Application of Multifrequency Bioelectrical Impedance Analysis Method for the Detection of Dehydration Statusin Professional Divers. Medicina (Kaunas) 2012; 48 (4): 203-10.
7. W J Hannan, S J Cowen, C E Plester, K C Fearon, A deBeau Comparison of bio-impedance spectroscopy and multi-frequency bio-impedance analysis for the assessment of extracellular and total body water in surgical patients. Clin Sci (Lond) (1995) 89 (6): 651-658.
8. Charu Pawar, Munna Khan, J.P. Saini Design and Analysis of Adjustable Constant Current Source with MultiFrequency for Measurement of Bioelectrical Impedance. International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 1 (2018) pp. 262-267.
9. Gafarov Gadir Determination Of Informative Parameters In The Diagnosis On The Basis Of Biologically Active Points International Journal of Academic Health and Medical Research (IJAHMR) ISSN: 2643-9824 Vol. 5 Issue 9, September - 2021, Pages: 32-35.
10. Gafarov Gadir, Rustamova Durdane Biologically Active Points and Application Possibilities in Medicine. International Journal of Academic Health and Medical Research (IJAHMR)ISSN: 2643-9824Vol. 6 Issue 11, November - 2022, Pages: 1-4.
11. Gabriel S., Lau R.W., Gabriel C. The dielectric properties of biological tissue: II. Measurements in the frequency range 10 Hz to 20 GHz // Phys. Med. Biol. 1996a. Vol. 41, N 11. P. 2251-2269.
12. Bolton M.P., Ward L.C., Khan A. et al. Sources of error in bioimpedance spectroscopy // Physiol. Meas. 1998. Vol. 19. P. 235-245.
13. Nikolaev D., Smirnov A., Tarnakin A. Bioimpedance analysis with automatically electrode commutation in equipment for intensive care unit // Proc. XI Intern. conf. on electrical bioimpedance. Oslo, 2001.
14. Cornish B.H., Jacobs A., Thomas B.J., Ward L.C. Optimizing electrode sites for segmental bioimpedance measurements // Physiol. Meas. 1999. Vol. 20. P. 241- 250.
15. Ward L.C., Cornish B.H. Multiple frequency bioelectrical impedance analysis: howmany frequencies to use? // Proc. XII Intern. conf. on electrical impedance & VIntern. conf. on electrical impedance tomography. Gdansk, 2004. Vol. 1, P. 321-324.
