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Method of determining the frequency characteristics of electrical impedance of tissue using wideband extenders

Michał Władziński

Abstract

The dissertation describes the measurement method for tissue impedance spectrometry. The new method of calculating spectrum impedance characteristics was introduced. The modulus characteristics and phase shifting are calculated from recorded waveforms of current extortion in circuit and voltage response of tested object. All extortions waveforms have constant spectral density in specified frequency band. The proper functioning of the method was verified in series of simulations. The simulations were performed using state-space representation of the measuring circuit and tissue equivalent circuit. As extortions waveforms with: limited time sinc(t) function and modulated sinc(t) function and the impulse response of FIR filter were used. The response for each extortion was calculated and used in the new method to determine impedance spectrum. The results of simulations were compared with analytical solution of a tissue model and the Pearson correlation coefficient was calculated. The value of the determined coefficients was approximately 0.99 for all used extortions. Analysis of the results proved correctness of measurements using the proposed measurement method. Investigating the possibility of measuring the impedance spectrum using the new method required an equivalent electrical circuit of tissue model. The circuit was built using passive elements which values were chosen based on literature studies. The performed measurements also required a new measuring system which extended properties of a digital oscilloscope and an arbitrary generator. The system consists of high precision differential amplifiers used in measurement circuits and voltage controlled current source used in extortion circuit. The measurements of impedance spectroscopy have been performed using the new method in comparison to frequency sweep technique. The results were compared by calculating the Pearson correlation coefficient. The value of the Pearson coefficient suggested high correlation between results of both methods. Analysis of the results showed that the impulse response of the FIR filter and the modulated sinc(t) function used as extortions waveforms give the best performance. The new measurement method has also been used with a signal averaging technique, which increased the correlation between characteristics. The final measurements were performed on a subject’s arm. The measuring system has been supplied with a battery source to separate from the power grids. In order to obtain the reference characteristics the frequency sweep measurements were performed. Analysis of the results proved that the proposed method enables measurement of the 9 impedance of tissue and determining both the impedance module and the phase shifting characteristics.
Record ID
WUTb88de050e2064cce87e017326c599593
Diploma type
Doctor of Philosophy
Author
Title in Polish
Metoda wyznaczania charakterystyk częstotliwościowych impedancji elektrycznej tkanek z zastosowaniem wymuszeń szerokopasmowych
Title in English
Method of determining the frequency characteristics of electrical impedance of tissue using wideband extenders
Language
(pl) Polish
Certifying Unit
Faculty of Mechatronics (FM)
Discipline
biocybernetics and biomedical engineering / (technology domain) / (technological sciences)
Status
Finished
Defense Date
24-05-2017
Title date
31-05-2017
Supervisor
Internal reviewers
Ewaryst Tkacz Ewaryst Tkacz,, External affiliation of publication: Silesian University of Technology
External reviewers
Antoni Nowakowski Antoni Nowakowski,, Author's external affiliation: Gdańsk University of Technology
Pages
98
Keywords in English
tissue impedance; bioimpedance spectroscopy; the impedance modulus characteristics; the phase shifting characteristics; the impulse response of FIR filter; modulated sinc(t) function
Abstract in English
The dissertation describes the measurement method for tissue impedance spectrometry. The new method of calculating spectrum impedance characteristics was introduced. The modulus characteristics and phase shifting are calculated from recorded waveforms of current extortion in circuit and voltage response of tested object. All extortions waveforms have constant spectral density in specified frequency band. The proper functioning of the method was verified in series of simulations. The simulations were performed using state-space representation of the measuring circuit and tissue equivalent circuit. As extortions waveforms with: limited time sinc(t) function and modulated sinc(t) function and the impulse response of FIR filter were used. The response for each extortion was calculated and used in the new method to determine impedance spectrum. The results of simulations were compared with analytical solution of a tissue model and the Pearson correlation coefficient was calculated. The value of the determined coefficients was approximately 0.99 for all used extortions. Analysis of the results proved correctness of measurements using the proposed measurement method. Investigating the possibility of measuring the impedance spectrum using the new method required an equivalent electrical circuit of tissue model. The circuit was built using passive elements which values were chosen based on literature studies. The performed measurements also required a new measuring system which extended properties of a digital oscilloscope and an arbitrary generator. The system consists of high precision differential amplifiers used in measurement circuits and voltage controlled current source used in extortion circuit. The measurements of impedance spectroscopy have been performed using the new method in comparison to frequency sweep technique. The results were compared by calculating the Pearson correlation coefficient. The value of the Pearson coefficient suggested high correlation between results of both methods. Analysis of the results showed that the impulse response of the FIR filter and the modulated sinc(t) function used as extortions waveforms give the best performance. The new measurement method has also been used with a signal averaging technique, which increased the correlation between characteristics. The final measurements were performed on a subject’s arm. The measuring system has been supplied with a battery source to separate from the power grids. In order to obtain the reference characteristics the frequency sweep measurements were performed. Analysis of the results proved that the proposed method enables measurement of the 9 impedance of tissue and determining both the impedance module and the phase shifting characteristics.
Thesis file
  • File: 1
    main rozprawa Michał Władziński.pdf
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Uniform Resource Identifier
https://repo.pw.edu.pl/info/phd/WUTb88de050e2064cce87e017326c599593/
URN
urn:pw-repo:WUTb88de050e2064cce87e017326c599593

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