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Improvements in Bioimpedance SpectroscopyData Analysis: Artefact Correction, ColeParameters, and Body Fluid Estimation
KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The estimation of body fluids is a useful and common practice in the status assessment of diseasemechanisms and treatments. Electrical bioimpedance spectroscopy (EBIS) methods are non-invasive,inexpensive, and efficient alternatives for the estimation of body fluids. However, these methods areindirect, and their robustness and validity are unclear.Regarding the recording of measurements, a controversy developed regarding a spectrum deviationin the impedance plane, which is caused by capacitive leakage. This deviation is frequentlycompensated for by the extended Cole model, which lacks a theoretical basis; however, there is nomethod published to estimate the parameters. In this thesis, a simplified model to correct thedeviation was proposed and tested. The model consists of an equivalent capacitance in parallel withthe load.Subsequently, two other measurement artefacts were considered. Both artefacts were frequentlydisregarded with regard to total body and segmental EBIS measurements as their influence isinsignificant with suitable skin-electrode contact. However, this case is not always valid, particularlyfrom a textile-enabled measurement system perspective. In the estimation of body fluids, EBIS dataare fitted to a model to obtain resistances at low and high frequencies. These resistances can berelated to body fluid volumes. In order to minimise the influence of all three artefacts on theestimation of body fluids and improve the robustness and suitability of the model fitting the differentdomains of immittance were used and tested. The conductance in a reduced frequency spectrum wasproposed as the most robust domain against the artefacts considered.The robustness and accuracy of the method did not increase, even though resistances at low and highfrequencies can be robustly estimated against measurement artefacts. Thus, there is likely error in therelation between the resistances and volumes. Based on a theoretical analysis, state of the artmethods were reviewed and their limitations were identified. New methods were also proposed. Allmethods were tested using a clinical database of patients involved in growth hormone replacementtherapy. The results indicated EBIS are accurate methods to estimate body fluids, however they haverobustness limits. It is hypothesized that those limits in extra-cellular fluid are primarily due toanisotropy, in total body fluid they are primarily due to the uncertainty ρi, and errors in intra-cellularfluid are primarily due to the addition of errors in extracellular and total body fluid. Currently, theseerrors cannot be prevented or minimised. Thus, the limitations for robustness must be predicted priorto applying EBIS to estimate body fluids.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , 83 p.
Series
Trita-STH : report, ISSN 1653-3836 ; 2013:7
Keyword [en]
Bioimpedance, Cole, Body Fluid
National Category
Medical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-128529ISBN: 978-91-7501-874-4 (print)OAI: oai:DiVA.org:kth-128529DiVA: diva2:647886
Public defence
2013-10-04, Sal 3-264, Alfred Nobels allé 10, Fremingsberg, 13:00 (English)
Opponent
Supervisors
Note

QC 20130917

Available from: 2013-09-17 Created: 2013-09-12 Last updated: 2013-09-17Bibliographically approved
List of papers
1. Experimental validation of a method for removing the capacitive leakage artifact from electrical bioimpedance spectroscopy measurements
Open this publication in new window or tab >>Experimental validation of a method for removing the capacitive leakage artifact from electrical bioimpedance spectroscopy measurements
2010 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 11Article in journal (Refereed) Published
Abstract [en]

Often when performing electrical bioimpedance (EBI) spectroscopy measurements, the obtained EBI data present a hook-like deviation, which is most noticeable at high frequencies in the impedance plane. The deviation is due to a capacitive leakage effect caused by the presence of stray capacitances. In addition to the data deviation being remarkably noticeable at high frequencies in the phase and the reactance spectra, the measured EBI is also altered in the resistance and the modulus. If this EBI data deviation is not properly removed, it interferes with subsequent data analysis processes, especially with Cole model-based analyses. In other words, to perform any accurate analysis of the EBI spectroscopy data, the hook deviation must be properly removed. Td compensation is a method used to compensate the hook deviation present in EBI data; it consists of multiplying the obtained spectrum, Z meas (ω), by a complex exponential in the form of exp(–jωTd). Although the method is well known and accepted, Td compensation cannot entirely correct the hook-like deviation; moreover, it lacks solid scientific grounds. In this work, the Td compensation method is revisited, and it is shown that it should not be used to correct the effect of a capacitive leakage; furthermore, a more developed approach for correcting the hook deviation caused by the capacitive leakage is proposed. The method includes a novel correcting expression and a process for selecting the proper values of expressions that are complex and frequency dependent. The correctness of the novel method is validated with the experimental data obtained from measurements from three different EBI applications. The obtained results confirm the sufficiency and feasibility of the correcting method.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2010
Keyword
electrical bioimpedance spectroscopy; capacitive leakage; artifact removal
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-73065 (URN)10.1088/0957-0233/21/11/115802 (DOI)000285262000026 ()
Note
QC 20120209Available from: 2012-02-09 Created: 2012-02-01 Last updated: 2017-12-08Bibliographically approved
2. Cole parameter estimation from electrical bioconductance spectroscopy measurements
Open this publication in new window or tab >>Cole parameter estimation from electrical bioconductance spectroscopy measurements
2010 (English)In: 2010 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), IEEE Press, 2010, Vol. 2010, 3495-3498 p.Conference paper, Published paper (Refereed)
Abstract [en]

Several applications of Electrical Bioimpedance (EBI) make use of Cole parameters as base of their analysis, therefore Cole parameters estimation has become a very common practice within Multifrequency- and EBI spectroscopy. EBI measurements are very often contaminated with the influence of parasitic capacitances, which contributes to cause a hook-alike measurement artifact at high frequencies in the EBI obtained data. Such measurement artifacts might cause wrong estimations of the Cole parameters, contaminating the whole analysis process and leading to wrong conclusions. In this work, a new approach to estimate the Cole parameters from the real part of the admittance, i.e. the conductance, is presented and its performance is compared with the results produced with the traditional fitting of complex impedance to a depressed semi-circle. The obtained results prove that is feasible to obtain the full Cole equation from only the conductance data and also that the estimation process is safe from the influence capacitive leakage.

Place, publisher, year, edition, pages
IEEE Press, 2010
Series
IEEE Engineering in Medicine and Biology Society Conference Proceedings, ISSN 1557-170X
Keyword
BODY, BIOIMPEDANCE, IMPEDANCE
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-73051 (URN)10.1109/IEMBS.2010.5627790 (DOI)000287964003223 ()21097029 (PubMedID)978-1-4244-4124-2 (ISBN)
Conference
32nd Annual International Conference of the IEEE Engineering-in-Medicine-and-Biology-Society (EMBC 10), Buenos Aires, ARGENTINA, AUG 30-SEP 04, 2010
Note
© 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20120209Available from: 2012-02-09 Created: 2012-02-01 Last updated: 2013-09-17Bibliographically approved
3. Hook Effect correction & resistance-based Cole fitting prior Cole model-based analysis: Experimental validation
Open this publication in new window or tab >>Hook Effect correction & resistance-based Cole fitting prior Cole model-based analysis: Experimental validation
Show others...
2010 (English)In: Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2010, IEEE Engineering in Medicine and Biology , 2010, 6563-6566 p.Conference paper, Published paper (Refereed)
Abstract [en]

The analysis of measurements of Electrical Bioimpedance (EBI) is on the increase for performing non-invasive assessment of health status and monitoring of pathophysiological mechanisms. EBI measurements might contain measurements artefacts that must be carefully removed prior to any further analysis. Cole model-based analysis is often selected when analysing EBI data and might lead to miss-conclusion if it is applied on data contaminated with measurement artefacts. The recently proposed Correction Function to eliminate the influence of the Hook Effect from EBI data and the fitting to the real part of the Cole model to extract the Cole parameters have been validated on experimental measurements. The obtained results confirm the feasible experimental use of these promising pre-processing tools that might improve the outcome of EBI applications using Cole model-based analysis.

Place, publisher, year, edition, pages
IEEE Engineering in Medicine and Biology, 2010
Series
IEEE Engineering in Medicine and Biology Society Conference Proceedings, ISSN 1557-170X
Keyword
bioelectric phenomena, electric impedance measurement, medical signal processing, patient diagnosis, patient monitoring, Cole model-based analysis, EBI data, Hook effect correction, electrical bioimpedance, health status, noninvasive assessment, pathophysiological mechanisms, resistance-based Cole fitting
National Category
Medical Laboratory and Measurements Technologies Signal Processing
Identifiers
urn:nbn:se:kth:diva-74129 (URN)10.1109/IEMBS.2010.5627109 (DOI)000287964006240 ()
Conference
Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
Note
QC 20120215Available from: 2012-02-09 Created: 2012-02-02 Last updated: 2013-09-17Bibliographically approved
4. Cole parameter estimation from total right side electrical bioimpedance spectroscopy measurements: Influence of the number of frequencies and the upper limit
Open this publication in new window or tab >>Cole parameter estimation from total right side electrical bioimpedance spectroscopy measurements: Influence of the number of frequencies and the upper limit
2011 (English)In: 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), 2011, 1843-1846 p.Conference paper, Published paper (Refereed)
Abstract [en]

Applications based on measurements of Electrical Bioimpedance Spectroscopy (EBIS) analysis are proliferating. The most spread and known application of EBIS is the non-invasive assessment of body composition. Fitting to the Cole function to obtain the Cole parameters, R<sub>0</sub> and R<sub>&#x221E;</sub>, is the core of the EBIS analysis to obtain the body fluid distribution. An accurate estimation of the Cole parameters is essential for the Body Composition Assessment (BCA) and the estimation process depends on several factors. One of them is the upper frequency limit used for the estimation and the other is the number of measured frequencies in the measurement frequency range. Both of them impose requirements on the measurement hardware, influencing largely in the complexity of the bioimpedance spectrometer. In this work an analysis of the error obtained when estimating the Cole parameters with several frequency ranges and different number of frequencies has been performed. The study has been done on synthetic EBIS data obtained from experimental Total Right Side (TRS) measurements. The results suggest that accurate estimations of R<sub>0</sub> and R<sub>&#x221E;</sub> for BCA measurements can be achieved using much narrower frequency ranges and quite fewer frequencies than electrical bioimpedance spectrometers commercially available nowadays do.

Keyword
biomedical equipment, electric impedance measurement, electrochemical impedance spectroscopy, frequency estimation, measurement errors, Cole parameter estimation, bioimpedance spectrometer, body composition assessment, body fluid distribution, error analysis, measurement hardware, total right side electrical bioimpedance spectroscopy measurements
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-74134 (URN)10.1109/IEMBS.2011.6090524 (DOI)000298810001243 ()2-s2.0-84055193230 (Scopus ID)978-1-4244-4121-1 (ISBN)
Conference
33rd Annual International Conference of the IEEE Engineering-in-Medicine-and-Biology-Society (EMBS). Boston, MA. AUG 30-SEP 03, 2011
Note
QC 20120329Available from: 2012-02-02 Created: 2012-02-02 Last updated: 2013-09-17Bibliographically approved
5. Cole Parameter Estimation from the Modulus of the Electrical Bioimpeadance for Assessment of Body Composition: A Full Spectroscopy Approach
Open this publication in new window or tab >>Cole Parameter Estimation from the Modulus of the Electrical Bioimpeadance for Assessment of Body Composition: A Full Spectroscopy Approach
2011 (English)In: Journal of Electrical Bioimpedance, ISSN 1891-5469, E-ISSN 1891-5469, Vol. 2, 72-78 p.Article in journal (Refereed) Published
Abstract [en]

Activities around applications of Electrical Bioimpedance Spectroscopy (EBIS) have proliferated in the past decade significantly. Most of these activities have been focused in the analysis of the EBIS measurements, which eventually might enable novel applications. In Body Composition Assessment (BCA) the most common analysis approach currently used in EBIS is based on the Cole function, which most often requires curve fitting. One of the most implemented approaches for obtaining the Cole parameters is performed in the impedance plane through the geometrical properties that the Cole function exhibit in such domain as depressed semi-circle. To fit the measured impedance data to a semi-circle in the impedance plane, obtaining the Cole parameters in an indirect and sequential manner has several drawbacks. Applying a Non-Linear Least Square (NLLS) iterative fitting on the spectroscopy measurement, obtains the Cole parameters considering the frequency information contained in the measurement. In this work, from experimental total right side EBIS measurements, the BCA parameters have been obtained to assess the amount and distribution of whole body fluids. The values for the BCA parameters have been obtained using values for the Cole parameters estimated with both approaches: circular fitting on the impedance plane and NLLS impedance-only fitting. The comparison of the values obtained for the BCA parameters with both methods confirms that the NLLS impedance-only is an effective alternative as Cole parameter estimation method in BCA from EBIS measurements. Using the modulus of the Cole function as the model for the fitting would eliminate the need for performing a phase detection in the acquisition process, simplifying the hardware specifications of the measurement instrumentation when implementing a bioimpedance spectrometer.

Place, publisher, year, edition, pages
Oslo: University of Oslo, 2011
Keyword
Bioimpedance, spectroscopy measurements, Cole Analysis, Body Composition
National Category
Medical Laboratory and Measurements Technologies Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-73199 (URN)10.5617/jeb.197 (DOI)
Note
QC 20120214Available from: 2012-02-14 Created: 2012-02-01 Last updated: 2017-12-08Bibliographically approved
6. Robust approach against capacitive coupling for the estimation of body fluids using clinical bioimpedance spectroscopy measurements
Open this publication in new window or tab >>Robust approach against capacitive coupling for the estimation of body fluids using clinical bioimpedance spectroscopy measurements
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-128805 (URN)
Conference
33rd Annual International Conference of the IEEE Engineering-in-Medicine-and-Biology-Society (EMBS). Boston, MA. AUG 30-SEP 03, 2011
Note

QS 2013

Available from: 2013-09-17 Created: 2013-09-17 Last updated: 2013-09-17Bibliographically approved
7. Estimation of body fluids with bioimpedance spectroscopy: state of the art methods and proposal of novel methods
Open this publication in new window or tab >>Estimation of body fluids with bioimpedance spectroscopy: state of the art methods and proposal of novel methods
Show others...
2015 (English)In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 36, no 10Article in journal (Refereed) Published
Abstract [en]

Determination of body fluids is a useful common practice in determination of disease mechanisms and treatments. Bioimpedance spectroscopy (BIS) methods are non-invasive, inexpensive and rapid alternatives to reference methods such as tracer dilution. However, they are indirect and their robustness and validity are unclear. In this article, state of the art methods are reviewed, their drawbacks identified and new methods are proposed. All methods were tested on a clinical database of patients receiving growth hormone replacement therapy. Results indicated that most BIS methods are similarly accurate (e.g. < 0.5 +/- 3.0% mean percentage difference for total body water) for estimation of body fluids. A new model for calculation is proposed that performs equally well for all fluid compartments (total body water, extra-and intracellular water). It is suggested that the main source of error in extracellular water estimation is due to anisotropy, in total body water estimation to the uncertainty associated with intracellular resistivity and in determination of intracellular water a combination of both.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
Keyword
bioimpedance, body composition, body fluids estimation
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-128807 (URN)10.1088/0967-3334/36/10/2171 (DOI)000367690500013 ()2-s2.0-84947596900 (Scopus ID)
Note

Updated from manuscript to article in journal.

QC 20160201

Available from: 2013-09-17 Created: 2013-09-17 Last updated: 2017-12-06Bibliographically approved

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