Dielectrical properties of living epidermis and dermis in the frequency range from 1 kHz to 1 MHz

Tsai, B.; Xue, Hansong; Birgersson, Erik; Ollmar, Stig; Birgersson, Ulrik

doi:10.2478/joeb-2019-0003

Cited by 28 publications

(29 citation statements)

References 40 publications

(41 reference statements)

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“…• The scalp can be represented by forearm human skin measurements by above 1 MHz, and below 1 MHz as a single entity by the forearm deep tissue skin measurements by Yamamoto and Yamamoto (1976) and as the dermis and epidermis separately between 1 kHz and 1 MHz by Tsai et al (2019).…”

Section: Discussionmentioning

confidence: 99%

“…They corrected their results to account for lead inductance and electrode polarisation. Figure 1 shows the conductivity of skin (and location when identified) extracted from and the conductivity derived from the resistivity measurements of Yamamoto and Yamamoto (1976) and Tsai et al (2019). Figure 2 shows the permittivity of skin extracted from Yamamoto and Yamamoto (1976), Tsai et al 2019, and .…”

Section: Scalpmentioning

confidence: 99%

“…Muscle conductivity. electrical properties of the stratum corneum and deep tissue skin using the two terminal method and compensating for the effect of lead wire stray impedance and electrode polarisation Tsai et al (2019). also measured the dielectric properties of different layers of human forearm skin in vivo over the frequency range of 1 kHz to 1 MHz…”

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confidence: 99%

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Analysis of the validity of the mathematical assumptions of electrical impedance tomography for human head tissues

Williams

Bouazza-Marouf

Zecca

et al. 2021

Biomed. Phys. Eng. Express

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Objective: To determine the validity of the key mathematical assumptions used in electrical impedance tomography for human head tissues. Approach:Conductivity and permittivity data collected from available literature for each tissue within the human head have been evaluated and critiqued. The most relevant dielectric tissue data for each tissue was then used to assess the validity of the mathematical assumptions of electrical impedance tomography in terms of their suitability for human head imaging in order to estimate related errors. Main Results:For induced currents with frequencies greater than 200 Hz the internal current source density is negligible. The assumption that magnetic effects are negligible is valid to an error of 1.7% for human head tissues for frequencies below 1 MHz. The capacitive effects are negligible for CSF, dura mater, blood, bone (cortical), and deep tissue skin for frequencies less than 3.2 MHz, 320 kHz, 25 kHz, 3.2 kHz, and 130 Hz respectively. However, the capacitive effects are not negligible for brain tissues, as the minimum error for brain tissues across the frequency range of 10 Hz to 100 GHz is 6.2% at 800 Hz, and the maximum error is 410% at 20 GHz. Significance:It is often assumed that the mathematical reduction of the base equations is valid for human head tissues over a broad frequency range; this study shows that these assumptions are not true for all tissues at all frequencies. False assumptions will result in greater errors and local distortions within tomographic images of the human head using electrical impedance tomography. This study provides the relationships between injected current frequency and the validity of the mathematical assumptions for each individual tissue, providing greater awareness of the magnitude of possible distortions.

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Section: Discussionmentioning

confidence: 99%

Section: Scalpmentioning

confidence: 99%

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Analysis of the validity of the mathematical assumptions of electrical impedance tomography for human head tissues

Williams

Bouazza-Marouf

Zecca

et al. 2021

Biomed. Phys. Eng. Express

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show abstract

“…Electrical impedance spectroscopy (EIS) has been widely used in biomedical applications for biological tissues' characterization [6], for disease identification, such as diabetes [7][8][9], for body composition analysis [10], for cardiac functions monitoring [11,12], for muscles' condition monitoring during sport activity [13], in dentistry [14] and in many other diagnostic fields.…”

Section: Introductionmentioning

confidence: 99%

Portable Knee Health Monitoring System by Impedance Spectroscopy Based on Audio-Board

et al. 2021

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Knee injuries are among the most common health problems in the world. They not only affect people who practice sports, but also those who lead a rather sedentary life. Factors such as age, weight, working and leisure activities can affect the health of the knees, causing disorders such as inflammation, edema, deterioration of cartilage and osteoarthritis. Although for the diagnosis and treatment of the various pathologies it is always advisable to contact orthopedists and specialized structures, it would often be useful to monitor the state of health of the knees in order to evaluate the healing (or worsening) process and the effects of sport/motion activities or rehabilitation. In this perspective, a portable knee health monitoring system was developed to be used at home or in gyms and sports environments in general. Besides requiring a simple custom front end, the system relies on a PC audio board capable of a sampling rate of 192 kHz to perform bioimpedance measurements at frequencies in excess of 50 kHz. A simple numerical calibration procedure allows to obtain high accuracy while maintaining low hardware complexity. The software developed for the operation of the system is freely available to any researcher willing to experiment with the bioimpedance measurement approach we propose, ensuring the conditions of portability and low complexity. Primary (intracellular and extracellular resistances and cell membrane capacitance) and secondary (real and imaginary parts of the total impedance) bioimpedance parameters can be obtained and analyzed through direct measurements with reference to an equivalent circuit model. The functionality of the system has been tested on nine subjects with different well-known health conditions, providing encouraging results in terms of the ability to correlate bioimpedance measurements to the health status of the knees. If proper clinical trials were to confirm our preliminary results, a system such as the one we propose could be used for fast and frequent monitoring of knee joints, thus possibly reducing the frequency at which complex and expensive medical exams, sometimes involving long waiting lists, must be performed.

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“…Physiological Properties of the Epidermis, Dermis, Fat, Fibrous septa and Muscle[22,[26][27][28][29] …”

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confidence: 99%

Effect of the Combination of Different Electrode Spacings and Power on Bipolar Radiofrequency Fat Dissolution: A Computational and Experimental Study

et al. 2020

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Background and Objectives The finite element method was used, and experiments were performed to analyze the effect of different electrode spacings and power combinations on the electrical and thermal aspects of biological tissues during bipolar radiofrequency (RF) fat dissolution. Through these efforts, this study also attempted to develop a reasonable electrode spacing and power combination that can achieve fat dissolution effects, the RF energy of which will not thermally damage the tissue. Study Design/Materials and Methods COMSOL was adopted to conduct a finite element analysis for bio‐thermoelectric coupling, and a two‐dimensional time‐domain model of biological tissue was built. A self‐developed single‐channel bipolar RF device was employed to load RF energy on the ex vivo porcine abdominal tissue. The thermal characteristics of the tissue were characterized and analyzed with a thermal imager and thermocouple probes. Results Under a power of 5 W combined with the electrode spacings of 1, 2, and 3 cm, the temperature in the tissue could not reach that required for fat dissolution. Under a power of 15 W combined with the electrode spacings of 1, 2, and 3 cm, the RF energy would thermally damage part of the skin areas. Besides this, the combination of a power of 10 W and the electrode spacing of 1 cm would thermally damage the skin areas. The combination of a power of 10 W and the electrode spacing of 2 or 3 cm made part of the fat layer of the tissue satisfy the requirements of fat dissolution, and the fat dissolution area caused by the former was 118% larger than that of the latter; in the meantime, no heat damage to the skin layer was found. Conclusion Different electrode spacings and power combinations significantly affect the electrical and thermal properties of bipolar RF energy loaded on biological tissue, a reasonable electrode spacing and power combination is one of the critical factors leading to the success of bipolar RF fat dissolution. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

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Dielectrical properties of living epidermis and dermis in the frequency range from 1 kHz to 1 MHz

Cited by 28 publications

References 40 publications

Analysis of the validity of the mathematical assumptions of electrical impedance tomography for human head tissues

Analysis of the validity of the mathematical assumptions of electrical impedance tomography for human head tissues

Portable Knee Health Monitoring System by Impedance Spectroscopy Based on Audio-Board

Effect of the Combination of Different Electrode Spacings and Power on Bipolar Radiofrequency Fat Dissolution: A Computational and Experimental Study

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