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Ollmar S, Fernandez Schrunder A, Birgersson U, Kristoffersson T, Rusu A, Thorsson E, Hedenqvist P, Manell E, Rydén A, Jensen-Waern M, Rodriguez S. A battery-less implantable glucose sensor based on electrical impedance spectroscopy. Sci Rep 2023; 13:18122. [PMID: 37872272 PMCID: PMC10593792 DOI: 10.1038/s41598-023-45154-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 10/17/2023] [Indexed: 10/25/2023] Open
Abstract
The ability to perform accurate continuous glucose monitoring without blood sampling has revolutionised the management of diabetes. Newer methods that can allow measurements during longer periods are necessary to substantially improve patients' quality of life. This paper presents an alternative method for glucose monitoring which is based on electrical impedance spectroscopy. A battery-less implantable bioimpedance spectroscope was designed, built, and used in an in vivo study on pigs. After a recovery period of 14 days post surgery, a total of 236 subcutaneous bioimpedance measurements obtained from intravenous glucose tolerance tests, with glucose concentration ranges between 77.4 and 523.8 mg/dL, were analyzed. The results show that glucose concentrations estimated by subcutaneous bioimpedance measurements correlate very well to the blood glucose reference values. The pigs were clinically healthy throughout the study, and the postmortem examinations revealed no signs of adverse effects related to the sensor. The implantation of the sensor requires minor surgery. The implant, being externally powered, could in principle last indefinitely. These encouraging results demonstrate the potential of the bioimpedance method to be used in future continuous glucose monitoring systems.
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Affiliation(s)
- Stig Ollmar
- Department of Clinical Science, Intervention and Technology, Karolinska Institute, Stockholm, Sweden
| | | | - Ulrik Birgersson
- Department of Clinical Science, Intervention and Technology, Karolinska Institute, Stockholm, Sweden
| | | | - Ana Rusu
- School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, 16440, Kista, Sweden
| | - Elina Thorsson
- Pathology Unit, Department of Biomedical Science and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Patricia Hedenqvist
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Elin Manell
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Anneli Rydén
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Marianne Jensen-Waern
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Saul Rodriguez
- School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, 16440, Kista, Sweden.
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2
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Ibrahim KA, Wicaksono R, Baidillah MR, Ito K, Takei M. Free and bound sodium identification by skin dielectric properties separation algorithm of bioelectrical impedance spectroscopy (spa-BIS) in human skin model. Biomed Phys Eng Express 2023; 9:055010. [PMID: 37459837 DOI: 10.1088/2057-1976/ace7d8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 07/17/2023] [Indexed: 07/28/2023]
Abstract
Free and bound sodium in human skin models have been identified by two proposals: skin's phantom fabrication and skin's dielectric properties separation algorithm of bioelectrical impedance spectroscopy (spa-BIS). Thespa-BIS consist of conductivity-permittivity separation, contact impedance compensation, and a correlation score algorithm based on the vessel with a bipolar electrode. The skin phantom fabrication comprises a recipe combination with temperature-controlled protocol and sodium molarity calculation. In experiments, the human skin models are created to mimic the electrical properties of skin under1MHzwith several different sodium molarities. Based on five types of human skin models with five samples of each group, the free sodium type conductivity and concentration resultsR2=0.9903-following a linear trendline of concentration change in skin tissues theorems with the fRequency range from1kHzto1MHz,while the bound sodium type resultsR2=0.9061-.Thespa-BIS compensate7-16Ωof vessel contact impedance. The dielectric properties of each type have been extracted with less than 10% of the average standard deviation, which is considered an accurate identification method of dermis dielectric properties. The algorithm successfully identifies sodium type: free sodium has a negative, and bound sodium has a positive correlation score trend. As an additional discussion, the different time-dependent effects, the different water content, and different agar content analyses have been provided in this study. As a robust analysis method, thespa-BIS has a prominent performance to replace a23Na-MRI in terms of free and bound sodium identification.
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Affiliation(s)
- Kiagus A Ibrahim
- Department of Mechanical Engineering, Graduate School of Science and Engineering, Chiba University, Chiba 2638522, Japan
| | - Ridwan Wicaksono
- Electrical and Information Engineering Department, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia
| | - Marlin R Baidillah
- Research Center for Electronics, National Research and Innovation Agency, KST Samaun Samadikun, Bandung 40135, Indonesia
| | - Koichi Ito
- Center for Frontier Medical Engineering, Chiba University, Chiba 2638522, Japan
| | - Masahiro Takei
- Department of Mechanical Engineering, Graduate School of Science and Engineering, Chiba University, Chiba 2638522, Japan
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Liu J, Atmaca Ö, Pott PP. Needle-Based Electrical Impedance Imaging Technology for Needle Navigation. Bioengineering (Basel) 2023; 10:bioengineering10050590. [PMID: 37237660 DOI: 10.3390/bioengineering10050590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 04/30/2023] [Accepted: 05/11/2023] [Indexed: 05/28/2023] Open
Abstract
Needle insertion is a common procedure in modern healthcare practices, such as blood sampling, tissue biopsy, and cancer treatment. Various guidance systems have been developed to reduce the risk of incorrect needle positioning. While ultrasound imaging is considered the gold standard, it has limitations such as a lack of spatial resolution and subjective interpretation of 2D images. As an alternative to conventional imaging techniques, we have developed a needle-based electrical impedance imaging system. The system involves the classification of different tissue types using impedance measurements taken with a modified needle and the visualization in a MATLAB Graphical User Interface (GUI) based on the spatial sensitivity distribution of the needle. The needle was equipped with 12 stainless steel wire electrodes, and the sensitive volumes were determined using Finite Element Method (FEM) simulation. A k-Nearest Neighbors (k-NN) algorithm was used to classify different types of tissue phantoms with an average success rate of 70.56% for individual tissue phantoms. The results showed that the classification of the fat tissue phantom was the most successful (60 out of 60 attempts correct), while the success rate decreased for layered tissue structures. The measurement can be controlled in the GUI, and the identified tissues around the needle are displayed in 3D. The average latency between measurement and visualization was 112.1 ms. This work demonstrates the feasibility of using needle-based electrical impedance imaging as an alternative to conventional imaging techniques. Further improvements to the hardware and the algorithm as well as usability testing are required to evaluate the effectiveness of the needle navigation system.
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Affiliation(s)
- Jan Liu
- Institute of Medical Device Technology, University of Stuttgart, 70569 Stuttgart, Germany
| | - Ömer Atmaca
- Institute of Medical Device Technology, University of Stuttgart, 70569 Stuttgart, Germany
- Institute of Applied Optics, University of Stuttgart, 70569 Stuttgart, Germany
| | - Peter Paul Pott
- Institute of Medical Device Technology, University of Stuttgart, 70569 Stuttgart, Germany
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Malyško-Ptašinskė V, Staigvila G, Novickij V. Invasive and non-invasive electrodes for successful drug and gene delivery in electroporation-based treatments. Front Bioeng Biotechnol 2023; 10:1094968. [PMID: 36727038 PMCID: PMC9885012 DOI: 10.3389/fbioe.2022.1094968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 12/28/2022] [Indexed: 01/17/2023] Open
Abstract
Electroporation is an effective physical method for irreversible or reversible permeabilization of plasma membranes of biological cells and is typically used for tissue ablation or targeted drug/DNA delivery into living cells. In the context of cancer treatment, full recovery from an electroporation-based procedure is frequently dependent on the spatial distribution/homogeneity of the electric field in the tissue; therefore, the structure of electrodes/applicators plays an important role. This review focuses on the analysis of electrodes and in silico models used for electroporation in cancer treatment and gene therapy. We have reviewed various invasive and non-invasive electrodes; analyzed the spatial electric field distribution using finite element method analysis; evaluated parametric compatibility, and the pros and cons of application; and summarized options for improvement. Additionally, this review highlights the importance of tissue bioimpedance for accurate treatment planning using numerical modeling and the effects of pulse frequency on tissue conductivity and relative permittivity values.
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Affiliation(s)
| | - Gediminas Staigvila
- Faculty of Electronics, Vilnius Gediminas Technical University, Vilnius, Lithuania
| | - Vitalij Novickij
- Faculty of Electronics, Vilnius Gediminas Technical University, Vilnius, Lithuania
- Department of Immunology, State Research Institute Centre of Innovative Medicine, Vilnius, Lithuania
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Ibrahim KA, Baidillah MR, Wicaksono R, Takei M. Skin layer classification by feedforward neural network in bioelectrical impedance spectroscopy. JOURNAL OF ELECTRICAL BIOIMPEDANCE 2023; 14:19-31. [PMID: 37564279 PMCID: PMC10411641 DOI: 10.2478/joeb-2023-0004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 08/05/2023] [Indexed: 08/12/2023]
Abstract
Conductivity change in skin layers has been classified by source indicator ok (k=1: Stratum corneum, k=2: Epidermis, k=3: Dermis, k=4: Fat, and k=5: Stratum corneum + Epidermis) trained from feedforward neural network (FNN) in bioelectrical impedance spectroscopy (BIS). In BIS studies, treating the skin as a bulk, limits the differentiation of conductivity changes in individual skin layers, however skin layer classification using FNN shows promise in accurately categorizing skin layers, which is essential for predicting source indicators ok and initiating skin dielectric characteristics diagnosis. The ok is trained by three main conceptual points which are (i) implementing FNN for predicting k in conductivity change, (ii) profiling four impedance inputs αξ consisting of magnitude input α|z|, phase angle input αθ, resistance input αR, and reactance input αx for filtering nonessential input, and (iii) selecting low and high frequency pair ( f r l h ) by distribution of relaxation time (DRT) for eliminating parasitic noise effect. The training data set of FNN is generated to obtain the αξ ∈ R10×17×10 by 10,200 cases by simulation under configuration and measurement parameters. The trained skin layer classification is validated through experiments with porcine skin under various sodium chloride (NaCl) solutions CNaCl = {15, 20, 25, 30, 35}[mM] in the dermis layer. FNN successfully classified conductivity change in the dermis layer from experiment with accuracy of 90.6% for the bipolar set-up at f 6 l h = 10 & 100 [ kHz] and with the same accuracy for the tetrapolar at f 8 l h = 35 & 100 [ kHz] . The measurement noise and systematic error in the experimental results are minimized by the proposed method using the feature extraction based on αξ at f r l h .
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Affiliation(s)
- Kiagus Aufa Ibrahim
- Department of Mechanical Engineering, Graduate School of Science and Engineering, Chiba University, Chiba, Japan
| | - Marlin Ramadhan Baidillah
- Research Center for Electronics, National Research and Innovation Agency, KST Samaun Samadikun, Bandung, Indonesia
| | - Ridwan Wicaksono
- Electrical and Information Engineering Department, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia
| | - Masahiro Takei
- Department of Mechanical Engineering, Graduate School of Science and Engineering, Chiba University, Chiba, Japan
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Anushree U, Shetty S, Kumar R, Bharati S. Adjunctive Diagnostic Methods for Skin Cancer Detection: A Review of Electrical Impedance-Based Techniques. Bioelectromagnetics 2022; 43:193-210. [PMID: 35181899 DOI: 10.1002/bem.22396] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 12/06/2021] [Accepted: 02/04/2022] [Indexed: 12/15/2022]
Abstract
Skin cancer is among the fastest-growing cancers with an excellent prognosis, if detected early. However, the current method of diagnosis by visual inspection has several disadvantages such as overlapping tumor characteristics, subjectivity, low sensitivity, and specificity. Hence, several adjunctive diagnostic techniques such as thermal imaging, optical imaging, ultrasonography, tape stripping methods, and electrical impedance imaging are employed along with visual inspection to improve the diagnosis. Electrical impedance-based skin cancer detection depends upon the variations in electrical impedance characteristics of the transformed cells. The information provided by this technique is fundamentally different from other adjunctive techniques and thus has good prospects. Depending on the stage, type, and location of skin cancer, various impedance-based devices have been developed. These devices when used as an adjunct to visual methods have increased the sensitivity and specificity of skin cancer detection up to 100% and 87%, respectively, thus demonstrating their potential to minimize unnecessary biopsies. In this review, the authors track the advancements and progress made in this technique for the detection of skin cancer, focusing mainly on the advantages and limitations in the clinical setting. © 2022 Bioelectromagnetics Society.
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Affiliation(s)
- U Anushree
- Department of Nuclear Medicine, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Sachin Shetty
- Department of Nuclear Medicine, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Rajesh Kumar
- Department of Nuclear Medicine, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India
| | - Sanjay Bharati
- Department of Nuclear Medicine, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, Karnataka, India
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Tronstad C, Amini M, Olesen E, Qvigstad E, Pabst O, Martinsen T, Abie SM, Martinsen ØG, Hisdal J, Jenssen TG, Kalvøy H. Diabetic Foot Assessment using Skin Impedance in a Custom Made Sensor-sock. JOURNAL OF ELECTRICAL BIOIMPEDANCE 2022; 13:136-142. [PMID: 36694878 PMCID: PMC9837869 DOI: 10.2478/joeb-2022-0019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Indexed: 06/17/2023]
Abstract
Diabetic peripheral neuropathy (DPN) may lead to several changes in the skin, and some of these may influence the skin impedance spectrum. In the present study we have developed a prototype solution for skin impedance spectroscopy at selected skin sites (big toe pulp, heel and toe ball) that was tested in a pilot study on five patients with DPN and five healthy controls. At the big toe, most of the controls had markedly lower impedance than the DPN group, especially in the range of 1-100 kHz. The separation between the groups seems to be weaker at the heel and weakest at the toeball. The results may indicate that monitoring of the skin impedance spectrum may be a method for detection of skin changes associated with DPN, encouraging further studies with the big toe sensor in particular.
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Affiliation(s)
- Christian Tronstad
- Department of Clinical and Biomedical Engineering, Oslo University Hospital, Oslo, Norway
| | - Maryam Amini
- Department of Clinical and Biomedical Engineering, Oslo University Hospital, Oslo, Norway
| | - Eline Olesen
- Department of Physics, University of Oslo, Oslo, Norway
| | - Elisabeth Qvigstad
- Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital, Oslo, Norway
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Oliver Pabst
- Department of Physics, University of Oslo, Oslo, Norway
| | - Tormod Martinsen
- Department of Clinical and Biomedical Engineering, Oslo University Hospital, Oslo, Norway
| | - Sisay M. Abie
- Faculty of Ecology and Natural Resource Management, Norwegian University of Life Sciences, Oslo Ås, Norway
| | - Ørjan G. Martinsen
- Department of Clinical and Biomedical Engineering, Oslo University Hospital, Oslo, Norway
- Department of Physics, University of Oslo, Oslo, Norway
| | - Jonny Hisdal
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Department of Vascular Surgery, Oslo University Hospital, Oslo, Norway
| | - Trond G. Jenssen
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Department of Transplantation Medicine, Oslo University Hospital, Oslo, Norway
| | - Håvard Kalvøy
- Department of Clinical and Biomedical Engineering, Oslo University Hospital, Oslo, Norway
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Wikslund LK, Amundsen VS, Kvernebo AK, Standal ØKV, Kvernebo K. Skin trauma rapidly induces thermoregulatory plexus hyperemia, while an increased nutritive papillary capillary function can be detected after 24 h. Microcirculation 2021; 29:e12735. [PMID: 34748662 DOI: 10.1111/micc.12735] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 10/30/2021] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Clinical assessments and laser Doppler perfusion measurements (LDPM) of skin microcirculation have limited value, as they fail to capture events regulated by local metabolic needs at a papillary capillary level. This study aimed to examine the ability of computer-assisted video microscopy (CAVM) and diffuse reflectance spectroscopy (DRS) to assess skin nutritive perfusion-compared to LDPM. METHODS Healthy volunteers (n = 10) were examined after (≈1 and ≈24 h) an incision (5 × 1 mm) on the forearm, at 0.1 mm (only with CAVM), 2-3 mm, and 30 mm from the trauma. RESULTS No changes were detected by CAVM after ≈1 h. After ≈24 h, 0-1 mm from the trauma, both CAVM parameters were increased: functional capillary density (capillary crossings/mm, 11.8 ± 1.4 vs. 7.3 ± 1.2, p < .01) and capillary flow velocities (CFV, %capillaries with brisk flow, 10 ± 6.8 vs. 1 ± 1, p < .01). At a distance of 2-3 mm, only CFV was increased (6.2 ± 6.1 vs. 1 ± 1, p < .05). DRS and LDPM measurements increased 2-3 mm from the trauma line in relation to baseline after both ≈1 and ≈24 h, that is, with DRS (%microvascular oxygen saturation): 45.8 ± 7.4% (baseline), 70.0 ± 12.5% (≈1 h), and 73.1 ± 10.4% (≈24 h), p < .01 and with LDPM (a.u.): 7.2 ± 2.5 (baseline), 28.3 ± 18.7 (≈1 h), and 45.9 ± 16.3 (≈24 h), p < .01. CONCLUSIONS ≈24 h after skin trauma, an increased function of the nutritive papillary capillaries can be detected by CAVM.
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Affiliation(s)
- Liv Kristin Wikslund
- Ostfold Hospital Trust, Sarpsborg, Norway
- The Circulation Laboratory, Department of Cardio-thoracic Surgery, Oslo University Hospital, Ullevaal, Oslo, Norway
- Institute of Clinical Medicine, Medical Faculty, University of Oslo, Oslo, Norway
| | - Vivian Shubira Amundsen
- The Circulation Laboratory, Department of Cardio-thoracic Surgery, Oslo University Hospital, Ullevaal, Oslo, Norway
- Institute of Clinical Medicine, Medical Faculty, University of Oslo, Oslo, Norway
| | - Anne Kari Kvernebo
- The Circulation Laboratory, Department of Cardio-thoracic Surgery, Oslo University Hospital, Ullevaal, Oslo, Norway
- Institute of Clinical Medicine, Medical Faculty, University of Oslo, Oslo, Norway
- Department of Ophthalmology, Oslo University Hospital HF, Oslo, Norway
| | | | - Knut Kvernebo
- The Circulation Laboratory, Department of Cardio-thoracic Surgery, Oslo University Hospital, Ullevaal, Oslo, Norway
- Institute of Clinical Medicine, Medical Faculty, University of Oslo, Oslo, Norway
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Enomoto Y, He S, Huang SY, Yu W. Effect of changes in Skin Thickness on pain-relief Transcutaneous Electrical Nerve Stimulation (TENS). ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:6504-6510. [PMID: 34892600 DOI: 10.1109/embc46164.2021.9630960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Transcutaneous Electrical Nerve Stimulation (TENS) suppresses chronic pain by stimulating deep nerves near the fascia from electrodes on the skin's surface. TENS has different effects on patients of different ages due to the variation of the thickness of skin layers when one becomes older.In this paper, we aim to optimize the stimulation effectiveness of TENS for patients of different ages through investigation of TENS stimulations of three different skin types categorized by age, Young, Old, and Older. In this investigation, the skin layer (stratum corneum, epidermis layer, dermis layer) in each model was created, and the thickness was varied. The effect of sin wave stimulation at 1 Hz, 100 Hz, and 10 kHz on the nerve stimulation effect near the fascia was examined.It is found that besides the well-known effect of stratum corneum, the thickness of the dermis layer significantly affects the stimulating effect. In addition, by using a lumped circuit model, it is showed that the change in the current path causes a mitigation in the stimulation effect in the dermis layer.
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Kruglikov IL. Assessment of Mechanical Stress Induced by Radiofrequency Currents on Skin Interfaces. BIOMED RESEARCH INTERNATIONAL 2021; 2021:6623757. [PMID: 34671678 PMCID: PMC8523224 DOI: 10.1155/2021/6623757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 09/08/2021] [Accepted: 09/15/2021] [Indexed: 11/18/2022]
Abstract
The epidermal-dermal (ED) and dermal-subcutaneous (DS) junctions are the most prominent skin interfaces, which are known to be of primary importance in different dermatological and aesthetic conditions. These interfaces are strongly modified in aging skin, and their effective targeting can lead to improvement of skin appearance in aging and by cellulite. Application of radiofrequency (RF) currents to the skin can selectively produce mechanical stress on these interfaces. Here, we assess the stresses induced by RF currents of different frequencies on EDJ and DSJ and discuss possible applications of the interfacial therapy in aesthetic medicine.
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Munawar MA, Schubert DW. Revealing Electrical and Mechanical Performances of Highly Oriented Electrospun Conductive Nanofibers of Biopolymers with Tunable Diameter. Int J Mol Sci 2021; 22:ijms221910295. [PMID: 34638631 PMCID: PMC8509057 DOI: 10.3390/ijms221910295] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/15/2021] [Accepted: 09/18/2021] [Indexed: 11/24/2022] Open
Abstract
The present study outlines a reliable approach to determining the electrical conductivity and elasticity of highly oriented electrospun conductive nanofibers of biopolymers. The highly oriented conductive fibers are fabricated by blending a high molar mass polyethylene oxide (PEO), polycaprolactone (PCL), and polylactic acid (PLA) with polyaniline (PANi) filler. The filler-matrix interaction and molar mass (M) of host polymer are among governing factors for variable fiber diameter. The conductivity as a function of filler fraction (φ) is shown and described using a McLachlan equation to reveal the electrical percolation thresholds (φc) of the nanofibers. The molar mass of biopolymer, storage time, and annealing temperature are significant factors for φc. The Young’s modulus (E) of conductive fibers is dependent on filler fraction, molar mass, and post-annealing process. The combination of high orientation, tunable diameter, tunable conductivity, tunable elasticity, and biodegradability makes the presented nanofibers superior to the fibers described in previous literature and highly desirable for various biomedical and technical applications.
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Affiliation(s)
- Muhammad A. Munawar
- Institute of Polymer Materials, Department of Material Science, Faculty of Engineering, Friedrich-Alexander-University Erlangen-Nuremberg, Martensstrasse 7, 91058 Erlangen, Germany
- KeyLab Advanced Fiber Technology, Bavarian Polymer Institute, Dr.-Mack-Strasse 77, 90762 Fürth, Germany
- Correspondence: (M.A.M.); (D.W.S.)
| | - Dirk W. Schubert
- Institute of Polymer Materials, Department of Material Science, Faculty of Engineering, Friedrich-Alexander-University Erlangen-Nuremberg, Martensstrasse 7, 91058 Erlangen, Germany
- KeyLab Advanced Fiber Technology, Bavarian Polymer Institute, Dr.-Mack-Strasse 77, 90762 Fürth, Germany
- Correspondence: (M.A.M.); (D.W.S.)
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12
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Lianru Z, Yu Z, Jia K, Yinmin X, ChengLi S. A Computational and Experimental Study to Compare the Effectiveness of Bipolar Mode With Phase-Shift Angle Mode in Radiofrequency Fat Dissolution on Subcutaneous Tissue. Lasers Surg Med 2021; 53:1395-1412. [PMID: 34036607 DOI: 10.1002/lsm.23420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 04/02/2021] [Accepted: 05/09/2021] [Indexed: 11/08/2022]
Abstract
BACKGROUND AND OBJECTIVES Radiofrequency (RF) energy exposure refers to a popular non-invasive method employed to generate heat in cutaneous and subcutaneous tissues. RF thermal stimulation of adipose tissue has been considered to cause adipocyte metabolism and enzymatic degradation of triglycerides into free fatty acids and glycerol. Bipolar mode (BM) has achieved extensive applications in clinical studies on RF fat dissolution, whereas BM has a less penetration depth than monopolar, result in a higher RF voltage that may be required to increase power to the deeper fat layer of the subcutaneous tissue, and improper power control may easily cause the skin layer to be thermally damaged. To tackle down the mentioned defect, a novel phase-shift angle mode (PM) was proposed in this study based on double-channel bipolar RF. By employing the finite element method (FEM) and performing the ex vivo experiment, the effectiveness of BM was compared with that of PM in RF fat dissolution on subcutaneous tissue. In addition, this study attempted to develop reasonable phase-shift angles capable of achieving fat dissolution effects, while the RF energy of which would not cause the skin layer to be thermally damaged. STUDY DESIGN/MATERIALS AND METHODS Two electrode spacings (1 and 2 cm) were applied in BM (BM-1 cm and BM-2 cm, respectively), and six phase-shift angles (i.e., 30°, 60°, 90°, 120°, 150°, and 180°) were set in PM (i.e., PM-30°, PM-60°, PM-90°, PM-120°, PM-150°, and PM-180°). In addition, COMSOL was adopted to conduct a finite element analysis for achieving thermoelectric coupling. Ex vivo experiments were performed with a self-developed double-channel bipolar RF device, through which up to two adjustable phase-shift angle sinusoidal voltages could be generated. Such a device was isolated with a transformer and then connected to four electrodes with a 5 mm diameter contacting the ex vivo porcine abdominal tissue. RESULTS Under the RF voltage amplitude of 30 V, and after 1800 seconds of RF heating, no thermally damaged area was formed in the tissue in BM-1 cm and BM-2 cm; in PM-30°, PM-60°, and PM-90°, thermally damaged areas were formed in the fat layer, while the skin layer was not located in the thermally damaged area. Moreover, the temperature in the thermally damaged area attributed to the mentioned three conditions may satisfy the requirement of fat dissolution temperature. CONCLUSIONS Under the identical RF voltage and heating time, PM is easier to cause the fat layer of the subcutaneous tissue to be thermally damaged as compared with BM. Accordingly, PM may be enabled to achieve the fat dissolution effect under a relatively low RF voltage as opposed to BM, thus avoiding the possibility of thermal damage of the skin layer attributed to the use of higher RF voltage. In PM, different phase-shift angle significantly affects the electrical and thermal properties of RF energy applied on subcutaneous tissue; the phase-shift angle of RF voltage is likely to be regulated for fat dissolution effect, while the RF energy of which will not cause the skin layer to be thermally damaged.© 2021 Wiley Periodicals LLC.
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Affiliation(s)
- Zang Lianru
- Shanghai Institute for Minimally Invasive Therapy, University of Shanghai for Science and Technology, 516 Jungong Road, 200082, Shanghai, China
| | - Zhou Yu
- Shanghai Institute for Minimally Invasive Therapy, University of Shanghai for Science and Technology, 516 Jungong Road, 200082, Shanghai, China
| | - Kang Jia
- Shanghai Institute for Minimally Invasive Therapy, University of Shanghai for Science and Technology, 516 Jungong Road, 200082, Shanghai, China
| | - Xue Yinmin
- Shanghai Institute for Minimally Invasive Therapy, University of Shanghai for Science and Technology, 516 Jungong Road, 200082, Shanghai, China
| | - Song ChengLi
- Shanghai Institute for Minimally Invasive Therapy, University of Shanghai for Science and Technology, 516 Jungong Road, 200082, Shanghai, China
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Williams T, Bouazza-Marouf K, Zecca M, Green A. Analysis of the validity of the mathematical assumptions of electrical impedance tomography for human head tissues. Biomed Phys Eng Express 2021; 7. [PMID: 33513587 DOI: 10.1088/2057-1976/abe190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 01/29/2021] [Indexed: 11/11/2022]
Abstract
Objective:To determine the validity of the key mathematical assumptions used in electrical impedance tomography for human head tissues over the frequency range of 10 Hz to 100 GHz.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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Affiliation(s)
- Toby Williams
- Wolfson School of Mechanical, Electrical, and Manufacturing Engineering, Loughborough University, Loughborough University, Wolfson Building, Ashby Road, Loughborough, Leicestershire, LE11 3TU, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
| | - Kaddour Bouazza-Marouf
- Wolfson School of Mechanical, Electrical, and Manufacturing Engineering, Loughborough University, Loughborough universtiy, Wolfson Building, Ashby Road, Loughborough, Leicestershire, LE11 3TU, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
| | - Massimiliano Zecca
- Wolfson School of Mechanical, Electrical, and Manufacturing Engineering, Loughborough University, Michael Pearson (East), 1 Oakwood Drive, Loughborough University Science and Enterprise Park, Loughborough, Leicestershire, LE11 3QF, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
| | - Alex Green
- Nuffield Department of Surgical Sciences, University of Oxford, University of Oxford, Oxford, Oxfordshire, OX3 9DU, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
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Colella M, Paffi A, De Santis V, Apollonio F, Liberti M. Effect of skin conductivity on the electric field induced by transcranial stimulation techniques in different head models. Phys Med Biol 2021; 66:035010. [PMID: 33496268 DOI: 10.1088/1361-6560/abcde7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This study aims at quantifying the effect that using different skin conductivity values has on the estimation of the electric (E)-field distribution induced by transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) in the brain of two anatomical models. The induced E-field was calculated with numerical simulations inside MIDA and Duke models, assigning to the skin a conductivity value estimated from a multi-layered skin model and three values taken from literature. The effect of skin conductivity variations on the local E-field induced by tDCS in the brain was up to 70%. In TMS, minor local differences, in the order of 20%, were obtained in regions of interest for the onset of possible side effects. Results suggested that an accurate model of the skin is necessary in all numerical studies that aim at precisely estimating the E-field induced during TMS and tDCS applications. This also highlights the importance of further experimental studies on human skin characterization, especially at low frequencies.
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Affiliation(s)
- Micol Colella
- Department of Information Engineering, Electronics and Telecommunications (DIET), University of Rome 'La Sapienza', Rome, Italy
| | - Alessandra Paffi
- Department of Information Engineering, Electronics and Telecommunications (DIET), University of Rome 'La Sapienza', Rome, Italy
| | - Valerio De Santis
- Department of Industrial and Information Engineering and Economics (DIIEE), University of L'Aquila, L'Aquila, Italy
| | - Francesca Apollonio
- Department of Information Engineering, Electronics and Telecommunications (DIET), University of Rome 'La Sapienza', Rome, Italy
| | - Micaela Liberti
- Department of Information Engineering, Electronics and Telecommunications (DIET), University of Rome 'La Sapienza', Rome, Italy
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Roopnarine A, Rocke SA. Stochastic Bioimpedance-Based Channel Model of The Human Body for Galvanic Coupling. JOURNAL OF ELECTRICAL BIOIMPEDANCE 2021; 12:117-124. [PMID: 35069947 PMCID: PMC8713383 DOI: 10.2478/joeb-2021-0014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Indexed: 06/14/2023]
Abstract
Human body communication (HBC) uses the human body as the channel to transfer data. Extensive work has been done to characterize the human body channel for different HBC techniques and scenarios. However, statistical channel bioimpedance characterisation of human body channels, particularly under dynamic conditions, remains relatively understudied. This paper develops a stochastic fading bioimpedance model for the human body channel using Monte Carlo simulations. Differential body segments were modelled as 2-port networks using ABCD parameters which are functions of bioimpedance based body parameters modelled as random variables. The channel was then modelled as the cascade of these random 2-port networks for different combinations of probability distribution functions (PDFs) assumed for the bioimpedance-based body parameters. The resultant distribution of the cascaded body segments varied for the different assumed bioimpedance based body parameter distributions and differential body segment sizes. However, considering the distribution names that demonstrated a best fit (in the top 3 PDF rankings) with highest frequency under the varying conditions, this paper recommends the distribution names: Generalized Pareto for phase distributions and Log-normal for magnitude distributions for each element in the overall cascaded random variable ABCD matrix.
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Affiliation(s)
- Aaron Roopnarine
- Department of Electrical & Computer Engineering, The University of the West Indies, St. Augustine, Trinidad & Tobago
| | - Sean A. Rocke
- Department of Electrical & Computer Engineering, The University of the West Indies, St. Augustine, Trinidad & Tobago
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Zang L, Zhou Y, Kang J, Song C. Effect of the Combination of Different Electrode Spacings and Power on Bipolar Radiofrequency Fat Dissolution: A Computational and Experimental Study. Lasers Surg Med 2020; 52:1020-1031. [DOI: 10.1002/lsm.23256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 03/15/2020] [Accepted: 04/16/2020] [Indexed: 11/10/2022]
Affiliation(s)
- Lianru Zang
- Shanghai Institute for Minimally Invasive Therapy University of Shanghai for Science and Technology 516 Jungong Road 200082 Shanghai China
| | - Yu Zhou
- Shanghai Institute for Minimally Invasive Therapy University of Shanghai for Science and Technology 516 Jungong Road 200082 Shanghai China
| | - Jia Kang
- Shanghai Institute for Minimally Invasive Therapy University of Shanghai for Science and Technology 516 Jungong Road 200082 Shanghai China
| | - ChengLi Song
- Shanghai Institute for Minimally Invasive Therapy University of Shanghai for Science and Technology 516 Jungong Road 200082 Shanghai China
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