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Kumar M, Mishra A. A microdosimetry analysis of reversible electroporation in scattered, overlapping, and cancerous cervical cells. Biomed Phys Eng Express 2024; 10:035022. [PMID: 38479001 DOI: 10.1088/2057-1976/ad33a9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 03/13/2024] [Indexed: 04/06/2024]
Abstract
We present a numerical method for studying reversible electroporation on normal and cancerous cervical cells. This microdosimetry analysis builds on a unique approach for extracting contours of free and overlapping cervical cells in the cluster from the Extended Depth of Field (EDF) images. The algorithm used for extracting the contours is a joint optimization of multiple-level set function along with the Gaussian mixture model and Maximally Stable Extremal Regions. These contours are then exported to a multi-physics domain solver, where a variable frequency pulsed electric field is applied. The trans-Membrane voltage (TMV) developed across the cell membrane is computed using the Maxwell equation coupled with a statistical approach, employing the asymptotic Smoluchowski equation. The numerical model was validated by successful replication of existing experimental configurations that employed low-frequency uni-polar pulses on the overlapping cells to obtain reversible electroporation, wherein, several overlapping clumps of cervical cells were targeted. For high-frequency calculation, a combination of normal and cancerous cells is introduced to the computational domain. The cells are assumed to be dispersive and the Debye dispersion equation is used for further calculations. We also present the resulting strength-duration relationship for achieving the threshold value of electroporation between the normal and cancerous cervical cells due to their size and conductivity differences. The dye uptake modulation during the high-frequency electric field electroporation is further advocated by a mathematical model.
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Affiliation(s)
- Mayank Kumar
- Department of Applied Science, Indian Institute of Information Technology Allahabad, India
| | - Ashutosh Mishra
- Department of Applied Science, Indian Institute of Information Technology Allahabad, India
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Kumar M, Kumar S, Chakrabartty S, Poulose A, Mostafa H, Goyal B. Dispersive Modeling of Normal and Cancerous Cervical Cell Responses to Nanosecond Electric Fields in Reversible Electroporation Using a Drift-Step Rectifier Diode Generator. MICROMACHINES 2023; 14:2136. [PMID: 38138305 PMCID: PMC10745406 DOI: 10.3390/mi14122136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 11/16/2023] [Accepted: 11/18/2023] [Indexed: 12/24/2023]
Abstract
This paper creates an approximate three-dimensional model for normal and cancerous cervical cells using image processing and computer-aided design (CAD) tools. The model is then exposed to low-frequency electric pulses to verify the work with experimental data. The transmembrane potential, pore density, and pore radius evolution are analyzed. This work adds a study of the electrodeformation of cells under an electric field to investigate cytoskeleton integrity. The Maxwell stress tensor is calculated for the dispersive bi-lipid layer plasma membrane. The solid displacement is calculated under electric stress to observe cytoskeleton integrity. After verifying the results with previous experiments, the cells are exposed to a nanosecond pulsed electric field. The nanosecond pulse is applied using a drift-step rectifier diode (DSRD)-based generator circuit. The cells' transmembrane voltage (TMV), pore density, pore radius evolution, displacement of the membrane under electric stress, and strain energy are calculated. A thermal analysis of the cells under a nanosecond pulse is also carried out to prove that it constitutes a non-thermal process. The results showed differences in normal and cancerous cell responses to electric pulses due to changes in morphology and differences in the cells' electrical and mechanical properties. This work is a model-driven microdosimetry method that could be used for diagnostic and therapeutic purposes.
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Affiliation(s)
- Mayank Kumar
- Technical Research Analyst (TRA), Electronics/Biomedical Engineering, Aranca, Mumbai 400076, Maharastra, India;
| | - Sachin Kumar
- Department of Electronics and Communication Engineering, Galgotias College of Engineering and Technology, Greater Noida 201310, Uttar Pradesh, India;
| | - Shubhro Chakrabartty
- School of Computer Science Engineering and Applications, D Y Patil International University, Pune 411044, Maharastra, India
| | - Alwin Poulose
- School of Data Science, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Vithura, Thiruvananthapuram 695551, Kerala, India
| | - Hala Mostafa
- Department of Information Technology, College of Computer and Information Sciences, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia;
| | - Bhawna Goyal
- University Centre for Research and Development, Chandigarh University, Gharuan, Mohali 140413, Punjab, India;
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Heath JP, Hunter KD, Murdoch C, Walker DC. Computational Modelling for Electrical Impedance Spectroscopy-Based Diagnosis of Oral Potential Malignant Disorders (OPMD). SENSORS (BASEL, SWITZERLAND) 2022; 22:5913. [PMID: 35957472 PMCID: PMC9371412 DOI: 10.3390/s22155913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 08/02/2022] [Accepted: 08/03/2022] [Indexed: 06/15/2023]
Abstract
A multiscale modelling approach has been applied to the simulation of the electrical properties of oral tissue, for the purpose of informing an electrical impedance-based method of oral potential malignant disorder (OPMD) diagnosis. Finite element models of individual cell types, with geometry informed by histological analysis of human oral tissue (normal, hyperplastic and dysplastic), were generated and simulated to obtain electrical parameters. These were then used in a histology-informed tissue scale model, including the electrode geometry of the ZedScan tetrapolar impedance-measurement device. The simulations offer insight into the feasibility of distinguishing moderate dysplasia from severe dysplasia or healthy tissue. For some oral sites, simulated spectra agreed with real measurements previously collected using ZedScan. However, similarities between simulated spectra for dysplastic, keratinised and non-dysplastic but hyperkeratinised tissue suggest that significant keratinisation could cause some OPMD tissues to exhibit larger than expected impedance values. This could lead to misidentification of OPMD spectra as healthy. Sources of uncertainty within the models were identified and potential remedies proposed.
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Affiliation(s)
- James P. Heath
- Department of Computer Science, University of Sheffield, Sheffield S1 4DP, UK
| | - Keith D. Hunter
- Liverpool Head and Neck Centre, Molecular and Clinical Cancer Medicine, University of Liverpool, Liverpool L69 7TX, UK
| | - Craig Murdoch
- School of Clinical Dentistry, University of Sheffield, Sheffield S10 2TA, UK
| | - Dawn C. Walker
- Department of Computer Science, University of Sheffield, Sheffield S1 4DP, UK
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Kumar M, Mishra A. Reversible electroporation study of realistic normal and cancerous cervical cells model using avalanche transistor-based nano pulse generator. Biomed Phys Eng Express 2021; 7. [PMID: 34488195 DOI: 10.1088/2057-1976/ac240b] [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: 06/18/2021] [Accepted: 09/06/2021] [Indexed: 11/12/2022]
Abstract
In this paper, we study the reversible electroporation process on normal and cancerous cervical cells. The 2D contour of the cervical cells is extracted using image processing techniques from the Pap smear images. The conductivity change in the cancer cell model has been used to differentiate the effects of the high-frequency electric field on normal and cancerous cells. The cells' dielectric constant modulates when this high-frequency pulse is applied based on the Debye relaxation. To computationally visualize the effects of the electroporation on the cell membrane, the Smoluchowski equation is employed to estimate pore density, and Maxwell equations are used to determine the electric potential developed across the membrane of the cervical cell. The results demonstrate the suitability of this mathematical model for studying the response of normal and cancerous cells under electric stress. The electric field is supplied with the help of a realistic pulse generator which is designed on the principle of Marx circuit and avalanche transistor-based operations to produce a Gaussian pulse. The paper here uses a strength-duration curve to differentiate the electric field and time in nanoseconds required to electroporate normal and cancerous cells.
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Affiliation(s)
- Mayank Kumar
- Indian Institute of Information Technology Allahabad, Department of Applied Sciences (Biomedical Engineering), India
| | - Ashutosh Mishra
- Indian Institute of Information Technology Allahabad, Department of Applied Sciences (Biomedical Engineering), India
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Anumba DOC, Stern V, Healey JT, Dixon S, Brown BH. Value of cervical electrical impedance spectroscopy to predict spontaneous preterm delivery in asymptomatic women: the ECCLIPPx prospective cohort study. ULTRASOUND IN OBSTETRICS & GYNECOLOGY : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF ULTRASOUND IN OBSTETRICS AND GYNECOLOGY 2021; 58:293-302. [PMID: 32798253 DOI: 10.1002/uog.22180] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 07/30/2020] [Accepted: 08/03/2020] [Indexed: 06/11/2023]
Abstract
OBJECTIVES Preterm birth (PTB) accounts for two-thirds of deaths of structurally normal babies and is associated with substantial lifetime healthcare costs. Prevention of PTB remains limited by the modest accuracy of prediction methods, namely transvaginal ultrasound (TVS) cervical length (CL) measurement and quantitative cervicovaginal fetal fibronectin (FFN) estimation. We report the first substantive study detailing the predictive performance of a cervical probe device based on electrical impedance spectroscopy (EIS) for PTB - the EleCtriCaL Impedance Prediction of Preterm birth by spectroscopy of the cervix (ECCLIPPx) study. We aimed to compare the accuracy of cervical EIS-based prediction of spontaneous PTB with that of prediction using TVS-CL and FFN in asymptomatic women in the mid-trimester. METHODS We studied asymptomatic women with a singleton pregnancy at 20-22 weeks' and 26-28 weeks' gestation. EIS was performed using a Sheffield Mark 5.0 device that makes measurements in the frequency range 76 Hz to 625 kHz using a small probe housing tetrapolar electrodes. TVS-CL and FFN were also measured. The associations of cervical EIS, TVS-CL and FFN with spontaneous delivery before 37 weeks and before 32 weeks were determined by multivariate linear and non-linear logistic regression analysis. Areas under the receiver-operating-characteristics curves (AUC) plots of sensitivity against specificity were used to compare the predictive performance of all parameters, both in isolation and in combination. RESULTS Of the 365 asymptomatic women studied at 20-22 weeks who were not receiving treatment, 29 had spontaneous PTB, 14 had indicated PTB and 322 had term birth. At the higher frequencies assessed, cervical EIS predicted spontaneous PTB before 37 weeks with an AUC of 0.76 (95% CI, 0.71-0.81), compared with AUCs of 0.72 (95% CI, 0.66-0.76) for TVS-CL and 0.62 (95% CI, 0.56-0.72) for FFN. Combining all three assessments improved the prediction of spontaneous PTB before 37 weeks (AUC, 0.79 (95% CI, 0.74-0.83)) compared with TVS-CL and FFN alone. Incorporating a history of spontaneous PTB (defined as previous mid-trimester miscarriage or spontaneous PTB (14 to < 37 weeks)) into the cervical EIS prediction model improved the accuracy of prediction of spontaneous PTB before 37 weeks (AUC, 0.83 (95% CI, 0.78-0.87)) and before 32 weeks (AUC, 0.86 (95% CI, 0.82-0.90)). CONCLUSIONS Mid-trimester cervical EIS assessment predicts spontaneous PTB. Larger confirmatory studies investigating its potential clinical utility and to inform effective preventive interventions are required. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.
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Affiliation(s)
- D O C Anumba
- Academic Unit of Reproductive and Developmental Medicine, Department of Oncology and Metabolism, University of Sheffield, Sheffield, UK
| | - V Stern
- Academic Unit of Reproductive and Developmental Medicine, Department of Oncology and Metabolism, University of Sheffield, Sheffield, UK
| | - J T Healey
- Medical Physics and Clinical Engineering, University of Sheffield, Sheffield, UK
| | - S Dixon
- School of Health and Related Research (ScHARR), University of Sheffield, Sheffield, UK
| | - B H Brown
- Medical Physics and Clinical Engineering, University of Sheffield, Sheffield, UK
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Sabuncu AC, Shen J, Zaki MH, Beskok A. Changes in the dielectric spectra of murine colon during neoplastic progression. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aaad81] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Sanchez B, Pacheck A, Rutkove SB. Guidelines to electrode positioning for human and animal electrical impedance myography research. Sci Rep 2016; 6:32615. [PMID: 27585740 PMCID: PMC5009322 DOI: 10.1038/srep32615] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 08/10/2016] [Indexed: 12/14/2022] Open
Abstract
The positioning of electrodes in electrical impedance myography (EIM) is critical for accurately assessing disease progression and effectiveness of treatment. In human and animal trials for neuromuscular disorders, inconsistent electrode positioning adds errors to the muscle impedance. Despite its importance, how the reproducibility of resistance and reactance, the two parameters that define EIM, are affected by changes in electrode positioning remains unknown. In this paper, we present a novel approach founded on biophysical principles to study the reproducibility of resistance and reactance to electrode misplacements. The analytical framework presented allows the user to quantify a priori the effect on the muscle resistance and reactance using only one parameter: the uncertainty placing the electrodes. We also provide quantitative data on the precision needed to position the electrodes and the minimum muscle length needed to achieve a pre-specified EIM reproducibility. The results reported here are confirmed with finite element model simulations and measurements on five healthy subjects. Ultimately, our data can serve as normative values to enhance the reliability of EIM as a biomarker and facilitate comparability of future human and animal studies.
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Affiliation(s)
- Benjamin Sanchez
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA
| | - Adam Pacheck
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA
| | - Seward B Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215-5491, USA
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keshtkar A, Madaen SK. The comparison of measured impedance of the bladder tissue with the computational modeling results. JOURNAL OF ANALYTICAL RESEARCH IN CLINICAL MEDICINE 2015. [DOI: 10.15171/jarcm.2015.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Novel advancements in colposcopy: historical perspectives and a systematic review of future developments. J Low Genit Tract Dis 2015; 18:246-60. [PMID: 24633164 DOI: 10.1097/lgt.0b013e3182a72170] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE To describe novel innovations and techniques for the detection of high-grade dysplasia. MATERIALS AND METHODS Studies were identified through the PubMed database, spanning the last 10 years. The key words (["computerized colposcopy" or "digital colposcopy" or "spectroscopy" or "multispectral digital colposcopy" or "dynamic spectral imaging", or "electrical impedance spectroscopy" or "confocal endomicroscopy" or "confocal microscopy"or "optical coherence tomography"] and ["cervical dysplasia" or cervical precancer" or "cervix" or "cervical"]) were used. The inclusion criteria were published articles of original research referring to noncolposcopic evaluation of the cervix for the detection of cervical dysplasia. Only English-language articles from the past 10 years were included, in which the technologies were used in vivo, and sensitivities and specificities could be calculated. RESULTS The single author reviewed the articles for inclusion. Primary search of the database yielded 59 articles, and secondary cross-reference yielded 12 articles. Thirty-two articles met the inclusion criteria. CONCLUSIONS An instrument that globally assesses the cervix, such as computer-assisted colposcopy, optical spectroscopy, and dynamic spectral imaging, would provided the most comprehensive estimate of disease and is therefore best suited when treatment is preferred. Electrical impedance spectroscopy, confocal microscopy, and optical coherence tomography provide information at the cellular level to estimate histology and are therefore best suited when deferment of treatment is preferred. If a device is to eventually replace the colposcope, it will likely combine technologies to best meet the needs of the target population, and as such, no single instrument may prove to be universally appropriate. Analyses of false-positive rates, additional colposcopies and biopsies, cost, and absolute life-savings will be important when considering these technologies and are limited thus far.
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Birgersson U, Birgersson E, Nicander I, Ollmar S. A methodology for extracting the electrical properties of human skin. Physiol Meas 2013; 34:723-36. [DOI: 10.1088/0967-3334/34/6/723] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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11
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Daoud J, Asami K, Rosenberg L, Tabrizian M. Dielectric spectroscopy for non-invasive monitoring of epithelial cell differentiation within three-dimensional scaffolds. Phys Med Biol 2012; 57:5097-112. [DOI: 10.1088/0031-9155/57/16/5097] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Birgersson U, Birgersson E, Åberg P, Nicander I, Ollmar S. Non-invasive bioimpedance of intact skin: mathematical modeling and experiments. Physiol Meas 2010; 32:1-18. [DOI: 10.1088/0967-3334/32/1/001] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Hartinger A, Guardo R, Kokta V, Gagnon H. A 3-D Hybrid Finite Element Model to Characterize the Electrical Behavior of Cutaneous Tissues. IEEE Trans Biomed Eng 2010; 57:780-9. [DOI: 10.1109/tbme.2009.2036371] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Balasubramani L, Brown BH, Healey J, Tidy JA. The detection of cervical intraepithelial neoplasia by electrical impedance spectroscopy: The effects of acetic acid and tissue homogeneity. Gynecol Oncol 2009; 115:267-71. [DOI: 10.1016/j.ygyno.2009.08.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 07/31/2009] [Accepted: 08/08/2009] [Indexed: 11/26/2022]
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Jokhi RP, Brown BH, Anumba DOC. The role of cervical Electrical Impedance Spectroscopy in the prediction of the course and outcome of induced labour. BMC Pregnancy Childbirth 2009; 9:40. [PMID: 19725953 PMCID: PMC3224746 DOI: 10.1186/1471-2393-9-40] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Accepted: 09/02/2009] [Indexed: 12/03/2022] Open
Abstract
Background Previous work by us and others had suggested that cervical electrical impedance spectroscopy (EIS) may be predictive of the outcome of induced labour. We sought to determine which probe configuration of the EIS device is predictive of the outcome of induced labour and compare this to digital assessment by the Bishop score. Methods In a prospective cohort of 205 women admitted for induction of labour, we used four probes of diameter 3, 6, 9 and 12 mm connected to an impedance meter to measure cervical resistivity (CR) in Ohm.meters at 14 electrical frequencies and compared their values to digital assessment of the cervix by the Bishop score for the prediction of the outcome of induced labour. We tested the association of labour characteristics and outcomes with CR and Bishop score by stepwise multilinear regression analyses, and the accuracy of prediction of categorical clinical outcomes by analysis of the area under the curves (AUC) of derived Receiver Operator Characteristic (ROC) curves. Results Of the four CR probe dimensions studied, only the 12 mm probe was predictive of any labour indices. In the frequency range 19 - 156 kHz, CR obtained with this probe was higher in women who delivered by caesarean section (CS) than those who delivered vaginally, and in labours lasting > 24 hrs. Cervical resistivity at 78.1 kHz best predicted vaginal delivery [optimal cut-off <2.25 Ohm.meter, AUC 0.66 (95% CI 0.59-0.72), sensitivity 71.0%, specificity 56.5%, LR+ 1.63, LR- 0.51, P < 0.01] and labour duration >24 hrs [optimal cut-off 2.27 Ω.m, AUC 0.65 (95% CI 0.58, 0.72), sensitivity 71%, specificity 59%, LR+ 1.72, LR- 0.50, P < 0.05]. In contrast digital assessment by the Bishop score neither predicted vaginal delivery nor the duration of labour. However, Bishop score predicted time to onset of labour > 12 hours and induction-delivery interval < 24 hrs [optimal cut-off ≤ 4, AUC 0.8 (95% CI 0.75, 0.86), sensitivity 77%, specificity 76%, LR+ 3.3, LR- 0.3, P < 0.05] whilst CR did not. Conclusion Cervical resistivity appears predictive of labour duration and delivery mode following induced labour. However the low predictive values obtained suggest that its current design proffers no immediate clinical utility.
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Affiliation(s)
- Roobin P Jokhi
- University of Sheffield, Sheffield Teaching Hospitals NHS Trust, Sheffield, UK.
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Jokhi RP, Ghule VV, Brown BH, Anumba DOC. Reproducibility and repeatability of measuring the electrical impedance of the pregnant human cervix-the effect of probe size and applied pressure. Biomed Eng Online 2009; 8:10. [PMID: 19534806 PMCID: PMC2704213 DOI: 10.1186/1475-925x-8-10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2009] [Accepted: 06/17/2009] [Indexed: 12/20/2022] Open
Abstract
Background The utility of cervical electrical impedance spectroscopy (EIS) as a diagnostic tool is being investigated in clinical trials. We sought to assess the reliability of two different sizes of tetrapolar probes used in measuring cervical impedance. Methods Cervical transfer impedance was measured at 14 frequencies between 76 and 625 000 Hz from 11 pregnant subjects at term. Repeated measurements were taken with two probes (3 mm and 12 mm diameter) applied softly (approximately 0.7 Newton of force), and firmly (approximately 2.2 Newton) to the surface of the cervix by two observers. The intra-class correlation coefficient (ICC), coefficient of variation (CV) and repeatability standard deviations (SD) were derived from these measurements and compared. Results Measurements taken by one observer were highly repeatable for both probes as demonstrated by high ICC and low CV values. Probe performance was improved further by firm application. Firm application of the 3 mm probe resulted in ICC values that ranged from 0.936 to 0.986 (p = 0.0001) and CV values between 1.0 and 3.4%. Firm pressure with the 12 mm probe resulted in ICC values that ranged between 0.914 and 0.988 (p = 0.0001) with CV values between 0.7 and 2.1%. In addition, the repeatability SD was low across all frequencies implying that there was low intra-observer variability. Measurements taken by 2 observers with firm application of the 12 mm probe demonstrated moderate reproducibility between 9.8 and 156 kHz, the frequency range in which previous clinical studies have shown predictive association between high cervical resistivity and vaginal delivery: ICC values ranged between 0.528 and 0.638 (p < 0.05), CV values were between 3.3 and 5.2% and reproducibility SD values were also low. In contrast the 3 mm probe demonstrated poor reproducibility at all study frequencies. Conclusion Measuring cervical resistivity by a single observer with both the 3 and 12 mm probes is highly repeatable whilst inter-observer reproducibility is poor with the 3 mm probe but moderately good when the 12 mm probe is firmly applied to the cervix in the frequency range 9.8 to 156 kHz, consistent with our observations of probe performance in clinical trials.
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Affiliation(s)
- Roobin P Jokhi
- Academic Unit of Reproductive and Developmental Medicine, University of Sheffield and Sheffield Teaching Hospitals NHS Trust, Sheffield, UK.
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Keshtkar A, Keshtkar A. Modeled Current Distribution Inside the Normal and Malignant Human Urothelium Using Finite Element Analysis. IEEE Trans Biomed Eng 2008; 55:733-8. [DOI: 10.1109/tbme.2007.905398] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Gandhi SV, Walker D, Milnes P, Mukherjee S, Brown BH, Anumba DOC. Electrical impedance spectroscopy of the cervix in non-pregnant and pregnant women. Eur J Obstet Gynecol Reprod Biol 2006; 129:145-9. [PMID: 16517044 DOI: 10.1016/j.ejogrb.2005.12.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2005] [Revised: 11/09/2005] [Accepted: 12/12/2005] [Indexed: 11/22/2022]
Abstract
OBJECTIVES We sought to validate and measure the electrical impedance of the uterine cervix in non-pregnant and pregnant women by spectroscopy. STUDY DESIGN Cervical stromal impedance (CSI) was measured in 50 non-pregnant, 20 1st, 20 2nd and 50 3rd trimester pregnant women. The technique was also validated by comparing in vivo data to a finite element (FE) model of cervical tissue. RESULTS CSI agreed well with the FE model and was highly reproducible in all study groups. Mean (S.E.) CSI at 4-819 kHz was higher in pregnant (2.78 +/- 0.09 Omega m) compared to non-pregnant (2.38 +/- 0.07, p < 0.01) women, and in the 3rd trimester (3.08 +/- 0.13) compared to non-pregnant (p < 0.01), 1st trimester (2.42 +/- 0.12, p < 0.001) and 2nd trimester (2.20 +/- 0.05, p < 0.001) pregnant women. CONCLUSION Measurement of CSI provides a non-invasive method of assessing cervical tissue characteristics. Cervical extracellular matrix synthesis and leukocyte infiltration may account for the increased tissue impedance noted in the 3rd trimester.
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Affiliation(s)
- Saurabh V Gandhi
- Academic Unit of Reproductive and Developmental Medicine, University of Sheffield, Sheffield Teaching Hospitals NHS Trust, Sheffield, United Kingdom
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Comparison of human uterine cervical electrical impedance measurements derived using two tetrapolar probes of different sizes. Biomed Eng Online 2006; 5:62. [PMID: 17125510 PMCID: PMC1684260 DOI: 10.1186/1475-925x-5-62] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Accepted: 11/24/2006] [Indexed: 11/10/2022] Open
Abstract
Background We sought to compare uterine cervical electrical impedance spectroscopy measurements employing two probes of different sizes, and to employ a finite element model to predict and compare the fraction of electrical current derived from subepithelial stromal tissue. Methods Cervical impedance was measured in 12 subjects during early pregnancy using 2 different sizes of the probes on each subject. Results Mean cervical resistivity was significantly higher (5.4 vs. 2.8 Ωm; p < 0.001) with the smaller probe in the frequency rage of 4–819 kHz. There was no difference in the short-term intra-observer variability between the two probes. The cervical impedance measurements derived in vivo followed the pattern predicted by the finite element model. Conclusion Inter-electrode distance on the probes for measuring cervical impedance influences the tissue resistivity values obtained. Determining the appropriate probe size is necessary when conducting clinical studies of resistivity of the cervix and other human tissues.
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Tagg R, Asadi-Zeydabadi M, Meyers AD. Biophotonic and Other Physical Methods for Characterizing Oral Mucosa. Otolaryngol Clin North Am 2005; 38:215-40, vi. [PMID: 15823590 DOI: 10.1016/j.otc.2004.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This article discusses biophotonic and other physical methods for characterizing oral mucosa.
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González-Correa CA, Brown BH, Smallwood RH, Walker DC, Bardhan KD. Electrical bioimpedance readings increase with higher pressure applied to the measuring probe. Physiol Meas 2005; 26:S39-47. [PMID: 15798245 DOI: 10.1088/0967-3334/26/2/004] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Electrical bioimpedance spectroscopy (EBIS) is a technique that uses a probe to calculate the transfer impedance from tissues. This transfer impedance can give information about the normal or pathological condition of the tissue. To take readings, pressure has to be applied to the probe in order to get a good contact between the electrodes and the tissue. We have been using EBIS to investigate the early diagnosis of dysplasia and cancer in the human cervix, oesophagus and bladder. We have found that, with increasing pressure (range used here was approximately 1 kPa to approximately 50 kPa), the resistivity readings increase in a consistent way up to 80%. In this paper, we show how this is a case in three different tissue types (oesophageal, gastric and vesical samples). These increases can be higher than those associated with the pathological changes that we are investigating (non-inflamed columnar tissue, for instance, shows values 50% higher than dysplastic columnar tissue). Finite-element modelling was also used to investigate the effect of volume reduction in the connective tissue or stroma. This simulation suggests no strong correlation between reduction of this structure and increase in resistivity. We hypothesize therefore that these changes may be mainly associated with the squeezing of water from the extracellular space. Finally, as pressure is difficult to control by hand, we raise the issue of the necessity of considering this variable when making EIS measurements.
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Affiliation(s)
- C A González-Correa
- Department of Medical Physics and Clinical Engineering, Royal Hallamshire Hospital, Glossop Road, S10 2JF, Sheffield, UK.
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Walker DC, Smallwood RH, Keshtar A, Wilkinson BA, Hamdy FC, Lee JA. Modelling the electrical properties of bladder tissue—quantifying impedance changes due to inflammation and oedema. Physiol Meas 2005; 26:251-68. [PMID: 15798300 DOI: 10.1088/0967-3334/26/3/010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Electrical impedance spectroscopy has been developed as a potential method for the diagnosis of carcinoma in epithelial tissues. An understanding of the influence of structural changes in the tissue on the properties measured using this technique is essential for interpreting measured data and optimization of probe design. In contrast to other tissue types, carcinoma in situ of the bladder gives rise to an increase in electrical impedance over the kHz-MHz frequency range in comparison to normal tissue. Finite element models of the urothelium and the underlying superficial lamina propria have been constructed and solved in order to ascertain the influence of structural changes associated with malignancy, oedema and inflammation on the measured electrical properties of the tissue. Sensitivity analysis of results from a composite tissue model suggests that the increase in lymphocyte density in the lamina propria associated with an inflammatory response to the infiltration of urine into the tissue may explain these unusual electrical properties.
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Affiliation(s)
- D C Walker
- Department of Computer Science, University of Sheffield, Regent Court, 211 Portobello Street, Sheffield S1 4DP, UK.
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23
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Abstract
In this paper, we describe the theory and practical implementation of an electrical impedance probe for making in vivo measurements of the electrical admittance of living tissue. The probe uses concentric annular electrodes and is shown to sample a more localized, yet greater, volume of tissue than the standard four-electrode probe. We have developed a mathematical model for the conduction of current between the probe electrodes assuming that we are investigating a uniform, isotropic, semi-infinite region and taking into account the contact impedance between the electrodes and the organ. The electric fields produced by the probe have been calculated by solving a weakly singular Fredholm integral equation of the second kind. The size and position of the probe electrodes have been optimized to maximize both the accuracy in the admittance measurement and insensitivity to contact impedance. A probe and driving hardware have been constructed and experimental results are provided showing the accuracy of admittance measurements at 50 and 640 KHz.
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Affiliation(s)
- Kevin S Paulson
- Radiocommunications Research Unit of Rutherford Appleton Laboratory, Chilton, Didcot, OXON OX10 0QX, UK.
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Hose DR, Narracott AJ, Griffiths B, Mahmood S, Gunn J, Sweeney D, Lawford PV. A Thermal Analogy for Modelling Drug Elution from Cardiovascular Stents. Comput Methods Biomech Biomed Engin 2004; 7:257-64. [PMID: 15621648 DOI: 10.1080/10255840412331303140] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Restriction of blood flow by the narrowing or occlusion of arteries is one of the most common presentations of cardiovascular disease. One treatment involves the introduction of a metal scaffold, or stent, designed to prevent recoil and to provide structural stability to the vessel. On the occasions that this treatment is ineffective, failure is usually associated with re-invasion of tissue. This can be prevented by local delivery of drugs which inhibit tissue growth. The drug might be delivered locally in a polymer coating on the stent. This paper develops and explores the use of a thermal analogue of the drug delivery process and the associated three-dimensional convection-diffusion equation to model the spatial and temporal distribution of drug concentration within the vessel wall. This allows the routine use of commercial finite element analysis software to investigate the dynamics of drug distribution, assist in the understanding of the treatment process and develop improved delivery systems. Two applications illustrate how the model might be used to investigate the effects of controllable or measurable parameters on the progression of the process. It is demonstrated that the geometric characteristics of the stent can have significant impact on the homogeneity of the dosing in the vessel wall.
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Affiliation(s)
- D R Hose
- Medical Physics, University of Sheffield, Royal Hallamshire Hospital, UK.
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Walker DC, Southgate J, Hill G, Holcombe M, Hose DR, Wood SM, Mac Neil S, Smallwood RH. The epitheliome: agent-based modelling of the social behaviour of cells. Biosystems 2004; 76:89-100. [PMID: 15351133 DOI: 10.1016/j.biosystems.2004.05.025] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2003] [Revised: 07/11/2003] [Accepted: 08/01/2003] [Indexed: 12/13/2022]
Abstract
We have developed a new computational modelling paradigm for predicting the emergent behaviour resulting from the interaction of cells in epithelial tissue. As proof-of-concept, an agent-based model, in which there is a one-to-one correspondence between biological cells and software agents, has been coupled to a simple physical model. Behaviour of the computational model is compared with the growth characteristics of epithelial cells in monolayer culture, using growth media with low and physiological calcium concentrations. Results show a qualitative fit between the growth characteristics produced by the simulation and the in vitro cell models.
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Affiliation(s)
- D C Walker
- Department of Computer Science, University of Sheffield, Sheffield, UK.
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26
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Jones DM, Smallwood RH, Hose DR, Brown BH, Walker DC. Modelling of epithelial tissue impedance measured using three different designs of probe. Physiol Meas 2003; 24:605-23. [PMID: 12812442 DOI: 10.1088/0967-3334/24/2/369] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Impedance measurement is a promising technique for detecting pre-malignant changes in epithelial tissue. This paper considers how the design of the impedance probe affects the ability to discriminate between tissue types. To do this, finite element models of the electrical properties of squamous and glandular columnar epithelia have been used. The glandular tissue model is described here for the first time. Glandular mucosa is found in many regions of the gastrointestinal tract, such as the stomach and intestine, and has a large effective surface area. Firstly, the electrical properties of a small section of gland, with epithelial cells and supportive tissue, are determined. These properties are then used to build up a three-dimensional model of a whole section of mucosa containing many thousands of glands. Measurements using different types of impedance probe were simulated by applying different boundary conditions to the models. Transepithelial impedance, and tetrapolar measurement with a probe placed on the tissue surface have been modelled. In the latter case, the impedance can be affected by conductive fluid, such as mucus, on the tissue surface. This effect has been investigated, and a new design of probe, which uses a guard electrode to counteract this potential source of variability, is proposed.
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Affiliation(s)
- D M Jones
- Medical Physics and Engineering, University of Sheffield, Royal Hallamshire Hospital, Glossop Road, Sheffield, S10 2JF, UK.
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27
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Walker DC, Brown BH, Blackett AD, Tidy J, Smallwood RH. A study of the morphological parameters of cervical squamous epithelium. Physiol Meas 2003; 24:121-35. [PMID: 12636191 DOI: 10.1088/0967-3334/24/1/309] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Electrical impedance spectroscopy is a technique that has been investigated as a potential method for the diagnosis of epithelial carcinomas. Finite element modelling can provide an insight into the patterns of current flow in normal and pathological epithelium and hence aid in the process of probe design optimization. In order to develop a finite element model of the structure of normal and precancerous cervical squamous epithelium, it was first necessary to obtain the mean values and ranges of a number of morphological tissue parameters. The most important parameters in discriminating normal from neoplastic tissue were identified as being cell size and shape distribution, nuclear-to-cytoplasmic volume ratio and volume of extracellular space. A survey of the literature revealed an absence of reliable quantitative data for these parameters. We therefore present the results of our own basic image analysis on normal and pathological tissue sections, which we hope will be of use to other workers wishing to model cervical squamous epithelium, or other similar tissue structures.
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Affiliation(s)
- D C Walker
- Medical Physics and Engineering, University of Sheffield, Floor I, Royal Hallamshire Hospital, Glossop Road, Sheffield S 10 2JF, UK.
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