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Ambrosanio M, Bevacqua MT, LoVetri J, Pascazio V, Isernia T. In-Vivo Electrical Properties Estimation of Biological Tissues by Means of a Multi-Step Microwave Tomography Approach. IEEE TRANSACTIONS ON MEDICAL IMAGING 2024; 43:1983-1994. [PMID: 38224510 DOI: 10.1109/tmi.2024.3354463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2024]
Abstract
The accurate quantitative estimation of the electromagnetic properties of tissues can serve important diagnostic and therapeutic medical purposes. Quantitative microwave tomography is an imaging modality that can provide maps of the in-vivo electromagnetic properties of the imaged tissues, i.e. both the permittivity and the electric conductivity. A multi-step microwave tomography approach is proposed for the accurate retrieval of such spatial maps of biological tissues. The underlying idea behind the new imaging approach is to progressively add details to the maps in a step-wise fashion starting from single-frequency qualitative reconstructions. Multi-frequency microwave data is utilized strategically in the final stage. The approach results in improved accuracy of the reconstructions compared to inversion of the data in a single step. As a case study, the proposed workflow was tested on an experimental microwave data set collected for the imaging of the human forearm. The human forearm is a good test case as it contains several soft tissues as well as bone, exhibiting a wide range of values for the electrical properties.
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Kordić A, Šarolić A. Dielectric Spectroscopy Shows a Permittivity Contrast between Meningioma Tissue and Brain White and Gray Matter-A Potential Physical Biomarker for Meningioma Discrimination. Cancers (Basel) 2023; 15:4153. [PMID: 37627181 PMCID: PMC10452737 DOI: 10.3390/cancers15164153] [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: 07/08/2023] [Revised: 07/22/2023] [Accepted: 08/11/2023] [Indexed: 08/27/2023] Open
Abstract
The effectiveness of surgical resection of meningioma, the most common primary CNS tumor, depends on the capability to intraoperatively discriminate between the meningioma tissue and the surrounding brain white and gray matter tissues. Aiming to find a potential biomarker based on tissue permittivity, dielectric spectroscopy of meningioma, white matter, and gray matter ex vivo tissues was performed using the open-ended coaxial probe method in the microwave frequency range from 0.5 to 18 GHz. The averages and the 95% confidence intervals of the measured permittivity for each tissue were compared. The results showed the absence of overlap between the 95% confidence intervals for meningioma tissue and for brain white and gray matter, indicating a significant difference in average permittivity (p ≤ 0.05) throughout almost the entire measured frequency range, with the most pronounced contrast found between 2 GHz and 5 GHz. The discovered contrast is relevant as a potential physical biomarker to discriminate meningioma tissue from the surrounding brain tissues by means of permittivity measurement, e.g., for intraoperative meningioma margin assessment. The permittivity models for each tissue, developed in this study as its byproducts, will allow more accurate electromagnetic modeling of brain tumor and healthy tissues, facilitating the development of new microwave-based medical devices and tools.
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Affiliation(s)
- Anton Kordić
- Department of Neurosurgery, University Hospital Centre Zagreb, 10000 Zagreb, Croatia
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Buisson C, Mounien L, Sicard F, Landrier JF, Tishkova V, Sabouroux P. Dielectric and Biological Characterization of Liver Tissue in a High-Fat Diet Mouse Model. SENSORS (BASEL, SWITZERLAND) 2023; 23:3434. [PMID: 37050495 PMCID: PMC10098745 DOI: 10.3390/s23073434] [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: 02/14/2023] [Revised: 03/15/2023] [Accepted: 03/18/2023] [Indexed: 06/19/2023]
Abstract
Hepatic steatosis may be caused by type 2 diabetes or obesity and is one of the origins of chronic liver disease. A non-invasive technique based on microwave propagation can be a good solution to monitor hepatic tissue pathologies. The present work is devoted to the dielectric permittivity measurements in healthy and fatty liver in the microwave range. A mouse model following normal and high sugar/glucose (HFS) diets was used. We demonstrated the change in the triglyceride and glucose concentration in the hepatic tissue of HFS diet mice. The difference in the dielectric permittivity of healthy and fatty liver was observed in the range from 100 MHz to 2 GHz. The dielectric permittivity was found to be 42 in the healthy tissue and 31 in the fatty liver tissue at 1 GHz. The obtained results demonstrate that dielectric permittivity can be a sensitive tool to distinguish between healthy and fatty hepatic tissue.
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Affiliation(s)
- Clément Buisson
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
- Aix Marseille Univ, CNRS, CINaM, Marseille, France
| | - Lourdes Mounien
- Aix-Marseille Université, C2VN, INRAE, INSERM, Marseille, France
| | - Flavie Sicard
- Aix-Marseille Université, C2VN, INRAE, INSERM, Marseille, France
- PhenoMARS Aix-Marseille Technology Platform, CriBiom, Marseille, France
| | | | | | - Pierre Sabouroux
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
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Samaddar P, Mishra AK, Gaddam S, Singh M, Modi VK, Gopalakrishnan K, Bayer RL, Igreja Sa IC, Khanal S, Hirsova P, Kostallari E, Dey S, Mitra D, Roy S, Arunachalam SP. Machine Learning-Based Classification of Abnormal Liver Tissues Using Relative Permittivity. SENSORS (BASEL, SWITZERLAND) 2022; 22:9919. [PMID: 36560303 PMCID: PMC9781624 DOI: 10.3390/s22249919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/04/2022] [Accepted: 12/08/2022] [Indexed: 06/17/2023]
Abstract
The search for non-invasive, fast, and low-cost diagnostic tools has gained significant traction among many researchers worldwide. Dielectric properties calculated from microwave signals offer unique insights into biological tissue. Material properties, such as relative permittivity (εr) and conductivity (σ), can vary significantly between healthy and unhealthy tissue types at a given frequency. Understanding this difference in properties is key for identifying the disease state. The frequency-dependent nature of the dielectric measurements results in large datasets, which can be postprocessed using artificial intelligence (AI) methods. In this work, the dielectric properties of liver tissues in three mouse models of liver disease are characterized using dielectric spectroscopy. The measurements are grouped into four categories based on the diets or disease state of the mice, i.e., healthy mice, mice with non-alcoholic steatohepatitis (NASH) induced by choline-deficient high-fat diet, mice with NASH induced by western diet, and mice with liver fibrosis. Multi-class classification machine learning (ML) models are then explored to differentiate the liver tissue groups based on dielectric measurements. The results show that the support vector machine (SVM) model was able to differentiate the tissue groups with an accuracy up to 90%. This technology pipeline, thus, shows great potential for developing the next generation non-invasive diagnostic tools.
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Affiliation(s)
- Poulami Samaddar
- Microwave Engineering and Imaging Laboratory (MEIL), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Anup Kumar Mishra
- GIH Artificial Intelligence Laboratory (GAIL), Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Sunil Gaddam
- Microwave Engineering and Imaging Laboratory (MEIL), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Vaishnavi K. Modi
- Microwave Engineering and Imaging Laboratory (MEIL), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Keerthy Gopalakrishnan
- Microwave Engineering and Imaging Laboratory (MEIL), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Rachel L. Bayer
- Gastroenterology Research, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA
| | - Ivone Cristina Igreja Sa
- Gastroenterology Research, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Biological and Medical Sciences, Faculty of Pharmacy in Hradec Králové, Charles University, Heyrovskeho 1203, 500 05 Hradec Kralove, Czech Republic
| | - Shalil Khanal
- Gastroenterology Research, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA
| | - Petra Hirsova
- Gastroenterology Research, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA
| | - Enis Kostallari
- Gastroenterology Research, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA
| | - Shuvashis Dey
- Microwave Engineering and Imaging Laboratory (MEIL), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Department of Electrical and Computer Engineering, North Dakota State University, Fargo, ND 58105, USA
| | - Dipankar Mitra
- Microwave Engineering and Imaging Laboratory (MEIL), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Department of Computer Science, University of Wisconsin, La Crosse, WI 54601, USA
| | - Sayan Roy
- Microwave Engineering and Imaging Laboratory (MEIL), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Department of Electrical Engineering and Computer Science, South Dakota Mines, Rapid City, SD 57701, USA
| | - Shivaram P. Arunachalam
- Microwave Engineering and Imaging Laboratory (MEIL), Division of Gastroenterology & Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
- GIH Artificial Intelligence Laboratory (GAIL), Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
- Department of Radiology, Mayo Clinic, Rochester, MN 55905, USA
- Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
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Sasaki K, Porter E, Rashed EA, Farrugia L, Schmid G. Measurement and image-based estimation of dielectric properties of biological tissues —past, present, and future—. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac7b64] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Accepted: 06/22/2022] [Indexed: 12/23/2022]
Abstract
Abstract
The dielectric properties of biological tissues are fundamental pararmeters that are essential for electromagnetic modeling of the human body. The primary database of dielectric properties compiled in 1996 on the basis of dielectric measurements at frequencies from 10 Hz to 20 GHz has attracted considerable attention in the research field of human protection from non-ionizing radiation. This review summarizes findings on the dielectric properties of biological tissues at frequencies up to 1 THz since the database was developed. Although the 1996 database covered general (normal) tissues, this review also covers malignant tissues that are of interest in the research field of medical applications. An intercomparison of dielectric properties based on reported data is presented for several tissue types. Dielectric properties derived from image-based estimation techniques developed as a result of recent advances in dielectric measurement are also included. Finally, research essential for future advances in human body modeling is discussed.
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Utilization of dielectric properties for assessment of liver ischemia-reperfusion injury in vivo and during machine perfusion. Sci Rep 2022; 12:11183. [PMID: 35778457 PMCID: PMC9249774 DOI: 10.1038/s41598-022-14817-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 06/13/2022] [Indexed: 11/20/2022] Open
Abstract
There is a shortage of donor livers and patients consequently die on waiting lists worldwide. Livers are discarded if they are clinically judged to have a high risk of non-function following transplantation. With the aim of extending the pool of available donor livers, we assessed the condition of porcine livers by monitoring the microwave dielectric properties. A total of 21 livers were divided into three groups: control with no injury (CON), biliary injury by hepatic artery occlusion (AHEP), and overall hepatic injury by static cold storage (SCS). All were monitored for four hours in vivo, followed by ex vivo plurithermic machine perfusion (PMP). Permittivity data was modeled with a two-pole Cole–Cole equation, and dielectric properties from one-hour intervals were analyzed during in vivo and normothermic machine perfusion (NMP). A clear increasing trend in the conductivity was observed in vivo in the AHEP livers compared to the control livers. After four hours of NMP, separations in the conductivity were observed between the three groups. Our results indicate that dielectric relaxation spectroscopy (DRS) can be used to detect and differentiate liver injuries, opening for a standardized and reliable point of evaluation for livers prior to transplantation.
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Zia G, Sebek J, Prakash P. Temperature-dependent dielectric properties of human uterine fibroids over microwave frequencies. Biomed Phys Eng Express 2021; 7. [PMID: 34534970 DOI: 10.1088/2057-1976/ac27c2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 09/17/2021] [Indexed: 12/15/2022]
Abstract
Microwave ablation is under investigation as a minimally-invasive treatment for uterine fibroids. Computational models play a vital role in the development, evaluation and characterization of candidate ablation devices. The temperature-dependent dielectric properties of fibroid tissue are essential for accurate computational modeling.Objective:To measure the broadband temperature-dependent dielectric properties of uterine fibroids excised during hysterectomy procedures.Methods: The open-ended coaxial probe method was employed for measuring the broadband dielectric properties of freshly excised human uterine fibroid samples (n = 6) obtained from an IRB-approved tissue bank. The dielectric properties (relative permittivity,εr, and effective electrical conductivity,σeff) were evaluated at temperatures ranging from 23 °C-150 °C, over the frequency range of 0.5-6 GHz. Linear piecewise parametrization with respect to temperature and quadratic parametrization with respect to frequency was applied to characterize broadband temperature-dependent dielectric properties of fibroid tissue.Results: The baseline room temperature values ofεrvary from 57.5 ± 5.29 to 44.5 ± 5.77 units andσeffchanges from 0.91 ± 0.19 to 6.02 ± 0.7 S m-1over the frequency range of 0.5-6 GHz. At temperatures close to the water vaporization point,εr, drops considerably i.e. to 12%-14% of its baseline value for all measured frequencies.σeffvalues initially rise till 98 °C and then fall to 11%-13% of their baseline values at 125 °C for frequencies ≤2.45 GHz. Theσefffollows a decreasing trend for frequencies >2.45 GHz and drops to ∼6 % of their baseline room temperature values.Conclusion:The temperature dependent dielectric properties of uterine fibroid tissues over microwave frequency range are reported for the first time in this study. Parametric models of uterine fibroid dielectric properties are also presented for incorporation within computational models of microwave ablation of fibroids.
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Affiliation(s)
- Ghina Zia
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, United States of America
| | - Jan Sebek
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, United States of America.,Department of Circuit Theory, Czech Technical University in Prague, Prague, Czech Republic
| | - Punit Prakash
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, United States of America
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Gerazov B, Caligari Conti DA, Farina L, Farrugia L, Sammut CV, Schembri Wismayer P, Conceição RC. Application of Machine Learning to Predict Dielectric Properties of In Vivo Biological Tissue. SENSORS 2021; 21:s21206935. [PMID: 34696148 PMCID: PMC8541465 DOI: 10.3390/s21206935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/13/2021] [Accepted: 10/16/2021] [Indexed: 11/16/2022]
Abstract
In this paper we revisited a database with measurements of the dielectric properties of rat muscles. Measurements were performed both in vivo and ex vivo; the latter were performed in tissues with varying levels of hydration. Dielectric property measurements were performed with an open-ended coaxial probe between the frequencies of 500 MHz and 50 GHz at a room temperature of 25 °C. In vivo dielectric properties are more valuable for creating realistic electromagnetic models of biological tissue, but these are more difficult to measure and scarcer in the literature. In this paper, we used machine learning models to predict the in vivo dielectric properties of rat muscle from ex vivo dielectric property measurements for varying levels of hydration. We observed promising results that suggest that our model can make a fair estimation of in vivo properties from ex vivo properties.
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Affiliation(s)
- Branislav Gerazov
- Faculty of Electrical Engineering and Information Technologies, Ss Cyril and Methodius University in Skopje, 1000 Skopje, North Macedonia;
| | | | - Laura Farina
- Translational Medical Device Lab, National University of Ireland Galway, H91 TK33 Galway, Ireland;
| | - Lourdes Farrugia
- Department of Physics, University of Malta, MSD 2080 Msida, Malta; (D.A.C.C.); (L.F.); (C.V.S.)
| | - Charles V. Sammut
- Department of Physics, University of Malta, MSD 2080 Msida, Malta; (D.A.C.C.); (L.F.); (C.V.S.)
| | | | - Raquel C. Conceição
- Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
- Correspondence: ; Tel.: +351-217-500-560
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Ištuk N, Porter E, O’Loughlin D, McDermott B, Santorelli A, Abedi S, Joachimowicz N, Roussel H, O’Halloran M. Dielectric Properties of Ovine Heart at Microwave Frequencies. Diagnostics (Basel) 2021; 11:531. [PMID: 33809672 PMCID: PMC8002248 DOI: 10.3390/diagnostics11030531] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/07/2021] [Accepted: 03/11/2021] [Indexed: 12/14/2022] Open
Abstract
Accurate knowledge of the dielectric properties of biological tissues is important in dosimetry studies and for medical diagnostic, monitoring and therapeutic technologies. In particular, the dielectric properties of the heart are used in numerical simulations of radiofrequency and microwave heart ablation. In one recent study, it was demonstrated that the dielectric properties of different components of the heart can vary considerably, contrary to previous literature that treated the heart as a homogeneous organ with measurements that ignored the anatomical location. Therefore, in this study, we record and report the dielectric properties of the heart as a heterogeneous organ. We measured the dielectric properties at different locations inside and outside of the heart over the 500 MHz to 20 GHz frequency range. Different parts of the heart were identified based on the anatomy of the heart and their function; they include the epicardium, endocardium, myocardium, exterior and interior surfaces of atrial appendage, and the luminal surface of the great vessels. The measured dielectric properties for each part of the heart are reported at both a single frequency (2.4 GHz), which is of interest in microwave medical applications, and as parameters of a broadband Debye model. The results show that in terms of dielectric properties, different parts of the heart should not be considered the same, with more than 25% difference in dielectric properties between some parts. The specific Debye models and single frequency dielectric properties from this study can be used to develop more detailed models of the heart to be used in electromagnetic modeling.
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Affiliation(s)
- Niko Ištuk
- Translational Medical Device Laboratory, National University of Ireland Galway, Costello Road, H91 TK33 Galway, Ireland; (B.M.); (M.O.)
| | - Emily Porter
- Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA; (E.P.); (A.S.)
| | - Declan O’Loughlin
- Department of Electronic and Electrical Engineering, Trinity College Dublin, College Green, D02 PN40 Dublin 2, Ireland;
| | - Barry McDermott
- Translational Medical Device Laboratory, National University of Ireland Galway, Costello Road, H91 TK33 Galway, Ireland; (B.M.); (M.O.)
| | - Adam Santorelli
- Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA; (E.P.); (A.S.)
| | - Soroush Abedi
- Sorbonne Université, CNRS, Laboratoire de Génie Electrique et Electronique de Paris, 75252 Paris, France; (S.A.); (N.J.); (H.R.)
- Université Paris-Saclay, CentraleSupélec, CNRS, Laboratoire de Génie Electrique et Electronique de Paris, 91192 Gif-sur-Yvette, France
| | - Nadine Joachimowicz
- Sorbonne Université, CNRS, Laboratoire de Génie Electrique et Electronique de Paris, 75252 Paris, France; (S.A.); (N.J.); (H.R.)
- Université Paris-Saclay, CentraleSupélec, CNRS, Laboratoire de Génie Electrique et Electronique de Paris, 91192 Gif-sur-Yvette, France
| | - Hélène Roussel
- Sorbonne Université, CNRS, Laboratoire de Génie Electrique et Electronique de Paris, 75252 Paris, France; (S.A.); (N.J.); (H.R.)
- Université Paris-Saclay, CentraleSupélec, CNRS, Laboratoire de Génie Electrique et Electronique de Paris, 91192 Gif-sur-Yvette, France
| | - Martin O’Halloran
- Translational Medical Device Laboratory, National University of Ireland Galway, Costello Road, H91 TK33 Galway, Ireland; (B.M.); (M.O.)
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Application of Artificial Neural Networks for Accurate Determination of the Complex Permittivity of Biological Tissue. SENSORS 2020; 20:s20164640. [PMID: 32824718 PMCID: PMC7472264 DOI: 10.3390/s20164640] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/11/2020] [Accepted: 08/13/2020] [Indexed: 11/16/2022]
Abstract
Medical devices making use of radio frequency (RF) and microwave (MW) fields have been studied as alternatives to existing diagnostic and therapeutic modalities since they offer several advantages. However, the lack of accurate knowledge of the complex permittivity of different biological tissues continues to hinder progress in of these technologies. The most convenient and popular measurement method used to determine the complex permittivity of biological tissues is the open-ended coaxial line, in combination with a vector network analyser (VNA) to measure the reflection coefficient (S11) which is then converted to the corresponding tissue permittivity using either full-wave analysis or through the use of equivalent circuit models. This paper proposes an innovative method of using artificial neural networks (ANN) to convert measured S11 to tissue permittivity, circumventing the requirement of extending the VNA measurement plane to the coaxial line open end. The conventional three-step calibration technique used with coaxial open-ended probes lacks repeatability, unless applied with extreme care by experienced persons, and is not adaptable to alternative sensor antenna configurations necessitated by many potential diagnostic and monitoring applications. The method being proposed does not require calibration at the tip of the probe, thus simplifying the measurement procedure while allowing arbitrary sensor design, and was experimentally validated using S11 measurements and the corresponding complex permittivity of 60 standard liquid and 42 porcine tissue samples. Following ANN training, validation and testing, we obtained a prediction accuracy of 5% for the complex permittivity.
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Cavagnaro M, Ruvio G. Numerical Sensitivity Analysis for Dielectric Characterization of Biological Samples by Open-Ended Probe Technique. SENSORS 2020; 20:s20133756. [PMID: 32635581 PMCID: PMC7374459 DOI: 10.3390/s20133756] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/26/2020] [Accepted: 07/01/2020] [Indexed: 12/22/2022]
Abstract
Dielectric characterization of biological tissues has become a fundamental aspect of the design of medical treatments based on electromagnetic energy delivery and their pre-treatment planning. Among several measuring techniques proposed in the literature, broadband and minimally-invasive open-ended probe measurements are best-suited for biological tissues. However, several challenges related to measurement accuracy arise when dealing with biological tissues in both ex vivo and in vivo scenarios such as very constrained set-ups in terms of limited sample size and probe positioning. By means of the Finite Integration Technique in the CST Studio Suite® software, the numerical accuracy of the reconstruction of the complex permittivity of a high water-content tissue such as liver and a low water-content tissue such as fat is evaluated for different sample dimensions, different location of the probe, and considering the influence of the background environment. It is found that for high water-content tissues, the insertion depth of the probe into the sample is the most critical parameter on the accuracy of the reconstruction. Whereas when low water-content tissues are measured, the probe could be simply placed in contact with the surface of the sample but a deeper and wider sample is required to mitigate biasing effects from the background environment. The numerical analysis proves to be a valid tool to assess the suitability of a measurement set-up for a target accuracy threshold.
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Affiliation(s)
- Marta Cavagnaro
- Department of Information Engineering, Electronics, and Telecommunications, Sapienza University, Piazzale Aldo Moro 5, 00185 Rome, Italy
- Correspondence: ; Tel.: +39-06-4458-5465
| | - Giuseppe Ruvio
- School of Medicine, National University of Ireland Galway, University Road, H91 TK33 Galway, Ireland;
- Endowave Ltd., Dublin 2, Ireland
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Challenges of Post-measurement Histology for the Dielectric Characterisation of Heterogeneous Biological Tissues. SENSORS 2020; 20:s20113290. [PMID: 32526983 PMCID: PMC7309042 DOI: 10.3390/s20113290] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 06/05/2020] [Accepted: 06/08/2020] [Indexed: 12/28/2022]
Abstract
The dielectric properties of biological tissues are typically measured using the open-ended coaxial probe technique, which is based on the assumption that the tissue sample is homogeneous. Therefore, for heterogeneous tissue samples, additional post-measurement sample processing is conducted. Specifically, post-measurement histological analysis may be performed in order to associate the measured dielectric properties with the tissue types present in a heterogeneous sample. Accurate post-measurement histological analysis enables identification of the constituent tissue types that contributed to the measured dielectric properties, and their relative distributions. There is no standard protocol for conducting post-measurement histological analysis, which leads to high numbers of excluded tissue samples and inconsistencies in the resulting reported data for heterogeneous tissues. To this extent, this study examines the post-measurement histological process and the challenges in associating the acquired dielectric properties with the different tissue types present in heterogeneous samples. The results demonstrate that the histological process inevitably alters the morphology of samples, thus introducing errors in the interpretation of the dielectric properties acquired from heterogeneous biological samples. Notably, sample size was seen to shrink by up to 90% through the histological process, meaning that sensing volume determined from fresh tissues is not directly applicable to histology images.
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Silva NP, Bottiglieri A, Conceição RC, O’Halloran M, Farina L. Characterisation of Ex Vivo Liver Thermal Properties for Electromagnetic-Based Hyperthermic Therapies. SENSORS (BASEL, SWITZERLAND) 2020; 20:E3004. [PMID: 32466323 PMCID: PMC7285484 DOI: 10.3390/s20103004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 05/21/2020] [Accepted: 05/22/2020] [Indexed: 12/18/2022]
Abstract
Electromagnetic-based hyperthermic therapies induce a controlled increase of temperature in a specific tissue target in order to increase the tissue perfusion or metabolism, or even to induce cell necrosis. These therapies require accurate knowledge of dielectric and thermal properties to optimise treatment plans. While dielectric properties have been well investigated, only a few studies have been conducted with the aim of understanding the changes of thermal properties as a function of temperature; i.e., thermal conductivity, volumetric heat capacity and thermal diffusivity. In this study, we experimentally investigate the thermal properties of ex vivo ovine liver in the hyperthermic temperature range, from 25 °C to 97 °C. A significant increase in thermal properties is observed only above 90 °C. An analytical model is developed to model the thermal properties as a function of temperature. Thermal properties are also investigated during the natural cooling of the heated tissue. A reversible phenomenon of the thermal properties is observed; during the cooling, thermal properties followed the same behaviour observed in the heating process. Additionally, tissue density and water content are evaluated at different temperatures. Density does not change with temperature; mass and volume losses change proportionally due to water vaporisation. A 30% water loss was observed above 90 °C.
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Affiliation(s)
- Nuno P. Silva
- Translational Medical Device Lab, National University of Ireland Galway, H91 TK33 Galway, Ireland; (N.P.S.); (A.B.); (M.O.)
- Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisbon, Portugal
| | - Anna Bottiglieri
- Translational Medical Device Lab, National University of Ireland Galway, H91 TK33 Galway, Ireland; (N.P.S.); (A.B.); (M.O.)
| | - Raquel C. Conceição
- Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências Universidade de Lisboa, 1749-016 Lisbon, Portugal;
| | - Martin O’Halloran
- Translational Medical Device Lab, National University of Ireland Galway, H91 TK33 Galway, Ireland; (N.P.S.); (A.B.); (M.O.)
| | - Laura Farina
- Translational Medical Device Lab, National University of Ireland Galway, H91 TK33 Galway, Ireland; (N.P.S.); (A.B.); (M.O.)
- CÚRAM, SFI Research Centre for Medical Devices, National University of Ireland Galway, H91 W2TY Galway, Ireland
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Multiclass Classification of Hepatic Anomalies with Dielectric Properties: From Phantom Materials to Rat Hepatic Tissues. SENSORS 2020; 20:s20020530. [PMID: 31963628 PMCID: PMC7014510 DOI: 10.3390/s20020530] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 12/20/2019] [Accepted: 01/15/2020] [Indexed: 11/17/2022]
Abstract
Open-ended coaxial probes can be used as tissue characterization devices. However, the technique suffers from a high error rate. To improve this technology, there is a need to decrease the measurement error which is reported to be more than 30% for an in vivo measurement setting. This work investigates the machine learning (ML) algorithms’ ability to decrease the measurement error of open-ended coaxial probe techniques to enable tissue characterization devices. To explore the potential of this technique as a tissue characterization device, performances of multiclass ML algorithms on collected in vivo rat hepatic tissue and phantom dielectric property data were evaluated. Phantoms were used for investigating the potential of proliferating the data set due to difficulty of in vivo data collection from tissues. The dielectric property measurements were collected from 16 rats with hepatic anomalies, 8 rats with healthy hepatic tissues, and in house phantoms. Three ML algorithms, k-nearest neighbors (kNN), logistic regression (LR), and random forests (RF) were used to classify the collected data. The best performance for the classification of hepatic tissues was obtained with 76% accuracy using the LR algorithm. The LR algorithm performed classification with over 98% accuracy within the phantom data and the model generalized to in vivo dielectric property data with 48% accuracy. These findings indicate first, linear models, such as logistic regression, perform better on dielectric property data sets. Second, ML models fitted to the data collected from phantom materials can partly generalize to in vivo dielectric property data due to the discrepancy between dielectric property variability.
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15
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Bonello J, Elahi MA, Porter E, O’Hollaran M, Farrugia L, Sammut CV. An investigation of the variation of dielectric properties of ovine lung tissue with temperature. Biomed Phys Eng Express 2019. [DOI: 10.1088/2057-1976/aaee40] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Lopresto V, Argentieri A, Pinto R, Cavagnaro M. Temperature dependence of thermal properties of ex vivo liver tissue up to ablative temperatures. ACTA ACUST UNITED AC 2019; 64:105016. [DOI: 10.1088/1361-6560/ab1663] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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17
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Ultra-Wideband Temperature Dependent Dielectric Spectroscopy of Porcine Tissue and Blood in the Microwave Frequency Range. SENSORS 2019; 19:s19071707. [PMID: 30974770 PMCID: PMC6479484 DOI: 10.3390/s19071707] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 03/22/2019] [Accepted: 04/04/2019] [Indexed: 12/20/2022]
Abstract
The knowledge of frequency and temperature dependent dielectric properties of tissue is essential to develop ultra-wideband diagnostic technologies, such as a non-invasive temperature monitoring system during hyperthermia treatment. To this end, we characterized the dielectric properties of animal liver, muscle, fat and blood in the microwave frequency range from 0.5 GHz to 7 GHz and in the temperature range between 30 °C and 50 °C. The measured data were modeled to a two-pole Cole-Cole model and a second-order polynomial was introduced to fit the Cole-Cole parameters as a function of temperature. The parametric model provides access to the dielectric properties of tissue at any frequency and temperature in the specified range.
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18
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Pollacco DA, Farrugia L, Conti MC, Farina L, Schembri Wismayer P, Sammut CV. Characterization of the dielectric properties of biological tissues using mixture equations and correlations to different states of hydration. Biomed Phys Eng Express 2019. [DOI: 10.1088/2057-1976/aafc1a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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19
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Open-Ended Coaxial Probe Technique for Dielectric Measurement of Biological Tissues: Challenges and Common Practices. Diagnostics (Basel) 2018; 8:diagnostics8020040. [PMID: 29874833 PMCID: PMC6023382 DOI: 10.3390/diagnostics8020040] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 05/24/2018] [Accepted: 06/02/2018] [Indexed: 01/06/2023] Open
Abstract
Electromagnetic (EM) medical technologies are rapidly expanding worldwide for both diagnostics and therapeutics. As these technologies are low-cost and minimally invasive, they have been the focus of significant research efforts in recent years. Such technologies are often based on the assumption that there is a contrast in the dielectric properties of different tissue types or that the properties of particular tissues fall within a defined range. Thus, accurate knowledge of the dielectric properties of biological tissues is fundamental to EM medical technologies. Over the past decades, numerous studies were conducted to expand the dielectric repository of biological tissues. However, dielectric data is not yet available for every tissue type and at every temperature and frequency. For this reason, dielectric measurements may be performed by researchers who are not specialists in the acquisition of tissue dielectric properties. To this end, this paper reviews the tissue dielectric measurement process performed with an open-ended coaxial probe. Given the high number of factors, including equipment- and tissue-related confounders, that can increase the measurement uncertainty or introduce errors into the tissue dielectric data, this work discusses each step of the coaxial probe measurement procedure, highlighting common practices, challenges, and techniques for controlling and compensating for confounders.
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Salahuddin S, Gioia AL, Shahzad A, Elahi MA, Kumar A, Kilroy D, Porter E, O’Halloran M. An anatomically accurate dielectric profile of the porcine kidney. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aaad7b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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21
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Shahzad A, Khan S, Jones M, Dwyer RM, O’Halloran M. Investigation of the effect of dehydration on tissue dielectric properties in
ex vivo
measurements. Biomed Phys Eng Express 2017. [DOI: 10.1088/2057-1976/aa74c4] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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