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Zheng HY, Li Y, Wang N, Xiang Y, Liu JH, Zhang LD, Huang L, Wang ZY. A novel framework for three-dimensional electrical impedance tomography reconstruction of maize ear via feature reconfiguration and residual networks. PeerJ Comput Sci 2024; 10:e1944. [PMID: 38660147 PMCID: PMC11042020 DOI: 10.7717/peerj-cs.1944] [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: 10/03/2023] [Accepted: 02/27/2024] [Indexed: 04/26/2024]
Abstract
Electrical impedance tomography (EIT) provides an indirect measure of the physiological state and growth of the maize ear by reconstructing the distribution of electrical impedance. However, the two-dimensional (2D) EIT within the electrode plane finds it challenging to comprehensively represent the spatial distribution of conductivity of the intact maize ear, including the husk, kernels, and cob. Therefore, an effective method for 3D conductivity reconstruction is necessary. In practical applications, fluctuations in the contact impedance of the maize ear occur, particularly with the increase in the number of grids and computational workload during the reconstruction of 3D spatial conductivity. These fluctuations may accentuate the ill-conditioning and nonlinearity of the EIT. To address these challenges, we introduce RFNetEIT, a novel computational framework specifically tailored for the absolute imaging of the three-dimensional electrical impedance of maize ear. This strategy transforms the reconstruction of 3D electrical conductivity into a regression process. Initially, a feature map is extracted from measured boundary voltage via a data reconstruction module, thereby enhancing the correlation among different dimensions. Subsequently, a nonlinear mapping model of the 3D spatial distribution of the boundary voltage and conductivity is established, utilizing the residual network. The performance of the proposed framework is assessed through numerical simulation experiments, acrylic model experiments, and maize ear experiments. Our experimental results indicate that our method yields superior reconstruction performance in terms of root-mean-square error (RMSE), correlation coefficient (CC), structural similarity index (SSIM), and inverse problem-solving time (IPST). Furthermore, the reconstruction experiments on maize ears demonstrate that the method can effectively reconstruct the 3D conductivity distribution.
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Affiliation(s)
- Hai-Ying Zheng
- College of Information and Electrical Engineering, China Agricultural University, Beijing, China
- Key Laboratory of Agricultural Information Acquisition Technology (Beijing), Ministry of Agriculture, Beijing, China
| | - Yang Li
- College of Information and Electrical Engineering, China Agricultural University, Beijing, China
- Key Laboratory of Modern Precision Agriculture System Integration Research, Ministry of Education, Beijing, China
| | - Nan Wang
- College of Information and Electrical Engineering, China Agricultural University, Beijing, China
- Key Laboratory of Agricultural Information Acquisition Technology (Beijing), Ministry of Agriculture, Beijing, China
| | - Yang Xiang
- College of Information and Electrical Engineering, China Agricultural University, Beijing, China
- Key Laboratory of Modern Precision Agriculture System Integration Research, Ministry of Education, Beijing, China
| | - Jin-Hang Liu
- College of Information and Electrical Engineering, China Agricultural University, Beijing, China
- Key Laboratory of Agricultural Information Acquisition Technology (Beijing), Ministry of Agriculture, Beijing, China
| | - Liu-Deng Zhang
- College of Information and Electrical Engineering, China Agricultural University, Beijing, China
- Key Laboratory of Modern Precision Agriculture System Integration Research, Ministry of Education, Beijing, China
| | - Lan Huang
- College of Information and Electrical Engineering, China Agricultural University, Beijing, China
- Key Laboratory of Agricultural Information Acquisition Technology (Beijing), Ministry of Agriculture, Beijing, China
| | - Zhong-Yi Wang
- College of Information and Electrical Engineering, China Agricultural University, Beijing, China
- Key Laboratory of Modern Precision Agriculture System Integration Research, Ministry of Education, Beijing, China
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2
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Frerichs I, Vogt B, Deuss K, Hennig V, Schädler D, Händel C. Distribution of regional lung function in upright healthy subjects determined by electrical impedance tomography in two chest examination planes. Physiol Meas 2024; 45:015001. [PMID: 38096575 DOI: 10.1088/1361-6579/ad15ac] [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: 09/05/2023] [Accepted: 12/14/2023] [Indexed: 12/20/2023]
Abstract
Objective. The variation in pulmonary gas content induced by ventilation is not uniformly distributed in the lungs. The aim of our study was to characterize the differences in spatial distribution of ventilation in two transverse sections of the chest using electrical impedance tomography (EIT).Approach. Twenty adult never-smokers, 10 women and 10 men (mean age ± SD, 31 ± 9 years), were examined in a sitting position with the EIT electrodes placed consecutively in a caudal (6th intercostal space) and a cranial (4th intercostal space) chest location. EIT data were acquired during quiet breathing, slow and forced full expiration manoeuvres. Impedance variations representing tidal volume (VT), vital capacity (VC), forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were calculated at the level of individual image pixels and their spatial distribution was determined using the following EIT measures: the centres of ventilation in ventrodorsal (CoVvd) and right-to-left direction (CoVrl), the dorsal and right fractions of ventilation, the coefficient of variation (CV) and the global inhomogeneity (GI) index.Main results. The sums of pixel ventilation-related impedance variations reproduced reliably the volumetric dissimilarities amongVT, VC, FEV1and FVC, with no significant differences noted between the two examination planes. Significant differences in ventilation distribution were found between the planes during tidal breathing and slow full expiration, mainly regarding the ventrodorsal direction, with higher values of CoVvdand dorsal fraction of ventilation in the caudal plane (p< 0.01). No significant differences in the spatial distribution of FEV1and FVC were detected between the examination planes.Significance. The spatial distribution of ventilation differed between the two examination planes only during the relaxed (quiet breathing and slow VC manoeuvre) but not during the forced ventilation. This effect is attributable to the differences in thoracoabdominal mechanics between these types of ventilation.
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Affiliation(s)
- I Frerichs
- University Medical Centre Schleswig-Holstein, Campus Kiel, Department of Anaesthesiology and Intensive Care Medicine, Kiel, Germany
| | - B Vogt
- University Medical Centre Schleswig-Holstein, Campus Kiel, Department of Anaesthesiology and Intensive Care Medicine, Kiel, Germany
| | - K Deuss
- University Medical Centre Schleswig-Holstein, Campus Kiel, Department of Anaesthesiology and Intensive Care Medicine, Kiel, Germany
| | - V Hennig
- University Medical Centre Schleswig-Holstein, Campus Kiel, Department of Anaesthesiology and Intensive Care Medicine, Kiel, Germany
| | - D Schädler
- University Medical Centre Schleswig-Holstein, Campus Kiel, Department of Anaesthesiology and Intensive Care Medicine, Kiel, Germany
| | - C Händel
- University Medical Centre Schleswig-Holstein, Campus Kiel, Department of Anaesthesiology and Intensive Care Medicine, Kiel, Germany
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3
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Park H, Kwon H. Electrical impedance tomography for pulmonary function monitoring without dorsal electrodes. Biomed Phys Eng Express 2023; 10:015003. [PMID: 37931291 DOI: 10.1088/2057-1976/ad0a08] [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: 08/14/2023] [Accepted: 11/06/2023] [Indexed: 11/08/2023]
Abstract
Electrical impedance tomography (EIT) is a non-invasive technology that can visualize conductivity changes inside human body in real time using multiple surface electrodes. For convenience of wearing and application, if no electrodes are attached to the back, a commonly used image reconstruction approach produces poor images of dorsal region. In this study, we developed a special current injection and voltage measurement pattern to well reconstruct the conductivity distribution inside the body even in the absence of dorsal electrodes. The proposed method has proven through numerical and phantom experiments.
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Affiliation(s)
- Hyoungchul Park
- Department of Mathematics, Yonsei University, Wonju, Republic of Korea
| | - Hyeuknam Kwon
- Division of Software, Yonsei University, Wonju, Republic of Korea
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4
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Tan Z, Lu S, Yang L, Xu Y, Qin S, Dai M, Li Z, Zhao Z. Research Trends and Hotspots of Medical Electrical Impedance Tomography Algorithms: A Bibliometric Analysis From 1987 to 2021. Cureus 2023; 15:e49700. [PMID: 38161896 PMCID: PMC10757460 DOI: 10.7759/cureus.49700] [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] [Accepted: 11/30/2023] [Indexed: 01/03/2024] Open
Abstract
Electrical impedance tomography (EIT) is a gradually maturing medical imaging technique that relies on computational algorithms for reconstructing and visualizing internal conductivity distributions within the human body. To provide a comprehensive and objective understanding of the current state and trends in the EIT algorithm research, we conducted bibliometric analysis on a 25-year EIT algorithm research dataset sourced from Web of Science Core Collections. We visualized publication characteristics, collaboration patterns, keywords, and co-cited references. The results indicate a steady increase in annual publications over recent decades. The United States, United Kingdom, China, and South Korea contributed 60% of the articles collaboratively. Keyword analysis unveiled three distinct stages in the evolution of EIT algorithm research: the establishment of fundamental algorithm frameworks, optimization for improved imaging performance, and the development of algorithms for clinical applications. Additionally, there has been a shift in research focus from traditional theories to the incorporation of new methods, such as artificial intelligence. Co-cited references suggest that integrating EIT with other established imaging techniques may emerge as a new trend in EIT algorithm research. In summary, EIT algorithms have been a consistent research focus, with current efforts centered on optimizing algorithms to enhance imaging performance. The emerging research trend involves utilizing more diverse and intersecting algorithms.
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Affiliation(s)
- Zhangjun Tan
- Department of Critical Care Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, CHN
| | - Shiyue Lu
- Department of Critical Care Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, CHN
| | - Lin Yang
- Department of Aerospace Medicine, Fourth Military Medical University, Xi'an, CHN
| | - Yuqing Xu
- Department of Critical Care Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, CHN
| | - Shaojie Qin
- Department of Critical Care Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, CHN
| | - Meng Dai
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, CHN
| | - Zhe Li
- Department of Critical Care Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, CHN
| | - Zhanqi Zhao
- School of Biomedical Engineering, Guangzhou Medical University, Guangzhou, CHN
- Department of Critical Care Medicine, Peking Union Medical College Hospital, Beijing, CHN
- Department of Technical Medicine, Furtwangen University, Villingen-Schwenningen, DEU
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5
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Lo Presti A, Montoya NA, Criscuolo V, Khan G, Khan U, Vecchione R, Falconi C. Fundamentals of Skin Bioimpedances. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2302127. [PMID: 37252818 DOI: 10.1002/adma.202302127] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/14/2023] [Indexed: 06/01/2023]
Abstract
The bioimpedances of tissues beyond the stratum corneum, which is the outermost layer of skin, contain crucial clinical information. Nevertheless, bioimpedance measurements of both the viable skin and the adipose tissue are not widely used, mainly because of the complex multilayered skin structure and the electrically insulating nature of the stratum corneum. Here, a theoretical framework is established for analyzing the impedances of multilayered tissues and, in particular, of skin. Then, strategies are determined for the system-level design of electrodes and electronics, which minimize 4-wire (or tetrapolar) measurement errors even in the presence of a top insulating tissue, thus enabling non-invasive characterizations of tissues beyond the stratum corneum. As an example, non-invasive measurements of bioimpedances of living tissues are demonstrated in the presence of parasitic impedances which are much (e.g., up to 350 times) higher than the bioimpedances of the living tissues beyond the stratum corneum, independently on extreme variations of the barrier (tape stripping) or of the skin-electrode contact impedances (sweat). The results can advance the development of bioimpedance systems for the characterization of viable skin and adipose tissues in several applications, including transdermal drug delivery and the assessment of skin cancer, obesity, dehydration, type 2 diabetes mellitus, cardiovascular risk, and multipotent adult stem cells.
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Affiliation(s)
- Andrea Lo Presti
- Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, Roma, 00133, Italy
| | - Nerio Andrés Montoya
- Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, Roma, 00133, Italy
- School of Physics, Universidad Nacional de Colombia, Medellín, A. A. 3840, Colombia
| | - Valeria Criscuolo
- Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, Roma, 00133, Italy
- Center for Advanced Biomaterial for Health Care, Istituto Italiano di Tecnologia, Largo Barsanti e Matteucci 53, Naples, 80125, Italy
- Faculty of Electrical Engineering and IT, RWTH Aachen, 52062, Aachen, Germany
- Institute for Biological Information Processing - Bioelectronics, IBI-3, Forschungszentrum Juelich, 52428, Aachen, Germany
| | - Gulaly Khan
- School of Electrical Engineering and Computer Science, National University of Sciences and Technology, Sector H-12, Islamabad, 44000, Pakistan
| | - Usman Khan
- School of Electrical Engineering and Computer Science, National University of Sciences and Technology, Sector H-12, Islamabad, 44000, Pakistan
| | - Raffaele Vecchione
- Center for Advanced Biomaterial for Health Care, Istituto Italiano di Tecnologia, Largo Barsanti e Matteucci 53, Naples, 80125, Italy
| | - Christian Falconi
- Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, Roma, 00133, Italy
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Sun T, Yu L, Deng D, Yu M, Chen Y, Chang C, Chen M, Chen S, Chen X, Lin H. Three-dimensional magneto-acousto-electrical tomography (3D MAET) with single-element ultrasound transducer and coded excitation: a phantom validation study. Neurocomputing 2023. [DOI: 10.1016/j.neucom.2023.02.055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2023]
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7
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Ikeno N, Prayitno YAK, Sejati PA, Kawashima D, Takei M. In situ 4D distribution visualization of carbon-black volume fraction in cathode slurry of lithium-ion battery by multi-layered electrical resistance tomography (mlERT). ADV POWDER TECHNOL 2022. [DOI: 10.1016/j.apt.2022.103766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Image quality improvement of magneto-acousto-electrical tomography with Barker coded excitation. Biomed Signal Process Control 2022. [DOI: 10.1016/j.bspc.2022.103823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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9
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Borgmann S, Linz K, Braun C, Dzierzawski P, Spassov S, Wenzel C, Schumann S. Lung area estimation using functional tidal electrical impedance variation images and active contouring. Physiol Meas 2022; 43. [PMID: 35764094 DOI: 10.1088/1361-6579/ac7cc3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 06/28/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Electrical impedance tomography is a valuable tool for monitoring global and regional lung mechanics. To evaluate the recorded data, an accurate estimate of the lung area is crucial. APPROACH We present two novel methods for estimating the lung area using functional tidal images or active contouring methods. A convolutional neural network was trained to determine, whether or not the heart region was visible within tidal images. In addition, the effects of lung area mirroring were investigated. The performance of the methods and the effects of mirroring were evaluated via a score based on the impedance magnitudes in functional tidal images. MAIN RESULTS Our analyses showed that the method based on functional tidal images provided the best estimate of the lung area. Mirroring of the lung area had an impact on the accuracy of area estimation for both methods. The achieved accuracy of the neural network's classification was 94%. For images without a visible heart area, the subtraction of a heart template proved to be a pragmatic approach with good results. SIGNIFICANCE In summary, we developed a routine for estimation of the lung area combined with estimation of the heart area in electrical impedance tomography images.
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Affiliation(s)
- Silke Borgmann
- Universitatsklinikum Freiburg, Hugstetter Straße 55, Freiburg, 79106, GERMANY
| | - Kim Linz
- Universitatsklinikum Freiburg, Hugstetter Straße 55, Freiburg, 79106, GERMANY
| | - Christian Braun
- Universitatsklinikum Freiburg, Hugstetter Straße 55, Freiburg, 79106, GERMANY
| | - Patryk Dzierzawski
- Universitatsklinikum Freiburg, Hugstetter Straße 55, Freiburg, 79106, GERMANY
| | - Sashko Spassov
- Universitatsklinikum Freiburg, Hugstetter Straße 55, Freiburg, 79106, GERMANY
| | - Christin Wenzel
- Anesthesiology and Critical Care, University of Freiburg Faculty of Medicine, Hugstetter Straße 55, Freiburg, 79106, GERMANY
| | - Stefan Schumann
- Universitatsklinikum Freiburg, Hugstetter Straße 55, Freiburg, 79106, GERMANY
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10
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Kim YZ, Choi HY, Choi YS, Kim CY, Lee YJ, Chung SH. Surfactant Treatment Shows Higher Correlation Between Ventilator and EIT Tidal Volumes in an RDS Animal Model. Front Physiol 2022; 13:814320. [PMID: 35514340 PMCID: PMC9065679 DOI: 10.3389/fphys.2022.814320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Accepted: 03/17/2022] [Indexed: 11/25/2022] Open
Abstract
Neonatal respiratory distress syndrome (RDS) is a condition of pulmonary surfactant insufficiency in the premature newborn. As such, artificial pulmonary surfactant administration is a key treatment. Despite continued improvement in the clinical outcomes of RDS, there are currently no established bedside tools to monitor whether pulmonary surfactant is effectively instilled throughout the lungs. Electrical impedance tomography (EIT) is an emerging technique in which physiological functions are monitored on the basis of temporal changes in conductivity of different tissues in the body. In this preliminary study, we aimed to assess how EIT tidal volumes correlate with ventilator tidal volumes in an RDS animal model, namely untreated, surfactant-treated, and normal control rabbit pups. Tidal volumes were measured simultaneously on an EIT system and a mechanical ventilator and compared at different peak inspiratory pressures. The linear correlation between tidal volumes measured by EIT and by ventilator had an R2 of 0.71, 0.76 and 0.86 in the untreated, surfactant-treated, and normal control groups, respectively. Bland–Altman analysis showed a good correlation between the measurements obtained with these two modalities. The intraclass correlation coefficients (ICC) between ventilator tidal volume and EIT tidal volume were 0.83, 0.87, and 0.93 (all p < 0.001) in the untreated, surfactant-treated, and normal control groups, respectively, indicating that the higher ICC value, the better inflated status of the lung. In conclusion, we demonstrated that EIT tidal volume correlated with ventilator tidal volume. ICC was higher in the surfactant treated group.
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Affiliation(s)
- Yoon Zi Kim
- Department of Pediatrics, College of Medicine Kyung Hee University, Seoul, South Korea
| | - Hee Yoon Choi
- Department of Pediatrics, College of Medicine Kyung Hee University, Seoul, South Korea
| | - Yong Sung Choi
- Department of Pediatrics, College of Medicine Kyung Hee University, Seoul, South Korea
| | - Chae Young Kim
- Department of Pediatrics, College of Medicine Kyung Hee University, Seoul, South Korea
| | - Young Joo Lee
- Department of Obstetrics and Gynecology, College of Medicine Kyung Hee University, Seoul, South Korea
| | - Sung Hoon Chung
- Department of Pediatrics, College of Medicine Kyung Hee University, Seoul, South Korea
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11
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Liu Z, Bagnaninchi P, Yang Y. Impedance-Optical Dual-Modal Cell Culture Imaging With Learning-Based Information Fusion. IEEE TRANSACTIONS ON MEDICAL IMAGING 2022; 41:983-996. [PMID: 34797763 DOI: 10.1109/tmi.2021.3129739] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
While Electrical Impedance Tomography (EIT) has found many biomedicine applications, better image quality is needed to provide quantitative analysis for tissue engineering and regenerative medicine. This paper reports an impedance-optical dual-modal imaging framework that primarily targets at high-quality 3D cell culture imaging and can be extended to other tissue engineering applications. The framework comprises three components, i.e., an impedance-optical dual-modal sensor, the guidance image processing algorithm, and a deep learning model named multi-scale feature cross fusion network (MSFCF-Net) for information fusion. The MSFCF-Net has two inputs, i.e., the EIT measurement and a binary mask image generated by the guidance image processing algorithm, whose input is an RGB microscopic image. The network then effectively fuses the information from the two different imaging modalities and generates the final conductivity image. We assess the performance of the proposed dual-modal framework by numerical simulation and MCF-7 cell imaging experiments. The results show that the proposed method could improve the image quality notably, indicating that impedance-optical joint imaging has the potential to reveal the structural and functional information of tissue-level targets simultaneously.
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12
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Frerichs I, Lasarow L, Strodthoff C, Vogt B, Zhao Z, Weiler N. Spatial Ventilation Inhomogeneity Determined by Electrical Impedance Tomography in Patients With Chronic Obstructive Lung Disease. Front Physiol 2021; 12:762791. [PMID: 34966289 PMCID: PMC8712108 DOI: 10.3389/fphys.2021.762791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 11/16/2021] [Indexed: 11/13/2022] Open
Abstract
The aim of this study was to examine whether electrical impedance tomography (EIT) could determine the presence of ventilation inhomogeneity in patients with chronic obstructive lung disease (COPD) from measurements carried out not only during conventional forced full expiration maneuvers but also from forced inspiration maneuvers and quiet tidal breathing and whether the inhomogeneity levels were comparable among the phases and higher than in healthy subjects. EIT data were acquired in 52 patients with exacerbated COPD (11 women, 41 men, 68 ± 11 years) and 14 healthy subjects (6 women, 8 men, 38 ± 8 years). Regional lung function parameters of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), forced inspiratory vital capacity (FIVC), forced inspiratory volume in 1 s (FIV1), and tidal volume (V T ) were determined in 912 image pixels. The spatial inhomogeneity of the pixel parameters was characterized by the coefficients of variation (CV) and the global inhomogeneity (GI) index. CV and GI values of pixel FVC, FEV1, FIVC, FIV1, and VT were significantly higher in patients than in healthy subjects (p ≤ 0.0001). The ventilation distribution was affected by the analyzed lung function parameter in patients (CV: p = 0.0024, GI: p = 0.006) but not in healthy subjects. Receiver operating characteristic curves showed that CV and GI discriminated patients from healthy subjects with an area under the curve (AUC) of 0.835 and 0.852 (FVC), 0.845 and 0.867 (FEV1), 0.903 and 0.903 (FIVC), 0.891 and 0.882 (FIV1), and 0.821 and 0.843 (VT), respectively. These findings confirm the ability of EIT to identify increased ventilation inhomogeneity in patients with COPD.
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Affiliation(s)
- Inéz Frerichs
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Livia Lasarow
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Claas Strodthoff
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Barbara Vogt
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Zhanqi Zhao
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China.,Institute of Technical Medicine, Furtwangen University, Villingen-Schwenningen, Germany
| | - Norbert Weiler
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Kiel, Germany
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13
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Groenendaal W, Lee S, van Hoof C. Wearable Bioimpedance Monitoring: Viewpoint for Application in Chronic Conditions. JMIR BIOMEDICAL ENGINEERING 2021. [DOI: 10.2196/22911] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Currently, nearly 6 in 10 US adults are suffering from at least one chronic condition. Wearable technology could help in controlling the health care costs by remote monitoring and early detection of disease worsening. However, in recent years, there have been disappointments in wearable technology with respect to reliability, lack of feedback, or lack of user comfort. One of the promising sensor techniques for wearable monitoring of chronic disease is bioimpedance, which is a noninvasive, versatile sensing method that can be applied in different ways to extract a wide range of health care parameters. Due to the changes in impedance caused by either breathing or blood flow, time-varying signals such as respiration and cardiac output can be obtained with bioimpedance. A second application area is related to body composition and fluid status (eg, pulmonary congestion monitoring in patients with heart failure). Finally, bioimpedance can be used for continuous and real-time imaging (eg, during mechanical ventilation). In this viewpoint, we evaluate the use of wearable bioimpedance monitoring for application in chronic conditions, focusing on the current status, recent improvements, and challenges that still need to be tackled.
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14
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Sun T, Hao P, Chin CT, Deng D, Chen T, Chen Y, Chen M, Lin H, Lu M, Gao Y, Chen S, Chang C, Chen X. Rapid rotational magneto-acousto-electrical tomography with filtered back-projection algorithm based on plane waves. Phys Med Biol 2021; 66. [PMID: 33725674 DOI: 10.1088/1361-6560/abef43] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 03/16/2021] [Indexed: 11/12/2022]
Abstract
Magneto-acousto-electrical tomography (MAET) is designed to produce conductivity images with high spatial resolution for a conducting object. In a previous study, for an irregular conductor, transverse scanning and rotational methods with a focus transducer were combined to collect complete electrical information. This kind of method, however, is time-consuming because of the transverse scanning procedure. In this study, we proposed a novel imaging method based on plane ultrasound waves and a new aspect of projection in rotational MAET. In the proposed method, we achieved the projection in each rotation angle by using plane waves rather than mechanical scanning of the focus waves along the transverse direction. Thus, the imaging time was significantly saved. To verify the proposed method, we derived a measurement formula containing a lateral integration, which built the relationship between the measurement formula and the projection under each rotation angle. Next, we constructed two different numerical models to compute magneto-acousto-electrical signals by using a finite element method and reconstructed the corresponding conductivity parameter images based on a filtered back-projection algorithm. Then, simulated signals under different signal-to-ratios (6, 20, 40, and 60 dB) were generated to test the performance of the proposed algorithm. To improve the image quality, we further analysed the influence of the filters and the frequency scaling factors embedded in the filtered back-projection algorithm. Moreover, we computed the L2norm of the error in case of different frequency scaling factors and measurement noises. Finally, we conducted a phantom experiment with a 64-element linear phased array transducer (center frequency of 2.7 MHz) and reconstructed the conductivity parameter images of the circular phantom with an elliptical hole. The experimental results demonstrated the feasibility and time-efficiency of the proposed rapid rotational MAET.
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Affiliation(s)
- Tong Sun
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Penghui Hao
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Chien Ting Chin
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Dingqian Deng
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Tiemei Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Yi Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Mian Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Haoming Lin
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Minhua Lu
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Yi Gao
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Siping Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Chunqi Chang
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Xin Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
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15
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Xu L, Hu C, Huang Q, Jin K, Zhao P, Wang D, Hou W, Dong L, Hu S, Ma H. Trends and recent development of the microelectrode arrays (MEAs). Biosens Bioelectron 2021; 175:112854. [PMID: 33371989 DOI: 10.1016/j.bios.2020.112854] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 11/20/2020] [Accepted: 11/23/2020] [Indexed: 11/27/2022]
Abstract
In this paper, we reviewed the history of microelectrode arrays (MEAs), compared different microfabrication techniques applied to modern MEAs in terms of their material characters, device properties and application scenarios. Then we discussed the biocompatibility of different MEAs as well as corresponding strategy of improvement. At last, we analyzed the growing trend of MEAs' technical route, expected application of MEAs in the field of Electrical impedance tomography (EIT).
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Affiliation(s)
- Longqian Xu
- CAS Key Laboratory of Bio-medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, No.88 Keling Road, Suzhou, Jiangsu province, 215163, PR China
| | - Chenxuan Hu
- CAS Key Laboratory of Bio-medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, No.88 Keling Road, Suzhou, Jiangsu province, 215163, PR China
| | - Qi Huang
- CAS Key Laboratory of Bio-medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, No.88 Keling Road, Suzhou, Jiangsu province, 215163, PR China
| | - Kai Jin
- CAS Key Laboratory of Bio-medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, No.88 Keling Road, Suzhou, Jiangsu province, 215163, PR China; International Joint Research Center for Nanophotonics and Biophotonics, School of Science, Changchun University of Science and Technology, Changchun, Jilin province, 130022, PR China
| | - Ping Zhao
- CAS Key Laboratory of Bio-medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, No.88 Keling Road, Suzhou, Jiangsu province, 215163, PR China; International Joint Research Center for Nanophotonics and Biophotonics, School of Science, Changchun University of Science and Technology, Changchun, Jilin province, 130022, PR China
| | - Dongping Wang
- CAS Key Laboratory of Bio-medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, No.88 Keling Road, Suzhou, Jiangsu province, 215163, PR China
| | - Wei Hou
- Department of Radiation Oncology & Therapy, The First Hospital of Jilin University, NO.1 Xinmin Street, Changchun, Jilin province, 130021, PR China
| | - Lihua Dong
- Department of Radiation Oncology & Therapy, The First Hospital of Jilin University, NO.1 Xinmin Street, Changchun, Jilin province, 130021, PR China
| | - Siyi Hu
- CAS Key Laboratory of Bio-medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, No.88 Keling Road, Suzhou, Jiangsu province, 215163, PR China
| | - Hanbin Ma
- CAS Key Laboratory of Bio-medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, No.88 Keling Road, Suzhou, Jiangsu province, 215163, PR China.
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16
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Mouskeftara T, Goulas A, Ioannidou D, Ntenti C, Agapakis D, Assimopoulou A, Gika H. A Study of Blood Fatty Acids Profile in Hyperlipidemic and Normolipidemic Subjects in Association with Common PNPLA3 and ABCB1 Polymorphisms. Metabolites 2021; 11:metabo11020090. [PMID: 33557317 PMCID: PMC7915980 DOI: 10.3390/metabo11020090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 01/28/2021] [Accepted: 01/29/2021] [Indexed: 01/06/2023] Open
Abstract
Adiponutrin (patatin-like phospholipase domain-containing 3; PNPLA3), encoded in humans by the PNPLA3 gene, is a protein associated with lipid droplet and endoplasmic reticulum membranes, where it is apparently involved in fatty acid redistribution between triglycerides and phospholipids. A common polymorphism of PNPLA3 (I148M, rs738409), linked to increased PNPLA3 presence on lipid droplets, is a strong genetic determinant of non-alcoholic fatty liver disease (NAFLD) and of its progression. P-glycoprotein (Pgp, MDR1—multidrug resistance protein 1, ABCB1—ATP-binding cassette sub-family B member 1), encoded by the ABCB1 gene, is another membrane protein implicated in lipid homeostasis and steatosis. In the past, common ABCB1 polymorphisms have been associated with the distribution of serum lipids but not with fatty acids (FA) profiles. Similarly, data on the effect of PNPLA3 I148M polymorphism on blood FAs are scarce. In this study, a gas chromatography-flame ionization detection (GC-FID) method was optimized, allowing us to analyze twenty FAs (C14: 0, C15: 0, C15: 1, C16: 0, C16: 1, C17: 0, C17: 1, C18: 0, C18: 1cis, C18: 2cis, C20: 0, C20: 1n9, C20: 2, C20: 3n6, C20: 4n6, C20: 5, C23: 0, C24: 0, C24: 1 and C22: 6) in whole blood, based on the indirect determination of the fatty acids methyl esters (FAMES), in 62 hyperlipidemic patients and 42 normolipidemic controls. FA concentrations were then compared between the different genotypes of the rs738409 and rs2032582 (ABCB1 G2677T) polymorphisms, within and between the hyperlipidemic and normolipidemic groups. The rs738409 polymorphism appears to exert a significant effect on the distribution of blood fatty acids, in a lipidemic and fatty acid saturation state-depending manner. The effect of rs2032582 was less pronounced, but the polymorphism did appear to affect the relative distribution of blood fatty acids between hyperlipidemic patients and normolipidemic controls.
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Affiliation(s)
- Thomai Mouskeftara
- Laboratory of Forensic Medicine and Toxicology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece;
- Biomic AUTh, Center for Interdisciplinary Research and Innovation (CIRI-AUTH), 57001 Thessaloniki, Greece
| | - Antonis Goulas
- Laboratory of Pharmacology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; (A.G.); (D.I.); (C.N.)
| | - Despoina Ioannidou
- Laboratory of Pharmacology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; (A.G.); (D.I.); (C.N.)
| | - Charikleia Ntenti
- Laboratory of Pharmacology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; (A.G.); (D.I.); (C.N.)
| | - Dimitris Agapakis
- Department of Internal Medicine, AHEPA Hospital, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece;
| | - Andreana Assimopoulou
- Natural Products Research Center of Excellence (NatPro-AUTH), Center for Interdisciplinary Research and Innovation (CIRI-AUTH), 57001 Thessaloniki, Greece;
- Laboratory of Organic Chemistry, School of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
| | - Helen Gika
- Laboratory of Forensic Medicine and Toxicology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece;
- Biomic AUTh, Center for Interdisciplinary Research and Innovation (CIRI-AUTH), 57001 Thessaloniki, Greece
- Correspondence:
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17
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Mandija S, Petrov PI, Vink JJT, Neggers SFW, van den Berg CAT. Brain Tissue Conductivity Measurements with MR-Electrical Properties Tomography: An In Vivo Study. Brain Topogr 2021; 34:56-63. [PMID: 33289858 PMCID: PMC7803705 DOI: 10.1007/s10548-020-00813-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 11/28/2020] [Indexed: 01/19/2023]
Abstract
First in vivo brain conductivity reconstructions using Helmholtz MR-Electrical Properties Tomography (MR-EPT) have been published. However, a large variation in the reconstructed conductivity values is reported and these values differ from ex vivo conductivity measurements. Given this lack of agreement, we performed an in vivo study on eight healthy subjects to provide reference in vivo brain conductivity values. MR-EPT reconstructions were performed at 3 T for eight healthy subjects. Mean conductivity and standard deviation values in the white matter, gray matter and cerebrospinal fluid (σWM, σGM, and σCSF) were computed for each subject before and after erosion of regions at tissue boundaries, which are affected by typical MR-EPT reconstruction errors. The obtained values were compared to the reported ex vivo literature values. To benchmark the accuracy of in vivo conductivity reconstructions, the same pipeline was applied to simulated data, which allow knowledge of ground truth conductivity. Provided sufficient boundary erosion, the in vivo σWM and σGM values obtained in this study agree for the first time with literature values measured ex vivo. This could not be verified for the CSF due to its limited spatial extension. Conductivity reconstructions from simulated data verified conductivity reconstructions from in vivo data and demonstrated the importance of discarding voxels at tissue boundaries. The presented σWM and σGM values can therefore be used for comparison in future studies employing different MR-EPT techniques.
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Affiliation(s)
- Stefano Mandija
- Computational Imaging Group for MR Diagnostic & Therapy, Center for Image Sciences, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, 3584 CX, The Netherlands.
- Division of Imaging & Oncology, Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, 3584 CX, The Netherlands.
| | - Petar I Petrov
- Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, 3584 CX, The Netherlands
| | - Jord J T Vink
- Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, 3584 CX, The Netherlands
| | - Sebastian F W Neggers
- Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, 3584 CX, The Netherlands
| | - Cornelis A T van den Berg
- Computational Imaging Group for MR Diagnostic & Therapy, Center for Image Sciences, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, 3584 CX, The Netherlands
- Division of Imaging & Oncology, Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, 3584 CX, The Netherlands
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Noninvasive, simultaneous, and continuous measurements of stroke volume and tidal volume using EIT: feasibility study of animal experiments. Sci Rep 2020; 10:11242. [PMID: 32647206 PMCID: PMC7347894 DOI: 10.1038/s41598-020-68139-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Accepted: 06/18/2020] [Indexed: 12/01/2022] Open
Abstract
Currently, there is no noninvasive method available for simultaneous measurements of tidal volume and stroke volume. Electrical impedance tomography (EIT) has been used for regional lung ventilation imaging. Cardiac EIT imaging, however, has not been successful due to the technical difficulty in extracting weak cardiogenic components. Instead of regional imaging, in this paper, we use the EIT technique to simultaneously measure two global variables of tidal volume and stroke volume. Time-varying patterns of boundary voltage data originating from lung ventilation and cardiac blood flow were extracted from measured boundary voltage data using the principal component analysis (PCA) and independent component analysis (ICA). The source consistency theory was adopted to separately synthesize time-series of boundary voltage data associated with lung ventilation and cardiac blood flow. The respiratory volume signal (RVS) and cardiac volume signal (CVS) were extracted from reconstructed time-difference EIT images of lung ventilation and cardiac blood flow, respectively. After calibrating the volume signals using the mechanical ventilator and the invasive transpulmonary thermodilution (TPTD) method, tidal volume and stroke volume were computed as valley-to-peak values of the RVS and CVS, respectively. The difference in the tidal volume data between EIT and mechanical ventilator was within ± 20 ml from six pigs. The difference in the stroke volume data between EIT and TPTD was within ± 4.7 ml from the same animals. The results show the feasibility of the proposed method as a new noninvasive cardiopulmonary monitoring tool for simultaneous continuous measurements of stroke volume and tidal volume that are two most important vital signs.
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Choi BK, Katoch N, Kim HJ, Park JA, Ko IO, Kwon OI, Woo EJ. Validation of conductivity tensor imaging using giant vesicle suspensions with different ion mobilities. Biomed Eng Online 2020; 19:35. [PMID: 32448134 PMCID: PMC7247266 DOI: 10.1186/s12938-020-00780-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 05/14/2020] [Indexed: 11/10/2022] Open
Abstract
Background Electrical conductivity of a biological tissue at low frequencies can be approximately expressed as a tensor. Noting that cross-sectional imaging of a low-frequency conductivity tensor distribution inside the human body has wide clinical applications of many bioelectromagnetic phenomena, a new conductivity tensor imaging (CTI) technique has been lately developed using an MRI scanner. Since the technique is based on a few assumptions between mobility and diffusivity of ions and water molecules, experimental validations are needed before applying it to clinical studies. Methods We designed two conductivity phantoms each with three compartments. The compartments were filled with electrolytes and/or giant vesicle suspensions. The giant vesicles were cell-like materials with thin insulating membranes. We controlled viscosity of the electrolytes and the giant vesicle suspensions to change ion mobility and therefore conductivity values. The conductivity values of the electrolytes and giant vesicle suspensions were measured using an impedance analyzer before CTI experiments. A 9.4-T research MRI scanner was used to reconstruct conductivity tensor images of the phantoms. Results The CTI technique successfully reconstructed conductivity tensor images of the phantoms with a voxel size of \documentclass[12pt]{minimal}
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\begin{document}$$0.5\times 0.5\times 0.5\hbox { mm}^3$$\end{document}0.5×0.5×0.5mm3. The relative \documentclass[12pt]{minimal}
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\begin{document}$$L^2$$\end{document}L2 errors between the conductivity values measured by the impedance analyzer and those reconstructed by the MRI scanner was between 1.1 and 11.5. Conclusions The accuracy of the new CTI technique was estimated to be high enough for most clinical applications. Future studies of animal models and human subjects should be pursued to show the clinical efficacy of the CTI technique.
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Affiliation(s)
- Bup Kyung Choi
- Department of Medical Engineering, Kyung Hee University, 26, Kyungheedae-ro, Seoul, 02447, South Korea
| | - Nitish Katoch
- Department of Biomedical Engineering, Kyung Hee University, 1732, Deogyeong-daero, Suwon, 17104, South Korea
| | - Hyung Joong Kim
- Department of Biomedical Engineering, Kyung Hee University, 26, Kyungheedae-ro, Seoul, 02447, South Korea
| | - Ji Ae Park
- Division of Applied RI, Korea Institute of Radiological and Medical Science, 75, Nowonro, Seoul, 01812, South Korea
| | - In Ok Ko
- Division of Applied RI, Korea Institute of Radiological and Medical Science, 75, Nowonro, Seoul, 01812, South Korea
| | - Oh In Kwon
- Department of Mathematics, Konkuk University, 120, Neungdong-ro, Seoul, 05029, South Korea
| | - Eung Je Woo
- Department of Biomedical Engineering, Kyung Hee University, 26, Kyungheedae-ro, Seoul, 02447, South Korea.
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Sun X, Lu L, Qi L, Mei Y, Liu X, Chen W. A robust electrical conductivity imaging method with total variation and wavelet regularization. Magn Reson Imaging 2020; 69:28-39. [PMID: 32145270 DOI: 10.1016/j.mri.2020.02.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 01/23/2020] [Accepted: 02/27/2020] [Indexed: 11/29/2022]
Abstract
PURPOSE This study aims to develop and evaluate a robust conductivity imaging method that combines total variation and wavelet regularization to enhance the accuracy of conductivity maps. THEORY AND METHODS The proposed approach is based on a gradient-based method. The central equation is derived from Maxwell's equation and describes the relationship between conductivity and the transceive phase. A linear system equation is obtained via a finite-difference method and solved using a least-squares method. Total variation and wavelet transform regularization terms are added to the minimization problem and solved using the Split Bregman method to improve reconstruction stability. The proposed approach is compared with conventional and gradient-based methods. Numerical simulations are performed to validate the accuracy of the developed method, and the effects of noise are determined. Phantom and in vivo experiments are conducted at 3 T to verify the clinical applicability of the proposed method. RESULTS Numerical simulations show that the proposed method is more robust than other methods and can suppress the effects of noise. The quantitative conductivity value of the phantom experiment agrees with the measured value. The in vivo experiment results present a clear structure, and the conductivity value of the tumor region is significantly higher than that around healthy tissues. CONCLUSION The proposed electrical conductivity imaging method can improve the quality of conductivity reconstruction, and thus, has future clinical applications.
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Affiliation(s)
- Xiangdong Sun
- School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China; School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China
| | - Lijun Lu
- School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China
| | - Li Qi
- School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China
| | - Yingjie Mei
- School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China
| | - Xiaoyun Liu
- School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Wufan Chen
- School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China; School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China.
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Automated gradient-based electrical properties tomography in the human brain using 7 Tesla MRI. Magn Reson Imaging 2019; 63:258-266. [PMID: 31425805 DOI: 10.1016/j.mri.2019.08.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 08/01/2019] [Accepted: 08/15/2019] [Indexed: 12/18/2022]
Abstract
Electrical properties of the brain tissues may yield useful biomarkers for neurological disorders and diseases, as well as contribute to safety assurance of ultra-high-field MRI. It has been reported that using B1 maps from a multi-channel RF coil, the spatial variation of the electrical properties can be robustly retrieved. The absolute electrical property values can then be obtained by spatial integration, given that an integration seed point is assigned. In this study, we propose to exploit automatically detected seed points based on tissue piece-wise homogeneity (Helmholtz equation) for spatial integration. Numerical simulations of a numerical brain model and experiments involving 12 healthy volunteers were performed to demonstrate its feasibility and robustness in various noisy conditions and head positions. For in vivo imaging, we consistently observed higher conductivity and permittivity values in the white and gray matter compared to tabulated ex vivo probe measurement results found in the literature, a discrepancy that may be attributed to ex vivo experimental constraints. Our results suggest that the proposed technique produces consistent brain electrical properties in vivo that may contribute to improving diagnostic and therapeutic decisions.
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22
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Grychtol B, Schramel JP, Braun F, Riedel T, Auer U, Mosing M, Braun C, Waldmann AD, Böhm SH, Adler A. Thoracic EIT in 3D: experiences and recommendations. Physiol Meas 2019; 40:074006. [PMID: 31189141 DOI: 10.1088/1361-6579/ab291d] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE In EIT applications to the thorax, a single electrode plane has typically been used to reconstruct a transverse 2D 'slice'. However, such images can be misleading as EIT is sensitive to contrasts above and below the electrode plane, and ventilation and aeration inhomogeneities can be distributed in complex ways. Using two (or more) electrode planes, 3D EIT images may be reconstructed, but 3D reconstructions are currently little used in thoracic EIT. In this paper, we investigate an incremental pathway towards 3D EIT reconstructions, using two electrode planes to calculate improved transverse slices as an intermediate step. We recommend a specific placement of electrode planes, and further demonstrate the feasibility of multi-slice reconstruction in two species. APPROACH Simulations of the forward and reconstructed sensitivities were analysed for two electrode planes using a 'square' pattern of electrode placement as a function of two variables: the stimulation and measurement 'skip', and the electrode plane separation. Next, single- versus two-plane measurements were compared in a horse and in human volunteers. We further show the feasibility of 3D reconstructions by reconstructing multiple transverse and, unusually, frontal slices during ventilation. MAIN RESULTS Using two electrode planes leads to a reduced position error and improvement in off-plane contrast rejection. 2D reconstructions from two-plane measurements showed better separation of lungs, as compared to the single plane measurements which tend to push contrasts in the center of the image. 3D reconstructions of the same data show anatomically plausible images, inside as well as outside the volume between the two electrode planes. SIGNIFICANCE Based on the results, we recommend EIT electrode planes separated by less than half of the minimum thoracic dimension with a 'skip 4' pattern and 'square' placement to produce images with good slice selectivity.
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Affiliation(s)
- Bartłomiej Grychtol
- Fraunhofer Project Group for Automation in Medicine and Biotechnology, Mannheim, Germany. Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
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Integrated EIT system for functional lung ventilation imaging. Biomed Eng Online 2019; 18:83. [PMID: 31345220 PMCID: PMC6659234 DOI: 10.1186/s12938-019-0701-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 07/12/2019] [Indexed: 02/06/2023] Open
Abstract
Background Electrical impedance tomography (EIT) has been used for functional lung imaging of regional air distributions during mechanical ventilation in intensive care units (ICU). From numerous clinical and animal studies focusing on specific lung functions, a consensus about how to use the EIT technique has been formed lately. We present an integrated EIT system implementing the functions proposed in the consensus. The integrated EIT system could improve the usefulness when monitoring of mechanical ventilation for lung protection so that it could facilitate the clinical acceptance of this new technique. Methods Using a custom-designed 16-channel EIT system with 50 frames/s temporal resolution, the integrated EIT system software was developed to implement five functional images and six EIT measures that can be observed in real-time screen view and analysis screen view mode, respectively. We evaluated the performance of the integrated EIT system with ten mechanically ventilated porcine subjects in normal and disease models. Results Quantitative and simultaneous imaging of tidal volume (TV), end-expiratory lung volume change (\documentclass[12pt]{minimal}
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\begin{document}$$\triangle$$\end{document}▵EELV), compliance, ventilation delay, and overdistension/collapse images were performed. Clinically useful parameters were successfully extracted including anterior/posterior ventilation ratio (A/P ratio), center of ventilation (\documentclass[12pt]{minimal}
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\begin{document}$${\mathrm{CoV}}_{{y}}$$\end{document}CoVy), global inhomogeneity (GI), coefficient of variation (CV), ventilation delay and percentile of overdistension/collapse. The integrated EIT system was demonstrated to suggest an optimal positive end-expiratory pressure (PEEP) for lung protective ventilation in normal and in the disease model of an acute injury. Optimal PEEP for normal and disease model was 2.3 and \documentclass[12pt]{minimal}
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\begin{document}$$7.9 \, {\mathrm{cmH}}_{2}\mathrm{O}$$\end{document}7.9cmH2O, respectively. Conclusions The proposed integrated approach for functional lung ventilation imaging could facilitate clinical acceptance of the bedside EIT imaging method in ICU. Future clinical studies of applying the proposed methods to human subjects are needed to show the clinical significance of the method for lung protective mechanical ventilation and mechanical ventilator weaning in ICU.
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Kaboutari K, Önder Tetik A, Ghalichi E, Soner Gözü M, Zengin R, Güneri Gençer N. Data acquisition system for MAET with magnetic field measurements. ACTA ACUST UNITED AC 2019; 64:115016. [DOI: 10.1088/1361-6560/ab1809] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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25
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Wei Z, Liu D, Chen X. Dominant-Current Deep Learning Scheme for Electrical Impedance Tomography. IEEE Trans Biomed Eng 2019; 66:2546-2555. [PMID: 30629486 DOI: 10.1109/tbme.2019.2891676] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Deep learning has recently been applied to electrical impedance tomography (EIT) imaging. Nevertheless, there are still many challenges that this approach has to face, e.g., targets with sharp corners or edges cannot be well recovered when using circular inclusion training data. This paper proposes an iterative-based inversion method and a convolutional neural network (CNN) based inversion method to recover some challenging inclusions such as triangular, rectangular, or lung shapes, where the CNN-based method uses only random circle or ellipse training data. METHODS First, the iterative method, i.e., bases-expansion subspace optimization method (BE-SOM), is proposed based on a concept of induced contrast current (ICC) with total variation regularization. Second, the theoretical analysis of BE-SOM and the physical concepts introduced there motivate us to propose a dominant-current deep learning scheme for EIT imaging, in which dominant parts of ICC are utilized to generate multi-channel inputs of CNN. RESULTS The proposed methods are tested with both numerical and experimental data, where several realistic phantoms including simulated pneumothorax and pleural effusion pathologies are also considered. CONCLUSIONS AND SIGNIFICANCE Significant performance improvements of the proposed methods are shown in reconstructing targets with sharp corners or edges. It is also demonstrated that the proposed methods are capable of fast, stable, and high-quality EIT imaging, which is promising in providing quantitative images for potential clinical applications.
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Wang Y, Shao Q, Van de Moortele PF, Racila E, Liu J, Bischof J, He B. Mapping electrical properties heterogeneity of tumor using boundary informed electrical properties tomography (BIEPT) at 7T. Magn Reson Med 2019; 81:393-409. [PMID: 30230603 PMCID: PMC6258314 DOI: 10.1002/mrm.27414] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 05/30/2018] [Accepted: 05/31/2018] [Indexed: 11/06/2022]
Abstract
PURPOSES To develop and evaluate a boundary informed electrical properties tomography (BIEPT) technique for high-resolution imaging of tumor electrical properties (EPs) heterogeneity on a rodent tumor xenograft model. METHODS Tumor EP distributions were inferred from a reference area external to the tumor, as well as internal EP spatial variations derived from a plurality of relative transmit B1 measurements at 7T. Edge sparsity constraint was enforced to enhance numerical stability. Phantom experiments were performed to determine the imaging accuracy and sensitivity for structures of various EP values, as well as geometrical sizes down to 1.5 mm. Numerical simulation of a realistic rodent model was used to quantify the algorithm performance in the presence of noise. Eleven athymic rats with human breast cancer xenograft were imaged in vivo, and representative pathological samples were acquired for comparison. RESULTS Reconstructed EPs of the phantoms correspond well to the ground truth acquired from dielectric probe measurements, with the smallest structure reliably detectable being 3 mm. EPs heterogeneity inside a tumor is successfully retrieved in both simulated and experimental cases. In vivo tumor imaging results demonstrate similar local features and spatial patterns to anatomical MRI and pathological slides. The imaged conductivity of necrotic tissue is higher than that of viable tissues, which agrees with our expectation. CONCLUSION BIEPT enables robust detection of tumor EPs heterogeneity with high accuracy and sensitivity to small structures. The retrieved quantitative EPs reflect tumor pathological features (e.g., necrosis). These results provide strong rationale to further expand BIEPT studies toward pathological conditions where EPs may yield valuable, non-invasive biomarkers.
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Affiliation(s)
- Yicun Wang
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
| | - Qi Shao
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455
| | | | - Emilian Racila
- Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455
| | - Jiaen Liu
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - John Bischof
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455
| | - Bin He
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455
- Department of Biomedical Engineering, Carnegie Mellon University, PA 15213, USA
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The influence on acoustic frequency characteristics of conductivity gradual-varying tissue in magnetoacoustic tomography (MAT). Comput Biol Med 2018; 104:105-110. [PMID: 30468913 DOI: 10.1016/j.compbiomed.2018.08.028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 08/28/2018] [Accepted: 08/28/2018] [Indexed: 11/21/2022]
Abstract
BACKGROUND As a functional imaging technology, magneto acoustic tomography (MAT) has broad application prospect in early tumor diagnosis and image monitoring during treatment. METHOD The influence on the acoustic field characteristics of the gradual change in conductivity was studied in magneto-acoustic tomography with current injection (MAT-CI) in this article. RESULT Theoretical analysis showed that the value of electro-acoustic conversion ratio (E-ACR) was different in different source frequencies under the same conductivity gradual-varying boundary. CONCLUSION The frequency characteristics of the acoustic pressure tend to shift towards the low frequency region. This conclusion provides a theoretical foundation for the MA signal detection and processing system optimization in the area of conductivity gradual-varying.
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Lee K, Woo EJ, Seo JK. A Fidelity-Embedded Regularization Method for Robust Electrical Impedance Tomography. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:1970-1977. [PMID: 29035213 DOI: 10.1109/tmi.2017.2762741] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Electrical impedance tomography (EIT) provides functional images of an electrical conductivity distribution inside the human body. Since the 1980s, many potential clinical applications have arisen using inexpensive portable EIT devices. EIT acquires multiple trans-impedance measurements across the body from an array of surface electrodes around a chosen imaging slice. The conductivity image reconstruction from the measured data is a fundamentally ill-posed inverse problem notoriously vulnerable to measurement noise and artifacts. Most available methods invert the ill-conditioned sensitivity or the Jacobian matrix using a regularized least-squares data-fitting technique. Their performances rely on the regularization parameter, which controls the trade-off between fidelity and robustness. For clinical applications of EIT, it would be desirable to develop a method achieving consistent performance over various uncertain data, regardless of the choice of the regularization parameter. Based on the analysis of the structure of the Jacobian matrix, we propose a fidelity-embedded regularization (FER) method and a motion artifact reduction filter. Incorporating the Jacobian matrix in the regularization process, the new FER method with the motion artifact reduction filter offers stable reconstructions of high-fidelity images from noisy data by taking a very large regularization parameter value. The proposed method showed practical merits in experimental studies of chest EIT imaging.
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Sajib SZK, Kwon OI, Kim HJ, Woo EJ. Electrodeless conductivity tensor imaging (CTI) using MRI: basic theory and animal experiments. Biomed Eng Lett 2018; 8:273-282. [PMID: 30603211 PMCID: PMC6208539 DOI: 10.1007/s13534-018-0066-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 04/12/2018] [Accepted: 04/12/2018] [Indexed: 11/26/2022] Open
Abstract
The electrical conductivity is a passive material property primarily determined by concentrations of charge carriers and their mobility. The macroscopic conductivity of a biological tissue at low frequency may exhibit anisotropy related with its structural directionality. When expressed as a tensor and properly quantified, the conductivity tensor can provide diagnostic information of numerous diseases. Imaging conductivity distributions inside the human body requires probing it by externally injecting conduction currents or inducing eddy currents. At low frequency, the Faraday induction is negligible and it has been necessary in most practical cases to inject currents through surface electrodes. Here we report a novel method to reconstruct conductivity tensor images using an MRI scanner without current injection. This electrodeless method of conductivity tensor imaging (CTI) utilizes B1 mapping to recover a high-frequency isotropic conductivity image which is influenced by contents in both extracellular and intracellular spaces. Multi-b diffusion weighted imaging is then utilized to extract the effects of the extracellular space and incorporate its directional structural property. Implementing the novel CTI method in a clinical MRI scanner, we reconstructed in vivo conductivity tensor images of canine brains. Depending on the details of the implementation, it may produce conductivity contrast images for conductivity weighted imaging (CWI). Clinical applications of CTI and CWI may include imaging of tumor, ischemia, inflammation, cirrhosis, and other diseases. CTI can provide patient-specific models for source imaging, transcranial dc stimulation, deep brain stimulation, and electroporation.
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Affiliation(s)
- Saurav Z. K. Sajib
- Department of Biomedical Engineering, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemun-gu, Seoul, 02447 Korea
| | - Oh In Kwon
- Department of Mathematics, Konkuk University, 120 Neungdongro, Gwangjin-gu, Seoul, 05029 Korea
| | - Hyung Joong Kim
- Department of Biomedical Engineering, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemun-gu, Seoul, 02447 Korea
| | - Eung Je Woo
- Department of Biomedical Engineering, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemun-gu, Seoul, 02447 Korea
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Zhou Y, Yu Z, Ma Q, Guo G, Tu J, Zhang D. Noninvasive Treatment-Efficacy Evaluation for HIFU Therapy Based on Magneto-Acousto-Electrical Tomography. IEEE Trans Biomed Eng 2018; 66:666-674. [PMID: 29993513 DOI: 10.1109/tbme.2018.2853594] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE As a novel noninvasive modality of oncotherapy or stroke treatment, high-intensity focused ultrasound (HIFU) has drawn more and more attention in the past decades. Whereas, real-time temperature monitoring and treatment-efficacy evaluation are still the key issues for HIFU therapy. METHODS Based on the temperature-conductivity relation of tissues with a sharp conductivity variation of irreversible thermocoagulation at 69 °C, a noninvasive method of treatment-efficacy evaluation for HIFU ablation using the magneto-acousto-electrical tomography (MAET) technology is theoretically studied. By applying the nonlinear Khokhlov-Zabolotskaya-Kuznetsov equation and Pennes equation, a cylindrical model is established to simulate the distributions of pressure, temperature, and conductivity with the consideration of harmonic components. RESULTS The MAET signals are simulated to analyze the characteristics of the peak amplitude and the axial interval of the two clusters generated by the conductivity boundary of HIFU ablation. CONCLUSION The axial interval can be used as the indictor to evaluate the size of HIFU ablation with the minimum axial width of one wavelength. SIGNIFICANCE The favorable results demonstrate the feasibility of real-time treatment-efficacy evaluation for HIFU therapy using the MAET technology and suggest potential applications in clinical practice.
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Park J, Youn JR, Song YS. Carbon Nanotube Embedded Nanostructure for Biometrics. ACS APPLIED MATERIALS & INTERFACES 2017; 9:44724-44731. [PMID: 29190074 DOI: 10.1021/acsami.7b15567] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Low electric energy loss is a very important problem to minimize the decay of transferred energy intensity due to impedance mismatch. This issue has been dealt with by adding an impedance matching layer at the interface between two media. A strategy was proposed to improve the charge transfer from the human body to a biometric device by using an impedance matching nanostructure. Nanocomposite pattern arrays were fabricated with shape memory polymer and carbon nanotubes. The shape recovery ability of the nanopatterns enhanced durability and sustainability of the structure. It was found that the composite nanopatterns improved the current transfer by two times compared with the nonpatterned composite sample. The underlying mechanism of the enhanced charge transport was understood by carrying out a numerical simulation. We anticipate that this study can provide a new pathway for developing advanced biometric devices with high sensitivity to biological information.
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Affiliation(s)
- Juhyuk Park
- Research Institute of Advanced Materials (RIAM), Department of Materials Science and Engineering, Seoul National University , Seoul 08826, Republic of Korea
| | - Jae Ryoun Youn
- Research Institute of Advanced Materials (RIAM), Department of Materials Science and Engineering, Seoul National University , Seoul 08826, Republic of Korea
| | - Young Seok Song
- Department of Fiber System Engineering, Dankook University , Gyeonggi Do 16890, Republic of Korea
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Liu J, Shao Q, Wang Y, Adriany G, Bischof J, Van de Moortele PF, He B. In vivo imaging of electrical properties of an animal tumor model with an 8-channel transceiver array at 7 T using electrical properties tomography. Magn Reson Med 2017; 78:2157-2169. [PMID: 28112824 PMCID: PMC5522781 DOI: 10.1002/mrm.26609] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 12/20/2016] [Accepted: 12/22/2016] [Indexed: 02/02/2023]
Abstract
PURPOSE To develop and evaluate a technique for imaging electrical properties ((EPs), conductivity and permittivity) of an animal tumor model in vivo using MRI. METHODS Electrical properties were reconstructed from the calculated EP gradient, which was derived using two sets of measured transmit B1 magnitude and relative phase maps with the sample and radiofrequency (RF) coil oriented in the positive and negative z-directions, respectively. An eight-channel transceiver microstrip array RF coil fitting the size of the animal was developed for generating and mapping B1 fields to reconstruct EPs. The technique was evaluated at 7 tesla using a physical phantom and in vivo on two Copenhagen rats with subcutaneously implanted AT-1 rat prostate cancer on a hind limb. RESULTS The reconstructed EPs in the phantom experiment was in good agreement with the target EP map determined by a dielectric probe. Reconstructed conductivity map of the animals revealed the boundary between tumor and healthy tissue consistent with the boundary indicated by T1 -weighted MRI. CONCLUSION A technique for imaging EP of an animal tumor model using MRI has been developed with high sensitivity, accuracy, and resolution, as demonstrated in the phantom experiment. Further animal experiments are needed to demonstrate its translational value for tumor diagnosis. Magn Reson Med 78:2157-2169, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jiaen Liu
- Department of Biomedical Engineering, University of
Minnesota, Minneapolis, MN, U.S
| | - Qi Shao
- Department of Biomedical Engineering, University of
Minnesota, Minneapolis, MN, U.S
| | - Yicun Wang
- Department of Biomedical Engineering, University of
Minnesota, Minneapolis, MN, U.S
| | - Gregor Adriany
- Center for Magnetic Resonance Research, University of
Minnesota, Minneapolis, MN, U.S
| | - John Bischof
- Department of Biomedical Engineering, University of
Minnesota, Minneapolis, MN, U.S
- Department of Mechanical Engineering, University of
Minnesota, Minneapolis, Minnesota, MN, U.S
- Institute for Engineering in Medicine, University of
Minnesota, Minneapolis, MN, U.S
| | | | - Bin He
- Department of Biomedical Engineering, University of
Minnesota, Minneapolis, MN, U.S
- Institute for Engineering in Medicine, University of
Minnesota, Minneapolis, MN, U.S
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Mandija S, Sbrizzi A, Katscher U, Luijten PR, van den Berg CAT. Error analysis of helmholtz-based MR-electrical properties tomography. Magn Reson Med 2017; 80:90-100. [PMID: 29144031 DOI: 10.1002/mrm.27004] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 10/19/2017] [Accepted: 10/21/2017] [Indexed: 11/10/2022]
Abstract
PURPOSE MR electrical properties tomography (MR-EPT) aims to measure tissue electrical properties by computing spatial derivatives of measured B1+ data. This computation is very sensitive to spatial fluctuations caused, for example, by noise and Gibbs ringing. In this work, the error arising from the computation of spatial derivatives using finite difference kernels (FD error) has been investigated. In relation to this FD error, it has also been investigated whether mitigation strategies such as Gibbs ringing correction and Gaussian apodization can be beneficial for conductivity reconstructions. METHODS Conductivity reconstructions were performed on a phantom (by means of simulations and MR measurements at 3T) and on a human brain model. The accuracy was evaluated as a function of image resolution, FD kernel size, k-space windowing, and signal-to-noise ratio. The impact of mitigation strategies was also investigated. RESULTS The adopted small FD kernel is highly sensitive to spatial fluctuations, whereas the large FD kernel is more noise-robust. However, large FD kernels lead to extended numerical boundary error propagation, which severely hampers the MR-EPT reconstruction accuracy for highly spatially convoluted tissue structures such as the human brain. Mitigation strategies slightly improve the accuracy of conductivity reconstructions. For the adopted derivative kernels and the investigated scenario, MR-EPT conductivity reconstructions show low accuracy: less than 37% of the voxels have a relative error lower than 30%. CONCLUSION The numerical error introduced by the computation of spatial derivatives using FD kernels is one of the major causes of limited accuracy in Helmholtz-based MR-EPT reconstructions. Magn Reson Med 80:90-100, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Stefano Mandija
- Center For Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Alessandro Sbrizzi
- Center For Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Peter R Luijten
- Center For Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands.,Department of Radiology, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cornelis A T van den Berg
- Center For Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands.,Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
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35
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Liu J, Wang Y, Katscher U, He B. Electrical Properties Tomography Based on $B_{{1}}$ Maps in MRI: Principles, Applications, and Challenges. IEEE Trans Biomed Eng 2017; 64:2515-2530. [PMID: 28829299 PMCID: PMC5675043 DOI: 10.1109/tbme.2017.2725140] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE The purpose is to provide a comprehensive review of the electrical properties tomography (EPT) technique, which was introduced to image the electrical properties (EPs) of tissue noninvasively by exploiting the measured field data of MRI. METHODS We reviewed the principle of EPT, reconstruction methods, biomedical applications such as tumor imaging, and existing challenges. As a key application of EPT, the estimation of specific absorption rate (SAR) due to MRI was discussed in the background of elevated risk of tissue heating at high field. RESULTS AND CONCLUSION Since the originally proposed local, homogeneous Helmholtz equation-based reconstruction algorithm, advanced EPT algorithms have emerged to address the challenges of EPT, including reconstruction error near tissue boundaries, noise sensitivity, inaccurate phase estimation, and elimination of the unmeasurable component, along with demonstrations of in vivo experiments. EPT techniques have been applied to investigate EPs of both healthy and pathological tissues in vivo and factors contributing to various EP value, including sodium, water content, etc. More studies are anticipated to consolidate the current findings. EPT-based subject-specific SAR estimation has led to in vivo demonstration of its feasibility and prediction of temperature increase of phantom during MRI scans merely using measured data. SIGNIFICANCE EPT has the advantage of high resolution and practical feasibility in a clinical setup for imaging the biomedically interesting EPs of tissue in the radiofrequency range. EPT-based SAR estimation is another promising topic for predicting tissue heating of individual subjects during a specific MRI scan.
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Affiliation(s)
- Jiaen Liu
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Yicun Wang
- Department of Biomedical Engineering, University of Minnesota, Minnesota, 55455, USA
| | | | - Bin He
- Department of Biomedical Engineering and Institute for Engineering in Medicine, University of Minnesota, Minnesota, 55455, USA
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Hao Z, Yue S, Sun B, Wang H. Optimal distance of multi-plane sensor in three-dimensional electrical impedance tomography. Comput Assist Surg (Abingdon) 2017; 22:326-338. [DOI: 10.1080/24699322.2017.1389412] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Affiliation(s)
- Zhenhua Hao
- School of Electrical and Information Engineering, Tianjin University, Tianjin, China
| | - Shihong Yue
- School of Electrical and Information Engineering, Tianjin University, Tianjin, China
| | - Benyuan Sun
- School of Electrical and Information Engineering, Tianjin University, Tianjin, China
| | - Huaxiang Wang
- School of Electrical and Information Engineering, Tianjin University, Tianjin, China
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Ghalichi E, Güneri Gençer N. Theoretical limits to sensitivity and resolution in magneto-acousto-electrical tomography. Phys Med Biol 2017; 62:8025-8040. [DOI: 10.1088/1361-6560/aa82a1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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38
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Faulkner M, Jehl M, Aristovich K, Avery J, Witkowska-Wrobel A, Holder D. Optimisation of current injection protocol based on a region of interest. Physiol Meas 2017; 38:1158-1175. [DOI: 10.1088/1361-6579/aa69d7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Elsaid NMH, Nachman AI, Ma W, DeMonte TP, Joy MLG. The Impact of Anisotropy on the Accuracy of Conductivity Imaging: A Quantitative Validation Study. IEEE TRANSACTIONS ON MEDICAL IMAGING 2017; 36:507-517. [PMID: 28113393 DOI: 10.1109/tmi.2016.2617873] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present a quantitative validation study to assess the accuracy of low-frequency conductivity imaging methods, based on a testing current measured using Current Density Imaging (CDI). We tested the proposed procedure to study the influence of tissue anisotropy on the accuracy of conductivity reconstruction methods, using a finite element model of anisotropic brain tissue. Simulations were carried out for three different levels of tissue anisotropy to compare the results obtained by our recently developed anisotropic conductivity method with those obtained by our well-established conductivity method that assumes isotropic conductivity. The validation results clearly show that the conductivity imaging method which takes into account tissue anisotropy yields significantly superior accuracy.
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Avery J, Dowrick T, Faulkner M, Goren N, Holder D. A Versatile and Reproducible Multi-Frequency Electrical Impedance Tomography System. SENSORS (BASEL, SWITZERLAND) 2017; 17:E280. [PMID: 28146122 PMCID: PMC5336119 DOI: 10.3390/s17020280] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 01/25/2017] [Indexed: 11/16/2022]
Abstract
A highly versatile Electrical Impedance Tomography (EIT) system, nicknamed the ScouseTom, has been developed. The system allows control over current amplitude, frequency, number of electrodes, injection protocol and data processing. Current is injected using a Keithley 6221 current source, and voltages are recorded with a 24-bit EEG system with minimum bandwidth of 3.2 kHz. Custom PCBs interface with a PC to control the measurement process, electrode addressing and triggering of external stimuli. The performance of the system was characterised using resistor phantoms to represent human scalp recordings, with an SNR of 77.5 dB, stable across a four hour recording and 20 Hz to 20 kHz. In studies of both haeomorrhage using scalp electrodes, and evoked activity using epicortical electrode mats in rats, it was possible to reconstruct images matching established literature at known areas of onset. Data collected using scalp electrode in humans matched known tissue impedance spectra and was stable over frequency. The experimental procedure is software controlled and is readily adaptable to new paradigms. Where possible, commercial or open-source components were used, to minimise the complexity in reproduction. The hardware designs and software for the system have been released under an open source licence, encouraging contributions and allowing for rapid replication.
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Affiliation(s)
- James Avery
- Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK.
| | - Thomas Dowrick
- Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK.
| | - Mayo Faulkner
- Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK.
| | - Nir Goren
- Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK.
| | - David Holder
- Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK.
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Schullcke B, Gong B, Krueger-Ziolek S, Tawhai M, Adler A, Mueller-Lisse U, Moeller K. Lobe based image reconstruction in Electrical Impedance Tomography. Med Phys 2017; 44:426-436. [PMID: 28121374 DOI: 10.1002/mp.12038] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 09/22/2016] [Accepted: 11/25/2016] [Indexed: 11/06/2022] Open
Abstract
PURPOSE Electrical Impedance Tomography (EIT) is an imaging modality used to generate two-dimensional cross-sectional images representing impedance change in the thorax. The impedance of lung tissue changes with change in air content of the lungs; hence, EIT can be used to examine regional lung ventilation in patients with abnormal lungs. In lung EIT, electrodes are attached around the circumference of the thorax to inject small alternating currents and measure resulting voltages. In contrast to X-ray computed tomography (CT), EIT images do not depict a thorax slice of well defined thickness, but instead visualize a lens-shaped region around the electrode plane, which results from diffuse current propagation in the thorax. Usually, this is considered a drawback, since image interpretation is impeded if 'off-plane' conductivity changes are projected onto the reconstructed two-dimensional image. In this paper we describe an approach that takes advantage of current propagation below and above the electrode plane. The approach enables estimation of the individual conductivity change in each lung lobe from boundary voltage measurements. This could be used to monitor disease progression in patients with obstructive lung diseases, such as chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF) and to obtain a more comprehensive insight into the pathophysiology of the lung. METHODS Electrode voltages resulting from different conductivities in each lung lobe were simulated utilizing a realistic 3D finite element model (FEM) of the human thorax and the lungs. Overall 200 different patterns of conductivity change were simulated. A 'lobe reconstruction' algorithm was developed, applying patient-specific anatomical information in the reconstruction process. A standard EIT image reconstruction algorithm and the proposed 'lobe reconstruction' algorithm were used to estimate conductivity change in the lobes. The agreement between simulated and reconstructed conductivity change in particular lobes were compared using Bland-Altman plots, correlation plots and linear regression. To test the applicability of the approach in a realistic scenario, EIT measurements of a patient suffering from cystic fibrosis (CF) were carried out. RESULTS Conductivity changes in each lobe generate specific patterns of voltage change. These can be used to estimate the conductivity change in lobes from measured boundary voltage. The correlation coefficient between simulated and reconstructed conductivity change in particular lobes is r > 0.89 for all lobes. Unknown position of the electrode plane leads to over- or underestimation of reconstructed conductivity change. Slight mismatches (± 5% of the forward model height) between the actual position of the electrode plane and the position used in the reconstruction model lead to regression coefficients of 0.7 to 1.3 between simulated and reconstructed conductivity change in the lobes. CONCLUSION The presented approach enhances common reconstruction methods by providing information about anatomically assignable units and thus facilitates image interpretation, since impedance change and thus ventilation of each lobe is directly determined in the reconstructions.
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Affiliation(s)
- Benjamin Schullcke
- Institute of Technical Medicine, Furtwangen University, 78045, VS-Schwenningen, Germany.,Department of Radiology, University of Munich, 80336, Munich, Germany
| | - Bo Gong
- Institute of Technical Medicine, Furtwangen University, 78045, VS-Schwenningen, Germany.,Department of Radiology, University of Munich, 80336, Munich, Germany
| | - Sabine Krueger-Ziolek
- Institute of Technical Medicine, Furtwangen University, 78045, VS-Schwenningen, Germany.,Department of Radiology, University of Munich, 80336, Munich, Germany
| | - Merryn Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, 1010, New Zealand
| | - Andy Adler
- Systems and Computer Engineering, Carlton University, Ottawa, ON, K1S 5B6, Canada
| | | | - Knut Moeller
- Institute of Technical Medicine, Furtwangen University, 78045, VS-Schwenningen, Germany
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Zhou Y, Ma Q, Guo G, Tu J, Zhang D. Magneto-acousto-electrical measurement based electrical conductivity reconstruction for tissues. IEEE Trans Biomed Eng 2017; 65:1086-1094. [DOI: 10.1109/tbme.2017.2740924] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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On-site Rapid Diagnosis of Intracranial Hematoma using Portable Multi-slice Microwave Imaging System. Sci Rep 2016; 6:37620. [PMID: 27897197 PMCID: PMC5126641 DOI: 10.1038/srep37620] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 11/01/2016] [Indexed: 11/28/2022] Open
Abstract
Rapid, on-the-spot diagnostic and monitoring systems are vital for the survival of patients with intracranial hematoma, as their conditions drastically deteriorate with time. To address the limited accessibility, high costs and static structure of currently used MRI and CT scanners, a portable non-invasive multi-slice microwave imaging system is presented for accurate 3D localization of hematoma inside human head. This diagnostic system provides fast data acquisition and imaging compared to the existing systems by means of a compact array of low-profile, unidirectional antennas with wideband operation. The 3D printed low-cost and portable system can be installed in an ambulance for rapid on-site diagnosis by paramedics. In this paper, the multi-slice head imaging system’s operating principle is numerically analysed and experimentally validated on realistic head phantoms. Quantitative analyses demonstrate that the multi-slice head imaging system is able to generate better quality reconstructed images providing 70% higher average signal to clutter ratio, 25% enhanced maximum signal to clutter ratio and with around 60% hematoma target localization compared to the previous head imaging systems. Nevertheless, numerical and experimental results demonstrate that previous reported 2D imaging systems are vulnerable to localization error, which is overcome in the presented multi-slice 3D imaging system. The non-ionizing system, which uses safe levels of very low microwave power, is also tested on human subjects. Results of realistic phantom and subjects demonstrate the feasibility of the system in future preclinical trials.
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Zengin R, Gençer NG. Lorentz force electrical impedance tomography using magnetic field measurements. Phys Med Biol 2016; 61:5887-905. [DOI: 10.1088/0031-9155/61/16/5887] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Wei KHY, Qiu CH, Primrose K. Super-sensing technology: industrial applications and future challenges of electrical tomography. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0328. [PMID: 27185967 DOI: 10.1098/rsta.2015.0328] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/04/2016] [Indexed: 06/05/2023]
Abstract
Electrical tomography is a relatively new imaging technique that can image the distribution of the passive electrical properties of an object. Since electrical tomography technology was proposed in the 1980s, the technique has evolved rapidly because of its low cost, easy scale-up and non-invasive features. The technique itself can be sensitive to all passive electrical properties, such as conductivity, permittivity and permeability. Hence, it has a huge potential to be applied in many applications. Owing to its ill-posed nature and low image resolution, electrical tomography attracts more attention in industrial fields than biomedical fields. In the past decades, there have been many research developments and industrial implementations of electrical tomography; nevertheless, the awareness of this technology in industrial sectors is still one of the biggest limitations for technology implementation. In this paper, the authors have summarized several representative applications that use electrical tomography. Some of the current tomography research activities will also be discussed. This article is part of the themed issue 'Supersensing through industrial process tomography'.
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Affiliation(s)
- Kent Hsin-Yu Wei
- Research and Development Department, Industrial Tomography Systems Plc, 85 Quay Street, Manchester M3 3JZ, UK
| | - Chang-Hua Qiu
- Research and Development Department, Industrial Tomography Systems Plc, 85 Quay Street, Manchester M3 3JZ, UK
| | - Ken Primrose
- Research and Development Department, Industrial Tomography Systems Plc, 85 Quay Street, Manchester M3 3JZ, UK
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Wagenaar J, Adler A. Electrical impedance tomography in 3D using two electrode planes: characterization and evaluation. Physiol Meas 2016; 37:922-37. [DOI: 10.1088/0967-3334/37/6/922] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Structural-functional lung imaging using a combined CT-EIT and a Discrete Cosine Transformation reconstruction method. Sci Rep 2016; 6:25951. [PMID: 27181695 PMCID: PMC4867600 DOI: 10.1038/srep25951] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 04/20/2016] [Indexed: 12/14/2022] Open
Abstract
Lung EIT is a functional imaging method that utilizes electrical currents to reconstruct images of conductivity changes inside the thorax. This technique is radiation free and applicable at the bedside, but lacks of spatial resolution compared to morphological imaging methods such as X-ray computed tomography (CT). In this article we describe an approach for EIT image reconstruction using morphologic information obtained from other structural imaging modalities. This leads to recon- structed images of lung ventilation that can easily be superimposed with structural CT or MRI images, which facilitates image interpretation. The approach is based on a Discrete Cosine Transformation (DCT) of an image of the considered transversal thorax slice. The use of DCT enables reduction of the dimensionality of the reconstruction and ensures that only conductivity changes of the lungs are reconstructed and displayed. The DCT based approach is well suited to fuse morphological image information with functional lung imaging at low computational costs. Results on simulated data indicate that this approach preserves the morphological structures of the lungs and avoids blurring of the solution. Images from patient measurements reveal the capabilities of the method and demonstrate benefits in possible applications.
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Bera TK, Nagaraju J, Lubineau G. Electrical impedance spectroscopy (EIS)-based evaluation of biological tissue phantoms to study multifrequency electrical impedance tomography (Mf-EIT) systems. J Vis (Tokyo) 2016. [DOI: 10.1007/s12650-016-0351-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Michel E, Hernandez D, Lee SY. Electrical conductivity and permittivity maps of brain tissues derived from water content based on T 1 -weighted acquisition. Magn Reson Med 2016; 77:1094-1103. [PMID: 26946979 DOI: 10.1002/mrm.26193] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 01/15/2016] [Accepted: 02/10/2016] [Indexed: 12/12/2022]
Abstract
PURPOSE To develop an electrical properties tomography (EPT) technique that can provide in vivo electrical conductivity and permittivity images of biological tissue without performing complex-valued radiofrequency field measurements. THEORY AND METHODS Electrical conductivity and permittivity images are modeled as a monotonic function of tissues' water content (W) under the principle of Maxwell's mixture theory. Water content maps are estimated from two spin-echo images having different repetition times (TRs). For the modeling functions, physically measured parameters (electrical properties, water content, and T1 ) of brain cerebrospinal fluid (CSF), gray matter, and white matter are used as landmark literature references. The formulations are validated by a developed electrolyte-protein phantom and by human brain studies at 3 Tesla (T). RESULTS The electrical properties (EPs) of the phantom estimated by the proposed method match well with the values measured on the bench. The conductivity and permittivity maps from all experiments show uncompromised spatial resolution without boundary artifacts and higher contrast when compared with water content maps. CONCLUSIONS Human brain and phantom EP images suggest that water content is a dominating factor in determining the electrical properties of tissues. Despite possible literature inaccuracies, the proposed method offers EP maps that can provide complementary information to current approaches, to facilitate EPT scans in clinical applications. Magn Reson Med 77:1094-1103, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Eric Michel
- Department of Biomedical Engineering, Kyung Hee University, Yongin, Korea
| | - Daniel Hernandez
- Department of Biomedical Engineering, Kyung Hee University, Yongin, Korea
| | - Soo Yeol Lee
- Department of Biomedical Engineering, Kyung Hee University, Yongin, Korea
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