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Jung YH, Lee HY, Lee BK, Choi BK, Kim TH, Kim JW, Kim HC, Kim HJ, Jeung KW. Feasibility of Magnetic Resonance-Based Conductivity Imaging as a Tool to Estimate the Severity of Hypoxic-Ischemic Brain Injury in the First Hours After Cardiac Arrest. Neurocrit Care 2024; 40:538-550. [PMID: 37353670 DOI: 10.1007/s12028-023-01776-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 06/05/2023] [Indexed: 06/25/2023]
Abstract
BACKGROUND Early identification of the severity of hypoxic-ischemic brain injury (HIBI) after cardiac arrest can be used to help plan appropriate subsequent therapy. We evaluated whether conductivity of cerebral tissue measured using magnetic resonance-based conductivity imaging (MRCI), which provides contrast derived from the concentration and mobility of ions within the imaged tissue, can reflect the severity of HIBI in the early hours after cardiac arrest. METHODS Fourteen minipigs were resuscitated after 5 min or 12 min of untreated cardiac arrest. MRCI was performed at baseline and at 1 h and 3.5 h after return of spontaneous circulation (ROSC). RESULTS In both groups, the conductivity of cerebral tissue significantly increased at 1 h after ROSC compared with that at baseline (P = 0.031 and 0.016 in the 5-min and 12-min groups, respectively). The increase was greater in the 12-min group, resulting in significantly higher conductivity values in the 12-min group (P = 0.030). At 3.5 h after ROSC, the conductivity of cerebral tissue in the 12-min group remained increased (P = 0.022), whereas that in the 5-min group returned to its baseline level. CONCLUSIONS The conductivity of cerebral tissue was increased in the first hours after ROSC, and the increase was more prominent and lasted longer in the 12-min group than in the 5-min group. Our findings suggest the promising potential of MRCI as a tool to estimate the severity of HIBI in the early hours after cardiac arrest.
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Affiliation(s)
- Yong Hun Jung
- Department of Emergency Medicine, Chonnam National University Hospital, 42 Jebong-ro, Donggu, Gwangju, 61469, Republic of Korea
- Department of Emergency Medicine, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Hyoung Youn Lee
- Trauma Center, Chonnam National University Hospital, Gwangju, Republic of Korea
| | - Byung Kook Lee
- Department of Emergency Medicine, Chonnam National University Hospital, 42 Jebong-ro, Donggu, Gwangju, 61469, Republic of Korea
- Department of Emergency Medicine, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Bup Kyung Choi
- Medical Science Research Institute, Kyung Hee University Hospital, Seoul, Republic of Korea
| | - Tae-Hoon Kim
- Medical Convergence Research Center, Wonkwang University, Iksan, Republic of Korea
| | - Jin Woong Kim
- Department of Radiology, Chosun University Hospital, Gwangju, Republic of Korea
| | - Hyun Chul Kim
- Department of Radiology, Chosun University Hospital, Gwangju, Republic of Korea
| | - Hyung Joong Kim
- Medical Science Research Institute, Kyung Hee University Hospital, Seoul, Republic of Korea
| | - Kyung Woon Jeung
- Department of Emergency Medicine, Chonnam National University Hospital, 42 Jebong-ro, Donggu, Gwangju, 61469, Republic of Korea.
- Department of Emergency Medicine, Chonnam National University Medical School, Gwangju, Republic of Korea.
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SNR-Enhanced, Rapid Electrical Conductivity Mapping Using Echo-Shifted MRI. Tomography 2022; 8:376-388. [PMID: 35202196 PMCID: PMC8874775 DOI: 10.3390/tomography8010031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/14/2022] [Accepted: 01/29/2022] [Indexed: 11/17/2022] Open
Abstract
Magnetic resonance electrical impedance tomography (MREIT) permits high-spatial resolution electrical conductivity mapping of biological tissues, and its quantification accuracy hinges on the signal-to-noise ratio (SNR) of the current-induced magnetic flux density (Bz). The purpose of this work was to achieve Bz SNR-enhanced rapid conductivity imaging by developing an echo-shifted steady-state incoherent imaging-based MREIT technique. In the proposed pulse sequence, the free-induction-decay signal is shifted in time over multiple imaging slices, and as a result is exposed to a plurality of injecting current pulses before forming an echo. Thus, the proposed multi-slice echo-shifting strategy allows a high SNR for Bz for a given number of current injections. However, with increasing the time of echo formation, the Bz SNR will also be compromised by T2*-related signal loss. Hence, numerical simulations were performed to evaluate the relationship between the echo-shifting and the Bz SNR, and subsequently to determine the optimal imaging parameters. Experimental studies were conducted to evaluate the effectiveness of the proposed method over conventional spin-echo-based MREIT. Compared with the reference spin-echo MREIT, the proposed echo-shifting-based method improves the efficiency in both data acquisition and current injection while retaining the accuracy of conductivity quantification. The results suggest the feasibility of the proposed MREIT method as a practical means for conductivity mapping.
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Chauhan M, Sadleir R. Phantom Construction and Equipment Configurations for Characterizing Electrical Properties Using MRI. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1380:83-110. [PMID: 36306095 DOI: 10.1007/978-3-031-03873-0_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Phantom objects are commonly employed in MRI systems as stable substitutes for biological tissues to ensure systems for measuring images are operating correctly and safely. For magnetic resonance electrical impedance tomography (MREIT) and magnetic resonance electrical property tomography (MREPT), conductivity or permittivity phantoms play an important role in checking MRI pulse sequences, MREIT equipment performance, and algorithm validation. The construction of these phantoms is explained in this chapter. In the first part, materials used for phantom construction are introduced. Ingredients for modifying the electromagnetic properties and relaxation times are presented, and the advantages and disadvantages of aqueous, gel, and hybrid conductivity phantoms are explained. The devices and methods used to confirm phantom electromagnetic properties are explained. Next, different types of MREIT electrode materials and the constant current sources used for MREIT studies are discussed. In the last section, we present the results of previous MREIT and MREPT studies.
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Affiliation(s)
- Munish Chauhan
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, USA
| | - Rosalind Sadleir
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, USA.
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Amouzandeh G, Mentink-Vigier F, Helsper S, Bagdasarian FA, Rosenberg JT, Grant SC. Magnetic resonance electrical property mapping at 21.1 T: a study of conductivity and permittivity in phantoms, ex vivo tissue and in vivo ischemia. Phys Med Biol 2020; 65:055007. [PMID: 31307020 PMCID: PMC7223161 DOI: 10.1088/1361-6560/ab3259] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Electrical properties (EP), namely conductivity and permittivity, can provide endogenous contrast for tissue characterization. Using electrical property tomography (EPT), maps of EP can be generated from conventional MRI data. This report investigates the feasibility and accuracy of EPT at 21.1 T for multiple RF coils and modes of operation using phantoms. Additionally, it demonstrates the EP of the in vivo rat brain with and without ischemia. Helmholtz-based EPT was implemented in its Full-form, which demands the complex [Formula: see text] field, and a simplified form requiring either just the [Formula: see text] field phase for conductivity or the [Formula: see text] field magnitude for permittivity. Experiments were conducted at 21.1 T using birdcage and saddle coils operated in linear or quadrature transceive mode, respectively. EPT approaches were evaluated using a phantom, ex and in vivo Sprague-Dawley rats under naïve conditions and ischemic stroke via transient middle cerebral artery occlusion. Different conductivity reconstruction approaches applied to the phantom displayed average errors of 12%-73% to the target acquired from dielectric probe measurements. Permittivity reconstructions showed higher agreement and an average 3%-8% error to the target depending on reconstruction approach. Conductivity and permittivity of ex and in vivo rodent brain were measured. Elevated EP in the ischemia region correlated with the increased sodium content and the influx of water intracellularly following ischemia in the lesion were detected. The Full-form technique generated from the linear birdcage provided the best accuracy for EP of the phantom. Phase-based conductivity and magnitude-based permittivity mapping provided reasonable estimates but also demonstrated the limitations of Helmholtz-based EPT at 21.1 T. Permittivity reconstruction was improved significantly over lower fields, suggesting a novel metric for in vivo brain studies. EPT applied to ischemic rat brain proved sensitivity to physiological changes, motivating the future application of more advanced reconstruction approaches.
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Affiliation(s)
- Ghoncheh Amouzandeh
- Department of Physics, Florida State University, Tallahassee, FL, USA
- The National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
| | | | - Shannon Helsper
- The National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
- Department of Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, USA
| | - F. Andrew Bagdasarian
- The National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
- Department of Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, USA
| | - Jens T. Rosenberg
- The National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
| | - Samuel C. Grant
- The National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
- Department of Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, USA
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Minhas AS, Chauhan M, Fu F, Sadleir R. Evaluation of magnetohydrodynamic effects in magnetic resonance electrical impedance tomography at ultra-high magnetic fields. Magn Reson Med 2018; 81:2264-2276. [PMID: 30450638 DOI: 10.1002/mrm.27534] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 08/25/2018] [Accepted: 08/27/2018] [Indexed: 11/09/2022]
Abstract
PURPOSE Artifacts observed in experimental magnetic resonance electrical impedance tomography images were hypothesized to be because of magnetohydrodynamic (MHD) effects. THEORY AND METHODS Simulations of MREIT acquisition in the presence of MHD and electrical current flow were performed to confirm findings. Laminar flow and (electrostatic) electrical conduction equations were bidirectionally coupled via Lorentz force equations, and finite element simulations were performed to predict flow velocity as a function of time. Gradient sequences used in spin-echo and gradient echo acquisitions were used to calculate overall effects on MR phase images for different electrical current application or phase-encoding directions. RESULTS Calculated and experimental phase images agreed relatively well, both qualitatively and quantitatively, with some exceptions. Refocusing pulses in spin echo sequences did not appear to affect experimental phase images. CONCLUSION MHD effects were confirmed as the cause of observed experimental phase changes in MREIT images obtained at high fields. These findings may have implications for quantitative measurement of viscosity using MRI techniques. Methods developed here may be also important in studies of safety and in vivo artifacts observed in high field MRI systems.
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Affiliation(s)
- Atul S Minhas
- Faculty of Science and Engineering, School of Engineering, Macquarie University, Sydney, NSW, Australia
| | - Munish Chauhan
- School of Biological and Health Systems Engineering, Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, Arizona
| | - Fanrui Fu
- School of Biological and Health Systems Engineering, Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, Arizona
| | - Rosalind Sadleir
- School of Biological and Health Systems Engineering, Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, Arizona
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Kim DH, Chauhan M, Kim MO, Jeong WC, Kim HJ, Sersa I, Kwon OI, Woo EJ. Frequency-dependent conductivity contrast for tissue characterization using a dual-frequency range conductivity mapping magnetic resonance method. IEEE TRANSACTIONS ON MEDICAL IMAGING 2015; 34:507-513. [PMID: 25312916 DOI: 10.1109/tmi.2014.2361689] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Electrical conductivities of biological tissues show frequency-dependent behaviors, and these values at different frequencies may provide clinically useful diagnostic information. MR-based tissue property mapping techniques such as magnetic resonance electrical impedance tomography (MREIT) and magnetic resonance electrical property tomography (MREPT) are widely used and provide unique conductivity contrast information over different frequency ranges. Recently, a new method for data acquisition and reconstruction for low- and high-frequency conductivity images from a single MR scan was proposed. In this study, we applied this simultaneous dual-frequency range conductivity mapping MR method to evaluate its utility in a designed phantom and two in vivo animal disease models. Magnetic flux density and B(1)(+) phase map for dual-frequency conductivity images were acquired using a modified spin-echo pulse sequence. Low-frequency conductivity was reconstructed from MREIT data by the projected current density method, while high-frequency conductivity was reconstructed from MREPT data by B(1)(+) mapping. Two different conductivity phantoms comprising varying ion concentrations separated by insulating films with or without holes were used to study the contrast mechanism of the frequency-dependent conductivities related to ion concentration and mobility. Canine brain abscess and ischemia were used as in vivo models to evaluate the capability of the proposed method to identify new electrical properties-based contrast at two different frequencies. The simultaneous dual-frequency range conductivity mapping MR method provides unique contrast information related to the concentration and mobility of ions inside tissues. This method has potential to monitor dynamic changes of the state of disease.
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Jin Keun Seo, Eung Je Woo. Electrical Tissue Property Imaging at Low Frequency Using MREIT. IEEE Trans Biomed Eng 2014; 61:1390-9. [DOI: 10.1109/tbme.2014.2298859] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Jeong WC, Meng ZJ, Kim HJ, Kwon OI, Woo EJ. Experimental validations of in vivo human musculoskeletal tissue conductivity images using MR-based electrical impedance tomography. Bioelectromagnetics 2014; 35:363-72. [DOI: 10.1002/bem.21852] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 02/26/2014] [Indexed: 01/19/2023]
Affiliation(s)
- Woo Chul Jeong
- Department of Biomedical Engineering; Kyung Hee University; Yongin Korea
| | - Zi Jun Meng
- Department of Biomedical Engineering; Kyung Hee University; Yongin Korea
| | - Hyung Joong Kim
- Department of Biomedical Engineering; Kyung Hee University; Yongin Korea
| | - Oh In Kwon
- Department of Mathematics; Konkuk University; Seoul Korea
| | - Eung Je Woo
- Department of Biomedical Engineering; Kyung Hee University; Yongin Korea
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Kwon OI, Jeong WC, K Sajib SZ, Kim HJ, Woo EJ, Oh TI. Reconstruction of dual-frequency conductivity by optimization of phase map in MREIT and MREPT. Biomed Eng Online 2014; 13:24. [PMID: 24607262 PMCID: PMC3995946 DOI: 10.1186/1475-925x-13-24] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 02/25/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The spectroscopic conductivity distribution of tissue can help to explain physiological and pathological status. Dual frequency conductivity imaging by combining Magnetic Resonance Electrical Property Tomography (MREPT) and Magnetic Resonance Electrical Impedance Tomography (MREIT) has been recently proposed. MREIT can provide internal conductivity distributions at low frequency (below 1 kHz) induced by an external injecting current. While MREPT can provide conductivity at the Larmor frequency related to the strength of the magnetic field. Despite this potential to describe the membrane properties using spectral information, MREPT and MREIT techniques currently suffer from weak signals and noise amplification as they both reply on differentiation of measured phase data. METHODS We proposed a method to optimize the measured phase signal by finding weighting factors according to the echo signal for MREPT and MREIT using the ICNE (Injected current nonlinear encoding) multi-echo pulse sequence. Our target weights are chosen to minimize the measured noise. The noise standard deviations were precisely analyzed for the optimally weighted magnetic flux density and the phase term of the positive-rotating magnetic field. To enhance the quality of dual-frequency conductivity images, we applied the denoising method based on the reaction-diffusion equation with the estimated noise standard deviations. A real experiment was performed with a hollow cylindrical object made of thin insulating film with holes to control the apparent conductivity using ion mobility and an agarose gel cylinder wrapped in an insulating film without holes to show different spectroscopic conductivities. RESULTS The ability to image different conductivity characteristics in MREPT and MREIT from a single MR scan was shown by including the two objects with different spectroscopic conductivities. Using the six echo signals, we computed the optimized weighting factors for each echo. The qualities of conductivity images for MREPT and MREIT were improved by optimization of the phase map. The proposed method effectively reduced the random noise artifacts for both MREIT and MREPT. CONCLUSION We enhanced the dual conductivity images using the optimally weighted magnetic flux density and the phase term of positive-rotating magnetic field based on the analysis of the noise standard deviations and applying the optimization and denoising methods.
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Affiliation(s)
- Oh In Kwon
- Department of Mathematics, Konkuk University, 143-701 Seoul, Korea
| | - Woo Chul Jeong
- Department of Biomedical Engineering and Impedance Imaging Research Center, Kyung Hee University, 446-701 Yongin, Korea
| | - Saurav Z K Sajib
- Department of Biomedical Engineering and Impedance Imaging Research Center, Kyung Hee University, 446-701 Yongin, Korea
| | - Hyung Joong Kim
- Department of Biomedical Engineering and Impedance Imaging Research Center, Kyung Hee University, 446-701 Yongin, Korea
| | - Eung Je Woo
- Department of Biomedical Engineering and Impedance Imaging Research Center, Kyung Hee University, 446-701 Yongin, Korea
| | - Tong In Oh
- Department of Biomedical Engineering and Impedance Imaging Research Center, Kyung Hee University, 446-701 Yongin, Korea
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Oh TI, Kim HJ, Jeong WC, Chauhan M, Kwon OI, Woo EJ. Detection of temperature distribution via recovering electrical conductivity in MREIT. Phys Med Biol 2013; 58:2697-711. [DOI: 10.1088/0031-9155/58/8/2697] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Kim HJ, Jeong WC, Sajib SZK, Kim MO, Kwon OI, Je Woo E, Kim DH. Simultaneous imaging of dual-frequency electrical conductivity using a combination of MREIT and MREPT. Magn Reson Med 2013; 71:200-8. [PMID: 23400804 DOI: 10.1002/mrm.24642] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Revised: 12/10/2012] [Accepted: 01/02/2013] [Indexed: 11/08/2022]
Abstract
PURPOSE To propose a single magnetic resonance scan conductivity imaging technique providing dual-frequency characteristics of tissue conductivity. METHODS Using a modified spin-echo pulse sequence, the magnetic flux density induced by externally injected currents and the B1+ phase map with injected current effects removed were acquired simultaneously. The low-frequency conductivity was reconstructed from the measured magnetic flux density by the projected current density method, while the high-frequency conductivity was reconstructed using the B1+ maps. Three different conductivity phantoms were used to demonstrate low- and high-frequency conductivity characteristics. RESULTS A conductivity spectrum at two frequencies was successfully acquired with the proposed scheme. Magnetic resonance electrical impedance tomography is advantageous for seeing an anomaly itself wrapped with a thin insulating membrane. In addition, if the membrane is porous, the membrane property can be quantitatively visualized with magnetic resonance electrical impedance tomography. Magnetic resonance electrical properties tomography does not detect such membranes, which enable it to probe things inside an insulating membrane. CONCLUSION Considering these pros and cons and also the fact that the conductivity of biological tissue changes with frequency, a dual-frequency conductivity imaging incorporating both magnetic resonance electrical impedance tomography and magnetic resonance electrical properties tomography in future animal and human experiments is suggested.
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Affiliation(s)
- Hyung Joong Kim
- Department of Biomedical Engineering, Kyung Hee University, Korea
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An iterative method for problems with multiscale conductivity. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2013; 2012:893040. [PMID: 23304238 PMCID: PMC3523148 DOI: 10.1155/2012/893040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 10/16/2012] [Indexed: 11/18/2022]
Abstract
A model with its conductivity varying highly across a very thin layer will be considered. It is related to a stable phantom model, which is invented to generate a certain apparent conductivity inside a region surrounded by a thin cylinder with holes. The thin cylinder is an insulator and both inside and outside the thin cylinderare filled with the same saline. The injected current can enter only through the holes adopted to the thin cylinder. The model has a high contrast of conductivity discontinuity across the thin cylinder and the thickness of the layer and the size of holes are very small compared to the domain of the model problem. Numerical methods for such a model require a very fine mesh near the thin layer to resolve the conductivity discontinuity. In this work, an efficient numerical method for such a model problem is proposed by employing a uniform mesh, which need not resolve the conductivity discontinuity. The discrete problem is then solved by an iterative method, where the solution is improved by solving a simple discrete problem with a uniform conductivity. At each iteration, the right-hand side is updated by integrating the previous iterate over the thin cylinder. This process results in a certain smoothing effect on microscopic structures and our discrete model can provide a more practical tool for simulating the apparent conductivity. The convergence of the iterative method is analyzed regarding the contrast in the conductivity and the relative thickness of the layer. In numerical experiments, solutions of our method are compared to reference solutions obtained from COMSOL, where very fine meshes are used to resolve the conductivity discontinuity in the model. Errors of the voltage in L2 norm follow O(h) asymptotically and the current density matches quitewell those from the reference solution for a sufficiently small mesh size h. The experimental results present a promising feature of our approach for simulating the apparent conductivity related to changes in microscopic cellular structures.
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Woo EJ. High-resolution MREIT using low imaging currents. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2011:7025-7028. [PMID: 22255956 DOI: 10.1109/iembs.2011.6091776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Magnetic Resonance Electrical Impedance Tomography (MREIT) produces cross-sectional images of a conductivity distribution inside the human body. We use an MRI scanner as a tool to measure induced internal magnetic flux density distributions subject to externally injected currents. Recent experimental MREIT studies demonstrated conductivity image reconstructions of in vivo animal and human subjects with a few millimeter pixel size using 3 mA current injections. To enhance the clinical applicability of MREIT especially in neuroimaging applications, it is necessary to develop high-resolution MREIT techniques using low imaging currents. In this study, we demonstrate the capability of MREIT to perform conductivity imaging with less than 1 mA injection currents. The experimental results using a 3 T MRI scanner with a multi-echo ICNE pulse sequence and high-performance RF coils demonstrate that we can distinguish two different anomalies in reconstructed conductivity images with less than 1 mm pixel sizes. We plan to apply the developed experimental method to in vivo head imaging of small animals to investigate the feasibility of functional MREIT as a new neuro-imaging method.
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Affiliation(s)
- Eung Je Woo
- Department of Biomedical Engineering, Kyung HeeUniversity, Gyeonggi-do 446-701, Korea. ejwoo@ khu.ac.kr
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