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MREIT conductivity imaging of the postmortem canine abdomen using CoReHA
Jeon, Kiwan,Minhas, Atul S,Kim, Young Tae,Jeong, Woo Chul,Kim, Hyung Joong,Kang, Byeong Teck,Park, Hee Myung,Lee, Chang-Ock,Seo, Jin Keun,Woo, Eung Je IOP PUBLISHING 2009 PHYSIOLOGICAL MEASUREMENT Vol.30 No.9
<P>Magnetic resonance electrical impedance tomography (MREIT) is a new bio-imaging modality providing cross-sectional conductivity images from measurements of internal magnetic flux densities produced by externally injected currents. Recent experimental results of postmortem and <I>in vivo</I> imaging of the canine brain demonstrated its feasibility by showing conductivity images with meaningful contrast among different brain tissues. MREIT image reconstructions involve a series of data processing steps such as <I>k</I>-space data handling, phase unwrapping, image segmentation, meshing, modelling, finite element computation, denoising and so on. To facilitate experimental studies, we need a software tool that automates these data processing steps. In this paper, we summarize such an MREIT software package called CoReHA (conductivity reconstructor using harmonic algorithms). Performing imaging experiments of the postmortem canine abdomen, we demonstrate how CoReHA can be utilized in MREIT. The abdomen with a relatively large field of view and various organs imposes new technical challenges when it is chosen as an imaging domain. Summarizing a few improvements in the experimental MREIT technique, we report our first conductivity images of the postmortem canine abdomen. Illustrating reconstructed conductivity images, we discuss how they discern different organs including the kidney, spleen, stomach and small intestine. We elaborate, as an example, that conductivity images of the kidney show clear contrast among cortex, internal medulla, renal pelvis and urethra. We end this paper with a brief discussion on future work using different animal models.</P>
Jeon, Kiwan,Kim, Hyung Joong,Lee, Chang-Ock,Seo, Jin Keun,Woo, Eung Je Institute of Physics in association with the Ameri 2010 Physics in medicine & biology Vol.55 No.24
<P>Conductivity imaging based on the current-injection MRI technique has been developed in magnetic resonance electrical impedance tomography. Current injected through a pair of surface electrodes induces a magnetic flux density distribution inside an imaging object, which results in additional magnetic field inhomogeneity. We can extract phase changes related to the current injection and obtain an image of the induced magnetic flux density. Without rotating the object inside the bore, we can measure only one component <I>B<SUB>z</SUB></I> of the magnetic flux density <B>B</B> = (<I>B<SUB>x</SUB></I>, <I>B<SUB>y</SUB></I>, <I>B<SUB>z</SUB></I>). Based on a relation between the internal conductivity distribution and <I>B<SUB>z</SUB></I> data subject to multiple current injections, one may reconstruct cross-sectional conductivity images. As the image reconstruction algorithm, we have been using the harmonic <I>B<SUB>z</SUB></I> algorithm in numerous experimental studies. Performing conductivity imaging of intact animal and human subjects, we found technical difficulties that originated from the MR signal void phenomena in the local regions of bones, lungs and gas-filled tubular organs. Measured <I>B<SUB>z</SUB></I> data inside such a problematic region contain an excessive amount of noise that deteriorates the conductivity image quality. In order to alleviate this technical problem, we applied hybrid methods incorporating ramp-preserving denoising, harmonic inpainting with isotropic diffusion and ROI imaging using the local harmonic <I>B<SUB>z</SUB></I> algorithm. These methods allow us to produce conductivity images of intact animals with best achievable quality. We suggest guidelines to choose a hybrid method depending on the overall noise level and existence of distinct problematic regions of MR signal void.</P>
ALGEBRAIC CORRECTION FOR METAL ARTIFACT REDUCTION IN COMPUTED TOMOGRAPHY
KIWAN JEON,SUNG-HO KANG,CHI YOUNG AHN,SUNGWHAN KIM 한국산업응용수학회 2014 Journal of the Korean Society for Industrial and A Vol.18 No.2
If there are metals located in the X-ray scanned object, a point outside the metals gas its range of projection angle at which projections passing through the point are disturbed by the metals. Roughly speaking, this implies that attenuation information at the point is missing in the blocked projection range. So conventional projection completion MAR algorithms to use the undisturbed projection data on the boundary of the metaltrace is less efficient in reconstructing the attenuation coefficient in detailed parts, in particular, near the metal region. In order to overcome this problem, we propose the algebraic correction technique (ACT) to utilize a prereconstructed interim image of the attenuation coefficient outside the metal region which is obtained by solving a linear system designed to reduce computational costs. The reconstructed interim image of the attenuation coefficient is used as prior information for MAR. Numerical simulations support that the proposed correction technique shows better performance than conventional inpainting techniques such as the total variation and the harmonic inpainting.
Jeon, Kiwan,Lee, Chang-Ock,Woo, Eung Je TaylorFrancis 2018 Inverse problems in science and engineering Vol.26 No.6
<P> Magnetic resonance electrical impedance tomography (MREIT) is a high-resolution conductivity imaging method utilizing measured magnetic flux density data induced by externally injected currents. Most MREIT image reconstruction methods including the harmonic <I>Bz</I> algorithm adopt iterative schemes to handle the non-linear relation between conductivity and magnetic flux density. Iterative methods, however, may not guarantee a reliable conductivity reconstruction when the measured magnetic flux density data are contaminated with a significant amount of noise. In this paper, we propose a new image reconstruction method which alleviates the technical difficulties of the iterative harmonic <I>Bz</I> algorithm. It effectively reduces the number of iterations by two at most. To improve the image quality, it incorporates the influence of non-transversal current densities. Providing theoretical observations and details of the proposed algorithm, we present results of numerical simulations and phantom experiments for its validation. </P>
Kiwan Jeon,Hyung Joong Kim,Chang-Ock Lee,Jin Keun Seo,Eung Je Woo 한국산업응용수학회 2010 한국산업응용수학회 학술대회 논문집 Vol.5 No.1
Conductivity imaging based on the current-injection MRI technique has been developed in magnetic resonance electrical impedance tomography (MREIT). Injection current through a pair of surface electrodes induces a magnetic flux density distribution inside an imaging object, which results in extra field inhomogeneity. We can extract phase changes related with the current injection and obtain an image of the induced magnetic flux density. Without rotating the object inside the bore, we can measure only one component Bz of the magnetic flux density B = (Bx;By;Bz). Based on a relation between the internal conductivity distribution and Bz data subject to multiple current injections, one may reconstruct cross-sectional conductivity images. As the image reconstruction algorithm, we have been using the harmonic Bz algorithm in numerous experimental studies. Performing conductivity imaging of intact animal and human subjects, we found technical difficulties that are originated from the MR signal void phenomena in local regions of bones, lungs and gas-filled tubular organs. Measured Bz data inside such a problematic region contains an excessive amount of noise that deteriorates the conductivity image quality. In order to alleviate this technical problem, we applied hybrid methods incorporating the ramp-preserving denoising, the harmonic inpainting with isotropic diffusion and ROI imaging using the local harmonic Bz algorithm. These methods allow us to produce conductivity images of intact animals with best achievable quality. We suggest a guideline to choose a hybrid method depending on the overall noise level and existence of distinct problematic regions of MR signal void.
CoReHA 2.0: A Software Package for <i>In Vivo</i> MREIT Experiments
Jeon, Kiwan,Lee, Chang-Ock Hindawi Publishing Corporation 2013 Computational and mathematical methods in medicine Vol.2013 No.-
<P>Magnetic resonance electrical impedance tomography (MREIT) is a new medical imaging modality visualizing static conductivity images of electrically conducting subjects. Recently, MREIT has rapidly progressed in its theory, algorithm, and experiment technique and now reached to the stage of <I>in vivo</I> animal experiments. In this paper, we present a software, named CoReHA 2.0 standing for the second version of conductivity reconstructor using harmonic algorithms, to facilitate <I>in vivo</I> MREIT reconstruction of conductivity image. This software offers various computational tools including preprocessing of MREIT data, identification of 2D geometry of the imaging domain and electrode positions, and reconstruction of cross-sectional scaled conductivity images from MREIT data. In particular, in the new version, we added several tools including ramp-preserving denoising, harmonic inpainting, and local harmonic <I>B</I><SUB><I>z</I></SUB> algorithm to deal with data from <I>in vivo</I> experiments. The presented software will be useful to researchers in the field of MREIT for simulation, validation, and further technical development.</P>