Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

Sajib, Saurav Z. K.,Kim, Ji Eun,Jeong, Woo Chul,Kim, Hyung Joong,Kwon, Oh In,Woo, Eung Je American Institute of Physics 2015 Journal of Applied Physics Vol.117 No.10

Software Toolbox for Low-Frequency Conductivity and Current Density Imaging Using MRI

Sajib, Saurav Z. K.,Katoch, Nitish,Kim, Hyung Joong,Kwon, Oh In,Woo, Eung Je IEEE 2017 IEEE Transactions on Biomedical Engineering Vol.64 No.11

<P>Objective: Low-frequency conductivity and current density imaging using MRI includes magnetic resonance electrical impedance tomography (MREIT), diffusion tensor MREIT (DT-MREIT), conductivity tensor imaging (CTI), and magnetic resonance current density imaging (MRCDI). MRCDI and MREIT provide current density and isotropic conductivity images, respectively, using current-injection phase MRI techniques. DT-MREIT produces anisotropic conductivity tensor images by incorporating diffusion weighted MRI into MREIT. These current-injection techniques are finding clinical applications in diagnostic imaging and also in transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), and electroporation where treatment currents can function as imaging currents. To avoid adverse effects of nerve and muscle stimulations due to injected currents, conductivity tensor imaging (CTI) utilizes B1 mapping and multi-b diffusion weighted MRI to produce low-frequency anisotropic conductivity tensor images without injecting current. This paper describes numerical implementations of several key mathematical functions for conductivity and current density image reconstructions in MRCDI, MREIT, DT-MREIT, and CTI. Methods: To facilitate experimental studies of clinical applications, we developed a software toolbox for these low-frequency conductivity and current density imaging methods. This MR-based conductivity imaging (MRCI) toolbox includes 11 toolbox functions which can be used in the MATLAB environment. Results: The MRCI toolbox is available at http://iirc.khu.ac.kr/software.html . Its functions were tested by using several experimental datasets, which are provided together with the toolbox. Conclusion: Users of the toolbox can focus on experimental designs and interpretations of reconstructed images instead of developing their own image reconstruction softwares. We expect more toolbox functions to be added from future research outcomes.</P>

Angiospermic Plant Diversity of Southeast Offshore Islands in Bangladesh

Sajib, Noor Hassan,Pasha, Mostafa Kamal,Uddin, Shaikh Bokhtear Institute of Forest Science 2016 Journal of Forest Science Vol.32 No.1

A total of 680 angiosperm plant species under 433 genera of 115 families have been recorded from the Southeast offshore Islands of Bangladesh including Nijhum Dwip, Hatiya, Sandwip, Kutubdia, Maheshkhali, Sonadia and Saint Martin's. Magnoliopsida is represented by 92 families, 344 genera and 546 species, whereas Liliopsida is represented by 23 families, 89 genera and 134 species. Habit analysis shows that herbs, shrubs, trees and climbers were represented by 331, 117, 169 and 63 species respectively. The plant diversity of the southeast offshore islands is under great risk because of many threats including natural and manmade. The aims of the present study are investigation, accumulation and documentation of the angiosperm plants of the area.

Numerical simulation of electromagnetic field distribution induced in brain by electrical stimulation

Sajib, S.Z.K.,Woo, E.J.,Wi, H.,Kim, H.J.,Chauhan, M.,Meng, Z.J.,Oh, T.I.,Kwon, O.I.,Jeong, W.C. Institution of Electrical Engineers 2014 Electronics letters Vol.50 No.15

Influences of nano-3Y-TZP reinforcement on phase transformation and crystallite size modification of zirconia-toughened alumina and Rietveld refinement of crystallographic data

Dhar Sajib Aninda,Sarker Saugata,Mumu Homayra Tabassum,Rashid A. K. M. Bazlur 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.2

The effects of varying amount of nano-3 mol% yttria-stabilized zirconia addition on the crystal structures, mechanical, and microstructural properties of zirconia-toughened alumina (ZTA) composite have been investigated in this work. The ZTA specimens were prepared by different 3Y-TZP amount ranging from 9 to 18 wt.% and sintered at 1550 °C for 2 h. The densification behaviour, indentation fracture toughness, microhardness, elastic modulus, flexural strength and surface morphology of the composites have been determined and correlated with tetragonal → monoclinic phase transformation and retention of tetragonal phase. Rietveld refinement of the crystallographic data was performed to correlate the effect of zirconia addition on the phase compositions, t → m transformability and impacts on crystallite sizes and lattice parameter. The toughness and flexural strength of the composites improved significantly up to 15 wt.% YSZ addition followed by a reduction for 18 wt.%, while the hardness and elastic modulus decreased with YSZ addition. Rietveld refinement ascertains the metastable t-ZrO2 retention and thermodynamically stable m-ZrO2 transformation with increasing 3Y-TZP and subsequent enhancement in fracture toughness through transformation toughening.

Electrodeless Conductivity Tensor Imaging (CTI) using MRI: Basic Theory and Animal Experiments

Saurav ZK Sajib,권오인,김형중,우응제 대한의용생체공학회 2018 Biomedical Engineering Letters (BMEL) Vol.8 No.3

The electrical conductivity is a passive material property primarily determined by concentrations of charge carriers andtheir mobility. The macroscopic conductivity of a biological tissue at low frequency may exhibit anisotropy related with itsstructural directionality. When expressed as a tensor and properly quantified, the conductivity tensor can provide diagnosticinformation of numerous diseases. Imaging conductivity distributions inside the human body requires probing it byexternally injecting conduction currents or inducing eddy currents. At low frequency, the Faraday induction is negligibleand it has been necessary in most practical cases to inject currents through surface electrodes. Here we report a novelmethod to reconstruct conductivity tensor images using an MRI scanner without current injection. This electrodelessmethod of conductivity tensor imaging (CTI) utilizes B1 mapping to recover a high-frequency isotropic conductivity imagewhich is influenced by contents in both extracellular and intracellular spaces. Multi-b diffusion weighted imaging is thenutilized to extract the effects of the extracellular space and incorporate its directional structural property. Implementing thenovel 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 weightedimaging (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 brainstimulation, and electroporation.

Angiospermic Plant Diversity of Southeast Offshore Islands in Bangladesh

Noor Hassan Sajib,Mostafa Kamal Pasha,Shaikh Bokhtear Uddin 강원대학교 산림과학연구소 2016 Journal of Forest Science Vol.32 No.1

A total of 680 angiosperm plant species under 433 genera of 115 families have been recorded from the Southeast offshore Islands of Bangladesh including Nijhum Dwip, Hatiya, Sandwip, Kutubdia, Maheshkhali, Sonadia and Saint Martin’s. Magnoliopsida is represented by 92 families, 344 genera and 546 species, whereas Liliopsida is represented by 23 families, 89 genera and 134 species. Habit analysis shows that herbs, shrubs, trees and climbers were represented by 331, 117, 169 and 63 species respectively. The plant diversity of the southeast offshore islands is under great risk because of many threats including natural and manmade. The aims of the present study are investigation, accumulation and documentation of the angiosperm plants of the area.

Focused Current Density Imaging Using Internal Electrode in Magnetic Resonance Electrical Impedance Tomography (MREIT)

IEEE 2014 IEEE Transactions on Biomedical Engineering Vol.61 No.7

<P>Magnetic resonance electrical impedance tomography (MREIT) is an imaging modality capable of visualizing cross-sectional current density and/or conductivity distributions inside an electrically conducting object. It uses an MRI scanner to measure one component of the magnetic flux density induced by an externally injected current through a pair of surface electrodes. For the cases of deep brain stimulation (DBS), electroporation, and radio frequency (RF) ablation, internal electrodes can be used to improve the quality of the MREIT images. In this paper, we propose a new MREIT imaging method using internal electrodes to visualize a current density distribution within a local region around them. To evaluate its performance, we conducted and analyzed a series of numerical simulations and phantom imaging experiments. We compared the reconstructed current density images using the internal electrodes with the obtained using only the external electrodes. We found that the proposed method using the internal electrodes stably determines the current density in the focused region with better accuracy.</P>

A Low Frequency Band Watermarking with Weighted Correction in the Combined Cosine and Wavelet Transform Domain

코식뎁,Md. Sajib Al- Seraj,정의필 한국융합신호처리학회 2013 융합신호처리학회 논문지 (JISPS) Vol.14 No.1

A combined DWT and DCT based watermarking technique of low frequency watermarking with weighted correction is proposed. The DWT has excellent spatial localization, frequency spread and multi-resolution characteristics, which are similar to the theoretical models of the human visual system (HVS). The DCT based watermarking techniques offer compression while DWT based watermarking techniques offer scalability. These desirable properties are used in this combined watermarking technique. In the proposed method watermark bits are embedded in the low frequency band of each DCT block of selected DWT sub-band. The weighted correction is also used to improve the imperceptibility. The extracting procedure reverses the embedding operations without the reference of the original image. Compared with the similar approach by DCT based approach and DWT based approach, the experimental results show that the proposed algorithm apparently preserves superiori mage quality and robustness under various attacks such as JPEG compression, cropping, sharping, contrast adjustments and so on.

Numerical Simulations of MREIT Conductivity Imaging for Brain Tumor Detection

Meng, Zi Jun,Sajib, Saurav Z. K.,Chauhan, Munish,Sadleir, Rosalind J.,Kim, Hyung Joong,Kwon, Oh In,Woo, Eung Je Hindawi Publishing Corporation 2013 Computational and mathematical methods in medicine Vol.2013 No.-

<P>Magnetic resonance electrical impedance tomography (MREIT) is a new modality capable of imaging the electrical properties of human body using MRI phase information in conjunction with external current injection. Recent <I>in vivo</I> animal and human MREIT studies have revealed unique conductivity contrasts related to different physiological and pathological conditions of tissues or organs. When performing <I>in vivo</I> brain imaging, small imaging currents must be injected so as not to stimulate peripheral nerves in the skin, while delivery of imaging currents to the brain is relatively small due to the skull's low conductivity. As a result, injected imaging currents may induce small phase signals and the overall low phase SNR in brain tissues. In this study, we present numerical simulation results of the use of head MREIT for brain tumor detection. We used a realistic three-dimensional head model to compute signal levels produced as a consequence of a predicted doubling of conductivity occurring within simulated tumorous brain tissues. We determined the feasibility of measuring these changes in a time acceptable to human subjects by adding realistic noise levels measured from a candidate 3 T system. We also reconstructed conductivity contrast images, showing that such conductivity differences can be both detected and imaged. </P>