Conductivity tensor imaging of the brain using diffusion-weighted magnetic resonance imaging

Sekino, Masaki; Yamaguchi, Katsuya; Iriguchi, Norio; Ueno, S.

doi:10.1063/1.1544446

Cited by 41 publications

(26 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Unlike the previous method by Tuch et al 7 and Sekino et al, 15 the proposed DT-MREIT technique could successfully reconstruct the scale factor at each voxel position from the measured diffusion tensor and the z-component of the magnetic flux density data induced by the externally injected currents. Since the distribution of ion concentration and motility varies with the position in three dimensional space, the scale factor for obtaining the equivalent conductivity tensor from the diffusion tensor information consequently depends on the voxel positions.…”

Section: Discussionmentioning

confidence: 92%

Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

et al. 2016

View full text Add to dashboard Cite

Anisotropy of biological tissues is a low-frequency phenomenon that is associated with the function and structure of cell membranes. Imaging of anisotropic conductivity has potential for the analysis of interactions between electromagnetic fields and biological systems, such as the prediction of current pathways in electrical stimulation therapy. To improve application to the clinical environment, precise approaches are required to understand the exact responses inside the human body subjected to the stimulated currents. In this study, we experimentally evaluate the anisotropic conductivity tensor distribution of canine brain tissues, using a recently developed diffusion tensor-magnetic resonance electrical impedance tomography method. At low frequency, electrical conductivity of the biological tissues can be expressed as a product of the mobility and concentration of ions in the extracellular space. From diffusion tensor images of the brain, we can obtain directional information on diffusive movements of water molecules, which correspond to the mobility of ions. The position dependent scale factor, which provides information on ion concentration, was successfully calculated from the magnetic flux density, to obtain the equivalent conductivity tensor. By combining the information from both techniques, we can finally reconstruct the anisotropic conductivity tensor images of brain tissues. The reconstructed conductivity images better demonstrate the enhanced signal intensity in strongly anisotropic brain regions, compared with those resulting from previous methods using a global scale factor.

show abstract

Section: Discussionmentioning

confidence: 92%

Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

et al. 2016

View full text Add to dashboard Cite

show abstract

“…We proposed three different methods of impedance imaging based on new principles of MRI: (1) Impedance MRI using large flip angles ]; (2) Impedance MRI with an additional AC coil [Yukawa et al, 1999]; and (3) Impedance MRI based on diffusion tensor MRI [Sekino et al, 2003a[Sekino et al, , 2005a[Sekino et al, , 2009a.…”

Section: Impedance Mri and Current Mrimentioning

confidence: 99%

“…We obtained conductivity tensor imaging of the rat brain and the human brain based on diffusion-weighted MRI. In the case of the rat brain, diffusion-weighted images were acquired by a 4.7 T MRI system with motion probing gradients (MPGs) applied in three or six directions [Sekino et al, 2003a[Sekino et al, , 2009a. Conductivities in each MPG direction were calculated from the fast component of the apparent diffusion coefficient (ADC) and the fraction of the fast component, and the conductivity tensor was estimated.…”

Section: Impedance Mri and Current Mrimentioning

confidence: 99%

Studies on magnetism and bioelectromagnetics for 45 years: From magnetic analog memory to human brain stimulation and imaging

Ueno

2011

Bioelectromagnetics

Self Cite

View full text Add to dashboard Cite

Forty-five years of studies on magnetism and bioelectromagnetics, in our laboratory, are presented. This article is prepared for the d'Arsonval Award Lecture. After a short introduction of our early work on magnetic analog memory, we review and discuss the following topics: (1) Magnetic nerve stimulation and localized transcranial magnetic stimulation (TMS) of the human brain by figure-eight coils; (2) Measurements of weak magnetic fields generated from the brain by superconducting quantum interference device (SQUID) systems, called magnetoencephalography (MEG), and its application in functional brain studies; (3) New methods of magnetic resonance imaging (MRI) for the imaging of impedance of the brain, called impedance MRI, and the imaging of neuronal current activities in the brain, called current MRI; (4) Cancer therapy and other medical treatments by pulsed magnetic fields; (5) Effects of static magnetic fields and magnetic control of cell orientation and cell growth; and (6) Effects of radio frequency magnetic fields and control of iron ion release and uptake from and into ferritins, iron cage proteins. These bioelectromagnetic studies have opened new horizons in magnetism and medicine, in particular for brain research and treatment of ailments such as depression, Parkinson's, and Alzheimer's diseases.

show abstract

“…It is well known that brain white matter has strong anisotropic characteristics, because it consists of numerous nerve bundles with inherent directional information. 4,5 The electrical tissue conductivity relies on the actual pathways of current flow inside the brain, [24][25][26][27] and shows more enhanced conductivity than its actual value. This clear contrast originates because the current density of the anisotropic model represents a more realistic distribution, combining the assigned conductivity and actual current flows from the DTI information.…”

Section: Quantitative Analysismentioning

confidence: 99%

Evaluation of three-dimensional anisotropic head model for mapping realistic electromagnetic fields of brain tissues

Jeong

Sajib

et al. 2015

AIP Advances

View full text Add to dashboard Cite

Electromagnetic fields provide fundamental data for the imaging of electrical tissue properties, such as conductivity and permittivity, in recent magnetic resonance (MR)-based tissue property mapping. The induced voltage, current density, and magnetic flux density caused by externally injected current are critical factors for determining the image quality of electrical tissue conductivity. As a useful tool to identify bio-electromagnetic phenomena, precise approaches are required to understand the exact responses inside the human body subject to an injected currents. In this study, we provide the numerical simulation results of electromagnetic field mapping of brain tissues using a MR-based conductivity imaging method. First, we implemented a realistic three-dimensional human anisotropic head model using high-resolution anatomical and diffusion tensor MR images. The voltage, current density, and magnetic flux density of brain tissues were imaged by injecting 1 mA of current through pairs of electrodes on the surface of our head model. The current density map of anisotropic brain tissues was calculated from the measured magnetic flux density based on the linear relationship between the water diffusion tensor and the electrical conductivity tensor. Comparing the current density to the previous isotropic model, the anisotropic model clearly showed the differences between the brain tissues. This originates from the enhanced signals by the inherent conductivity contrast as well as the actual tissue condition resulting from the injected currents.

show abstract

Conductivity tensor imaging of the brain using diffusion-weighted magnetic resonance imaging

Cited by 41 publications

References 10 publications

Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

Studies on magnetism and bioelectromagnetics for 45 years: From magnetic analog memory to human brain stimulation and imaging

Evaluation of three-dimensional anisotropic head model for mapping realistic electromagnetic fields of brain tissues

Contact Info

Product

Resources

About