Three-Dimensional Ventricular Activation Imaging by Means of Equivalent Current Source Modeling and Estimation

2006 ◽  
Author(s):  
Z. Liu ◽  
C. Liu ◽  
B. He
Keyword(s):  
Current Source ◽  
Three Dimensional ◽  
Source Modeling ◽  
Equivalent Current ◽  
Ventricular Activation

Noninvasive three-dimensional electrocardiographic imaging of ventricular activation sequence

2005 ◽  
Vol 289 (6) ◽  
pp. H2724-H2732 ◽  
Author(s):  
Xin Zhang ◽  
Indiresha Ramachandra ◽  
Zhongming Liu ◽  
Basharat Muneer ◽  
Steven M. Pogwizd ◽  
...  
Keyword(s):  
Surface Potential ◽  
Body Surface ◽  
Cardiac Arrhythmias ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Electrocardiographic Imaging ◽  
Ventricular Activation ◽  
Body Surface Potential ◽  
Life Threatening ◽  
Activation Sequence

Imaging the myocardial activation sequence is critical for improved diagnosis and treatment of life-threatening cardiac arrhythmias. It is desirable to reveal the underlying cardiac electrical activity throughout the three-dimensional (3-D) myocardium (rather than just the endocardial or epicardial surface) from noninvasive body surface potential measurements. A new 3-D electrocardiographic imaging technique (3-DEIT) based on the boundary element method (BEM) and multiobjective nonlinear optimization has been applied to reconstruct the cardiac activation sequences from body surface potential maps. Ultrafast computerized tomography scanning was performed for subsequent construction of the torso and heart models. Experimental studies were then conducted, during left and right ventricular pacing, in which noninvasive assessment of ventricular activation sequence by means of 3-DEIT was performed simultaneously with 3-D intracardiac mapping (up to 200 intramural sites) using specially designed plunge-needle electrodes in closed-chest rabbits. Estimated activation sequences from 3-DEIT were in good agreement with those constructed from simultaneously recorded intracardiac electrograms in the same animals. Averaged over 100 paced beats (from a total of 10 pacing sites), total activation times were comparable (53.3 ± 8.1 vs. 49.8 ± 5.2 ms), the localization error of site of initiation of activation was 5.73 ± 1.77 mm, and the relative error between the estimated and measured activation sequences was 0.32 ± 0.06. The present experimental results demonstrate that the 3-D paced ventricular activation sequence can be reconstructed by using noninvasive multisite body surface electrocardiographic measurements and imaging of heart-torso geometry. This new 3-D electrocardiographic imaging modality has the potential to guide catheter-based ablative interventions for the treatment of life-threatening cardiac arrhythmias.

Effect of Perospirone on p300 Electrophysiological Activity and Social Cognition in Schizophrenia: A Three-dimensional Analysis with (s)loreta

2009 ◽  
Vol 24 (S1) ◽  
pp. 1-1
Author(s):  
T. Sumiyoshi ◽  
Y. Higuchi ◽  
T. Itoh ◽  
M. Matsui ◽  
H. Arai ◽  
...  
Keyword(s):  
Social Cognition ◽  
Partial Agonist ◽  
Verbal Learning ◽  
Current Source ◽  
Three Dimensional ◽  
Event Related Potentials ◽  
Brain Regions ◽  
Electrophysiological Activity ◽  
Before And After ◽  
Related Potentials

The purpose of this study was to determine if perospirone, a second generation antipsychotic drug and partial agonist at serotonin-5-HT1A receptors, enhances electrophysiological activity, such as event-related potentials (ERPs), in frontal brain regions, as well as cognitive function in subjects with schizophrenia. P300 current source images were obtained by means of standardized low resolution brain electromagnetic tomography (sLORETA) before and after treatment with perospirone for 6 months. Perospirone significantly increased P300 current source density in the left superior frontal gyrus, and improved positive symptoms and performance on the script tasks, a measure of verbal social cognition. Perospirone also tended to enhance verbal learning memory in patients with schizophrenia. There was a significant correlation between the changes in P300 amplitudes on the left frontal lead and those in social cognition. These results suggest the changes in three-dimensional distribution of cortical activity, as demonstrated by sLORETA, may mediate some of the actions of antipsychotic drugs. the distinct cognition-enhancing profile of perospirone may be related to its actions on 5-HT1A receptors.

scholarly journals Three-Dimensional Inversion of Borehole-Surface Resistivity Method Based on the Unstructured Finite Element

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhi Wang ◽  
Sinan Fang
Keyword(s):  
Numerical Solution ◽  
Surface Topography ◽  
Current Source ◽  
Three Dimensional ◽  
Surface Resistivity ◽  
Normal Equation ◽  
Inversion Algorithm ◽  
Field Source ◽  
Resistivity Method ◽  
Borehole Surface

The electromagnetic wave signal from the electromagnetic field source generates induction signals after reaching the target geological body through the underground medium. The time and spatial distribution rules of the artificial or the natural electromagnetic fields are obtained for the exploration of mineral resources of the subsurface and determining the geological structure of the subsurface to solve the geological problems. The goal of electromagnetic data processing is to suppress the noise and improve the signal-to-noise ratio and the inversion of resistivity data. Inversion has always been the focus of research in the field of electromagnetic methods. In this paper, the three-dimensional borehole-surface resistivity method is explored based on the principle of geometric sounding, and the three-dimensional inversion algorithm of the borehole-surface resistivity method in arbitrary surface topography is proposed. The forward simulation and calculation start from the partial differential equation and the boundary conditions of the total potential of the three-dimensional point current source field are satisfied. Then the unstructured tetrahedral grids are used to discretely subdivide the calculation area that can well fit the complex structure of subsurface and undulating surface topography. The accuracy of the numerical solution is low due to the rapid attenuation of the electric field at the point current source and the nearby positions and sharply varying potential gradients. Therefore, the mesh density is defined at the local area, that is, the vicinity of the source electrode and the measuring electrode. The mesh refinement can effectively reduce the influence of the source point and its vicinity and improve the accuracy of the numerical solution. The stiffness matrix is stored with Compressed Row Storage (CSR) format, and the final large linear equations are solved using the Super Symmetric Over Relaxation Preconditioned Conjugate Gradient (SSOR-PCG) method. The quasi-Newton method with limited memory (L_BFGS) is used to optimize the objective function in the inversion calculation, and a double-loop recursive method is used to solve the normal equation obtained at each iteration in order to avoid computing and storing the sensitivity matrix explicitly and reduce the amount of calculation. The comprehensive application of the above methods makes the 3D inversion algorithm efficient, accurate, and stable. The three-dimensional inversion test is performed on the synthetic data of multiple theoretical geoelectric models with topography (a single anomaly model under valley and a single anomaly model under mountain) to verify the effectiveness of the proposed algorithm.

scholarly journals A protocol combining current- and voltage-clamp provides a novel and useful three-dimensional representation of cardiac action potential

2014 ◽  
Vol 87 (1) ◽  
Author(s):  
Massimiliano Zaniboni ◽  
Francesca Cacciani
Keyword(s):  
Action Potential ◽  
Current Source ◽  
Three Dimensional ◽  
Membrane Conductance ◽  
Ventricular Repolarization ◽  
Cardiac Action Potential ◽  
Dimensional Representation ◽  
Cardiac Action ◽  
Three Dimensional Representation

A compact three-dimensional representation of cardiac action potential (AP) properties in terms of current source is presented here. The experimental protocol used to obtain such representation is based on the measure of instantaneous current-voltage relationships during the course of the AP. The procedure, which combines current- and voltage-clamps on patch clamped cardiac myocytes, has been previously applied to real cells, and then extended to computer simulations with cellular ventricular AP models. The three-dimensional AP representation allows to easily estimate membrane resistance during repolarization, a key factor for the modulation of ventricular repolarization. It also shows that, during late ventricular repolarization, membrane conductance becomes negative, <em>i.e.</em> repolarization is auto-regenerative. The novel AP representation is therefore a useful tool for both in vivo and in silico cardiac cellular electrophysiological investigations.

Electromagnetic induction by a finite electric dipole source over a 2-D earth

Geophysics ◽  
1993 ◽  
Vol 58 (2) ◽  
pp. 198-214 ◽  
Author(s):  
Martyn J. Unsworth ◽  
Bryan J. Travis ◽  
Alan D. Chave
Keyword(s):  
Finite Element ◽  
Electromagnetic Fields ◽  
Electric Dipole ◽  
Numerical Solutions ◽  
Current Source ◽  
Three Dimensional ◽  
Iterative Solution ◽  
Electromagnetic Response ◽  
Dipole Source ◽  
Horizontal Electric Dipole

A numerical solution for the frequency domain electromagnetic response of a two‐dimensional (2-D) conductivity structure to excitation by a three‐dimensional (3-D) current source has been developed. The fields are Fourier transformed in the invariant conductivity direction and then expressed in a variational form. At each of a set of discrete spatial wavenumbers a finite‐element method is used to obtain a solution for the secondary electromagnetic fields. The finite element uses exponential elements to efficiently model the fields in the far‐field. In combination with an iterative solution for the along‐strike electromagnetic fields, this produces a considerable reduction in computation costs. The numerical solutions for a horizontal electric dipole are computed and shown to agree with closed form expressions and to converge with respect to the parameterization. Finally some simple examples of the electromagnetic fields produced by horizontal electric dipole sources at both the seafloor and air‐earth interface are presented to illustrate the usefulness of the code.

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