A new finite element formulation for the forward problem of electro-magnetic source imaging

The voltage measurements on the scalp and magnetic held measurements near the scalp can be used to compute spatio-temporal evolution of electric currents across the cerebral cortex. Such a representation can be called Electro-Magnetic Source Image. In order to interpret the measured fields accurately, a realistic numerical model of the head should be prepared that includes physical properties and geometry of the individual's head. For that purpose, in this study, Finite Element Method (FEM) is used to solve the scaler potential function. A new FEM formulation is derived that assumes constant current density in isoparametric volume elements. A software is prepared by optimizing the code to run in a PC with 128 MB memory. It is shown that, for a current dipole at 2.5 cm from the origin, the potential distribution can be solved within an accuracy of 0.5% in comparison with the exact solutions, with a mesh of 29001 nodes and 7000 elements. In order to solve the magnetic held, the surface integration tools developed in the same FEM code are used. For the same dipole location the radial magnetic fields are calculated within an accuracy of 2.2%. Obviously, the accuracy in results can be increased by increasing the number of nodes.
International Conference of the IEEE Engineering-in-Medicine-and-Biology-Society


A new boundary element method formulation for the forward problem solution of electro-magnetic source imaging
Tanzer, IO; Gençer, Nevzat Güneri (1997-11-02)
Numerical solution of the potential and magnetic fields far a given electrical source distribution in the human brain is the essential part of electro-magnetic source imaging. In this study, the performance of Boundary Element Method (BEM) with different surface element types is explored. A new BEM formulation is derived that makes use of isoparametric linear and quadratic elements. It is shown that, quadratic elements provides superior performance over linear elements in terms of computation time and accur...
A FEM based framework for simulation of thermal treatments: Application to steel quenching
Şimşir, Caner; Gür, Cemil Hakan (2008-12-01)
During thermal treatments, materials are usually subjected to continuous heating and cooling cycles during which microstructural evolution and mechanical interactions occur simultaneously at different length and time scales. Modeling of these processes necessitates dealing with inherent complexities such as phase transformations, large material property variations, complex couplings and boundary conditions. In this study, a mathematical framework based on finite element method (FEM) capable of predicting te...
A Comparison of Velocity Skin Effect Modeling With 2-D Transient and 3-D Quasi-Transient Finite Element Methods
Tosun, Nail; Ceylan, Doga; Polat, Hakan; Keysan, Ozan (2021-04-01)
The analysis of the velocity skin effect (VSE) in electromagnetic launchers (EMLs) requires a 3-D transient finite element method, unlike magnetic skin and proximity effects. However, VSE is dominant at high speeds, and this creates convergence problems when moving or deformed mesh physics is used in a transient FEM in the 3-D analysis. Commercial finite element software cannot solve the electromagnetic aspects of such a high-speed application with a transient solver in 3-D. Although 2-D approximations can ...
A numerical study on magneto-hydrodynamic mixed convection flow
Bozkaya, Canan (2014-01-01)
This paper, describes a study conducted to numerically investigate the two-dimensional, steady, laminar, magneto-hydrodynamic mixed convection flow and heat transfer characteristics in a lid-driven enclosure beneath an externally applied magnetic field. A solid square block is placed inside the cavity. The governing equations in the form of a stream function-vorticity-temperature formulation are solved numerically using the dual reciprocity boundary element method with constant elements. Treatment of nonlin...
Experimental results for 2D magnetic resonance electrical impedance tomography (MR-EIT) using magnetic flux density in one direction
Birgul, O; Eyüboğlu, Behçet Murat; Ider, YZ (IOP Publishing, 2003-11-07)
Magnetic resonance electrical impedance tomography (MR-EIT) is an emerging imaging technique that reconstructs conductivity images using magnetic flux density measurements acquired employing MRI together with conventional EIT measurements. In this study, experimental MR-EIT images from phantoms with conducting and insulator objects are presented. The technique is implemented using the 0.15 T Middle East Technical University MRI system. The dc current method used in magnetic resonance current density imaging...
Citation Formats
M. Ozdemir and N. G. Gençer, “A new finite element formulation for the forward problem of electro-magnetic source imaging,” CHICAGO, IL, 1997, vol. 19, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/53476.