Algebraic reconstraction for 3D magnetic resonance-electrical impedance tomography (MREIT) using one component of magnetic flux density

Magnetic resonance-electrical impedance tomography (MREIT) algorithms fall into two categories: those utilizing internal current density and those utilizing only one component of measured magnetic flux density. The latter group of algorithms have the advantage that the object does not have to be rotated in the magnetic resonance imaging (MRI) system. A new algorithm which uses only one component of measured magnetic flux density is developed. In this method, the imaging problem is formulated as the solution of a non-linear matrix equation which is solved iteratively to reconstruct resistivity. Numerical simulations are performed to test the algorithm both for noise-free and noisy cases. The uniqueness of the solution is monitored by looking at the singular value behavior of the matrix and it is shown that at least two current injection profiles are necessary. The method is also modified to handle region-of-interest reconstructions. In particular it is shown that, if the image of a certain xy-slice is sought for, then it suffices to measure the z-component of magnetic flux density up to a distance above and below that slice. The method is robust and has good convergence behavior for the simulation phantoms used

Uniqueness and reconstruction in magnetic resonance-electrical impedance tomography (MR-EIT)

Magnetic resonance-electrical impedance tomography (MR-EIT) was first proposed in 1992. Since then various reconstruction algorithms have been suggested and applied. These algorithms use peripheral voltage measurements and internal current density measurements in different combinations. In this study the problem of MR-EIT is treated as a hyperbolic system of first-order partial differential equations, and three numerical methods are proposed for its solution. This approach is not utilized in any of the algorithms proposed earlier. The numerical solution methods are integration along equipotential surfaces (method of characteristics), integration on a Cartesian grid, and inversion of a system matrix derived by a finite difference formulation. It is shown that if some uniqueness conditions are satisfied, then using at least two injected current patterns, resistivity can be reconstructed apart from a multiplicative constant. This constant can then be identified using a single voltage measurement. The methods proposed are direct, non-iterative, and valid and feasible for 3D reconstructions. They can also be used to easily obtain slice and field-of-view images from a 3D object. 2D simulations are made to illustrate the performance of the algorithms

Simulation of real beam ground mapping mode of a pulsed radar [Darbeli radar ile yer haritalamanin bilgisayar benzetimi]

A Matlab© based realistic simulation software is developed for Real Beam Ground Mapping (RBGM) mode of a pulsed air-borne radar. The developed software successfully simulates the effects of basic radar parameters for the real beam mapping mode. A zero level Digital Terrain Elevation Data (DiTED) is used for terrain model. Radar return is calculated for a stationary antenna at a given height from the ground and tilt angle. Simulations can represent the effects of terrain occulting, shadowing, incidence angle depended scattering, range attenuation, antenna parameters (pattern, gain, beam width e.g.) and transmitter parameters (frequency, output power, pulse width, PRF e.g.) on radar returns for both sector and circular scans. © 2006 IEEE