International Journal of Applied Electromagnetics and Mechanics - Volume 30, issue 3-4

Authors: Ziolkowski, M. | Gratkowski, S. | Palka, R.

Article Type: Research Article

Abstract: Magnetic induction tomography, highly promising imaging technique for medical purposes, applies a magnetic field from an exciter to induce eddy currents in the object of low conductivity, and the magnetic field from these is then detected by a sensor. The induced eddy currents are proportional to the conductivity distribution. This paper deals with the solution of the fundamental inverse problem existing in magnetic induction tomography, which consists in the reconstruction of the eddy currents distribution basing …on the magnetic field measurements. The problem has been solved by the Tikhonov regularization method. The choice of the regularization parameter and the accuracy of the proposed method have also been discussed. Show more

Keywords: Magnetic induction tomography, image reconstruction, Tikhonov regularization method

DOI: 10.3233/JAE-2009-1025

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 30, no. 3-4, pp. 245-253, 2009

Authors: Wondrak, Thomas | Stefani, Frank | Gundrum, Thomas | Gerbeth, Gunter

Article Type: Research Article

Abstract: The goal of contactless inductive flow tomography (CIFT) is the velocity reconstruction in electrically conducting melts which are used in many metallurgical and crystal growth applications. In this paper, we discuss some recent methodological improvements of this method, in particular the automatic search for an optimum regularisation parameter and the amended treatment of the boundary integrals.

Keywords: Inverse problems, industrial tomography, liquid metal flow measurement

DOI: 10.3233/JAE-2009-1026

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 30, no. 3-4, pp. 255-264, 2009

Authors: Weiser, Martin

Article Type: Research Article

Abstract: Regional hyperthermia is a cancer therapy aiming at heating tumors using phased array applicators. This article provides an overview over current mathematical challenges of delivering individually optimal treatments. The focus is on therapy planning and identification of technical as well as physiological quantities from magnetic resonance (MR) thermometry measurements.

Keywords: Hyperthermia treatment planning, identification, MR thermometry, interior point methods

DOI: 10.3233/JAE-2009-1027

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 30, no. 3-4, pp. 265-275, 2009

Authors: Cutrupi, V. | Ferraioli, F. | Formisano, A. | Martone, R.

Article Type: Research Article

Abstract: Purpose: This paper proposes an approach for the coupled EEG-MEG data analysis that takes into account the anisotropy of brain tissues and the different sensitivities of EEG and MEG measurements. Design/methodology/approach: The study is carried out by using a combination of analytical and numerical methods. In particular, where available, closed solutions are used to evaluate the numerical errors, while FEM models are used where anisotropy and geometrical characteristics make analytical solutions not applicable. …Findings: The impact of tissues anisotropy on coupled EEG-MEG analysis has been assessed, and the effectiveness of an approach based on smart exploitation of different EEG and MEG sensitivity to improve sources reconstruction has been demonstrated numerically. Research limitations/implications: The analysis has been carried out using a spherical head model, and on simulated data. Practical implications: The proposed approach allows to improve the localization of equivalent sources for the description of cellular brain activity. Originality/value: The properties of objective functions used in brain sources reconstruction from EEG and MEG has been investigated taking into account tissues anisotropy in the spherical symmetric case. In addition a formulation of the joint source and tissues tensor conductivity estimation by exploiting simultaneously bioelectric and biomagnetic measurements based on the complementary sensitivity of those measurements has been presented. Show more

Keywords: Identification problems, medical diagnostics, brain activity reconstruction

DOI: 10.3233/JAE-2009-1028

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 30, no. 3-4, pp. 277-288, 2009

Authors: Farina, Dmytro | Dössel, Olaf

Article Type: Research Article

Abstract: Non-invasive localization of premature ventricular beat (PVB) foci is very important for medical treatment of numerous cardiac diseases. In this work a model-based method of reconstruction of ectopic center locations is investigated. Within the scope of this method patient's multichannel ECG is used as a reference for optimization of an electrophysiological cardiac model. This model is based on the cellular automaton principle and utilizes anatomical data of the patient. Optimized are coordinates of the …ectopic focus as well as excitation conduction velocity of ventricular myocardium. Initial values for these parameters are obtained by solving the linearized problem of electrocardiography in terms of activation times. Optimization is performed by minimization of discrepancy between the simulated and reference ECGs. The aim of the current work is to estimate the quality of ectopic focus localization delivered by this method. Four sample ectopic beats have been simulated, with their foci located in different regions of the left ventricle. 1% Gaussian noise has been introduced into the resulting ECGs. In this way the "measured" ECG signals for this investigation have been obtained. Afterwards the origin of each ectopic beat has been reconstructed using the model-based approach. The method has demonstrated reliable localization of PVB foci, reconstruction errors have not exceeded 6.1 mm. Show more

Keywords: Ectopic beats, inverse problem of electrocardiography, cardiac modeling

DOI: 10.3233/JAE-2009-1029

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 30, no. 3-4, pp. 289-297, 2009

Authors: Kreutzbruck, Marc | Allweins, Kai | Strackbein, Chris | Bernau, Hendrick

Article Type: Research Article

Abstract: To meet the increasing fabrication quality standards and the high throughput requirements NDE techniques are reliant on efficient reconstruction tools and visualization tools. In this work we present an inverse algorithm for a modern electromagnetic non-destructive testing approach using a small GMR sensor array to inspect superconducting wires. Four sensitive GMR sensors are positioned around the wire. Small defects of 100 μm in size could be detected in a depth of 200 μm with a …signal-to-noise ratio of better than 400. Surface defects could be detected with a SNR of up to 10,000. This remarkably SNR and the small extent of GMR sensors results in a spatial resolution which offers new visualisation techniques for defect localisation, defect characterization and future tomography-like mapping techniques. We developed several inverse algorithms based on either a Finite Element Method or an analytical approach leading to defect localization with an accuracy of a few 10 μm. Show more

Keywords: Nondestructive testing, reconstruction, GMR-sensor array, superconducting wires

DOI: 10.3233/JAE-2009-1030

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 30, no. 3-4, pp. 299-308, 2009

Authors: Gyimóthy, Szabolcs | Kiss, Imre | Pávó, József

Article Type: Research Article

Abstract: An adaptive sampling method based on simplex-mesh refinement is proposed for creating a database that facilitates the inverse problem solution in NDT. The resulting database is used as a generic interpolator of the forward problem. In order to obtain optimal sampling for the purpose of interpolation, physically based mesh generation technique relying on spring analogy is utilized. The method is tested with a four-parameter crack reconstruction problem. It is demonstrated that the optimized database provides high …interpolation quality comparing to regular grid databases. Show more

Keywords: Inverse problems, database, nondestructive testing, interpolation

DOI: 10.3233/JAE-2009-1031

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 30, no. 3-4, pp. 309-319, 2009

Authors: Riganti Fulginei, Francesco | Salvini, Alessandro

Article Type: Research Article

Abstract: This paper presents the identification of the Jiles-Atherton and Preisach hysteresis models by means of a new heuristic: the Flock-of-Starlings Optimization (FSO). The FSO can be classified as an artificial life algorithm since it takes inspiration from the Particle Swarm Optimization (PSO) and from recent naturalistic observations on real flocks of common little European birds (starlings, Sturnus Vulgaris), performed by M. Ballerini et al. The one-to-one correspondence between the real flight of starlings searching food and …the virtual flight of candidate solutions searching global optima is the core of the algorithm. Validations and comparisons with other heuristics have shown that the FSO gives good performances especially in those cases in which the solution space has a huge dimension. In fact, from the analysis of the obtained results by testing the FSO on hysteresis model identification, this heuristic has shown to be very attractive in comparison with other famous heuristics. Show more

Keywords: Model identification, evolutionary computation, optimization

DOI: 10.3233/JAE-2009-1032

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 30, no. 3-4, pp. 321-331, 2009