Abstract:

Magnetocardiography (MCG) deals with the measurement of biomagnetic fields due to electrical excitation of the heart. The solution of the inverse problem of MCG and electrocardiography (ECG) is the reconstruction and visualization of the excitation process. The calculation is performed from MCG data recorded by multichannel systems. For a maximum of information content an optimized magnetometer arrangement is determined which is not realized at present. The information content with respect to imaging of bioelectric sources is defined by the slope of the singular values, respective the signal-to-noise ratio and the dimension of the nullspace. Reconstruction errors due to modelling errors are not taken into account in this work. The nullspace describes the set of non-detectable source patterns in MCG and ECG. A conventional commercial sensor arrangement will be compared to an improved sensor composition. Recent publications show evidence that MCG contains more or different diagnostic information in cardiac arrhythmia and infarction diagnosis than electrocardiography. Therefore, first results of a general comparison of the information content of MCG and ECG are presented.

Abstract:

Non invasive source reconstruction from Electrocardiography (ECG) and Magnetocardiography (MCG) data is a highly discussed research field. In this work we investigate mathematically the source space of the Inverse Problem of Electrocardiography with respect to the information content. Starting from the modeled source space of distributed epicardial potentials we compare several ECG electrode configurations, i.e. a 32-, 64-optimized channel electrode arrangement, that we determined for our individual torso model, the 256-lead ECG configuration which was recorded at the Ragnar Granit Instiute, Technical University of Tampere, Finland and the 128 channel system of the BioMag Laboratory, Helsinki University Central Hospital, Finland.

Abstract:

Noninvasive Imaging of the bioelectric processes on the heart using Electrocardiography (ECG) and Magnetocardiography (MCG) data is a widely discussed research topic of the recent years. The source space of ECG is compared with the source space of MCG and vice versa to investigate the difference of information content of these mapping techniques for source imaging purposes. The approach allows the calculation of the intersection and non-intersection part (the calculation of silent sources) of MCG (ECG) in comparison to ECG (MCG). The investigation was carried out on a Finite Element model which was constructed from a magnetic resonance imaging (MRI) dataset of a volunteer. Anisotropic fibre orientation was applied to myocardium to investigate its effect on the differences of the source spaces.

Abstract:

Clinical measurements of atrial excitation propagation were performed to validate the results of noninvasive cardiac source reconstructions. Epicardial potentials and transmembrane voltages were reconstructed using an individual volume conductor model of the patient. Activation times were measured with a basket catheter and compared with the time course of the reconstructed epicardial potentials and transmembrane voltages.

Abstract:

A new approach to the reconstruction of transmembrane potentials (TMP) in anisotropic finite element heart model is presented. The solution is sought in the form of 3D patches constructed by the interpolation of TMP distributions. The method is evaluated using TMP distributions generated with a cellular automaton.