Abstract:

More than 20 years of research in imaging of bioelectric sources in the human heart have passed and a lot of effort has been devoted to the topic. In spite of that the method is not established in clinical practice but still just an interesting research topic of enthusiastic scientist. A review together with a comprehensive literature survey is given in this article. Recent developments and new trends are outlined.

Abstract:

Mapping of electrical endocardial activity is an important task for cardiac diagnosis and surgical treatment planning. Different kinds of catheters measure this activity with a limited number of electrodes. In recent years an increasing number of mapping systems is used in clinical routine. Various systems have been introduced and discussed in literature. This work deals with the localization of catheter electrodes in the heart with advanced techniques of digital image processing. The catheters - developed by various enterprises - differ in shape, handling and amount of electrodes. They are specified and presented in detail. Digital image analysis techniques like filters, Fourier and Hough transformation build the background and basics for this work. The main part describes the methods for the detection of the electrodes and the catheter strings. With these methods, it is possible to setup computer models for each catheter. The computer models can be used e. g. in numerical field calculation together with medical tomographic datasets.

Abstract:

Motion is one major problem of magnetic resonance imaging (MRI) of the coronary vessels. Despite of cardiac motion of the beating heart itself respiratory motion has to be considered (see MR movie of respiratory motion of the heart). Respiratory motion is commonly suppressed by gating techniques, which reduce scan efficiency. In principle modern MR scanners are able to correct those motion patterns prospectively, which can be described by a 3D affine transformation. A prospective motion correction approach could be used to increase the respiratory gating window and in consequence to reduce scan time. However, in order to achieve a sufficient correction the motion must be described quantitatively. In this initial study the respiratory motion of the heart (coronary vessels) was analysed and a new motion model described by an affine transformation was compared to two rigid motion models. The affine transformation model achieved a better fit (mean error < 1 mm for coronary vessels) than a rigid motion model describing translation in all directions (mean error < 2 mm) and a rigid motion model covering only superior-inferior motion (mean error <6 mm).

Abstract:

A model of the electromechanical behavior of a myocardial region is presented. The model combines an electrophysiological, a force development and an excitation propagation model. All of these models incorporate the effects of deformation of the myocardium. An extension of the traditional bidomain model for excitation propagation is proposed. The extension describes the stretch dependency of the conductivity tensor of the intra- and extracellular space and is constructed outgoing from physically motivated assumptions, which simplify the behavior of the conductivity tensor. The extension makes usage of the deformation gradient tensor, which is a foundation in the theory of continuums mechanics. The performed simulations illustrate some effects of myocardial electromechanical behavior.

Abstract:

Knowledge of the distribution of electrical fields in the human body is of importance for scientists, engineers and physicians. This paper shows one way to achieve this knowledge by numerical calculation based on macroscopic models of the human body. An anatomical model is created by preprocessing, segmentation and classification of the digital images within the Visible Man data set. Conductivity models are derived, which describe the distribution of electrical conductivity in the human body. A conductivity model is applied to solve an exemplary forward problem in electrophysiology, which consist of the calculation of the electrical field distribution arising from cardiac sources. The cardiac sources are obtained by a model of the excitation process within the heart. The calculation of electrical fields is carried out numerically by employing the finite difference method.

Abstract:

This paper describes the measurement of a data set used to create a three-dimensional (3-D) parametric model of atrial anatomy. A short introduction to porcine and human atrial anatomy is given and important anatomical differences are noted. The data acquisition techniques are described. A pig heart was arrested in diastole and perfusion fixed in-situ at physiological pressures with the chest open but the pericardium intact, then excised, cast and mounted. A six-degree-of-freedom measurement arm was used to measure three-dimensional epicardial surface geometry and fiber angles. An epicardial surface model was created using a computer aided design (CAD ) software program for reverse engineering. The model was used to direct the dissection of the heart into small tissue blocks from which endocardial fiber angles and wall thicknesses were measured. Tissue blocks were then cryo-sectioned for histology and the identification of conducting system structures. Figures and images illustrate the resulting surface model, the acquired fiber angles and wall thickness. This preliminary work provides a foundation for building a three-dimensional anatomically detailed model suitable as a mesh for computational analysis of atrial mechanics and electrophysiology.

Abstract:

This work deals with the simulation of the electrical cardiac excitation propagation based on anatomical models of the human heart and body. The generation of anatomical models applying different techniques of digital image processing to medical image data is described as well as the generation of electrophysiological models based on these anatomical models. Different spatial and temporal physical field distributions, e.g. the transmembrane potential, the current sources and the extracellular potentials, are calculated and visualized in sinus rhythm case as well as in pathological cases.

Abstract:

3rd Interventional MRI Symposium, Leipzig, Germany, May 12-13, P 03

Abstract:

In this paper, a new method for QRS complex analysis and estimation based on principal component analysis (PCA) and polynomial fitting techniques is presented. Multi-channel ECG signals were recorded and QRS complexes were obtained from every channel and aligned perfectly in matrices. For every channel, the covariance matrix was calculated from the QRS complex data matrix of many heartbeats. Then the corresponding eigenvectors and eigenvalues were calculated and reconstruction parameter vectors were computed by expansion of every beat in terms of the principal eigenvectors. These parameter vectors show short-term fluctuations that have to be discriminated from abrupt changes or long-term trends that might indicate diseases. For this purpose, first-order poly-fit methods were applied to the elements of the reconstruction parameter vectors. In healthy volunteers, subsequent QRS complexes were estimated by calculating the corresponding reconstruction parameter vectors derived from these functions. The similarity, absolute error and RMS error between the original and predicted QRS complexes were measured. Based on this work, thresholds can be defined for changes in the parameter vectors that indicate diseases.

Abstract:

Die Simulation der elektrischen Erregungsausbreitung im menschlichen Herzen gewinnt bei der kardiologischen Ausbildung, Diagnostik und Therapieplanung zunehmend an Bedeutung. Eine Möglichkeit die elektrische Erregungsausbreitung zu simulieren, basiert auf der Erstellung anatomischer Modelle, die die Basis für physiologische Modelle bilden. Auf statischen anatomischen Modellen basierende physiologische Modelle vernachlässigen bei der Simulation der Erregungsausbreitung den Einfluß der Bewegung auf die Berechnung der elektrischen Quellen im Herzen. Ziel dieser Arbeit ist es, ein dynamisches digitales Herzmodell zur Berechnung der elektrischen Quellen im menschlichen Herzen zu erstellen, das die Bewegung des Herzens berücksichtigt.