![]() It is therefore natural to select source and conductor models for magnetocardiography that are on the same level of complexity as for electrocardiography. Magnetocardiography was intended, at least initially, to complement the electric measurements of the heart's electric activity, or possibly replace it (e.g., in screening tests). The volume conductor is modeled either with the trivial solution (i.e., a homogeneous unbounded or spherical boundary) in the 12-lead ECG or with a finite (realistic), homogeneous conductor in the Frank VECG. From that table, one can see that in present clinical electrocardiography (standard 12-lead system and Frank vectorelectrocardiography (VECG)), a dipole with a fixed location is used as the model of the cardiac electric source. Table 17.1 (Section 17.4) lists several source and conductor models, tacitly assumed in various electrocardiographic lead systems. SOURCE: Magnetic dipole in a fixed locationĬONDUCTOR: Finite, homogeneous (or possibly inhomogeneous) The main purpose of this chapter is to discuss the lead systems currently being applied in detecting the equivalent magnetic dipole of the heart, and to discuss briefly the ECG-MCG relationship.Ģ0.2ěASIC METHODS IN MAGNETOCARDIOGRAPHY 20.2.1 Measurement of the equivalent magnetic dipole An overview of the methods for solving the biomagnetic inverse problem can be found in Swithenby (1987). ![]() The localization of arrhythmogenic centers has also been a subject of intensive research. There exist also many other kinds of trials for finding out clinical applications for the MCG - for example, testing the risk for sudden cardiac death and for rejection of an implanted heart. Though the detection of the magnetic heart vector is an obvious selection as the first clinical tool, many of the MCG studies of today have been made by mapping the normal component of the magnetic field of the heart around the thorax. Since the concept of the magnetic heart vector was introduced by Baule and McFee in 1970, studies have been conducted to detect the vectormagnetocardiogram (i.e., in which the heart is considered as a magnetic dipole). ![]() ![]() For instance, as will be discussed in Section 20.7, according to the present understanding, with the combined use of the ECG and the MCG, called electromagnetocardiogram, (EMCG), in some cardiac diseases the number of incorrectly diagnosed patients can be decreased by one half of that when using only the ECG is used. Though this has been shown theoretically (Rush, 1975) and in practical clinical studies not to be true, there are still many potential clinical applications of the MCG. The discovery raised a lot of optimism, as it was believed that MCG would provide as much new information about the heart's electric activity as had the ECG. The first biomagnetic signal to be detected was the magnetocardiogram (MCG) by Baule and McFee (1963). ![]()
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