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An electric and a magnetic field. An electric current produces a magnetic field by Ampere's circuital law.
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Ischemic heart disease (IHD) is one of the leading causes of death in the general population. Ischemia induces changes in the electrophysiologic properties of the myocardium that sometimes cannot be detected with rest ECG, which has a relatively low sensitivity. Magnetocardiography (MCG) which records the magnetic fields generated by the heart, is...
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... quantify the rotation of the magnetic field map orientation, they calculated the magnetic field map angle/heart rate slope, and compared it with normal controls. In this study, they found the heart rate-adjusted magnetic field map rotation detects transient myocardial ischemia more sensitively compared with the ST/heart rate slope of ECG ( Figure 10). Computerized diagnosis in which computer has ''learned'' to recognize normal and abnormal patterns based on 3 characteristics within the analysis window (the number of poles, the positions and movements of the poles, and the overall stability of the map) is also reported. ...
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... source in the heart produces a 2-pole pattern having positive and negative magnetic poles for each electrical current in a magnetic field map using Bz ( Figure 11). This complicates isomagnetic field map interpretation because the Bz contour map does not represent a direct one-to-one relationship between the magnetic field strength and the active region of the heart. ...
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... the plane Bxy is at right angles to Bz (Figure 11). Using this equation, we can transform the measured magnetic fields into electrical current just under the detecting SQUID (Figure 12), [34][35][36][37] and we can know the electric current of the heart with the current arrow map. ...
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... the plane Bxy is at right angles to Bz (Figure 11). Using this equation, we can transform the measured magnetic fields into electrical current just under the detecting SQUID (Figure 12), [34][35][36][37] and we can know the electric current of the heart with the current arrow map. ...
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... In addition, high time resolution of MCG (less than 5 ms) make visualization of the macro-reentrant circuits or microexcitations of atrial fibrillations, flutters, and atrial tachycardia possible. 38,39) In normal heart, the current arrow map during ventricular repolarization exhibits the single current pattern which indicates a leftward, inferior direc- tion 40,41) (Figure 12). Hailer et al. 42,43) reconstructed Upper panels: The change in magnetic field map angle after stress is greater in RCA patient than the control. ...
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... slope is obviously greater in RCA patient than that of control subjects. the current arrow map within the ST-T interval, and classified it from category 0 (normal) to category 4 (grossly abnormal) according to whether it indicates dipolar pattern or not, dipole orientation, directions of most vectors, and vortex equality ( Figure 13). In this diagnostic classification, the current arrow map pattern with single dipole oriented at leftward, inferior direction, and with equal vortexes is the completely normal (category 0) pattern. ...
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... transforming the measured magnetic fields (Bz) into electrical current (Bxy), we can determine the amplitude of the electric current force by the formula: Figure 14 illustrates the superimposed 64-channel waveforms of the magnitude of Bxy (jBxyj) of each channel. From this waveform, we can derive the electrical vector power of QRS or JT interval by integrating jBxyj waveform during each period (QRS integral and JT integral). ...
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... integral and JT integral represent the current intensity of the cardiac activity during each time interval. Figures 15 and 16 are the iso-integral maps in which the QRS integral and JT integral values for each of the 64 channels are color-displayed in cases of normal controls ( Figure 15) and cases with CAD ( Figure 16) by Tsukada K et al. 34) As stated by Tsukada et al., the iso-integral maps of the QRS integral and JT integral show similar patterns for all health subjects ( Figure 15). The maximum-value area in each map is located in the area of the left ventricle. ...
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... integral and JT integral represent the current intensity of the cardiac activity during each time interval. Figures 15 and 16 are the iso-integral maps in which the QRS integral and JT integral values for each of the 64 channels are color-displayed in cases of normal controls ( Figure 15) and cases with CAD ( Figure 16) by Tsukada K et al. 34) As stated by Tsukada et al., the iso-integral maps of the QRS integral and JT integral show similar patterns for all health subjects ( Figure 15). The maximum-value area in each map is located in the area of the left ventricle. ...
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... integral and JT integral represent the current intensity of the cardiac activity during each time interval. Figures 15 and 16 are the iso-integral maps in which the QRS integral and JT integral values for each of the 64 channels are color-displayed in cases of normal controls ( Figure 15) and cases with CAD ( Figure 16) by Tsukada K et al. 34) As stated by Tsukada et al., the iso-integral maps of the QRS integral and JT integral show similar patterns for all health subjects ( Figure 15). The maximum-value area in each map is located in the area of the left ventricle. ...
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... integral and JT integral represent the current intensity of the cardiac activity during each time interval. Figures 15 and 16 are the iso-integral maps in which the QRS integral and JT integral values for each of the 64 channels are color-displayed in cases of normal controls ( Figure 15) and cases with CAD ( Figure 16) by Tsukada K et al. 34) As stated by Tsukada et al., the iso-integral maps of the QRS integral and JT integral show similar patterns for all health subjects ( Figure 15). The maximum-value area in each map is located in the area of the left ventricle. ...
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... the integral values of the repolarization are always higher than that of the depolarization in each case. Compared to these observations, the iso-integral maps of the patients with IHD exhibited different patterns both in the depolarization and repolarization process (Figure 16). Moreover, all IHD patients' integral values of repolarizaton are always lower than those of the depolarization period. ...
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... we calculated JTi/QRSi to correct for the distance between the SQUID sensor and the origin of the magnetic field affecting the strength of the MCG signal. As a result, the ratio of the total current intensity during repolarization and depolari- zation in MCG (JTi/QRSi) is significantly smaller in patients with coronary stenosis compared with healthy controls ( Figure 17). Moreover, JTi/QRSi improved after coronary revascularization and no longer significantly differed from the control value. ...
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... findings indicated that the JTi/QRSi value of MCG reflects myocardial ischemia. We then exam- ined whether ECG can also reflect such improve- ment, but we found no significant changes after coronary revascularization (Figure 18), indicating that MCG is more sensitive than ECG in detecting myocardial ischemia. Finally, we examined age- related effects on the JTi/QRSi and found no differences within the control group, indicating that JTi/QRSi is not influenced by age (Figure 19). ...
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... then exam- ined whether ECG can also reflect such improve- ment, but we found no significant changes after coronary revascularization (Figure 18), indicating that MCG is more sensitive than ECG in detecting myocardial ischemia. Finally, we examined age- related effects on the JTi/QRSi and found no differences within the control group, indicating that JTi/QRSi is not influenced by age (Figure 19). ...
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... Measurements of magnetic fields generated by the human body provide a critical diagnostic and research tool [129][130][131][132][133][134][135][136]. Biomagnetic signal amplitudes are 6-9 orders of magnitude smaller than the earth's magnetic field of 50 µT, e.g. ...
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... This may be due to uncancelled laser and microwave noise some of which could be cancelled out through the implementation of a gradiometer which would also alleviate ambient magnetic noise from the environment [34,35]. To detect signals for MCG it is estimated that the sensitivity required would need to be over an order of magnitude beyond what we currently achieve [12,36]. ...
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