Multichannel SQUID system detecting tangential components of the cardiac magnetic field

Tsukada, Keiji; Haruta, Yasuhiro; Adachi, Akira; Ogata, H.; Komuro, Takashi; Ito, Tsuyoshi; Takada, Yoshio; Kandori, Akihiko; Noda, Y.; Terada, Yasushi; Mitsui, Toshio

doi:10.1063/1.1146524

Cited by 65 publications

(35 citation statements)

References 12 publications

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“…A 0.1-100-Hz band-pass filter and a 50-Hz power-line noise filter were applied. Details of the SQUID system have been described in a previous report (9). Immediately before fMCG recording, the shortest distance from the maternal abdominal surface to the anterior ventricular surface of the fetal heart (d 1 ) was determined by ultrasonography.…”

Section: Study Populationmentioning

confidence: 99%

Detection of Cardiac Hypertrophy in the Fetus by Approximation of the Current Dipole Using Magnetocardiography

et al. 2001

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To determine the developmental changes in the myocardial current during fetal life, and to evaluate the clinical usefulness of magnetocardiography for prenatal diagnosis of cardiac hypertrophy or enlargement, we approximated the magnitude of the one-current dipole of the fetal heart using fetal magnetocardiography (fMCG). A total of 95 fetuses with gestational age of 20 -40 wk were included in this study. fMCG was recorded with a nine-channel superconducting quantum interference device system in a magnetically shielded room. The magnitude of the dipole (Q) was calculated using an equation based on the fMCG amplitude obtained on the maternal abdomen and the distance between the maternal surface and fetal heart measured ultrasonographically. In uncomplicated pregnancies, the Q value correlated significantly with gestational age, reflecting an increase in the amount of myocardial current, i.e. myocardial mass. Moreover, the Q values in fetuses with cardiomegaly caused by various cardiovascular abnormalities tended to be higher than the normal values. Although there are some limitations of the methodology based on the half-space model, and fetal orientation may influence the magnitude of the dipole, making it smaller, fMCG recorded with a multichannel superconducting quantum interference device system is a clinically useful tool for noninvasive, prenatal, and electrical evaluation of fetal cardiac hypertrophy. (1) in 1974, the magnetic field generated by the fetal heart has been measured noninvasively with satisfactory waveforms. MCG requires no pasting of electrodes to the fetal body surface and is completely noninvasive to both fetus and mother. MCG signals from the fetal heart are considered to be minimally affected by the electrical conduction properties of the tissue around the heart (2, 3). In fact, time intervals can be obtained with satisfactory signal-to-noise ratio even after the development of vernix caseosa in the second half of gestation. A number of studies, including ours, defined the developmental changes and normal ranges of various time intervals on the fMCG in uncomplicated pregnancies (4 -6). However, the amplitude of the fMCG waveform has not been fully investigated (7), although it is another important variable used for the diagnosis of fetal heart diseases. One reason for this rare application is that the amplitude of fMCG measured on the maternal abdomen does not necessarily reflect the maximum value of myocardial current because of the effects of the depth and orientation of the heart. Furthermore, these biases are not easily corrected as the fetus may move during measurement.We attempted to approximate the magnitude of the onecurrent dipole of the fetal heart based on the maximum value of fMCG data obtained with a multichannel SQUID system and the depth of the fetal heart determined by echocardiography in normal pregnancies. We then used these control values to assess magnitude abnormalities in fetuses with cardiomegaly resulting from excessive volume loading in cardiac ventricles. Using bo...

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Section: Study Populationmentioning

confidence: 99%

Detection of Cardiac Hypertrophy in the Fetus by Approximation of the Current Dipole Using Magnetocardiography

et al. 2001

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“…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.…”

Section: Restmentioning

confidence: 99%

Magnetocardiography in Early Detection of Electromagnetic Abnormality in Ischemic Heart Disease

Watanabe

Yamada

2008

Journal of Arrhythmia

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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 reported more sensitive for measuring myocardial electric activity. Many analyzing methods using MCG for the diagnosis of IHD are reported. Those methods can be summarized as follows: 1. magnetic measurement of ST and TQ segment shift, 2. spatial dispersion of the magnetocardiographically determined QT intervals (QT dispersion), 3. ST current angle rotation of magnetic field (isomagnetic map) at rest or in exercise magnetocardiography, 4. analyzing current arrow map during ventricular repolarization, and 5. analyzing the integral values of reporalization In this review we will given an overview of the current status of MCG methods for the diagnosis of IHD. (J Arrhythmia 2008; 24: 4-17)

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“…We measure the normal components (Z components) of the cardiac magnetic fields with a minimal interval of 0.5 ms and analyze both the normal and the tangential components (X and Y components). The tangential components are calculated from the normal components by using the equation: where Bz is the measured-normal component (in pico tesla, pT) and Bxy´is the calculated tangential component (pT/ m) (28)(29)(30).…”

Section: Mcg Systemmentioning

confidence: 99%

Magnetocardiograms in Clinical Medicine: Unique Information on Cardiac Ischemia, Arrhythmias, and Fetal Diagnosis

Yamada

Yamaguchi

2005

Intern. Med.

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Cardiac diseases are the leading cause of death in population. Diagnostic tests to detect cardiac dysfunction at an early stage of the disease are desirable. The major focus has been centered on tests evaluating the perfusion of the heart with imaging techniques or detecting alterations in electrical or mechanical function of the heart. The heart generates magnetic fields that can be detected by body surface mapping utilizing super conducting quantum interference device sensors giving magnetocardiograms (MCGs). The advantages of MCG over traditional electrocardiograms (ECGs) are increased sensitivity to small signals and lack of conductivity in body tissues, presentation of direct component signals and primary currents. This review will highlight the basic principles and recent advantages of MCGs, and the application of MCG in clinical diagnosis, especially in cases whose ECGs are non-diagnostic or not specific, such as detecting baseline shift in ischemic heart disease, noninvasive His potential recording, detection of arrhythmic mechanism defining reentrant circuits vs non reentrant mechanism, diagnosis of fetal arrhythmias and prolongation of QT interval. Areas of future basic and clinical research are also discussed. (Internal Medicine 44: 1-19, 2005)

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Multichannel SQUID system detecting tangential components of the cardiac magnetic field

Cited by 65 publications

References 12 publications

Detection of Cardiac Hypertrophy in the Fetus by Approximation of the Current Dipole Using Magnetocardiography

Detection of Cardiac Hypertrophy in the Fetus by Approximation of the Current Dipole Using Magnetocardiography

Magnetocardiography in Early Detection of Electromagnetic Abnormality in Ischemic Heart Disease

Magnetocardiograms in Clinical Medicine: Unique Information on Cardiac Ischemia, Arrhythmias, and Fetal Diagnosis

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