Two-dimensional mapping of impedance magnetocardiograms

Akihiko Kandori, Tsuyoshi Miyashita, Daisuke Suzuki, Koichi Yokosawa, Keiji Tsukada

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

A new method for measuring two-dimensional (2-D) impedance magnetocardiograms (I-MCGs) and magnetocardiograms (MCGs) above the heart simultaneously, has been developed. The I-MCG's and MCG's signals are recorded by using a superconducting interference device (SQUID) system. To measure the I-MCG and MCG signals, four first-order gradiometers with an 18-mm diameter and a 50-mm baseline were used. The SQUIDs are driven by a flux-locked-loop circuit with a frequency range higher than that of an ac-current (40 kHz) with constant amplitude passed through a subject. The output of the circuit is filtered through two circuits: one for measuring the I-MCG signals and one for measuring the MCG signals. The I-MCG signals are obtained by demodulating the magnetic field, which is detected by the gradiometers, at the frequency of the ac current. As a result, the I-MCG signal reflects the change in spatial distribution of conductivity caused by the movement of the heart muscle and blood volume. A contour map of the 2-D I-MCG signals showed the largest signals occur above the right ventricle and right atrium. In a corresponding current-arrow map, it was found that the large current arrows occurred above the right side of the right ventricle. Furthermore, it was found that the systole and diastole timings obtained from the first-derivative I-MCG signal and the phonocardiogram were different. These results show that primitive 2-D I-MCG signal can provide much physiological information on the circulatory movement of the heart.

Original languageEnglish
Pages (from-to)721-728
Number of pages8
JournalIEEE Transactions on Biomedical Engineering
Volume49
Issue number7
DOIs
Publication statusPublished - Jun 27 2002
Externally publishedYes

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Keywords

  • I-MCG
  • Impedance-magnetocardiogram
  • MCG
  • Magnetocardiogram
  • SQUID

ASJC Scopus subject areas

  • Biomedical Engineering

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