Detection and modeling of the cardiac magnetic field using high-T c SQUID gradiometers

Hong-Chang Yang, Shou Yen Hung, Shu-Hsien Liao, Shi Jun Hsu, Shu Yun Wang, Ji Cheng Chen, Ming Jye Chen, Chiu Hsien Wu, Herng-Er Horng, Shieh-Yueh Yang, J. T. Jeng

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Abstract

Single channel MCG systems were used to probe the magnetic field signal from the heart activity in an unshielded or magnetically moderate shielded environment. Using the FFT of magnetometers with the Hanning window overlapped, we optimized the parameters required for the subtraction circuit to minimize the environmental noises in the frequency ranges of interest. Using the optimized parameters, low pass and notch filters, we reduced the environmental noise level much lower than the signal of the heart activity. Hence, we can perform MCG measurements in a magnetically unshielded environment or moderate shielded environment. It was found that a signal to noise ratio of 17 for four-vector gradiometer and 8 for 1st order gradiometer were achieved in a moderate shielded environment. The four-vector gradiometer further improve the two times the sensitivity inside the moderate shielded room compared with that of the 1st order gradiometer. To solve the inverse problem we simulated the magnetic field data with the current-dipoles model and obtained the optimized moving orbits of current dipoles. The current density mapping of the circulating current was derived. A comparison between the measured data and simulated results is given.

Original languageEnglish
Pages (from-to)508-519
Number of pages12
JournalChinese Journal of Physics
Volume42
Issue number4 II
Publication statusPublished - 2004 Aug 1

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ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Yang, H-C., Hung, S. Y., Liao, S-H., Hsu, S. J., Wang, S. Y., Chen, J. C., Chen, M. J., Wu, C. H., Horng, H-E., Yang, S-Y., & Jeng, J. T. (2004). Detection and modeling of the cardiac magnetic field using high-T c SQUID gradiometers. Chinese Journal of Physics, 42(4 II), 508-519.