Channel Capacity of Multichannel Magnetometers

  • P. K. Kemppainen
  • R. J. Ilmoniemi

Abstract

We have applied Shannon’s theory of communication to develop a figure of merit for the comparison and optimization of multichannel magnetometers. This new measure is the channel capacity of the equipment in conveying information about cerebral currents. Like other figures of merit (Abraham-Fuchs et al., 1988; Carelli and Leoni, 1986; Erné 1985; Knuutila and Hämäläinen, 1989), it is a function of the SQUID noise level, the coil configuration, and the distance of the sensor array from the brain. Channel capacity as a cost function enables us to compare the marginal utility of different parameters, for example, of additional channels or a reduced brain-sensor distance, without specific source models.

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References

  1. Abrahams-Fuchs, K., Schneider, S., Reichenberger, H., 1988, MCG inverse solution: Influence of coil size, grid size, number of coils, and SNR. IEEE Trans. Biom. Eng., 35: 573.CrossRefGoogle Scholar
  2. Carelli, P., Leoni, R., 1986, Localization of biological sources with arrays of superconducting gradiometers, J. Appl. Phys. 59: 645.CrossRefGoogle Scholar
  3. Erné, S.N., 1985, SQUID measurement techniques in medical diagnosis, in ”SQUID’85, Superconducting Quantum Interference Devices and their Applications”, H.D. Hahlbohm, H. Lübbig, eds., Walter de Gruyter, Berlin.Google Scholar
  4. Gudden, F., Hoenig, E., Reichenberger, H., Schittenhelm, R., Schneider, S., 1989, A multi-channel system for use in biomagnetic diagnosis in neurology and cardiology: principle, method and initial results, Electromedica, 57: 2.Google Scholar
  5. Kajola, M., Ahlfors, S., Ehnholm, G.J., Hallstrom, J., Hämäläinen, M.S., Ilmoniemi, R.J., Kiviranta, M., Knuutila, J., Lounasmaa, O.V., Tesche, C.D., Vilkman, V., 1989, A 24-channel magnetometer for brain research, this volume.Google Scholar
  6. Knuutila, J., Ahlfors, S., Ahonen, A., Hallstrom, J., Kajola, M., Lounasmaa, O.V., Vilkman, V., Tesche, C., 1987, A large-area low-noise seven-channel magnetometer for brain research, Rev. Sci. Instrum., 58: 2145.CrossRefGoogle Scholar
  7. Knuutila, J., Hämäläinen, M.S., 1989, On the spatial locating accuracy of multichannel magnetometers, this volume.Google Scholar
  8. Plonsey, R., 1969, “Bioelectric Phenomena”, McGraw-Hill, New York.Google Scholar
  9. Shannon, C.E., Weaver, W., 1949, “The Mathematical Theory of Communication”, The University of Illinois Press, Urbana.Google Scholar

Copyright information

© Plenum Press, New York 1989

Authors and Affiliations

  • P. K. Kemppainen
    • 1
  • R. J. Ilmoniemi
    • 1
  1. 1.Low Temperature LaboratoryHelsinki University of TechnologyEspooFinland

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