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Multichannel magnetocardiographic measurements with a physical thorax phantom

  • K. Pesola
  • U. Tenner
  • J. Nenonen
  • P. Endt
  • H. Brauer
  • U. Leder
  • T. Katila
Biomagnetism

Abstract

Artificial dipolar sources were applied inside a physical thorax phantom to experimentally investigate the accuracy obtainable for non-invasive magnetocardiographic equivalent current dipole localisation. For the measurements, the phantom was filled with saline solution of electrical conductivity 0.21 Sm−1. A multichannel cardiomagnetometer was employed to record the magnetic fields generated by seven dipolar sources at distances from 25 mm to 145 mm below the surface of the phantom. The inverse problem was solved using an equivalent current dipole in a homogeneous boundary element torso model. The dipole parameters were determined with a non-linear least squares fitting algorithm. The signal-to-noise ratio (SNR) and the goodness of fit of the calculated localisations were used in assessing the quality of the results. The dependence between the SNR and the goodness of fit was derived, and the results were found to correspond to the model. With SNR between 5 and 10, the average localisation error was found to be 9±8 mm, while for SNR between 30 and 40 and goodness of fit between 99.5% and 100%, the average error reduced to 3.2±0.3 mm. The SNR values obtained in this study were also compared with typical clinical values of SNR.

Keywords

Magnetocardiography Phantom measurement Boundary element method Equivalent current dipole localisation 

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References

  1. Brauer, H., Tenner, U., Arlt, A., andWiechmann, H. (1996a): ‘Validation of biomagnetic source localization techniques using physical thorax phantoms’,Med. Biol. Eng. Comput.,34 (Suppl. 1), pp. 55–56Google Scholar
  2. Brauer, H., Tenner, U., Wiechmann, H., Arlt, A., Leder, U., Haueisen, J., Nowak, H., Trahms, L., andBurghoff, M. (1995b): ‘Modellierung eines Thoraxphantoms für die Validierung der biomagnetischen Quellenlokalisation’,Biomedizinische Technik,41 (Suppl. 1), pp. 294–295Google Scholar
  3. Fenici, R., andMelillo, G. (1993): ‘Magnetocardiography: ventricular arrhythmias’,Eur. Heart J.,14 (Suppl. E), pp. 53–60Google Scholar
  4. Fenici, R., Pesola, K., Korhonen, P., Mäkijärvi, M., Nenonen, J., Toivonen, L., Fenici, P., andKatila, T. (1988): ‘Magnetocardiographic pacemapping for non-fluoroscopic localization of intracardiac electrophysiology catheters’, to be published in the November Cardiostim Supplement of PACEGoogle Scholar
  5. Geddes, L. A., andBaker, L. E. (1967): ‘The specific resistance of biological material-a compendium of data for the biomedical engineer and physiologist’,Med. Biol. Eng.,5, pp. 271–293CrossRefGoogle Scholar
  6. Haueisen, J., Boettner, A., Funke, M., Brauer, H., andNowak, H. (1997): ‘The influence of boundary element discretization on the forward and inverse problem in electroencephalography and magnetoencephalography’,Biomedizinische Technik,42, pp. 240–248CrossRefGoogle Scholar
  7. Hren, R., Zhang, X., andStroink, G. (1996): ‘Comparison between electrocardiographic and magnetocardiographic inverse solutions using the boundary element method’,Med. Biol. Eng. Comput.,34, pp. 110–114CrossRefGoogle Scholar
  8. Hren, R., Stroink, G., andHoracek, B. M. (1998): ‘Accuracy of a single-dipole inverse solution when localising ventricular preexcitation sites: simulation study’,Med. Biol. Eng. Comp. 36, pp. 323–329CrossRefGoogle Scholar
  9. Hren, R., Stroink, G., andHoracek, B. M. (1998): ‘Accuracy of a single-dipole inverse solution when localising ventricular preexcitation sites: simulation study’,Med. Biol. Eng. Comp.,36, pp. 323–329CrossRefGoogle Scholar
  10. Mäkijärvi, M., Nenonen, J., Toivonen, L., Montonen, J., Katila, T., andSiltanen, P. (1993): ‘Magnetocardiography: supraventricular arrhythmias and preexcitation syndrome’,Eur. Heart J.,14 (Suppl. E), pp. 46–52Google Scholar
  11. Marquardt, D. (1963): ‘An algorithm for least-squares estimation of nonlinear parameters’,J. Soc. Indust. Appl. Math.,11, pp. 431–441MATHCrossRefMathSciNetGoogle Scholar
  12. Montonen, J., Ahonen, A., Hämäläinen, M., Ilmoniemi, R., Laine, P., Nenonen, J., Paavola, M., Simelius, K., Simola, J., andKatila, T. (1998): ‘Magnetocardiographic functional imaging studies in BioMag Laboratory’,in Aine, C., Okada, Y., Stroink, G., Swithenby, S., andWood, C. (Eds.), ‘Advances in biomagnetism research: BioMag96 (Springer Verlag, New York, in press)Google Scholar
  13. Moshage, W., Achenbach, S., Göhl, K., andBachmann, K. (1996): ‘Evaluation of the non-invasive localization accuracy of cardiac arrhythmias attainable by multichannel magnetocardiography (MCG)’,Int. J. Card. Imaging,12, pp. 47–59CrossRefGoogle Scholar
  14. Nenonen, J. (1994): ‘Solving the inverse problem in magnetocardiography’,IEEE Eng. Med. Biol. Mag.,13, pp. 487–496CrossRefGoogle Scholar
  15. Nenonen, J., Mäkijärvi, M., Toivonen, L., Forsman, K., Leiniö, M., Montonen, J., Järvinen, A., Keto, P., Hekali, P., andKatila, T. (1993): ‘Non-invasive magnetocardiographic localization of ventricular pre-excitation in the Wolff-Parkinson-White syndrome using a realistic torso model’,Eur. Heart J.,14, pp. 168–174Google Scholar
  16. Nenonen, J., Purcell, C., Horacek, B. M., Stroink, G., andKatila, T. (1991): ‘Magnetocardiographic functional localization using a current dipole in a realistic torso’,IEEE Trans. Biomed. Eng.,38, pp. 658–664CrossRefGoogle Scholar
  17. Numminen, J., Ahlfors, S., Ilmoniemi, R., Montonen, J., andNenonen, J. (1995): ‘Transformation of multichannel magnetocardiographic signals to standard grid form’,IEEE Trans. Biomed. Eng.,42, pp. 72–78CrossRefGoogle Scholar
  18. Oeff, M., andBurghoff, M. (1994): ‘Magnetocardiographic localization of the origin of ventricular ectopic beats’,Pacing Clin. Electrophysiol.,17, pp. 517–522CrossRefGoogle Scholar
  19. Siltanen, P. (1988): ‘Magnetocardiography’,in MacFarlane, P. W., andLawrie, T. D. W. (Eds): ‘Comprehensive electrocardiology’ (Pergamon Press, London), pp. 1405–1434Google Scholar
  20. Stroink, G., Lamothe, R., andGardner, M. J. (1996): ‘Magnetocardiographic and electrocardiographic mapping studies’,in Weinstock, H. (Ed.): ‘SQUID sensors: fundamentals, fabrication and applications’ (NATO ASI Series, Kluwer, The Netherlands), pp. 413–444Google Scholar
  21. Tenner, U., Brauer, H., Wiechmann, H., Arlt, A., Haueisen, J., Nowak, H., andLeder, U. (1996): ‘reconstruction of dipolar and extended biomagnetic sources in a physical thorax phantom’,in Proc. XVIII Annual Int. Conf. IEEE Eng. Med. Biol. Soc., Amsterdam, The Netherlands, CD-rom, Paper number: 907Google Scholar
  22. Tenner, U., Brauer, H., Haueisen, J., Nowak, H., Nenonen, J., andKatila, T. (1997): ‘Multichannel magnetocardiographic and body surface potential mapping with a physical thorax phantom’,Med. Biol. Eng. Comput.,35, (Suppl. Part I), p. 17Google Scholar
  23. Weissmüller, P., Abraham-Fuchs, K., Schneider, S., Richter, P., Kochs, M., andHombach, V. (1992): ‘Magnetocardiographic non-invasive localization of accessory pathways in the Wolff-Parkinson-White syndrome by a multichannel system’,Eur. Heart J.,13, pp. 616–622Google Scholar
  24. Ziolkowski, M., andBrauer, H. (1996): ‘Methods of mesh generation for biomagnetic problems’,IEEE Trans. Magn.,32, pp. 1345–1348CrossRefGoogle Scholar

Copyright information

© IFMBE 1999

Authors and Affiliations

  • K. Pesola
    • 1
    • 2
  • U. Tenner
    • 3
  • J. Nenonen
    • 1
    • 2
  • P. Endt
    • 1
    • 4
  • H. Brauer
    • 3
  • U. Leder
    • 5
  • T. Katila
    • 1
    • 2
  1. 1.Laboratory of Biomedical EngineeringHelsinki University of TechnologyHUTFinland
  2. 2.Medical Engineering Centre, Biomag LaboratoryHelsinki University Central HospitalHelsinkiFinland
  3. 3.Department of Electrical EngineeringTechnical University of IlmenauIlmenauGermany
  4. 4.Physikalisch-Technische-BundesanstaltBerlinGermany
  5. 5.Clinic of Internal Medicine IllFriedrich-Schiller-University of JenaJenaGermany

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