Summary
The electric conductivities of different tissues are important parameters of the head model and their precise knowledge appears to be a prerequisite for the localization of electric sources within the brain. To estimate the error in source localization due to errors in assumed conductivity values, parameter variations on skull conductivities are examined. The skull conductivity was varied in a wide range and, in a second part of this paper, the effect of a nonhomogeneous skull conductivity was examined. An error in conductivity of lower than 20% appears to be acceptable for fine finite element head models with average discretization errors down to 3mm. Nonhomogeneous skull conductivities, e.g., sutures, yield important mislocalizations especially in the vincinty of electrodes and should be modeled.
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References
Ary, J.P., Klein, S.K. and Fender, D.H. Location of Sources of Evoked Scalp Potentials: Corrections for Skull and Scalp Thicknesses. IEEE Trans. Biomed. Engng., 1981, 28: 447–452.
Bertrand, O., Thevenet, M. and Perrin, F. 3D finite elemente method in brain elecrtical activity studies. In: J. Nenonen, H.-M. Rajala and T. Katila (Eds.), Biomagnetic localization and 3D modelling. Report Dep. of Technical Physics, Helsinki University, 1991, 154–171.
Buchner, H., Knoll, G., Fuchs, M., RienÄcker, A., Beckmann, R., Wagner, M., Silny, J., and Pesch, J. Inverse Location of electric current sources in finite element models of the human head. Electrenceph. clin. Neurophysiol, 1997 (in press).
Fuchs, M., Wagner, M., Wischmann, H.-A., Ottenberg, K. and Dössel, O. Possibilities of functionsal brain imaging using combination of MEG and MRT. In: C. Pantev (Ed.), Oscillatory event-relared brain dynamics, Plenum Press, New York, 1994, 435–457.
Geddes, L. A. and Baker, L.E. The Specific Resistance of Biological Material — A Compendium of Data for the Biomedical Engineer and Physiologist. Med. & Biol. Engng., 1967, 5: 271–293.
Ilmoniemi, R.J. Magnetic Source Imaging. In: Carpenter D. O. and Ayrapetyan, S. (Eds.), Biological Effects of Electric and Magnetic Fields. Academic Press San Diego, 1994, 2: 49–79.
Law, S. Thickness and resistivity variations over the upper surface of the human skull. Brain Topography, 1993, 6: 99–109.
Lütkenhöner, B., Menninghaus, E., Steinstrater, O., Wienbruch, G., Gissler, H. M. and Elbert, T. Neuromagnetic source analysis using magnetic resonance images for the construction of source and volume conductor model, Brain Topography, 1995, 7: 291–299.
Meijs, J.W.H., Peters, M.J. and Oosterom, A. van. Computation of MEG's and EEG's using a realistically shaped multicompartment model of the head. Med. biol. Engng. Comput, 1985, 23 (Suppl. Part 1): 36–37.
Menninghaus, E., Lütkenhöhner, B. and Gonzalez, S.L. Localization of a dipolar source in a skull phantom: relistic versus spherical model. IEEE Biomed. Eng., 1994, 41: 986–989.
Nunez, P.L. Localization of brain activity with electroencephalography. In: S. Sato (Ed.), Magnetoencephalography. Raven Press, New York, 1990, 39–65.
Peters, M. and Wieringa, H. The influence of the volume conductor on electric source estimation. Brain Topography, 1993, 5: 337–345.
Peters, M.J. Realistically shaped volume conductor models of the head. Brain Topography, 1994, 7: 328–329.
Roth, B., Balish, M., Gorbach, A. and Sato, S. How well does a three-sphere model predict positions of dipoles in a realisticaly shaped head? Electroenceph. clin. Neurophysiol., 1993, 175–184.
Srebro, R. Realistic modeling of VEP topography. Vision Res, 1990, 30: 1001–1009.
Stok, C. J., The Influence of Model Parameters on EEG/MEG Single Dipole Source Estimation. IEEE Trans. Biomed. Engng., 1987, 34: 289–296.
Wagner, M., Fuchs, M., Wischmann, H.A. and Drenckhahn, R. Representation of individual anatomy by triangle nets for current reconstruction, volume conductor modelling and visualization. In: H.J. Heinze, T.F. Mühle, G.R. Maugum and H. Schleich (Eds) Mapping cognition in time and space. BirkhÄuser, Boston, 1996, in press.
Wagner, M., Fuchs, M., Wischmann, H.A., Ottenberg, K. and Dössel, O. Cortex segmentation from 3D MR images for MEG reconstructions. In: C. Baumgartner, L. Deecke, G. Stroink and S.J. Williamson (Eds) Biomagnetism: Fundamental research and clinical applications. IOS Press, Amsterdam, 1995, 433–438.
Yan, Y., Nunez, P.L. and Hart, R.T. Finite-element model of the human head: scalp potentials due to dipole sources. Med Biol Eng Comput, 1991, 29: 475–481.
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The authors wish to thank the VW — Foundation for financial support.
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Pohlmeier, R., Buchner, H., Knoll, G. et al. The influence of skull-conductivity misspecification on inverse source localization in realistically shaped finite element head models. Brain Topogr 9, 157–162 (1997). https://doi.org/10.1007/BF01190384
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DOI: https://doi.org/10.1007/BF01190384