Summary
Probabilistic modelling of continuous current sources is applied to the analysis of MEG signals generated by current dipoles implanted in the head of a living human subject. Estimates of the distribution of activity within a circular disk are obtained from signals generated by a single implanted dipole and by a pair of simultaneously active implanted dipoles. The orientation and depth of the disc is determined in advance from the experimental geometry and the measurements. The resulting reconstructions constitute the first in vivo validation of distributed source imaging; they provide a complementary test to earlier works using computer generated data and tests using point source analysis of signals generated by a single implanted dipole. In this work we provide a literal test of spatial resolution by resolving two nearby point-like sources. Temporal resolution is addressed in a de facto manner by imaging at one millisecond intervals. Computer simulations, with controlled amount of noise, are used to demonstrate the robustness of the results, and show the interplay between high spatial accuracy and noise insensitivity.
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Balish, M. and Sato, S. Magnetoencephalography in epilepsy research and its perspectives. In: S.J. Williamson, M. Hoke, G. Stroink and M. Kotani (Eds.), Advances in Biomagnetism. Plenum Press, New York, 1989: 269–272.
Balish, M., Sato, S., Connaughton, P. and Kufta, C. Magnetoencephalographic (MEG) localization of multiple subdural electrodes. Neurology, 1991, 41: 1072–1076.
Baumgartner, C. and Deecke, L. Magnetoencephalography in clinical epileptology and epilepsy research. Brain Topogr., 1990, 2: 203–219.
Clarke, C.J.S. and Janday, B.S. Probabilistic methods in a biomagnetic inverse problem. Inverse Problems, 1989, 5: 483–500.
Clarke, C.J.S. Probabilistic methods in a biomagnetic inverse problem. Inverse Problems, 1989, 5: 999–1012.
Clarke, C.J.S., Ioannides, A.A. and Bolton, J.P.R. Localised and distributed source solutions for the biomagnetic inverse problem I. In: S.J. Williamson, M. Hoke, G. Stroink and M. Kotani (Eds.), Advances in Biomagnetism. Plenum Press, New York, 1989: 587–590.
Crowley, C.W., Greenblatt, R.E. and Khalil, I. Minimum norm estimation of current distributions in realistic geometries. In: S.J. Williamson, M. Hoke, G. Stroink and M. Kotani (Eds.), Advances in Biomagnetism. Plenum Press, New York, 1989: 603–606.
Hämäläinen, M.S. and Ilmoniemi, R.J. Interpreting Measured Magnetic Fields of the Brain: Estimates of the Current Distributions. Preprint TKK-F-A559, Helsinki University of Technology, 1984.
Hoke, M., Lehnertz, K., Lutkenhoner, B. and Pantev, C. Cortical auditory evoked magnetic fields: mapping of time and frequency domain aspects. In: K. Mauer (Ed.), Topographic Brain Mapping of EEG and Evoked Potentials. Springer-Verlag, Berlin, 1989: 537–564.
Ioannides, A.A. Comparison of MEG with other functional Imaging Techniques, Clinical Physics and Physiological Measurement Suppl., 1991, A-12, 23–28.
Ioannides, A.A., Bolton, J.P.R., Hasson, R. and Clarke, C.J.S. Localised and distributed source solutions for the biomagnetic inverse problem II. In: S.J. Williamson, M. Hoke, G. Stroink and M. Kotani (Eds.), Advances in Biomagnetism. Plenum Press, New York, 1989a: 591–594.
Ioannides, A.A., Hasson, R. and Bolton, J.P.R. Spatial and Temporal Evolution of Brain Activity. Open University video, July 1989b.
Ioannides, A.A., Bolton, J.P.R. and Clarke, C.J.S. Continuous probabilistic solutions to the biomagnetic inverse problem. Inverse Problems, 1990a, 6: 523–542.
Ioannides, A.A., Hasson, R. and Miseldine, J.G. Model- dependent noise elimination and distributed source solutions for the biomagnetic inverse problem. In: A.F. Gmitro, P.S. Idell and I.J. Lahaie (Eds.), Digital Image Synthesis and Inverse Optics., Proc. SPIE 1351, 1990b: 471–481.
Ioannides, A.A., Singh K.D., Hasson R., Baumann S.B., Rogers R.L., Papanicolaou, A.C., Rogers, R.L., Guinto, F.C. and Papanicolaou, A.C. Comparison of Current Dipole and Magnetic Field Tomography Analyses of the Cortical Response to Auditory Stimuli. Brain Topography 1993 (In press).
Kullman, W.H., Jandt, K.D., Rehm, K., Schlitt, H.A., Dallas, W.J. and Smith, W.E. A linear estimation approach to biomagnetic imaging. In: S.J. Williamson, M. Hoke, G. Stroink and M. Kotani (Eds.), Advances in Biomagnetism. Plenum Press, New York, 1989: 571–574.
Mosher, J.C., Lewis, P.S., Leahy, R., and Singh, M. Multiple Dipole Modelling of Spatio-Temporal MEG Data. In: A.F. Gmitro, P.S. Idell and I.J. Lahaie (Eds.), Digital Image Synthesis and Inverse Optics. Proc SPIE 1351, 1990: 471–475.
Pantev, C., Hoke, M., Lutkenhoner, B. and Lehnertz, K. Tonotopic organisation of the auditory cortex: pitch versus frequency representation. Science, 1986, 244: 486–488.
Papanicolaou, A.C., Baumann, S., Rogers, R.L., Saydjari, C., Amparo, E.G. and Eisenberg, H.M. Localization of auditory response sources using magnetoencephalography and magnetic resonance imaging. Arch. Neurol., 1990, 47: 33–37.
Ribary, U., Ioannides, A.A., Hasson, R., Singh, K.D., Bolton, J.P.R., Lado, F. and Llinas, R. Magnetic Field Tomography (MFT) of Coherent Thalamo-Cortical 40 Hz Oscillations in Humans, Proc. Nat. Acad. Sci. USA, 1991, 88, 11037–11041.
Rose, D.F., Sato, S., Smith, P.D., Friauf, W. and Ducla- Soares, E. Subdural electrode as a dipole source for magnetoencephalography. Electroenceph. Clin. Neurophysiol., 1989a, 72: 86–90.
Rose, D.F., Ducla-Soares, E., Sato, S., Kufta, C.V. MEG localization of a subdural dipole in a patient. Epilepsia, 1989b, 29: 656–657.
Scherg and Cramon D. von, Two bilateral sources of the late AEP as identified by a spatio-temporal dipole model. Electroenceph. Clin. Neurophysiol. 1985, 62: 32–44.
Scherg, M., Vajsar, J. and Picton, T.W. A source analysis of the late human auditory evoked potentials. J. Cognitive Neuroscience, 1989, 1: 336–355.
Scherg M. Fundamentals of Dipole Source Potential Analysis. In: Auditory Evoked Magnetic Fields and Electric Potentials ed. Grandori, F., Romani, G.L. (Eds), Karger, Basel, 1990, 40–69.
Schmidt R.O. Multiple emitter location and signal parameter estimation. IEEE Trans. Antennas and Propagation, 1986, AP-34: 276–280.
Smith, D.B., Sidman, R.D., Henke, J.S., Flanigin, H., Labiner, D. and Evans, C.N. Scalp and depth recording of induced deep cerebral potentials. Electroenceph. Clin. Neurophysiol., 1983, 55: 145–150.
Smith, D.B., Sidman, R.D., Flanigin, H., Henke, J. and Labiner, D. A reliable method for localizing deep intracranial sources of the EEG. Neurology, 1985, 35: 1702–1707.
Tepley, N., Barkley, G.L., Moran, J.E., Simkins, R.T. and Welch, K.M.A. Observation of spreading cortical depression in migraine patients. In: S.J. Williamson, M. Hoke, G. Stroink and M. Kotani (Eds.), Advances in Biomagnetism. Plenum Press, New York, 1989: 327–330.
Tripp, J.H. Physical Concepts and Mathematical Models. In Biomagnetism: an Interdisciplinary Approach, ed. Williamson, S.J., Romani, G.L., Kaufman, L. and Modena, I., Plenum Press, New York, 1983, 123–139.
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This work was done in part while Robert Muratore held a National Research Council/National Institutes of Health Research Associateship. This work has benefited from research grants from the Science and Engineering Research Council (UK), including an award under the Computational Science initiative. Travel assistance to one of us (AAI) from the Nuffield foundation is also acknowledged.
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Ioannides, A.A., Muratore, R., Balish, M. et al. In vivo validation of distributed source solutions for the biomagnetic inverse problem. Brain Topogr 5, 263–273 (1993). https://doi.org/10.1007/BF01128993
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DOI: https://doi.org/10.1007/BF01128993