Interpretation of EEG (electroencephalography) or MEG (magnetoencephalography) derived three-dimensional dipole localizations is hampered by poor visualization. This paper describes a method for combining dipole data with structural image data of the same patient. To ensure high precision this method utilizes external markers that are easy to apply. These markers can achieve subslice accuracy and can even be used to pinpoint reference points outside the scanned volume. Accurate matching is thus provided even in standard imaging protocols employing thick slices and/or large interslice gaps. The results of the matching method are presented in 2D and 3D visualizations. The hybrid images facilitate the interpretation of dipole localizations with respect to the patient's anatomy.
Key words CT - Dipole - EEG - Epilepsy - Multimodality Matching - MEG - MRI - Volume Visualization
This research was supported in part by the Dutch ministry of Economic Affairs through a SPIN grant, and by the industrial companies Hewlett-Packard, Agfa-Gevaert, Philips Medical Systems, KEMA, and Tektronix. The authors are grateful to Linda Meiners, University Hospital Utrecht, for her contribution in defining a suitable MRI protocol, and want to thank Berry Robben, Duke University, Durham, and Evert-Jan Pol, Philips Research Laboratories, Eindhoven, for their critical comments on earlier versions of the manuscript.