This work was performed as part of a larger research concerning the feasibility of improving the localization of epileptic foci, as compared to the standard SPECT examination, by applying the technique of EEG mapping. The presented study extends our previous work on the development of a method for superposition of SPECT images and EEG 3D maps when these two examinations are performed simultaneously. Due to the lack of anatomical data in SPECT images it is a much more difficult task than in the case of MRI/EEG study where electrodes are visible in morphological images. Using the appropriate dose of radioisotope we mark five base electrodes to make them visible in the SPECT image and then approximate the coordinates of the remaining electrodes using properties of the 10-20 electrode placement system and the proposed nine-ellipses model. This allows computing a sequence of 3D EEG maps spanning on all electrodes. It happens, however, that not all five base electrodes can be reliably identified in SPECT data. The aim of the current study was to develop a method for determining the coordinates of base electrode(s) missing in the SPECT image. The algorithm for coordinates approximation has been developed and was tested on data collected for three subjects with all visible electrodes. To increase the accuracy of the approximation we used head surface models. Freely available model from Oostenveld research based on data from SPM package and our own model based on data from our EEG/SPECT studies were used. For data collected in four cases with one electrode not visible we compared the invisible base electrode coordinates approximation for Oostenveld and our models. The results vary depending on the missing electrode placement, but application of the realistic head model significantly increases the accuracy of the approximation.
If the inline PDF is not rendering correctly, you can download the PDF file here.
 McNally K.A. Paige A.L. Varghese G. Zhang H. Novotny E.J. Spencer S.S. Zubal G. Blumenfeld H. (2005). Localizing value of ictal-interictal SPECT analyzed by SPM (ISAS). Epilepsia 46 1450-1464.
 O’Brien T.J. So E.L. Mullan B.P. Hauser M.F. Brinkmann B.H. Bohnen N.I. Hanson D. Cascino G.D. Jack C.R. Jr Sharbrough F.W. (1998). Subtraction ictal SPECT coregistered to MRI improves clinical usefulness of SPECT in localizing the surgical seizure focus. Neurology 50 445-454.
 Kowalczyk L. Bajera A. Goszczynska H. Zalewska E. Krolicki L. (2013). Superposition of 3D EEG maps on SPECT images acquired from simultaneous examinations. Biocybernetics and Biomedical Engineering 33 196-203.
 Goszczyńska H. Królicki L. Bajera A. Zalewska E. Kowalczyk L. Walerjan P. Rysz A. Kolebska K. (2007). The procedure for SPECT and BEAM images adjustment. Polish Journal of Medical Physics and Engineering 13 115-125.
 Jasper H.H. (1958). The ten-twenty electrode system of the International Federation. Electroencephalography and Clinical Neurophysiology 10 371-375.
 Papademetris X. Jackowski M. Rajeevan N. Constable R.T. Staib L.H. BioImageSuite: An integrated medical image analysis suite. Section of Bioimaging Sciences Dept. of Diagnostic Radiology Yale School of Medicine. http://www.bioimagesuite.org
 Koessler L. Cecchin T. Caspary O. Benhadid A. Vespignani H. Maillard L. (2011). EEG-MRI coregistration and sensor labeling using a 3D laser scanner. Annals of Biomedical Engineering 39 983-995.
 Koessler L. Maillard L. Benhadid A. Vignal J.P. Braun M. Vespignani H. (2007). Spatial localisation of EEG electrodes. Clinical Neurophysiology 37 97-102.
 Oostenveld R. Praamstra P. (2001). The five percent electrode system for high-resolution EEG and ERP measurements. Clinical Neurophysiology 112 713-719.
 Oostenveld R. Praamstra P. Stegeman D.F. van Oosterom A. (2001). Overlap of attention and movement-related activity in lateralized event-related brain potentials. Clinical Neurophysiology 112 477-484.
 de Munck J.C. van Houdt P.J. Verdaasdonk R.M. Ossenblok P.W. (2012). A semi-automatic method to determine electrode positions and labels from gel artifacts in EEG/fMRI-studies. Neuroimage 59 399-403.
 Rademacher J. Caviness V.S. Jr Steinmetz H. Galaburda A.M. (1993). Topographical variation of the human primary cortices: Implications for neuroimaging brain mapping and neurobiology. Cerebral Cortex 3 (4) 313-329.
 Scheinost D. Teisseyre T.Z. Distasio M. DeSalvo M.N. Papademetris X. Blumenfeld H. (2010). New open-source ictal SPECT analysis method implemented in BioImage Suite. Epilepsia 51 703-707.