Abstracts

Substantial interest exists in the development of noninvasive localization of epileptogenic foci, since the current standard utilization of subdural electrocorticography and depth electrodes requires surgical implantation with some additional risks to the patient. The aim of the present study is to evaluate a novel noninvasive source localization approach for localizing epileptogenic foci from scalp EEG. The traditional dipole source localization approach faces problems for multiple dipole source localization as the number of sources increases. We recently developed a new subspace source localization approach, i.e. three-dimensional [underline]fi[/underline]rst pri[underline]n[/underline]ciple v[underline]e[/underline]ctors (3D-FINE), for EEG-based epileptic focus localization (Xu et al, Phys Med [amp] Bio, 49(2):327[ndash]343, 2004). The approach uses a three-dimensional search instead of solving the extremely complicated nonlinear optimization problem. It employs the projection onto a particular set of vectors in noise-only subspace instead of entire noise-only subspace to achieve high accuracy and high spatial resolvability. Computer simulation studies were conducted to test the feasibility and performance of 3D-FINE.Three patients, from the Mayo Clinic, with medically intractable partial epilepsy and symptomatic lesion demonstrated by the magnetic resonance image (MRI) were analyzed by 3D-FINE using interictal data. The patient[apos]s EEGs were recorded using 31 electrodes in the modified 10/20 system and each patient had a standardized seizure protocol MRI. The interictal data was identified and selected by the experienced neurologists. The results from the 3D-FINE approach were evaluated and validated by the brain lesions demonstrated on the MRI. Both computer simulations and interictal data analysis indicate the higher spatial resolution and higher source localization accuracy of 3D-FINE in multiple source localization in comparison with the well established MUSIC approach, which suggests that 3D-FINE has the greater ability to distinguish closely-spaced sources. The identified sources from both MUSIC and 3D-FINE are well correlated with the MRI lesions. They appear on the border or in the vicinity of the MRI lesion. The detailed electrical activity distributions during the interictal spikes are revealed by 3D-FINE suggesting the excellent performance of 3D-FINE in localizing epileptiform activities from scalp EEG. We tested the feasibility of imaging epileptic foci using a novel multiple dipole source localization approach, i.e. 3D-FINE. The patients studied are with MRI lesions because it provides a unique way to cross validate the epileptic foci localization results using different imaging modalities. However, the usefulness of such technique is to image epileptic foci in epilepsy patient without explicit MRI lesions, where MRI technique may fail to identify the epileptic foci. (Supported by NIH EB 00178 and NSF BES-0411898.)